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Sample records for biocatalytic alkene oxidation

  1. Towards preparative-scale, biocatalytic alkene reductions.

    PubMed

    Bougioukou, Despina J; Walton, Adam Z; Stewart, Jon D

    2010-12-01

    Simple strategies for using alkene reductase enzymes to produce gram-scale quantities of both (R)- and (S)-citronellal have been developed. The methodology is easily accessible to non-specialist laboratories, allowing alkene reductases to be added to the toolbox of routine synthetic transformations.

  2. Techno-economic analysis of biocatalytic processes for production of alkene epoxides.

    PubMed

    Borole, Abhijeet P; Davison, Brian H

    2007-04-01

    A techno-economic analysis of two different bioprocesses was conducted, one for the conversion of propylene to propylene oxide (PO) and other for conversion of styrene to styrene epoxide (SO). The first process was a lipase-mediated chemo-enzymatic reaction, whereas the second one was a one-step enzymatic process using chloroperoxidase. The PO produced through the chemo-enzymatic process is a racemic product, whereas the latter process (based on chloroperoxidase) produces an enantio-pure product. The former process thus falls under the category of high-volume commodity chemical (PO); whereas the latter is a low-volume, high-value product (SO).A simulation of the process was conducted using the bioprocess engineering software SuperPro Designer v6.0 (Intelligen, Inc., Scotch Plains, NJ) to determine the economic feasibility of the process. The purpose of the exercise was to compare biocatalytic processes with existing chemical processes for production of alkene expoxides. The results show that further improvements are needed in improving biocatalyst stability to make these bioprocesses competitive with chemical processes. PMID:18478407

  3. Alkene Cleavage Catalysed by Heme and Nonheme Enzymes: Reaction Mechanisms and Biocatalytic Applications

    PubMed Central

    Mutti, Francesco G.

    2012-01-01

    The oxidative cleavage of alkenes is classically performed by chemical methods, although they display several drawbacks. Ozonolysis requires harsh conditions (−78°C, for a safe process) and reducing reagents in a molar amount, whereas the use of poisonous heavy metals such as Cr, Os, or Ru as catalysts is additionally plagued by low yield and selectivity. Conversely, heme and nonheme enzymes can catalyse the oxidative alkene cleavage at ambient temperature and atmospheric pressure in an aqueous buffer, showing excellent chemo- and regioselectivities in certain cases. This paper focuses on the alkene cleavage catalysed by iron cofactor-dependent enzymes encompassing the reaction mechanisms (in case where it is known) and the application of these enzymes in biocatalysis. PMID:22811656

  4. Engineering of TM1459 from Thermotoga maritima for Increased Oxidative Alkene Cleavage Activity

    PubMed Central

    Fink, Matthias; Trunk, Sarah; Hall, Mélanie; Schwab, Helmut; Steiner, Kerstin

    2016-01-01

    Oxidative cleavage of alkenes is a widely employed process allowing oxyfunctionalization to corresponding carbonyl compounds. Recently, a novel biocatalytic oxidative alkene cleavage activity on styrene derivatives was identified in TM1459 from Thermotoga maritima. In this work we engineered the enzyme by site-saturation mutagenesis of active site amino acids to increase its activity and to broaden its substrate scope. A high-throughput assay for the detection of the ketone products was successfully developed. Several variants with up to twofold improved conversion level of styrene derivatives were successfully identified. Especially, changes in or removal of the C-terminus of TM1459 increased the activity most significantly. These best variants also displayed a slightly enlarged substrate scope. PMID:27713741

  5. Oxidative Decarboxylation of Short-Chain Fatty Acids to 1-Alkenes.

    PubMed

    Dennig, Alexander; Kuhn, Miriam; Tassoti, Sebastian; Thiessenhusen, Anja; Gilch, Stefan; Bülter, Thomas; Haas, Thomas; Hall, Mélanie; Faber, Kurt

    2015-07-20

    The enzymatic oxidative decarboxylation of linear short-chain fatty acids (C4:0-C9:0) employing the P450 monooxygenase OleT, O2 as the oxidant, and NAD(P)H as the electron donor gave the corresponding terminal C3 to C8  alkenes with product titers of up to 0.93 g L(-1) and TTNs of >2000. Key to this process was the construction of an efficient electron-transfer chain employing putidaredoxin CamAB in combination with NAD(P)H recycling at the expense of glucose, formate, or phosphite. This system allows for the biocatalytic production of industrially important 1-alkenes, such as propene and 1-octene, from renewable resources for the first time.

  6. Copper-Catalyzed Intramolecular Oxidative Amination of Unactivated Internal Alkenes.

    PubMed

    Xiong, Peng; Xu, Fan; Qian, Xiang-Yang; Yohannes, Yared; Song, Jinshuai; Lu, Xin; Xu, Hai-Chao

    2016-03-18

    A copper-catalyzed oxidative amination of unactivated internal alkenes has been developed. The Wacker-type oxidative alkene amination reaction is traditionally catalyzed by a palladium through a mechanism involving aminopalladation and β-hydride elimination. Replacing the precious and scarce palladium with a cheap and abundant copper for this transformation has been challenging because of the difficulty associated with the aminocupration of internal alkenes. The combination of a simple copper salt, without additional ligand, as the catalyst and Dess-Martin periodinane as the oxidant, promotes efficiently the oxidative amination of allylic carbamates and ureas bearing di- and trisubstituted alkenes leading to oxazolidinones and imidazolidinones. Preliminary mechanistic studies suggested a hybrid radical-organometallic mechanism involving an amidyl radical cyclization to form the key C-N bond.

  7. New approach to the air oxidation of alkenes employing metal nitro complexes as catalysts

    SciTech Connect

    Andrews, M.A.; Chang, T.C.T.; Cheng, C.W.F.; Kelley, K.P.

    1984-01-01

    Alkenes are stoichiometrically and, in the presence of air, catalytically oxidized by cis-bis(aceto-nitrile) chloronitropalladium(II). Oxidation of monosubstituted terminal alkenes and trans-cyclooctene yields the corresponding ketone, oxidation of cyclopentene and cyclohexene the corresponding allyl alcohol, and oxidation of bicyclic alkenes the corresponding epoxide, each with good selectivity for the respective product. Other alkenes give varying mixtures of the above products together with, in some cases, the ..cap alpha..,..beta..-unsaturated ketone. Vinyl ethers yield the corresponding ester while (trimethylsily)ethylene yields (trimethylsilyl)acetaldehyde. The selectivities are rationalized on the basis of ease of ..beta..-hydrogen elimination in observed intermediate heterometallacyclopentane complexes formed by nucleophilic attack of the nitro oxygen atom on the coordinated alkene in alkene nitro complexes. The general role of metallacycles in metal-mediated alkene oxidations and the advantages and disadvantages of intra-vs. intermolecular metal nitro catalyzed alkene oxidations are discussed. 50 references, 4 figures, 3 tables.

  8. Covalent attachment of 1-alkenes to oxidized platinum surfaces.

    PubMed

    Alonso, Jose Maria; Fabre, Bruno; Trilling, Anke K; Scheres, Luc; Franssen, Maurice C R; Zuilhof, Han

    2015-03-10

    We report the formation of covalently bound alkyl layers onto oxidized Pt (PtOx) substrates by reaction with 1-alkenes as a novel way to bind organic molecules to metal surfaces. The organic layers were characterized by static contact angle, infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The grafted alkyl layers display a hydrolytic stability that is comparable to that of alkyl thiols on Au. PtOx-alkene attachment is compatible with terminal ester moieties enabling further anchoring of functional groups, such as redox-active ferrocene, and thus has great potential to extend monolayer chemistry on noble metals.

  9. Oxidations of alkenes and lignin model compounds in aqueous dispersions

    SciTech Connect

    Zhu, Weiming.

    1991-01-01

    The objective was to develop methods to oxidize water-immiscible alkenes and lignin model compounds with polymer colloid supported transition metal catalysts. The oxidations of organic compounds were carried out in aqueous phase with several water-soluble oxidants and dioxygen. Cationic polymer latexes were prepared by the emulsion copolymerization of vinylbenzyl chloride, divinylbenzene, and vinyl octadecyl ether, or styrene, or n-decyl methacrylate, and the subsequent quaternization of copolymers with trimethylamine. The latex particles were 44 nm to 71 nm in diameter. The latex bound Mn porphyrin catalysts were formed with MnTSPP [TSPP = meso-tetrakis(2,6-dichloro-3-sulfonatophenyl)porphyrin], which catalyzed the oxidation of cyclohexene, cycloocetene, allylbenzene, and 1-octene by sodium hypochlorite (NaOCl) and potassium peroxymonosulfate (KHSO[sub 5]). The latex bound porphyrin catalysts showed higher activity than MnTSPP in solution. Oxidations of 3,4-dimethoxybenzyl alcohol (DMBA), 4-hydroxy-3-methoxytoluene (HMT), and 3,4-dimethoxytoluene (DMT) were performed with either dioxygen or hydrogen peroxide and CoPcTS (PcTS = tetrasulfonatophthalocyanine), FePcTS, CuPcTS, NiPcTS, FeTCPP [TCPP = meso-tetrakis(4-carboxyphenyl)porphyrin], and MnTSPP. CoPcTS catalyzed the autoxidation of DMBA and HMT at 70-85[degrees]C and pH [ge] 8. All catalysts were active for the oxidation of DMBA, HMT, and DMT with H[sub 2]O[sub 2]. Aqueous solutions of KHSO[sub 5] oxidized water-immiscible alkenes at room temperature in the absence of organic solvent. The acidic pH [le] 1.7 solutions of commercial 2KHSO[sub 5][center dot]K[sub 2]SO[sub 4] in water produced diols from all reactive alkenes except cyclooctene. Adjustment of initial pH to [ge]6.7 with NaHCO[sub 3] enabled selective epoxidations.

  10. Cl atom initiated oxidation of 1-alkenes under atmospheric conditions

    NASA Astrophysics Data System (ADS)

    Walavalkar, M.; Sharma, A.; Alwe, H. D.; Pushpa, K. K.; Dhanya, S.; Naik, P. D.; Bajaj, P. N.

    2013-03-01

    In view of the importance of the oxidation pathways of alkenes in the troposphere, and the significance of Cl atom as an oxidant in marine boundary layer (MBL) and polluted industrial atmosphere, the reactions of four 1-alkenes (C6-C9) with Cl atoms are investigated. The rate coefficients at 298 K are measured to be (4.0 ± 0.5), (4.4 ± 0.7), (5.5 ± 0.9) and (5.9 ± 1.7) × 10-10 cm3 molecule-1 s-1 for 1-hexene, 1-heptene, 1-octene and 1-nonene, respectively. The quoted errors include the experimental 2σ, along with the error in the reference rate coefficients. From the systematic increase in the rate coefficients with the number of carbon atoms, an approximate value for the average rate coefficient for hydrogen abstraction per CH2 group in alkenes is estimated to be (4.9 ± 0.3) × 10-11 cm3 molecule-1 s-1. Based on these rate coefficients, the contribution of Cl atom reactions towards the degradation of these molecules is found to be comparable to that of OH radical reactions, under MBL conditions. The products identified in gas phase indicate that Cl atom addition occurs mainly at the terminal carbon, leading to the formation of 1-chloro-2-ketones and 1-chloro-2-ols. The major gas phase products from the alkenyl radicals (formed by H atom abstraction) are different positional isomers of long chain enols and enones. A preference for dissociation leading to an allyl radical, resulting in aldehydes, lower by three carbon atoms, is indicated. The observed relative yields suggest that in general, the increased contribution of the reactions of Cl atoms towards degradation of 1-alkenes in NOx free air does not result in an increase in the generation of small aldehydes (carbon number < 4), including chloroethanal, as compared to that in the reaction of 1-butene.

  11. Copper-Catalyzed Oxidative Amination and Allylic Amination of Alkenes

    PubMed Central

    Liwosz, Timothy W.; Chemler, Sherry R.

    2014-01-01

    Enamines and enamides are useful synthetic intermediates and common components of bioactive compounds. A new protocol for their direct synthesis by a net alkene C–H amination and allylic amination by using catalytic CuII in the presence of MnO2 is reported. Reactions between N-aryl sulfonamides and vinyl arenes furnish enamides, allylic amines, indoles, benzothiazine dioxides, and dibenzazepines directly and efficiently. Control experiments further showed that MnO2 alone can promote the reaction in the absence of a copper salt, albeit with lower efficiency. Mechanistic probes support the involvement of nitrogen-radical intermediates. This method is ideal for the synthesis of enamides from 1,1-disubstituted vinyl arenes, which are uncommon substrates in existing oxidative amination protocols. PMID:23878099

  12. Oxidative Allylic Esterification of Alkenes by Cooperative Selenium-Catalysis Using Air as the Sole Oxidant.

    PubMed

    Ortgies, Stefan; Depken, Christian; Breder, Alexander

    2016-06-17

    A new metal-free catalysis protocol for the oxidative coupling of nonactivated alkenes with simple carboxylic acids has been established. This method is predicated on the cooperative interaction of a diselane and a photoredox catalyst, which allows for the use of ambient air or pure O2 as the terminal oxidant. Under the title conditions, a range of both functionalized and nonfunctionalized alkenes can be readily converted into the corresponding allylic ester products with good yields (up to 89%) and excellent regioselectivity as well as good functional group tolerance.

  13. Oxidative Allylic Esterification of Alkenes by Cooperative Selenium-Catalysis Using Air as the Sole Oxidant.

    PubMed

    Ortgies, Stefan; Depken, Christian; Breder, Alexander

    2016-06-17

    A new metal-free catalysis protocol for the oxidative coupling of nonactivated alkenes with simple carboxylic acids has been established. This method is predicated on the cooperative interaction of a diselane and a photoredox catalyst, which allows for the use of ambient air or pure O2 as the terminal oxidant. Under the title conditions, a range of both functionalized and nonfunctionalized alkenes can be readily converted into the corresponding allylic ester products with good yields (up to 89%) and excellent regioselectivity as well as good functional group tolerance. PMID:27257803

  14. A biocatalytic route towards rose oxide using chloroperoxidase.

    PubMed

    Piantini, Umberto; Schrader, Jens; Wawrzun, Andrzej; Wüst, Matthias

    2011-12-01

    The chiral monoterpene alcohol citronellol was converted to the corresponding bromohydrin by the haem-thiolate enzyme chloroperoxidase (CPO) from Caldariomyces fumago in the presence of hydrogen peroxide and bromide ions. A conversion rate of 51% could be achieved under adapted reaction conditions, which easily yield product in the gramme per litre range while only needing catalytic amounts of enzyme. The bromohydroxylation was shown to be highly regioselective yielding 6-bromo-3,7-dimethyloctane-1,7-diol as the sole product. Product identity was confirmed by GC-MS, (1)H- and (13)C-NMR spectroscopy and the synthesis of reference compounds. However, the reaction was shown to be non-stereospecific because enantiopure (R)- and (S)-citronellol, respectively, gave 1:1-diasteromeric mixtures of the corresponding bromohydrins. A racemic mixture of (R/S)-citronellol was bromohydroxylated without any detectable enantiodiscrimination. The total lack of stereospecificity and enantiodiscrimination points to a reaction mechanism where the oxidised bromide intermediate is not a ligand to the Fe(III)-haem at the distal site but is released from the enzyme active site. The final bromide transfer occurs probably outside the active site via a diffusible oxidised bromide species and the demonstrated regioselectivity is purely chemically controlled. The generated bromohydrins can be straightforward converted via two reactions steps into rose oxide which is a highly valuable flavour and fragrance substance.

  15. Pd(Quinox)-Catalyzed Allylic Relay Suzuki Reactions of Secondary Homostyrenyl Tosylates via Alkene-Assisted Oxidative Addition.

    PubMed

    Stokes, Benjamin J; Bischoff, Amanda J; Sigman, Matthew S

    2014-06-01

    Pd-catalyzed allylic relay Suzuki cross-coupling reactions of secondary alkyl tosylates, featuring a sterically-hindered oxidative addition and precise control of β-hydride elimination, are reported. The identification of a linear free energy relationship between the relative rates of substrate consumption and the electronic nature of the substrate alkene suggests that the oxidative addition requires direct alkene involvement. A study of the effect of chain length on the reaction outcome supports a chelation-controlled oxidative addition.

  16. Tuning graphitic oxide for initiator- and metal-free aerobic epoxidation of linear alkenes

    NASA Astrophysics Data System (ADS)

    Pattisson, Samuel; Nowicka, Ewa; Gupta, Upendra N.; Shaw, Greg; Jenkins, Robert L.; Morgan, David J.; Knight, David W.; Hutchings, Graham J.

    2016-09-01

    Graphitic oxide has potential as a carbocatalyst for a wide range of reactions. Interest in this material has risen enormously due to it being a precursor to graphene via the chemical oxidation of graphite. Despite some studies suggesting that the chosen method of graphite oxidation can influence the physical properties of the graphitic oxide, the preparation method and extent of oxidation remain unresolved for catalytic applications. Here we show that tuning the graphitic oxide surface can be achieved by varying the amount and type of oxidant. The resulting materials differ in level of oxidation, surface oxygen content and functionality. Most importantly, we show that these graphitic oxide materials are active as unique carbocatalysts for low-temperature aerobic epoxidation of linear alkenes in the absence of initiator or metal. An optimum level of oxidation is necessary and materials produced via conventional permanganate-based methods are far from optimal.

  17. Tuning graphitic oxide for initiator- and metal-free aerobic epoxidation of linear alkenes

    PubMed Central

    Pattisson, Samuel; Nowicka, Ewa; Gupta, Upendra N.; Shaw, Greg; Jenkins, Robert L.; Morgan, David J.; Knight, David W.; Hutchings, Graham J.

    2016-01-01

    Graphitic oxide has potential as a carbocatalyst for a wide range of reactions. Interest in this material has risen enormously due to it being a precursor to graphene via the chemical oxidation of graphite. Despite some studies suggesting that the chosen method of graphite oxidation can influence the physical properties of the graphitic oxide, the preparation method and extent of oxidation remain unresolved for catalytic applications. Here we show that tuning the graphitic oxide surface can be achieved by varying the amount and type of oxidant. The resulting materials differ in level of oxidation, surface oxygen content and functionality. Most importantly, we show that these graphitic oxide materials are active as unique carbocatalysts for low-temperature aerobic epoxidation of linear alkenes in the absence of initiator or metal. An optimum level of oxidation is necessary and materials produced via conventional permanganate-based methods are far from optimal. PMID:27687877

  18. Hydroxy nitrate production in the OH-initiated oxidation of alkenes

    NASA Astrophysics Data System (ADS)

    Teng, A. P.; Crounse, J. D.; Lee, L.; St. Clair, J. M.; Cohen, R. C.; Wennberg, P. O.

    2015-04-01

    Alkenes are oxidized rapidly in the atmosphere by addition of OH and subsequently O2 leading to the formation of β-hydroxy peroxy radicals. These peroxy radicals react with NO to form β-hydroxy nitrates with a branching ratio α. We quantify α for CM2-C8 alkenes at 295 K ± 3 and 993 hPa. The branching ratio can be expressed as α = (0.045 ± 0.016) × N - (0.11 ± 0.05) where N is the number of heavy atoms (excluding the peroxy moiety), and listed errors are 2σ. These branching ratios are larger than previously reported and are similar to those for peroxy radicals formed from H abstraction from alkanes. We find the isomer distributions of β-hydroxy nitrates formed under NO-dominated peroxy radical chemistry to be different than the isomer distribution of hydroxy hydroperoxides produced under HO2-dominated peroxy radical chemistry. Assuming unity yield for the hydroperoxides implies that the branching ratio to form β-hydroxy nitrates increases with substitution of RO2. Deuterium substitution enhances the branching ratio to form hydroxy nitrates in both propene and isoprene by a factor of ~ 1.5. The role of alkene chemistry in the Houston region is re-evaluated using the RONO2 branching ratios reported here. Small alkenes are found to play a significant role in present-day oxidant formation more than a decade (2013) after the 2000 Texas Air Quality Study identified these compounds as major contributors to photochemical smog in Houston.

  19. Biocatalytic desulfurization

    SciTech Connect

    Monticello, D.J. )

    1994-02-01

    Biocatalytic desulfurization (BDS) has many advantages compared to traditional refinery desulfurization processes, including: lower capital and operating costs, low-temperature and low-pressure operation and no hydrogen requirement. Biotechnology has developed from an art into a science in recent years. The HPI is familiar with an artful' application of biotechnology in the biotreatment of refinery wastes, and has experimented with other technologies for over 50 years. This paper discusses the following: biorefining, sulfur management, conventional solutions, bioprocessing precedents, new biotechnology tools, microbial desulfurization, biocatalytic desulfurization, specificity, biodesulfurization conceptual design, development issues, and implementation.

  20. Polymer - supported cobalt (II) catalysts for the oxidation of alkenes.

    PubMed

    Błaz, Edyta; Pielichowski, Jan

    2006-01-31

    Polymer-supported heterogeneous catalysts in a form of complexes of 8-hydroxy- quinoline with cobalt acetate were synthesized. Conjugated polymers - polyaniline (PANI), poly-o-toluidine (POT), poly-o-anisidine (POA) - were used as supports. Oxidation reactions of aliphatic and aromatic hydrocarbons were carried out in the presence of molecular oxygen at atmospheric pressure and epoxides or ketones were obtained as the main products with high selectivity.

  1. Branched zinc oxide nanorods arrays modified paper electrode for electrochemical immunosensing by combining biocatalytic precipitation reaction and competitive immunoassay mode.

    PubMed

    Sun, Guoqiang; Yang, Hongmei; Zhang, Yan; Yu, Jinghua; Ge, Shenguang; Yan, Mei; Song, Xianrang

    2015-12-15

    Branched zinc oxide nanorods (BZR) arrays, an array with high charge carries collection efficiency and specific surface area, are grown on the reduced graphene oxide-paper working electrode for the first time to construct a paper-based electrochemical (EC) immunosensor. Typically, the BZR are fabricated via a simple hydrothermal process, which can provide abundant sites for antibodies loading. By combining the large surface area of porous zinc oxide (PZS) and good biocompatibility of gold nanoparticles (AuNPs), PZS-AuNPs (PZS@Au) nanocomposites are designed to label horseradish peroxide (HRP) and antigens. After a competitive reaction between antigens and PZS@Au nanocomposites labeled antigens, the signal labels are introduced into the immunosensor, in which, HRP participate in biocatalytic precipitation process. The produced precipitate reduces the electrode surface area and hinders the electron transfer. With the increase of concentration of antigens, the signal labels introduced into the sensor decrease, thus, a signal-on immunoassay for α-fetoprotein detection is constructed. The proposed paper-based EC immunosensor combines enzymatic biocatalytic precipitation reaction and competitive immunoassay mode for the first time, and possesses a wide linear range from 0.2 pg mL(-1) to 500 ng mL(-1) with a detection limit of 0.08 pg mL(-1). In addition, the proposed method is simple, sensitive and specific and can be a promising platform for other protein detection.

  2. Regioselective aerobic oxidative Heck reactions with electronically unbiased alkenes: efficient access to α-alkyl vinylarenes.

    PubMed

    Zheng, Changwu; Stahl, Shannon S

    2015-08-18

    Branched-selective oxidative Heck coupling reactions have been developed between arylboronic acids and electronically unbiased terminal alkenes. The reactions exhibit high catalyst-controlled regioselectivity favoring the less common branched isomer. The reactions employ a catalyst composed of Pd(TFA)2/dmphen (TFA = trifluoroacetate, dmphen = 2,9-dimethyl-1,10-phenanthroline) and proceed efficiently at 45-60 °C under 1 atm of O2 without requiring other additives. A broad array of functional groups, including aryl halide, allyl silane and carboxylic acids are tolerated.

  3. Mechanistic Studies of Wacker-Type Intramolecular Aerobic Oxidative Amination of Alkenes Catalyzed by Pd(OAc)2/Pyridine

    PubMed Central

    Ye, Xuan; Liu, Guosheng; Popp, Brian V.; Stahl, Shannon S.

    2011-01-01

    Wacker-type oxidative cyclization reactions have been the subject of extensive research for several decades, but few systematic mechanistic studies of these reactions have been reported. The present study features experimental and DFT computational studies of Pd(OAc)2/pyridine-catalyzed intramolecular aerobic oxidative amination of alkenes. The data support a stepwise catalytic mechanism that consists of (1) steady-state formation of a PdII-amidate-alkene chelate with release of one equivalent of pyridine and AcOH from the catalyst center, (2) alkene insertion into a Pd–N bond, (3) reversible β-hydride elimination, (4) irreversible reductive elimination of AcOH, and (5) aerobic oxidation of palladium(0) to regenerate the active trans-Pd(OAc)2(py)2 catalyst. Evidence is obtained for two energetically viable pathways for the key C–N bond-forming step, featuring a pyridine-ligated and a pyridine-dissociated PdII species. Analysis of natural charges and bond lengths of the alkene-insertion transition state suggest that this reaction is best described as an intramolecular nucleophilic attack of the amidate ligand on the coordinated alkene. PMID:21250706

  4. Formation of highly oxidized multifunctional compounds: Autoxidation of peroxy radicals formed in the oxidation of alkenes

    NASA Astrophysics Data System (ADS)

    Mentel, Thomas; Ehn, Mikael; Thornton, Joel; Kleist, Einhard; Pullinen, Iida; Springer, Monika; Wahner, Andreas; Wildt, Jürgen

    2015-04-01

    Recent studies show that peroxy radicals are key intermediates in particle formation. Permutation reactions involving highly oxidized peroxy radicals form stable products with extremely low volatility (ELVOC). We suggest that ELVOC are the postulated organic compounds that explain growth of small particles (Ehn et al., Nature, 2014). To elucidate the pathways of ELVOC formation, experiments were performed in the Juelich Plant Atmosphere Chamber. We applied High Resolution Nitrate-Chemical Ionization Mass Spectrometry for detection of ELVOC including highly oxidized peroxy radicals. ELVOC were produced by ozonolysis of a-pinene and other cyclic alkenes (Rissanen et al., JACS, 2014, Mentel et al., ACPD, 2015), as well as by reactions of the target compounds with OH. ELVOC with C10 skeletons carry a large number of oxygens, still containing 14 or 16 H-atoms. ELVOC-dimers with twice the number of C-atoms of the reactant were also observed. The formation of ELVOC can be explained by fast intramolecular H-shifts in combination with classical peroxy radical termination reactions, leading to ketones, alcohols, and hydroperoxides (including peroxy acids). The subsequent H-shifts enable the formation of an increasing number of hydroperoxide groups under reproduction of a peroxy radical (containing now two more oxygens). Addition of NOX to the system increases the concentrations of nitrates at the expense of the corresponding peroxy radicals, confirming their identification as peroxy radicals. Furthermore, the concentrations of ELVOC dimers decrease strongly with increasing NOX suggesting that they are indeed formed by peroxy-peroxy permutation reactions. ELVOC are involved in new particle formation, and can explain the major fraction of the early growth observed in field studies. ELVOC dimers are very likely key in new particle formation as their formation is strongly suppressed with increasing NOX in accordance with the observed NOX dependence of new particle formation (Ehn

  5. Biocatalytic Properties and Structural Analysis of Eugenol Oxidase from Rhodococcus jostii RHA1: A Versatile Oxidative Biocatalyst.

    PubMed

    Nguyen, Quoc-Thai; de Gonzalo, Gonzalo; Binda, Claudia; Rioz-Martínez, Ana; Mattevi, Andrea; Fraaije, Marco W

    2016-07-15

    Eugenol oxidase (EUGO) from Rhodococcus jostii RHA1 had previously been shown to convert only a limited set of phenolic compounds. In this study, we have explored the biocatalytic potential of this flavoprotein oxidase, resulting in a broadened substrate scope and a deeper insight into its structural properties. In addition to the oxidation of vanillyl alcohol and the hydroxylation of eugenol, EUGO can efficiently catalyze the dehydrogenation of various phenolic ketones and the selective oxidation of a racemic secondary alcohol-4-(1-hydroxyethyl)-2-methoxyphenol. EUGO was also found to perform the kinetic resolution of a racemic secondary alcohol. Crystal structures of the enzyme in complexes with isoeugenol, coniferyl alcohol, vanillin, and benzoate have been determined. The catalytic center is a remarkable solvent-inaccessible cavity on the si side of the flavin cofactor. Structural comparison with vanillyl alcohol oxidase from Penicillium simplicissimum highlights a few localized changes that correlate with the selectivity of EUGO for phenolic substrates bearing relatively small p-substituents while tolerating o-methoxy substituents. PMID:27123962

  6. Water independent SO2 oxidation by Stabilised Criegee Intermediates from Biogenic Alkenes

    NASA Astrophysics Data System (ADS)

    Newland, Mike; Rickard, Andrew; Vereecken, Luc; Evans, Mat; Muñoz, Amalia; Ródenas, Milagros; Bloss, William

    2015-04-01

    Biogenic VOCs account for about 90% of global VOC emissions and these are dominated by the unsaturated hydrocarbons: isoprene (600 Tg yr-1) and monoterpenes (100 Tg yr-1). Stabilized Criegee Intermediates (SCI) are thought to be formed in the atmosphere mainly from reactions of unsaturated hydrocarbons with ozone. SCI have been shown in laboratory experiments to rapidly oxidise SO2 (k > 2x10-11 cm3 s-1) and NO2 (k = 7x10-12 cm3 s-1), providing a potentially important gas phase oxidation route for these species in the atmosphere. The importance of the SCI reaction with traces gases has been shown in modelling work to be critically dependent on the ratio of the rate constants for the reaction of the SCI with these trace gases and with H2O. Such modelling work has suggested that the SCI + SO2 reaction is only likely to be important in regions with high alkene emissions, e.g. forests, and that elsewhere SCI are likely to be almost entirely quenched by reaction with water, thus negating their importance as trace gas oxidants. However, it has been shown in laboratory experiments with small SCI that the reaction rate of SCI with water is structure dependent, with anti-CH3CHOO reacting fast with H2O (k > 1x10-14 cm3 s-1), and syn-CH3CHOO reacting orders of magnitude slower (k < 2x10-16 cm3 s-1). Here we present results from a series of ozonolysis experiments performed at the EUPHORE atmospheric simulation chamber in Valencia. These experiments measure the loss of SO2, in the presence of various biogenic alkenes (isoprene and three monoterpenes: α-pinene, β-pinene and limonene), as a function of water vapour. The SO2 loss shows a dependence on relative humidity for all systems studied, decreasing with increasing relative humidity. However, for all species, there also appears to be a fraction of the SO2 loss that shows a much lower sensitivity to relative humidity. We quantify the relative rates of reaction of the SCI produced in the ozonolysis of these biogenics with

  7. [3 + 2] cycloaddition and subsequent oxidative dehydrogenation between alkenes and diazo compounds: a simple and direct approach to pyrazoles using TBAI/TBHP.

    PubMed

    Shao, Ying; Tong, Jingjing; Zhao, Yanwei; Zheng, Hao; Ma, Liang; Ma, Meihua; Wan, Xiaobing

    2016-09-28

    A novel Bu4NI-catalyzed pyrazole formation reaction is well described via sequential [3 + 2] cycloaddition and oxidative dehydrogenation reactions using TBHP as the primary oxidant. In comparison with previous cases toward pyrazoles from alkenes and diazo compounds, alkenes without a pre-organized leaving group were applied in this transformation. In addition, this methodology was distinguished by its broad substrate scope, commercially available inexpensive starting materials, high atom economy and operational simplicity. PMID:27539888

  8. Cofactor Specificity Engineering of Streptococcus mutans NADH Oxidase 2 for NAD(P)(+) Regeneration in Biocatalytic Oxidations.

    PubMed

    Petschacher, Barbara; Staunig, Nicole; Müller, Monika; Schürmann, Martin; Mink, Daniel; De Wildeman, Stefaan; Gruber, Karl; Glieder, Anton

    2014-01-01

    Soluble water-forming NAD(P)H oxidases constitute a promising NAD(P)(+) regeneration method as they only need oxygen as cosubstrate and produce water as sole byproduct. Moreover, the thermodynamic equilibrium of O2 reduction is a valuable driving force for mostly energetically unfavorable biocatalytic oxidations. Here, we present the generation of an NAD(P)H oxidase with high activity for both cofactors, NADH and NADPH. Starting from the strictly NADH specific water-forming Streptococcus mutans NADH oxidase 2 several rationally designed cofactor binding site mutants were created and kinetic values for NADH and NADPH conversion were determined. Double mutant 193R194H showed comparable high rates and low K m values for NADPH (k cat 20 s(-1), K m 6 µM) and NADH (k cat 25 s(-1), K m 9 µM) with retention of 70% of wild type activity towards NADH. Moreover, by screening of a SeSaM library S. mutans NADH oxidase 2 variants showing predominantly NADPH activity were found, giving further insight into cofactor binding site architecture. Applicability for cofactor regeneration is shown for coupling with alcohol dehydrogenase from Sphyngobium yanoikuyae for 2-heptanone production.

  9. Biocatalytic conversion of ethylene to ethylene oxide using an engineered toluene monooxygenase.

    PubMed

    Carlin, D A; Bertolani, S J; Siegel, J B

    2015-02-11

    Mutants of toluene o-xylene monooxygenase are demonstrated to oxidize ethylene to ethylene oxide in vivo at yields of >99%. The best mutant increases ethylene oxidation activity by >5500-fold relative to the native enzyme. This is the first report of a recombinant enzyme capable of carrying out this industrially significant chemical conversion.

  10. Biocatalytic conversion of ethylene to ethylene oxide using an engineered toluene monooxygenase

    SciTech Connect

    Carlin, DA; Bertolani, SJ; Siegel, JB

    2015-01-01

    Mutants of toluene o-xylene monooxygenase are demonstrated to oxidize ethylene to ethylene oxide in vivo at yields of >99%. The best mutant increases ethylene oxidation activity by >5500-fold relative to the native enzyme. This is the first report of a recombinant enzyme capable of carrying out this industrially significant chemical conversion.

  11. Biocatalytic Dynamic Kinetic Resolution for the Synthesis of Atropisomeric Biaryl N-Oxide Lewis Base Catalysts.

    PubMed

    Staniland, Samantha; Adams, Ralph W; McDouall, Joseph J W; Maffucci, Irene; Contini, Alessandro; Grainger, Damian M; Turner, Nicholas J; Clayden, Jonathan

    2016-08-26

    Atropisomeric biaryl pyridine and isoquinoline N-oxides were synthesized enantioselectively by dynamic kinetic resolution (DKR) of rapidly racemizing precursors exhibiting free bond rotation. The DKR was achieved by ketoreductase (KRED) catalyzed reduction of an aldehyde to form a configurationally stable atropisomeric alcohol, with the substantial increase in rotational barrier arising from the loss of a bonding interaction between the N-oxide and the aldehyde. Use of different KREDs allowed either the M or P enantiomer to be synthesized in excellent enantiopurity. The enantioenriched biaryl N-oxide compounds catalyze the asymmetric allylation of benzaldehyde derivatives with allyltrichlorosilane. PMID:27504722

  12. Enhanced Biocatalytic Esterification with Lipase-Immobilized Chitosan/Graphene Oxide Beads

    PubMed Central

    Lau, Siaw Cheng; Lim, Hong Ngee; Basri, Mahiran; Fard Masoumi, Hamid Reza; Ahmad Tajudin, Asilah; Huang, Nay Ming; Pandikumar, Alagarsamy; Chia, Chi Hua; Andou, Yoshito

    2014-01-01

    In this work, lipase from Candida rugosa was immobilized onto chitosan/graphene oxide beads. This was to provide an enzyme-immobilizing carrier with excellent enzyme immobilization activity for an enzyme group requiring hydrophilicity on the immobilizing carrier. In addition, this work involved a process for the preparation of an enzymatically active product insoluble in a reaction medium consisting of lauric acid and oleyl alcohol as reactants and hexane as a solvent. This product enabled the stability of the enzyme under the working conditions and allowed the enzyme to be readily isolated from the support. In particular, this meant that an enzymatic reaction could be stopped by the simple mechanical separation of the “insoluble” enzyme from the reaction medium. Chitosan was incorporated with graphene oxide because the latter was able to enhance the physical strength of the chitosan beads by its superior mechanical integrity and low thermal conductivity. The X-ray diffraction pattern showed that the graphene oxide was successfully embedded within the structure of the chitosan. Further, the lipase incorporation on the beads was confirmed by a thermo-gravimetric analysis. The lipase immobilization on the beads involved the functionalization with coupling agents, N-hydroxysulfosuccinimide sodium (NHS) and 1-ethyl-(3-dimethylaminopropyl) carbodiimide (EDC), and it possessed a high enzyme activity of 64 U. The overall esterification conversion of the prepared product was 78% at 60°C, and it attained conversions of 98% and 88% with commercially available lipozyme and novozyme, respectively, under similar experimental conditions. PMID:25127038

  13. The use of microscale processing technologies for quantification of biocatalytic Baeyer-Villiger oxidation kinetics.

    PubMed

    Doig, Steven D; Pickering, Samuel C R; Lye, Gary J; Woodley, John M

    2002-10-01

    Microscale processing techniques would be a useful tool for the rapid and efficient collection of biotransformation kinetic data as a basis for bioprocess design. Automated liquid handling systems can reduce labor intensity while the small scale reduces the demand for scarce materials such as substrate, product, and biocatalyst. Here we illustrate this concept by establishing the use of several microwell formats (96-round, 96-deep square and 24-round well microtiter plates) for quantification of the kinetics of the E. coli TOP10 [pQR239] resting cell catalyzed Baeyer-Villiger oxidation of bicyclo[3.2.0]hept-2en-6-one using glycerol as a source of reducing power. By increasing the biocatalyst concentration until the biotransformation rate was oxygen mass-transfer limited we can ensure that kinetic data collected are in the region away from oxygen limitation. Using a 96-round well plate the effect of substrate (bicyclo[3.2.0]hept-2en-6-one) concentration on the volumetric CHMO activity was examined and compared to data collected from 1.5-L stirred-tank experiments. The phenomenon and magnitude of substrate inhibition, observed at the larger scale, was accurately reproduced in the microwell format. We have used this as an illustrative example to demonstrate that under adequately defined conditions, automated microscale processing technologies can be used for the collection of quantitative kinetic data. Additionally, by using the experimentally determined stoichiometry for product formation and glycerol oxidation, we have estimated the maximum oxygen transfer rates as a function of well geometry and agitation rate. Oxygen-transfer rates with an upper limit of between 33 mmol. L(-1). h(-1) (based solely on product formation) and 390 mmol. L(-1). h(-1) (based on product formation and glycerol oxidation) were achieved using a 96-square well format plate shaken at 1300 rpm operated with a static surface area to volume ratio of 320 m(2). m(-3).

  14. Cobalt salophen complex supported on imidazole functionalized magnetic nanoparticles as a recoverable catalyst for oxidation of alkenes

    NASA Astrophysics Data System (ADS)

    Afshari, Mozhgan; Gorjizadeh, Maryam; Nazari, Simin; Naseh, Mohammad

    2014-08-01

    A new magnetically separable catalyst consisting of Co(II) salophen complex covalently supported on imidazole functionalized silica coated cobalt ferrite was prepared. The synthesized catalyst was characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and Fourier transform infrared (FT-IR). The immobilized catalyst was shown to be an efficient heterogeneous catalyst for the oxidation of some alkenes using hydrogen peroxide (H2O2) as oxidant. The catalyst could be easily and efficiently isolated from the final product solution by magnetic decantation and be reused for 5 consecutive reactions without showing any significant activity degradation.

  15. Alkene oxidation catalyzed by a ruthenium-substituted heteropolyanion, SiRu(L)W sub 11 O sub 39 : The mechanism of the periodate mediated oxidative cleavage

    SciTech Connect

    Neumann, R.; Abu-Gnim, C. )

    1990-08-01

    A ruthenium-substituted heteropolyanion SiRu(H{sub 2}O)W{sub 11}O{sub 39}{sup 5{minus}} was synthesized and characterized. The hydrophobic quaternary ammonium salt of the heteropolyanion ((C{sub 6}H{sub 13}){sub 4}N){sub 5}SiRu{sup III}(H{sub 2}O)W{sub 11}O{sub 39} was used as a catalyst for the oxidation of alkenes with tert-butyl hydroperoxide, potassium persulfate, iodosobenzene, and sodium periodate as primary oxidants. Reactivity and selectivity were found to be dependent on the oxidant used; several different types of oxidation processes could be identified including allylic oxidation, epoxidation, and oxidative cleavage. Use of sodium periodate as oxidant enabled selective bond cleavage with aldehydes as the exclusive product.

  16. Direct conversion of allyl arenes to aryl ethylketones via a TBHP-mediated palladium-catalyzed tandem isomerization-Wacker oxidation of terminal alkenes.

    PubMed

    Zhao, JinWu; Liu, Li; Xiang, ShiJian; Liu, Qiang; Chen, HuoJi

    2015-05-28

    A TBHP-mediated palladium-catalyzed tandem isomerization-Wacker oxidation of terminal alkenes was developed. This methodology provides a new efficient and simple route for conversion of a range of allyl arenes directly into aryl ethylketones in good yields with high chemoselectivity.

  17. Total synthesis of gracilioether F. Development and application of Lewis acid promoted ketene–alkene [2+2] cycloadditions and late-stage C—H oxidation

    SciTech Connect

    Rasik, Christopher M.; Brown, M. Kevin

    2014-12-22

    The first synthesis of gracilioether F, a polyketide natural product with an unusual tricyclic core and five contiguous stereocenters, is described. Key steps of the synthesis include a Lewis acid promoted ketene–alkene [2+2] cycloaddition and a late-stage carboxylic acid directed C(sp³)—H oxidation. The synthesis requires only eight steps from norbornadiene.

  18. Ozonolysis of surface adsorbed methoxyphenols: kinetics of aromatic ring cleavage vs. alkene side-chain oxidation

    NASA Astrophysics Data System (ADS)

    O'Neill, E. M.; Kawam, A. Z.; Van Ry, D. A.; Hinrichs, R. Z.

    2013-07-01

    Lignin pyrolysis products, which include a variety of substituted methoxyphenols, constitute a major component of organics released by biomass combustion and may play a central role in the formation of atmospheric brown carbon. Understanding the atmospheric fate of these compounds upon exposure to trace gases is therefore critical to predicting the chemical and physical properties of biomass burning aerosol. We used diffuse reflectance infrared spectroscopy to monitor the heterogeneous ozonolysis of 4-propylguaiacol, eugenol, and isoeugenol adsorbed on NaCl and α-Al2O3 substrates. Adsorption of gaseous methoxyphenols onto these substrates produced near monolayer surface concentrations of 3 × 1018 molecules m-2. The subsequent dark heterogeneous ozonolysis of adsorbed 4-propylguaiacol cleaved the aromatic ring between the methoxy and phenol groups with the product conclusively identified by GC-MS and 1H-NMR. Kinetic analysis of eugenol and isoeugenol dark ozonolysis also suggested the formation of ring-cleaved products, although ozonolysis of the unsaturated substituent groups forming carboxylic acids and aldehydes was an order of magnitude faster. Average uptake coefficients for NaCl-adsorbed methoxyphenols were γ = 2.3 (±0.8) × 10-7 and 2 (±1) × 10-6 for ozonolysis of the aromatic ring and the unsaturated side chain, respectively, and reactions on α-Al2O3 were approximately two times slower. UV-visible radiation (λ>300 nm) enhanced eugenol ozonolysis of the aromatic ring by a factor of 4(±1) but had no effect on ozonolysis of the alkene side-chain.

  19. Geminal bis(silane)-controlled regio- and stereoselective oxidative Heck reaction of enol ethers with terminal alkenes to give push-pull 1,3-dienes.

    PubMed

    Li, Linjie; Chu, Yang; Gao, Lu; Song, Zhenlei

    2015-11-01

    A geminal bis(silane)-controlled regio- and stereoselective oxidative Heck reaction of enol ethers with terminal alkenes has been developed. The reaction proceeds with α,β-coupling regioselectivity to give push-pull Z,E-1,3-dienes in good yields. The product showed valuable utility in Sakurai homoallylation with acetals to generate α-substituted-γ-keto esters with good anti-selectivity.

  20. Self-assembled monolayers of 1-alkenes on oxidized platinum surfaces as platforms for immobilized enzymes for biosensing

    NASA Astrophysics Data System (ADS)

    Alonso, Jose Maria; Bielen, Abraham A. M.; Olthuis, Wouter; Kengen, Servé W. M.; Zuilhof, Han; Franssen, Maurice C. R.

    2016-10-01

    Alkene-based self-assembled monolayers grafted on oxidized Pt surfaces were used as a scaffold to covalently immobilize oxidase enzymes, with the aim to develop an amperometric biosensor platform. NH2-terminated organic layers were functionalized with either aldehyde (CHO) or N-hydroxysuccinimide (NHS) ester-derived groups, to provide anchoring points for enzyme immobilization. The functionalized Pt surfaces were characterized by X-ray photoelectron spectroscopy (XPS), static water contact angle (CA), infrared reflection absorption spectroscopy (IRRAS) and atomic force microscopy (AFM). Glucose oxidase (GOX) was covalently attached to the functionalized Pt electrodes, either with or without additional glutaraldehyde crosslinking. The responses of the acquired sensors to glucose concentrations ranging from 0.5 to 100 mM were monitored by chronoamperometry. Furthermore, lactate oxidase (LOX) and human hydroxyacid oxidase (HAOX) were successfully immobilized onto the PtOx surface platform. The performance of the resulting lactate sensors was investigated for lactate concentrations ranging from 0.05 to 20 mM. The successful attachment of active enzymes (GOX, LOX and HAOX) on Pt electrodes demonstrates that covalently functionalized PtOx surfaces provide a universal platform for the development of oxidase enzyme-based sensors.

  1. PALLADIUM-CATALYZED OXIDATION OF STYRENE AND ALKENES IN PRESENCE OF IONIC LIQUIDS (WACKER REACTION)

    EPA Science Inventory

    The use of ionic liquids in various synthetic transformations is gaining significance due to the enhanced reaction rates, potential for recycling and compatibility with various organic compounds and organometallic catalysts. Palladium-catalyzed oxidation of styrene and other alk...

  2. NOx analyser interefence from alkenes

    NASA Astrophysics Data System (ADS)

    Bloss, W. J.; Alam, M. S.; Lee, J. D.; Vazquez, M.; Munoz, A.; Rodenas, M.

    2012-04-01

    Nitrogen oxides (NO and NO2, collectively NOx) are critical intermediates in atmospheric chemistry. NOx abundance controls the levels of the primary atmospheric oxidants OH, NO3 and O3, and regulates the ozone production which results from the degradation of volatile organic compounds. NOx are also atmospheric pollutants in their own right, and NO2 is commonly included in air quality objectives and regulations. In addition to their role in controlling ozone formation, NOx levels affect the production of other pollutants such as the lachrymator PAN, and the nitrate component of secondary aerosol particles. Consequently, accurate measurement of nitrogen oxides in the atmosphere is of major importance for understanding our atmosphere. The most widely employed approach for the measurement of NOx is chemiluminescent detection of NO2* from the NO + O3 reaction, combined with NO2 reduction by either a heated catalyst or photoconvertor. The reaction between alkenes and ozone is also chemiluminescent; therefore alkenes may contribute to the measured NOx signal, depending upon the instrumental background subtraction cycle employed. This interference has been noted previously, and indeed the effect has been used to measure both alkenes and ozone in the atmosphere. Here we report the results of a systematic investigation of the response of a selection of NOx analysers, ranging from systems used for routine air quality monitoring to atmospheric research instrumentation, to a series of alkenes ranging from ethene to the biogenic monoterpenes, as a function of conditions (co-reactants, humidity). Experiments were performed in the European Photoreactor (EUPHORE) to ensure common calibration, a common sample for the monitors, and to unequivocally confirm the alkene (via FTIR) and NO2 (via DOAS) levels present. The instrument responses ranged from negligible levels up to 10 % depending upon the alkene present and conditions used. Such interferences may be of substantial importance

  3. Light-driven biocatalytic reduction of α,β-unsaturated compounds by ene reductases employing transition metal complexes as photosensitizers† †Electronic supplementary information (ESI) available: Additional experimental sections, tables, figures and discussion. See DOI: 10.1039/c5cy01642h Click here for additional data file.

    PubMed Central

    Peers, Martyn K.; Toogood, Helen S.; Heyes, Derren J.; Mansell, David; Coe, Benjamin J.

    2016-01-01

    Efficient and cost effective nicotinamide cofactor regeneration is essential for industrial-scale bio-hydrogenations employing flavin-containing biocatalysts such as the Old Yellow Enzymes. A direct flavin regeneration system using visible light to initiate a photoredox cycle and drive biocatalysis is described, and shown to be effective in driving biocatalytic activated alkene reduction. Using Ru(ii) or Ir(iii) complexes as photosensitizers, coupled with an electron transfer mediator (methyl viologen) and sacrificial electron donor (triethanolamine) drives catalytic turnover of two Old Yellow Enzymes with multiple oxidative substrates. Therefore, there is great potential in the development of light-driven biocatalytic systems, providing an alternative to the reliance on enzyme-based cofactor regeneration systems. PMID:27019691

  4. Two Metals Are Better Than One in the Gold Catalyzed Oxidative Heteroarylation of Alkenes

    PubMed Central

    Tkatchouk, Ekaterina; Mankad, Neal P.; Benitez, Diego; Goddard, William A.; Toste, F. Dean

    2011-01-01

    We present a detailed study of the mechanism for oxidative heteroarylation, based on DFT calculations and experimental observations. We propose binuclear Au(II)-Au(II) complexes to be key intermediates in the mechanism for gold catalyzed oxidative heteroarylation. The reaction is thought to proceed via a gold redox cycle involving initial oxidation of Au(I) to binuclear Au(II)-Au(II) complexes by Selectfluor, followed by heteroauration and reductive elimination. While it is tempting to invoke a transmetalation/reductive elimination mechanism similar to that proposed for other transition metal complexes, experimental and DFT studies suggest that the key C-C bond forming reaction occurs via a bimolecular reductive elimination process (devoid of transmetalation). In addition, the stereochemistry of the elimination step was determined experimentally to proceed with complete retention. Ligand and halide effects played an important role in the development and optimization of the catalyst; our data provides an explanation for the ligand effects observed experimentally, useful for future catalyst development. Cyclic voltammetry data is presented that supports redox synergy of the Au···Au aurophilic interaction. The monometallic reductive elimination from mononuclear Au(III) complexes is also studied from which we can predict a ~15 kcal/mol advantage for bimetallic reductive elimination. PMID:21861448

  5. Copper-Catalyzed Oxidative Dehydrogenative Carboxylation of Unactivated Alkanes to Allylic Esters via Alkenes

    PubMed Central

    2015-01-01

    We report copper-catalyzed oxidative dehydrogenative carboxylation (ODC) of unactivated alkanes with various substituted benzoic acids to produce the corresponding allylic esters. Spectroscopic studies (EPR, UV–vis) revealed that the resting state of the catalyst is [(BPI)Cu(O2CPh)] (1-O2CPh), formed from [(BPI)Cu(PPh3)2], oxidant, and benzoic acid. Catalytic and stoichiometric reactions of 1-O2CPh with alkyl radicals and radical probes imply that C–H bond cleavage occurs by a tert-butoxy radical. In addition, the deuterium kinetic isotope effect from reactions of cyclohexane and d12-cyclohexane in separate vessels showed that the turnover-limiting step for the ODC of cyclohexane is C–H bond cleavage. To understand the origin of the difference in products formed from copper-catalyzed amidation and copper-catalyzed ODC, reactions of an alkyl radical with a series of copper–carboxylate, copper–amidate, and copper–imidate complexes were performed. The results of competition experiments revealed that the relative rate of reaction of alkyl radicals with the copper complexes follows the trend Cu(II)–amidate > Cu(II)–imidate > Cu(II)–benzoate. Consistent with this trend, Cu(II)–amidates and Cu(II)–benzoates containing more electron-rich aryl groups on the benzamidate and benzoate react faster with the alkyl radical than do those with more electron-poor aryl groups on these ligands to produce the corresponding products. These data on the ODC of cyclohexane led to preliminary investigation of copper-catalyzed oxidative dehydrogenative amination of cyclohexane to generate a mixture of N-alkyl and N-allylic products. PMID:25389772

  6. Selective oxidation of alkanes and/or alkenes to valuable oxygenates

    DOEpatents

    Lin, Manhua; Pillai, Krishnan S.

    2011-02-15

    A catalyst, its method of preparation and its use for producing at least one of methacrolein and methacrylic acid, for example, by subjecting isobutane or isobutylene or a mixture thereof to a vapor phase catalytic oxidation in the presence of air or oxygen. In the case where isobutane alone is subjected to a vapor phase catalytic oxidation in the presence of air or oxygen, the product is at least one of isobutylene, methacrolein and methacrylic acid. The catalyst comprises a compound having the formula A.sub.aB.sub.bX.sub.xY.sub.yZ.sub.zO.sub.o wherein A is one or more elements selected from the group of Mo, W and Zr, B is one or more elements selected from the group of Bi, Sb, Se, and Te, X is one or more elements selected from the group of Al, Bi, Ca, Ce, Co, Fe, Ga, Mg, Ni, Nb, Sn, W and Zn, Y is one or more elements selected from the group of Ag, Au, B, Cr, Cs, Cu, K, La, Li, Mg, Mn, Na, Nb, Ni, P, Pb, Rb, Re, Ru, Sn, Te, Ti, V and Zr, and Z is one or more element from the X or Y groups or from the following: As, Ba, Pd, Pt, Sr, or mixtures thereof, and wherein a=1, 0.05oxidation state of the other elements.

  7. Copper-catalyzed oxidative dehydrogenative carboxylation of unactivated alkanes to allylic esters via alkenes.

    PubMed

    Tran, Ba L; Driess, Matthias; Hartwig, John F

    2014-12-10

    We report copper-catalyzed oxidative dehydrogenative carboxylation (ODC) of unactivated alkanes with various substituted benzoic acids to produce the corresponding allylic esters. Spectroscopic studies (EPR, UV-vis) revealed that the resting state of the catalyst is [(BPI)Cu(O2CPh)] (1-O2CPh), formed from [(BPI)Cu(PPh3)2], oxidant, and benzoic acid. Catalytic and stoichiometric reactions of 1-O2CPh with alkyl radicals and radical probes imply that C-H bond cleavage occurs by a tert-butoxy radical. In addition, the deuterium kinetic isotope effect from reactions of cyclohexane and d12-cyclohexane in separate vessels showed that the turnover-limiting step for the ODC of cyclohexane is C-H bond cleavage. To understand the origin of the difference in products formed from copper-catalyzed amidation and copper-catalyzed ODC, reactions of an alkyl radical with a series of copper-carboxylate, copper-amidate, and copper-imidate complexes were performed. The results of competition experiments revealed that the relative rate of reaction of alkyl radicals with the copper complexes follows the trend Cu(II)-amidate > Cu(II)-imidate > Cu(II)-benzoate. Consistent with this trend, Cu(II)-amidates and Cu(II)-benzoates containing more electron-rich aryl groups on the benzamidate and benzoate react faster with the alkyl radical than do those with more electron-poor aryl groups on these ligands to produce the corresponding products. These data on the ODC of cyclohexane led to preliminary investigation of copper-catalyzed oxidative dehydrogenative amination of cyclohexane to generate a mixture of N-alkyl and N-allylic products. PMID:25389772

  8. Polar Addition to C=C Group: Why Is Anti-Markovnikov Hydroboration-Oxidation of Alkenes Not "Anti-"?

    ERIC Educational Resources Information Center

    Ilich, Predrag-Peter; Rickertsen, Lucas S.; Becker, Erienne

    2006-01-01

    For 137 years Markovnikov's rule has been extensively used in organic chemical education and research to describe the regioselectivity in electrophilic addition reactions to alkenes and alkynes. When the structures of the final reaction products are used as reference, the rule requests that certain polar addition reactions be termed…

  9. Biocatalytic portfolio of Basidiomycota.

    PubMed

    Schmidt-Dannert, Claudia

    2016-04-01

    Basidiomycota fungi have received little attention for applications in biocatalysis and biotechnology and remain greatly understudied despite their importance for carbon recycling, ecosystem functioning and medicinal properties. The steady influx of genome data has facilitated detailed studies aimed at understanding the evolution and function of fungal lignocellulose degradation. These studies and recent explorations into the secondary metabolomes have uncovered large portfolios of enzymes useful for biocatalysis and biosynthesis. This review will provide an overview of the biocatalytic repertoires of Basidiomycota characterized to date with the hope of motivation more research into the chemical toolkits of this diverse group of fungi. PMID:26812494

  10. Oxidation Numbers, Oxidants, and Redox Reactions: Variants of the Electrophilic Bromination of Alkenes and Variants of the Application of Oxone

    ERIC Educational Resources Information Center

    Eissen, Marco; Strudthoff, Merle; Backhaus, Solveig; Eismann, Carolin; Oetken, Gesa; Kaling, Soren; Lenoir, Dieter

    2011-01-01

    Oxidation-state and donor-acceptor concepts are important areas in the chemical education. Student worksheets containing problems that emphasize oxidation numbers, redox reactions of organic compounds, and stoichiometric reaction equations are presented. All of the examples are incorporated under one unifying topic: the production of vicinal…

  11. Electrochemical intramolecular aminooxygenation of unactivated alkenes.

    PubMed

    Xu, Fan; Zhu, Lin; Zhu, Shaobin; Yan, Xiaomei; Xu, Hai-Chao

    2014-09-26

    An electrochemical approach to the intramolecular aminooxygenation of unactivated alkenes has been developed. This process is based on the addition of nitrogen-centered radicals, generated through electrochemical oxidation, to alkenes followed by trapping of the cyclized radical intermediate with 2,2,6,6-tetramethylpiperidine-N-oxyl radical (TEMPO). Difunctionalization of a variety of alkenes with easily available carbamates/amides and TEMPO affords aminooxygenation products in high yields and with excellent trans selectivity for cyclic systems (d.r. up to>20:1). The approach provides a much-needed complementary route to existing cis-selective methods.

  12. The influence of immobilization and reduced water activity on gaseous-alkene oxidation by Mycobacterium PY1 and Xanthobacter PY2 in a gas-solid bioreactor.

    PubMed

    Hamstra, R S; Murris, M R; Tramper, J

    1987-05-01

    Immobilization of Mycobacterium PY1 and Xanthobacter PY2 in alginate and in or on hydroculture has a minor influence on the maximum rate of oxidation of propene and ethane. The apparent K(m) values of the immobilized cells are slightly higher than those of the free cells, indicating the presence of diffusion limitation in the immobilized systems. Both bacterial strains rapidly lose their alkene-oxidizing activity when the water activity is decreased. This decrease in activity is so rapid that most of the activity is lost already when the pores of the pertinent supports are still filled with water. Therefore, it is not possible with this system to study the transition of mass transfer of substrates entirely in the water phase to mass transfer to substrates entirely through the gas phase. PMID:18576533

  13. Impact of chamber wall loss of gaseous organic compounds on secondary organic aerosol formation: explicit modeling of SOA formation from alkane and alkene oxidation

    NASA Astrophysics Data System (ADS)

    La, Y. S.; Camredon, M.; Ziemann, P. J.; Valorso, R.; Matsunaga, A.; Lannuque, V.; Lee-Taylor, J.; Hodzic, A.; Madronich, S.; Aumont, B.

    2016-02-01

    Recent studies have shown that low volatility gas-phase species can be lost onto the smog chamber wall surfaces. Although this loss of organic vapors to walls could be substantial during experiments, its effect on secondary organic aerosol (SOA) formation has not been well characterized and quantified yet. Here the potential impact of chamber walls on the loss of gaseous organic species and SOA formation has been explored using the Generator for Explicit Chemistry and Kinetics of the Organics in the Atmosphere (GECKO-A) modeling tool, which explicitly represents SOA formation and gas-wall partitioning. The model was compared with 41 smog chamber experiments of SOA formation under OH oxidation of alkane and alkene series (linear, cyclic and C12-branched alkanes and terminal, internal and 2-methyl alkenes with 7 to 17 carbon atoms) under high NOx conditions. Simulated trends match observed trends within and between homologous series. The loss of organic vapors to the chamber walls is found to affect SOA yields as well as the composition of the gas and the particle phases. Simulated distributions of the species in various phases suggest that nitrates, hydroxynitrates and carbonylesters could substantially be lost onto walls. The extent of this process depends on the rate of gas-wall mass transfer, the vapor pressure of the species and the duration of the experiments. This work suggests that SOA yields inferred from chamber experiments could be underestimated up a factor of 2 due to the loss of organic vapors to chamber walls.

  14. Impact of chamber wall loss of gaseous organic compounds on secondary organic aerosol formation: explicit modeling of SOA formation from alkane and alkene oxidation

    NASA Astrophysics Data System (ADS)

    La, Y. S.; Camredon, M.; Ziemann, P. J.; Valorso, R.; Matsunaga, A.; Lannuque, V.; Lee-Taylor, J.; Hodzic, A.; Madronich, S.; Aumont, B.

    2015-09-01

    Recent studies have shown that low volatility gas-phase species can be lost onto the smog chamber wall surfaces. Although this loss of organic vapors to walls could be substantial during experiments, its effect on secondary organic aerosol (SOA) formation has not been well characterized and quantified yet. Here the potential impact of chamber walls on the loss of gaseous organic species and SOA formation has been explored using the Generator for Explicit Chemistry and Kinetics of the Organics in the Atmosphere (GECKO-A) modeling tool which explicitly represents SOA formation and gas/wall partitioning. The model was compared with 41 smog chamber experiments of SOA formation under OH oxidation of alkane and alkene series (linear, cyclic and C12-branched alkanes and terminal, internal and 2-methyl alkenes with 7 to 17 carbon atoms) under high NOx conditions. Simulated trends match observed trends within and between homologous series. The loss of organic vapors to the chamber walls is found to affect SOA yields as well as the composition of the gas and the particle phases. Simulated distributions of the species in various phases suggest that nitrates, hydroxynitrates and carbonylesters could substantially be lost onto walls. The extent of this process depends on the rate of gas/wall mass transfer, the vapor pressure of the species and the duration of the experiments. This work suggests that SOA yields inferred from chamber experiments could be underestimated up to 0.35 yield unit due to the loss of organic vapors to chamber walls.

  15. Biocatalytic material comprising multilayer enzyme coated fiber

    DOEpatents

    Kim, Jungbae [Richland, WA; Kwak, Ja Hun [Richland, WA; Grate, Jay W [West Richland, WA

    2009-11-03

    The present invention relates generally to high stability, high activity biocatalytic materials and processes for using the same. The materials comprise enzyme aggregate coatings having high biocatalytic activity and stability useful in heterogeneous environment. These new materials provide a new biocatalytic immobilized enzyme system with applications in bioconversion, bioremediation, biosensors, and biofuel cells.

  16. Impact of chamber wall loss of gaseous organic compounds on secondary organic aerosol formation: Explicit modeling of SOA formation from alkane and alkene oxidation

    DOE PAGESBeta

    La, Y. S.; Camredon, M.; Ziemann, P. J.; Valorso, R.; Matsunaga, A.; Lannuque, V.; Lee-Taylor, J.; Hodzic, A.; Madronich, S.; Aumont, B.

    2016-02-08

    Recent studies have shown that low volatility gas-phase species can be lost onto the smog chamber wall surfaces. Although this loss of organic vapors to walls could be substantial during experiments, its effect on secondary organic aerosol (SOA) formation has not been well characterized and quantified yet. Here the potential impact of chamber walls on the loss of gaseous organic species and SOA formation has been explored using the Generator for Explicit Chemistry and Kinetics of the Organics in the Atmosphere (GECKO-A) modeling tool, which explicitly represents SOA formation and gas–wall partitioning. The model was compared with 41 smog chambermore » experiments of SOA formation under OH oxidation of alkane and alkene series (linear, cyclic and C12-branched alkanes and terminal, internal and 2-methyl alkenes with 7 to 17 carbon atoms) under high NOx conditions. Simulated trends match observed trends within and between homologous series. The loss of organic vapors to the chamber walls is found to affect SOA yields as well as the composition of the gas and the particle phases. Simulated distributions of the species in various phases suggest that nitrates, hydroxynitrates and carbonylesters could substantially be lost onto walls. The extent of this process depends on the rate of gas–wall mass transfer, the vapor pressure of the species and the duration of the experiments. Furthermore, this work suggests that SOA yields inferred from chamber experiments could be underestimated up a factor of 2 due to the loss of organic vapors to chamber walls.« less

  17. cis-1,2-Aminohydroxylation of Alkenes Involving a Catalytic Cycle of Osmium(III) and Osmium(V) Centers: Os(V)(O)(NHTs) Active Oxidant with a Macrocyclic Tetradentate Ligand.

    PubMed

    Sugimoto, Hideki; Mikami, Akine; Kai, Kenichiro; Sajith, P K; Shiota, Yoshihito; Yoshizawa, Kazunari; Asano, Kaori; Suzuki, Takeyuki; Itoh, Shinobu

    2015-07-20

    Catalytic activity of [Os(III)(OH)(H2O)(L-N4Me2)](PF6)2 (1: L-N4Me2 = N,N'-dimethyl-2,11-diaza-[3,3](2,6)pyridinophane) in 1,2-cis-aminohydroxylation of alkenes with sodium N-chloro-4-methylbenzenesulfonamide (chloramine-T) is explored. Simple alkenes as well as those containing several types of substituents are converted to the corresponding 1,2-aminoalcohols in modest to high yields. The aminoalcohol products have exclusively cis conformation with respect to the introduced -OH and -NHTs groups. The spectroscopic measurements including cold mass spectroscopic study of the reaction product of complex 1 and chloromine-T as well as density functional theory (DFT) calculations indicate that an oxido-aminato-osmium(V) species [Os(V)(O)(NHTs)(L-N4Me2)](PF6)2 (2) is an active oxidant for the aminohydroxylation. The DFT calculations further indicate that the reaction involves a [3 + 2] cycloaddition between 2 and alkene, and the regioselectivity in the aminohydroxylation of unsymmetrical alkenes is determined by the orientation that bears less steric hindrance from the tosylamino group, which leads to the energetically more preferred product isomer.

  18. cis-1,2-Aminohydroxylation of Alkenes Involving a Catalytic Cycle of Osmium(III) and Osmium(V) Centers: Os(V)(O)(NHTs) Active Oxidant with a Macrocyclic Tetradentate Ligand.

    PubMed

    Sugimoto, Hideki; Mikami, Akine; Kai, Kenichiro; Sajith, P K; Shiota, Yoshihito; Yoshizawa, Kazunari; Asano, Kaori; Suzuki, Takeyuki; Itoh, Shinobu

    2015-07-20

    Catalytic activity of [Os(III)(OH)(H2O)(L-N4Me2)](PF6)2 (1: L-N4Me2 = N,N'-dimethyl-2,11-diaza-[3,3](2,6)pyridinophane) in 1,2-cis-aminohydroxylation of alkenes with sodium N-chloro-4-methylbenzenesulfonamide (chloramine-T) is explored. Simple alkenes as well as those containing several types of substituents are converted to the corresponding 1,2-aminoalcohols in modest to high yields. The aminoalcohol products have exclusively cis conformation with respect to the introduced -OH and -NHTs groups. The spectroscopic measurements including cold mass spectroscopic study of the reaction product of complex 1 and chloromine-T as well as density functional theory (DFT) calculations indicate that an oxido-aminato-osmium(V) species [Os(V)(O)(NHTs)(L-N4Me2)](PF6)2 (2) is an active oxidant for the aminohydroxylation. The DFT calculations further indicate that the reaction involves a [3 + 2] cycloaddition between 2 and alkene, and the regioselectivity in the aminohydroxylation of unsymmetrical alkenes is determined by the orientation that bears less steric hindrance from the tosylamino group, which leads to the energetically more preferred product isomer. PMID:26126185

  19. Ozonolysis of surface-adsorbed methoxyphenols: kinetics of aromatic ring cleavage vs. alkene side-chain oxidation

    NASA Astrophysics Data System (ADS)

    O'Neill, E. M.; Kawam, A. Z.; Van Ry, D. A.; Hinrichs, R. Z.

    2014-01-01

    Lignin pyrolysis products, which include a variety of substituted methoxyphenols, constitute a major component of organics released by biomass combustion, and may play a central role in the formation of atmospheric brown carbon. Understanding the atmospheric fate of these compounds upon exposure to trace gases is therefore critical to predicting the chemical and physical properties of biomass burning aerosol. We used diffuse reflectance infrared spectroscopy to monitor the heterogeneous ozonolysis of 4-propylguaiacol, eugenol, and isoeugenol adsorbed on NaCl and α-Al2O3 substrates. Adsorption of gaseous methoxyphenols onto these substrates produced near-monolayer surface concentrations of 3 × 1018 molecules m-2. The subsequent dark heterogeneous ozonolysis of adsorbed 4-propylguaiacol cleaved the aromatic ring between the methoxy and phenol groups with the product conclusively identified by GC-MS and 1H-NMR. Kinetic analysis of eugenol and isoeugenol dark ozonolysis also suggested the formation of ring-cleaved products, although ozonolysis of the unsaturated substituent groups forming carboxylic acids and aldehydes was an order of magnitude faster. Average uptake coefficients for NaCl-adsorbed methoxyphenols were γ = 2.3 (± 0.8) × 10-7 and 2 (± 1) × 10-6 for ozonolysis of the aromatic ring and the unsaturated side chain, respectively, and reactions on α-Al2O3 were approximately two times slower. UV-visible radiation (λ > 300 nm) enhanced eugenol ozonolysis of the aromatic ring by a factor of 4(± 1) but had no effect on ozonolysis of the alkene side chain.

  20. Bioorganometallic chemistry: biocatalytic oxidation reactions with biomimetic nad+/nadh co-factors and [cp*rh(bpy)h]+ for selective organic synthesis

    SciTech Connect

    Lutz, Jochen; Hollman, Frank; Ho, The Vinh; Schnyder, Adrian; Fish, Richard H.; Schmid, Andreas

    2004-03-09

    The biocatalytic, regioselective hydroxylation of 2-hydroxybiphenyl to the corresponding catechol was accomplished utilizing the monooxygenase 2-hydroxybiphenyl 3-monooxygenase (HbpA). The necessary natural nicotinamide adenine dinucleotide (NAD{sup +}) co-factor for this biocatalytic process was replaced by a biomimetic co-factor, N-benzylnicotinamide bromide, 1a. The interaction between the flavin (FAD) containing HbpA enzyme and the corresponding biomimetic NADH compound, N-benzyl-1,4-dihdronicotinamide, 1b, for hydride transfers, was shown to readily occur. The in situ recycling of the reduced NADH biomimic 1b from 1a was accomplished with [Cp*Rh(bpy)H](Cl); however, productive coupling of this regeneration reaction to the enzymatic hydroxylation reaction was not totally successful, due to a deactivation process concerning the HbpA enzyme peripheral groups; i.e., -SH or -NH{sub 2} possibly reacting with the precatalyst, [Cp*Rh(bpy)(H{sub 2}O)](Cl){sub 2}, and thus inhibiting the co-factor regeneration process. The deactivation mechanism was studied, and a promising strategy of derivatizing these peripheral -SH or -NH{sub 2} groups with a polymer containing epoxide was successful in circumventing the undesired interaction between HbpA and the precatalyst. This latter strategy allowed tandem co-factor regeneration using 1a or 2a, [Cp*Rh(bpy)(H2O)](Cl){sub 2}, and formate ion, in conjunction with the polymer bound, FAD containing HbpA enzyme to provide the catechol product.

  1. Copper-Catalyzed Oxyboration of Unactivated Alkenes.

    PubMed

    Itoh, Taisuke; Matsueda, Takumi; Shimizu, Yohei; Kanai, Motomu

    2015-11-01

    The first regiodivergent oxyboration of unactivated terminal alkenes is reported, using copper alkoxide as a catalyst, bis(pinacolato)diboron [(Bpin)2 ] as a boron source, and (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) as an oxygen source. The reaction is compatible with various functional groups. Two regioisomers are selectively produced by selecting the appropriate ligands on copper. The products may be used as a linchpin precursor for various other functionalizations, and net processes such as carbooxygenation, aminooxygenation, and dioxygenation of alkenes can be achieved after C-B bond transformations. Mechanistic studies indicate that the reaction involves the following steps: 1) Transmetalation between CuOtBu and (Bpin)2 to generate a borylcopper species; 2) regiodivergent borylcupration of alkenes; 3) oxidation of the thus-generated C-Cu bond to give an alkyl radical; 4) trapping of the resulting alkyl radical by TEMPO. PMID:26376774

  2. Intermolecular Hydropyridylation of Unactivated Alkenes.

    PubMed

    Ma, Xiaoshen; Herzon, Seth B

    2016-07-20

    A general method for the hydropyridylation of unactivated alkenes is described. The transformation connects metal-mediated hydrogen atom transfer to alkenes and Minisci addition reactions. The reaction proceeds under mild conditions with high site-selectivities and allows for the construction of tertiary and quaternary centers from simple alkene starting materials. PMID:27384921

  3. Synthesis and Application of Chiral Spiro Cp Ligands in Rhodium-Catalyzed Asymmetric Oxidative Coupling of Biaryl Compounds with Alkenes.

    PubMed

    Zheng, Jun; Cui, Wen-Jun; Zheng, Chao; You, Shu-Li

    2016-04-27

    The vastly increasing application of chiral Cp ligands in asymmetric catalysis results in growing demand for novel chiral Cp ligands. Herein, we report a new class of chiral Cp ligands based on 1,1'-spirobiindane, a privileged scaffold for chiral ligands and catalysts. The corresponding Rh complexes are shown to be excellent catalysts in asymmetric oxidative coupling reactions, providing axially chiral biaryls in 19-97% yields with up to 98:2 er.

  4. The Biocatalytic Desulfurization Project

    SciTech Connect

    David Nunn; James Boltz; Philip M. DiGrazia; Larry Nace

    2006-03-03

    The material in this report summarizes the Diversa technical effort in development of a biocatalyst for the biodesulfurization of Petro Star diesel as well as an economic report of standalone and combined desulfurization options, prepared by Pelorus and Anvil, to support and inform the development of a commercially viable process. We will discuss goals of the projected as originally stated and their modification as guided by parallel efforts to evaluate commercialization economics and process parameters. We describe efforts to identify novel genes and hosts for the generation of an optimal biocatalyst, analysis of diesel fuels (untreated, chemically oxidized and hydrotreated) for organosulfur compound composition and directed evolution of enzymes central to the biodesulfurization pathway to optimize properties important for their use in a biocatalyst. Finally we will summarize the challenges and issues that are central to successful development of a viable biodesulfurization process.

  5. THE BIOCATALYTIC DESULFURIZATION PROJECT

    SciTech Connect

    Steven E. Bonde; David Nunn

    2003-04-01

    Research activities in the second quarter have largely been a continuation of efforts previously described in the first quarterly report as well as a degree of redirection of effort as a result of discussions during the first quarterly meeting held in San Diego. Chemical synthesis efforts have been refined and are currently being used to support generation of substrates for evaluation and evolution of enzymes for their oxidation. Analysis of the sulfur species in Petro Star diesel, CED extract and refinement of the speciation data is nearly complete. Molecular biology efforts continue with the cloning, expression and characterization of the DszA and DszC proteins as well as the flavin reductases to support regeneration of the essential FMN cofactors. In addition, we have initiated an evolution effort for the extension and improvement of DszA enzyme activity using Diversa's Gene Site Saturation Mutagenesis (GSSM{trademark}) technology. To support the evolution effort as well as of characterization of enzyme activities on a variety of substrates, a high-throughput mass spectroscopy-based assay has been developed. Two selection/screen strategies for the discovery and evolution of biocatalyst enzyme have been developed and are being evaluated for performance using gene libraries constructed from known biodesulfurization strains and environmental libraries.

  6. THE BIOCATALYTIC DESULFURIZATION PROJECT

    SciTech Connect

    Steven E. Bonde; David Nunn

    2003-01-01

    During the first quarter of the Biological Desulfurization project several activities were pursued. A project kickoff meeting was held at the Diversa facility in San Diego, CA. Activities that were in process before the meeting and begun afterwards by Diversa Corporation and Petro Star Inc. include: Technology transfer in the form of information generated by Enchira to Diversa, the purchase and installation of equipment by Diversa, development of synthetic methods and preparation of organo-sulfur substrates for use in determining enzyme activities, production of extract via Petro Star's CED process, detailed analysis of Petro Star Inc. diesel and CED extract, and several activities in molecular biology. Diversa Corporation, in the area of molecular biology, engaged in several activities in support of the task list of the contract. These included: construction of a genomic library; development and utilization of a sequence-based gene discovery effort; a parallel discovery approach based on functional expression of enzymes with the ability to oxidize organosulfur compounds. Biodesulfurization genes have already been identified and are being sequenced and subcloned for expression in heterologous biological hosts. Diversa has evaluated and adapted assays developed by Enchira used to assess the activities of DBT and DBTO{sub 2} monooxygenases. Finally, Diversa personnel have developed two novel selection/screen strategies for the improvement of biocatalyst strains by directed evolution.

  7. Methods of producing epoxides from alkenes using a two-component catalyst system

    DOEpatents

    Kung, Mayfair C.; Kung, Harold H.; Jiang, Jian

    2013-07-09

    Methods for the epoxidation of alkenes are provided. The methods include the steps of exposing the alkene to a two-component catalyst system in an aqueous solution in the presence of carbon monoxide and molecular oxygen under conditions in which the alkene is epoxidized. The two-component catalyst system comprises a first catalyst that generates peroxides or peroxy intermediates during oxidation of CO with molecular oxygen and a second catalyst that catalyzes the epoxidation of the alkene using the peroxides or peroxy intermediates. A catalyst system composed of particles of suspended gold and titanium silicalite is one example of a suitable two-component catalyst system.

  8. Catalytic, stereospecific syn-dichlorination of alkenes

    NASA Astrophysics Data System (ADS)

    Cresswell, Alexander J.; Eey, Stanley T.-C.; Denmark, Scott E.

    2015-02-01

    As some of the oldest organic chemical reactions known, the ionic additions of elemental halogens such as bromine and chlorine to alkenes are prototypical examples of stereospecific reactions, typically delivering vicinal dihalides resulting from anti-addition. Although the invention of enantioselective variants is an ongoing challenge, the ability to overturn the intrinsic anti-diastereospecificity of these transformations is also a largely unsolved problem. Here, we describe the first catalytic, syn-stereospecific dichlorination of alkenes, employing a group transfer catalyst based on a redox-active main group element (selenium). With diphenyl diselenide (PhSeSePh) (5 mol%) as the pre-catalyst, benzyltriethylammonium chloride (BnEt3NCl) as the chloride source and an N-fluoropyridinium salt as the oxidant, a wide variety of functionalized cyclic and acyclic 1,2-disubstituted alkenes, including simple allylic alcohols, deliver syn-dichlorides with exquisite stereocontrol. This methodology is expected to find applications in streamlining the synthesis of polychlorinated natural products such as the chlorosulfolipids.

  9. Catalytic, Stereospecific Syn-Dichlorination of Alkenes

    PubMed Central

    Cresswell, Alexander J.; Eey, Stanley T.-C.; Denmark, Scott E.

    2015-01-01

    As some of the oldest organic chemical reactions known, the ionic additions of elemental halogens such as bromine and chlorine to alkenes are prototypical examples of stereospecific reactions, typically delivering vicinal dihalides resulting from anti-addition. Whilst the invention of enantioselective variants is an ongoing challenge, the ability to overturn the intrinsic anti-diastereospecificity of these transformations is also a largely unsolved problem. In this Article, we describe the first catalytic, syn-stereospecific dichlorination of alkenes, employing a group transfer catalyst based on a redox-active main group element (i.e., selenium). Thus, with diphenyl diselenide (PhSeSePh) (5 mol %) as the pre-catalyst, benzyltriethylammonium chloride (BnEt3NCl) as the chloride source, and an N-fluoropyridinium salt as the oxidant, a wide variety of functionalized cyclic and acyclic 1,2-disubstituted alkenes, including simple allylic alcohols, deliver syn-dichlorides with exquisite stereocontrol. This methodology is expected to find applications in streamlining the synthesis of polychlorinated natural products such as the chlorosulfolipids. PMID:25615668

  10. Intensification of biocatalytical processes by synergistic substrate conversion. Fungal peroxidase catalyzed N-hydroxy derivative oxidation in presence of 10-propyl sulfonic acid phenoxazine.

    PubMed

    Kulys, Juozas; Dapkunas, Zilvinas; Stupak, Robert

    2009-08-01

    Many industrial pollutants, xenobiotics, and industry-important compounds are known to be oxidized by peroxidases. It has been shown that highly efficient peroxidase substrates are able to enhance the oxidation of low reactive substrate by acting as mediators. To explore this effect, the oxidation of two N-hydroxy derivatives, i.e., N-hydroxy-N-phenyl-acetamide (HPA) and N-hydroxy-N-phenyl-carbamic acid methyl ester (HPCM) catalyzed by recombinant Coprinus cinereus (rCiP) peroxidase has been studied in presence of efficient substrate 3-(4a,10a-dihydro- phenoxazin-10-yl)-propane-1-sulfonic acid (PPSA) at pH 8.5. The bimolecular constant of PPSA cation radical reaction with HPA was estimated to be (2.5 +/- 0.2).10(7) M(-1) s(-1) and for HPCM was even higher. The kinetic measurements show that rCiP-catalyzed oxidation of HPA and HPCM can increase up to 33,000 times and 5,500 times in the presence of equivalent concentration of high reactive substrate PPSA. The mathematical model of synergistic rCiP-catalyzed HPA-PPSA and HPCM-PPSA oxidation was proposed. Experimentally obtained rate constants were in good agreement with those calculated from the model confirming the synergistic scheme of the substrate oxidation. In order to explain the different reactivity of substrates, the docking of substrates in the active site of the enzyme was calculated. Molecular dynamic calculations show that the enzyme-substrate complexes are structurally stable. The high reactive PPSA exhibited higher affinity to enzyme active site than HPA and HPCM. Furthermore, the orientation of HPA and HPCM was not favorable for proton transfer to the distal histidine, and different substrate reactivity was explained by these diversities.

  11. Studies on reactions of ozone with alkenes.

    PubMed

    Protczak, Agnieszka; Trzeszczynski, Jerzy

    2002-01-01

    In the last years, a continuous increase of the O3 concentration has been recorded in the lower atmospheric layers. Photochemical reactions with NO(x), CO and organic compounds are the main sources of O3 in the troposphere. In this work, an attempt was made to determine the impact of alkenes on the O3 concentration in the troposphere. A study on the gas-phase reactions of 03 with 1-hexene, 1-heptene and 1-nonene was made. The reactions were carried out at room temperature under atmospheric pressure. Ozone was formed by the ultraviolet radiation emitted by a mercury lamp, in order to simulate the atmospheric conditions. The changes with time in the concentration of O3, 1-alkenes and formed aldehydes were investigated. Qualitative and quantitative analyses were done by means of the gas chromatography and colorimetry. The following products were identified: pentanal from 1-hexene; hexanal from 1-heptene; oktanal from 1-nonene. For each of the reactions, HCHO was also determined as a product. The reaction rate constants were calculated and obtained in units of 10(-17) cm(-3) molecule(-1) s(-1): 1.94-0.99 for 1-hexene, 5.54-4.51 for 1-heptene and 1.54-0.76 for 1-nonene. Based on the results obtained, an explanation of O3 concentration variations in the planetary boundary layer can be given. Last year a considerable increase of O3 concentration on the roads of Western Europe was recorded. This increase could have resulted from the decrease of alkene concentration in the air due to common use of the catalytic converters in cars. The unsaturated hydrocarbons rapidly oxidize on the catalyst. In Eastern Europe, where the amount of cars equipped with catalytic converters is smaller than in Western Europe, the alkene content in the exhaust fumes results in a decrease of the O3 concentration in the troposphere.

  12. Degradation of Hydrocarbons by Members of the Genus Candida II. Oxidation of n-Alkanes and 1-Alkenes by Candida lipolytica

    PubMed Central

    Klug, M. J.; Markovetz, A. J.

    1967-01-01

    Candida lipolytica ATCC 8661 was grown in a mineral-salts hydrocarbon medium. n-Alkanes and 1-alkenes with 14 through 18 carbon atoms were used as substrates. Ether extracts of culture fluids and cells obtained from cultures grown on the various substrates were analyzed by thin-layer and gas-liquid chromatography. Analyses of fluids from cultures grown on n-alkanes indicated a predominance of fatty acids and alcohols of the same chain length as the substrate. In addition, numerous other fatty acids and alcohols were present. Analyses of saponifiable and nonsaponifiable material obtained from the cells revealed essentially the same products. The presence of primary and secondary alcohols, as well as fatty acids, of the same chain length as the n-alkane substrate suggested that attack on both the methyl and α-methylene group was occurring. The significance of these two mechanisms in the degradation of n-alkanes by this organism was not evident from the data presented. Analyses of fluids from cultures grown on 1-alkenes indicated the presence of 1,2-diols, as well as ω-unsaturated fatty acids, of the same chain length as the substrate. Alcohols present were all unsaturated. Saponifiable and nonsaponifiable material obtained from cells contained essentially the same products. The presence of 1,2-diols and ω-unsaturated fatty acids of the same chain length as the substrate from cultures grown on 1-alkenes indicated that both the terminal methyl group and the terminal double bond were being attacked. PMID:6025303

  13. Microanalysis of Alkenes by Ozonolysis

    ERIC Educational Resources Information Center

    Luibrand, R. T.; Vollmer, J. J.

    1975-01-01

    Describes an undergraduate laboratory experiment in which the position of the double bond in an alkene is determined by identifying its ozonolysis products. This experiment can also be used to introduce the technique of gas chromatography. (MLH)

  14. The arene–alkene photocycloaddition

    PubMed Central

    Streit, Ursula

    2011-01-01

    Summary In the presence of an alkene, three different modes of photocycloaddition with benzene derivatives can occur; the [2 + 2] or ortho, the [3 + 2] or meta, and the [4 + 2] or para photocycloaddition. This short review aims to demonstrate the synthetic power of these photocycloadditions. PMID:21647263

  15. Biogenic Emissions of Light Alkenes from a Coniferous Forest

    NASA Astrophysics Data System (ADS)

    Rhew, R. C.; Turnipseed, A. A.; Martinez, L.; Shen, S.; De Gouw, J. A.; Warneke, C.; Koss, A.; Lerner, B. M.; Miller, B. R.; Smith, J. N.; Guenther, A. B.

    2014-12-01

    Alkenes are reactive hydrocarbons that play important roles in the photochemical production of tropospheric ozone and in the formation of secondary organic aerosols. The light alkenes (C2-C4) originate from both biogenic and anthropogenic sources and include C2H4 (ethene), C3H6 (propene) and C4H8 (1-butene, 2-butene, 2-methylpropene). Light alkenes are used widely as chemical feedstocks because their double bond makes them versatile for industrial reactions. Their biogenic sources are poorly characterized, with most global emissions estimates relying on laboratory-based studies; net ecosystem emissions have been measured at only one site thus far. Here we report net ecosystem fluxes of light alkenes and isoprene from a semi-arid ponderosa pine forest in the Rocky Mountains of Colorado, USA. Canopy scale fluxes were measured using relaxed eddy accumulation (REA) techniques on the 28-meter NCAR tower in the Manitou Experimental Forest Observatory. Updrafts and downdrafts were determined by sonic anemometry and segregated into 'up' and 'down' reservoirs over the course of an hour. Samples were then measured on two separate automated gas chromatographs (GCs). The first GC measured light hydrocarbons (C2-C6 alkanes and C2-C5 alkenes) by flame ionization detection (FID). The second GC measured halocarbons (methyl chloride, CFC-12, and HCFC-22) by electron capture detection (ECD). Additional air measurements from the top of the tower included hydrocarbons and their oxidation products by Proton Transfer Reaction Mass Spectrometry (PTR-MS). Three field intensives were conducted during the summer of 2014. The REA flux measurements showed that ethene, propene and the butene emissions have significant diurnal cycles, with maximum emissions at midday. The light alkenes contribute significantly to the overall biogenic source of reactive hydrocarbons and have a temporal variability that may be associated with physical and biological parameters. These ecosystem scale measurements

  16. The Industrial Age of Biocatalytic Transamination

    PubMed Central

    Fuchs, Michael; Farnberger, Judith E; Kroutil, Wolfgang

    2015-01-01

    During the last decade the use of ω-transaminases has been identified as a very powerful method for the preparation of optically pure amines from the corresponding ketones. Their immense potential for the preparation of chiral amines, together with their ease of use in combination with existing biocatalytic methods, have made these biocatalysts a competitor to any chemical methodology for (asymmetric) amination. An increasing number of examples, especially from industry, shows that this biocatalytic technology outmaneuvers existing chemical processes by its simple and flexible nature. In the last few years numerous publications and patents on synthetic routes, mainly to pharmaceuticals, involving ω-transaminases have been published. The review gives an overview of the application of ω-transaminases in organic synthesis with a focus on active pharmaceutical ingredients (APIs) and the developments during the last few years. PMID:26726292

  17. An ene reductase from Clavispora lusitaniae for asymmetric reduction of activated alkenes.

    PubMed

    Ni, Yan; Yu, Hui-Lei; Lin, Guo-Qiang; Xu, Jian-He

    2014-03-01

    A putative ene reductase gene from Clavispora lusitaniae was heterologously overexpressed in Escherichia coli, and the encoded protein (ClER) was purified and characterized for its biocatalytic properties. This NADPH-dependent flavoprotein was identified with reduction activities toward a diverse range of activated alkenes including conjugated enones, enals, maleimide derivative and α,β-unsaturated carboxylic esters. The purified ClER exhibited a relatively high activity of 7.3 U mg(prot)⁻¹ for ketoisophorone while a remarkable catalytic efficiency (k(cat)/K(m)=810 s⁻¹ mM⁻¹) was obtained for 2-methyl-cinnamaldehyde due to the high affinity. A series of prochiral activated alkenes were stereoselectively reduced by ClER furnishing the corresponding saturated products in up to 99% ee. The practical applicability of ClER was further evaluated for the production of (R)-levodione, a valuable chiral compound, from ketoisophorone. Using the crude enzyme of ClER and glucose dehydrogenase (GDH), 500 mM of ketoisophorone was efficiently converted to (R)-levodione with excellent stereoselectivity (98% ee) within 1h. All these positive features demonstrate a high synthetic potential of ClER in the asymmetric reduction of activated alkenes. PMID:24564901

  18. Efficient Biocatalytic Synthesis of Chiral Chemicals.

    PubMed

    Zhang, Zhi-Jun; Pan, Jiang; Ma, Bao-Di; Xu, Jian-He

    2016-01-01

    Chiral chemicals are a group of important chiral synthons for the synthesis of a series of pharmaceuticals, agrochemicals, and fine chemicals. In past decades, a number of biocatalytic approaches have been developed for the green and effective synthesis of various chiral chemicals. However, the practical application of these biocatalytic processes is still hindered by the lack of highly efficient and robust biocatalysts, which usually results in the low volumetric productivity and high cost of the bioprocesses. Further step forward of biocatalysis in industrial application strongly requires the development of versatile and highly efficient biocatalysts, aiming to increase the process efficiency and facilitate the downstream processing. Recently, the fast growth of genome sequences in the database in post-genomic era offers great opportunities for accessing numerous biocatalysts with practical application potential, and the so-called genome mining approach provides time-effective and highly specific strategy for the fast identification of target enzymes with desired properties and outperforms the traditional screening of soil samples for microbial enzyme producers of interest. A number of biocatalytic processes with industrial application potential were developed thereafter. Further development of protein engineering strategies, process optimization, and cooperative work between biologists, organic chemists, and engineers is expected to make biocatalysis technology the first choice approach for the eco-friendly, highly efficient, and cost-effective synthesis of chiral chemicals in the near future.

  19. 2-Alkenal-scavenging ability of m-diphenols.

    PubMed

    Hidalgo, Francisco J; Zamora, Rosario

    2014-10-01

    The reaction between m-diphenols (resorcinol, 2-methylresorcinol, 2,5-dimethylresorcinol, 3-methylphenol, orcinol, and phloroglucinol) and 2-alkenals (2-pentenal and 2-octenal) was studied in an attempt to understand the chemical pathways involved in the scavenging ability of m-diphenols for the 2-alkenals produced as a consequence of lipid oxidation. Phenols reacted chemically with 2-alkenals producing a number of 2H-chromenols, chromandiols, chromanols, and dihydropyrano[3,2-g]chromenes, which were isolated and identified by 1D and 2D nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS). The identification of all these compounds resulted in the construction of a general pathway for these reactions. These results confirm that the 2-alkenal-scavenging ability of m-diphenols is a consequence of their structure. This is a complex reaction in which many different products are formed. The most stable products were the chromandiols. However, the main reaction products were the 2H-chromenols. These products were unstable and disappeared as a consequence of polymerisation and browning reactions. PMID:24799217

  20. Rhodium-catalysed syn-carboamination of alkenes via a transient directing group.

    PubMed

    Piou, Tiffany; Rovis, Tomislav

    2015-11-01

    Alkenes are the most ubiquitous prochiral functional groups--those that can be converted from achiral to chiral in a single step--that are accessible to synthetic chemists. For this reason, difunctionalization reactions of alkenes (whereby two functional groups are added to the same double bond) are particularly important, as they can be used to produce highly complex molecular architectures. Stereoselective oxidation reactions, including dihydroxylation, aminohydroxylation and halogenation, are well established methods for functionalizing alkenes. However, the intermolecular incorporation of both carbon- and nitrogen-based functionalities stereoselectively across an alkene has not been reported. Here we describe the rhodium-catalysed carboamination of alkenes at the same (syn) face of a double bond, initiated by a carbon-hydrogen activation event that uses enoxyphthalimides as the source of both the carbon and the nitrogen functionalities. The reaction methodology allows for the intermolecular, stereospecific formation of one carbon-carbon and one carbon-nitrogen bond across an alkene, which is, to our knowledge, unprecedented. The reaction design involves the in situ generation of a bidentate directing group and the use of a new cyclopentadienyl ligand to control the reactivity of rhodium. The results provide a new way of synthesizing functionalized alkenes, and should lead to the convergent and stereoselective assembly of amine-containing acyclic molecules.

  1. Nickel-Catalyzed Coupling Reactions of Alkenes

    PubMed Central

    Ng, Sze-Sze; Ho, Chun-Yu; Schleicher, Kristin D.; Jamison, Timothy F.

    2011-01-01

    Several reactions of simple, unactivated alkenes with electrophiles under nickel(0) catalysis are discussed. The coupling of olefins with aldehydes and silyl triflates provides allylic or homoallylic alcohol derivatives, depending on the supporting ligands and, to a lesser extent, the substrates employed. Reaction of alkenes with isocyanates yields N-alkyl acrylamides. In these methods, alkenes act as the functional equivalents of alkenyl- and allylmetal reagents. PMID:21814295

  2. Catalytic Enantioselective Functionalization of Unactivated Terminal Alkenes.

    PubMed

    Coombs, John R; Morken, James P

    2016-02-18

    Terminal alkenes are readily available functional groups which appear in α-olefins produced by the chemical industry, and they appear in the products of many contemporary synthetic reactions. While the organic transformations that apply to alkenes are amongst the most studied reactions in all of chemical synthesis, the number of reactions that apply to nonactivated terminal alkenes in a catalytic enantioselective fashion is small in number. This Minireview highlights the cases where stereocontrol in catalytic reactions of 1-alkenes is high enough to be useful for asymmetric synthesis. PMID:26764019

  3. Catalytic Enantioselective Functionalization of Unactivated Terminal Alkenes.

    PubMed

    Coombs, John R; Morken, James P

    2016-02-18

    Terminal alkenes are readily available functional groups which appear in α-olefins produced by the chemical industry, and they appear in the products of many contemporary synthetic reactions. While the organic transformations that apply to alkenes are amongst the most studied reactions in all of chemical synthesis, the number of reactions that apply to nonactivated terminal alkenes in a catalytic enantioselective fashion is small in number. This Minireview highlights the cases where stereocontrol in catalytic reactions of 1-alkenes is high enough to be useful for asymmetric synthesis.

  4. Passerini Reactions on Biocatalytically Derived Chiral Azetidines.

    PubMed

    Moni, Lisa; Banfi, Luca; Basso, Andrea; Bozzano, Andrea; Spallarossa, Martina; Wessjohann, Ludger; Riva, Renata

    2016-01-01

    The purpose of this study was to explore a series of Passerini reactions on a biocatalytically derived enantiopure azetidine-2-carboxyaldehyde in order to obtain, in a diastereoselective manner, polyfunctionalised derivatives having the potential to be cyclized to chiral bridged bicyclic nitrogen heterocycles. While diastereoselectivity was poor under classical Passerini conditions, a significant increase of diastereoselectivity (up to 76:24) was gained by the use of zinc bromide as promoter. The methodology has a broad scope and yields are always good. PMID:27589709

  5. Biocatalytic Pathway Selection in Transient Tripeptide Nanostructures.

    PubMed

    Pappas, Charalampos G; Sasselli, Ivan R; Ulijn, Rein V

    2015-07-01

    Structural adaption in living systems is achieved by competing catalytic pathways that drive assembly and disassembly of molecular components under the influence of chemical fuels. We report on a simple mimic of such a system that displays transient, sequence-dependent formation of supramolecular nanostructures based on biocatalytic formation and hydrolysis of self-assembling tripeptides. The systems are catalyzed by α-chymotrypsin and driven by hydrolysis of dipeptide aspartyl-phenylalanine-methyl ester (the sweetener aspartame, DF-OMe). We observed switch-like pathway selection, with the kinetics and consequent lifetime of transient nanostructures controlled by the peptide sequence. In direct competition, kinetic (rather than thermodynamic) component selection is observed.

  6. On the Mechanism of the Palladium-Catalyzed TBHP-Mediated Wacker-Type Oxidation of Alkenes using Quinoline-2-Oxazoline Ligands

    PubMed Central

    Michel, Brian W.; Steffens, Laura D.; Sigman, Matthew S.

    2011-01-01

    The mechanism of the tert-butylhydroperoxide-mediated, Pd(quinox)-catalyzed Wacker-type oxidation was investigated to evaluate the hypothesis that a selective catalyst-controlled oxidation could be achieved by rendering the palladium coordinatively saturated using a bidentate amine ligand. The unique role of the quinox ligand framework was probed via systematic ligand modifications. The modified ligands were evaluated through quantitative Hammett analysis, which supports a “push-pull” relationship between the electronically asymmetric quinoline and oxazoline ligand modules. PMID:21553838

  7. Group 11 Metal Compounds with Tripodal Bis(imidazole) Thioether Ligands. Applications as Catalysts in the Oxidation of Alkenes and as Antimicrobial Agents

    PubMed Central

    Liu, Fangwei; Anis, Reema; Hwang, Eunmi; Ovalle, Rafael; Varela-Ramírez, Armando; Aguilera, Renato J.; Contel, María

    2011-01-01

    New group 11 metal complexes have been prepared using the previously described tripodal bis(imidazole) thioether ligand (N-methyl-4,5-diphenyl-2-imidazolyl)2C(OMe)C(CH3)2S(tert-Bu) ({BITOMe,StBu}, 2). The pincer ligand offers a N2S donor atom set that can be used to coordinate the group 11 metals in different oxidation states [AuI, AuIII, AgI, CuI and CuII]. Thus the new compounds [Au{BITOMe,StBu}Cl][AuCl4]2 (3), [Au{BITOMe,StBu}Cl] (4), [Ag{BITOMe,StBu}X] (X = OSO2CF3 − 5, PF6 − 6) and [Cu{BITOMe,StBu}Cl2] (7) have been synthesized from reaction of 2 with the appropriate metal precursors, and characterized in solution. While attempting characterization in the solid state of 3, single crystals of the neutral dinuclear mixed AuIII-AuI species [Au2{BITOMe,S}Cl3] (8) were obtained and its crystal structure was determined by X-ray diffraction studies. The structure shows a AuIII center coordinated to the pincer ligand through one N and the S atom. The soft AuI center coordinates to the ligand through the same S atom that has lost the tert-butyl group, thus becoming a thiolate ligand. The short distance between the AuI–AuIII atoms (3.383 Å) may indicate a weak metal-metal interaction. Complexes 2–7 and the previously described CuI compound [Cu{BITOMe,StBu}]PF6 (9) have been evaluated in the oxidation of biphenyl ethylene with tert-butyl hydrogen peroxide (TBHP) as the oxidant. Results have shown that the AuI and AgI complexes 4 and 6 (at 10 mol % loading) are the more active catalysts in this oxidative cleavage. The antimicrobial activity of compounds 2–5, 7 and 9 against Gram-positive and Gram-negative bacteria and yeast has also been evaluated. The new gold and silver compounds display moderate to high antibacterial activity, while the copper derivatives are mostly inactive. The gold and silver complexes were also potent against fungi. Their cytotoxic properties have been analyzed in vitro utilizing HeLa human cervical carcinoma cells. The compounds

  8. Recent advances in the ruthenium-catalyzed hydroarylation of alkynes with aromatics: synthesis of trisubstituted alkenes.

    PubMed

    Manikandan, Rajendran; Jeganmohan, Masilamani

    2015-11-14

    The hydroarylation of alkynes with substituted aromatics in the presence of a metal catalyst via chelation-assisted C-H bond activation is a powerful method to synthesize trisubstituted alkenes. Chelation-assisted C-H bond activation can be done by two ways: (a) an oxidative addition pathway and (b) a deprotonation pathway. Generally, a mixture of cis and trans stereoisomeric as well as regioisomeric trisubstituted alkenes was observed in an oxidative addition pathway. In the deprotonation pathway, the hydroarylation reaction can be done in a highly regio- and stereoselective manner, and enables preparation of the expected trisubstituted alkenes in a highly selective manner. Generally, ruthenium, rhodium and cobalt complexes are used as catalysts in the reaction. In this review, a ruthenium-catalyzed hydroarylation of alkynes with substituted aromatics is covered completely. The hydroarylation reaction of alkynes with amide, azole, carbamate, phosphine oxide, amine, acetyl, sulfoxide and sulphur directed aromatics is discussed.

  9. Intermolecular cope-type hydroamination of alkenes and alkynes using hydroxylamines.

    PubMed

    Moran, Joseph; Gorelsky, Serge I; Dimitrijevic, Elena; Lebrun, Marie-Eve; Bédard, Anne-Catherine; Séguin, Catherine; Beauchemin, André M

    2008-12-31

    The development of the Cope-type hydroamination as a method for the metal- and acid-free intermolecular hydroamination of hydroxylamines with alkenes and alkynes is described. Aqueous hydroxylamine reacts efficiently with alkynes in a Markovnikov fashion to give oximes and with strained alkenes to give N-alkylhydroxylamines, while unstrained alkenes are more challenging. N-Alkylhydroxylamines also display similar reactivity with strained alkenes and give modest to good yields with vinylarenes. Electron-rich vinylarenes lead to branched products while electron-deficient vinylarenes give linear products. A beneficial additive effect is observed with sodium cyanoborohydride, the extent of which is dependent on the structure of the hydroxylamine. The reaction conditions are found to be compatible with common protecting groups, free OH and NH bonds, as well as bromoarenes. Both experimental and theoretical results suggest the proton transfer step of the N-oxide intermediate is of vital importance in the intermolecular reactions of alkenes. Details are disclosed concerning optimization, reaction scope, limitations, and theoretical analysis by DFT, which includes a detailed molecular orbital description for the concerted hydroamination process and an exhaustive set of calculated potential energy surfaces for the reactions of various alkenes, alkynes, and hydroxylamines.

  10. Biocatalytic Pathway Selection in Transient Tripeptide Nanostructures.

    PubMed

    Pappas, Charalampos G; Sasselli, Ivan R; Ulijn, Rein V

    2015-07-01

    Structural adaption in living systems is achieved by competing catalytic pathways that drive assembly and disassembly of molecular components under the influence of chemical fuels. We report on a simple mimic of such a system that displays transient, sequence-dependent formation of supramolecular nanostructures based on biocatalytic formation and hydrolysis of self-assembling tripeptides. The systems are catalyzed by α-chymotrypsin and driven by hydrolysis of dipeptide aspartyl-phenylalanine-methyl ester (the sweetener aspartame, DF-OMe). We observed switch-like pathway selection, with the kinetics and consequent lifetime of transient nanostructures controlled by the peptide sequence. In direct competition, kinetic (rather than thermodynamic) component selection is observed. PMID:26014441

  11. Remote functionalization through alkene isomerization.

    PubMed

    Vasseur, Alexandre; Bruffaerts, Jeffrey; Marek, Ilan

    2016-03-01

    Exploiting the reactivity of one functional group within a molecule to generate a reaction at a different position is an ongoing challenge in organic synthesis. Effective remote functionalization protocols have the potential to provide access to almost any derivatives but are difficult to achieve. The difficulty is more pronounced for acyclic systems where flexible alkyl chains are present between the initiating functional group and the desired reactive centres. In this Review, we discuss the concept of remote functionalization of alkenes using metal complexes, leading to a selective reaction at a position distal to the initial double bond. We aim to show the vast opportunity provided by this growing field through selected and representative examples. Our aim is to demonstrate that using a double bond as a chemical handle, metal-assisted long-distance activation could be used as a powerful synthetic strategy. PMID:26892551

  12. Remote functionalization through alkene isomerization

    NASA Astrophysics Data System (ADS)

    Vasseur, Alexandre; Bruffaerts, Jeffrey; Marek, Ilan

    2016-03-01

    Exploiting the reactivity of one functional group within a molecule to generate a reaction at a different position is an ongoing challenge in organic synthesis. Effective remote functionalization protocols have the potential to provide access to almost any derivatives but are difficult to achieve. The difficulty is more pronounced for acyclic systems where flexible alkyl chains are present between the initiating functional group and the desired reactive centres. In this Review, we discuss the concept of remote functionalization of alkenes using metal complexes, leading to a selective reaction at a position distal to the initial double bond. We aim to show the vast opportunity provided by this growing field through selected and representative examples. Our aim is to demonstrate that using a double bond as a chemical handle, metal-assisted long-distance activation could be used as a powerful synthetic strategy.

  13. Remote functionalization through alkene isomerization.

    PubMed

    Vasseur, Alexandre; Bruffaerts, Jeffrey; Marek, Ilan

    2016-03-01

    Exploiting the reactivity of one functional group within a molecule to generate a reaction at a different position is an ongoing challenge in organic synthesis. Effective remote functionalization protocols have the potential to provide access to almost any derivatives but are difficult to achieve. The difficulty is more pronounced for acyclic systems where flexible alkyl chains are present between the initiating functional group and the desired reactive centres. In this Review, we discuss the concept of remote functionalization of alkenes using metal complexes, leading to a selective reaction at a position distal to the initial double bond. We aim to show the vast opportunity provided by this growing field through selected and representative examples. Our aim is to demonstrate that using a double bond as a chemical handle, metal-assisted long-distance activation could be used as a powerful synthetic strategy.

  14. Systematic methodology for the development of biocatalytic hydrogen-borrowing cascades: application to the synthesis of chiral α-substituted carboxylic acids from α-substituted α,β-unsaturated aldehydes.

    PubMed

    Knaus, Tanja; Mutti, Francesco G; Humphreys, Luke D; Turner, Nicholas J; Scrutton, Nigel S

    2015-01-01

    Ene-reductases (ERs) are flavin dependent enzymes that catalyze the asymmetric reduction of activated carbon-carbon double bonds. In particular, α,β-unsaturated carbonyl compounds (e.g. enals and enones) as well as nitroalkenes are rapidly reduced. Conversely, α,β-unsaturated esters are poorly accepted substrates whereas free carboxylic acids are not converted at all. The only exceptions are α,β-unsaturated diacids, diesters as well as esters bearing an electron-withdrawing group in α- or β-position. Here, we present an alternative approach that has a general applicability for directly obtaining diverse chiral α-substituted carboxylic acids. This approach combines two enzyme classes, namely ERs and aldehyde dehydrogenases (Ald-DHs), in a concurrent reductive-oxidative biocatalytic cascade. This strategy has several advantages as the starting material is an α-substituted α,β-unsaturated aldehyde, a class of compounds extremely reactive for the reduction of the alkene moiety. Furthermore no external hydride source from a sacrificial substrate (e.g. glucose, formate) is required since the hydride for the first reductive step is liberated in the second oxidative step. Such a process is defined as a hydrogen-borrowing cascade. This methodology has wide applicability as it was successfully applied to the synthesis of chiral substituted hydrocinnamic acids, aliphatic acids, heterocycles and even acetylated amino acids with elevated yield, chemo- and stereo-selectivity. A systematic methodology for optimizing the hydrogen-borrowing two-enzyme synthesis of α-chiral substituted carboxylic acids was developed. This systematic methodology has general applicability for the development of diverse hydrogen-borrowing processes that possess the highest atom efficiency and the lowest environmental impact.

  15. Alkene anti-Dihydroxylation with Malonoyl Peroxides.

    PubMed

    Alamillo-Ferrer, Carla; Davidson, Stuart C; Rawling, Michael J; Theodoulou, Natalie H; Campbell, Matthew; Humphreys, Philip G; Kennedy, Alan R; Tomkinson, Nicholas C O

    2015-10-16

    Malonoyl peroxide 1, prepared in a single step from the commercially available diacid, is an effective reagent for the anti-dihydroxylation of alkenes. Reaction of 1 with an alkene in the presence of acetic acid at 40 °C followed by alkaline hydrolysis leads to the corresponding diol (35-92%) with up to 13:1 anti-selectivity. A mechanism consistent with experimental findings is proposed that accounts for the selectivity observed. PMID:26425839

  16. The Origin of Anti-Markovnikov Regioselectivity in Alkene Hydroamination Reactions Catalyzed by [Rh(DPEphos)](.).

    PubMed

    Couce-Rios, Almudena; Lledós, Agustí; Ujaque, Gregori

    2016-06-27

    The development of regioselective anti-Markovnikov alkene's hydroamination is a long-standing goal in catalysis. The [Rh(COD)(DPEphos)](+) complex is the most general and regioselective group 9 catalyst for such a process. The reaction mechanism for intermolecular hydroamination of alkenes catalyzed by [Rh(DPEphos)](+) complex is analyzed by means of DFT calculations. Hydroamination (alkene vs. amine activation routes) as well as oxidative amination pathways are analyzed. According to the computational results the operating mechanism can be generally described by alkene coordination, amine nucleophilic addition, proton transfer through the metal center and reductive elimination steps. The mechanism for the formation of the oxidative amination side product goes via a β-elimination after the nucleophilic addition and metal center protonation steps. The origin of the regioselectivity for the addition process (Markovnikov vs. anti-Markovnikov additions) is shown to be not charge but orbitally driven. Remarkably, η(2) to η(1) slippage degree on the alkene coordination mode is directly related to the regioselective outcome.

  17. The Origin of Anti-Markovnikov Regioselectivity in Alkene Hydroamination Reactions Catalyzed by [Rh(DPEphos)](.).

    PubMed

    Couce-Rios, Almudena; Lledós, Agustí; Ujaque, Gregori

    2016-06-27

    The development of regioselective anti-Markovnikov alkene's hydroamination is a long-standing goal in catalysis. The [Rh(COD)(DPEphos)](+) complex is the most general and regioselective group 9 catalyst for such a process. The reaction mechanism for intermolecular hydroamination of alkenes catalyzed by [Rh(DPEphos)](+) complex is analyzed by means of DFT calculations. Hydroamination (alkene vs. amine activation routes) as well as oxidative amination pathways are analyzed. According to the computational results the operating mechanism can be generally described by alkene coordination, amine nucleophilic addition, proton transfer through the metal center and reductive elimination steps. The mechanism for the formation of the oxidative amination side product goes via a β-elimination after the nucleophilic addition and metal center protonation steps. The origin of the regioselectivity for the addition process (Markovnikov vs. anti-Markovnikov additions) is shown to be not charge but orbitally driven. Remarkably, η(2) to η(1) slippage degree on the alkene coordination mode is directly related to the regioselective outcome. PMID:27226329

  18. Biocatalytic removal of organic sulfur from coal

    SciTech Connect

    Webster, D.A.; Kilbane, J.J. II

    1994-09-09

    The objective is to characterize more completely the biochemical ability of the bacterium, Rhodococcus rhodochrous IGTS8, to cleave carbon-sulfur bonds with emphasis on data that will allow the development of a practical coal biodesulfurization process. Another approach for increasing the desulfurization activity of the IGTS8 cultures is to produce strains genetically that have higher activity. The goal of this part of research is to achieve strain improvement by introducing a stronger promoter using genetic engineering techniques. The promoter regulates the transcription of the genes for the desulfurization enzymes, and a stronger promoter, would up-regulate the expression of these genes, resulting in cells with higher desulfurization activity. Promoter probe vectors are used to identify and isolate promoters from a DNA library of the experimental organism. The major accomplishments have been to obtain high biodesulfurization activity in nonaqueous, media, especially using freeze-dried cells, and to have isolated strong promoters from R. rhodochrous IGTS8 which will be used to engineer the organism to produce strains with higher biocatalytic activity.

  19. Biocatalytic desulfurization (BDS) of petrodiesel fuels.

    PubMed

    Mohebali, Ghasemali; Ball, Andrew S

    2008-08-01

    Oil refineries are facing many challenges, including heavier crude oils, increased fuel quality standards, and a need to reduce air pollution emissions. Global society is stepping on the road to zero-sulfur fuel, with only differences in the starting point of sulfur level and rate reduction of sulfur content between different countries. Hydrodesulfurization (HDS) is the most common technology used by refineries to remove sulfur from intermediate streams. However, HDS has several disadvantages, in that it is energy intensive, costly to install and to operate, and does not work well on refractory organosulfur compounds. Recent research has therefore focused on improving HDS catalysts and processes and also on the development of alternative technologies. Among the new technologies one possible approach is biocatalytic desulfurization (BDS). The advantage of BDS is that it can be operated in conditions that require less energy and hydrogen. BDS operates at ambient temperature and pressure with high selectivity, resulting in decreased energy costs, low emission, and no generation of undesirable side products. Over the last two decades several research groups have attempted to isolate bacteria capable of efficient desulfurization of oil fractions. This review examines the developments in our knowledge of the application of bacteria in BDS processes, assesses the technical viability of this technology and examines its future challenges.

  20. Biocatalytic Reductions of Baylis - Hillman Adducts

    SciTech Connect

    A Walton; W Conerly; Y Pompeu; B Sullivan; J Stewart

    2011-12-31

    Baylis-Hillman adducts are highly useful synthetic intermediates; to enhance their value further, we sought enantiocomplementary alkene reductases to introduce chirality. Two solutions emerged: (1) a wild-type protein from Pichia stipitis (OYE 2.6), whose performance significantly outstrips that of the standard enzyme (Saccharomyces pastorianus OYE1), and (2) a series of OYE1 mutants at position 116 (Trp in the wild-type enzyme). To understand how mutations could lead to inverted enantioselectivity, we solved the X-ray crystal structure of the Trp116Ile OYE1 variant complexed with a cyclopentenone substrate. This revealed key protein-ligand interactions that control the orientation of substrate binding above the FMN cofactor.

  1. A General Approach to Catalytic Alkene Anti-Markovnikov Hydrofunctionalization Reactions via Acridinium Photoredox Catalysis.

    PubMed

    Margrey, Kaila A; Nicewicz, David A

    2016-09-20

    The development of methods for anti-Markovnikov alkene hydrofunctionalization has been a focal point of catalysis research for several decades. The vast majority of work on the control of regioselectivity for this reaction class has hinged on transition metal catalyst activation of olefin substrates. While progress has been realized, there are significant limitations to this approach, and a general solution for catalysis of anti-Markovnikov hydrofunctionalization reactions of olefins does not presently exist. In the past several years, this research lab has focused on alkene activation by single electron oxidation using organic photoredox catalysts to facilitate anti-Markovnikov hydrofunctionalization. By accessing reactive cation radical intermediates, we have realized a truly general approach to anti-Markovnikov olefin hydrofunctionalization reactions. We have identified a dual organic catalyst system consisting of an acridinium photooxidant, first reported by Fukuzumi, and a redox-active hydrogen atom donor that accomplishes a wide range of hydrofunctionalization reactions with complete anti-Markovnikov regiocontrol. This method relies on single electron oxidation of the alkene to reverse its polarity and results in the opposite regioselectivity for hydrofunctionalization. In 2012, we disclosed the anti-Markovnikov hydroetherification of alkenols employing an acridinium photocatalyst and a hydrogen atom donor that proceeds via interwoven polar and radical steps. This general catalyst system has enabled several important reactions in this area, including anti-Markovnikov alkene hydroacetoxylation, hydrolactonization, hydroamination, and hydrotrifluoromethylation reactions. More recently, we have also delineated conditions for intermolecular anti-Markovnikov hydroamination reactions of alkenes using either triflamide or nitrogen-containing heteroaromatic compounds such as pyrazole, indazole, imidazole, and 1,2,3-triazole. Further development led to a method for

  2. A General Approach to Catalytic Alkene Anti-Markovnikov Hydrofunctionalization Reactions via Acridinium Photoredox Catalysis.

    PubMed

    Margrey, Kaila A; Nicewicz, David A

    2016-09-20

    The development of methods for anti-Markovnikov alkene hydrofunctionalization has been a focal point of catalysis research for several decades. The vast majority of work on the control of regioselectivity for this reaction class has hinged on transition metal catalyst activation of olefin substrates. While progress has been realized, there are significant limitations to this approach, and a general solution for catalysis of anti-Markovnikov hydrofunctionalization reactions of olefins does not presently exist. In the past several years, this research lab has focused on alkene activation by single electron oxidation using organic photoredox catalysts to facilitate anti-Markovnikov hydrofunctionalization. By accessing reactive cation radical intermediates, we have realized a truly general approach to anti-Markovnikov olefin hydrofunctionalization reactions. We have identified a dual organic catalyst system consisting of an acridinium photooxidant, first reported by Fukuzumi, and a redox-active hydrogen atom donor that accomplishes a wide range of hydrofunctionalization reactions with complete anti-Markovnikov regiocontrol. This method relies on single electron oxidation of the alkene to reverse its polarity and results in the opposite regioselectivity for hydrofunctionalization. In 2012, we disclosed the anti-Markovnikov hydroetherification of alkenols employing an acridinium photocatalyst and a hydrogen atom donor that proceeds via interwoven polar and radical steps. This general catalyst system has enabled several important reactions in this area, including anti-Markovnikov alkene hydroacetoxylation, hydrolactonization, hydroamination, and hydrotrifluoromethylation reactions. More recently, we have also delineated conditions for intermolecular anti-Markovnikov hydroamination reactions of alkenes using either triflamide or nitrogen-containing heteroaromatic compounds such as pyrazole, indazole, imidazole, and 1,2,3-triazole. Further development led to a method for

  3. Coated-wall microreactor for continuous biocatalytic transformations using immobilized enzymes.

    PubMed

    Thomsen, Malene S; Nidetzky, Bernd

    2009-01-01

    Microstructured flow reactors are emerging tools for biocatalytic process development. A compelling design is that of the coated-wall reactor where enzyme is present as a surface layer attached to microchannel walls. However, preparation of a highly active wall biocatalyst remains a problem. Here, a stainless steel microreactor was developed where covalent immobilization of the enzyme in multiple linear flow channels of the reaction plate was supported by a macroporous wash-coat layer of gamma-aluminum oxide. Using surface functionalization with aminopropyl triethoxysilane followed by activation with glutardialdehyde, the thermophilic beta-glycosidase CelB from Pyrococcus furiosus was bound with retention of half of the specific activity of the free enzyme (800 U/mg), yielding a high catalyst loading of about 500 U/mL. This microreactor was employed for the continuous hydrolysis of lactose (100 mM) at 80 degrees C, providing a space-time yield of 500 mg glucose/(mL h) at a stable conversion of > or =70%. The immobilized enzyme displayed a half-life of 15 days under the operational conditions. Due to the absence of hydrophobic solute-material interactions, which limit the scope of microstructures fabricated from poly(dimethylsiloxane) for biocatalytic applications, the new microreactor was fully compatible with the alternate enzyme substrate 2-nitro-phenyl-beta-D-galactoside and the 2-nitro-phenol product resulting from its hydrolysis catalyzed by CelB. PMID:18618472

  4. Heterogeneous Catalysis: The Horiuti-Polanyi Mechanism and Alkene Hydrogenation

    ERIC Educational Resources Information Center

    Mattson, Bruce; Foster, Wendy; Greimann, Jaclyn; Hoette, Trisha; Le, Nhu; Mirich, Anne; Wankum, Shanna; Cabri, Ann; Reichenbacher, Claire; Schwanke, Erika

    2013-01-01

    The hydrogenation of alkenes by heterogeneous catalysts has been studied for 80 years. The foundational mechanism was proposed by Horiuti and Polanyi in 1934 and consists of three steps: (i) alkene adsorption on the surface of the hydrogenated metal catalyst, (ii) hydrogen migration to the beta-carbon of the alkene with formation of a delta-bond…

  5. 40 CFR 721.10508 - Alkene substituted Bis phenol (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Alkene substituted Bis phenol (generic... Specific Chemical Substances § 721.10508 Alkene substituted Bis phenol (generic). (a) Chemical substance... alkene substituted bis phenol (PMN P-07-161) is subject to reporting under this section for...

  6. 40 CFR 721.10508 - Alkene substituted Bis phenol (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Alkene substituted Bis phenol (generic... Specific Chemical Substances § 721.10508 Alkene substituted Bis phenol (generic). (a) Chemical substance... alkene substituted bis phenol (PMN P-07-161) is subject to reporting under this section for...

  7. Biocatalytic Refining of Soybean Oil into Cosmeceutical Ingredients

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Our mission is to develop new, value-added uses for commodity crops and oils. We chose to fulfill this mission while adhering as closely as possible to the tenants of “green” chemistry. We have developed patented, all-natural oils called Feruloyl Soy Glycerols (FSG) from the biocatalytic transester...

  8. [C. E. Alken (1909-1986) and the Alken-Prize].

    PubMed

    Konert, J

    2016-06-01

    C. E. Alken is regarded as the Nestor of German urology post World War II. His development path is given in brief and his specific contributions to the emancipation of the field are pointed out. In 1948 he received a teaching assignment in urology at Saarland State University Homburg, where in 1952, a Chair of Urology was established, and in 1958 he received the Ordinariat. The "Alken-Prize" which was named after him, is also presented.

  9. Alkene epoxidation employing metal nitro complexes

    DOEpatents

    Andrews, M.A.; Cheng, C.W.; Kelley, K.P.

    1982-07-15

    Process for converting alkenes to form epoxides utilizes transition metal nitro complexes of the formula: M(RCN)/sub 2/XNO/sub 2/ wherein M is palladium or platinum, R is an alkyl or aryl group containing up to 12 carbon atoms, and X is a monoanionic, monodentate ligand such as chlorine, optionally in the presence of molecular oxygen.

  10. A biocatalytic approach towards synthesis of polymer CdS nanocomposites

    SciTech Connect

    Banerjee, S.; Premchandran, R.; Baumgartner, T.

    1996-10-01

    Copolymers of hydroxythiophenol and ethylphenol have been prepared using a biocatalytic route. Specifically, the method utilizes an oxidative enzyme, horseradish peroxidase, solubilized within the aqueous phase of a AOT/isooctane microemulsion. The monomers are oil soluble and are thus present in the organic phase. High conversions are obtained upto 1:1 molar ratio of the two monomers. The resulting polymers have the overall morphology of interconnected submicron spheres and are soluble in common organic solvents. Following their synthesis these copolymers have been derivatized by attaching Q-sized CdS particles. Though the copolymer itself is nonfluorescent, the CdS nanoclusters within it can be selectively excited and made to fluoresce. The fluorescent properties of the polymer CdS composite are distinctive from underivatized CdS or hydroxythiophenol monomer capped CdS.

  11. A new approach to the deposition of nanostructured biocatalytic films

    NASA Astrophysics Data System (ADS)

    Troitsky, V. I.; Berzina, T. S.; Pastorino, L.; Bernasconi, E.; Nicolini, C.

    2003-06-01

    In the present work, monolayer engineering was used to fabricate biocatalytic nanostructured thin films based on the enzyme penicillin G acylase. The biocatalytic films with enhanced characteristics were produced by the deposition of alternate-layer assemblies with a predetermined structure using a combination of Langmuir-Blodgett and adsorption techniques. The value of enzyme activity and the level of protein detachment were measured in dependence on the variation of film composition and on the sequence of layer alternation. As a result, highly active and stable structures were found, which could be promising candidates for practical applications. The method of modification of the deposition method to provide continuous film formation on large-area supports is discussed.

  12. Methods for direct alkene diamination, new & old

    PubMed Central

    de Jong, Sam; Nosal, Daniel G.; Wardrop, Duncan J.

    2012-01-01

    The 1,2-diamine moiety is a ubiquitous structural motif present in a wealth of natural products, including non-proteinogenic amino acids and numerous alkaloids, as well as in pharmaceutical agents, chiral ligands and organic reagents. The biological activity associated with many of these systems and their chemical utility in general has ensured that the development of methods for their preparation is of critical importance. While a wide range of strategies for the preparation of 1,2-diamines have been established, the diamination of alkenes offers a particularly direct and efficient means of accessing these systems. The purpose of this review is to provide an overview of all methods of direct alkene diamination, metal-mediated or otherwise. PMID:22888177

  13. Trifluoromethylation of alkenes by visible light photoredox catalysis.

    PubMed

    Iqbal, Naeem; Choi, Sungkyu; Kim, Eunjin; Cho, Eun Jin

    2012-12-21

    A method for trifluoromethylation of alkenes has been developed employing visible light photoredox catalysis with CF(3)I, Ru(Phen)(3)Cl(2), and DBU. This process works especially well for terminal alkenes to give alkenyl-CF(3) products with only E-stereochemistry. The mild reaction conditions enable the trifluoromethylation of a range of alkenes that bear various functional groups. PMID:23167602

  14. [C. E. Alken (1909-1986) and the Alken-Prize].

    PubMed

    Konert, J

    2016-06-01

    C. E. Alken is regarded as the Nestor of German urology post World War II. His development path is given in brief and his specific contributions to the emancipation of the field are pointed out. In 1948 he received a teaching assignment in urology at Saarland State University Homburg, where in 1952, a Chair of Urology was established, and in 1958 he received the Ordinariat. The "Alken-Prize" which was named after him, is also presented. PMID:27160773

  15. Ligand-Controlled Regiodivergent Copper-Catalyzed Alkylboration of Alkenes.

    PubMed

    Su, Wei; Gong, Tian-Jun; Lu, Xi; Xu, Meng-Yu; Yu, Chu-Guo; Xu, Zheng-Yang; Yu, Hai-Zhu; Xiao, Bin; Fu, Yao

    2015-10-26

    A novel copper-catalyzed regiodivergent alkylboration of alkenes with bis(pinacolato)diboron and alkyl halides has been developed. The regioselectivity of the alkylboration was controlled by subtle differences in the ligand structure. The reaction thus enables the practical, regiodivergent synthesis of two different alkyl boronic esters with complex structures from a single alkene. PMID:26338141

  16. Reversible Interconversion between Alkanes, Alkenes, Alcohols and Ketones under Hydrothermal Conditions

    NASA Astrophysics Data System (ADS)

    Shipp, J.; Hartnett, H. E.; Gould, I. R.; Shock, E.; Williams, L. B.

    2011-12-01

    Many transformation reactions involving hydrocarbons that occur in deep sedimentary systems and determine petroleum compositions occur in the presence of H2O. Hydrothermal transformations of organic material are thought to provide carbon sources for microbes in deep ocean sediments. Hydrothermal conditions may also mimic the conditions where life developed on an early Earth. Nevertheless, much remains to be learned about the mechanisms of hydrothermal organic reactions, including ways in which various reactions are interrelated and how reactions compete with each other. It can be argued that metastable equilibrium states develop over geological timescales and at geochemically relevant temperatures, suggesting that reactions occur under thermodynamic rather than kinetic control. The extent to which reactions are reversible, and how product distributions are determined, are primary tests of the metastable equilibrium model. Seewald (2001, GCA 65, 1641-1664) showed that under hydrothermal conditions and in the presence of a redox buffer, simple alkanes and alkenes undergo oxidation, reduction, and hydration reactions. He proposed a reaction scheme where alkanes interconvert with alkenes, followed by stepwise hydration of alkenes to alcohols, oxidation to ketones, and finally conversion to carboxylic acids, which can undergo decarboxylation. Here we describe experiments that further develop the scope of these functional group interconversions, determine relative reaction kinetics, and provide insight into competing reactions. Hydrothermal experiments were performed at 300°C and 100 MPa in gold capsules for 12 to 144 hours. The reactant structures were based on cyclohexane with one and two methyl groups that served as regio- and stereochemical markers for the reactions. Starting with the alkanes, the observed products include the corresponding alkenes, alcohols, ketones and enones, in support of the Seewald reaction scheme. Our experiments add a branch to this scheme

  17. Rapid biocatalytic polytransesterification: Reaction kinetics in an exothermic reaction

    SciTech Connect

    Chaudhary, A.K.; Beckman, E.J.; Russell, A.J.

    1998-08-20

    Biocatalytic polytransesterification at high concentrations of monomers proceeds rapidly and is accompanied by an increase in the temperature of the reaction mixture due to liberation of heat of reaction during the initial phase. The authors have used principles of reaction calorimetry to monitor the kinetics of polymerization during this initial phase, thus relating the temperature to the extent of polymerization. Rate of polymerization increases with the concentration of monomers. This is also reflected by the increase in the temperature of the reaction mixture. Using time-temperature-conversion contours, a differential method of kinetic analysis was used to calculate the energy of activation ({approximately} 15.1 Kcal/mol).

  18. Biocatalytic approaches applied to the synthesis of nucleoside prodrugs.

    PubMed

    Iglesias, Luis E; Lewkowicz, Elizabeth S; Medici, Rosario; Bianchi, Paola; Iribarren, Adolfo M

    2015-01-01

    Nucleosides are valuable bioactive molecules, which display antiviral and antitumour activities. Diverse types of prodrugs are designed to enhance their therapeutic efficacy, however this strategy faces the troublesome selectivity issues of nucleoside chemistry. In this context, the aim of this review is to give an overview of the opportunities provided by biocatalytic procedures in the preparation of nucleoside prodrugs. The potential of biocatalysis in this research area will be presented through examples covering the different types of nucleoside prodrugs: nucleoside analogues as prodrugs, nucleoside lipophilic prodrugs and nucleoside hydrophilic prodrugs.

  19. Tritium labelled alkenes via the Shapiro reaction

    SciTech Connect

    Saljoughian, Manouchehr; Morimoto, Hiromi; Than, Chit; Williams, P.G.

    1995-12-31

    The authors report a simple synthesis of a variety of tritiated alkenes with high specific activity. The labelling steps involved in situ generation of the vinyllithium derivatives of the intermediate trisylhydrazone at low temperature, followed by quenching with high specific activity Tritiated water as an electrophile to generate the final tritiated alkenes. Several ketonic precursors with cyclopentanone and cyclohexanone rings, {alpha},{beta}-unsaturated and large ring cyclic ketones were selected and the corresponding trisylhydrazone derivatives were prepared. The Shapiro reaction conditions were optimized to work at a millimolar scale using deuteriated water as the electrophile. The successful reaction conditions were finally applied to the tritiation reactions. The chemical and radiochemical purity, and the specific radioactivity of the reaction products were determined by radio-hplc, gas chromatography and liquid scintillation counting as well as tritium NMR spectroscopy. The stereochemistry and specificity of tritium labelling was also established with tritium NMR spectroscopy. Application of different organolithium bases and the reaction mechanisms will be discussed.

  20. Biochemical and biocatalytic characterization of 17 novel halohydrin dehalogenases.

    PubMed

    Koopmeiners, Julia; Halmschlag, Birthe; Schallmey, Marcus; Schallmey, Anett

    2016-09-01

    Halohydrin dehalogenases are rare but catalytically remarkable enzymes since they are able to form novel C-C, C-O, C-N, or C-S bonds. Very recently, a motif-based sequence database mining approach resulted in the identification of 37 novel halohydrin dehalogenase enzymes, many of them exhibiting only low sequence similarity to previously known halohydrin dehalogenases. In an attempt to explore the biocatalytic potential of these newly identified enzymes, 17 representatives from all six phylogenetic subtypes were heterologously produced in Escherichia coli, purified and characterized to determine their substrate scopes in the dehalogenation and epoxide ring-opening reaction. Several enzymes with broad substrate spectra were identified exhibiting high activities towards a selection of typical substrates. Moreover, four halohydrin dehalogenases were found to be significantly more thermostable than the previously known HheC from Agrobacterium radiobacter AD1. Investigation of the enzymes' stereoselectivity in the dehalogenation of racemic 2-chloro-1-phenylethanol revealed that their stereopreference correlates with the phylogenetic placing of the enzymes in subtypes A through G. Furthermore, the biocatalytic potential of these novel halohydrin dehalogenases was investigated in the preparation of ethyl 4-cyano-3-hydroxybutyrate, a statin side-chain precursor. Though none of the active enzymes selectively formed the required (R)-enantiomer, several halohydrin dehalogenases were identified with significantly higher activity in the conversion compared to HheC, making them promising candidates for this industrially relevant reaction. PMID:27052376

  1. Enzyme-polymer composites with high biocatalytic activity and stability

    SciTech Connect

    Kim, Jungbae; Kosto, Timothy J.; Manimala, Joseph C.; Nauman, E B.; Dordick, Jonathan S.

    2004-08-22

    We have applied vacuum-spraying and electrospinning to incorporate an enzyme into a polymer matrix, creating a novel and highly active biocatalytic composite. As a unique technical approach, enzymes were co-dissolved in toluene with polymers, and the solvent was then rapidly removed by injecting the mixture into a vacuum chamber or by electrospinning. Subsequent crosslinking of the enzyme with glutaraldehyde resulted in stable entrapped enzyme within the polymeric matrices. For example, an amorphous composite of alpha-chymotrypsin and polyethylene showed no significant loss of enzymatic activity in aqueous buffer for one month. Nanofibers of alpha-chymotrypsin and polystyrene also showed no decrease in activity for more than two weeks. The normalized activity of amorphous composite in organic solvents was 3-13 times higher than that of native alpha-chymotrypsin. The activity of nanofibers was 5-7 times higher than that of amorphous composite in aqueous buffer solution. The composites of alpha-chymotrypsin and polymers demonstrate the feasibility of obtaining a wide variety of active and stable biocatalytic materials with many combinations of enzymes and polymers.

  2. Bioconjugation with strained alkenes and alkynes.

    PubMed

    Debets, Marjoke F; van Berkel, Sander S; Dommerholt, Jan; Dirks, A Ton J; Rutjes, Floris P J T; van Delft, Floris L

    2011-09-20

    The structural complexity of molecules isolated from biological sources has always served as an inspiration for organic chemists. Since the first synthesis of a natural product, urea, chemists have been challenged to prepare exact copies of natural structures in the laboratory. As a result, a broad repertoire of synthetic transformations has been developed over the years. It is now feasible to synthesize organic molecules of enormous complexity, and also molecules with less structural complexity but prodigious societal impact, such as nylon, TNT, polystyrene, statins, estradiol, XTC, and many more. Unfortunately, only a few chemical transformations are so mild and precise that they can be used to selectively modify biochemical structures, such as proteins or nucleic acids; these are the so-called bioconjugation strategies. Even more challenging is to apply a chemical reaction on or in living cells or whole organisms; these are the so-called bioorthogonal reactions. These fields of research are of particular importance because they not only pose a worthy challenge for chemists but also offer unprecedented possibilities for studying biological systems, especially in areas in which traditional biochemistry and molecular biology tools fall short. Recent years have seen tremendous growth in the chemical biology toolbox. In particular, a rapidly increasing number of bioorthogonal reactions has been developed based on chemistry involving strained alkenes or strained alkynes. Such strained unsaturated systems have the unique ability to undergo (3 + 2) and (4 + 2) cycloadditions with a diverse set of complementary reaction partners. Accordingly, chemistry centered around strain-promoted cycloadditions has been exploited to precisely modify biopolymers, ranging from nucleic acids to proteins to glycans. In this Account, we describe progress in bioconjugation centered around cycloadditions of these strained unsaturated systems. Being among the first to recognize the utility

  3. Synthesis of terminal alkenes from internal alkenes and ethylene via olefin metathesis

    DOEpatents

    Schrodi, Yann

    2015-09-22

    This invention relates generally to olefin metathesis, and more particularly relates to the synthesis of terminal alkenes from internal alkenes using a cross-metathesis reaction catalyzed by a selected olefin metathesis catalyst. In one embodiment of the invention, for example, a method is provided for synthesizing a terminal olefin, the method comprising contacting an olefinic substrate comprised of at least one internal olefin with ethylene, in the presence of a metathesis catalyst, wherein the catalyst is present in an amount that is less than about 1000 ppm relative to the olefinic substrate, and wherein the metathesis catalyst has the structure of formula (II) ##STR00001## wherein the various substituents are as defined herein. The invention has utility, for example, in the fields of catalysis, organic synthesis, and industrial chemistry.

  4. Synthesis of terminal alkenes from internal alkenes and ethylene via olefin metathesis

    DOEpatents

    Schrodi, Yann

    2011-11-29

    This invention relates generally to olefin metathesis, and more particularly relates to the synthesis of terminal alkenes from internal alkenes using a cross-metathesis reaction catalyzed by a selected olefin metathesis catalyst. In one embodiment of the invention, for example, a method is provided for synthesizing a terminal olefin, the method comprising contacting an olefinic substrate comprised of at least one internal olefin with ethylene, in the presence of a metathesis catalyst, wherein the catalyst is present in an amount that is less than about 1000 ppm relative to the olefinic substrate, and wherein the metathesis catalyst has the structure of formula (II) ##STR00001## wherein the various substituents are as defined herein. The invention has utility, for example, in the fields of catalysis, organic synthesis, and industrial chemistry.

  5. Synthesis of terminal alkenes from internal alkenes and ethylene via olefin metathesis

    DOEpatents

    Schrodi, Yann

    2013-07-09

    This invention relates generally to olefin metathesis, and more particularly relates to the synthesis of terminal alkenes from internal alkenes using a cross-metathesis reaction catalyzed by a selected olefin metathesis catalyst. In one embodiment of the invention, for example, a method is provided for synthesizing a terminal olefin, the method comprising contacting an olefinic substrate comprised of at least one internal olefin with ethylene, in the presence of a metathesis catalyst, wherein the catalyst is present in an amount that is less than about 1000 ppm relative to the olefinic substrate, and wherein the metathesis catalyst has the structure of formula (II) ##STR00001## wherein the various substituents are as defined herein. The invention has utility, for example, in the fields of catalysis, organic synthesis, and industrial chemistry.

  6. Synthesis of terminal alkenes from internal alkenes and ethylene via olefin metathesis

    DOEpatents

    Schrodi, Yann

    2016-02-09

    This invention relates generally to olefin metathesis, and more particularly relates to the synthesis of terminal alkenes from internal alkenes using a cross-metathesis reaction catalyzed by a selected olefin metathesis catalyst. In one embodiment of the invention, for example, a method is provided for synthesizing a terminal olefin, the method comprising contacting an olefinic substrate comprised of at least one internal olefin with ethylene, in the presence of a metathesis catalyst, wherein the catalyst is present in an amount that is less than about 1000 ppm relative to the olefinic substrate, and wherein the metathesis catalyst has the structure of formula (II) ##STR00001## wherein the various substituents are as defined herein. The invention has utility, for example, in the fields of catalysis, organic synthesis, and industrial chemistry.

  7. Metal-free direct trifluoromethylation of activated alkenes with Langlois' reagent leading to CF3-containing oxindoles.

    PubMed

    Wei, Wei; Wen, Jiangwei; Yang, Daoshan; Liu, Xiaoxia; Guo, Mengyuan; Dong, Ruimei; Wang, Hua

    2014-05-01

    A metal-free and cost-effective synthesis protocol has been initially proposed for the construction of CF3-containing oxindoles via the direct oxidative trifluoromethylation of activated alkenes with Langlois' reagent (CF3SO2Na). The present methodology, which utilizes very cheap CF3 reagent and a simple oxidant, provides a convenient and practical approach to CF3-containing oxindoles with a wide variety of functional groups. PMID:24689970

  8. Electrophilic Addition to Alkenes: The Relation between Reactivity and Enthalpy of Hydrogenation: Regioselectivity is Determined by the Stability of the Two Conceivable Products.

    PubMed

    Schnatter, Wayne F K; Rogers, Donald W; Zavitsas, Andreas A

    2015-07-13

    Although electrophilic addition to alkenes has been well studied, some secrets still remain. Halogenations, hydrohalogenations, halohydrin formations, hydrations, epoxidations, other oxidations, carbene additions, and ozonolyses are investigated to elucidate the relation of alkene reactivities with their enthalpies of hydrogenation (ΔHhyd ). For addition of electrophiles to unconjugated hydrocarbon alkenes, ln(k) is a linear function of ΔHhyd , where k is the rate constant. Linear correlation coefficients are about 0.98 or greater. None of the many previously proposed correlations of ln(k) with the properties of alkenes or with linear free-energy relationships match the generality and accuracy of the simple linear relationship found herein. A notable exception is acid-catalyzed hydration in water or in solvents stabilizing relatively stable carbocation intermediates (e.g., tertiary, benzylic, or allylic). (13) C NMR chemical shifts of the two alkene carbons also predict regioselectivity. These effects have not been noted previously and are operative in general, including addition to heteroatom-substituted alkenes.

  9. Products and Kinetics of the Reactions of an Alkane Monolayer and a Terminal Alkene Monolayer with NO₃ Radicals

    SciTech Connect

    Gross, Simone; Bertram, Allan K.

    2009-01-27

    The reactions of an alkanethiol and a terminal alkenethiol self-assembled monolayer with NO₃ radicals (in the presence of NO₂ and O₂) were studied. For the alkane monolayer, infrared (IR) spectroscopy and time-of-flight secondary ion mass spectrometry (ToF-SIMS) confirmed the formation of organonitrates (RONO₂). The observation of organonitrates is in contrast to the recent X-ray photoelectron spectroscopy (XPS) data, which showed very little nitrogen-containing surface species. The identification of organonitrates may help explain why significant volatilization of the organic chain was not observed in recent studies of alkane monolayer oxidation by NO₃ radicals. The reactive uptake coefficient (g) of NO₃ on alkene monolayers determined in our study is higher than the values obtained in a recent study using liquid and solid alkene bulk films. A possible reason for this difference may be the location of the double bond at the interface. Using the g value determined in our studies, we show that under conditions where NO₃ is high the lifetime of an alkene monolayer in the atmosphere may be short (approximately 20 min). XPS, IR, and ToF-SIMS were used to identify surface functional groups after the oxidation of the alkene monolayers by NO₃. The results are consistent with the formation of C-O, aldehyde/ketone, carboxylic groups, and nitrogen containing species.

  10. Kinetics and mechanism of the oxidation of alkenes and silanes by hydrogen peroxide catalyzed by methylrhenium trioxide (MTO) and a novel application of electrospray mass spectrometry to study the hydrolysis of MTO

    SciTech Connect

    Tan, Haisong

    1999-11-08

    Conjugated dienes were oxidized by hydrogen peroxide with methylrhenium trioxide (MTO) as catalyst. Methylrhenium bis-peroxide was the major reactive catalyst present. Hydroxyalkenes and trisubstituted silane were also tested. Mechanisms for each of these reactions are presented.

  11. Catalytic reversible alkene-nitrile interconversion through controllable transfer hydrocyanation.

    PubMed

    Fang, Xianjie; Yu, Peng; Morandi, Bill

    2016-02-19

    Nitriles and alkenes are important synthetic intermediates with complementary reactivity that play a central role in the preparation of materials, pharmaceuticals, cosmetics, and agrochemicals. Here, we report a nickel-catalyzed transfer hydrocyanation reaction between a wide range (60 examples) of alkyl nitriles and alkenes. This strategy not only overcomes the toxicity challenge posed by the use of HCN in traditional approaches, but also encompasses distinct chemical advances, including retro-hydrocyanation and anti-Markovnikov regioselectivity. In a broader context, this work highlights an approach to the reversible hydrofunctionalization of alkenes through thermodynamically controlled transfer reactions to circumvent the use of volatile and hazardous reagents in the laboratory. PMID:26912891

  12. Radical product yields from the ozonolysis of short chain alkenes under atmospheric boundary layer conditions.

    PubMed

    Alam, Mohammed S; Rickard, Andrew R; Camredon, Marie; Wyche, Kevin P; Carr, Timo; Hornsby, Karen E; Monks, Paul S; Bloss, William J

    2013-11-27

    The gas-phase reaction of ozone with unsaturated volatile organic compounds (VOCs), alkenes, is an important source of the critical atmospheric oxidant OH, especially at night when other photolytic radical initiation routes cannot occur. Alkene ozonolysis is also known to directly form HO2 radicals, which may be readily converted to OH through reaction with NO, but whose formation is poorly understood. We report a study of the radical (OH, HO2, and RO2) production from a series of small alkenes (propene, 1-butene, cis-2-butene, trans-2-butene, 2-methylpropene, 2,3-dimethyl-2-butene (tetramethyl ethene, TME), and isoprene). Experiments were performed in the European Photoreactor (EUPHORE) atmospheric simulation chamber, with OH and HO2 levels directly measured by laser-induced fluorescence (LIF) and HO2 + ΣRO2 levels measured by peroxy-radical chemical amplification (PERCA). OH yields were found to be in good agreement with the majority of previous studies performed under comparable conditions (atmospheric pressure, long time scales) using tracer and scavenger approaches. HO2 yields ranged from 4% (trans-2-butene) to 34% (2-methylpropene), lower than previous experimental determinations. Increasing humidity further reduced the HO2 yields obtained, by typically 50% for an RH increase from 0.5 to 30%, suggesting that HOx production from alkene ozonolysis may be lower than current models suggest under (humid) ambient atmospheric boundary layer conditions. The mechanistic origin of the OH and HO2 production observed is discussed in the context of previous experimental and theoretical studies.

  13. Asymmetric synthesis from terminal alkenes by diboration/cross-coupling cascades

    PubMed Central

    Mlynarski, Scott N.; Schuster, Christopher H.; Morken, James P.

    2013-01-01

    Amongst prospective starting materials for organic synthesis, terminal (monosubstituted) alkenes are ideal. In the form of α-olefins, they are manufactured on enormous scale and they are the core product features from many organic chemical reactions. While their latent reactivity can easily enable hydrocarbon chain extension, alkenes also have the attractive feature of being stable in the presence of many acids, bases, oxidants and reductants. In spite of these impressive attributes, relatively few catalytic enantioselective transformations have been developed that transform aliphatic α-olefins in >90% ee and, with the exception of site-controlled isotactic polymerization of α-olefins,1 none of these processes result in chain-extending C-C bond formation to the terminal carbon.2, 3, 4, 5, 6 Herein, we describe a strategy that directly addresses this gap in synthetic methodology and present a single-flask catalytic enantioselective conversion of terminal alkenes into a range of chiral products. These reactions are enabled by an unusual neighboring group participation effect that accelerates Pd-catalyzed cross-coupling of 1,2-bis(boronates) relative to nonfunctionalized alkyl boronate analogs. In tandem with enantioselective diboration, this reactivity feature connects abundant alkene starting materials to a diverse array of chiral products. Importantly with respect to synthesis utility, the tandem diboration/cross-coupling reaction (DCC reaction) generally provides products in high yield and high selectivity (>95:5 enantiomer ratio), employs low loadings (1–2 mol %) of commercially available catalysts and reagents, it offers an expansive substrate scope, and can address a broad range of alcohol and amine synthesis targets, many of which cannot be easily addressed with current technology. PMID:24352229

  14. Ruthenium-Catalyzed Cross-Coupling of Maleimides with Alkenes.

    PubMed

    Morita, Tomohiro; Akita, Mitsutoshi; Satoh, Tetsuya; Kakiuchi, Fumitoshi; Miura, Masahiro

    2016-09-16

    The cross-coupling of maleimides with electron-deficient alkenes such as acrylates proceeds smoothly under ruthenium catalysis. This unique C-C coupling provides a simple, straightforward synthetic method for preparing alkylidene succinimide derivatives. PMID:27571229

  15. Catalytic, Stereoselective Dihalogenation of Alkenes: Challenges and Opportunities.

    PubMed

    Cresswell, Alexander J; Eey, Stanley T-C; Denmark, Scott E

    2015-12-21

    Although recent years have witnessed significant advances in the development of catalytic, enantioselective halofunctionalizations of alkenes, the related dihalogenation of olefins to afford enantioenriched vicinal dihalide products remains comparatively underdeveloped. However, the growing number of complex natural products bearing halogen atoms at stereogenic centers has underscored this critical gap in the synthetic chemist's arsenal. This Review highlights the selectivity challenges inherent in the design of enantioselective dihalogenation processes, and formulates a mechanism-based classification of alkene dihalogenations, including those that may circumvent the "classical" haliranium (or alkene-dihalogen π-complex) intermediates. A variety of metal and main group halide reagents that have been used for the dichlorination or dibromination of alkenes are discussed, and the proposed mechanisms of these transformations are critically evaluated.

  16. Biocompatible enzymatic roller pens for direct writing of biocatalytic materials: "do-it-yourself" electrochemical biosensors.

    PubMed

    Bandodkar, Amay J; Jia, Wenzhao; Ramírez, Julian; Wang, Joseph

    2015-06-01

    The development of enzymatic-ink-based roller pens for direct drawing of biocatalytic sensors, in general, and for realizing renewable glucose sensor strips, in particular, is described. The resulting enzymatic-ink pen allows facile fabrication of high-quality inexpensive electrochemical biosensors of any design by the user on a wide variety of surfaces having complex textures with minimal user training. Unlike prefabricated sensors, this approach empowers the end user with the ability of "on-demand" and "on-site" designing and fabricating of biocatalytic sensors to suit their specific requirement. The resulting devices are thus referred to as "do-it-yourself" sensors. The bio-active pens produce highly reproducible biocatalytic traces with minimal edge roughness. The composition of the new enzymatic inks has been optimized for ensuring good biocatalytic activity, electrical conductivity, biocompati-bility, reproducible writing, and surface adherence. The resulting inks are characterized using spectroscopic, viscometric, electrochemical, thermal and microscopic techniques. Applicability to renewable blood glucose testing, epidermal glucose monitoring, and on-leaf phenol detection are demonstrated in connection to glucose oxidase and tyrosinase-based carbon inks. The "do-it-yourself" renewable glucose sensor strips offer a "fresh," reproducible, low-cost biocatalytic sensor surface for each blood test. The ability to directly draw biocatalytic conducting traces even on unconventional surfaces opens up new avenues in various sensing applications in low-resource settings and holds great promise for diverse healthcare, environmental, and defense domains. PMID:25721554

  17. Biocompatible enzymatic roller pens for direct writing of biocatalytic materials: "do-it-yourself" electrochemical biosensors.

    PubMed

    Bandodkar, Amay J; Jia, Wenzhao; Ramírez, Julian; Wang, Joseph

    2015-06-01

    The development of enzymatic-ink-based roller pens for direct drawing of biocatalytic sensors, in general, and for realizing renewable glucose sensor strips, in particular, is described. The resulting enzymatic-ink pen allows facile fabrication of high-quality inexpensive electrochemical biosensors of any design by the user on a wide variety of surfaces having complex textures with minimal user training. Unlike prefabricated sensors, this approach empowers the end user with the ability of "on-demand" and "on-site" designing and fabricating of biocatalytic sensors to suit their specific requirement. The resulting devices are thus referred to as "do-it-yourself" sensors. The bio-active pens produce highly reproducible biocatalytic traces with minimal edge roughness. The composition of the new enzymatic inks has been optimized for ensuring good biocatalytic activity, electrical conductivity, biocompati-bility, reproducible writing, and surface adherence. The resulting inks are characterized using spectroscopic, viscometric, electrochemical, thermal and microscopic techniques. Applicability to renewable blood glucose testing, epidermal glucose monitoring, and on-leaf phenol detection are demonstrated in connection to glucose oxidase and tyrosinase-based carbon inks. The "do-it-yourself" renewable glucose sensor strips offer a "fresh," reproducible, low-cost biocatalytic sensor surface for each blood test. The ability to directly draw biocatalytic conducting traces even on unconventional surfaces opens up new avenues in various sensing applications in low-resource settings and holds great promise for diverse healthcare, environmental, and defense domains.

  18. Alkene dihydroxylation with malonoyl peroxides: catalysis using fluorinated alcohols.

    PubMed

    Picon, Sylvain; Rawling, Michael; Campbell, Matthew; Tomkinson, Nicholas C O

    2012-12-21

    The effect of fluorinated alcohols on the dihydroxylation of alkenes using cyclopropyl malonoyl peroxide is described. Addition of perfluoro-tert-butyl alcohol to a toluene solution of alkene and peroxide increases the rate of product formation and the stereoselectivity observed, providing a simple and effective method for acceleration of this important class of reaction. Basic hydrolysis of the crude reaction mixture provides access to syn-diols in high yield and stereoselectivity.

  19. Hydroaminations of alkenes: a radical, revised, and expanded version.

    PubMed

    Villa, Matteo; Jacobi von Wangelin, Axel

    2015-10-01

    Radical changes: The applicability of alkene hydroamination has recently been significantly expanded by the development of radical variants that are based on initial hydrogen atom transfer to the alkene. This Highlight assesses the current state of the art, focusing on an iron-catalyzed reaction that utilizes stable nitroarenes as the electrophilic N component and is based on the dual catalytic activation of both starting materials.

  20. Microfluidic multi-input reactor for biocatalytic synthesis using transketolase.

    PubMed

    Lawrence, James; O'Sullivan, Brian; Lye, Gary J; Wohlgemuth, Roland; Szita, Nicolas

    2013-11-01

    Biocatalytic synthesis in continuous-flow microreactors is of increasing interest for the production of specialty chemicals. However, the yield of production achievable in these reactors can be limited by the adverse effects of high substrate concentration on the biocatalyst, including inhibition and denaturation. Fed-batch reactors have been developed in order to overcome this problem, but no continuous-flow solution exists. We present the design of a novel multi-input microfluidic reactor, capable of substrate feeding at multiple points, as a first step towards overcoming these problems in a continuous-flow setting. Using the transketolase-(TK) catalysed reaction of lithium hydroxypyruvate (HPA) and glycolaldehyde (GA) to l-erythrulose (ERY), we demonstrate the transposition of a fed-batch substrate feeding strategy to our microfluidic reactor. We obtained a 4.5-fold increase in output concentration and a 5-fold increase in throughput compared with a single input reactor.

  1. Experimental determination of thermodynamic equilibrium in biocatalytic transamination.

    PubMed

    Tufvesson, Pär; Jensen, Jacob S; Kroutil, Wolfgang; Woodley, John M

    2012-08-01

    The equilibrium constant is a critical parameter for making rational design choices in biocatalytic transamination for the synthesis of chiral amines. However, very few reports are available in the scientific literature determining the equilibrium constant (K) for the transamination of ketones. Various methods for determining (or estimating) equilibrium have previously been suggested, both experimental as well as computational (based on group contribution methods). However, none of these were found suitable for determining the equilibrium constant for the transamination of ketones. Therefore, in this communication we suggest a simple experimental methodology which we hope will stimulate more accurate determination of thermodynamic equilibria when reporting the results of transaminase-catalyzed reactions in order to increase understanding of the relationship between substrate and product molecular structure on reaction thermodynamics.

  2. Regio- and stereoselective synthesis of pregnane-fused isoxazolines by nitril-oxide/alkene 1,3-dipolar cycloaddition and an evaluation of their cell-growth inhibitory effect in vitro

    NASA Astrophysics Data System (ADS)

    Mótyán, Gergő; Baji, Ádám; Zupkó, István; Frank, Éva

    2016-04-01

    Efficient syntheses of some pregnane-fused isoxazolines from 16-dehydropregnenolone acetate with different arylnitrile oxides were carried out by 1,3-dipolar cycloadditions. The intermolecular ring-closures occurred in a highly regio- and stereoselective manner permitting the formation of a single 16α,17α-condensed diastereomer in which the O terminus of the nitrile oxide dipole is attached to C-17 of the sterane core. The conversions were found to be affected significantly by the electronic character of the substituents on the aromatic moiety of the 1,3-dipoles. Deacetylation of the primary products resulted in the corresponding 3β-OH analogs. All of the synthesized compounds were subjected to in vitro pharmacological studies for the determination of their antiproliferative effects on four breast cancer cell lines (MCF7, T47D, MDA-MB-231 and MDA-MB-361).

  3. Biocatalytically induced growth of gold nanoshells: using enzyme reaction for the controllable fabrication of nanomaterials.

    PubMed

    Ma, Xiaoyuan; Liu, Liangliang; Liu, Fangjing; Qian, Weiping

    2012-02-01

    In the present work, the enzymatically controlled growth process of gold nanoshells (GNSs) in the presence of O2/glucose/glucose oxidase (GOx) and its chloroaurate ion electron acceptor is described. The biocatalytically stimulated growth process is one of the bio-inspired synthetic procedures directed by biological molecules which occur under ambient conditions. It is found that hydrogen peroxide (H2O2) could enlarge the gold nanoparticles (GNPs) on the surface of GNSs precursor composites, of which the preadsorbed GNPs serve as nucleation sites for further gold deposition. Here, GOx is harnessed for its unparalled level of catalytic activity and substrate specificity while H2O2 is produced as a by-product during the oxidation of D-glucose to gluconic acid by GOx. Then the bio-generated H2O2 is used as the reducing agent in the catalytic deposition process of GNSs formation. During the procedure, the localized surface plasmon resonance peaks range across hundreds of nanometers from visible to near infrared region accompanying by the resultant formation of uniform and continuous core-shell nanostructures. The corresponding optical, morphological and enzyme kinetic properties are all well investigated. The novel protocol offers a new perspective for the bio-directed synthesis method in nanotechnology. PMID:22629867

  4. Enzyme-Modified Particles for Selective Biocatalytic Hydrogenation by Hydrogen-Driven NADH Recycling

    PubMed Central

    Reeve, Holly A; Lauterbach, Lars; Lenz, Oliver; Vincent, Kylie A

    2015-01-01

    We describe a new approach to selective H2-driven hydrogenation that exploits a sequence of enzymes immobilised on carbon particles. We used a catalyst system that comprised alcohol dehydrogenase, hydrogenase and an NAD+ reductase on carbon black to demonstrate a greater than 98 % conversion of acetophenone to phenylethanol. Oxidation of H2 by the hydrogenase provides electrons through the carbon for NAD+ reduction to recycle the NADH cofactor required by the alcohol dehydrogenase. This biocatalytic system operates over the pH range 6–8 or in un-buffered water, and can function at low concentrations of the cofactor (10 μm NAD+) and at H2 partial pressures below 1 bar. Total turnover numbers >130 000 during acetophenone reduction indicate high enzyme stability, and the immobilised enzymes can be recovered by a simple centrifugation step and re-used several times. This offers a route to convenient, atom-efficient operation of NADH-dependent oxidoreductases for selective hydrogenation catalysis. PMID:26613009

  5. Manganese(IV)-mediated hydroperoxyarylation of alkenes with aryl hydrazines and dioxygen from air.

    PubMed

    Kindt, Stephanie; Jasch, Hannelore; Heinrich, Markus R

    2014-05-19

    We report a new carbooxygenation-type version of the Meerwein arylation in which the introduction of oxygen is achieved by using dioxygen from the air. In this way, hydroperoxides were obtained from activated as well as non-activated alkenes by oxidizing aryl hydrazines with manganese dioxide. The best results were obtained with α-substituted acrylates. Importantly, the aryl hydrazine has to be added slowly to the reaction mixture to allow sufficient uptake of dioxygen from the air. Competition and labeling experiments revealed hydroperoxyl radicals as novel oxygen-centered radical scavengers. PMID:24737215

  6. Osmium(III) and osmium(V) complexes bearing a macrocyclic ligand: a simple and efficient catalytic system for cis-dihydroxylation of alkenes with hydrogen peroxide.

    PubMed

    Sugimoto, Hideki; Ashikari, Kenji; Itoh, Shinobu

    2013-09-01

    A simple protocol that uses [Os(III)(OH)(H2O)(L-N4Me2)](PF6)2 (1; L-N4Me2 = N,N'-dimethyl-2,11-diaza[3.3](2,6)pyridinophane) as a catalyst and H2O2 as a terminal oxidant for efficient cis-1,2-dihydroxylation of alkenes is presented. Unfunctionalized (or aliphatic) alkenes and alkenes/styrenes containing electron-withdrawing groups are selectively oxidized to the corresponding vicinal diols in good to excellent yields (46-99 %). In the catalytic reactions, the stoichiometry of alkene:H2O2 is 1:1, and thus the oxidant efficiency is very high. For the dihydroxylation of cyclohexene, the catalytic amount of 1 can be reduced to 0.01 mol % to achieve a very high turnover number of 5500. The active oxidant is identified as the Os(V)(O)(OH) species (2), which is formed via the hydroperoxide adduct, an Os(III)(OOH) species. The active oxidant 2 is successfully isolated and crystallographically characterized.

  7. Copper Nitrate Mediated Regioselective [2+2+1] Cyclization of Alkynes with Alkenes: A Cascade Approach to Δ(2)-Isoxazolines.

    PubMed

    Gao, Mingchun; Li, Yingying; Gan, Yuansheng; Xu, Bin

    2015-07-20

    An efficient method for the regioselective synthesis of pharmacologically relevant polysubstituted Δ(2)-isoxazolines is based on the copper-mediated direct transformation of simple terminal alkynes and alkenes. The overall process involves the formation of four chemical bonds with inexpensive and readily available copper nitrate trihydrate as a novel precursor of nitrile oxides. The reaction can be easily handled and proceeds under mild conditions.

  8. Determining the Impact of Ligand and Alkene Substituents on Bonding in Gold(I)-Alkene Complexes Supported by N-Heterocyclic Carbenes: A Computational Study.

    PubMed

    York, John T

    2016-08-01

    The nature of the gold(I)-alkene bond in [(NHC)Au(alkene)](+) complexes (where NHC is the N-heterocyclic carbene 1,3-bis(2,6-dimethylphenyl)imidazole-2-ylidine and its derivatives) has been studied using density functional theory. By utilization of a series of electron-withdrawing and electron-donating substituents ranging from -NO2 to -NH2, an examination of substituent effects has been undertaken with 4-substituted NHC ligands, monosubstituted ethylene derivatives, and 4-substituted styrene derivatives. Natural population, natural bond orbital (NBO), molecular orbital, and bond energy decomposition analysis (EDA) methods have been used to quantify a number of important parameters, including the charge of the coordinated alkenes and the magnitude of alkene→[(NHC)Au](+) and [(NHC)Au](+)→alkene electron donation. EDA methods have also been used to quantify the strength of the [(NHC)Au](+)-(alkene) bond and the impact of both ligand and alkene substitution on different components of the interaction, including polarization, orbital, electrostatic, and Pauli repulsive contributions. Finally, molecular orbital analysis has been used to understand the activation of the alkenes in terms of orbital composition and stabilization within the [(NHC)Au(alkene)](+) complexes relative to the free alkenes. These results provide important insight into the fundamental nature of gold(I)-alkene bonding and the impact of both ligand and alkene substitution on the electronic structure of these complexes. PMID:27455390

  9. Determining the Impact of Ligand and Alkene Substituents on Bonding in Gold(I)-Alkene Complexes Supported by N-Heterocyclic Carbenes: A Computational Study.

    PubMed

    York, John T

    2016-08-01

    The nature of the gold(I)-alkene bond in [(NHC)Au(alkene)](+) complexes (where NHC is the N-heterocyclic carbene 1,3-bis(2,6-dimethylphenyl)imidazole-2-ylidine and its derivatives) has been studied using density functional theory. By utilization of a series of electron-withdrawing and electron-donating substituents ranging from -NO2 to -NH2, an examination of substituent effects has been undertaken with 4-substituted NHC ligands, monosubstituted ethylene derivatives, and 4-substituted styrene derivatives. Natural population, natural bond orbital (NBO), molecular orbital, and bond energy decomposition analysis (EDA) methods have been used to quantify a number of important parameters, including the charge of the coordinated alkenes and the magnitude of alkene→[(NHC)Au](+) and [(NHC)Au](+)→alkene electron donation. EDA methods have also been used to quantify the strength of the [(NHC)Au](+)-(alkene) bond and the impact of both ligand and alkene substitution on different components of the interaction, including polarization, orbital, electrostatic, and Pauli repulsive contributions. Finally, molecular orbital analysis has been used to understand the activation of the alkenes in terms of orbital composition and stabilization within the [(NHC)Au(alkene)](+) complexes relative to the free alkenes. These results provide important insight into the fundamental nature of gold(I)-alkene bonding and the impact of both ligand and alkene substitution on the electronic structure of these complexes.

  10. Intramolecular Alkene Aminocarbonylation Using Concerted Cycloadditions of Amino-Isocyanates.

    PubMed

    Ivanovich, Ryan A; Clavette, Christian; Vincent-Rocan, Jean-François; Roveda, Jean-Grégoire; Gorelsky, Serge I; Beauchemin, André M

    2016-06-01

    The ubiquity of nitrogen heterocycles in biologically active molecules challenges synthetic chemists to develop a variety of tools for their construction. While developing metal-free hydroamination reactions of hydrazine derivatives, it was discovered that carbazates and semicarbazides can also lead to alkene aminocarbonylation products if nitrogen-substituted isocyanates (N-isocyanates) are formed in situ as reactive intermediates. At first this reaction required high temperatures (150-200 °C), and issues included competing hydroamination and N-isocyanate dimerization pathways. Herein, improved conditions for concerted intramolecular alkene aminocarbonylation with N-isocyanates are reported. The use of βN-benzyl carbazate precursors allows the effective minimization of N-isocyanate dimerization. Diminished dimerization leads to higher yields of alkene aminocarbonylation products, to reactivity at lower temperatures, and to an improved scope for a reaction sequence involving alkene aminocarbonylation followed by 1,2-migration of the benzyl group. Furthermore, fine-tuning of the blocking (masking) group on the N-isocyanate precursor, and reaction conditions relying on base catalysis for N-isocyanate formation from simpler precursors resulted in room temperature reactivity, consequently minimizing the competing hydroamination pathway. Collectively, this work highlights that controlled reactivity of aminoisocyanates is possible, and provides a broadly applicable alkene aminocarbonylation approach to heterocycles possessing the β-aminocarbonyl motif. PMID:27112602

  11. Intramolecular Alkene Aminocarbonylation Using Concerted Cycloadditions of Amino-Isocyanates.

    PubMed

    Ivanovich, Ryan A; Clavette, Christian; Vincent-Rocan, Jean-François; Roveda, Jean-Grégoire; Gorelsky, Serge I; Beauchemin, André M

    2016-06-01

    The ubiquity of nitrogen heterocycles in biologically active molecules challenges synthetic chemists to develop a variety of tools for their construction. While developing metal-free hydroamination reactions of hydrazine derivatives, it was discovered that carbazates and semicarbazides can also lead to alkene aminocarbonylation products if nitrogen-substituted isocyanates (N-isocyanates) are formed in situ as reactive intermediates. At first this reaction required high temperatures (150-200 °C), and issues included competing hydroamination and N-isocyanate dimerization pathways. Herein, improved conditions for concerted intramolecular alkene aminocarbonylation with N-isocyanates are reported. The use of βN-benzyl carbazate precursors allows the effective minimization of N-isocyanate dimerization. Diminished dimerization leads to higher yields of alkene aminocarbonylation products, to reactivity at lower temperatures, and to an improved scope for a reaction sequence involving alkene aminocarbonylation followed by 1,2-migration of the benzyl group. Furthermore, fine-tuning of the blocking (masking) group on the N-isocyanate precursor, and reaction conditions relying on base catalysis for N-isocyanate formation from simpler precursors resulted in room temperature reactivity, consequently minimizing the competing hydroamination pathway. Collectively, this work highlights that controlled reactivity of aminoisocyanates is possible, and provides a broadly applicable alkene aminocarbonylation approach to heterocycles possessing the β-aminocarbonyl motif.

  12. Combinatorial metabolic engineering of Saccharomyces cerevisiae for terminal alkene production.

    PubMed

    Chen, Binbin; Lee, Dong-Yup; Chang, Matthew Wook

    2015-09-01

    Biological production of terminal alkenes has garnered a significant interest due to their industrial applications such as lubricants, detergents and fuels. Here, we engineered the yeast Saccharomyces cerevisiae to produce terminal alkenes via a one-step fatty acid decarboxylation pathway and improved the alkene production using combinatorial engineering strategies. In brief, we first characterized eight fatty acid decarboxylases to enable and enhance alkene production. We then increased the production titer 7-fold by improving the availability of the precursor fatty acids. We additionally increased the titer about 5-fold through genetic cofactor engineering and gene expression tuning in rich medium. Lastly, we further improved the titer 1.8-fold to 3.7 mg/L by optimizing the culturing conditions in bioreactors. This study represents the first report of terminal alkene biosynthesis in S. cerevisiae, and the abovementioned combinatorial engineering approaches collectively increased the titer 67.4-fold. We envision that these approaches could provide insights into devising engineering strategies to improve the production of fatty acid-derived biochemicals in S. cerevisiae.

  13. Oxidative Reactions with Nonaqueous Enzymes

    SciTech Connect

    Jonathan S. Dordick; Douglas Clark; Brian H Davison; Alexander Klibanov

    2001-12-30

    The objective of this work is to demonstrate a proof-of-concept of enzymatic oxidative processing in nonaqueous media using alkene epoxidation and phenolic polymerization as relevant targets. This project will provide both the fundamental and applied investigations necessary to initiate the implementation of oxidative biocatalysts as commercially relevant alternatives to chemical processing in general, and to phenolic polymerizations and alkene epoxidation specifically. Thus, this work will address the Bioprocessing Solicitation Area to: (1) makes major improvements to phenolic polymerization and alkene epoxidation technologies; (2) is expected to be cost competitive with competing conventional processes; and (3) produces higher yields with less waste.

  14. Intramolecular Aminocyanation of Alkenes via N–CN Bond Cleavage**

    PubMed Central

    Pan, Zhongda; Pound, Sarah M.; Rondla, Naveen R.; Douglas, Christopher J.

    2014-01-01

    A metal-free, Lewis acid-promoted intramolecular aminocyanation of alkenes was developed. B(C6F5)3 activates N-sulfonyl cyanamides, leading an formal cleavage of the N-CN bonds in conjunction with vicinal addition of sulfonamide and nitrile groups across an alkene. This method enables atom-economical access to indolines and tetrahydroquinolines in excellent yields, and provides a complementary strategy for regioselective alkene difunctionalizations with sulfonamide and nitrile groups. Labeling experiments with 13C suggest a fully intramolecular cyclization pattern due to lack of label scrambling in double crossover experiments. Catalysis with Lewis acid is realized and the reaction can be conducted under air. PMID:24719371

  15. Alkanes and alkenes conversion to high octane gasoline

    SciTech Connect

    Harandi, M.N.; Owen, H.

    1989-07-25

    This patent describes a process for the conversion of lower alkane and alkene hydrocarbons to high octane gasoline. It comprises: contacting a hydrocarbon feedstock comprising lower alkanes and alkenes with a fluidized bed of acidic, shape selective metallosiliate catalyst in a first conversion zone under high temperature alkane conversion conditions wherein the feedstock contains an amount of lower alkene sufficient to provide an exotherm sufficient to maintain near isothermal reaction conditions whereby an effluent stream is produced comprising higher aliphatic hydrocarbons rich in aromatics; contacting the effluent stream with a fluidized bed of acidic, medium pore metallosilicate catalyst in a second conversion zone at moderate temperature under oligonerization and alkylation conditions whereby a C/sub 5/ + gasoline boiling range product is produced rich in alkylated aromatics.

  16. Biocatalytic potential of vanillin aminotransferase from Capsicum chinense

    PubMed Central

    2014-01-01

    Background The conversion of vanillin to vanillylamine is a key step in the biosynthetic route towards capsaicinoids in pungent cultivars of Capsicum sp. The reaction has previously been annotated to be catalysed by PAMT (putative aminotransferase; [GenBank: AAC78480.1, Swiss-Prot: O82521]), however, the enzyme has previously not been biochemically characterised in vitro. Results The biochemical activity of the transaminase was confirmed by direct measurement of the reaction with purified recombinant enzyme. The enzyme accepted pyruvate, and oxaloacetate but not 2-oxoglutarate as co-substrate, which is in accordance with other characterised transaminases from the plant kingdom. The enzyme was also able to convert (S)-1-phenylethylamine into acetophenone with high stereo-selectivity. Additionally, it was shown to be active at a broad pH range. Conclusions We suggest PAMT to be renamed to VAMT (vanillin aminotransferase, abbreviation used in this study) as formation of vanillin from vanillylamine could be demonstrated. Furthermore, due to high stereoselectivity and activity at physiological pH, VAMT is a suitable candidate for biocatalytic transamination in a recombinant whole-cell system. PMID:24712445

  17. Effectiveness Factors and Conversion in a Biocatalytic Membrane Reactor

    PubMed Central

    Godongwana, Buntu

    2016-01-01

    Analytical expressions of the effectiveness factor of a biocatalytic membrane reactor, and its asymptote as the Thiele modulus becomes large, are presented. The evaluation of the effectiveness factor is based on the solution of the governing equations for solute transport in the two regions of the reactor, i.e. the lumen and the matrix (with the biofilm immobilized in the matrix). The lumen solution accounts for both axial diffusion and radial convective flow, while the matrix solution is based on Robin-type boundary conditions. The effectiveness factor is shown to be a function of the Thiele modulus, the partition coefficient, the Sherwood number, the Peclet number, and membrane thickness. Three regions of Thiele moduli are defined in the effectiveness factor graphs. These correspond with reaction rate limited, internal-diffusion limited, and external mass transfer limited solute transport. Radial convective flows were shown to only improve the effectiveness factor in the region of internal diffusion limitation. The assumption of first order kinetics is shown to be applicable only in the Thiele modulus regions of internal and external mass transfer limitation. An iteration scheme is also presented for estimating the effectiveness factor when the solute fractional conversion is known. The model is validated with experimental data from a membrane gradostat reactor immobilised with Phanerochaete chrysosporium for the production of lignin and manganese peroxidases. The developed model and experimental data allow for the determination of the Thiele modulus at which the effectiveness factor and fractional conversion are optimal. PMID:27104954

  18. The mechanism for iron-catalyzed alkene isomerization in solution

    SciTech Connect

    Sawyer, Karma R.; Glascoe, Elizabeth A.; Cahoon, James F.; Schlegel, Jacob P.; Harris, Charles B.

    2008-05-27

    Here we report nano- through microsecond time-resolved IR experiments of iron-catalyzed alkene isomerization in room-temperature solution. We have monitored the photochemistry of a model system, Fe(CO){sub 4}({eta}{sup 2}-1-hexene), in neat 1-hexene solution. UV-photolysis of the starting material leads to the dissociation of a single CO to form Fe(CO){sub 3}({eta}{sup 2}-1-hexene), in a singlet spin state. This CO loss complex shows a dramatic selectivity to form an allyl hydride, HFe(CO){sub 3}({eta}{sup 3}-C{sub 6}H{sub 11}), via an internal C-H bond-cleavage reaction in 5-25 ns. We find no evidence for the coordination of an alkene molecule from the bath to the CO loss complex, but do observe coordination to the allyl hydride, indicating that it is the key intermediate in the isomerization mechanism. Coordination of the alkene ligand to the allyl hydride leads to the formation of the bis-alkene isomers, Fe(CO){sub 3}({eta}{sup 2}-1-hexene)({eta}{sup 2}-2-hexene) and Fe(CO){sub 3}({eta}{sup 2}-1-hexene){sub 2}. Because of the thermodynamic stability of Fe(CO){sub 3}({eta}{sup 2}-1-hexene)({eta}{sup 2}-2-hexene) over Fe(CO){sub 3}({eta}{sup 2}-1-hexene){sub 2} (ca. 12 kcal/mol), nearly 100% of the alkene population will be 2-alkene. The results presented herein provide the first direct evidence for this mechanism in solution and suggest modifications to the currently accepted mechanism.

  19. New osmium-based reagent for the dihydroxylation of alkenes.

    PubMed

    Donohoe, Timothy J; Harris, Robert M; Butterworth, Sam; Burrows, Jeremy N; Cowley, Andrew; Parker, Jeremy S

    2006-06-01

    The cis dihydroxylation of alkenes is most efficiently accomplished by reaction with osmium tetroxide. Recently, the expense and toxicity of osmium tetroxide have led to a number of attempts to harness alternative osmium-based reagents, including microencapsulation and solid support techniques. We describe here the development of a new nonvolatile, stable, and recoverable osmium-based reagent devised for the stoichiometric cis dihydroxylation of alkenes. Although attempts to make this new dihydroxylation work with catalytic amounts of this reagent were unsuccessful, we did develop a sensitive test for free osmium tetroxide leached from the reagent in situ: this test may well have uses in probing future applications of derivatized osmium reagents.

  20. Alkenes with antioxidative activities from Murraya koenigii (L.) Spreng.

    PubMed

    Ma, Qin-Ge; Xu, Kun; Sang, Zhi-Pei; Wei, Rong-Rui; Liu, Wen-Min; Su, Ya-Lun; Yang, Jian-Bo; Wang, Ai-Guo; Ji, Teng-Fei; Li, Lu-Jun

    2016-02-01

    Four new alkenes (1-4), and six known alkenes (5-12) were isolated from Murraya koenigii (L.) Spreng. Their structures were elucidated on the basis of spectroscopic analyses and references. Compounds (1-12) were evaluated for antioxidative activities. Among them, compounds 1, 2, 4, and 7 exhibited significant antioxidative activities using 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay with IC50=21.4-49.5 μM. The known compounds (5-12) were isolated from this plant for the first time.

  1. Synthesis and characterization of supported heteropolymolybdate nanoparticles between silicate layers of Bentonite with enhanced catalytic activity for epoxidation of alkenes

    SciTech Connect

    Salavati, Hossein; Rasouli, Nahid

    2011-11-15

    Highlights: {yields} The PVMo and nanocomposite catalyst (PVMo/Bentonite) as catalyst for epoxidation of alkenes. {yields} The composite catalyst showed higher catalytic activity than parent heteropolymolybdate (PVMo). {yields}The use of ultrasonic irradiation increased the conversions and reduced the reaction times. {yields} The H{sub 2}O{sub 2} is a green and eco-friendly oxidant in this catalytic system. -- Abstract: A new heterogeneous catalyst (PVMo/Bentonite) consisting of vanadium substituted heteropolymolybdate with Keggin-type structure Na{sub 5}[PV{sub 2}Mo{sub 10}O{sub 40}].14H{sub 2}O (PVMo) supported between silicate layers of bentonite has been synthesized by impregnation method and characterized using X-ray diffraction, Fourier-transformed infrared spectroscopy, scanning electron microscopy, UV-vis diffuse reflectance spectroscopy, transmission electron microscopy and elemental analysis. X-ray diffraction and scanning electron microscopy analysis indicated that PVMo was finely dispersed into layers of bentonite as support. The PVMo/Bentonite used as an efficient heterogeneous catalyst for epoxidation of alkenes. Various cyclic and linear alkenes were oxidized into the corresponding epoxides in high yields and selectivity with 30% aqueous H{sub 2}O{sub 2}. The catalyst was reused several times, without observable loss of activity and selectivity. The obtained results showed that the catalytic activity of the PVMo/Bentonite was higher than that of pure heteropolyanion (PVMo).

  2. Use of a batch-stirred reactor to rationally tailor biocatalytic polytransesterification

    SciTech Connect

    Kline, B.J.; Lele, S.S.; Lenart, P.J.; Beckman, E.J.; Russell, A.J.

    2000-02-20

    Despite favorable thermodynamics, high-molecular weight and low-dispersity polyesters are difficult to synthesize biocatalytically in organic solvents. The authors have reported previously that the elimination of solvent can improve the kinetics and apparent equilibrium significantly. The authors now present the design and use of a batch-stirred enzyme reactor to control the biocatalytic polymerization. Using the rector, polyester having a molecular weight of 23,400 Da and a polydispersity of 1.69 was synthesized in only 1 h at 60 C. Additional factors like enzyme-deactivation kinetics, enzyme specificity, and initial exothermicity were investigated to develop a better understanding of this complex reaction system.

  3. Hydroxy-alkenals from the peroxidation of n-3 and n-6 fatty acids and urinary metabolites.

    PubMed

    Guichardant, M; Bacot, S; Molière, P; Lagarde, M

    2006-09-01

    4-Hydroxy-2E-hexenal (4-HHE) and 4-hydroxy-2E-nonenal (4-HNE) have been characterized as prominent by-products of n-3 and n-6 hydroperoxy derivatives of n-3 and n-6 fatty acids, respectively. We also have characterized the homolog 4-hydroxy-2E,6Z-dodecadienal (4-HDDE) as a specific by-product of the 12-lipoxygenase product of arachidonic acid 12-hydroperoxy-eicosatetraenoate (12-HpETE). The three hydroxy-alkenals have been found in human plasma with 4-HHE being the most prominent followed by 4-HNE. They were found increased in tissues submitted to oxidative stress, according to the fatty acid characteristic of those tissues, e.g., 4-HNE and 4-HDDE in blood platelets and 4-HHE in the retina. We have shown they covalently bind to the primary amine moiety of ethanolamine phospholipids (PE), especially the plasmalogen subclass, with the highest hydrophobic alkenal (4-HDDE) being the most reactive. Their carboxylic acid metabolites, 4-hydroxy-2E-hexenoic acid (4-HHA), 4-hydroxy-2E-nonenoic acid (4-HNA) and 4-hydroxy-2E,6Z-dodecadienoic acid (4-HDDA), respectively, were found in human urine and measured in higher amounts in situations in which oxidative stress has been reported such as aging and diabetes. As reported above with their hydroxy-alkenals precursors, 4-HHA proved to be the most prominent followed by 4-HNA. Altogether, the three hydroxy-alkenals, either in their free form or bound to membrane PE, may be considered as specific markers of lipid peroxidation able to discriminate between n-3 and n-6 fatty acids. This is corroborated by the measurement of their urinary carboxylic acid metabolites.

  4. The syn/anti-Dichotomy in the Palladium-Catalyzed Addition of Nucleophiles to Alkenes

    PubMed Central

    Kočovský, Pavel; Bäckvall, Jan-E

    2015-01-01

    In this review the stereochemistry of palladium-catalyzed addition of nucleophiles to alkenes is discussed, and examples of these reactions in organic synthesis are given. Most of the reactions discussed involve oxygen and nitrogen nucleophiles; the Wacker oxidation of ethylene has been reviewed in detail. An anti-hydroxypalladation in the Wacker oxidation has strong support from both experimental and computational studies. From the reviewed material it is clear that anti-addition of oxygen and nitrogen nucleophiles is strongly favored in intermolecular addition to olefin–palladium complexes even if the nucleophile is coordinated to the metal. On the other hand, syn-addition is common in the case of intramolecular oxy- and amidopalladation as a result of the initial coordination of the internal nucleophile to the metal. PMID:25378278

  5. Heuristical Strategies on the Study Theme "The Unsaturated Hydrocarbons -- Alkenes"

    ERIC Educational Resources Information Center

    Naumescu, Adrienne Kozan; Pasca, Roxana-Diana

    2011-01-01

    The influence of heuristical strategies upon the level of two experimental classes is studied in this paper. The didactic experiment took place at secondary school in Cluj-Napoca, in 2008-2009 school year. The study theme "The Unsaturated Hydrocarbons--Alkenes" has been efficiently learned by using the most active methods: laboratory…

  6. Increased functionality of methyl oleate using alkene metathesis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A series of alkene cross metathesis reactions were performed using a homogeneous ruthenium based catalyst. Using this technology, a variety of functional groups can be incorporated into the biobased starting material, methyl oleate. Trans-stilbene, styrene, methyl cinnamate and hexen-3-ol were all s...

  7. An Easily Accessed Nickel Nanoparticle Catalyst for Alkene Hydrosilylation with Tertiary Silanes.

    PubMed

    Buslov, Ivan; Song, Fang; Hu, Xile

    2016-09-26

    The first efficient and non-precious nanoparticle catalyst for alkene hydrosilylation with commercially relevant tertiary silanes has been developed. The nickel nanoparticle catalyst was prepared in situ from a simple nickel alkoxide precatalyst Ni(O(t) Bu)2 ⋅x KCl. The catalyst exhibits high activity for anti-Markovnikov hydrosilylation of unactivated terminal alkenes and isomerizing hydrosilylation of internal alkenes. The catalyst can be applied to synthesize a single terminal alkyl silane from a mixture of internal and terminal alkene isomers, and to remotely functionalize an internal alkene derived from a fatty acid. PMID:27612210

  8. Evidence for significant C-5 alkene emissions from car traffic

    NASA Astrophysics Data System (ADS)

    Schade, G. W.; Park, C.

    2010-12-01

    We present evidence from urban flux tower measurements in Houston, Texas, that a five carbon alkene, likely isoprene, is emitted from car traffic. Our GC-dual FID instrument setup measures VOC concentrations at 60 m above ground level from a lattice flux tower, and determines fluxes via a novel relaxed eddy accumulation technique. C-5 2-alkenes and isoprene, 2-methyl-1,3-butadiene, are not chromatographically separated by our method, but past VOC measurements suggest that isoprene, a biogenic hydrocarbon, generally dominates during the growing season. Our measured 2008 summertime C-5 alkene fluxes generally followed the expected, light and temperature driven emission pattern of isoprene from a significant density of oak trees in the tower’s footprint area. However, nighttime fluxes were significantly different from an expected zero biogenic flux, and morning rush hour fluxes were significantly higher than modeled biogenic fluxes. Wintertime measurements in January 2009 confirmed a small flux during the morning rush-hour was maintained, suggesting either an isoprene or C-5 2-alkene emission from car exhaust. While isoprene emissions from car traffic have been found several times before, emission rates have been found negligibly small compared to biogenic emissions. A quantitative comparison of our data to simultaneously measured toluene and benzene emissions however suggests that these C-5 alkene emissions may have increased relative to aromatics by a factor of ten since the 1990s. This notion is supported both by recent direct car exhaust measurements in Europe and Japan, and airborne isoprene measurements over Houston. Car exhaust measurements show that (i) the isoprene to toluene emission ratio for the newest car models is now around 1:10, similar to the ratio obtained from our data, and (ii) cold start alkene emissions are still an order of magnitude higher than regular emissions, consistent with a more prominent morning rush hour peak. If the identity of our

  9. Cloning, Expression, Characterization, and Biocatalytic Investigation of the 4-Hydroxyacetophenone Monooxygenase from Pseudomonas putida JD1▿ †

    PubMed Central

    Rehdorf, Jessica; Zimmer, Christian L.; Bornscheuer, Uwe T.

    2009-01-01

    While the number of available recombinant Baeyer-Villiger monooxygenases (BVMOs) has grown significantly over the last few years, there is still the demand for other BVMOs to expand the biocatalytic diversity. Most BVMOs that have been described are dedicated to convert efficiently cyclohexanone and related cyclic aliphatic ketones. To cover a broader range of substrate types and enantio- and/or regioselectivities, new BVMOs have to be discovered. The gene encoding a BVMO identified in Pseudomonas putida JD1 converting aromatic ketones (HAPMO; 4-hydroxyacetophenone monooxygenase) was amplified from genomic DNA using SiteFinding-PCR, cloned, and functionally expressed in Escherichia coli. Furthermore, four other open reading frames could be identified clustered around this HAPMO. It has been suggested that these proteins, including the HAPMO, might be involved in the degradation of 4-hydroxyacetophenone. Substrate specificity studies revealed that a large variety of other arylaliphatic ketones are also converted via Baeyer-Villiger oxidation into the corresponding esters, with preferences for para-substitutions at the aromatic ring. In addition, oxidation of aldehydes and some heteroaromatic compounds was observed. Cycloketones and open-chain ketones were not or poorly accepted, respectively. It was also found that this enzyme oxidizes aromatic ketones such as 3-phenyl-2-butanone with excellent enantioselectivity (E ≫100). PMID:19251889

  10. Laboratory spectroscopic analyses of electron irradiated alkanes and alkenes in solar system ices

    NASA Astrophysics Data System (ADS)

    Hand, K. P.; Carlson, R. W.

    2012-03-01

    We report results from laboratory experiments of 10 keV electron irradiation of thin ice films of water and short-chain hydrocarbons at ˜10-8 Torr and temperatures ranging from 70-100 K. Hydrocarbon mixtures include water with C3H8, C3H6, C4H10 (butane and isobutane), and C4H8, (1-butene and cis/trans-2-butene). The double bonds of the alkenes in our initial mixtures were rapidly destroyed or converted to single carbon bonds, covalent bonds with hydrogen, bonds with -OH (hydroxyl), bonds with oxygen (C-O), or double bonds with oxygen (carbonyl). Spectra resulting from irradiation of alkane and alkene ices are largely indistinguishable; the initial differences in film composition are destroyed and the resulting mixture includes long-chain, branched aliphatics, aldehydes, ketones, esters, and alcohols. Methane was observed as a product during radiolysis but CO was largely absent. We find that while some of the carbon is oxidized and lost to CO2 formation, some carbon is sequestered into highly refractory, long-chain aliphatic compounds that remain as a thin residue even after the ice film has been raised to standard temperature and pressure. We conclude that the high availability of hydrogen in our experiments leads to the formation of the formyl radical which then serves as the precursor for formaldehyde and polymerization of longer hydrocarbon chains.

  11. Mechanistic Insight into the Photoredox Catalysis of Anti-Markovnikov Alkene Hydrofunctionalization Reactions

    PubMed Central

    2015-01-01

    We describe our efforts to understand the key mechanistic aspects of the previously reported alkene hydrofunctionalization reactions using 9-mesityl-10-methylacridinium (Mes-Acr+) as a photoredox catalyst. Importantly, we are able to detect alkene cation radical intermediates, and confirm that phenylthiyl radical is capable of oxidizing the persistent acridinyl radical in a fast process that unites the catalytic activity of the photoredox and hydrogen atom transfer (HAT) manifolds. Additionally, we present evidence that diphenyl disulfide ((PhS)2) operates on a common catalytic cycle with thiophenol (PhSH) by way of photolytic cleaveage of the disulfide bond. Transition structure analysis of the HAT step using DFT reveals that the activation barrier for H atom donation from PhSH is significantly lower than 2-phenylmalononitrile (PMN) due to structural reorganization. In the early stages of the reaction, Mes-Acr+ is observed to engage in off-cycle adduct formation, presumably as buildup of PhS− becomes significant. The kinetic differences between PhSH and (PhS)2 as HAT catalysts indicate that the proton transfer step may have significant rate limiting influence. PMID:25390821

  12. Structure-Odor Relationships of (E)-3-Alkenoic Acids, (E)-3-Alken-1-ols, and (E)-3-Alkenals.

    PubMed

    Lorber, Katja; Buettner, Andrea

    2015-08-01

    (E)-3-Unsaturated volatile acids, alcohols, and aldehydes are commonly found as odorants or pheromones in foods and other natural sources, playing a vital role in not only the attractiveness of foods but also chemo-communication in the animal kingdom. However, a systematic elucidation of their aroma properties, especially for humans, has not been carried out until today. To close this gap, the odor thresholds in air and odor qualities of homologous series of (E)-3-alkenoic acids, (E)-3-alken-1-ols, and (E)-3-alkenals were determined by gas chromatography-olfactometry. In the series of (E)-3-alkenoic acids the odor quality changed successively from sweaty via plastic-like to sweaty and waxy. On the other hand, the odor qualities in the series of (E)-3-alken-1-ols and (E)-3-alkenals changed from grassy, green to an overall citrus-like, fresh, soapy, and coriander-like odor with increasing chain length. With regard to their odor potencies, the lowest thresholds in air were found for (E)-3-heptenoic acid, (E)-3-hexenoic acid, and (E)-3-hexenal. PMID:26165743

  13. Cobalt-Catalyzed [2π + 2π] Cycloadditions of Alkenes: Scope, Mechanism, and Elucidation of Electronic Structure of Catalytic Intermediates.

    PubMed

    Schmidt, Valerie A; Hoyt, Jordan M; Margulieux, Grant W; Chirik, Paul J

    2015-06-24

    Aryl-substituted bis(imino)pyridine cobalt dinitrogen compounds, ((R)PDI)CoN2, are effective precatalysts for the intramolecular [2π + 2π] cycloaddition of α,ω-dienes to yield the corresponding bicyclo[3.2.0]heptane derivatives. The reactions proceed under mild thermal conditions with unactivated alkenes, tolerating both amine and ether functional groups. The overall second order rate law for the reaction, first order with respect to both the cobalt precatalyst and the substrate, in combination with electron paramagnetic resonance (EPR) spectroscopic studies established the catalyst resting state as dependent on the identity of the precatalyst and diene substrate. Planar S = ½ κ(3)-bis(imino)pyridine cobalt alkene and tetrahedral κ(2)-bis(imino)pyridine cobalt diene complexes were observed by EPR spectroscopy and in the latter case structurally characterized. The hemilabile chelate facilitates conversion of a principally ligand-based singly occupied molecular orbital (SOMO) in the cobalt dinitrogen and alkene compounds to a metal-based SOMO in the diene intermediates, promoting C-C bond-forming oxidative cyclization. Structure-activity relationships on bis(imino)pyridine substitution were also established with 2,4,6-tricyclopentyl-substituted aryl groups, resulting in optimized catalytic [2π + 2π] cycloaddition. The cyclopentyl groups provide a sufficiently open metal coordination sphere that encourages substrate coordination while remaining large enough to promote a challenging, turnover-limiting C(sp(3))-C(sp(3)) reductive elimination. PMID:26030841

  14. Cobalt-Catalyzed [2π + 2π] Cycloadditions of Alkenes: Scope, Mechanism, and Elucidation of Electronic Structure of Catalytic Intermediates.

    PubMed

    Schmidt, Valerie A; Hoyt, Jordan M; Margulieux, Grant W; Chirik, Paul J

    2015-06-24

    Aryl-substituted bis(imino)pyridine cobalt dinitrogen compounds, ((R)PDI)CoN2, are effective precatalysts for the intramolecular [2π + 2π] cycloaddition of α,ω-dienes to yield the corresponding bicyclo[3.2.0]heptane derivatives. The reactions proceed under mild thermal conditions with unactivated alkenes, tolerating both amine and ether functional groups. The overall second order rate law for the reaction, first order with respect to both the cobalt precatalyst and the substrate, in combination with electron paramagnetic resonance (EPR) spectroscopic studies established the catalyst resting state as dependent on the identity of the precatalyst and diene substrate. Planar S = ½ κ(3)-bis(imino)pyridine cobalt alkene and tetrahedral κ(2)-bis(imino)pyridine cobalt diene complexes were observed by EPR spectroscopy and in the latter case structurally characterized. The hemilabile chelate facilitates conversion of a principally ligand-based singly occupied molecular orbital (SOMO) in the cobalt dinitrogen and alkene compounds to a metal-based SOMO in the diene intermediates, promoting C-C bond-forming oxidative cyclization. Structure-activity relationships on bis(imino)pyridine substitution were also established with 2,4,6-tricyclopentyl-substituted aryl groups, resulting in optimized catalytic [2π + 2π] cycloaddition. The cyclopentyl groups provide a sufficiently open metal coordination sphere that encourages substrate coordination while remaining large enough to promote a challenging, turnover-limiting C(sp(3))-C(sp(3)) reductive elimination.

  15. Enantioselective Oxidative Rearrangements with Chiral Hypervalent Iodine Reagents

    PubMed Central

    Brown, Michael; Kumar, Ravi; Rehbein, Julia

    2016-01-01

    Abstract A stereoselective hypervalent iodine‐promoted oxidative rearrangement of 1,1‐disubstituted alkenes has been developed. This practically simple protocol provides access to enantioenriched α‐arylated ketones without the use of transition metals from readily accessible alkenes. PMID:26800241

  16. Alkene metathesis - a tool for the synthesis of conjugated polymers.

    PubMed

    Bunz, Uwe H F; Mäker, Dominic; Porz, Michael

    2012-05-29

    Alkene metathesis is a superb methodology. We report the progress using alkene metathesis in the synthesis of polymeric organic semiconductors. Three classes of polymers have been synthesized using acyclic diene metathesis (ADMET) or ring opening metathesis polymerization (ROMP), viz., poly(acetylene)s (PA), poly(arylene-vinylene)s (PAV), and organometallic polymers. For PAs, ROMP of cyclooctatetraenes is best, whereas for PAV, both ADMET and indirect and direct ROMP are viable. Metathesis performs flawlessly with the correct monomers, as molybdenum and particularly the robust Ru carbenes demonstrate. When performing ROMP, one is often rewarded with structurally uniform polymers that can display very low polydispersities. Overall, metathesis is a powerful tool for the preparation of semiconducting polymers.

  17. Highly Selective Phosphinylphosphination of Alkenes with Tetraphenyldiphosphine Monoxide.

    PubMed

    Sato, Yuki; Kawaguchi, Shin-Ichi; Nomoto, Akihiro; Ogawa, Akiya

    2016-08-01

    In sharp contrast to tetraphenyldiphosphine, which does not add to carbon-carbon double bonds efficiently, its monoxide, [Ph2 P(O)PPh2 ] can engage in a radical addition to various alkenes, thus affording the corresponding 1-phosphinyl-2-phosphinoalkanes regioselectively, and they can be converted into their sulfides by treatment with elemental sulfur. The phosphinylphosphination proceeds by the homolytic cleavage of the P(V) (O)-P(III) single bond of Ph2 P(O)PPh2 , followed by selective attack of the phosphinyl radical at the terminal position of the alkenes, and selective trapping of the resulting carbon radical by the phosphino group. Furthermore, the phosphinylphosphination product could be converted directly into its platinum complex with a hemilabile P,O chelation. PMID:27374767

  18. Thermal functionalization of GaN surfaces with 1-alkenes.

    PubMed

    Schwarz, Stefan U; Cimalla, Volker; Eichapfel, Georg; Himmerlich, Marcel; Krischok, Stefan; Ambacher, Oliver

    2013-05-28

    A thermally induced functionalization process for gallium nitride surfaces with 1-alkenes is introduced. The resulting functionalization layers are characterized with atomic force microscopy and X-ray photoelectron spectroscopy and compared to reference samples without and with a photochemically generated functionalization layer. The resulting layers show very promising characteristics as functionalization for GaN based biosensors. On the basis of the experimental results, important characteristics of the functionalization layers are estimated and a possible chemical reaction scheme is proposed. PMID:23617559

  19. Palladium Catalyzed Intramolecular Acylcyanation of Alkenes Using α-Iminonitriles

    PubMed Central

    Rondla, Naveen R.; Ogilvie, Jodi M.; Pan, Zhongda

    2014-01-01

    Reported here is a palladium catalyzed intramolecular acylcyanation of alkenes using α-iminonitriles. Through this method, highly functionalized indanones are synthesized in moderate to high yields using Pd(PPh3)4, without need for any additional ligands, and a common Lewis acid (ZnCl2). Additionally, the reaction tolerates substitution at various positions on the aromatic ring including electron donating, and electron withdrawing groups. PMID:24980625

  20. Alkene Metathesis and Renewable Materials: Selective Transformations of Plant Oils

    NASA Astrophysics Data System (ADS)

    Malacea, Raluca; Dixneuf, Pierre H.

    The olefin metathesis of natural oils and fats and their derivatives is the basis of clean catalytic reactions relevant to green chemistry processes and the production of generate useful chemicals from renewable raw materials. Three variants of alkene metathesis: self-metathesis, ethenolysis and cross-metathesis applied to plant oil derivatives will show new routes to fine chemicals, bifunctional products, polymer precursours and industry intermediates.

  1. Regioselective, Asymmetric Formal Hydroamination of Unactivated Internal Alkenes.

    PubMed

    Xi, Yumeng; Butcher, Trevor W; Zhang, Jing; Hartwig, John F

    2016-01-11

    We report the regioselective and enantioselective formal hydroamination of unsymmetrical internal alkenes catalyzed by a copper catalyst ligated by DTBM-SEGPHOS. The regioselectivity of the reaction is controlled by the electronic effects of ether, ester, and sulfonamide groups in the homoallylic position. The observed selectivity underscores the influence of inductive effects of remote substituents on the selectivity of catalytic processes occurring at hydrocarbyl groups, and the method provides direct access to various 1,3-aminoalcohol derivatives with high enantioselectivity. PMID:26592363

  2. Ultrasensitive photoelectrochemical immunoassay of antibody against tumor-associated carbohydrate antigen amplified by functionalized graphene derivates and enzymatic biocatalytic precipitation.

    PubMed

    Zhang, Xiaoru; Liu, Mingshuai; Mao, Yaning; Xu, Yunpeng; Niu, Shuyan

    2014-09-15

    Tumor-associated carbohydrate antigens (TACAs) are often found on the surface of cancer cells. The determination of the carbohydrate components of glycoconjugates is challenging because of the chemical complexity of glycan chains. Through monitoring corresponding antibody, we can get a good solution for clinical diagnosis. Here breast tumor-associated carbohydrate antigens Tn were used as a model and a new photoelectrochemical biosensor for ultrasensitive detection of antibody against Tn was developed. To enhance the sensitivity, both graphene oxide and graphene were used during the construction of biosensor. Through the formation of immunocomplex and the insoluble biocatalytic precipitation (BCP) product, photocurrent intensity was decreased greatly and the antibody could be detected from 0.5 to 500 pg/mL with a detection limit of 1.0×10(-13) g/mL. At the same time, the developed biosensor showed acceptable selectivity and could be used in the complex matrix. Compared with the traditional glycoarray method, this PEC method is more sensitive (5 orders of magnitude), and thus provides another platform to monitor the immune response to carbohydrate epitopes at different stages during differentiation, metastasis, or treatment.

  3. Spectroscopic and biocatalytic properties of a chlorophyll-containing extract in silica gel

    NASA Astrophysics Data System (ADS)

    Lipke, Agnieszka; Trytek, Mariusz; Fiedurek, Jan; Majdan, Marek; Janik, Ewa

    2013-11-01

    UV-Vis absorption and fluorescence spectra of chlorophyll a (in the form of spinach extract) in acetone solution and in silica gel showed a predominance of pigment dimers in its overall concentration and an evident transformation of chlorophyll a to pheophytin with time. The dimerization constant of chlorophyll a in acetone was log Kdim = 2.14, whereas the constants for chlorophyll a and pheophytin a in alcogel were log Kdim = 4.70 and log Kdim = 5.22, respectively. Biocatalytic experiments indicated the possibility of using the pigment embedded in silica gel, i.e. mainly its dimeric form, for biotransformation of α-pinene to pinocarveyl hydroperoxide, trans-pinocarveol, pinocarvone and myrtenal. The advantage of a heterogeneous biocatalytic system (composed of a solvent and silica gel) over a homogeneous system (single phase of chloroform) is the possibility of reusing the biocatalyst with about 10% preservation of its activity.

  4. Recent achievements in developing the biocatalytic toolbox for chiral amine synthesis.

    PubMed

    Kohls, Hannes; Steffen-Munsberg, Fabian; Höhne, Matthias

    2014-04-01

    Novel enzyme activities and chemoenzymatic reaction concepts have considerably expanded the biocatalytic toolbox for chiral amine synthesis. Creating new activities or extending the scope of existing enzymes by protein engineering is a common trend in biocatalysis and in chiral amine synthesis specifically. For instance, an amine dehydrogenase that allows for the direct asymmetric amination of ketones with ammonia was created by mutagenesis of an l-amino acid dehydrogenase. Another trend in chiral amine chemistry is the development of strategies allowing for the synthesis of secondary amines. For example the smart choice of substrates for amine transaminases provided access to secondary amines by chemoenzymatic reactions. Furthermore novel biocatalysts for the synthesis of secondary amines such as imine reductases and Pictet-Spenglerases have been identified and applied. Recent examples showed that the biocatalytic amine synthesis is emerging from simple model reactions towards industrial scale preparation of pharmaceutical relevant substances, for instance, as shown in the synthesis of a Janus kinase 2 inhibitor using an amine transaminase. A comparison of important process parameters such as turnover number and space-time yield demonstrates that biocatalytic strategies for asymmetric reductive amination are maturing and can already compete with established chemical methods. PMID:24721252

  5. Copper-catalyzed stereoselective aminoboration of bicyclic alkenes.

    PubMed

    Sakae, Ryosuke; Hirano, Koji; Satoh, Tetsuya; Miura, Masahiro

    2015-01-01

    A copper-catalyzed aminoboration of bicyclic alkenes, including oxa- and azabenzonorbornadienes, has been developed. With this method, amine and boron moieties are simultaneously introduced at an olefin with exo selectivity. Subsequent stereospecific transformations of the boryl group can provide oxygen- and nitrogen-rich cyclic molecules with motifs that may be found in natural products or pharmaceutically active compounds. Moreover, a catalytic asymmetric variant of this transformation was realized by using a copper complex with a chiral bisphosphine ligand, namely (R,R)-Ph-BPE. PMID:25404258

  6. A biocompatible alkene hydrogenation merges organic synthesis with microbial metabolism.

    PubMed

    Sirasani, Gopal; Tong, Liuchuan; Balskus, Emily P

    2014-07-21

    Organic chemists and metabolic engineers use orthogonal technologies to construct essential small molecules such as pharmaceuticals and commodity chemicals. While chemists have leveraged the unique capabilities of biological catalysts for small-molecule production, metabolic engineers have not likewise integrated reactions from organic synthesis with the metabolism of living organisms. Reported herein is a method for alkene hydrogenation which utilizes a palladium catalyst and hydrogen gas generated directly by a living microorganism. This biocompatible transformation, which requires both catalyst and microbe, and can be used on a preparative scale, represents a new strategy for chemical synthesis that combines organic chemistry and metabolic engineering.

  7. A Biocompatible Alkene Hydrogenation Merges Organic Synthesis with Microbial Metabolism**

    PubMed Central

    Sirasani, Gopal; Tong, Liuchuan; Balskus, Emily P.

    2014-01-01

    Organic chemists and metabolic engineers use largely orthogonal technologies to construct essential small molecules like pharmaceuticals and commodity chemicals. While chemists have leveraged the unique capabilities of biological catalysts for small molecule production, metabolic engineers have not likewise integrated reactions from organic synthesis with the metabolism of living organisms. Here we report a method for alkene hydrogenation that utilizes a palladium catalyst and hydrogen gas generated directly by a living microorganism. This biocompatible transformation, which requires both catalyst and microbe and can be used on a preparative scale, represents a new strategy for chemical synthesis that combines organic chemistry and metabolic engineering. PMID:24916924

  8. Copper-catalyzed stereoselective aminoboration of bicyclic alkenes.

    PubMed

    Sakae, Ryosuke; Hirano, Koji; Satoh, Tetsuya; Miura, Masahiro

    2015-01-01

    A copper-catalyzed aminoboration of bicyclic alkenes, including oxa- and azabenzonorbornadienes, has been developed. With this method, amine and boron moieties are simultaneously introduced at an olefin with exo selectivity. Subsequent stereospecific transformations of the boryl group can provide oxygen- and nitrogen-rich cyclic molecules with motifs that may be found in natural products or pharmaceutically active compounds. Moreover, a catalytic asymmetric variant of this transformation was realized by using a copper complex with a chiral bisphosphine ligand, namely (R,R)-Ph-BPE.

  9. Modular Synthesis of Pyrazolones Using an Alkene Aminocarbonylation Reaction.

    PubMed

    Lavergne, Kaitlyn; Bongers, Amanda; Betit, Lyanne; Beauchemin, André M

    2015-07-17

    A variety of pyrazolones were synthesized from enol ethers and hydrazones using a reaction sequence involving aminocarbonylation of enol ethers followed by nucleophile-induced aromatization of the azomethine imines intermediates. Using bases to catalyze the in situ formation of imino isocyanates allowed alkene aminocarbonylation to proceed under milder conditions with reactive substrates and enabled aminocarbonylation reactions of sensitive enol ethers. Aromatization of the azomethine imines could be induced by reduction using NaBH4, or by addition of NH2OH to afford the parent (β)N-H products. PMID:26126788

  10. Efficient epoxidation of a terminal alkene containing allylic hydrogen atoms: trans-methylstyrene on Cu{111}.

    PubMed

    Cropley, Rachael L; Williams, Federico J; Urquhart, Andrew J; Vaughan, Owain P H; Tikhov, Mintcho S; Lambert, Richard M

    2005-04-27

    The selective oxidation of trans-methylstyrene, a phenyl-substituted propene that contains labile allylic hydrogen atoms, has been studied on Cu{111}. Mass spectrometry and synchrotron fast XPS were used to detect, respectively, desorbing gaseous products and the evolution of surface species as a function of temperature and time. Efficient partial oxidation occurs yielding principally the epoxide, and the behavior of the system is sensitive to the order in which reactants are adsorbed. The latter is understandable in terms of differences in the spatial distribution of oxygen adatoms; isolated adatoms lead to epoxidation, while islands of "oxidic" oxygen do not. NEXAFS data taken over a range of coverages and in the presence and absence of coadsorbed oxygen indicate that the adsorbed alkene lies essentially flat with the allylic hydrogen atoms close to the surface. The photoemission results and comparison with the corresponding behavior of styrene on Cu{111} strongly suggest that allylic hydrogen abstraction is indeed a critical factor that limits epoxidation selectivity. An overall mechanism consistent with the structural and reactive properties is proposed.

  11. Cobalt-catalyzed C-H olefination of aromatics with unactivated alkenes.

    PubMed

    Manoharan, Ramasamy; Sivakumar, Ganesan; Jeganmohan, Masilamani

    2016-08-18

    A cobalt-catalyzed C-H olefination of aromatic and heteroaromatic amides with unactivated alkenes, allyl acetates and allyl alcohols is described. This method offers an efficient route for the synthesis of vinyl and allyl benzamides in a highly stereoselective manner. It is observed that the ortho substituent on the benzamide moiety is crucial for the observation of allylated products in unactivated alkenes.

  12. Osmium-catalyzed vicinal oxyamination of alkenes by N-(4-toluenesulfonyloxy)carbamates.

    PubMed

    Masruri; Willis, Anthony C; McLeod, Malcolm D

    2012-10-01

    N-(4-toluenesulfonyloxy)carbamates based on a range of common amine protecting groups serve as preformed nitrogen sources in the intermolecular osmium-catalyzed oxyamination reaction of a variety of mono-, di-, and trisubstituted alkenes. The reactions occur with low catalyst loadings and good yields and afford high regioselectivity for unsymmetrically substituted alkenes.

  13. Combination of a Cyano Migration Strategy and Alkene Difunctionalization: The Elusive Selective Azidocyanation of Unactivated Olefins.

    PubMed

    Wu, Zhen; Ren, Rongguo; Zhu, Chen

    2016-08-26

    A conceptually new, efficient, and metal-free approach for the challenging azidocyanation of unactivated alkenes is presented. The strategy of intramolecular distal cyano migration is combined with alkene difunctionalization for the first time. A variety of useful azido-substituted alkyl nitriles are prepared in good yields and, most importantly, with exquisite regio- and stereo-selectivities.

  14. Well-Defined and Robust Rhodium Catalysts for the Hydroacylation of Terminal and Internal Alkenes**

    PubMed Central

    Prades, Amparo; Fernández, Maitane; Pike, Sebastian D; Willis, Michael C; Weller, Andrew S

    2015-01-01

    A Rh-catalyst system based on the asymmetric ligand tBu2PCH2P(o-C6H4OMe)2 is reported that allows for the hydroacylation of challenging internal alkenes with β-substituted aldehydes. Mechanistic studies point to the stabilizing role of both excess alkene and the OMe-group. PMID:26069052

  15. Copper-catalyzed trifluoromethylation of alkenes with an electrophilic trifluoromethylating reagent

    PubMed Central

    Wang, Xiao-Ping; Lin, Jin-Hong; Zhang, Cheng-Pan; Zheng, Xing

    2013-01-01

    Summary An efficient method for the copper-catalyzed trifluoromethylation of terminal alkenes with an electrophilic trifluoromethylating reagent has been developed. The reactions proceeded smoothly to give trifluoromethylated alkenes in good to excellent yields. The results provided a versatile approach for the construction of Cvinyl–CF3 bonds without using prefunctionalized substrates. PMID:24367428

  16. 40 CFR 721.4464 - Mixture of hydrofluoro alkanes and hydrofluoro alkene.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Mixture of hydrofluoro alkanes and... Specific Chemical Substances § 721.4464 Mixture of hydrofluoro alkanes and hydrofluoro alkene. (a) Chemical... as a mixture of hydrofluoro alkanes and hydrofluoro alkene (PMNs P-96-945/946/947/948) are subject...

  17. 40 CFR 721.4464 - Mixture of hydrofluoro alkanes and hydrofluoro alkene.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Mixture of hydrofluoro alkanes and... Specific Chemical Substances § 721.4464 Mixture of hydrofluoro alkanes and hydrofluoro alkene. (a) Chemical... as a mixture of hydrofluoro alkanes and hydrofluoro alkene (PMNs P-96-945/946/947/948) are subject...

  18. 40 CFR 721.4464 - Mixture of hydrofluoro alkanes and hydrofluoro alkene.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Mixture of hydrofluoro alkanes and... Specific Chemical Substances § 721.4464 Mixture of hydrofluoro alkanes and hydrofluoro alkene. (a) Chemical... as a mixture of hydrofluoro alkanes and hydrofluoro alkene (PMNs P-96-945/946/947/948) are subject...

  19. 40 CFR 721.4464 - Mixture of hydrofluoro alkanes and hydrofluoro alkene.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Mixture of hydrofluoro alkanes and... Specific Chemical Substances § 721.4464 Mixture of hydrofluoro alkanes and hydrofluoro alkene. (a) Chemical... as a mixture of hydrofluoro alkanes and hydrofluoro alkene (PMNs P-96-945/946/947/948) are subject...

  20. 40 CFR 721.4464 - Mixture of hydrofluoro alkanes and hydrofluoro alkene.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Mixture of hydrofluoro alkanes and... Specific Chemical Substances § 721.4464 Mixture of hydrofluoro alkanes and hydrofluoro alkene. (a) Chemical... as a mixture of hydrofluoro alkanes and hydrofluoro alkene (PMNs P-96-945/946/947/948) are subject...

  1. Enantioselective Intramolecular Hydroarylation of Alkenes via Directed C-H Bond Activation

    SciTech Connect

    Harada, Hitoshi; Thalji, Reema; Bergman, Robert; Ellman, Jonathan

    2008-05-22

    Highly enantioselective catalytic intramolecular ortho-alkylation of aromatic imines containing alkenyl groups tethered at the meta position relative to the imine directing group has been achieved using [RhCl(coe){sub 2}]{sub 2} and chiral phosphoramidite ligands. Cyclization of substrates containing 1,1- and 1,2-disubstituted as well as trisubstituted alkenes were achieved with enantioselectivities >90% ee for each substrate class. Cyclization of substrates with Z-alkene isomers proceeded much more efficiently than substrates with E-alkene isomers. This further enabled the highly stereoselective intramolecular alkylation of certain substrates containing Z/E-alkene mixtures via a Rh-catalyzed alkene isomerization with preferential cyclization of the Z-isomer.

  2. Highly efficient molybdenum-based catalysts for enantioselective alkene metathesis

    PubMed Central

    Malcolmson, Steven J.; Meek, Simon J.; Sattely, Elizabeth S.; Schrock, Richard R.; Hoveyda, Amir H.

    2009-01-01

    Discovery of efficient catalysts is one of the most compelling objectives of modern chemistry. Chiral catalysts are in particularly high demand, as they facilitate synthesis of enantiomerically enriched small molecules that are critical to developments in medicine, biology and materials science1. Especially noteworthy are catalysts that promote—with otherwise inaccessible efficiency and selectivity levels—reactions demonstrated to be of great utility in chemical synthesis. Here we report a class of chiral catalysts that initiate alkene metathesis1 with very high efficiency and enantioselectivity. Such attributes arise from structural fluxionality of the chiral catalysts and the central role that enhanced electronic factors have in the catalytic cycle. The new catalysts have a stereogenic metal centre and carry only monodentate ligands; the molybdenum-based complexes are prepared stereoselectively by a ligand exchange process involving an enantiomerically pure aryloxide, a class of ligands scarcely used in enantioselective catalysis2,3. We demonstrate the application of the new catalysts in an enantioselective synthesis of the Aspidosperma alkaloid, quebrachamine, through an alkene metathesis reaction that cannot be promoted by any of the previously reported chiral catalysts. PMID:19011612

  3. Biocatalytic synthesis of polycatechols from toxic aromatic compounds.

    PubMed

    Ward, Gary; Parales, Rebecca E; Dosoretz, Carlos G

    2004-09-15

    A process is described in which toxic aromatic compounds are converted by toluene dioxygenase and in turn toluene cis-dihydrodiol dehydrogenase to catechols which are further polymerized by peroxidase-catalyzed oxidation producing polycatechols. Three approaches for obtaining catechols were employed: (1) addition of halogenated aromatics to P. putida F1, resulting in the accumulation of halogenated catechols; (2) inhibition of catechol 2,3-dioxygenase of P. putida F1 by known aromatic and aliphatic inhibitors; and (3) overexpression of toluene dioxygenase and toluene cis-dihydrodiol dehydrogenase genes in E. coli JM109. The process is suitable for producing novel catechols that upon oxidation may yield polymers with unique properties, presenting a tool for producing tailor-made biopolymers. Formation of 3-chlorocatechol from chlorobenzene, 3,4-dichlorocatechol from 1,2-dichlorobenzene, and catechol from benzene and their subsequent oxidation and polymerization was demonstrated. Oxidation of catechol yielded polymers with molecular weights of up to 4000 Daltons. Their apparently high water solubility eliminates the need for water-miscible solvents. In aqueous solution oxidation of catechols was rapid, yet the presence of 20%, 30%, and 40% ethanol, resulted in a rate decrease of 31%, 95%, and 93%, respectively. The advantage is that significantly less peroxidase is required for performing the reactions if miscible solvents are not employed. Furthermore, water-soluble polymers may be desirable for many applications.

  4. Genes involved in long-chain alkene biosynthesis in Micrococcus luteus

    SciTech Connect

    Beller, Harry R.; Goh, Ee-Been; Keasling, Jay D.

    2010-01-07

    Aliphatic hydrocarbons are highly appealing targets for advanced cellulosic biofuels, as they are already predominant components of petroleum-based gasoline and diesel fuels. We have studied alkene biosynthesis in Micrococcus luteus ATCC 4698, a close relative of Sarcina lutea (now Kocuria rhizophila), which four decades ago was reported to biosynthesize iso- and anteiso branched, long-chain alkenes. The underlying biochemistry and genetics of alkene biosynthesis were not elucidated in those studies. We show here that heterologous expression of a three-gene cluster from M. luteus (Mlut_13230-13250) in a fatty-acid overproducing E. coli strain resulted in production of long-chain alkenes, predominantly 27:3 and 29:3 (no. carbon atoms: no. C=C bonds). Heterologous expression of Mlut_13230 (oleA) alone produced no long-chain alkenes but unsaturated aliphatic monoketones, predominantly 27:2, and in vitro studies with the purified Mlut_13230 protein and tetradecanoyl-CoA produced the same C27 monoketone. Gas chromatography-time of flight mass spectrometry confirmed the elemental composition of all detected long-chain alkenes and monoketones (putative intermediates of alkene biosynthesis). Negative controls demonstrated that the M. luteus genes were responsible for production of these metabolites. Studies with wild-type M. luteus showed that the transcript copy number of Mlut_13230-13250 and the concentrations of 29:1 alkene isomers (the dominant alkenes produced by this strain) generally corresponded with bacterial population over time. We propose a metabolic pathway for alkene biosynthesis starting with acyl-CoA (or -ACP) thioesters and involving decarboxylative Claisen condensation as a key step, which we believe is catalyzed by OleA. Such activity is consistent with our data and with the homology (including the conserved Cys-His-Asn catalytic triad) of Mlut_13230 (OleA) to FabH (?-ketoacyl-ACP synthase III), which catalyzes decarboxylative Claisen condensation during

  5. Reactions of volatile organic compounds in the atmosphere: Ozone-alkene reactions

    NASA Astrophysics Data System (ADS)

    Fenske, Jill Denise

    2000-08-01

    Photochemical smog cannot form without sunlight, nitrogen oxides, and volatile organic compounds (VOC). This dissertation addresses several different aspects of VOC chemistry in the atmosphere. Aside from ambient levels of VOC outdoors, VOC are also present at moderate concentrations indoors. Many studies have measured indoor air concentrations of VOC, but only one considered the effects of human breath. The major VOC in the breath of healthy individuals are isoprene (12-580 ppb), acetone (1.2-1800 ppb), ethanol (13-1000 ppb), methanol (160-2000 ppb), and other alcohols. Human emissions of VOC are negligible on a regional (less than 4%) and global scale (less than 0.3%). However, in indoor air, under fairly crowded situations, human emissions of VOC may dominate other sources of VOC. An important class of VOC in the atmosphere is alkenes, due to their high reactivity. The ozone reaction with alkenes forms OH radicals, a powerful oxidizing agent in the troposphere. OH radical formation yields from the ozonolysis of several cycloalkenes were measured using small amounts of fast-reacting aromatics and aliphatic ethers to trace OH formation. The values are 0.62 +/- 0.15, 0.54 +/- 0.13, 0.36 +/- 0.08, and 0.91 +/- 0.20 for cyclopentene, cyclohexene, cycloheptene and 1-methylcyclohexene, respectively. Density functional theory calculations at the B3LYP/6-31 G(d,p) level are presented to aid in understanding the trends observed. The pressure dependence of OH radical yields may lend insight into the formation mechanism. We have made the first study of the pressure dependence of the OH radical yield for ethene, propene, 1-butene, trans-2-butene, and 2,3-dimethyl-2- butene over the range 20-760 Torr, and trans -3-hexene, and cyclopentene over the range 200-760 Torr. The OH yields from ozonolysis of ethene and propene were pressure dependent, while the other compounds had OH yields that were independent of pressure. Ozone-alkene reactions form vibrationally excited carbonyl

  6. Thermal Reactions of Oxygen Atoms with Alkenes at Low Temperatures on Interstellar Dust

    NASA Astrophysics Data System (ADS)

    Ward, Michael D.; Price, Stephen D.

    2011-11-01

    Laboratory experiments show that the thermal heterogeneous reactions of oxygen atoms may contribute to the synthesis of epoxides in interstellar clouds. The data set also indicates that the contribution of these pathways to epoxide formation, in comparison to non-thermal routes, is likely to be strongly temperature dependent. Our results indicate that an increased abundance of epoxides, relative to the corresponding aldehydes, could be an observational signature of a significant contribution to molecular oxidation via thermal O atom reactions with alkenes. Specifically surface science experiments show that both C2H4O and C3H6O are readily formed from reactions of ethene and propene molecules with thermalized oxygen atoms at temperatures in the range of 12-90 K. It is clear from our experiments that these reactions, on a graphite surface, proceed with significantly reduced reaction barriers compared with those operating in the gas phase. For both the C2H4 + O and the C3H6 + O reactions, the surface reaction barriers we determine are reduced by approximately an order of magnitude compared with the barriers in the gas phase. The modeling of our experimental results, which determines these reaction barriers, also extracts desorption energies and rate coefficients for the title reactions. Our results clearly show that the major product from the O + C2H4 reaction is ethylene oxide, an epoxide.

  7. THERMAL REACTIONS OF OXYGEN ATOMS WITH ALKENES AT LOW TEMPERATURES ON INTERSTELLAR DUST

    SciTech Connect

    Ward, Michael D.; Price, Stephen D. E-mail: s.d.price@ucl.ac.uk

    2011-11-10

    Laboratory experiments show that the thermal heterogeneous reactions of oxygen atoms may contribute to the synthesis of epoxides in interstellar clouds. The data set also indicates that the contribution of these pathways to epoxide formation, in comparison to non-thermal routes, is likely to be strongly temperature dependent. Our results indicate that an increased abundance of epoxides, relative to the corresponding aldehydes, could be an observational signature of a significant contribution to molecular oxidation via thermal O atom reactions with alkenes. Specifically surface science experiments show that both C{sub 2}H{sub 4}O and C{sub 3}H{sub 6}O are readily formed from reactions of ethene and propene molecules with thermalized oxygen atoms at temperatures in the range of 12-90 K. It is clear from our experiments that these reactions, on a graphite surface, proceed with significantly reduced reaction barriers compared with those operating in the gas phase. For both the C{sub 2}H{sub 4} + O and the C{sub 3}H{sub 6} + O reactions, the surface reaction barriers we determine are reduced by approximately an order of magnitude compared with the barriers in the gas phase. The modeling of our experimental results, which determines these reaction barriers, also extracts desorption energies and rate coefficients for the title reactions. Our results clearly show that the major product from the O + C{sub 2}H{sub 4} reaction is ethylene oxide, an epoxide.

  8. An osmium(III)/osmium(V) redox couple generating Os(V)(O)(OH) center for cis-1,2-dihydroxylation of alkenes with H2O2: Os complex with a nitrogen-based tetradentate ligand.

    PubMed

    Sugimoto, Hideki; Kitayama, Kazuhiro; Mori, Seiji; Itoh, Shinobu

    2012-11-21

    For the synthesis of the 1,2-diols, cis-1,2-dihydroxylation of alkenes catalyzed by osmium(VIII) tetroxide (OsO(4)) is a powerful method. However, OsO(4) is quite toxic due to its highly volatile and sublimable nature. Thus, the development of alternative catalysts for cis-1,2-dihydroxylation of alkenes is highly challenging. Our approach involves the use of a nitrogen-based tetradentate ligand, tris(2-pyridylmethyl)amine (tpa), for an osmium center to develop a new osmium catalyst and hydrogen peroxide (H(2)O(2)) as a cheap and environmentally benign oxidant. The new Os-tpa complex acts as a very efficient turnover catalyst for syn-selective dihydroxylation of various alkenes (turnover number ∼1000) in aqueous media, and H(2)O(2) oxidant is formally incorporated into the products quantitatively (100% atom efficiency). The reaction intermediates involved in the catalytic cycle have been isolated and characterized crystallographically as [Os(III)(OH)(H(2)O)(tpa)](2+) and [Os(V)(O)(OH)(tpa)](2+) complexes. The observed syn-selectivity, structural characteristics of the intermediates, and kinetic studies have suggested a concerted [3 + 2]-cycloaddition mechanism between [Os(V)(O)(OH)(tpa)](2+) and alkenes, which is strongly supported by DFT calculations.

  9. Chemotherapy pro-drug activation by biocatalytic virus-like nanoparticles containing cytochrome P450.

    PubMed

    Sánchez-Sánchez, Lorena; Cadena-Nava, Rubén D; Palomares, Laura A; Ruiz-Garcia, Jaime; Koay, Melissa S T; Cornelissen, Jeroen J M T; Vazquez-Duhalt, Rafael

    2014-06-10

    This work shows, for the first time, the encapsulation of a highly relevant protein in the biomedical field into virus-like particles (VLPs). A bacterial CYP variant was effectively encapsulated in VLPs constituted of coat protein from cowpea chlorotic mottle virus (CCMV). The catalytic VLPs are able to transform the chemotherapeutic pro-drug, tamoxifen, and the emerging pro-drug resveratrol. The chemical nature of the products was identified, confirming similar active products than those obtained with human CYP. The enzymatic VLPs remain stable after the catalytic reaction. The potential use of these biocatalytic nanoparticles as targeted CYP carriers for the activation of chemotherapy drugs is discussed. PMID:24835096

  10. Towards biochemical filters with a sigmoidal response to pH changes: buffered biocatalytic signal transduction

    NASA Astrophysics Data System (ADS)

    Pita, Marcos; Privman, Vladimir; Arugula, Mary A.; Melnikov, Dmitriy; Bocharova, Vera; Katz, Evgeny

    We realize a biochemical filtering process by introducing a buffer in a biocatalytic signal-transduction logic system based on the function of an enzyme, esterase. The input, ethyl butyrate, is converted into butyric acid-the output signal, which in turn is measured by the drop in the pH value. The developed approach offers a versatile "network element" for increasing the complexity of biochemical information processing systems. Evaluation of an optimal regime for quality filtering is accomplished in the framework of a kinetic rate-equation model.

  11. Catalytic, Enantioselective Sulfenofunctionalisation of Alkenes: Mechanistic, Crystallographic, and Computational Studies

    PubMed Central

    Denmark, Scott E.; Hartmann, Eduard; Kornfilt, David J. P.; Wang, Hao

    2015-01-01

    The stereocontrolled introduction of vicinal heteroatomic substituents into organic molecules is one of the most powerful ways of adding value and function. Whereas many methods exist for the introduction of oxygen- and nitrogen-containing substituents, the number stereocontrolled methods for the introduction of sulfur-containing substituents pales by comparison. Previous reports from these laboratories have described the sulfenofunctionalization of alkenes that construct vicinal carbon-sulfur and carbon-oxygen, carbon-nitrogen as well as carbon-carbon bonds with high levels of diastereospecificity and enantioselectivity. This process is enabled by the concept of Lewis base activation of Lewis acids that provides activation of Group 16 electrophiles. To provide a foundation for expansion of substrate scope and improved selectivities, we have undertaken a comprehensive study of the catalytically active species. Insights gleaned from kinetic, crystallographic and computational methods have led to the introduction of a new family of sulfenylating agents that provide significantly enhanced selectivities. PMID:25411883

  12. Catalyst system for the polymerization of alkenes to polyolefins

    DOEpatents

    Miller, Stephen A.; Bercaw, John E.

    2004-02-17

    The invention provides metallocene catalyst systems for the controlled polymerization of alkenes to a wide variety of polyolefins and olefin coplymers. Catalyst systems are provided that specifically produce isotactic, syndiotactic and steroblock polyolefins. The type of polymer produced can be controlled by varying the catalyst system, specifically by varying the ligand substituents. Such catalyst systems are particularly useful for the polymerization of polypropylene to give elastomeric polypropylenes. The invention also provides novel elastomeric polypropylene polymers characterized by dyad (m) tacticities of about 55% to about 65%, pentad (mmmm) tacticities of about 25% to about 35%, molecular weights (M.sub.W) in the range of about 50,000 to about 2,000,000, and have mmrm+rrmr peak is less than about 5%.

  13. Catalyst system for the polymerization of alkenes to polyolefins

    DOEpatents

    Miller, Stephen A.; Bercaw, John E.

    2002-01-01

    The invention provides metallocene catalyst systems for the controlled polymerization of alkenes to a wide variety of polyolefins and olefin coplymers. Catalyst systems are provided that specifically produce isotactic, syndiotactic and steroblock polyolefins. The type of polymer produced can be controlled by varying the catalyst system, specifically by varying the ligand substituents. Such catalyst systems are particularly useful for the polymerization of polypropylene to give elastomeric polypropylenes. The invention also provides novel elastomeric polypropylene polymers characterized by dyad (m) tacticities of about 55% to about 65%, pentad (mmmm) tacticities of about 25% to about 35%, molecular weights (M.sub.w)in the range of about 50,000 to about 2,000,000, and have mmrm+rrmr peak is less than about 5%.

  14. New developments in gold-catalyzed manipulation of inactivated alkenes

    PubMed Central

    Chiarucci, Michel

    2013-01-01

    Summary Over the recent years, the nucleophilic manipulation of inactivated carbon–carbon double bonds has gained remarkable credit in the chemical community. As a matter of fact, despite lower reactivity with respect to alkynyl and allenyl counterparts, chemical functionalization of isolated alkenes, via carbon- as well as hetero atom-based nucleophiles, would provide direct access to theoretically unlimited added value of molecular motifs. In this context, homogenous [Au(I)] and [Au(III)] catalysis continues to inspire developments within organic synthesis, providing reliable responses to this interrogative, by combining crucial aspects such as chemical selectivity/efficiency with mild reaction parameters. This review intends to summarize the recent progresses in the field, with particular emphasis on mechanistic details. PMID:24367423

  15. Cofactor recycling mechanism in asymmetric biocatalytic reduction of carbonyl compounds mediated by yeast: which is the efficient electron donor?

    PubMed

    Zhang, Ben-Li; Pionnier, Sébastien

    2003-08-01

    In asymmetric reduction of carbonyl compounds mediated by microorganisms, the cofactors that transfer hydride should be regenerated by using a recycling system. In most cases, this recycling system consists of carbohydrate molecules, especially glucose or sucrose. Other molecules such as ethanol and acetate have been used as electron donors too. The reduction can even be conducted without added electron donors. To improve biocatalytic synthesis, it is important to understand the cofactor recycling mechanism. In this work, the hydride-transfer mechanism in cofactor regeneration, which takes place in bioreduction mediated by yeast, was studied by means of an isotope tracing technique. The results show that, when glucose was used, the NADH involved in the glycolysis was consumed directly in the formation of ethanol and was not used in the bioreduction. Hence, the regeneration of cofactors in the reduction is not coupled with glycolysis. Nevertheless, glucose is an efficient electron donor that transfers hydride through the hexose monophosphate (HMP) pathway in which the main hydrogen source is C-1 and C-3 hydrogen of glucose. Ethanol is not a good electron donor, since, when it was used, only a small quantity of hydrogen was transferred from this molecule, and the main hydrogen source was water. Therefore, the ethanol oxidation pathway may not be efficient. In the absence of added auxiliary substrates, the yeast cells may use electron donors stored in its cellules. However, in this case we observed that the main hydrogen source for cofactor recycling was water, while only very few hydrogen atoms were from unexchangeable sites. This is similar to the case in which ethanol is used, and is in contradiction with the HMP pathway if stored glucose was the electron donor. The question that remains to be investigated is "what is the efficient electron donor recycling mechanism in the yeast cellules?" PMID:12898687

  16. Tyramine-based enzymatic conjugate repeats for ultrasensitive immunoassay accompanying tyramine signal amplification with enzymatic biocatalytic precipitation.

    PubMed

    Hou, Li; Tang, Yun; Xu, Mingdi; Gao, Zhuangqiang; Tang, Dianping

    2014-08-19

    A new impedimetric immunoassay protocol based on enzyme-triggered formation of tyramine-enzyme repeats on gold nanoparticle (AuNP) was designed for highly sensitive detection of carcinoembryonic antigen (CEA, as a model) by virtue of utilizing enzymatic biocatalytic precipitation toward 4-chloro-1-naphthol (4-CN) on anti-CEA antibody (Ab1)-modified immunosensor. Initially, AuNP was functionalized with horseradish peroxidase and detection antibody (HRP-AuNP-Ab2), and then HRP-tyramine conjugate was utilized for the formation of tyramine-HRP repeats through the triggering of the immobilized HRP on the AuNP with the aid of H2O2. In the presence of target CEA, the carried HRP-tyramine repeats accompanying the sandwiched immunocomplex catalyzed the 4-CN oxidation to produce an insoluble precipitation on the immunosensor, thus causing a local alteration of the conductivity. Three signal-transduction tags including HRP-Ab2, HRP-AuNP-Ab2, and HRP-AuNP-Ab2 with HRP-tyramine repeats were employed for target CEA evaluation, and improved analytical properties were achieved by HRP-AuNP-Ab2 with HRP-tyramine repeats. Using the unique signal-transduction tag, the analytical performance of the impedimetric immunoassay was studied in detail. Under the optimal conditions, the impedimetric immunosensor displayed a wide dynamic working range of between 0.5 pg mL(-1) and 40 ng mL(-1) with a detection limit (LOD) of 0.38 pg mL(-1) relative to target CEA. The coefficients of variation (CVs) were ≤9.3% and 13.3% for the intra-assay and interassay, respectively. The levels of CEA in eight clinical serum specimens were measured by using the developed impedimetric immunosensor. The obtained results correlated well with those from the electrochemiluminescent (ECL)-based immunoassay with a correlation coefficient of 0.998.

  17. Tandem ring-closing metathesis/transfer hydrogenation: practical chemoselective hydrogenation of alkenes.

    PubMed

    Connolly, Timothy; Wang, Zhongyu; Walker, Michael A; McDonald, Ivar M; Peese, Kevin M

    2014-09-01

    An operationally simple chemoselective transfer hydrogenation of alkenes using ruthenium metathesis catalysts is presented. Of great practicality, the transfer hydrogenation reagents can be added directly to a metathesis reaction and effect hydrogenation of the product alkene in a single pot at ambient temperature without the need to seal the vessel to prevent hydrogen gas escape. The reduction is applicable to a range of alkenes and can be performed in the presence of aryl halides and benzyl groups, a notable weakness of Pd-catalyzed hydrogenations. Scope and mechanistic considerations are presented. PMID:25140991

  18. Maturation of tergal gland alkene profiles in European honey bee queens,Apis mellifera L.

    PubMed

    Smith, R K; Spivak, M; Taylor, O R; Bennett, C; Smith, M L

    1993-01-01

    In a series of husbandry and stop-time chemical experiments with honey bee queens, the production of tergal gland alkenes was found to be stimulated by natural mating and not by instrumental insemination. Carbon dioxide, physical manipulation of the sting chamber and vagina, presence of sperm in the spermatheca, egg production, and chemicals transferred via drone semen are demonstrated to not initiate the synthesis of the tergal gland alkenes. The compounds probably do not function as sex pheromones. However, the circumstances and timing of the initiation of production of the tergal gland alkenes strongly suggests a communication role for the compounds within the hive.

  19. Tandem ring-closing metathesis/transfer hydrogenation: practical chemoselective hydrogenation of alkenes.

    PubMed

    Connolly, Timothy; Wang, Zhongyu; Walker, Michael A; McDonald, Ivar M; Peese, Kevin M

    2014-09-01

    An operationally simple chemoselective transfer hydrogenation of alkenes using ruthenium metathesis catalysts is presented. Of great practicality, the transfer hydrogenation reagents can be added directly to a metathesis reaction and effect hydrogenation of the product alkene in a single pot at ambient temperature without the need to seal the vessel to prevent hydrogen gas escape. The reduction is applicable to a range of alkenes and can be performed in the presence of aryl halides and benzyl groups, a notable weakness of Pd-catalyzed hydrogenations. Scope and mechanistic considerations are presented.

  20. Catalytic Selenium-Promoted Intermolecular Friedel-Crafts Alkylation with Simple Alkenes.

    PubMed

    Tang, E; Zhao, Yinjiao; Li, Wen; Wang, Weilin; Zhang, Meng; Dai, Xin

    2016-03-01

    A method for conducting selenium-promoted intermolecular Friedel-Crafts (F-C) alkylation reactions has been developed with simple alkenes using trimethylsilyl trifluoromethanesulfonate as a catalyst and N-phenylselenophthalimide as an efficient selenium source. Electron-rich arenes smoothly underwent F-C alkylation with a variety of alkenes to afford alkylated products in good yield and with high regioselectivity and diastereoselectivity. The regioselectivity and stereoselectivity of arenes and alkenes as well as a preliminary mechanism of the F-C alkylation reaction are discussed. PMID:26882088

  1. ORGANIC CHEMISTRY. Iron-catalyzed intermolecular [2+2] cycloadditions of unactivated alkenes.

    PubMed

    Hoyt, Jordan M; Schmidt, Valerie A; Tondreau, Aaron M; Chirik, Paul J

    2015-08-28

    Cycloadditions, such as the [4+2] Diels-Alder reaction to form six-membered rings, are among the most powerful and widely used methods in synthetic chemistry. The analogous [2+2] alkene cycloaddition to synthesize cyclobutanes is kinetically accessible by photochemical methods, but the substrate scope and functional group tolerance are limited. Here, we report iron-catalyzed intermolecular [2+2] cycloaddition of unactivated alkenes and cross cycloaddition of alkenes and dienes as regio- and stereoselective routes to cyclobutanes. Through rational ligand design, development of this base metal-catalyzed method expands the chemical space accessible from abundant hydrocarbon feedstocks.

  2. Photoredox-Catalyzed Stereoselective Conversion of Alkynes into Tetrasubstituted Trifluoromethylated Alkenes.

    PubMed

    Tomita, Ren; Koike, Takashi; Akita, Munetaka

    2015-10-26

    A regio- and stereoselective synthesis of trifluoromethylated alkenes bearing four different substituents has been developed. Stereocontrolled sulfonyloxytrifluoromethylation of unsymmetric internal alkynes with an electrophilic CF3 reagent, namely the triflate salt of the Yagupol'skii-Umemoto reagent, in the presence of an Ir photoredox catalyst under visible-light irradiation afforded trifluoromethylalkenyl triflates with well-predictable stereochemistry resulting from anti addition of the trifluoromethyl and triflate groups. Subsequent palladium-catalyzed cross-couplings led to tetrasubstituted trifluoromethylated alkenes in a highly stereoselective manner. The present method is the first example of a facile one-pot synthesis of tetrasubstituted trifluoromethylated alkenes from simple alkynes.

  3. Critical influence of adsorption geometry in the heterogeneous epoxidation of "allylic" alkenes: structure and reactivity of three phenylpropene isomers on Cu(111).

    PubMed

    Williams, Federico J; Cropley, Rachael L; Vaughan, Owain P H; Urquhart, Andrew J; Tikhov, Mintcho S; Kolczewski, Christine; Hermann, Klaus; Lambert, Richard M

    2005-12-01

    It has long been conjectured that the difficulty of heterogeneously epoxidizing higher alkenes such as propene is due to the presence in the molecule of "allylic" H atoms that are readily stripped off by the oxygenated surface of the metal catalyst resulting in combustion. Here, taking advantage of the intrinsically higher epoxidation selectivity of Cu over Ag under vacuum conditions, we have used three phenylpropene structural isomers to examine the correlation between adsorption geometry and oxidation chemistry. It is found that under comparable conditions alpha-methylstyrene, trans-methylstyrene, and allylbenzene behave very differently on the oxygenated Cu(111) surface: the first undergoes extensive epoxidation accompanied by relatively little decomposition of the alkene; the second leads to some epoxide formation and extensive alkene decomposition; and the third is almost inert with respect to both reaction pathways. This reactive behavior is understandable in terms of the corresponding molecular conformations determined by near-edge X-ray absorption fine structure spectroscopy and density functional theory calculations. The proximity to the surface of the C=C function and of the allylic H atoms is critically important in determining reaction selectivity. This demonstrates the importance of adsorption geometry and confirms that allylic H stripping is indeed a key process that limits epoxidation selectivity in such cases.

  4. A robust methodology for kinetic model parameter estimation for biocatalytic reactions.

    PubMed

    Al-Haque, Naweed; Santacoloma, Paloma A; Neto, Watson; Tufvesson, Pär; Gani, Rafiqul; Woodley, John M

    2012-01-01

    Effective estimation of parameters in biocatalytic reaction kinetic expressions are very important when building process models to enable evaluation of process technology options and alternative biocatalysts. The kinetic models used to describe enzyme-catalyzed reactions generally include several parameters, which are strongly correlated with each other. State-of-the-art methodologies such as nonlinear regression (using progress curves) or graphical analysis (using initial rate data, for example, the Lineweaver-Burke plot, Hanes plot or Dixon plot) often incorporate errors in the estimates and rarely lead to globally optimized parameter values. In this article, a robust methodology to estimate parameters for biocatalytic reaction kinetic expressions is proposed. The methodology determines the parameters in a systematic manner by exploiting the best features of several of the current approaches. The parameter estimation problem is decomposed into five hierarchical steps, where the solution of each of the steps becomes the input for the subsequent step to achieve the final model with the corresponding regressed parameters. The model is further used for validating its performance and determining the correlation of the parameters. The final model with the fitted parameters is able to describe both initial rate and dynamic experiments. Application of the methodology is illustrated with a case study using the ω-transaminase catalyzed synthesis of 1-phenylethylamine from acetophenone and 2-propylamine.

  5. Recent advances on halohydrin dehalogenases-from enzyme identification to novel biocatalytic applications.

    PubMed

    Schallmey, Anett; Schallmey, Marcus

    2016-09-01

    Halohydrin dehalogenases are industrially relevant enzymes that catalyze the reversible dehalogenation of vicinal haloalcohols with formation of the corresponding epoxides. In the reverse reaction, also other negatively charged nucleophiles such as azide, cyanide, or nitrite are accepted besides halides to open the epoxide ring. Thus, novel C-N, C-C, or C-O bonds can be formed by halohydrin dehalogenases, which makes them attractive biocatalysts for the production of various β-substituted alcohols. Despite the fact that only five individual halohydrin dehalogenase enzyme sequences have been known until recently enabling their heterologous production, a large number of different biocatalytic applications have been reported using these enzymes. The recent characterization of specific sequence motifs has facilitated the identification of novel halohydrin dehalogenase sequences available in public databases and has largely increased the number of recombinantly available enzymes. These will help to extend the biocatalytic repertoire of this enzyme family and to foster novel biotechnological applications and developments in the future. This review gives a general overview on the halohydrin dehalogenase enzyme family and their biochemical properties and further focuses on recent developments in halohydrin dehalogenase biocatalysis and protein engineering. PMID:27502414

  6. Biocatalytic carbon capture via reversible reaction cycle catalyzed by isocitrate dehydrogenase.

    PubMed

    Xia, Shunxiang; Frigo-Vaz, Benjamin; Zhao, Xueyan; Kim, Jungbae; Wang, Ping

    2014-09-12

    The practice of carbon capture and storage (CCS) requires efficient capture and separation of carbon dioxide from its gaseous mixtures such as flue gas, followed by releasing it as a pure gas which can be subsequently compressed and injected into underground storage sites. This has been mostly achieved via reversible thermochemical reactions which are generally energy-intensive. The current work examines a biocatalytic approach for carbon capture using an NADP(H)-dependent isocitrate dehydrogenase (ICDH) which catalyzes reversibly carboxylation and decarboxylation reactions. Different from chemical carbon capture processes that rely on thermal energy to realize purification of carbon dioxide, the biocatalytic strategy utilizes pH to leverage the reaction equilibrium, thereby realizing energy-efficient carbon capture under ambient conditions. Results showed that over 25 mol of carbon dioxide could be captured and purified from its gas mixture for each gram of ICDH applied for each carboxylation/decarboxylation reaction cycle by varying pH between 6 and 9. This work demonstrates the promising potentials of pH-sensitive biocatalysis as a green-chemistry route for carbon capture.

  7. Nickel-catalysed cyclopropanation of electron-deficient alkenes with diiodomethane and diethylzinc.

    PubMed

    Xu, Jin; Samsuri, Nazurah Binte; Duong, Hung A

    2016-02-25

    In the presence of a nickel catalyst, the cyclopropanation of electron-deficient alkenes with diiodomethane and diethylzinc is drastically accelerated. A wide range of cyclopropyl ketones, esters and amides can be accessed under these conditions. PMID:26879514

  8. Is H Atom Abstraction Important in the Reaction of Cl with 1-Alkenes?

    PubMed

    Walavalkar, M P; Vijayakumar, S; Sharma, A; Rajakumar, B; Dhanya, S

    2016-06-23

    The relative yields of products of the reaction of Cl atoms with 1-alkenes (C4-C9) were determined to see whether H atom abstraction is an important channel and if it is to identify the preferred position of abstraction. The presence of all the possible positional isomers of long chain alkenones and alkenols among the products, along with chloroketones and chloroalcohols, confirms the occurrence of H atom abstraction. A consistent pattern of distribution of abstraction products is observed with oxidation at C4 (next to allyl) being the lowest and that at CH2 groups away from the double bond being the highest. This contradicts with the higher stability of allyl (C3) radical. For a better understanding of the relative reactivity, ab initio calculations at MP2/6-311+G (d,p) level of theory are carried out in the case of 1-heptene. The total rate coefficient, calculated using conventional transition state theory, was found to be in good agreement with the experimental value at room temperature. The preferred position of Cl atom addition is predicted to be the terminal carbon atom, which matches with the experimental observation, whereas the rate coefficients calculated for individual channels of H atom abstraction do not explain the observed pattern of products. The distribution of abstraction products except at C4 is found to be better explained by reported structure activity relationship, developed from experimental rate coefficient data. This implies the reactions to be kinetically dictated and emphasizes the importance of secondary reactions.

  9. Unprecedented Selective Oxidation of Styrene Derivatives using a Supported Iron Oxide Nanocatalyst in Aqueous Medium

    EPA Science Inventory

    Iron oxide nanoparticles supported on mesoporous silica-type materials have been successfully utilized in the aqueous selective oxidation of alkenes under mild conditions using hydrogen peroxide as a green oxidant. Catalysts could be easily recovered after completion of the reac...

  10. Copper-catalyzed decarboxylative coupling of alkynyl carboxylates with 1,1-dibromo-1-alkenes.

    PubMed

    Huang, Zheng; Shang, Rui; Zhang, Zi-Rong; Tan, Xiao-Dan; Xiao, Xiao; Fu, Yao

    2013-05-01

    A copper-catalyzed decarboxylative coupling reaction of potassium alkynyl carboxylates with 1,1-dibromo-1-alkenes was developed for the synthesis of unsymmetrical 1,3-diyne and 1,3,5-triyne derivatives. Diverse aryl, alkenyl, alkynyl, and alkyl substituted 1,1-dibromo-1-alkenes can react smoothly with aryl and alkyl substituted propiolates to produce unsymmetrical 1,3-diynes and 1,3,5-triynes with high selectivity and good functional group compatibility.

  11. Diverse Asymmetric Hydrofunctionalization of Aliphatic Internal Alkenes through Catalytic Regioselective Hydroboration.

    PubMed

    Xi, Yumeng; Hartwig, John F

    2016-06-01

    We report a two-step strategy for diverse hydrofunctionalizations of aliphatic internal alkenes with high regioselectivity and enantioselectivity. This process comprises a copper-catalyzed asymmetric hydroboration and subsequent stereospecific derivatizations of the secondary boronates. By this strategy, a range of compounds, such as amides, alkyl fluorides and bromides, alcohols, aldehydes, arenes, and heteroarenes, were synthesized from an internal alkene with high regioselectivity and enantioselectivity. Computational studies provide insight into the origins of these selectivities. PMID:27167490

  12. Fundamental Flame Velocities of Pure Hydrocarbons I : Alkanes, Alkenes, Alkynes Benzene, and Cyclohexane

    NASA Technical Reports Server (NTRS)

    Gerstein, Melvin; Levine, Oscar; Wong, Edgar L

    1950-01-01

    The flame velocities of 37 pure hydrocarbons including normal and branched alkanes, alkenes, and alkynes; as well as benzene and cyclohexane, together with the experimental technique employed are presented. The normal alkanes have about the same flame velocity from ethane through heptane with methane being about 16 percent lower. Unsaturation increases the flame velocity in the order of alkanes, alkenes, and alkynes. Branching reduces the flame velocity.

  13. Environmental significance of biocatalytic conversion of low grade oils

    SciTech Connect

    Lin, M.S.; Premuzic, E.T.; Lian, H.; Zhou, W.M.; Yablon, J.

    1996-09-01

    Studies dealing with the interactions between extremophilic microorganisms and crude oils have led to the identification of biocatalysts which through multiple biochemical reactions catalyze desulfurization, denitrogenation, and demetalation reactions in oils. Concurrently, the oils are also converted to lighter oils. These complex biochemical reactions have served as models in the development of the crude oil bioconversion technology to be applied prior to the treatment of oils by conventional chemical processes. In practical terms, this means that the efficiency of the existing technology is being enhanced. For example, the recently introduced additional regulation for the emission of nitrogen oxides in some states restricts further the kinds of oils that may be used in burners. The biocatalysts being developed in this laboratory selectively interact with nitrogen compounds, i.e. basic and neutral types present in the oil and, hence, affect the fuel NOx production. This, in turn, has a cost-efficient influence on the processed oils and their consumption. In this paper, these cost-efficient and beneficial effects will be discussed in terms of produced oils, the lowering of sulfur and nitrogen contents, and the effect on products, as well as the longevity of catalysts due to the removal of heteroatoms and metal containing compounds found in crudes.

  14. Biocatalytic CO2 sequestration based on shell regeneration

    NASA Astrophysics Data System (ADS)

    Lee, S.

    2012-04-01

    Carbon dioxide, CO2, is one of the green gases, being uniformly distributed over the earth's surface. Recently, a variety of methods exists or has been proposed for pre- or post-emission capture and sequestration of CO2. However, CCS (carbon capture & storage) do not quarntee permanent treatment of CO2 and could ingenerate environment risks. Some organisms convert CO2 into exoskeleton (e.g., mollusks) or energy sources (e.g., plants) during metabolism under atmospheric conditions. One of representative biomaterials in ocean is bivalve shell to be composed of CaCO3. Calcium carbonate is not only abundant material in the world but also thermodynamically stable mineral in the capture of CO2. Bivalve has produced CaCO3 under seawater condition, in other word, near atmospheric conditions (1 atm. and around 20-25 oC). At the inorganic point, the synthesis of CaCO3 is as followed. Ca2+ + CO32- -> CaCO3 The bivalve shell plays an important role to protect bivalve's internal organs from prodetor. What will be happened if the shell is damaged and a hole is made? Bivalve must cover the hole to prevent the oxidation of internal organs as fast as possible. From in vitro crystallization test of a notched shell, rapid CaCO3 production was identified at the damaged area. The biocatalyst related to shell regeneration was purified and named as SPSR (Soluble Protein related to Shell Regeneration) that is obtained from the oyster, Crassostrea gigas. And in vitro CaCO3 crystallization test was used to calculate the crystal growth rate of SPSR on CaCO3 crystallization. The characteristics of SPRR are discussed at the point of CO2 hydration and rapid CaCO3 synthesis. To develop the bioinspired process based on shell regeneration concept, the analysis of protein structure has been studied and the immobilization has been carried out for easy recovery of SPSR.

  15. Regioselective Oxo-Amination of Alkenes and Enol Ethers with N-Bromosuccinimide-Dimethyl Sulfoxide Combination: A Facile Synthesis of α-Amino-Ketones and Esters.

    PubMed

    Prasad, Pragati K; Reddi, Rambabu N; Sudalai, Arumugam

    2016-02-01

    An unprecedented conversion of alkenes and enol ethers to the corresponding α-imido carbonyl compounds with excellent regioselectivity and yields has been developed. This oxo-amination process employs readily available N-bromosuccinimide (NBS) and secondary amines as N-sources and dimethyl sulfoxide (DMSO) as the oxidant and also leads to the production of amino alcohols in a single step on reduction, thus broadening the scope of this operationally simple reaction. For the first time, the formation of reactive Me2S(+)-O-Br species generated by the interaction of NBS with DMSO has been proven.

  16. Synthesis of Z-alkenes from Rh(I)-catalyzed olefin isomerization of β,γ-unsaturated ketones.

    PubMed

    Zhuo, Lian-Gang; Yao, Zhong-Ke; Yu, Zhi-Xiang

    2013-09-20

    Developing olefin isomerization reactions to reach kinetically controlled Z-alkenes is challenging because formation of trans-alkenes is thermodynamically favored under the traditional catalytic conditions using acids, bases, or transition metals as the catalysts. A new synthesis of Z-alkenes from Rh(I)-catalyzed olefin isomerization of β,γ-unsaturated ketones to α,β-unsaturated ketones was developed, providing an easy and efficient way to access various Z-enones.

  17. Silver(I)-Mediated Phosphorylation/Cyclization Cascade of N-Cyanamide Alkenes for Divergent Access to Quinazolinones and Dihydroisoquinolinones.

    PubMed

    Zheng, Jing; Zhang, Yan; Wang, Dahai; Cui, Sunliang

    2016-04-15

    A silver(I)-mediated phosphorylation/cyclization radical cascade of N-cyanamide alkenes has been developed. The addition of in situ generated phosphorus radical to N-cyanamide alkenes triggers the cascade, resulting in late-stage cyclization toward divergent access to 4-quinazolinones and dihydroisoquinolinones. Both terminal and internal N-cyanamide alkenes are applicable in this protocol, and the cyclizations are consistent with Baldwin's rule.

  18. Recent applications in natural product synthesis of dihydrofuran and -pyran formation by ring-closing alkene metathesis.

    PubMed

    Jacques, Reece; Pal, Ritashree; Parker, Nicholas A; Sear, Claire E; Smith, Peter W; Ribaucourt, Aubert; Hodgson, David M

    2016-07-01

    In the past two decades, alkene metathesis has risen in prominence to become a significant synthetic strategy for alkene formation. Many total syntheses of natural products have used this transformation. We review the use, from 2003 to 2015, of ring-closing alkene metathesis (RCM) for the generation of dihydrofurans or -pyrans in natural product synthesis. The strategies used to assemble the RCM precursors and the subsequent use of the newly formed unsaturation will also be highlighted and placed in context. PMID:27108941

  19. Immobilized biocatalytic process development and potential application in membrane separation: a review.

    PubMed

    Chakraborty, Sudip; Rusli, Handajaya; Nath, Arijit; Sikder, Jaya; Bhattacharjee, Chiranjib; Curcio, Stefano; Drioli, Enrico

    2016-01-01

    Biocatalytic membrane reactors have been widely used in different industries including food, fine chemicals, biological, biomedical, pharmaceuticals, environmental treatment and so on. This article gives an overview of the different immobilized enzymatic processes and their advantages over the conventional chemical catalysts. The application of a membrane bioreactor (MBR) reduces the energy consumption, and system size, in line with process intensification. The performances of MBR are considerably influenced by substrate concentration, immobilized matrix material, types of immobilization and the type of reactor. Advantages of a membrane associated bioreactor over a free-enzyme biochemical reaction, and a packed bed reactor are, large surface area of immobilization matrix, reuse of enzymes, better product recovery along with heterogeneous reactions, and continuous operation of the reactor. The present research work highlights immobilization techniques, reactor setup, enzyme stability under immobilized conditions, the hydrodynamics of MBR, and its application, particularly, in the field of sugar, starch, drinks, milk, pharmaceutical industries and energy generation.

  20. Biocatalytic methanation of hydrogen and carbon dioxide in a fixed bed bioreactor.

    PubMed

    Alitalo, Anni; Niskanen, Marko; Aura, Erkki

    2015-11-01

    Biocatalytic methanation of H2 and CO2 was studied in a fixed bed reactor system consisting of two solid state bioreactors in series connected to a recirculation system. Bioreactors were packed with a mixture of vermiculite shales and granular perlite material as a support material. A maximal methane productivity of 6.35l/lreactord was achieved at a hydrogen feed rate of 25.2l/lreactord, while hydrogen conversion rate was 100%. However, stable operation of the reactor at this efficiency remains to be achieved. Very simple reactor design, constructed from low cost materials, and the idea of exploiting waste material as a robust source of nutrients for methanogens makes this study very interesting regarding the overall usability and suitability of the system as part of a decentralized energy system. PMID:26298404

  1. Biocatalytic synthesis of acrylates in supercritical fluids: tuning enzyme activity by changing pressure.

    PubMed Central

    Kamat, S V; Iwaskewycz, B; Beckman, E J; Russell, A J

    1993-01-01

    Supercritical fluids are a unique class of nonaqueous media in which biocatalytic reactions can occur. The physical properties of supercritical fluids, which include gas-like diffusivities and liquid-like densities, can be predictably controlled with changing pressure. This paper describes how adjustment of pressure, with the subsequent predictable changes of the dielectric constant and Hildebrand solubility parameter for fluoroform, ethane, sulfur hexafluoride, and propane, can be used to manipulate the activity of lipase in the transesterification of methylmethacrylate with 2-ethyl-1-hexanol. Of particular interest is that the dielectric constant of supercritical fluoroform can be tuned from approximately 1 to 8, merely by increasing pressure from 850 to 4000 psi (from 5.9 to 28 MPa). The possibility now exists to predictably alter both the selectivity and the activity of a biocatalyst merely by changing pressure. Images Fig. 6 PMID:8464910

  2. Biocatalytic self-assembly of nanostructured peptide microparticles using droplet microfluidics.

    PubMed

    Bai, Shuo; Debnath, Sisir; Gibson, Kirsty; Schlicht, Barbara; Bayne, Lauren; Zagnoni, Michele; Ulijn, Rein V

    2014-01-29

    Uniformly-sized, nanostructured peptide microparticles are generated by exploiting the ability of enzymes to serve (i) as catalysts, to control self-assembly within monodisperse, surfactant-stabilized water-in-oil microdroplets, and (ii) as destabilizers of emulsion interfaces, to enable facile transfer of the produced microparticles to water. This approach combines the advantages of biocatalytic self-assembly with the compartmentalization properties enabled by droplet microfluidics. Firstly, using microfluidic techniques, precursors of self-assembling peptide derivatives and enzymes are mixed in the microdroplets which upon catalytic conversion undergo molecular self-assembly into peptide particles, depending on the chemical nature of the precursors. Due to their amphiphilic nature, enzymes adsorb at the water-surfactant-oil interface of the droplets, inducing the transfer of peptide microparticles from the oil to the aqueous phase. Ultimately, through washing steps, enzymes can be removed from the microparticles which results in uniformely-sized particles composed of nanostructured aromatic peptide amphiphiles.

  3. Spectroscopic and Theoretical Identification of Two Thermal Isomerization Pathways for Bistable Chiral Overcrowded Alkenes.

    PubMed

    Kistemaker, Jos C M; Pizzolato, Stefano F; van Leeuwen, Thomas; Pijper, Thomas C; Feringa, Ben L

    2016-09-12

    Chiroptical molecular switches play an important role in responsive materials and dynamic molecular systems. Here we present the synthesis of four chiral overcrowded alkenes and the experimental and computational study of their photochemical and thermal behavior. By irradiation with UV light, metastable diastereoisomers with opposite helicity were generated through high yielding E-Z isomerizations. Kinetic studies on metastable 1-4 using CD spectroscopy and HPLC analysis revealed two pathways at higher temperatures for the thermal isomerization, namely a thermal E-Z isomerization (TEZI) and a thermal helix inversion (THI). These processes were also studied computationally whereby a new strategy was developed for calculating the TEZI barrier for second-generation overcrowded alkenes. To demonstrate that these overcrowded alkenes can be employed as bistable switches, photochromic cycling was performed, which showed that the alkenes display good selectivity and fatigue resistance over multiple irradiation cycles. In particular, switch 3 displayed the best performance in forward and backward photoswitching, while 1 excelled in thermal stability of the photogenerated metastable form. Overall, the alkenes studied showed a remarkable and unprecedented combination of switching properties including dynamic helicity, reversibility, selectivity, fatigue resistance, and thermal stability. PMID:27471009

  4. Spectroscopic and Theoretical Identification of Two Thermal Isomerization Pathways for Bistable Chiral Overcrowded Alkenes.

    PubMed

    Kistemaker, Jos C M; Pizzolato, Stefano F; van Leeuwen, Thomas; Pijper, Thomas C; Feringa, Ben L

    2016-09-12

    Chiroptical molecular switches play an important role in responsive materials and dynamic molecular systems. Here we present the synthesis of four chiral overcrowded alkenes and the experimental and computational study of their photochemical and thermal behavior. By irradiation with UV light, metastable diastereoisomers with opposite helicity were generated through high yielding E-Z isomerizations. Kinetic studies on metastable 1-4 using CD spectroscopy and HPLC analysis revealed two pathways at higher temperatures for the thermal isomerization, namely a thermal E-Z isomerization (TEZI) and a thermal helix inversion (THI). These processes were also studied computationally whereby a new strategy was developed for calculating the TEZI barrier for second-generation overcrowded alkenes. To demonstrate that these overcrowded alkenes can be employed as bistable switches, photochromic cycling was performed, which showed that the alkenes display good selectivity and fatigue resistance over multiple irradiation cycles. In particular, switch 3 displayed the best performance in forward and backward photoswitching, while 1 excelled in thermal stability of the photogenerated metastable form. Overall, the alkenes studied showed a remarkable and unprecedented combination of switching properties including dynamic helicity, reversibility, selectivity, fatigue resistance, and thermal stability.

  5. Selective thermal oxidation of hydrocarbons in zeolites by oxygen

    DOEpatents

    Frei, Heinz; Blatter, Fritz; Sun, Hai

    2000-01-01

    A process for selective thermal oxidation of hydrocarbons adsorbed onto zeolite matrices. A highly selective thermal oxidation of unsubstituted or alkyl substituted alkanes, alkenes, aromatics and cycloalkyls is carried out in solvent free zeolites under dark thermal conditions. The process oxidizes hydrocarbons almost completely selectively without substantial production of byproducts.

  6. Inhibitory Potency of 4-Carbon Alkanes and Alkenes toward CYP2E1 Activity

    PubMed Central

    Hartman, Jessica H.; Miller, Grover P.; Boysen, Gunnar

    2016-01-01

    CYP2E1 has been implicated in the bioactivation of many small molecules into reactive metabolites which form adducts with proteins and DNA, and thus a better understanding of the molecular determinants of its selectivity are critical for accurate toxicological predictions. In this study, we determined the potency of inhibition of human CYP2E1 for various 4-carbon alkanes, alkenes and alcohols. In addition, known CYP2E1 substrates and inhibitors including 4-methylpyrazole, aniline, and dimethylnitrosamine were included to determine their relative potencies. Of the 1,3-butadiene-derived metabolites studied, 3,4-epoxy-1-butene was the strongest inhibitor with an IC50 of 110 μM compared to 1700 μM and 6600 μM for 1,2-butenediol and 1,2:3,4-diepoxybutane, respectively. Compared to known inhibitors, inhibitory potency of 3,4-epoxy-1-butene is between 4-methylpyrazole (IC50 = 1.8 μM) and dimethylnitrosamine (IC50 = 230 μM). All three butadiene metabolites inhibit CYP2E1 activity through a simple competitive mechanism. Among the 4-carbon compounds studied, the presence and location of polar groups seems to influence inhibitory potency. To further examine this notion, the investigation was extended to include structurally and chemically similar analogs, including propylene oxide and various butane alcohols. Those results demonstrated preferential recognition of CYP2E1 toward the type and location of polar and hydrophobic structural elements. Taken together, CYP2E1 metabolism may be modified in vivo by exposure to 4-carbon compounds, such as drugs, and nutritional constituents, a finding that highlights the complexity of exposure to mixtures. PMID:24561005

  7. Preparation of Biocatalytic Microparticles by Interfacial Self-Assembly of Enzyme-Nanoparticle Conjugates Around a Cross-Linkable Core.

    PubMed

    Andler, S M; Wang, L-S; Goddard, J M; Rotello, V M

    2016-01-01

    Rational design of hierarchical interfacial assembly of reusable biocatalytic microparticles is described in this chapter. Specifically, purified enzymes and functionalized nanoparticles are electrostatically assembled at the interface of cross-linked microparticles which are formed through ring opening metathesis polymerization. The diameters of microparticle assemblies average 10μm, and they show enhanced kinetic efficiency as well as improved stability against heat, pH, and solvent denaturation when compared to stabilities of the corresponding native enzymes.

  8. Metal-Free C–H Alkyliminylation and Acylation of Alkenes with Secondary Amides

    PubMed Central

    Huang, Pei-Qiang; Huang, Ying-Hong; Geng, Hui; Ye, Jian-Liang

    2016-01-01

    Carbon–carbon bond formation by metal-free cross-coupling of two reactants with low reactivity represents a challenge in organic synthesis. Secondary amides and alkenes are two classes of bench-stable compounds. The low electrophilicity of the former and low nucleophilicity of the latter make the direct coupling of these two partners challenging yet highly desirable. We report herein an unprecedented intermolecular reaction of secondary amides with alkenes to afford α,β-unsaturated ketimines or enones, which are versatile intermediates for organic synthesis and are prevalent in bioactive compounds and functional materials. Our strategy relies on the chemoselective activation of the secondary amide with trifluoromethanesulfonic anhydride (Tf2O)/2-fluoropyridine to generate a highly reactive nitrilium intermediate, which reacts efficiently with alkenes. This metal-free synthesis is characterized by its mild reaction conditions, excellent functional group tolerance and chemoselectivity, allowing the preparation of multi-functionalized compounds without using protecting groups. PMID:27356173

  9. Metal-Free C-H Alkyliminylation and Acylation of Alkenes with Secondary Amides.

    PubMed

    Huang, Pei-Qiang; Huang, Ying-Hong; Geng, Hui; Ye, Jian-Liang

    2016-01-01

    Carbon-carbon bond formation by metal-free cross-coupling of two reactants with low reactivity represents a challenge in organic synthesis. Secondary amides and alkenes are two classes of bench-stable compounds. The low electrophilicity of the former and low nucleophilicity of the latter make the direct coupling of these two partners challenging yet highly desirable. We report herein an unprecedented intermolecular reaction of secondary amides with alkenes to afford α,β-unsaturated ketimines or enones, which are versatile intermediates for organic synthesis and are prevalent in bioactive compounds and functional materials. Our strategy relies on the chemoselective activation of the secondary amide with trifluoromethanesulfonic anhydride (Tf2O)/2-fluoropyridine to generate a highly reactive nitrilium intermediate, which reacts efficiently with alkenes. This metal-free synthesis is characterized by its mild reaction conditions, excellent functional group tolerance and chemoselectivity, allowing the preparation of multi-functionalized compounds without using protecting groups. PMID:27356173

  10. Titanocene(III)-Catalyzed Three-Component Reaction of Secondary Amides, Aldehydes, and Electrophilic Alkenes.

    PubMed

    Zheng, Xiao; He, Jiang; Li, Heng-Hui; Wang, Ao; Dai, Xi-Jie; Wang, Ai-E; Huang, Pei-Qiang

    2015-11-01

    An umpolung Mannich-type reaction of secondary amides, aliphatic aldehydes, and electrophilic alkenes has been disclosed. This reaction features the one-pot formation of C-N and C-C bonds by a titanocene-catalyzed radical coupling of the condensation products, from secondary amides and aldehydes, with electrophilic alkenes. N-substituted γ-amido-acid derivatives and γ-amido ketones can be efficiently prepared by the current method. Extension to the reaction between ketoamides and electrophilic alkenes allows rapid assembly of piperidine skeletons with α-amino quaternary carbon centers. Its synthetic utility has been demonstrated by a facile construction of the tricyclic core of marine alkaloids such as cylindricine C and polycitorol A.

  11. Use of a Ceramic Membrane to Improve the Performance of Two-Separate-Phase Biocatalytic Membrane Reactor.

    PubMed

    Ranieri, Giuseppe; Mazzei, Rosalinda; Wu, Zhentao; Li, Kang; Giorno, Lidietta

    2016-03-14

    Biocatalytic membrane reactors (BMR) combining reaction and separation within the same unit have many advantages over conventional reactor designs. Ceramic membranes are an attractive alternative to polymeric membranes in membrane biotechnology due to their high chemical, thermal and mechanical resistance. Another important use is their potential application in a biphasic membrane system, where support solvent resistance is highly needed. In this work, the preparation of asymmetric ceramic hollow fibre membranes and their use in a two-separate-phase biocatalytic membrane reactor will be described. The asymmetric ceramic hollow fibre membranes were prepared using a combined phase inversion and sintering technique. The prepared fibres were then used as support for lipase covalent immobilization in order to develop a two-separate-phase biocatalytic membrane reactor. A functionalization method was proposed in order to increase the density of the reactive hydroxyl groups on the surface of ceramic membranes, which were then amino-activated and treated with a crosslinker. The performance and the stability of the immobilized lipase were investigated as a function of the amount of the immobilized biocatalytst. Results showed that it is possible to immobilize lipase on a ceramic membrane without altering its catalytic performance (initial residual specific activity 93%), which remains constant after 6 reaction cycles.

  12. Use of a Ceramic Membrane to Improve the Performance of Two-Separate-Phase Biocatalytic Membrane Reactor.

    PubMed

    Ranieri, Giuseppe; Mazzei, Rosalinda; Wu, Zhentao; Li, Kang; Giorno, Lidietta

    2016-01-01

    Biocatalytic membrane reactors (BMR) combining reaction and separation within the same unit have many advantages over conventional reactor designs. Ceramic membranes are an attractive alternative to polymeric membranes in membrane biotechnology due to their high chemical, thermal and mechanical resistance. Another important use is their potential application in a biphasic membrane system, where support solvent resistance is highly needed. In this work, the preparation of asymmetric ceramic hollow fibre membranes and their use in a two-separate-phase biocatalytic membrane reactor will be described. The asymmetric ceramic hollow fibre membranes were prepared using a combined phase inversion and sintering technique. The prepared fibres were then used as support for lipase covalent immobilization in order to develop a two-separate-phase biocatalytic membrane reactor. A functionalization method was proposed in order to increase the density of the reactive hydroxyl groups on the surface of ceramic membranes, which were then amino-activated and treated with a crosslinker. The performance and the stability of the immobilized lipase were investigated as a function of the amount of the immobilized biocatalytst. Results showed that it is possible to immobilize lipase on a ceramic membrane without altering its catalytic performance (initial residual specific activity 93%), which remains constant after 6 reaction cycles. PMID:26985887

  13. Carbohydrate base co-polymers as an efficient immobilization matrix to enhance lipase activity for potential biocatalytic applications.

    PubMed

    Badgujar, Kirtikumar Chandulal; Bhanage, Bhalchandra Mahadeo

    2015-12-10

    In the present study, we have synthesized biocompatible hybrid blend of cellulosic polymers of hydroxypropyl-methyl-cellulose (HPMC) and chitosan (CHY) for the immobilization of Candida rugosa lipase (CRL). The immobilized biocatalyst HPMC:CHY:CRL was subjected for characterization such as SEM, TGA, water content analysis, lipase activity, specific activity and protein content analysis. The kinetic parameter study (Rmax/Km) demonstrated improved biocatalytic activity of lipase after immobilization on carbohydrate co-polymers of HPMC:CHY. This biocatalyst was then employed to study practical biocatalytic applications for kinetic resolution which provided 50% conversion and >94% enantiomeric excess of substrate/product (ees/eep). The protocol demonstrated excellent recyclability upto five cycles. Finally, we studied influence of immobilization on cellulosic polymers for substrate, structure and reactivity for kinetic resolution. Hence, we investigated R0 (initial reaction rate), E-value (enantioselectivity) and Ea (activation energy). This study confirms that, lipase immobilized on carbohydrate polymers had 3-4 folds higher biocatalytic activity as compared to crude CRL. PMID:26428176

  14. Peroxide promoted tunable decarboxylative alkylation of cinnamic acids to form alkenes or ketones under metal-free conditions.

    PubMed

    Ji, Jing; Liu, Ping; Sun, Peipei

    2015-05-01

    A tunable decarboxylative alkylation of cinnamic acids with alkanes was developed to form alkenes or ketones under transition metal-free conditions. In the presence of DTBP or DTBP/TBHP, the reaction gave alkenes and ketones respectively via a radical mechanism in moderate to good yields.

  15. Photochemical Synthesis and Ligand Exchange Reactions of Ru(CO)[subscript 4] (Eta[superscript 2]-Alkene) Compounds

    ERIC Educational Resources Information Center

    Cooke, Jason; Berry, David E.; Fawkes, Kelli L.

    2007-01-01

    The photochemical synthesis and subsequent ligand exchange reactions of Ru(CO)[subscript 4] (eta[superscript2]-alkene) compounds has provided a novel experiment for upper-level inorganic chemistry laboratory courses. The experiment is designed to provide a system in which the changing electronic properties of the alkene ligands could be easily…

  16. In tandem or alone: a remarkably selective transfer hydrogenation of alkenes catalyzed by ruthenium olefin metathesis catalysts.

    PubMed

    Zieliński, Grzegorz Krzysztof; Samojłowicz, Cezary; Wdowik, Tomasz; Grela, Karol

    2015-03-01

    A system for transfer hydrogenation of alkenes, composed of a ruthenium metathesis catalyst and HCOOH, is presented. This operationally simple system can be formed directly after a metathesis reaction to effect hydrogenation of the metathesis product in a single-pot. These hydrogenation conditions are applicable to a wide range of alkenes and offer remarkable selectivity. PMID:25586518

  17. In tandem or alone: a remarkably selective transfer hydrogenation of alkenes catalyzed by ruthenium olefin metathesis catalysts.

    PubMed

    Zieliński, Grzegorz Krzysztof; Samojłowicz, Cezary; Wdowik, Tomasz; Grela, Karol

    2015-03-01

    A system for transfer hydrogenation of alkenes, composed of a ruthenium metathesis catalyst and HCOOH, is presented. This operationally simple system can be formed directly after a metathesis reaction to effect hydrogenation of the metathesis product in a single-pot. These hydrogenation conditions are applicable to a wide range of alkenes and offer remarkable selectivity.

  18. An insight into the Lewis acid-catalyzed intramolecular aminocyanation and oxycyanation of alkenes: a concerted or stepwise mechanism.

    PubMed

    Zhao, Jiyang; Wang, Guoqiang; Li, Shuhua

    2015-10-28

    Density functional theory investigations reveal that the intramolecular additions of N-CN bonds to alkenes proceed in a novel asynchronous and concerted mechanism, while the intramolecular addition of O-CN bonds to alkenes may occur by both concerted and stepwise pathways.

  19. A new approach to ferrocene derived alkenes via copper-catalyzed olefination

    PubMed Central

    Muzalevskiy, Vasily M; Shastin, Aleksei V; Demidovich, Alexandra D; Shikhaliev, Namiq G; Magerramov, Abel M; Khrustalev, Victor N; Rakhimov, Rustem D; Vatsadze, Sergey Z

    2015-01-01

    Summary A new approach to ferrocenyl haloalkenes and bis-alkenes was elaborated. The key procedure involves copper catalyzed olefination of N-unsubstituted hydrazones, obtained from ferrocene-containing carbonyl compounds and hydrazine, with polyhaloalkanes. The procedure is simple, cheap and could be applied for the utilization of environmentally harmful polyhalocarbons. The cyclic voltammetry study of the representative examples of the synthesized ferrocenyl alkenes shows the strong dependence of the cathodic behavior on the amount of vinyl groups: while for the monoalkene containing molecules no reduction is seen, the divinyl products are reduced in several steps. PMID:26664627

  20. Copper-catalyzed intermolecular trifluoromethylarylation of alkenes: mutual activation of arylboronic acid and CF3+ reagent.

    PubMed

    Wang, Fei; Wang, Dinghai; Mu, Xin; Chen, Pinhong; Liu, Guosheng

    2014-07-23

    A novel copper-catalyzed intermolecular trifluoromethylarylation of alkenes is developed using less active ether-type Togni's reagent under mild reaction conditions. Various alkenes and diverse arylboronic acids are compatible with these conditions. Preliminary mechanistic studies reveal that a mutual activation process between arylboronic acid and CF3(+) reagent is essential. In addition, the reaction might involve a rate-determining transmetalation, and the final aryl C-C bond is derived from reductive elimination of the aryl(alkyl)Cu(III) intermediate. PMID:24983408

  1. Trifluoromethylchlorosulfonylation of alkenes: evidence for an inner-sphere mechanism by a copper phenanthroline photoredox catalyst.

    PubMed

    Bagal, Dattatraya B; Kachkovskyi, Georgiy; Knorn, Matthias; Rawner, Thomas; Bhanage, Bhalchandra M; Reiser, Oliver

    2015-06-01

    A visible-light-mediated procedure for the unprecedented trifluoromethylchlorosulfonylation of unactivated alkenes is presented. It uses [Cu(dap)2]Cl as catalyst, and contrasts with [Ru(bpy)3]Cl2, [Ir(ppy)2(dtbbpy)]PF6, or eosin Y that exclusively give rise to trifluoromethylchlorination of the same alkenes. It is assumed that [Cu(dap)2]Cl plays a dual role, that is, acting both as an electron transfer reagent as well as coordinating the reactants in the bond forming processes. PMID:25926329

  2. Palladium-Catalyzed Alkene Carboamination Reactions of Electron-Poor Nitrogen Nucleophiles

    PubMed Central

    Peterson, Luke J.

    2015-01-01

    Modified reaction conditions that facilitate Pd-catalyzed alkene carboamination reactions of electron-deficient nitrogen nucleophiles are reported. Pent-4-enylamine derivatives bearing N-tosyl or N-trifluoroacetyl groups are coupled with aryl triflates to afford substituted pyrrolidines in good yield. These reactions proceed via a mechanism involving anti-aminopalladation of the alkene, which differs from previously reported analogous reactions of N-aryl and N-boc pentenylamines. The application of these conditions to a formal synthesis of (±)-aphanorphine is also described. PMID:26622222

  3. Perfluoroalkylation of Unactivated Alkenes with Acid Anhydrides as the Perfluoroalkyl Source.

    PubMed

    Kawamura, Shintaro; Sodeoka, Mikiko

    2016-07-18

    An efficient perfluoroalkylation of unactivated alkenes with perfluoro acid anhydrides was developed. Copper salts play a crucial role as a catalyst to achieve allylic perfluoroalkylation with the in situ generated bis(perfluoroacyl) peroxides. Furthermore, carboperfluoroalkylation of alkene bearing an aromatic ring at an appropriate position on the carbon side chain was found to proceed under metal-free conditions to afford carbocycles or heterocycles bearing a perfluoroalkyl group. This method, which makes use of readily available perfluoroalkyl sources, offers a convenient and powerful tool for introducing a perfluoroalkyl group onto an sp(3) carbon to construct synthetically useful skeletons. PMID:27254318

  4. The kinetics of the gas-phase reactions of selected monoterpenes and cyclo-alkenes with ozone and the NO3 radical

    NASA Astrophysics Data System (ADS)

    Stewart, D. J.; Almabrok, S. H.; Lockhart, J. P.; Mohamed, O. M.; Nutt, D. R.; Pfrang, C.; Marston, G.

    2013-05-01

    The relative rate method has been used to measure the room-temperature rate constants for the gas-phase reactions of ozone and NO3 with selected monoterpenes and cyclo-alkenes with structural similarities to monoterpenes. Measurements were carried out at 298 ± 2 K and 760 ± 10 Torr. The following rate constants (in units of 10-18 cm3 molecule-1 s-1) were obtained for the reaction with ozone: methyl cyclohexene (132 ± 17), terpinolene (1290 ± 360), ethylidene cyclohexane (223 ± 57), norbornene (860 ± 240), t-butyl isopropylidene cyclohexane (1500 ± 460), cyclopentene (543 ± 94), cyclohexene (81 ± 18), cyclooctene (451 ± 66), dicyclopentadiene (1460 ± 170) and α-pinene (107 ± 13). For the reaction with NO3 the rate constants obtained (in units of 10-12 cm3 molecule-1 s-1) were: methyl cyclohexene (7.92 ± 0.95), terpinolene (47.9 ± 4.0), ethylidene cyclohexane (4.30 ± 0.24), norbornene (0.266 ± 0.029), cyclohexene (0.540 ± 0.017), cyclooctene (0.513 ± 0.029), dicyclopentadiene (1.20 ± 0.10) and α-pinene (5.17 ± 0.62). Errors are quoted as the root mean square of the statistical error (95% confidence) and the quoted error in the rate constant for the reference compound. Combining these results with previous studies, new recommendations for the rate constants are presented. Molecular orbital energies were calculated for each alkene and the kinetic data are discussed in terms of the deviation from the structure-activity relationship obtained from the rate constants for a series of simple alkenes. Lifetimes with respect to key initiators of atmospheric oxidation have been calculated suggesting that the studied reactions play dominant roles in the night-time removal of these compounds from the atmosphere.

  5. Preference of Ruthenium-Based Metathesis Catalysts toward Z- and E-Alkenes as a Guide for Selective Reactions to Alkene Stereoisomers.

    PubMed

    Lee, Jihong; Kim, Kyung Hwan; Lee, Ok Suk; Choi, Tae-Lim; Lee, Hee-Seung; Ihee, Hyotcherl; Sohn, Jeong-Hun

    2016-09-01

    As a guide for selective reactions toward either Z- or E-alkene in a metathesis reaction, the relative preference of metathesis Ru catalysts for each stereoisomer was determined by a method using time-dependent fluorescence quenching. We found that Ru-1 prefers the Z-isomer over the E-isomer, whereas Ru-2 prefers the E-isomer over the Z-isomer. The Z/E-alkene preference of the catalysts precisely predicted the Z/E isomeric selectivity in the metathesis reactions of diene substrates possessing combinations of Z/E-alkenes. For the diene substrates, the rate order of the reactions using Ru-1 was Z,Z-1,6-diene > Z,E-1,6-diene > E,E-1,6-diene, while the completely opposite order of E,E-1,6-diene > Z,E-1,6-diene > Z,Z-1,6-diene was exhibited in the case of Ru-2.

  6. Preference of Ruthenium-Based Metathesis Catalysts toward Z- and E-Alkenes as a Guide for Selective Reactions to Alkene Stereoisomers.

    PubMed

    Lee, Jihong; Kim, Kyung Hwan; Lee, Ok Suk; Choi, Tae-Lim; Lee, Hee-Seung; Ihee, Hyotcherl; Sohn, Jeong-Hun

    2016-09-01

    As a guide for selective reactions toward either Z- or E-alkene in a metathesis reaction, the relative preference of metathesis Ru catalysts for each stereoisomer was determined by a method using time-dependent fluorescence quenching. We found that Ru-1 prefers the Z-isomer over the E-isomer, whereas Ru-2 prefers the E-isomer over the Z-isomer. The Z/E-alkene preference of the catalysts precisely predicted the Z/E isomeric selectivity in the metathesis reactions of diene substrates possessing combinations of Z/E-alkenes. For the diene substrates, the rate order of the reactions using Ru-1 was Z,Z-1,6-diene > Z,E-1,6-diene > E,E-1,6-diene, while the completely opposite order of E,E-1,6-diene > Z,E-1,6-diene > Z,Z-1,6-diene was exhibited in the case of Ru-2. PMID:27463964

  7. Modeling SOA formation from alkanes and alkenes in chamber experiments: effect of gas/wall partitioning of organic vapors.

    NASA Astrophysics Data System (ADS)

    Stéphanie La, Yuyi; Camredon, Marie; Ziemann, Paul; Ouzebidour, Farida; Valorso, Richard; Madronich, Sasha; Lee-Taylor, Julia; Hodzic, Alma; Aumont, Bernard

    2014-05-01

    Oxidation products of Intermediate Volatility Organic Compounds (IVOC) are expected to be the major precursors of secondary organic aerosols (SOA). Laboratory experiments were conducted this last decade in the Riverside APRC chamber to study IVOC oxidative mechanisms and SOA formation processes for a large set of linear, branched and cyclic aliphatic hydrocarbons (Ziemann, 2011). This dataset are used here to assess the explicit oxidation model GECKO-A (Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere) (Aumont et al., 2005). The simulated SOA yields agree with the general trends observed in the chamber experiments. They are (i) increasing with the increasing carbon number; (ii) decreasing with increasing methyl branch number; and (iii) increasing for cyclic compounds compared to their corresponding linear analogues. However, simulated SOA yields are systematically overestimated regardless of the precursors, suggesting missing processes in the model. In this study, we assess whether gas-to-wall partitioning of organic vapors can explain these model/observation mismatches (Matsunaga and Ziemann, 2010). First results show that GECKO-A outputs better match the observations when wall uptake of organic vapors is taken into account. Effects of gas/wall partitioning on SOA yields and composition will be presented. Preliminary results suggest that wall uptake is a major process influencing SOA production in the Teflon chambers. References Aumont, B., Szopa, S., Madronich, S.: Modelling the evolution of organic carbon during its gas-phase tropospheric oxidation: development of an explicit model based on a self generating approach. Atmos.Chem.Phys., 5, 2497-2517 (2005). P. J. Ziemann: Effects of molecular structure on the chemistry of aerosol formation from the OH-radical-initiated oxidation of alkanes and alkenes, Int. Rev.Phys.Chem., 30:2, 161-195 (2011). Matsunaga, A., Ziemann, P. J.: Gas-wall partitioning of organic compounds in a Teflon film

  8. Combined Experimental and Computational Investigations of Rhodium-Catalysed C–H Functionalisation of Pyrazoles with Alkenes

    PubMed Central

    Algarra, Andrés G; Davies, David L; Khamker, Qudsia; Macgregor, Stuart A; McMullin, Claire L; Singh, Kuldip; Villa-Marcos, Barbara

    2015-01-01

    Detailed experimental and computational studies have been carried out on the oxidative coupling of the alkenes C2H3Y (Y=CO2Me (a), Ph (b), C(O)Me (c)) with 3-aryl-5-R-pyrazoles (R=Me (1 a), Ph (1 b), CF3 (1 c)) using a [Rh(MeCN)3Cp*][PF6]2/Cu(OAc)2⋅H2O catalyst system. In the reaction of methyl acrylate with 1 a, up to five products (2 aa–6 aa) were formed, including the trans monovinyl product, either complexed within a novel CuI dimer (2 aa) or as the free species (3 aa), and a divinyl species (6 aa); both 3 aa and 6 aa underwent cyclisation by an aza-Michael reaction to give fused heterocycles 4 aa and 5 aa, respectively. With styrene, only trans mono- and divinylation products were observed, whereas with methyl vinyl ketone, a stronger Michael acceptor, only cyclised oxidative coupling products were formed. Density functional theory calculations were performed to characterise the different migratory insertion and β-H transfer steps implicated in the reactions of 1 a with methyl acrylate and styrene. The calculations showed a clear kinetic preference for 2,1-insertion and the formation of trans vinyl products, consistent with the experimental results. PMID:25521823

  9. Torsional Control of Stereoselectivities in Electrophilic Additions and Cycloadditions to Alkenes

    PubMed Central

    Wang, Hao; Houk, K. N.

    2013-01-01

    Torsional effects control the π-facial stereoselectivities of a variety of synthetically important organic reactions. This review surveys theoretical calculations that have led to the understanding of the influence of the torsional effects on several types of stereoselective organic reactions, especially electrophilic additions and cycloadditions to alkenes. PMID:24409340

  10. Evolution of copper(II) as a new alkene amination promoter and catalyst

    PubMed Central

    Chemler, Sherry R.

    2010-01-01

    Copper(II) carboxylates and chiral copper(II) triflate·bis(oxazoline) complexes promote and catalyze intramolecular alkene carboamination, diamination and aminooxygenation reactions, creating an array of nitrogen heterocycles. High diastereoselectivity and enantioselectivity can be achieved in these transformations. This account reviews the discovery and development of these useful and interesting reactions. PMID:21379363

  11. Metal-free direct intramolecular carbotrifluoromethylation of alkenes to functionalized trifluoromethyl azaheterocycles.

    PubMed

    Li, Lei; Deng, Min; Zheng, Sheng-Cai; Xiong, Ya-Ping; Tan, Bin; Liu, Xin-Yuan

    2014-01-17

    The first example of a metal-free direct carbotrifluoromethylation of alkenes using inexpensive TMSCF3 as the CF3 source is described. The methodology not only exhibits high chemoselectivity for this transformation but also expands the substrate scope that is difficult to access by known transition-metal-catalyzed methods. PMID:24351111

  12. Products of the gas-phase reactions of O{sub 3} with alkenes

    SciTech Connect

    Atkinson, R.; Tuazon, E.C.; Aschmann, S.M.

    1995-12-01

    Selected products of the gas-phase reactions of a series of alkenes (1-pentene, 1-hexene, 1-heptene, 1-octene, 2,3-dimethyl-l-butene, cyclopentene and 1-methylcyclohexene) with O{sub 3} have been identified and quantified by gas chromatography and in situ Fourier transform infrared absorption spectroscopy. Because OH radicals are formed in these O{sub 3} reactions, experiments were carried out in the presence of sufficient cyclohexane or n-octane to scavenge > 90 % of the OH radicals formed. OH radical formation yields from the O{sub 3}-alkene reactions were derived from the amounts of cyclohexanone and cyclohexanol formed in O{sub 3}-alkene-cyclohexane-air mixtures. The molar yields of the carbonyls products R{sub 1}C(O)R{sub 2} plus HCHO from the O{sub 3} reactions with the five 1-alkenes (R{sub 1}R{sub 2}C=CH{sub 2}) studied were 1.1 {plus_minus} 0.1, as expected from the presently accepted reaction mechanism.

  13. Highly regio- and enantioselective multiple oxy- and amino-functionalizations of alkenes by modular cascade biocatalysis

    PubMed Central

    Wu, Shuke; Zhou, Yi; Wang, Tianwen; Too, Heng-Phon; Wang, Daniel I. C.; Li, Zhi

    2016-01-01

    New types of asymmetric functionalizations of alkenes are highly desirable for chemical synthesis. Here, we develop three novel types of regio- and enantioselective multiple oxy- and amino-functionalizations of terminal alkenes via cascade biocatalysis to produce chiral α-hydroxy acids, 1,2-amino alcohols and α-amino acids, respectively. Basic enzyme modules 1–4 are developed to convert alkenes to (S)-1,2-diols, (S)-1,2-diols to (S)-α-hydroxyacids, (S)-1,2-diols to (S)-aminoalcohols and (S)-α-hydroxyacids to (S)-α-aminoacids, respectively. Engineering of enzyme modules 1 & 2, 1 & 3 and 1, 2 & 4 in Escherichia coli affords three biocatalysts over-expressing 4–8 enzymes for one-pot conversion of styrenes to the corresponding (S)-α-hydroxyacids, (S)-aminoalcohols and (S)-α-aminoacids in high e.e. and high yields, respectively. The new types of asymmetric alkene functionalizations provide green, safe and useful alternatives to the chemical syntheses of these compounds. The modular approach for engineering multi-step cascade biocatalysis is useful for developing other new types of one-pot biotransformations for chemical synthesis. PMID:27297777

  14. Synthesis of insect pheromones belonging to the group of (Z)-trisubstituted alkenes

    NASA Astrophysics Data System (ADS)

    Grigorieva, Natalia Ya; Tsiklauri, Paata G.

    2000-07-01

    Stereo- and regiocontrolled methods for the construction of a (Z)-trisubstituted C=C bond and for the regiospecific introduction of a chiral fragment are exemplified in total syntheses of insect pheromones belonging to (Z)-trisubstituted alkenes. The bibliography includes 113 references.

  15. Direct Synthesis of Alkenyl Boronic Esters from Unfunctionalized Alkenes: A Boryl-Heck Reaction.

    PubMed

    Reid, William B; Spillane, Jesse J; Krause, Sarah B; Watson, Donald A

    2016-05-01

    We report the first example of a boryl-Heck reaction using an electrophilic boron reagent. This palladium-catalyzed process allows for the conversion of terminal alkenes to trans-alkenyl boronic esters using commercially available catecholchloroborane (catBCl). In situ transesterification allows for rapid access to a variety of boronic esters, amides, and other alkenyl boron adducts. PMID:27104749

  16. Highly Regioselective Radical Amination of Allenes: Direct Synthesis of Allenamides and Tetrasubstituted Alkenes.

    PubMed

    Zhang, Ge; Xiong, Tao; Wang, Zining; Xu, Guoxing; Wang, Xuedan; Zhang, Qian

    2015-10-19

    The first controllable, regioselective radical amination of allenes with N-fluoroarylsulfonimide is described to proceed under very mild reaction conditions. With this methodology, a general and straightforward route for the synthesis of both allenamides and fluorinated tetrasubstituted alkenes was realized from a wide range of terminal and internal allenes.

  17. Catalytic and asymmetric cyclopropanation of alkenes catalysed by rhenium(I) bipyridine and terpyridine tricarbonyl complexes.

    PubMed

    Yeung, Chi-Tung; Teng, Pang-Fei; Yeung, Ho-Lun; Wong, Wing-Tak; Kwong, Hoi-Lun

    2007-12-01

    Re(I) tricarbonyl bipyridine and terpyridine complexes catalyse stereospecific cyclopropanation of alkenes; high selectivity of cyclopropane vs coupling and an ee of 73% and 62% for cis- and trans-cyclopropanes of styrene respectively were achieved with the [Re(L)(CO)(3)(MeCN)]OTf complex (L = chiral C(2)-symmetric terpyridine ligand).

  18. Continuous flow hydrogenation of nitroarenes, azides and alkenes using maghemite-Pd nanocomposites

    EPA Science Inventory

    Maghemite-supported ultra-fine Pd (1-2 nm) nanoparticles, prepared by a simple co-precipitation method, find application in the catalytic continuous flow hydrogenation of nitroarenes, azides, and alkenes wherein they play an important role in reduction of various functional group...

  19. One-Pot Anti-Markovnikov Hydroamination of Unactivated Alkenes by Hydrozirconation and Amination

    PubMed Central

    Strom, Alexandra E.

    2013-01-01

    A one-pot hydroamination of alkenes is reported. The synthesis of primary and secondary amines from unactivated olefins was accomplished in the presence of a variety of functional groups. Hydrozirconation, followed by amination with nitrogen electrophiles, provides exclusive anti-Markovnikov selectivity, and most products are isolated in high yields without the use of column chromatography. PMID:23899320

  20. 40 CFR 721.445 - Substituted ethyl alken-a-mide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.445 Substituted ethyl alken-a-mide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a substituted ethyl...

  1. 40 CFR 721.445 - Substituted ethyl alken-a-mide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.445 Substituted ethyl alken-a-mide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a substituted ethyl...

  2. Tandem isomerization-decarboxylation for converting alkenoic fatty acids into alkenes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We report a facile Ru-catalyzed route to alkenes from alkenoic fatty acids via a readily accessible pre-catalyst [Ru(CO)2RCO2]n. The catalyst apparently functions in a tandem mode by dynamically isomerizing the positions of double bonds in an aliphatic chain and, subsequently, decarboxylating specif...

  3. Silver Iodide-Chitosan Nanotag Induced Biocatalytic Precipitation for Self-Enhanced Ultrasensitive Photocathodic Immunosensor.

    PubMed

    Gong, Lingshan; Dai, Hong; Zhang, Shupei; Lin, Yanyu

    2016-06-01

    In this work, we first exposed that the application of p-type semiconductor, silver iodide-chitosan nanoparticle (SICNP), acted as peroxidase mimetic to catalyze the bioprecipitation reaction for signal-amplification photocathodic immunosensing of human interleukin-6 (IL-6). After immobilization of captured antibody onto a polyethylenimine-functionalized carbon nitride (CN) matrix, SICNPs as photoactive tags and peroxidase mimetics were labeled on secondary antibodies, which were subsequently introduced onto the sensing interface to construct sandwich immunoassay platform through antigen-antibody specific recognition. Due to the matched energy levels between CN and AgI, the photocurrent intensity and photostability of SICNP were dramatically improved with rapid separation and transportation of photogenerated carriers. Moreover, the insoluble product in effective biocatalytic precipitation reaction served as electron acceptor to scavenge the photoexcited electron, leading to great amplification of the photocurrent signal of SICNP again. With the help of multiamplification processes, this photocathodic immunosensor presented a turn-on photoelectrochemical performance for IL-6, which showed wide linear dynamic range from 10(-6) to 10 pg/mL with the ultralow detection limit of 0.737 ag/mL. This work also performed the promising application of SICNP in developing an ultrasensitive, cost-effective, and enzyme-free photocathodic immunosensor for biomarkers. PMID:27180822

  4. Exploiting cell metabolism for biocatalytic whole-cell transamination by recombinant Saccharomyces cerevisiae.

    PubMed

    Weber, Nora; Gorwa-Grauslund, Marie; Carlquist, Magnus

    2014-05-01

    The potential of Saccharomyces cerevisiae for biocatalytic whole-cell transamination was investigated using the kinetic resolution of racemic 1-phenylethylamine (1-PEA) to (R)-1-PEA as a model reaction. As native yeast do not possess any ω-transaminase activity for the reaction, a recombinant yeast biocatalyst was constructed by overexpressing the gene coding for vanillin aminotransferase from Capsicum chinense. The yeast-based biocatalyst could use glucose as the sole co-substrate for the supply of amine acceptor via cell metabolism. In addition, the biocatalyst was functional without addition of the co-factor pyridoxal-5'-phosphate (PLP), which can be explained by a high inherent cellular capacity to sustain PLP-dependent reactions in living cells. In contrast, external PLP supplementation was required when cell viability was low, as it was the case when using pyruvate as a co-substrate. Overall, the results indicate a potential for engineered S. cerevisiae as a biocatalyst for whole-cell transamination and with glucose as the only co-substrate for the supply of amine acceptor and PLP.

  5. Building carbon-carbon bonds using a biocatalytic methanol condensation cycle.

    PubMed

    Bogorad, Igor W; Chen, Chang-Ting; Theisen, Matthew K; Wu, Tung-Yun; Schlenz, Alicia R; Lam, Albert T; Liao, James C

    2014-11-11

    Methanol is an important intermediate in the utilization of natural gas for synthesizing other feedstock chemicals. Typically, chemical approaches for building C-C bonds from methanol require high temperature and pressure. Biological conversion of methanol to longer carbon chain compounds is feasible; however, the natural biological pathways for methanol utilization involve carbon dioxide loss or ATP expenditure. Here we demonstrated a biocatalytic pathway, termed the methanol condensation cycle (MCC), by combining the nonoxidative glycolysis with the ribulose monophosphate pathway to convert methanol to higher-chain alcohols or other acetyl-CoA derivatives using enzymatic reactions in a carbon-conserved and ATP-independent system. We investigated the robustness of MCC and identified operational regions. We confirmed that the pathway forms a catalytic cycle through (13)C-carbon labeling. With a cell-free system, we demonstrated the conversion of methanol to ethanol or n-butanol. The high carbon efficiency and low operating temperature are attractive for transforming natural gas-derived methanol to longer-chain liquid fuels and other chemical derivatives.

  6. Microbiome and Biocatalytic Bacteria in Monkey Cup (Nepenthes Pitcher) Digestive Fluid

    PubMed Central

    Chan, Xin-Yue; Hong, Kar-Wai; Yin, Wai-Fong; Chan, Kok-Gan

    2016-01-01

    Tropical carnivorous plant, Nepenthes, locally known as “monkey cup”, utilises its pitcher as a passive trap to capture insects. It then secretes enzymes into the pitcher fluid to digest the insects for nutrients acquisition. However, little is known about the microbiota and their activity in its pitcher fluid. Eighteen bacteria phyla were detected from the metagenome study in the Nepenthes pitcher fluid. Proteobacteria, Bacteroidetes and Actinobacteria are the dominant phyla in the Nepenthes pitcher fluid. We also performed culturomics approach by isolating 18 bacteria from the Nepenthes pitcher fluid. Most of the bacterial isolates possess chitinolytic, proteolytic, amylolytic, and cellulolytic and xylanolytic activities. Fifteen putative chitinase genes were identified from the whole genome analysis on the genomes of the 18 bacteria isolated from Nepenthes pitcher fluid and expressed for chitinase assay. Of these, six clones possessed chitinase activity. In conclusion, our metagenome result shows that the Nepenthes pitcher fluid contains vast bacterial diversity and the culturomic studies confirmed the presence of biocatalytic bacteria within the Nepenthes pitcher juice which may act in symbiosis for the turn over of insects trapped in the Nepenthes pitcher fluid. PMID:26817720

  7. Characterisation of a Recombinant Patchoulol Synthase Variant for Biocatalytic Production of Terpenes.

    PubMed

    Frister, Thore; Hartwig, Steffen; Alemdar, Semra; Schnatz, Katharina; Thöns, Laura; Scheper, Thomas; Beutel, Sascha

    2015-08-01

    The patchoulol synthase (PTS) is a multi-product sesquiterpene synthases which is the central enzyme for biosynthesis of patchouli essential oil in the patchouli plant. Sesquiterpene synthases catalyse the formation of various complex carbon backbones difficult to approach by organic synthesis. Here, we report the characterisation of a recombinant patchoulol synthase complementary DNA (cDNA) variant (PTS var. 1), exhibiting significant amino acid exchanges compared to the native PTS. The product spectrum using the natural substrate E,E-farnesyl diphosphate (FDP) as well as terpenoid products resulting from conversions employing alternative substrates was analysed by GC-MS. In respect to a potential use as a biocatalyst, important enzymatic parameters such as the optimal reaction conditions, kinetic behaviour and the product selectivity were studied as well. Adjusting the reaction conditions, an increased patchoulol ratio in the recombinant essential oil was achieved. Nevertheless, the ratio remained lower than in plant-derived patchouli oil. As alternative substrates, several prenyl diposphates were accepted and converted in numerous compounds by the PTS var. 1, revealing its great biocatalytic potential. PMID:26100386

  8. Biocatalytic Production of Trehalose from Maltose by Using Whole Cells of Permeabilized Recombinant Escherichia coli.

    PubMed

    Zheng, Zhaojuan; Xu, Ying; Sun, Ye; Mei, Wending; Ouyang, Jia

    2015-01-01

    Trehalose is a non-reducing disaccharide, which can protect proteins, lipid membranes, and cells from desiccation, refrigeration, dehydration, and other harsh environments. Trehalose can be produced by different pathways and trehalose synthase pathway is a convenient, practical, and low-cost pathway for the industrial production of trehalose. In this study, 3 candidate treS genes were screened from genomic databases of Pseudomonas and expressed in Escherichia coli. One of them from P. stutzeri A1501 exhibited the best transformation ability from maltose into trehalose and the least byproduct. Thus, whole cells of this recombinant E. coli were used as biocatalyst for trehalose production. In order to improve the conversion rate of maltose to trehalose, optimization of the permeabilization and biotransformation were carried out. Under optimal conditions, 92.2 g/l trehalose was produced with a high productivity of 23.1 g/(l h). No increase of glucose was detected during the whole course. The biocatalytic process developed in this study might serve as a candidate for the large scale production of trehalose. PMID:26462117

  9. Biocatalytic methanation of hydrogen and carbon dioxide in an anaerobic three-phase system.

    PubMed

    Burkhardt, M; Koschack, T; Busch, G

    2015-02-01

    A new type of anaerobic trickle-bed reactor was used for biocatalytic methanation of hydrogen and carbon dioxide under mesophilic temperatures and ambient pressure in a continuous process. The conversion of gaseous substrates through immobilized hydrogenotrophic methanogenic archaea in a biofilm is a unique feature of this type of reactor. Due to the formation of a three-phase system on the carrier surface and operation as a plug flow reactor without gas recirculation, a complete reaction could be observed. With a methane concentration higher than c(CH4) = 98%, the product gas exhibits a very high quality. A specific methane production of P(CH4) = 1.49 Nm(3)/(m(3)(SV) d) was achieved at a hydraulic loading rate of LR(H2) = 6.0 Nm(3)/(m(3)(SV) d). The relation between trickle flow through the reactor and productivity could be shown. An application for methane enrichment in combination with biogas facilities as a source of carbon dioxide has also been positively proven. PMID:25193088

  10. Building carbon–carbon bonds using a biocatalytic methanol condensation cycle

    PubMed Central

    Bogorad, Igor W.; Chen, Chang-Ting; Theisen, Matthew K.; Wu, Tung-Yun; Schlenz, Alicia R.; Lam, Albert T.; Liao, James C.

    2014-01-01

    Methanol is an important intermediate in the utilization of natural gas for synthesizing other feedstock chemicals. Typically, chemical approaches for building C–C bonds from methanol require high temperature and pressure. Biological conversion of methanol to longer carbon chain compounds is feasible; however, the natural biological pathways for methanol utilization involve carbon dioxide loss or ATP expenditure. Here we demonstrated a biocatalytic pathway, termed the methanol condensation cycle (MCC), by combining the nonoxidative glycolysis with the ribulose monophosphate pathway to convert methanol to higher-chain alcohols or other acetyl-CoA derivatives using enzymatic reactions in a carbon-conserved and ATP-independent system. We investigated the robustness of MCC and identified operational regions. We confirmed that the pathway forms a catalytic cycle through 13C-carbon labeling. With a cell-free system, we demonstrated the conversion of methanol to ethanol or n-butanol. The high carbon efficiency and low operating temperature are attractive for transforming natural gas-derived methanol to longer-chain liquid fuels and other chemical derivatives. PMID:25355907

  11. Building Bridges: Biocatalytic C–C-Bond Formation toward Multifunctional Products

    PubMed Central

    2016-01-01

    Carbon–carbon bond formation is the key reaction for organic synthesis to construct the carbon framework of organic molecules. The review gives a selection of biocatalytic C–C-bond-forming reactions which have been investigated during the last 5 years and which have already been proven to be applicable for organic synthesis. In most cases, the reactions lead to products functionalized at the site of C–C-bond formation (e.g., α-hydroxy ketones, aminoalcohols, diols, 1,4-diketones, etc.) or allow to decorate aromatic and heteroaromatic molecules. Furthermore, examples for cyclization of (non)natural precursors leading to saturated carbocycles are given as well as the stereoselective cyclopropanation of olefins affording cyclopropanes. Although many tools are already available, recent research also makes it clear that nature provides an even broader set of enzymes to perform specific C–C coupling reactions. The possibilities are without limit; however, a big library of variants for different types of reactions is required to have the specific enzyme for a desired specific (stereoselective) reaction at hand. PMID:27398261

  12. Biocatalytic Production of Trehalose from Maltose by Using Whole Cells of Permeabilized Recombinant Escherichia coli

    PubMed Central

    Sun, Ye; Mei, Wending; Ouyang, Jia

    2015-01-01

    Trehalose is a non-reducing disaccharide, which can protect proteins, lipid membranes, and cells from desiccation, refrigeration, dehydration, and other harsh environments. Trehalose can be produced by different pathways and trehalose synthase pathway is a convenient, practical, and low-cost pathway for the industrial production of trehalose. In this study, 3 candidate treS genes were screened from genomic databases of Pseudomonas and expressed in Escherichia coli. One of them from P. stutzeri A1501 exhibited the best transformation ability from maltose into trehalose and the least byproduct. Thus, whole cells of this recombinant E. coli were used as biocatalyst for trehalose production. In order to improve the conversion rate of maltose to trehalose, optimization of the permeabilization and biotransformation were carried out. Under optimal conditions, 92.2 g/l trehalose was produced with a high productivity of 23.1 g/(l h). No increase of glucose was detected during the whole course. The biocatalytic process developed in this study might serve as a candidate for the large scale production of trehalose. PMID:26462117

  13. Silver Iodide-Chitosan Nanotag Induced Biocatalytic Precipitation for Self-Enhanced Ultrasensitive Photocathodic Immunosensor.

    PubMed

    Gong, Lingshan; Dai, Hong; Zhang, Shupei; Lin, Yanyu

    2016-06-01

    In this work, we first exposed that the application of p-type semiconductor, silver iodide-chitosan nanoparticle (SICNP), acted as peroxidase mimetic to catalyze the bioprecipitation reaction for signal-amplification photocathodic immunosensing of human interleukin-6 (IL-6). After immobilization of captured antibody onto a polyethylenimine-functionalized carbon nitride (CN) matrix, SICNPs as photoactive tags and peroxidase mimetics were labeled on secondary antibodies, which were subsequently introduced onto the sensing interface to construct sandwich immunoassay platform through antigen-antibody specific recognition. Due to the matched energy levels between CN and AgI, the photocurrent intensity and photostability of SICNP were dramatically improved with rapid separation and transportation of photogenerated carriers. Moreover, the insoluble product in effective biocatalytic precipitation reaction served as electron acceptor to scavenge the photoexcited electron, leading to great amplification of the photocurrent signal of SICNP again. With the help of multiamplification processes, this photocathodic immunosensor presented a turn-on photoelectrochemical performance for IL-6, which showed wide linear dynamic range from 10(-6) to 10 pg/mL with the ultralow detection limit of 0.737 ag/mL. This work also performed the promising application of SICNP in developing an ultrasensitive, cost-effective, and enzyme-free photocathodic immunosensor for biomarkers.

  14. Cellulose Digestion and Metabolism Induced Biocatalytic Transitions in Anaerobic Microbial Ecosystems

    PubMed Central

    Yamazawa, Akira; Iikura, Tomohiro; Morioka, Yusuke; Shino, Amiu; Ogata, Yoshiyuki; Date, Yasuhiro; Kikuchi, Jun

    2013-01-01

    Anaerobic digestion of highly polymerized biomass by microbial communities present in diverse microbial ecosystems is an indispensable metabolic process for biogeochemical cycling in nature and for industrial activities required to maintain a sustainable society. Therefore, the evaluation of the complicated microbial metabolomics presents a significant challenge. We here describe a comprehensive strategy for characterizing the degradation of highly crystallized bacterial cellulose (BC) that is accompanied by metabolite production for identifying the responsible biocatalysts, including microorganisms and their metabolic functions. To this end, we employed two-dimensional solid- and one-dimensional solution-state nuclear magnetic resonance (NMR) profiling combined with a metagenomic approach using stable isotope labeling. The key components of biocatalytic reactions determined using a metagenomic approach were correlated with cellulose degradation and metabolic products. The results indicate that BC degradation was mediated by cellulases that contain carbohydrate-binding modules and that belong to structural type A. The degradation reactions induced the metabolic dynamics of the microbial community and produced organic compounds, such as acetic acid and propionic acid, mainly metabolized by clostridial species. This combinatorial, functional and structural metagenomic approach is useful for the comprehensive characterization of biomass degradation, metabolic dynamics and their key components in diverse ecosystems. PMID:24958386

  15. Microbiome and Biocatalytic Bacteria in Monkey Cup (Nepenthes Pitcher) Digestive Fluid.

    PubMed

    Chan, Xin-Yue; Hong, Kar-Wai; Yin, Wai-Fong; Chan, Kok-Gan

    2016-01-01

    Tropical carnivorous plant, Nepenthes, locally known as "monkey cup", utilises its pitcher as a passive trap to capture insects. It then secretes enzymes into the pitcher fluid to digest the insects for nutrients acquisition. However, little is known about the microbiota and their activity in its pitcher fluid. Eighteen bacteria phyla were detected from the metagenome study in the Nepenthes pitcher fluid. Proteobacteria, Bacteroidetes and Actinobacteria are the dominant phyla in the Nepenthes pitcher fluid. We also performed culturomics approach by isolating 18 bacteria from the Nepenthes pitcher fluid. Most of the bacterial isolates possess chitinolytic, proteolytic, amylolytic, and cellulolytic and xylanolytic activities. Fifteen putative chitinase genes were identified from the whole genome analysis on the genomes of the 18 bacteria isolated from Nepenthes pitcher fluid and expressed for chitinase assay. Of these, six clones possessed chitinase activity. In conclusion, our metagenome result shows that the Nepenthes pitcher fluid contains vast bacterial diversity and the culturomic studies confirmed the presence of biocatalytic bacteria within the Nepenthes pitcher juice which may act in symbiosis for the turn over of insects trapped in the Nepenthes pitcher fluid. PMID:26817720

  16. Biocatalytic methanation of hydrogen and carbon dioxide in an anaerobic three-phase system.

    PubMed

    Burkhardt, M; Koschack, T; Busch, G

    2015-02-01

    A new type of anaerobic trickle-bed reactor was used for biocatalytic methanation of hydrogen and carbon dioxide under mesophilic temperatures and ambient pressure in a continuous process. The conversion of gaseous substrates through immobilized hydrogenotrophic methanogenic archaea in a biofilm is a unique feature of this type of reactor. Due to the formation of a three-phase system on the carrier surface and operation as a plug flow reactor without gas recirculation, a complete reaction could be observed. With a methane concentration higher than c(CH4) = 98%, the product gas exhibits a very high quality. A specific methane production of P(CH4) = 1.49 Nm(3)/(m(3)(SV) d) was achieved at a hydraulic loading rate of LR(H2) = 6.0 Nm(3)/(m(3)(SV) d). The relation between trickle flow through the reactor and productivity could be shown. An application for methane enrichment in combination with biogas facilities as a source of carbon dioxide has also been positively proven.

  17. Expedient synthesis of C-aryl carbohydrates by consecutive biocatalytic benzoin and aldol reactions.

    PubMed

    Hernández, Karel; Parella, Teodor; Joglar, Jesús; Bujons, Jordi; Pohl, Martina; Clapés, Pere

    2015-02-16

    The introduction of aromatic residues connected by a C-C bond into the non-reducing end of carbohydrates is highly significant for the development of innovative structures with improved binding affinity and selectivity (e.g., C-aril-sLex). In this work, an expedient asymmetric "de novo" synthetic route to new aryl carbohydrate derivatives based on two sequential stereoselectively biocatalytic carboligation reactions is presented. First, the benzoin reaction of aromatic aldehydes to dimethoxyacetaldehyde is conducted, catalyzed by benzaldehyde lyase from Pseudomonas fluorescens biovar I. Then, the α-hydroxyketones formed are reduced by using NaBH4 yielding the anti diol. After acetal hydrolysis, the aldol addition of dihydroxyacetone, hydroxyacetone, or glycolaldehyde catalyzed by the stereocomplementary D-fructose-6-phosphate aldolase and L-rhamnulose-1-phosphate aldolase is performed. Both aldolases accept unphosphorylated donor substrates, avoiding the need of handling the phosphate group that the dihydroxyacetone phosphate-dependent aldolases require. In this way, 6-C-aryl-L-sorbose, 6-C-aryl-L-fructose, 6-C-aryl-L-tagatose, and 5-C-aryl-L-xylose derivatives are prepared by using this methodology.

  18. Discovery and molecular and biocatalytic properties of hydroxynitrile lyase from an invasive millipede, Chamberlinius hualienensis

    PubMed Central

    Dadashipour, Mohammad; Ishida, Yuko; Yamamoto, Kazunori; Asano, Yasuhisa

    2015-01-01

    Hydroxynitrile lyase (HNL) catalyzes the degradation of cyanohydrins and causes the release of hydrogen cyanide (cyanogenesis). HNL can enantioselectively produce cyanohydrins, which are valuable building blocks for the synthesis of fine chemicals and pharmaceuticals, and is used as an important biocatalyst in industrial biotechnology. Currently, HNLs are isolated from plants and bacteria. Because industrial biotechnology requires more efficient and stable enzymes for sustainable development, we must continuously explore other potential enzyme sources for the desired HNLs. Despite the abundance of cyanogenic millipedes in the world, there has been no precise study of the HNLs from these arthropods. Here we report the isolation of HNL from the cyanide-emitting invasive millipede Chamberlinius hualienensis, along with its molecular properties and application in biocatalysis. The purified enzyme displays a very high specific activity in the synthesis of mandelonitrile. It is a glycosylated homodimer protein and shows no apparent sequence identity or homology with proteins in the known databases. It shows biocatalytic activity for the condensation of various aromatic aldehydes with potassium cyanide to produce cyanohydrins and has high stability over a wide range of temperatures and pH values. It catalyzes the synthesis of (R)-mandelonitrile from benzaldehyde with a 99% enantiomeric excess, without using any organic solvents. Arthropod fauna comprise 80% of terrestrial animals. We propose that these animals can be valuable resources for exploring not only HNLs but also diverse, efficient, and stable biocatalysts in industrial biotechnology. PMID:26261304

  19. Separation, Immobilization, and Biocatalytic Utilization of Proteins by a Supramolecular Membrane

    PubMed Central

    Krieg, Elisha; Albeck, Shira; Weissman, Haim; Shimoni, Eyal; Rybtchinski, Boris

    2013-01-01

    Membrane separation of biomolecules and their application in biocatalysis is becoming increasingly important for biotechnology, demanding the development of new biocompatible materials with novel properties. In the present study, an entirely noncovalent water-based material is used as a membrane for size-selective separation, immobilization, and biocatalytic utilization of proteins. The membrane shows stable performance under physiological conditions, allowing filtration of protein mixtures with a 150 kDa molecular weight cutoff (∼8 nm hydrodynamic diameter cutoff). Due to the biocompatibility of the membrane, filtered proteins stay functionally active and retained proteins can be partially recovered. Upon filtration, large enzymes become immobilized within the membrane. They exhibit stable activity when subjected to a constant flux of substrates for prolonged periods of time, which can be used to carry out heterogeneous biocatalysis. The noncovalent membrane material can be easily disassembled, purified, reassembled, and reused, showing reproducible performance after recycling. The robustness, recyclability, versatility, and biocompatibility of the supramolecular membrane may open new avenues for manipulating biological systems. PMID:23675461

  20. Anti-Markovnikov Oxidation of β-Alkyl Styrenes with H2O as the Terminal Oxidant.

    PubMed

    Zhang, Guoting; Hu, Xia; Chiang, Chien-Wei; Yi, Hong; Pei, Pengkun; Singh, Atul K; Lei, Aiwen

    2016-09-21

    Oxygenation of alkenes is one of the most straightforward routes for the construction of carbonyl compounds. Wacker oxidation provides a broadly useful strategy to convert the mineral oil into higher value-added carbonyl chemicals. However, the conventional Wacker chemistry remains problematic, such as the poor activity for internal alkenes, the lack of anti-Markovnikov regioselectivity, and the high cost and chemical waste resulted from noble metal catalysts and stoichiometric oxidant. Here, we describe an unprecedented dehydrogenative oxygenation of β-alkyl styrenes and their derivatives with water under external-oxidant-free conditions by utilizing the synergistic effect of photocatalysis and proton-reduction catalysis that can address these challenges. This dual catalytic system possesses the single anti-Markovnikov selectivity due to the property of the visible-light-induced alkene radical cation intermediate. PMID:27595272

  1. QUANTIFICATION OF FUGITIVE REACTIVE ALKENE EMISSIONS FROM PETROCHEMICAL PLANTS WITH PERFLUOROCARBON TRACERS.

    SciTech Connect

    SENUM,G.I.; DIETZ,R.N.

    2004-06-30

    Recent studies demonstrate the impact of fugitive emissions of reactive alkenes on the atmospheric chemistry of the Houston Texas metropolitan area (1). Petrochemical plants located in and around the Houston area emit atmospheric alkenes, such as ethene, propene and 1,3-butadiene. The magnitude of emissions is a major uncertainty in assessing their effects. Even though the petrochemical industry reports that fugitive emissions of alkenes have been reduced to less than 0.1% of daily production, recent measurement data, obtained during the TexAQS 2000 experiment indicates that emissions are perhaps a factor of ten larger than estimated values. Industry figures for fugitive emissions are based on adding up estimated emission factors for every component in the plant to give a total estimated emission from the entire facility. The dramatic difference between estimated and measured rates indicates either that calculating emission fluxes by summing estimates for individual components is seriously flawed, possibly due to individual components leaking well beyond their estimated tolerances, that not all sources of emissions for a facility are being considered in emissions estimates, or that there are known sources of emissions that are not being reported. This experiment was designed to confirm estimates of reactive alkene emissions derived from analysis of the TexAQS 2000 data by releasing perfluorocarbon tracers (PFTs) at a known flux from a petrochemical plant and sampling both the perfluorocarbon tracer and reactive alkenes downwind using the Piper-Aztec research aircraft operated by Baylor University. PFTs have been extensively used to determine leaks in pipelines, air infiltration in buildings, and to characterize the transport and dispersion of air parcels in the atmosphere. Over 20 years of development by the Tracer Technology Center (TTC) has produced a range of analysis instruments, field samplers and PFT release equipment that have been successfully deployed in a

  2. Upgrading light hydrocarbons via tandem catalysis: a dual homogeneous Ta/Ir system for alkane/alkene coupling.

    PubMed

    Leitch, David C; Lam, Yan Choi; Labinger, Jay A; Bercaw, John E

    2013-07-17

    Light alkanes and alkenes are abundant but are underutilized as energy carriers because of their high volatility and low energy density. A tandem catalytic approach for the coupling of alkanes and alkenes has been developed in order to upgrade these light hydrocarbons into heavier fuel molecules. This process involves alkane dehydrogenation by a pincer-ligated iridium complex and alkene dimerization by a Cp*TaCl2(alkene) catalyst. These two homogeneous catalysts operate with up to 60/30 cooperative turnovers (Ir/Ta) in the dimerization of 1-hexene/n-heptane, giving C13/C14 products in 40% yield. This dual system can also effect the catalytic dimerization of n-heptane (neohexene as the H2 acceptor) with cooperative turnover numbers of 22/3 (Ir/Ta).

  3. A simple and facile Heck-type arylation of alkenes with diaryliodonium salts using magnetically recoverable Pd-catalyst

    EPA Science Inventory

    The Heck-type arylation of alkenes was achieved in aqueous polyethylene glycol using a magnetically recoverable heterogenized palladium catalyst employing diaryliodonium salts under ambient conditions. The benign reaction medium and the stability of the catalyst are the salient f...

  4. Palladium Catalyzed Intermolecular Aminoacetoxylation of Alkenes and the Influence of PhI(OAc)2 on Aminopalladation Stereoselectivity

    PubMed Central

    Martínez, Claudio; Wu, Yichen; Weinstein, Adam B.; Stahl, Shannon S.; Liu, Guosheng; Muñiz, Kilian

    2013-01-01

    A modified protocol has been identified for Pd-catalyzed intermolecular aminoacetoxylation of terminal and internal alkenes that enables the alkene to be used as the limiting reagent. The results prompt a reassessment of the stereochemical course of these reactions. X-ray crystallographic characterization of two of the products, together with isotopic labeling studies, show that the amidopalladation step switches from a cis-selective process under aerobic conditions to a trans-selective process in the presence of diacetoxyiodobenzene. PMID:23734834

  5. Alkene synthesis through transition metal-catalyzed cross-coupling of N-tosylhydrazones.

    PubMed

    Zhang, Yan; Wang, Jianbo

    2012-01-01

    In this chapter, alkene synthesis based on the reaction of N-tosylhydrazones is described. The reactivity of tosylhydrazones is determined by either the acidity of α-proton and hydrazone proton or the electropositivity of the carbon of C=N bond. This leads to diverse reactivities and a series of N-tosylhydrazone-based olefination methodologies. Both non-catalytic and transition metal-catalyzed olefinations from N-tosylhydrazones are introduced in this chapter. Most of the transition metal-catalyzed reactions proceed via metal carbene transformations. The synthesis of alkenes through Pd-catalyzed cross-coupling reactions of N-tosylhydrazones is particularly attractive and will be discussed in detail.

  6. Metallacycle-Mediated Cross-Coupling with Substituted and Electronically Unactivated Alkenes

    PubMed Central

    Reichard, Holly A.

    2011-01-01

    This perspective surveys the history of- and recent advances in- metallacycle-mediated coupling chemistry of substituted alkenes. While the reaction of preformed metal–π complexes with ethylene was reported nearly 30 years ago, the generalization of this mode of bimolecular C–C bond formation to the regio- and stereoselective union of complex substrates has only recently begun to emerge. This perspective discusses early observations in this area, the challenges associated with controlling such processes, the evolution of a general strategy to overcome these challenges, and a summary of highly regio- and stereoselective convergent coupling reactions that are currently available by metallacycle-mediated cross-coupling with substituted alkenes. PMID:21436986

  7. Catalytic asymmetric carbon-carbon bond formation using alkenes as alkylmetal equivalents.

    PubMed

    Maksymowicz, Rebecca M; Roth, Philippe M C; Fletcher, Stephen P

    2012-08-01

    Catalytic asymmetric conjugate addition reactions with organometallic reagents are powerful reactions in synthetic chemistry. Procedures that use non-stabilized carbanions have been developed extensively, but these suffer from a number of limitations that prevent their use in many situations. Here, we report that alkylmetal species generated in situ from alkenes can be used in highly enantioselective 1,4-addition initiated by a copper catalyst. Using alkenes as starting materials is desirable because they are readily available and have favourable properties when compared to pre-made organometallics. High levels of enantioselectivity are observed at room temperature in a range of solvents, and the reaction tolerates functional groups that are not compatible with comparable methods-a necessary prerequisite for efficient and protecting-group-free strategies for synthesis. PMID:22824897

  8. Catalytic asymmetric carbon-carbon bond formation using alkenes as alkylmetal equivalents

    NASA Astrophysics Data System (ADS)

    Maksymowicz, Rebecca M.; Roth, Philippe M. C.; Fletcher, Stephen P.

    2012-08-01

    Catalytic asymmetric conjugate addition reactions with organometallic reagents are powerful reactions in synthetic chemistry. Procedures that use non-stabilized carbanions have been developed extensively, but these suffer from a number of limitations that prevent their use in many situations. Here, we report that alkylmetal species generated in situ from alkenes can be used in highly enantioselective 1,4-addition initiated by a copper catalyst. Using alkenes as starting materials is desirable because they are readily available and have favourable properties when compared to pre-made organometallics. High levels of enantioselectivity are observed at room temperature in a range of solvents, and the reaction tolerates functional groups that are not compatible with comparable methods—a necessary prerequisite for efficient and protecting-group-free strategies for synthesis.

  9. Mechanistic interpretation of selective catalytic hydrogenation and isomerization of alkenes and dienes by ligand deactivated Pd nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhu, Jie S.; Shon, Young-Seok

    2015-10-01

    Unsupported thiolate-capped palladium nanoparticle catalysts are found to be highly substrate-selective for alkene hydrogenation and isomerization. Steric and poisoning effects from thiolate ligands on the nanoparticle surface control reactivity and selectivity by influencing alkene adsorption and directing either di-σ or mono-σ bond formation. The presence of overlapping p orbitals and α protons in alkenes greatly influences the catalytic properties of deactivated palladium nanoparticles leading to easily predictable hydrogenation or isomerization products.Unsupported thiolate-capped palladium nanoparticle catalysts are found to be highly substrate-selective for alkene hydrogenation and isomerization. Steric and poisoning effects from thiolate ligands on the nanoparticle surface control reactivity and selectivity by influencing alkene adsorption and directing either di-σ or mono-σ bond formation. The presence of overlapping p orbitals and α protons in alkenes greatly influences the catalytic properties of deactivated palladium nanoparticles leading to easily predictable hydrogenation or isomerization products. Electronic supplementary information (ESI) available: Supplementary figures, methods, materials, and characterization data. See DOI: 10.1039/c5nr05090a

  10. Copper-catalyzed oxyamination of electron-deficient alkenes with N-acyloxyamines.

    PubMed

    Ren, Shichao; Song, Shengjin; Ye, Lu; Feng, Chao; Loh, Teck-Peng

    2016-08-16

    A Cu(i)-catalyzed direct intermolecular oxyamination of electron deficient alkenes is disclosed. This process is characterized by difunctionalization of a variety of α,β-unsaturated ketones with easily available N-acyloxyamine reagents as both amine and oxygen donors, which delivers ester derivatives of β-amino alcohols in good yields as well as with high regioselectivity. Control studies suggested the involvement of alkyl radical species on the way of product formation. PMID:27481485

  11. Iron-catalyzed 1,2-addition of perfluoroalkyl iodides to alkynes and alkenes.

    PubMed

    Xu, Tao; Cheung, Chi Wai; Hu, Xile

    2014-05-01

    Iron catalysis has been developed for the intermolecular 1,2-addition of perfluoroalkyl iodides to alkynes and alkenes. The catalysis has a wide substrate scope and high functional-group tolerance. A variety of perfluoroalkyl iodides including CF3 I can be employed. The resulting perfluoroalkylated alkyl and alkenyl iodides can be further functionalized by cross-coupling reactions. This methodology provides a straightforward and streamlined access to perfluoroalkylated organic molecules.

  12. Alkenes as Chelating Groups in Diastereoselective Additions of Organometallics to Ketones

    PubMed Central

    2015-01-01

    Alkenes have been discovered to be chelating groups to Zn(II), enforcing highly stereoselective additions of organozincs to β,γ-unsaturated ketones. 1H NMR studies and DFT calculations provide support for this surprising chelation mode. The results expand the range of coordinating groups for chelation-controlled carbonyl additions from heteroatom Lewis bases to simple C–C double bonds, broadening the 60 year old paradigm. PMID:25328269

  13. Copper-catalyzed oxyamination of electron-deficient alkenes with N-acyloxyamines.

    PubMed

    Ren, Shichao; Song, Shengjin; Ye, Lu; Feng, Chao; Loh, Teck-Peng

    2016-08-16

    A Cu(i)-catalyzed direct intermolecular oxyamination of electron deficient alkenes is disclosed. This process is characterized by difunctionalization of a variety of α,β-unsaturated ketones with easily available N-acyloxyamine reagents as both amine and oxygen donors, which delivers ester derivatives of β-amino alcohols in good yields as well as with high regioselectivity. Control studies suggested the involvement of alkyl radical species on the way of product formation.

  14. A Cu/Pd Cooperative Catalysis for Enantioselective Allylboration of Alkenes.

    PubMed

    Jia, Tao; Cao, Peng; Wang, Bing; Lou, Yazhou; Yin, Xuemei; Wang, Min; Liao, Jian

    2015-11-01

    A cooperative Cu/Pd-catalyzed asymmetric three-component reaction of styrenes, B2(pin)2, and allyl carbonates was reported. This reaction, in the presence of chiral CuOAc/SOP and achiral Pd(dppf)Cl2 catalysts, occurs smoothly with high enantioselectivities (up to 97% ee) . The allylboration products, which contain alkene (or diene) unite and alkylboron group, are easily functionalized. The utility of this protocol was demonstrated through the synthesis of an antipsychotic drug, (-)-preclamol. PMID:26458555

  15. Isolated CH stretching frequencies, bond lengths and dissociation energies in some haloalkanes and alkenes

    NASA Astrophysics Data System (ADS)

    Mackenzie, M. W.

    Isolated CH stretching frequencies (ν isCH) have been obtained for a variety of haloalkanes and alkenes. These have been used to predict CH bond lengths, dissociation energies and force constants. Use of substituent effect S values from previous studies to predict ν isCH demonstrates that the effects of α- and β-substitution by halogens are approximately additive in the case of the haloalkenes but non-additive for the alkanes.

  16. Branch-Selective Alkene Hydroarylation by Cooperative Destabilization: Iridium-Catalyzed ortho-Alkylation of Acetanilides.

    PubMed

    Crisenza, Giacomo E M; Sokolova, Olga O; Bower, John F

    2015-12-01

    An iridium(I) catalyst system, modified with the wide-bite-angle and electron-deficient bisphosphine d(F) ppb (1,4-bis(di(pentafluorophenyl)phosphino)butane) promotes highly branch-selective hydroarylation reactions between diverse acetanilides and aryl- or alkyl-substituted alkenes. This provides direct and ortho-selective access to synthetically challenging anilines, and addresses long-standing issues associated with related Friedel-Crafts alkylations. PMID:26490739

  17. Alkene Chemoselectivity in Ruthenium-Catalyzed Z-Selective Olefin Metathesis

    PubMed Central

    Cannon, Jeffrey S.

    2013-01-01

    Chelated ruthenium catalysts have achieved highly chemoselective olefin metathesis reactions. Terminal and internal Z olefins were selectively reacted in the presence of internal E olefins. Products were produced in good yield and high stereoselectivity for formation of a new Z olefin. No products of metathesis with the internal E olefin were observed. Chemoselectivity for terminal olefins was also observed over both sterically hindered and electronically deactivated alkenes. PMID:23832646

  18. Versatile Enantioselective Synthesis of Functionalized Lactones via Copper-Catalyzed Radical Oxyfunctionalization of Alkenes.

    PubMed

    Zhu, Rong; Buchwald, Stephen L

    2015-07-01

    A versatile method for the rapid synthesis of diverse enantiomerically enriched lactones has been developed based on Cu-catalyzed enantioselective radical oxyfunctionalization of alkenes. The scope of this strategy encompasses a series of enantioselective difunctionalization reactions: oxyazidation, oxysulfonylation, oxyarylation, diacyloxylation, and oxyalkylation. These reactions provide straightforward access to a wide range of useful chiral lactone building blocks containing tetrasubstituted stereogenic centers, which are hard to access traditionally.

  19. Branch-Selective Alkene Hydroarylation by Cooperative Destabilization: Iridium-Catalyzed ortho-Alkylation of Acetanilides

    PubMed Central

    Crisenza, Giacomo E M; Sokolova, Olga O; Bower, John F

    2015-01-01

    An iridium(I) catalyst system, modified with the wide-bite-angle and electron-deficient bisphosphine dFppb (1,4-bis(di(pentafluorophenyl)phosphino)butane) promotes highly branch-selective hydroarylation reactions between diverse acetanilides and aryl- or alkyl-substituted alkenes. This provides direct and ortho-selective access to synthetically challenging anilines, and addresses long-standing issues associated with related Friedel–Crafts alkylations. PMID:26490739

  20. Biocatalytic properties of a recombinant Fusarium proliferatum lactonase with significantly enhanced production by optimal expression in Escherichia coli.

    PubMed

    Chen, Bing; Fan, Li-Qiang; Xu, Jian-He; Zhao, Jian; Zhang, Xian; Ouyang, Li-Ming

    2010-10-01

    The levo-lactonase gene of Fusarium proliferatum ECU2002 (EC3.1.1.25) was cloned and expressed in Escherichia coli JM109 (DE3) for biocatalytic resolution of industrially important chiral lactones, including DL-pantoyl lactone which was a key precursor to calcium D-pantothenate. By increasing the biomass concentration and lowering the inducer (isopropyl-beta-D-thiogalactoside) concentration and induction temperature, the lactonase production was significantly enhanced up to 20 kU/L, which was 20 times higher than that of wild-type strain F. proliferatum ECU2002. The recombinant Fusarium lactonase was purified using immobilized metal affinity chromatography, and its SDS-PAGE revealed a molecular mass of 50 kDa for the recombinant protein, suggesting that the enzyme was a simplex protein. Furthermore, biocatalytic properties of the recombinant lactonase were investigated, including kinetic parameters, additive's effect, and substrate specificity. The results reported in this paper provide a feasible method to make the whole cells of E. coli JM109 (DE3) expressing lactonase gene to be a highly efficient and easy-to-make biocatalyst for asymmetric synthesis of chiral compounds. PMID:19876606

  1. Terminal alkenes as versatile chemical reporter groups for metabolic oligosaccharide engineering.

    PubMed

    Späte, Anne-Katrin; Schart, Verena F; Schöllkopf, Sophie; Niederwieser, Andrea; Wittmann, Valentin

    2014-12-01

    The Diels-Alder reaction with inverse electron demand (DAinv reaction) of 1,2,4,5-tetrazines with electron rich or strained alkenes was proven to be a bioorthogonal ligation reaction that proceeds fast and with high yields. An important application of the DAinv reaction is metabolic oligosaccharide engineering (MOE) which allows the visualization of glycoconjugates in living cells. In this approach, a sugar derivative bearing a chemical reporter group is metabolically incorporated into cellular glycoconjugates and subsequently derivatized with a probe by means of a bioorthogonal ligation reaction. Here, we investigated a series of new mannosamine and glucosamine derivatives with carbamate-linked side chains of varying length terminated by alkene groups and their suitability for labeling cell-surface glycans. Kinetic investigations showed that the reactivity of the alkenes in DAinv reactions increases with growing chain length. When applied to MOE, one of the compounds, peracetylated N-butenyloxycarbonylmannosamine, was especially well suited for labeling cell-surface glycans. Obviously, the length of its side chain represents the optimal balance between incorporation efficiency and speed of the labeling reaction. Sialidase treatment of the cells before the bioorthogonal labeling reaction showed that this sugar derivative is attached to the glycans in form of the corresponding sialic acid derivative and not epimerized to another hexosamine derivative to a considerable extent.

  2. Regioselective and Stereospecific Dehydrogenative Annulation Utilizing Silylium Ion-Activated Alkenes.

    PubMed

    Arii, Hidekazu; Yano, Yuto; Nakabayashi, Kenichi; Yamaguchi, Syuhei; Yamamura, Masaki; Mochida, Kunio; Kawashima, Takayuki

    2016-08-01

    Treatment of dialkylbenzylsilanes (1) with trityl tetrakis(pentafluorophenyl)borate (TPFPB) afforded the corresponding silylium ions in equilibrium with their intra- or intermolecular π-complexes, which underwent dehydrogenative annulation with various alkenes to form 1,2,3,4-tetrahydro-2-silanaphthalenes (4) in up to 82% isolated yield. Sterically bulkier substituents on the silicon atom tended to increase the yield of cyclic products 4. The annulation products retained the stereochemistry in cases of the reactions using internal alkenes. The use of diisopropyl(1-naphthyl)silane (2) instead of 1 also resulted in annulation to obtain the 2,3-dihydro-1-sila-1H-phenalene derivatives 6. Electrophilic aromatic substitution at the 8-position was predominant, despite the two potentially reactive positions on the naphthyl group. The steric hindrance of the naphthyl group prevented addition of the cis-alkene to the silylium ion, which would considerably decrease yields of the desired products from 2 compared to those from 1. PMID:27404297

  3. Pressure-dependent OH yields in alkene + HO2 reactions: a theoretical study.

    PubMed

    Zádor, Judit; Klippenstein, Stephen J; Miller, James A

    2011-09-15

    The major bimolecular product of alkyl + O(2) reactions is alkene + hydroperoxyl radical (HO(2)), but in the reverse direction, the reactants are reformed to a very limited extent only. The most important products of the alkene + HO(2) reactions are alkylperoxy radical (ROO(•)), hydroxyl radical (OH) + cyclic ether, and the corresponding hydroperoxyalkyl ((•)QOOH) species. Moreover, abstraction of allylic hydrogens can compete with the addition, further complicating the possible outcome of this reaction type and its effect on low-temperature combustion chemistry. In this paper, six alkene + HO(2) reactions and the reaction between an unsaturated oxygenate and HO(2) are studied based on previously established potential energy surfaces. The studied unsaturated compounds are ethene, propene, 1-butene, trans-2-butene, isobutene, cyclohexene, and vinyl alcohol. Using multiwell master equations, temperature- (300-1200 K) and pressure-dependent rate coefficients and branching fractions are calculated for these reactions. The importance of this reaction type for the combustion of unsaturated compounds is also assessed, and we show that, to get reliable results, it is important to include the pressure-dependence of the rate coefficients in the calculations. PMID:21819062

  4. Mechanistic Analysis and Optimization of the Copper-Catalyzed Enantioselective Intramolecular Alkene Aminooxygenation

    PubMed Central

    Paderes, Monissa C.; Keister, Jerome B.; Chemler, Sherry R.

    2013-01-01

    The catalytic asymmetric aminooxygenation of alkenes provides an efficient and straightforward approach to prepare chiral vicinal amino alcohols. We have reported a copper(II)-catalyzed enantioselective intramolecular alkene aminooxygenation, using (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) as the oxygen source, which results in the synthesis of chiral indolines and pyrrolidines. Herein we disclose that kinetics studies indicate the reaction is first order both in substrate and the [Cu(R,R)-Ph-bis(oxazoline)]OTf2 catalyst, and zero order in TEMPO. Furthermore, kinetic isotope effect studies support that the cis aminocupration step, the addition of N-Cu across the alkene, is the rate-limiting step. Subsequent formation of a carbon radical intermediate, and direct carbon radical trapping with TEMPO is the indicated mechanism for the C-O bond formation as suggested by a deuterium labeling experiment. A ligand screen revealed that C(4)-phenyl substitution on the bis(oxazoline) is optimal for high asymmetric induction. The size of the substrate’s N-sulfonyl group also influences the enantioselectivity of the reaction. The preparative scale catalytic aminooxygenation reaction (gram scale) was demonstrated and an unexpected dependence on reaction temperature was uncovered on the larger scale reaction. PMID:23244027

  5. Mechanistic analysis and optimization of the copper-catalyzed enantioselective intramolecular alkene aminooxygenation.

    PubMed

    Paderes, Monissa C; Keister, Jerome B; Chemler, Sherry R

    2013-01-18

    The catalytic asymmetric aminooxygenation of alkenes provides an efficient and straightforward approach to prepare chiral vicinal amino alcohols. We have reported a copper(II)-catalyzed enantioselective intramolecular alkene aminooxygenation, using (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) as the oxygen source, which results in the synthesis of chiral indolines and pyrrolidines. Herein we disclose that kinetics studies indicate the reaction is first order both in substrate and the [Cu(R,R)-Ph-bis(oxazoline)]OTf(2) catalyst and zero order in TEMPO. Furthermore, kinetic isotope effect studies support that the cis-aminocupration step, the addition of N-Cu across the alkene, is the rate-limiting step. Subsequent formation of a carbon radical intermediate and direct carbon radical trapping with TEMPO is the indicated mechanism for the C-O bond formation as suggested by a deuterium labeling experiment. A ligand screen revealed that C(4)-phenyl substitution on the bis(oxazoline) is optimal for high asymmetric induction. The size of the substrate's N-sulfonyl group also influences the enantioselectivity of the reaction. The preparative-scale catalytic aminooxygenation reaction (gram scale) was demonstrated, and an unexpected dependence on reaction temperature was uncovered on the larger scale reaction. PMID:23244027

  6. Stereospecific Synthesis of Alkenes by Eliminative Cross-Coupling of Enantioenriched sp(3) -Hybridized Carbenoids.

    PubMed

    Wu, Zhenhua; Sun, Xun; Potter, Kristin; Cao, Yang; Zakharov, Lev N; Blakemore, Paul R

    2016-09-26

    1-Aryl-1,2-dialkylethenes were generated by a sequence of electrophilic substitution, 1,2-metalate rearrangement, and β-elimination initiated by the addition of enantioenriched α-(carbamoyloxy)alkylboronates to enantioenriched lithiated carbamates. The carbenoid stereochemical pairing [i.e., "like"=(S)+(S) or "unlike"=(S)+(R)] and the elimination mechanism (syn or anti), not substituent effects, determined the configuration of the trisubstituted alkene target. For example, (Z)-2,5-diphenyl-2-pentene was produced in 70 % yield with E/Z=5:95 by a like combination of Li and B carbenoids and syn (thermal) elimination whereas the E isomer was obtained in the same yield with E/Z>98:2 by an otherwise identical process involving an unlike stereochemical pairing. The concept elaborated overcomes an intrinsic limitation of traditional strategies for direct connective alkene synthesis, which cannot realize meaningful stereochemical bias unless the alkene substituents are strongly differentiated. PMID:27585188

  7. 1,3-Diferuloyl-sn-glycerol from the biocatalytic transesterification of ethyl 4-hydroxy-3-methoxy cinnamic acid (ethyl ferulate) and soybean oil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    1,3-Diferuloyl-sn-glycerol is a natural plant component found ubiquitously throughout the plant kingdom, possessing ultraviolet adsorbing and antioxidant properties. Diferuloyl glycerol was synthesized and isolated as a byproduct in up to 5% yield from the pilot plant scale packed-bed, biocatalytic...

  8. Gas chromatographic-mass spectrometric characterization of all acyclic C5-C7 alkenes from fluid catalytic cracked gasoline using polydimethylsiloxane and squalane stationary phases.

    PubMed

    Soják, Ladislav; Addová, Gabriela; Kubinec, Róbert; Kraus, Angelika; Hu, Gengyuan

    2002-02-15

    Published retention indices of acyclic alkenes C5-C7 on squalane and polydimethylsiloxane as stationary phases were investigated, and reliable retention indices of alkenes from various sources were converted to separation systems used in a laboratory. Retention indices measured on available authentic commercial alkenes and on alkenic fraction of gasoline, published retention indices as well as means of GC-MS were used for verification of calculated retention indices. Retention of some gas chromatographic unseparated isomer pairs was obtained by mass spectrometric deconvolution using a specific single-ion monitoring. On the basis of these retention data, C5-C7 alkenes were identified and analyzed in the gasoline from fluid catalytic cracking. In the gasoline all 59 acyclic C5-C7 isomeric alkenes were determined at significantly different concentration levels.

  9. Three common pathways of nephrotoxicity induced by halogenated alkenes.

    PubMed

    Cristofori, Patrizia; Sauer, Aisha V; Trevisan, Andrea

    2015-02-01

    Glutathione-dependent bioactivation is a common pathway in nephrotoxicity caused by haloalkanes and haloalkenes. Glutathione conjugation forms the link between halogenated hydrocarbons, based on the formation of an episulfonium ion (vicinal halomethanes) or a cysteine conjugate (haloalkenes). Herein, we review the metabolic pathways underlying the nephrotoxic effects of the three well-known haloalkenes trichloroethylene, tetrachloroethylene, and hexachloro-1:3-butadiene to emphasize the role of cysteine-conjugate β-lyase and the oxidative metabolism in renal toxicity. Activation by cysteine-conjugate β-lyase is the best-characterized mechanism causing toxicity due to haloalkene treatment in experimental models. However, the severity of toxicity differs considerably, with S-(1,2,2-trichlorovinyl)-L-cysteine being more toxic than S-(1,2-dichlorovinyl)-L-cysteine, which is in turn more toxic than S-(1,2,3,4,4-pentachloro-1:3-butadienyl)-L-cysteine. Moreover, two oxidative pathways involving cysteine S-conjugates (mediated by flavin-containing monooxigenase 3) and N-acetyl-L-cysteine conjugates (mediated by cytochrome P-450 3A) form derived sulfoxides, which represent alternative metabolites with toxic effects. In vitro and in vivo studies showed that sulfoxide metabolites are more toxic than cysteine-conjugate derivates. The cytochrome P-450 3A family, on the other hand, is sex specific, and its expression has only been reported in adult male rats and rabbits. In summary, haloalkenes are highly nephrotoxic in vivo and in vitro and their toxicity mechanisms are well documented experimentally. However, little information is available on their toxicity in humans, except for the carcinogenic effects established for high exposure levels of trichloroethylene and tetrachloroethylene.

  10. Catalytic Alkene Carboaminations Enabled by Oxidative Proton-Coupled Electron Transfer

    PubMed Central

    Choi, Gilbert J.; Knowles, Robert R.

    2015-01-01

    Here we describe a dual catalyst system comprised of an iridium photocatalyst and weak phosphate base that is capable of both selectively homolyzing the N–H bonds of N-arylamides (bond dissociation free energies ~ 100 kcal/mol) via concerted proton-coupled electron transfer (PCET) and mediating efficient carboamination reactions of the resulting amidyl radicals. This manner of PCET activation, which finds its basis in numerous biological redox processes, enables the formal homolysis of a stronger amide N–H bond in the presence of weaker allylic C–H bonds, a selectivity that is uncommon in conventional molecular H atom acceptors. Moreover, this transformation affords access to a broad range of structurally complex heterocycles from simple amide starting materials. The design, synthetic scope, and mechanistic evaluation of the PCET process are described. PMID:26166022

  11. Nickel and cobalt-catalyzed coupling of alkyl halides with alkenes via heck reactions and radical conjugate addition.

    PubMed

    Qian, Qun; Zang, Zhenhua; Chen, Yang; Tong, Weiqi; Gong, Hegui

    2013-05-01

    Cross-coupling of alkyl halides with alkenes leading to Heck-type and addition products is summarized. The development of Heck reaction with aliphatic halides although has made significant progress in the past decade and particularly recently, it was much less explored in comparison with the aryl halides. The use of Ni- and Co-catalyzed protocols allowed efficient Heck coupling of activated and unactivated alkenes with 1°, 2° and 3° alkyl halides. In addition, radical conjugate addition to activated alkenes has become a well-established method that has led to efficient construction of many natural products. The utilization of Ni- and Co-catalyzed strategies would avoid toxic tin reagents, and therefore worth exploring. The recent development of Ni- and Co-catalyzed addition of alkyl halides to alkenes displays much improved reactivity and functional group tolerance. In this mini-review, we also attempt to overview the mechanisms that are proposed in the reactions, aiming at providing insight into the nickel and cobalt-catalyzed coupling of alkyl halides with alkenes.

  12. Biocatalytic self-assembly of supramolecular charge-transfer nanostructures based on n-type semiconductor-appended peptides.

    PubMed

    Nalluri, Siva Krishna Mohan; Berdugo, Cristina; Javid, Nadeem; Frederix, Pim W J M; Ulijn, Rein V

    2014-06-01

    The reversible in situ formation of a self-assembly building block (naphthalenediimide (NDI)-dipeptide conjugate) by enzymatic condensation of NDI-functionalized tyrosine (NDI-Y) and phenylalanine-amide (F-NH2) to form NDI-YF-NH2 is described. This coupled biocatalytic condensation/assembly approach is thermodynamically driven and gives rise to nanostructures with optimized supramolecular interactions as evidenced by substantial aggregation induced emission upon assembly. Furthermore, in the presence of di-hydroxy/alkoxy naphthalene donors, efficient charge-transfer complexes are produced. The dynamic formation of NDI-YF-NH2 and electronic and H-bonding interactions are analyzed and characterized by different methods. Microscopy (TEM and AFM) and rheology are used to characterize the formed nanostructures. Dynamic nanostructures, whose formation and function are driven by free-energy minimization, are inherently self-healing and provide opportunities for the development of aqueous adaptive nanotechnology. PMID:24788665

  13. Biocatalytic polymer thin films: optimization of the multilayered architecture towards in situ synthesis of anti-proliferative drugs

    NASA Astrophysics Data System (ADS)

    Andreasen, Sidsel Ø.; Fejerskov, Betina; Zelikin, Alexander N.

    2014-03-01

    We report on the assembly of multi-layered polyelectrolyte thin films containing an immobilized enzyme to perform conversion of externally administered prodrugs and achieve delivery of the resulting therapeutics to adhering cells. Towards this goal, multi-layered coatings were assembled using poly(sodium styrene sulfonate) and poly(allylamine hydrochloride). Activity of the incorporated enzyme was quantified as a function of the assembly conditions, position of the enzyme within the multi-layered architecture, concentration of the enzyme in the adsorption solution, and concentration of the administered prodrug. Biocatalytic coatings exhibited sustained levels of enzymatic activity over at least one week of incubation in physiological buffers without signs of loss of activity of the enzyme. Developed enzyme-containing polymer films afforded zero-order release of the in situ synthesized cargo with kinetics of synthesis (nM per hour) covering at least 3 orders of magnitude. Internalization of the synthesized product by adhering cells was visualized using a fluorogenic enzyme substrate. Therapeutic utility of biocatalytic coatings was demonstrated using a myoblast cell line and a prodrug for the anti-proliferative agent, 5-fluorouridine. Taken together, this work presents a novel approach to delivery of small molecule drugs using multi-layered polymer thin films with utility in surface-mediated drug delivery, assembly of therapeutic implantable devices, and tissue engineering.We report on the assembly of multi-layered polyelectrolyte thin films containing an immobilized enzyme to perform conversion of externally administered prodrugs and achieve delivery of the resulting therapeutics to adhering cells. Towards this goal, multi-layered coatings were assembled using poly(sodium styrene sulfonate) and poly(allylamine hydrochloride). Activity of the incorporated enzyme was quantified as a function of the assembly conditions, position of the enzyme within the multi

  14. Elucidation of the regio- and chemoselectivity of enzymatic allylic oxidations with Pleurotus sapidus – conversion of selected spirocyclic terpenoids and computational analysis

    PubMed Central

    Weidmann, Verena; Schaffrath, Mathias; Zorn, Holger

    2013-01-01

    Summary Allylic oxidations of olefins to enones allow the efficient synthesis of value-added products from simple olefinic precursors like terpenes or terpenoids. Biocatalytic variants have a large potential for industrial applications, particularly in the pharmaceutical and food industry. Herein we report efficient biocatalytic allylic oxidations of spirocyclic terpenoids by a lyophilisate of the edible fungus Pleurotus sapidus. This ‘’mushroom catalysis’’ is operationally simple and allows the conversion of various unsaturated spirocyclic terpenoids. A number of new spirocyclic enones have thus been obtained with good regio- and chemoselectivity and chiral separation protocols for enantiomeric mixtures have been developed. The oxidations follow a radical mechanism and the regioselectivity of the reaction is mainly determined by bond-dissociation energies of the available allylic CH-bonds and steric accessibility of the oxidation site. PMID:24204436

  15. Sesquiterpene, alkene, and alkane hydrocarbons in virgin olive oils of different varieties and geographical origins.

    PubMed

    Bortolomeazzi, R; Berno, P; Pizzale, L; Conte, L S

    2001-07-01

    The hydrocarbon fraction of 30 virgin olive oils was analyzed, focusing in particular on the sesquiterpenes. The oil samples were of different geographical origins and obtained from different olive varieties. The hydrocarbon fraction was isolated by silica gel column chromatography of the unsaponifiable fraction of the oils. The sesquiterpene hydrocarbons were then fractionated, on the basis of their degree of unsaturation, by AgNO3 TLC and silica gel AgNO3 column chromatography. The composition of the sesquiterpenes was more complex than previously reported. Among the 31 sesquiterpenes detected, 24 have been tentatively identified, by comparison of the linear retention indices on two capillary columns of different polarities and mass spectra with those reported in the literature. The total concentration of the sesquiterpenes in the oils analyzed ranged from about 2 to 37 ppm. Among the sesquiterpenes the more abundant were alpha-farnesene, alpha-copaene, eremophyllene, and alpha-muurolene. The alkenes present in the hydrocarbon fraction were isolated by TLC AgNO3 and characterized by GC-MS of their dimethyl disulfide derivatives. The series of n-Delta9-alkenes from C22 to C27, 8-heptadecene, and 6,10-dimethyl-1-undecene were detected. Among the n-alkanes, those with an odd number of carbon atoms predominated in all of the analyzed oils, the most common being C23, C25, C27, and C29. The concentration of the n-alkenes ranged from about 0.5 to 2 ppm, whereas for the n-alkanes the range was from 30 to 177 ppm.

  16. Cross-metathesis reaction of α- and β-vinyl C-glycosides with alkenes.

    PubMed

    Šnajdr, Ivan; Parkan, Kamil; Hessler, Filip; Kotora, Martin

    2015-01-01

    Cross-metathesis of α- and β-vinyl C-deoxyribosides and α-vinyl C-galactoside with various terminal alkenes under different conditions was studied. The cross-metathesis of the former proceeded with good yields of the corresponding products in ClCH2CH2Cl the latter required the presence of CuI in CH2Cl2 to achieve good yields of the products. A simple method for the preparation of α- and β-vinyl C-deoxyribosides was also developed. In addition, feasibility of deprotection and further transformations were briefly explored. PMID:26425194

  17. Regioselective and Stereospecific Copper-Catalyzed Deoxygenation of Epoxides to Alkenes.

    PubMed

    Yu, Jingxun; Zhou, Yu; Lin, Zhenyang; Tong, Rongbiao

    2016-09-16

    Two copper salts (Cu(CF3CO2)2 and IMesCuCl) were identified as earth-abundant, inexpensive, but effective metal catalysts together with diazo malonate for chemo-/regioselective and stereospecific deoxygenation of various epoxides with tolerance of common functional groups (alkene, ketone, ester, p-methoxybenzyl, benzyl, tert-butyldimethylsilyl, and triisopropylsilyl). In particular, the unprecedented regioselectivity allowed for the first time monodeoxygenation of diepoxides to alkenyl epoxides. Density functional theory mechanistic studies showed that the deoxygenation occurred by collapsing the free ylide, unfavoring the possible intuitive pathway via cycloreversion of possible oxetane. PMID:27596225

  18. Cross-Coupling Synthesis of Methylallyl Alkenes: Scope Extension and Mechanistic Study.

    PubMed

    Tabélé, Clémence; Curti, Christophe; Kabri, Youssef; Primas, Nicolas; Vanelle, Patrice

    2015-12-21

    Cross-coupling reactions between 2-methyl-2-propen-1-ol and various boronic acids are used to obtain aromatic-(2-methylallyl) derivatives. However, deboronation or isomerization side reactions may occur for several boronic acids. We describe herein the synthesis of original alkenes with good yields under mild reaction conditions that decrease these side reactions. The scope of this environmentally benign reaction is thereby extended to a wide variety of boronic acids. A mechanistic study was conducted and suggested a plausible catalytic cycle mechanism, pointing to the importance of the Lewis acidity of the boronic acid used.

  19. α-Diazo-β-ketonitriles: uniquely reactive substrates for arene and alkene cyclopropanation.

    PubMed

    Nani, Roger R; Reisman, Sarah E

    2013-05-15

    An investigation of the intramolecular cyclopropanation reactions of α-diazo-β-ketonitriles is reported. These studies reveal that α-diazo-β-ketonitriles exhibit unique reactivity in their ability to undergo arene cyclopropanation reactions; other similar acceptor-acceptor-substituted diazo substrates instead produce mixtures of C-H insertion and dimerization products. α-Diazo-β-ketonitriles also undergo highly efficient intramolecular cyclopropanation of tri- and tetrasubstituted alkenes. In addition, the α-cyano-α-ketocyclopropane products are demonstrated to serve as substrates for SN2, SN2', and aldehyde cycloaddition reactions.

  20. Enantioselective CuH-catalyzed anti-Markovnikov hydroamination of 1,1-disubstituted alkenes.

    PubMed

    Zhu, Shaolin; Buchwald, Stephen L

    2014-11-12

    Enantioselective synthesis of β-chiral amines has been achieved via copper-catalyzed hydroamination of 1,1-disubstituted alkenes with hydroxylamine esters in the presence of a hydrosilane. This mild process affords a range of structurally diverse β-chiral amines, including β-deuterated amines, in excellent yields with high enantioselectivities. Furthermore, catalyst loading as low as 0.4 mol% could be employed to deliver product in undiminished yield and selectivity, demonstrating the practicality of this method for large-scale synthesis. PMID:25339089

  1. Efficient copper-catalyzed direct intramolecular aminotrifluoromethylation of unactivated alkenes with diverse nitrogen-based nucleophiles.

    PubMed

    Lin, Jin-Shun; Xiong, Ya-Ping; Ma, Can-Liang; Zhao, Li-Jiao; Tan, Bin; Liu, Xin-Yuan

    2014-01-27

    A mild, convenient, and step-economical intramolecular aminotrifluoromethylation of unactivated alkenes with a variety of electronically distinct, nitrogen-based nucleophiles in the presence of a simple copper salt catalyst, in the absence of extra ligands, is described. Many different nitrogen-based nucleophiles (e.g., basic primary aliphatic and aromatic amines, sulfonamides, carbamates, and ureas) can be employed in this new aminotrifluoromethylation reaction. The aminotrifluoromethylation process allows straightforward access to diversely substituted CF3-containing pyrrolidines or indolines, in good to excellent yields, through a direct difunctionalization strategy from the respective acyclic starting materials. Mechanistic studies were conducted and a plausible mechanism was proposed. PMID:24458913

  2. Intermolecular hydroaminoalkylation of alkenes and dienes using a titanium mono(formamidinate) catalyst.

    PubMed

    Dörfler, Jaika; Preuss, Till; Brahms, Christian; Scheuer, Dennis; Doye, Sven

    2015-07-21

    An easily accessible formamidinate ligand-bearing titanium complex initially synthesized by Eisen et al. is used as catalyst for intermolecular hydroaminoalkylation reactions of unactivated, sterically demanding 1,1- and 1,2-disubstituted alkenes and styrenes with secondary amines. The corresponding reactions, which have never been achieved with titanium catalysts before, take place with excellent regioselectivity (up to 99 : 1) and in addition, corresponding reactions of 1,3-butadienes with N-methylbenzylamine are also described for the first time.

  3. Coordination and insertion of alkenes and alkynes in Au(III) complexes: nature of the intermediates from a computational perspective.

    PubMed

    Balcells, David; Eisenstein, Odile; Tilset, Mats; Nova, Ainara

    2016-04-01

    The contribution of Au(III) species to catalysis is still debated due to the limited number of characterized intermediates with this oxidation state. In particular, the coordination of alkenes and alkynes to Au(III) followed by insertion into Au(III)-X bonds has been suggested but rarely proven experimentally. Here, these reactions are explored by means of DFT and CCSD(T) calculations considering [AuX3(L)] and [AuX2(L)2](+) complexes. In these complexes, L = ethylene and acetylene have been chosen as substrates of high interest and representative of any unsaturated organic substrate, whereas X is Cl, Me or H, as found in metal salts and as model for intermediates involved in catalysis. Isoelectronic Pt(II) complexes are also considered for comparison. Ethylene coordination occurs preferentially perpendicular for all X except H, whereas for acetylene, coordination takes place in-plane for all X except Cl. These coordination isomers can represent either minima (intermediates) or saddle points (transition states) on the potential energy surface, depending on X. NBO analysis shows how this variety of structures results from the combination of electronic (M-L donation and back-donation) and steric (cis L-X repulsion) effects. With the sole exception of [AuMe2(ethylene)2](+), rotation of the unsaturated ligand and insertion into a cis Au-X bond involve low to moderate energy barriers, ΔG(‡) = 2.5 to 23.5 kcal mol(-1), and are thermodynamically feasible, ΔG = 4.3 to -47.2 kcal mol(-1). The paucity of experimental observations for such reactions should thus be caused by other factors, like the participation of the intermediates and products in competitive side reactions including the reductive elimination of XCHnCHnX (n = 1 or 2). PMID:26905649

  4. Suppression of Chloroplastic Alkenal/One Oxidoreductase Represses the Carbon Catabolic Pathway in Arabidopsis Leaves during Night.

    PubMed

    Takagi, Daisuke; Ifuku, Kentaro; Ikeda, Ken-Ichi; Inoue, Kanako Ikeda; Park, Pyoyun; Tamoi, Masahiro; Inoue, Hironori; Sakamoto, Katsuhiko; Saito, Ryota; Miyake, Chikahiro

    2016-04-01

    Lipid-derived reactive carbonyl species (RCS) possess electrophilic moieties and cause oxidative stress by reacting with cellular components. Arabidopsis (Arabidopsis thaliana) has a chloroplast-localized alkenal/one oxidoreductase (AtAOR) for the detoxification of lipid-derived RCS, especially α,β-unsaturated carbonyls. In this study, we aimed to evaluate the physiological importance of AtAOR and analyzed AtAOR (aor) mutants, including a transfer DNA knockout, aor (T-DNA), and RNA interference knockdown, aor (RNAi), lines. We found that both aor mutants showed smaller plant sizes than wild-type plants when they were grown under day/night cycle conditions. To elucidate the cause of the aor mutant phenotype, we analyzed the photosynthetic rate and the respiration rate by gas-exchange analysis. Subsequently, we found that both wild-type and aor (RNAi) plants showed similar CO2 assimilation rates; however, the respiration rate was lower in aor (RNAi) than in wild-type plants. Furthermore, we revealed that phosphoenolpyruvate carboxylase activity decreased and starch degradation during the night was suppressed in aor (RNAi). In contrast, the phenotype of aor (RNAi) was rescued when aor (RNAi) plants were grown under constant light conditions. These results indicate that the smaller plant sizes observed in aor mutants grown under day/night cycle conditions were attributable to the decrease in carbon utilization during the night. Here, we propose that the detoxification of lipid-derived RCS by AtAOR in chloroplasts contributes to the protection of dark respiration and supports plant growth during the night.

  5. Suppression of Chloroplastic Alkenal/One Oxidoreductase Represses the Carbon Catabolic Pathway in Arabidopsis Leaves during Night1[OPEN

    PubMed Central

    Ifuku, Kentaro; Ikeda, Ken-ichi; Inoue, Kanako Ikeda; Park, Pyoyun; Tamoi, Masahiro; Inoue, Hironori; Sakamoto, Katsuhiko; Saito, Ryota

    2016-01-01

    Lipid-derived reactive carbonyl species (RCS) possess electrophilic moieties and cause oxidative stress by reacting with cellular components. Arabidopsis (Arabidopsis thaliana) has a chloroplast-localized alkenal/one oxidoreductase (AtAOR) for the detoxification of lipid-derived RCS, especially α,β-unsaturated carbonyls. In this study, we aimed to evaluate the physiological importance of AtAOR and analyzed AtAOR (aor) mutants, including a transfer DNA knockout, aor (T-DNA), and RNA interference knockdown, aor (RNAi), lines. We found that both aor mutants showed smaller plant sizes than wild-type plants when they were grown under day/night cycle conditions. To elucidate the cause of the aor mutant phenotype, we analyzed the photosynthetic rate and the respiration rate by gas-exchange analysis. Subsequently, we found that both wild-type and aor (RNAi) plants showed similar CO2 assimilation rates; however, the respiration rate was lower in aor (RNAi) than in wild-type plants. Furthermore, we revealed that phosphoenolpyruvate carboxylase activity decreased and starch degradation during the night was suppressed in aor (RNAi). In contrast, the phenotype of aor (RNAi) was rescued when aor (RNAi) plants were grown under constant light conditions. These results indicate that the smaller plant sizes observed in aor mutants grown under day/night cycle conditions were attributable to the decrease in carbon utilization during the night. Here, we propose that the detoxification of lipid-derived RCS by AtAOR in chloroplasts contributes to the protection of dark respiration and supports plant growth during the night. PMID:26884484

  6. The chemistry of simple alkene molecules on Si(100)c(4 × 2): The mechanism of cycloaddition and their selectivities

    NASA Astrophysics Data System (ADS)

    Akagi, Kazuto; Yoshinobu, Jun

    2016-10-01

    The chemistry of simple alkene molecules on the Si(100) surface is reviewed with the newly-produced visual presentation by theoretical calculations. The early pioneering studies by the Kyoto Group and Pittsburgh group reported the di-σ bond formation and the precursor-mediated chemisorption for acetylene and ethylene on Si(100), respectively. Thereafter, these studies have been stimulating various studies of organic molecules on Si surfaces. Our recent studies have observed the precursor states for alkene chemisorption and elucidated the microscopic mechanisms of the di-σ bond formation (cycloaddition) with the help of theoretical calculations; the site-, stereo- and regio-selective chemisorption of simple alkene molecules on Si(100)c(4 × 2) has been established.

  7. Enantioselective Synthesis of Spirobarbiturate-Cyclohexenes through Phosphine-Catalyzed Asymmetric [4 + 2] Annulation of Barbiturate-Derived Alkenes with Allenoates.

    PubMed

    Liu, Honglei; Liu, Yang; Yuan, Chunhao; Wang, Guo-Peng; Zhu, Shou-Fei; Wu, Yang; Wang, Bo; Sun, Zhanhu; Xiao, Yumei; Zhou, Qi-Lin; Guo, Hongchao

    2016-03-18

    An enantioselective synthesis of pharmaceutically important spirobarbiturates has been achieved via spirocyclic chiral phosphine-catalyzed asymmetric [4 + 2] annulation of barbiturate-derived alkenes with allenoates. With the use of this tool, various spirobarbiturate-cyclohexenes are obtained in good to excellent yields with excellent diastereo- and enantioselectivities. A wide range of α-substituted allenoates and barbiturate-derived alkenes were tolerated.

  8. Sources of C₂-C₄ alkenes, the most important ozone nonmethane hydrocarbon precursors in the Pearl River Delta region.

    PubMed

    Zhang, Yanli; Wang, Xinming; Zhang, Zhou; Lü, Sujun; Huang, Zhonghui; Li, Longfeng

    2015-01-01

    Surface ozone is becoming an increasing concern in China's megacities such as the urban centers located in the highly industrialized and densely populated Pearl River Delta (PRD) region, where previous studies suggested that ozone production is sensitive to VOC emissions with alkenes being important precursors. However, little was known about sources of alkenes. Here we present our monitoring of ambient volatile organic compounds at four representative urban, suburban and rural sites in the PRD region during November-December 2009, which experienced frequent ozone episodes. C2-C4 alkenes, whose total mixing ratios were 11-20% of non-methane hydrocarbons (NMHCs) quantified, accounted for 38-64% of ozone formation potentials (OFPs) and 30-50% of the total hydroxyl radical (OH) reactivity by NMHCs. Ethylene was the most abundant alkene, accounting for 8-15% in total mixing ratios of NMHCs and contributed 25-46% of OFPs. Correlations between C2-C4 alkenes and typical source tracers suggested that ethylene might be largely related to vehicle exhausts and industry activities, while propene and butenes were much more LPG-related. Positive Matrix Factorization (PMF) confirmed that vehicle exhaust and liquefied petroleum gas (LPG) were two major sources that altogether accounted for 52-62%, 58-77%, 73-83%, 68-79% and 73-84% for ethylene, propene, 1-butene, trans-2-butene and cis-2-butene, respectively. Vehicle exhausts alone contributed 32-49% ethylene and 35-41% propene. Industry activities contributed 13-23% ethylene and 7-20% propene. LPG instead contributed the most to butenes (38-65%) and substantially to propene (23-36%). Extensive tests confirmed high fractions of propene and butenes in LPG then used in Guangzhou and in LPG combustion plumes; therefore, limiting alkene contents in LPG would benefit regional ozone control.

  9. Products and mechanism of secondary organic aerosol formation from reactions of linear alkenes with NO3 radicals.

    PubMed

    Gong, Huiming; Matsunaga, Aiko; Ziemann, Paul J

    2005-05-19

    Secondary organic aerosol (SOA) formation from reactions of linear alkenes with NO(3) radicals was investigated in an environmental chamber using a thermal desorption particle beam mass spectrometer for particle analysis. A general chemical mechanism was developed to explain the formation of the observed SOA products. The major first-generation SOA products were hydroxynitrates, carbonylnitrates, nitrooxy peroxynitrates, dihydroxynitrates, and dihydroxy peroxynitrates. The major second-generation SOA products were hydroxy and oxo dinitrooxytetrahydrofurans, which have not been observed previously. The latter compounds were formed by a series of reactions in which delta-hydroxycarbonyls isomerize to cyclic hemiacetals, which then dehydrate to form substituted dihydrofurans (unsaturated compounds) that rapidly react with NO(3) radicals to form very low volatility products. For the approximately 1 ppmv alkene concentrations used here, aerosol formed only for alkenes C(7) or larger. SOA formed from C(7)-C(9) alkenes consisted only of second-generation products, whereas for larger alkenes first-generation products were also present and contributions increased with increasing carbon number apparently due to the formation of lower volatility products. The estimated mass fractions of first- and second-generation products were approximately 50:50, 30:70, 10:90, and 0:100, for 1-tetradecene, 1-dodecene, 1-decene, and 1-octene SOA, respectively. This study shows that delta-hydroxycarbonyls play a key role in the formation of SOA in alkene-NO(3) reactions and are likely to be important in other systems because delta-hydroxycarbonyls can also be formed from reactions of OH radicals and O(3) with hydrocarbons.

  10. Photocatalytic oxidation by uranyl

    SciTech Connect

    McCleskey, T.M.; Tumas, W.; Burns, C.J.

    1995-12-01

    The excited state of uranyl (UO{sub 2}{sup 2+}*) is a potent oxidant (E{sup 0}(UO{sub 2}{sup 2+}*/UO{sub 2}{sup +}) {approx} 2.5 V) which can be quenched by either electron transfer (ET) or H atom abstraction. We have investigated both types of quenching with a variety of organic substrates in water and acetone/water media. Excited-state reactions with alkenes proceed by ET to form cation radicals, while reactions with tertiary alkanes follow an H-atom abstraction pathway. In aqueous media uranyl photocatalytically decomposes tert-butyl peroxide in a manner analogous to Fenton-type chemistry.

  11. UV light-mediated difunctionalization of alkenes through aroyl radical addition/1,4-/1,2-aryl shift cascade reactions.

    PubMed

    Zheng, Lewei; Huang, Hongli; Yang, Chao; Xia, Wujiong

    2015-02-20

    UV light-mediated difunctionalization of alkenes through an aroyl radical addition/1,4-/1,2-aryl shift has been described. The resulted aroyl radical from a photocleavage reaction added to acrylamide compounds followed by cyclization led to the formation of oxindoles, whereas the addition to cinnamic amides aroused a unique 1,4-aryl shift reaction. Furthermore, the difunctionalization of alkenes of prop-2-en-1-ols was also achieved through aroyl radical addition and a sequential 1,2-aryl shift cascade reaction.

  12. Palladium-catalyzed hydroaminocarbonylation of alkenes with amines: a strategy to overcome the basicity barrier imparted by aliphatic amines.

    PubMed

    Zhang, Guoying; Gao, Bao; Huang, Hanmin

    2015-06-22

    A novel and efficient palladium-catalyzed hydroaminocarbonylation of alkenes with aminals has been developed under mild reaction conditions, and allows the synthesis of a wide range of N-alkyl linear amides in good yields with high regioselectivity. On the basis of this method, a cooperative catalytic system operating by the synergistic combination of palladium, paraformaldehyde, and acid was established for promoting the hydroaminocarbonylation of alkenes with both aromatic and aliphatic amines, which do not react well under conventional palladium-catalyzed hydroaminocarbonylation.

  13. Hybrid membrane with TiO2 based bio-catalytic nanoparticle suspension system for the degradation of bisphenol-A.

    PubMed

    Hou, Jingwei; Dong, Guangxi; Luu, Belinda; Sengpiel, Robert G; Ye, Yun; Wessling, Matthias; Chen, Vicki

    2014-10-01

    The removal of micropollutant in wastewater treatment has become a key environmental challenge for many industrialized countries. One approach is to use enzymes such as laccase for the degradation of micropollutants such as bisphenol-A. In this work, laccase was covalently immobilized on APTES modified TiO2 nanoparticles, and the effects of particle modification on the bio-catalytic performance were examined and optimized. These bio-catalytic particles were then suspended in a hybrid membrane reactor for BPA removal with good BPA degradation efficiency observed. Substantial improvement in laccase stability was achieved in the hybrid system compared with free laccase under simulated harsh industrial wastewater treatment conditions (such as a wide range of pH and presence of inhibitors). Kinetic study provided insight of the effect of immobilization on the bio-degradation reaction. PMID:25084046

  14. Platinum-catalyzed intramolecular hydrohydrazination: evidence for alkene insertion into a Pt-N bond.

    PubMed

    Hoover, Jessica M; Dipasquale, Antonio; Mayer, James M; Michael, Forrest E

    2010-04-14

    Dicationic (bpy)Pt(II) complexes were found to catalyze the intramolecular hydrohydrazination of alkenes. Reaction optimization revealed Pt(bpy)Cl(2) (10 mol %) and AgOTf (20 mol %) in DMF-d(7) to be an effective catalyst system for the conversion of substituted hydrazides to five- and six-membered N-amino lactams (N-amino = N-acetamido at 120 degrees C, N-phthalimido at 80 degrees C, (-)OTf = trifluoromethanesulfonate). Of the four possible regioisomeric products, only the product of 5-exo cyclization at the proximal nitrogen is formed, without reaction at the distal nitrogen or 6-endo cyclization. The resting states were found to be a 2:1 Pt-amidate complex (25, for N-acetamido) of the deprotonated hydrazide and a Pt-alkyl complex of the cyclized pyrrolidinone (20 for N-phthalimido). Both complexes are catalytically competent. Catalysis using 25 as the precatalyst shows no rate dependence on added acid (HOTf) or base (2,6-lutidine). The available mechanistic data are all consistent with a mechanism involving N-H activation of the hydrazide, followed by insertion of the alkene into the Pt-N bond, and finally protonation of the resulting cyclized alkyl complex by hydrazide to release the hydrohydrazination product and regenerate the active Pt-amidate catalyst. PMID:20334376

  15. Photochemical electron transfer mediated addition of naphthylamine derivatives to electron-deficient alkenes.

    PubMed

    Jahjah, Rabih; Gassama, Abdoulaye; Dumur, Frédéric; Marinković, Siniša; Richert, Sabine; Landgraf, Stephan; Lebrun, Aurélien; Cadiou, Cyril; Sellès, Patrice; Hoffmann, Norbert

    2011-09-01

    Using photochemical electron transfer, N,N-dimethylnaphthylamine derivatives are added to α,β-unsaturated carboxylates. The addition takes place exclusively in the α-position of electron-deficient alkenes and mainly in the 4-position of N,N-dimethylnaphthalen-1-amine. A minor regioisomer results from the addition in the 5-position of this naphthylamine. A physicochemical study reveals that the fluorescence quenching of N,N-dimethylnaphthalen-1-amine is diffusion-controlled and that the back electron transfer is highly efficient. Therefore no transformation is observed at lower concentrations. To overcome this limitation and to induce an efficient transformation, minor amounts of water or another proton donor as well as an excess of the naphthylamine derivative are necessary. A mechanism involving a contact radical ion pair is discussed. Isotopic labeling experiments reveal that no hydrogen is directly transferred between the substrates. The hydrogen transfer to the furanone moiety observed in the overall reaction therefore results from an exchange with the reaction medium. An electrophilic oxoallyl radical generated from the furanone reacts with the naphthylamine used in excess. Concerning some mechanistic details, the reaction is compared with radical and electrophilic aromatic substitutions. The transformation was carried out with a variety of electron-deficient alkenes. Sterically hindered furanone derivatives are less reactive under standard conditions. In a first experiment, such a compound was transformed using heterogeneous electron transfer photocatalysis with TiO(2).

  16. SmoXYB1C1Z of Mycobacterium sp. Strain NBB4: a Soluble Methane Monooxygenase (sMMO)-Like Enzyme, Active on C2 to C4 Alkanes and Alkenes

    PubMed Central

    Martin, Kiri E.; Ozsvar, Jazmin

    2014-01-01

    Monooxygenase (MO) enzymes initiate the aerobic oxidation of alkanes and alkenes in bacteria. A cluster of MO genes (smoXYB1C1Z) of thus-far-unknown function was found previously in the genomes of two Mycobacterium strains (NBB3 and NBB4) which grow on hydrocarbons. The predicted Smo enzymes have only moderate amino acid identity (30 to 60%) to their closest homologs, the soluble methane and butane MOs (sMMO and sBMO), and the smo gene cluster has a different organization from those of sMMO and sBMO. The smoXYB1C1Z genes of NBB4 were cloned into pMycoFos to make pSmo, which was transformed into Mycobacterium smegmatis mc2-155. Cells of mc2-155(pSmo) metabolized C2 to C4 alkanes, alkenes, and chlorinated hydrocarbons. The activities of mc2-155(pSmo) cells were 0.94, 0.57, 0.12, and 0.04 nmol/min/mg of protein with ethene, ethane, propane, and butane as substrates, respectively. The mc2-155(pSmo) cells made epoxides from ethene, propene, and 1-butene, confirming that Smo was an oxygenase. Epoxides were not produced from larger alkenes (1-octene and styrene). Vinyl chloride and 1,2-dichloroethane were biodegraded by cells expressing Smo, with production of inorganic chloride. This study shows that Smo is a functional oxygenase which is active against small hydrocarbons. M. smegmatis mc2-155(pSmo) provides a new model for studying sMMO-like monooxygenases. PMID:25015887

  17. SmoXYB1C1Z of Mycobacterium sp. strain NBB4: a soluble methane monooxygenase (sMMO)-like enzyme, active on C2 to C4 alkanes and alkenes.

    PubMed

    Martin, Kiri E; Ozsvar, Jazmin; Coleman, Nicholas V

    2014-09-01

    Monooxygenase (MO) enzymes initiate the aerobic oxidation of alkanes and alkenes in bacteria. A cluster of MO genes (smoXYB1C1Z) of thus-far-unknown function was found previously in the genomes of two Mycobacterium strains (NBB3 and NBB4) which grow on hydrocarbons. The predicted Smo enzymes have only moderate amino acid identity (30 to 60%) to their closest homologs, the soluble methane and butane MOs (sMMO and sBMO), and the smo gene cluster has a different organization from those of sMMO and sBMO. The smoXYB1C1Z genes of NBB4 were cloned into pMycoFos to make pSmo, which was transformed into Mycobacterium smegmatis mc(2)-155. Cells of mc(2)-155(pSmo) metabolized C2 to C4 alkanes, alkenes, and chlorinated hydrocarbons. The activities of mc(2)-155(pSmo) cells were 0.94, 0.57, 0.12, and 0.04 nmol/min/mg of protein with ethene, ethane, propane, and butane as substrates, respectively. The mc(2)-155(pSmo) cells made epoxides from ethene, propene, and 1-butene, confirming that Smo was an oxygenase. Epoxides were not produced from larger alkenes (1-octene and styrene). Vinyl chloride and 1,2-dichloroethane were biodegraded by cells expressing Smo, with production of inorganic chloride. This study shows that Smo is a functional oxygenase which is active against small hydrocarbons. M. smegmatis mc(2)-155(pSmo) provides a new model for studying sMMO-like monooxygenases. PMID:25015887

  18. Stereoselective introduction of two chiral centers by a single diketoreductase: an efficient biocatalytic route for the synthesis of statin side chains.

    PubMed

    Wu, Xuri; Wang, Lili; Wang, Shuzhen; Chen, Yijun

    2010-06-01

    Statins, including atorvastatin (Lipitor), are the top-selling drugs in the world. The biocatalytic production of chiral side chains of statin drugs is of great interest to academia and industry. Stereoselective double reduction of a beta,delta-diketo ester catalyzed by a diketoreductase offers a simple and efficient route for the preparation of statin side chains. Comparison of different cofactor regeneration systems resulted in an easy and cost-effective process for this enzymatic reduction.

  19. Photocatalytic synthesis of dihydrobenzofurans by oxidative [3+2] cycloaddition of phenols.

    PubMed

    Blum, Travis R; Zhu, Ye; Nordeen, Sarah A; Yoon, Tehshik P

    2014-10-01

    We report a protocol for oxidative [3+2] cycloadditions of phenols and alkenes applicable to the modular synthesis of a large family of dihydrobenzofuran natural products. Visible-light-activated transition metal photocatalysis enables the use of ammonium persulfate as an easily handled, benign terminal oxidant. The broad range of organic substrates that are readily oxidized by photoredox catalysis suggests that this strategy may be applicable to a variety of useful oxidative transformations. PMID:25155300

  20. Application of two methods of calculation of solvation descriptor L to estimate C5 -C7 alkenes retention.

    PubMed

    Jirkal, Štěpán; Ševčík, Jiří G K

    2015-07-01

    The solvation descriptor L for 59 isomers of all C5 -C7 alkenes was calculated using two methods based on additive contributions of particular fragments in the molecule by the method of Havelec and Ševčík and the method of Platts and Butina. These descriptors were used to estimate the gas chromatography retention of alkenes on squalane and polydimethylsiloxane stationary phases. The retention was described better by the Platts-Butina method. Modification of the Havelec-Ševčík method by omitting the contribution for interaction of the cis isomers led to a substantial improvement in the estimation ability of the model. The modified Havelec-Ševčík method was found to be preferable for estimation of the descriptor L compared to the Platts-Butina method. A more comprehensive description of the retention of alkenes was achieved by inclusion of an additional descriptor E. This model with the descriptors L and E yielded better estimation for alkenes compared to the model with a single descriptor.

  1. Selective partial hydrogenation of alkynes to (Z)-alkenes with ionic liquid-doped nickel nanocatalysts at near ambient conditions.

    PubMed

    Konnerth, Hannelore; Prechtl, Martin H G

    2016-07-12

    A selective hydrogenation method for forming (Z)-alkenes from alkynes has been developed using a catalyst system of cheap Ni-NPs in a nitrile functionalised imidazolium based ionic liquid (IL) operating under very mild reaction conditions of 30-50 °C and 1-4 bar H2 pressure.

  2. Magnetic Fe@g-C3N4: A Photoactive Catalyst for the Hydrogenation of Alkenes and Alkynes

    EPA Science Inventory

    A photoactive catalyst, Fe@g-C3N4, has been developed for the hydrogenation of alkenes and alkynes using hydrazine hydrate as a source of hydrogen. The magnetically separable Fe@g-C3N4 eliminates the use of high pressure hydrogenation and the reaction can be accomplished using vi...

  3. Nickel-catalyzed three-component domino reactions of aryl Grignard reagents, alkynes, and aryl halides producing tetrasubstituted alkenes.

    PubMed

    Xue, Fei; Zhao, Jin; Hor, T S Andy; Hayashi, Tamio

    2015-03-11

    Three-component reaction of aryl Grignard reagents, alkynes, and aryl halides in the presence of 1 mol % of NiCl2 proceeded sequentially through carbomagnesiation of the alkyne followed by cross-coupling of the resulting alkenyl Grignard reagent with aryl halide to give tetrasubstituted alkenes in high yields. PMID:25714497

  4. Regioselective Hydration of an Alkene and Analysis of the Alcohol Product by Remote Access NMR: A Classroom Demonstration

    ERIC Educational Resources Information Center

    Smith, Maureen E.; Johnson, Sara L.; Masterson, Douglas S.

    2013-01-01

    A two-part demonstration was conducted in our first-semester organic chemistry course designed to introduce students to the formation of alcohols, regioselective reactions, and analysis of organic products by NMR analysis. This demonstration utilized the oxymercuration-demercuration sequence to prepare an alcohol from an alkene in a Markovnikov…

  5. FORMATION OF BETA-HYDROXYCARBONYLS FROM THE OH RADICAL-INITIATED REACTIONS OF SELECTED ALKENES (R825252)

    EPA Science Inventory

    -Hydroxycarbonyls can be formed from the gas-phase
    reactions of alkenes with the OH radical, both in the presence
    and in the absence of NO. To date, because of analytical
    difficulties, few data have been r...

  6. A general synthesis of fluoroalkylated alkenes by palladium-catalyzed Heck-type reaction of fluoroalkyl bromides.

    PubMed

    Feng, Zhang; Min, Qiao-Qiao; Zhao, Hai-Yang; Gu, Ji-Wei; Zhang, Xingang

    2015-01-19

    An efficient palladium-catalyzed Heck-type reaction of fluoroalkyl halides, including perfluoroalkyl bromides, trifluoromethyl iodides, and difluoroalkyl bromides, has been developed. The reaction proceeds under mild reaction conditions with high efficiency and broad substrate scope, and provides a general and straightforward access to fluoroalkylated alkenes which are of interest in life and material sciences.

  7. Direct Catalytic Synthesis of Unprotected 2-Amino-1-Phenylethanols from Alkenes by Using Iron(II) Phthalocyanine.

    PubMed

    Legnani, Luca; Morandi, Bill

    2016-02-01

    Aryl-substituted amino alcohols are privileged scaffolds in medicinal chemistry and natural products. Herein, we report that an exceptionally simple and inexpensive Fe(II) complex efficiently catalyzes the direct transformation of simple alkenes into unprotected amino alcohols in good yield and perfect regioselectivity. This new catalytic method was applied in the expedient synthesis of bioactive molecules and could be extended to aminoetherification.

  8. Selective access to trisubstituted macrocyclic E- and Z-alkenes from the ring-closing metathesis of vinylsiloxanes.

    PubMed

    Wang, Yikai; Jimenez, Miguel; Sheehan, Patrick; Zhong, Cheng; Hung, Alvin W; Tam, Chun Pong; Young, Damian W

    2013-03-15

    Macrocyclic (E)-alkenylsiloxanes, obtained from E-selective ring-closing metathesis reactions, can be converted to the corresponding (Z)-alkenyl bromides and (E)-alkenyl iodides allowing access to both E- and Z-trisubstituted macrocyclic alkenes. The reaction conditions and substrate scope of these stereoselective transformations are explored.

  9. Total synthesis of debromoflustramines B and E based on the intramolecular carbamoylketene-alkene [2 + 2] cycloaddition.

    PubMed

    Ozawa, Tsukasa; Kanematsu, Makoto; Yokoe, Hiromasa; Yoshida, Masahiro; Shishido, Kozo

    2012-10-19

    Total synthesis of debromoflustramines B and E has been accomplished by using a platinum-catalyzed addition reaction of o-aminophenylboronic acid with the allene and an intramolecular carbamoylketene-alkene [2 + 2] cycloaddition for the construction of the basic carbon framework of the target alkaloids as the key steps.

  10. UV light-mediated difunctionalization of alkenes with CF3SO2Na: synthesis of trifluoromethyl phenanthrene and anthrone derivatives.

    PubMed

    Li, Bing; Fan, Dan; Yang, Chao; Xia, Wujiong

    2016-06-21

    A metal-free and cost-effective protocol for UV light-mediated difunctionalization of alkenes with CF3SO2Na was developed. This strategy realized the direct formation of Csp(3)-CF3 and C-C bonds through a proposed tandem radical cyclization process, which produced a variety of phenanthrene and anthrone derivatives in moderate yields. PMID:27206267

  11. Efficient alkene epoxidation catalyzed by molybdenyl acetylacetonate supported on aminated UiO-66 metal−organic framework

    SciTech Connect

    Kardanpour, Reihaneh; Tangestaninejad, Shahram; Mirkhani, Valiollah; Moghadam, Majid; Mohammadpoor-Baltork, Iraj; Zadehahmadi, Farnaz

    2015-03-15

    Metal–organic frameworks (MOFs) containing Mo Schiff base complexes were prepared by post-synthesis method and applied as efficient catalysts in the epoxidation of alkenes with tert-BuOOH. In this manner, UiO-66-NH{sub 2} (UiO=University of Oslo) MOF was reacted with salicylaldehyde and thiophene-2-carbaldehyde to produce bidentate Schiff bases. Then, the Schiff base ligands were used for immobilization of molybdenyl acetylacetonate. These new catalysts were characterized by FT-IR, UV–vis spectroscopic techniques, X-ray diffraction (XRD), BET, inductively coupled plasma atomic emission spectroscopy (ICP-AES) and field emission scanning electron microscopy (FE-SEM). These catalytic systems showed excellent activity in the epoxidation of alkenes such as cyclic and linear ones with tert-butyl hydroperoxide (TBHP) in 1,2-dichloroethane, and reused several times without any appreciable loss of their activity. - Graphical abstract: Efficient alkene epoxidation with TBHP catalyzed by heterogeneous and reusable molybdenum base catalysts is reported. - Highlights: • UiO-66-NH{sub 2} was modified with salicylaldehyde and thiophene-2-carbaldehyde. • The Schiff base groups were used for immobilization of MoO{sub 2}(acac){sub 2}. • The heterogeneous catalysts were prepared. • The prepared catalysts were used for epoxidation of alkenes. • Compared to other catalyst, our catalysts were more efficient and forceful.

  12. Hydrogen peroxide-independent production of α-alkenes by OleTJE P450 fatty acid decarboxylase

    PubMed Central

    2014-01-01

    Background Cytochrome P450 OleTJE from Jeotgalicoccus sp. ATCC 8456, a new member of the CYP152 peroxygenase family, was recently found to catalyze the unusual decarboxylation of long-chain fatty acids to form α-alkenes using H2O2 as the sole electron and oxygen donor. Because aliphatic α-alkenes are important chemicals that can be used as biofuels to replace fossil fuels, or for making lubricants, polymers and detergents, studies on OleTJE fatty acid decarboxylase are significant and may lead to commercial production of biogenic α-alkenes in the future, which are renewable and more environmentally friendly than petroleum-derived equivalents. Results We report the H2O2-independent activity of OleTJE for the first time. In the presence of NADPH and O2, this P450 enzyme efficiently decarboxylates long-chain fatty acids (C12 to C20) in vitro when partnering with either the fused P450 reductase domain RhFRED from Rhodococcus sp. or the separate flavodoxin/flavodoxin reductase from Escherichia coli. In vivo, expression of OleTJE or OleTJE-RhFRED in different E. coli strains overproducing free fatty acids resulted in production of variant levels of multiple α-alkenes, with a highest total hydrocarbon titer of 97.6 mg·l-1. Conclusions The discovery of the H2O2-independent activity of OleTJE not only raises a number of fundamental questions on the monooxygenase-like mechanism of this peroxygenase, but also will direct the future metabolic engineering work toward improvement of O2/redox partner(s)/NADPH for overproduction of α-alkenes by OleTJE. PMID:24565055

  13. Product Control in Alkene Trifluoromethylation: Hydrotrifluoromethylation, Vinylic Trifluoromethylation, and Iodotrifluoromethylation using Togni Reagent

    PubMed Central

    Egami, Hiromichi; Usui, Yoshihiko; Kawamura, Shintaro; Nagashima, Sayoko; Sodeoka, Mikiko

    2015-01-01

    Hydrotrifluoromethylation, vinylic trifluoromethylation, and iodotrifluoromethylation of simple alkenes have been achieved by using Togni reagent in the absence of any transition metal catalyst. These reactions were readily controllable by selection of appropriate salts and solvents. The addition of K2CO3 afforded the hydrotrifluoromethylation product, with DMF acting not only as a solvent, but also as the hydrogen source. In contrast, the use of tetra-n-butylammonium iodide (TBAI) in 1,4-dioxane resulted in vinylic trifluoromethylation, while the use of KI afforded the iodotrifluoromethylation product. The vinylic trifluoromethylation product was obtained by treatment of the iodotrifluoromethylation product with ammonium 2-iodobenzoate, indicating that it was formed through an elimination reaction of the in-situ-generated iodotrifluoromethylation product, and the solubility of the resulting 2-iodobenzoate salt plays a key role in the product switching. A radical-clock experiment showed that these reactions proceed via radical intermediates. PMID:25960034

  14. Walphos versus Biferrocene-Based Walphos Analogues in the Asymmetric Hydrogenation of Alkenes and Ketones

    PubMed Central

    2014-01-01

    Two representative Walphos analogues with an achiral 2,2″-biferrocenediyl backbone were synthesized. These diphosphine ligands were tested in the rhodium-catalyzed asymmetric hydrogenation of several alkenes and in the ruthenium-catalyzed hydrogenation of two ketones. The results were compared with those previously obtained on using biferrocene ligands with a C2-symmetric 2,2″-biferrocenediyl backbone as well as with those obtained with Walphos ligands. The application of one newly synthesized ligand in the hydrogenation of 2-methylcinnamic acid gave (R)-2-methyl-3-phenylpropanoic acid with full conversion and with 92% ee. The same ligand was used to transform 2,4-pentanedione quantitatively and diastereoselectively into (S,S)-2,4-pentanediol with 98% ee. PMID:24795493

  15. Surfing π clouds for noncovalent interactions: arenes versus alkenes.

    PubMed

    Aliev, Abil E; Arendorf, Josephine R T; Pavlakos, Ilias; Moreno, Rafael B; Porter, Michael J; Rzepa, Henry S; Motherwell, William B

    2015-01-01

    A comparative study of molecular balances by NMR spectroscopy indicates that noncovalent functional-group interactions with an arene dominate over those with an alkene, and that a π-facial intramolecular hydrogen bond from a hydroxy group to an arene is favored by approximately 1.2 kJ mol(-1). The strongest interaction observed in this study was with the cyano group. Analysis of the series of groups CH2CH3, CH=CH2, C≡CH, and C≡N shows a correlation between conformational free-energy differences and the calculated charge on the C(α) atom of these substituents, which is indicative of the electrostatic nature of their π interactions. Changes in the free-energy differences of conformers show a linear dependence on the solvent hydrogen bond acceptor parameter β.

  16. Graphenes in the absence of metals as carbocatalysts for selective acetylene hydrogenation and alkene hydrogenation

    NASA Astrophysics Data System (ADS)

    Primo, Ana; Neatu, Florentina; Florea, Mihaela; Parvulescu, Vasile; Garcia, Hermenegildo

    2014-10-01

    Catalysis makes possible a chemical reaction by increasing the transformation rate. Hydrogenation of carbon-carbon multiple bonds is one of the most important examples of catalytic reactions. Currently, this type of reaction is carried out in petrochemistry at very large scale, using noble metals such as platinum and palladium or first row transition metals such as nickel. Catalysis is dominated by metals and in many cases by precious ones. Here we report that graphene (a single layer of one-atom-thick carbon atoms) can replace metals for hydrogenation of carbon-carbon multiple bonds. Besides alkene hydrogenation, we have shown that graphenes also exhibit high selectivity for the hydrogenation of acetylene in the presence of a large excess of ethylene.

  17. X-ray structure of linalool dehydratase/isomerase from Castellaniella defragrans reveals enzymatic alkene synthesis.

    PubMed

    Weidenweber, Sina; Marmulla, Robert; Ermler, Ulrich; Harder, Jens

    2016-05-01

    Linalool dehydratase/isomerase (Ldi), an enzyme of terpene degradation in Castellaniella defragrans, isomerizes the primary monoterpene alcohol geraniol into the tertiary alcohol (S)-linalool and dehydrates (S)-linalool to the alkene β-myrcene. Here we report on the crystal structures of Ldi with and without terpene substrates, revealing a cofactor-free homopentameric enzyme. The substrates were embedded inside a hydrophobic channel between two monomers of the (α,α)6 barrel fold class and flanked by three clusters of polar residues involved in acid-base catalysis. The detailed view into the active site will guide future biotechnological applications of Ldi, in particular, for industrial butadiene and isoprene production from renewable sources.

  18. Engineering Rieske Non-Heme Iron Oxygenases for the Asymmetric Dihydroxylation of Alkenes.

    PubMed

    Gally, Christine; Nestl, Bettina M; Hauer, Bernhard

    2015-10-26

    The asymmetric dihydroxylation of olefins is of special interest due to the facile transformation of the chiral diol products into valuable derivatives. Rieske non-heme iron oxygenases (ROs) represent promising biocatalysts for this reaction as they can be engineered to efficiently catalyze the selective mono- and dihydroxylation of various olefins. The introduction of a single point mutation improved selectivities (≥95 %) and conversions (>99 %) towards selected alkenes. By modifying the size of one active site amino acid side chain, we were able to modulate the regio- and stereoselectivity of these enzymes. For distinct substrates, mutants displayed altered regioselectivities or even favored opposite enantiomers compared to the wild-type ROs, offering a sustainable approach for the oxyfunctionalization of a wide variety of structurally different olefins.

  19. Hydrotrifluoromethylation and iodotrifluoromethylation of alkenes and alkynes using an inorganic electride as a radical generator.

    PubMed

    Choi, Sungkyu; Kim, Ye Ji; Kim, Sun Min; Yang, Jung Woon; Kim, Sung Wng; Cho, Eun Jin

    2014-09-12

    The trifluoromethyl (CF3) group is a staple synthon that can alter the physical and chemical properties of organic molecules. Despite recent advances in trifluoromethylation methods, the development of a general synthetic methodology for efficient and selective trifluoromethylation remains an ongoing challenge motivated by a steadily increasing demand from the pharmaceutical, agrochemical and materials science industries. In this article, we describe a simple, efficient and environmentally benign strategy for the hydrotrifluoromethylation of unactivated alkenes and alkynes through a radical-mediated reaction using an inorganic electride, [Ca2N](+) · e(-), as the electron source. In the transformation, anionic electrons are transferred from [Ca2N](+) · e(-) electrides to the trifluoromethylating reagent CF3I to initiate radical-mediated trifluoromethylation. The role of ethanol is pivotal in the transformation, acting as the solvent, an electron-releasing promoter and a hydrogen atom source. In addition, iodotrifluoromethylation of alkynes proceeds selectively upon the control of electride amount.

  20. Chemo- and regioselective homogeneous rhodium-catalyzed hydroamidomethylation of terminal alkenes to N-alkylamides.

    PubMed

    Raoufmoghaddam, Saeed; Drent, Eite; Bouwman, Elisabeth

    2013-09-01

    A rhodium/xantphos homogeneous catalyst system has been developed for direct chemo- and regioselective mono-N-alkylation of primary amides with 1-alkenes and syngas through catalytic hydroamidomethylation with 1-pentene and acetamide as model substrates. For appropriate catalyst performance, it appears to be essential that catalytic amounts of a strong acid promoter, such as p-toluenesulfonic acid (HOTs), as well as larger amounts of a weakly acidic protic promoter, particularly hexafluoroisopropyl alcohol (HOR(F) ) are applied. Apart from the product N-1-hexylacetamide, the isomeric unsaturated intermediates, hexanol and higher mass byproducts, as well as the corresponding isomeric branched products, can be formed. Under optimized conditions, almost full alkene conversion can be achieved with more than 80% selectivity to the product N-1-hexylamide. Interestingly, in the presence of a relatively high concentration of HOR(F) , the same catalyst system shows a remarkably high selectivity for the formation of hexanol from 1-pentene with syngas, thus presenting a unique example of a selective rhodium-catalyzed hydroformylation-hydrogenation tandem reaction under mild conditions. Time-dependent product formation during hydroamidomethylation batch experiments provides evidence for aldehyde and unsaturated intermediates; this clearly indicates the three-step hydroformylation/condensation/hydrogenation reaction sequence that takes place in hydroamidomethylation. One likely role of the weakly acidic protic promoter, HOR(F) , in combination with the strong acid HOTs, is to establish a dual-functionality rhodium catalyst system comprised of a neutral rhodium(I) hydroformylation catalyst species and a cationic rhodium(III) complex capable of selectively reducing the imide and/or ene-amide intermediates that are in a dynamic, acid-catalyzed condensation equilibrium with the aldehyde and amide in a syngas environment.

  1. Gold-catalyzed oxidative cycloadditions to activate a quinoline framework.

    PubMed

    Huple, Deepak B; Ghorpade, Satish; Liu, Rai-Shung

    2013-09-23

    Going for gold! Gold-catalyzed reactions of 3,5- and 3,6-dienynes with 8-alkylquinoline oxides results in an oxidative cycloaddition with high stereospecificity (see scheme; EWG = electron-withdrawing group); this process involves a catalytic activation of a quinoline framework. The reaction mechanism involves the intermediacy of α-carbonyl pyridinium ylides (I) in a concerted [3+2]-cycloaddition with a tethered alkene.

  2. One-step synthesis of 2-keto-3-deoxy-d-gluconate by biocatalytic dehydration of d-gluconate.

    PubMed

    Matsubara, Kohei; Köhling, Rudi; Schönenberger, Bernhard; Kouril, Theresa; Esser, Dominik; Bräsen, Christopher; Siebers, Bettina; Wohlgemuth, Roland

    2014-12-10

    2-Keto-3-deoxy-sugar acids are key intermediates of central metabolism and integral constituents of bacterial (lipo)polysaccharides and cell wall components and are therefore continuously and highly demanded in related research fields. The stereospecific chemical synthesis of chiral 2-keto-deoxy-sugar acids involves a multitude of reaction steps, while in metabolic pathways only few conversions lead to the same 2-keto-3-deoxy sugar acids from easily available carbohydrate precursors. Here we present a straightforward and highly economic one-step biocatalytic synthesis procedure of 2-keto-3-deoxy-d-gluconate (KDG) from d-gluconate using recombinant gluconate dehydratase (GAD) from the hyperthermophilic crenarchaeon Thermoproteus tenax. This method is highly advantageous to KDG production schemes described so far for several reasons: (i) the d-gluconate is completely converted to stereochemically pure D-KDG without side-product formation, (ii) the final KDG yield is approximately 90%, (iii) the newly developed quantitative and qualitative LC-MS analysis method enabled the simultaneous detection of d-gluconate and KDG and (iv) the T. tenax GAD as biocatalyst can be provided by a simple and rapid procedure involving only two precipitation steps. The described utilization of dehydratases for 2-keto-3-deoxy sugar acid syntheses represents a highly resource-efficient one-step preparation and offers potential short synthetic routes toward a broad range of 2-keto-3-deoxy sugar acids and their derivatives.

  3. Non-water miscible ionic liquid improves biocatalytic production of geranyl glucoside with Escherichia coli overexpressing a glucosyltransferase.

    PubMed

    Schmideder, Andreas; Priebe, Xenia; Rubenbauer, Mark; Hoffmann, Thomas; Huang, Fong-Chin; Schwab, Wilfried; Weuster-Botz, Dirk

    2016-09-01

    Whole cells of Escherichia coli overexpressing a glucosyltransferase from Vitis vinifera were used for the glucosylation of geraniol to geranyl glucoside. A high cell density cultivation process for the production of whole-cell biocatalysts was developed, gaining a dry cell mass concentration of up to 67.6 ± 1.2 g L(-1) and a glucosyltransferase concentration of up to 2.7 ± 0.1 g protein L(-1) within a process time of 48 h. Whole-cell batch biotransformations in milliliter-scale stirred-tank bioreactors showed highest conversion of geraniol at pH 7.0 although the pH optimum of the purified glucosyltransferase was at pH 8.5. The biocatalytic batch process performance was improved significantly by the addition of a water-immiscible ionic liquid (N-hexylpyridinium bis(trifluoromethylsulfonyl)imid) for in situ substrate supply. The so far highest final geranyl glucoside concentration (291 ± 9 mg L(-1)) and conversion (71 ± 2 %) reported for whole-cell biotransformations of geraniol were achieved with 5 % (v/v) of the ionic liquid. PMID:27142377

  4. Biocatalytic potential of lipase from Staphylococcus sp. MS1 for transesterification of jatropha oil into fatty acid methyl esters.

    PubMed

    Sharma, Monika; Singh, Shelley Sardul; Maan, Pratibha; Sharma, Rohit

    2014-11-01

    An extracellular lipase producing isolate Staphylococcus sp. MS1 was optimized for lipase production and its biocatalytic potential was assessed. Medium with tributyrin (0.25 %) and without any exogenous inorganic nitrogen source was found to be optimum for lipase production from Staphylococcus sp. MS1. The optimum pH and temperature for lipase production were found to be pH 7 and 37 °C respectively, showing lipase activity of 37.91 U. It showed good lipase production at pH 6-8. The lipase was found to be stable in organic solvents like hexane and petroleum ether, showing 98 and 88 % residual activity respectively. The biotransformation using the concentrated enzyme in petroleum ether resulted in the synthesis of fatty acid methyl esters like methyl oleate, methyl palmitate and methyl stearate. Thus, the lipase under study has got the potential to bring about transesterification of oils into methyl esters which can be exploited for various biotechnological applications. PMID:25115850

  5. Adsorption of enzymes to stimuli-responsive polymer brushes: Influence of brush conformation on adsorbed amount and biocatalytic activity.

    PubMed

    Koenig, Meike; Bittrich, Eva; König, Ulla; Rajeev, Bhadra Lakshmi; Müller, Martin; Eichhorn, Klaus-Jochen; Thomas, Sabu; Stamm, Manfred; Uhlmann, Petra

    2016-10-01

    Polyelectrolyte brushes can be utilized to immobilize enzymes on macroscopic surfaces. This report investigates the influence of the pH value of the surrounding medium on the amount and the activity of enzymes adsorbed to poly(2-vinylpyridine) and poly(acrylic acid) brushes, as well as the creation of thermoresponsive biocatalytically active coatings via the adsorption of enzymes onto a mixed brush consisting of a polyelectrolyte and temperature-sensitive poly(N-isopropylacryl amide). Spectroscopic ellipsometry and attenuated total reflection-Fourier transform infrared spectroscopy are used to monitor the adsorption process. Additionally, infrared spectra are evaluated in terms of the secondary structure of the enzymes. Glucose oxidase is used as a model enzyme, where the enzymatic activity is measured after different adsorption conditions. Poly(acrylic acid) brushes generally adsorb larger amounts of enzyme, while less glucose oxidase is found on poly(2-vinylpyridine), which however exhibits higher specific activity. This difference in activity could be attributed to a difference in secondary structure of the adsorbed enzyme. For glucose oxidase adsorbed to mixed brushes, switching of enzymatic activity between an active state at 20°C and a less active state at 40°C as compared to the free enzyme in solution is observed. However, this switching is strongly depending on pH in mixed brushes of poly(acrylic acid) and poly(N-isopropylacryl amide) due to interactions between the polymers.

  6. Adsorption of enzymes to stimuli-responsive polymer brushes: Influence of brush conformation on adsorbed amount and biocatalytic activity.

    PubMed

    Koenig, Meike; Bittrich, Eva; König, Ulla; Rajeev, Bhadra Lakshmi; Müller, Martin; Eichhorn, Klaus-Jochen; Thomas, Sabu; Stamm, Manfred; Uhlmann, Petra

    2016-10-01

    Polyelectrolyte brushes can be utilized to immobilize enzymes on macroscopic surfaces. This report investigates the influence of the pH value of the surrounding medium on the amount and the activity of enzymes adsorbed to poly(2-vinylpyridine) and poly(acrylic acid) brushes, as well as the creation of thermoresponsive biocatalytically active coatings via the adsorption of enzymes onto a mixed brush consisting of a polyelectrolyte and temperature-sensitive poly(N-isopropylacryl amide). Spectroscopic ellipsometry and attenuated total reflection-Fourier transform infrared spectroscopy are used to monitor the adsorption process. Additionally, infrared spectra are evaluated in terms of the secondary structure of the enzymes. Glucose oxidase is used as a model enzyme, where the enzymatic activity is measured after different adsorption conditions. Poly(acrylic acid) brushes generally adsorb larger amounts of enzyme, while less glucose oxidase is found on poly(2-vinylpyridine), which however exhibits higher specific activity. This difference in activity could be attributed to a difference in secondary structure of the adsorbed enzyme. For glucose oxidase adsorbed to mixed brushes, switching of enzymatic activity between an active state at 20°C and a less active state at 40°C as compared to the free enzyme in solution is observed. However, this switching is strongly depending on pH in mixed brushes of poly(acrylic acid) and poly(N-isopropylacryl amide) due to interactions between the polymers. PMID:27447452

  7. Biotechnological production of fucosylated human milk oligosaccharides: Prokaryotic fucosyltransferases and their use in biocatalytic cascades or whole cell conversion systems.

    PubMed

    Petschacher, Barbara; Nidetzky, Bernd

    2016-10-10

    Human milk oligosaccharides (HMOs) constitute a class of complex carbohydrates unique to mother's milk and are strongly correlated to the health benefits of breastfeeding in infants. HMOs are important as functional ingredients of advanced infant formula and have attracted broad interest for use in health-related human nutrition. About 50% of the HMOs structures contain l-fucosyl residues, which are introduced into nascent oligosaccharides by enzymatic transfer from GDP-l-fucose. To overcome limitation in the current availability of fucosylated HMOs, biotechnological approaches for their production have been developed. Functional expression of the fucosyltransferase(s) and effective supply of GDP-l-fucose, respectively, are both bottlenecks of the biocatalytic routes of synthesis. Strategies of in vitro and in vivo production of fucosylated HMOs are reviewed here. Besides metabolic engineering for enhanced HMO production in whole cells, the focus is on the characteristics and the heterologous overexpression of prokaryotic α1,2- and α1,3/4-fucosyltransferases. Up to 20g/L of fucosylated HMOs were obtained in optimized production systems. Optimized expression enabled recovery of purified fucosyltransferases in a yield of up to 45mg/L culture for α1,2-fucosyltransferases and of up to 200mg protein/L culture for α1,3/4-fucosyltransferases.

  8. Applications of biocatalytic arene ipso,ortho cis-dihydroxylation in synthesis.

    PubMed

    Lewis, Simon E

    2014-03-18

    The dearomatising dihydroxylation of aromatic molecules mediated by arene dioxygenase enzymes can provide cyclohexadiene-diols that are versatile starting materials for organic synthesis. Whereas oxidation of a substituted arene to give its ortho,meta-dihydrodiol has been demonstrated for numerous substrates and dioxygenases, formation of ipso,ortho-dihydrodiols has historically been underutilised in comparison. This feature article presents a chronological account of reported uses of such diols.

  9. Enantioselective Synthesis of Spirobarbiturate-Cyclohexenes through Phosphine-Catalyzed Asymmetric [4 + 2] Annulation of Barbiturate-Derived Alkenes with Allenoates.

    PubMed

    Liu, Honglei; Liu, Yang; Yuan, Chunhao; Wang, Guo-Peng; Zhu, Shou-Fei; Wu, Yang; Wang, Bo; Sun, Zhanhu; Xiao, Yumei; Zhou, Qi-Lin; Guo, Hongchao

    2016-03-18

    An enantioselective synthesis of pharmaceutically important spirobarbiturates has been achieved via spirocyclic chiral phosphine-catalyzed asymmetric [4 + 2] annulation of barbiturate-derived alkenes with allenoates. With the use of this tool, various spirobarbiturate-cyclohexenes are obtained in good to excellent yields with excellent diastereo- and enantioselectivities. A wide range of α-substituted allenoates and barbiturate-derived alkenes were tolerated. PMID:26937706

  10. Diastereodivergent synthesis of trisubstituted alkenes through protodeboronation of allylic boronic esters: application to the synthesis of the Californian red scale beetle pheromone.

    PubMed

    Hesse, Matthew J; Butts, Craig P; Willis, Christine L; Aggarwal, Varinder K

    2012-12-01

    E-allylic boronic esters undergo a highly diastereoselective protodeboronation with TBAF⋅3 H(2)O to give Z-trisubstituted alkenes. The selectivity can be switched to give predominantly the E-alkene instead by using KHF(2)/TsOH (see scheme). The utility of the methodology has been illustrated in a short synthesis of a component of the sex pheromone of the Californian red scale beetle. PMID:23129403

  11. Efficient biocatalytic synthesis of (R)-[3,5-bis(trifluoromethyl)phenyl] ethanol by a newly isolated Trichoderma asperellum ZJPH0810 using dual cosubstrate: ethanol and glycerol.

    PubMed

    Li, Jun; Wang, Pu; He, Jun-Yao; Huang, Jin; Tang, Jun

    2013-08-01

    (R)-[3,5-bis(trifluoromethyl)phenyl] ethanol is a crucial intermediate for the synthesis of Aprepitant. An efficient biocatalytic process for (R)-[3,5-bis(trifluoromethyl)phenyl] ethanol was developed via the asymmetric reduction of 3,5-bis(trifluoromethyl) acetophenone, catalyzed by whole cells of newly isolated Trichoderma asperellum ZJPH0810 using ethanol and glycerol as dual cosubstrate for cofactor recycling. A fungal strain ZJPH0810, showing asymmetric biocatalytic activity of 3,5-bis(trifluoromethyl) acetophenone to its corresponding (R)-[3,5-bis(trifluoromethyl)phenyl] ethanol, was isolated from a soil sample. Based on its morphological and physiological characteristics and internal transcribed spacer sequence, this isolate was identified as T. asperellum ZJPH0810, which afforded an NADH-dependent (R)-stereospecific carbonyl reductase and was a promising biocatalyst for the synthesis of (R)-[3,5-bis(trifluoromethyl)phenyl] ethanol. Some key reaction parameters involved in the bioreduction catalyzed by T. asperellum ZJPH0810 were subsequently optimized. The effectiveness of (R)-[3,5-bis(trifluoromethyl)phenyl] ethanol production was significantly enhanced by employing a novel dual cosubstrate-coupled system for cofactor recycling. The established efficient bioreduction system contained 50 mM of 3,5-bis(trifluoromethyl) acetophenone and 60 g l(-1) of resting cells, employing ethanol (6.0 %, v/v) and glycerol (0.5 %, v/v) as dual cosubstrate. The bioreduction was performed in distilled water medium, at 30 °C and 200 rpm. Under the above conditions, a best yield of 93.4 % was obtained, which is nearly a 3.5-fold increase in contrast to no addition of cosubstrate. The ee value of the product reached above 98 %. This biocatalytic process shows great potential in the production of (R)-[3,5-bis(trifluoromethyl)phenyl] ethanol, a valuable chiral building block in the pharmaceutical industry.

  12. Efficient alkene epoxidation catalyzed by molybdenyl acetylacetonate supported on aminated UiO-66 metal-organic framework

    NASA Astrophysics Data System (ADS)

    Kardanpour, Reihaneh; Tangestaninejad, Shahram; Mirkhani, Valiollah; Moghadam, Majid; Mohammadpoor-Baltork, Iraj; Zadehahmadi, Farnaz

    2015-03-01

    Metal-organic frameworks (MOFs) containing Mo Schiff base complexes were prepared by post-synthesis method and applied as efficient catalysts in the epoxidation of alkenes with tert-BuOOH. In this manner, UiO-66-NH2 (UiO=University of Oslo) MOF was reacted with salicylaldehyde and thiophene-2-carbaldehyde to produce bidentate Schiff bases. Then, the Schiff base ligands were used for immobilization of molybdenyl acetylacetonate. These new catalysts were characterized by FT-IR, UV-vis spectroscopic techniques, X-ray diffraction (XRD), BET, inductively coupled plasma atomic emission spectroscopy (ICP-AES) and field emission scanning electron microscopy (FE-SEM). These catalytic systems showed excellent activity in the epoxidation of alkenes such as cyclic and linear ones with tert-butyl hydroperoxide (TBHP) in 1,2-dichloroethane, and reused several times without any appreciable loss of their activity.

  13. Production of hydrogen peroxide and organic peroxides in the gas phase reactions of ozone with natural alkenes

    SciTech Connect

    Simonaitis, R.; Olszyna, K.J.; Meagher, J.F.

    1991-01-01

    The formation of H{sub 2}O{sub 2} and organic peroxides in the reaction of O{sub 3} with trans-2-butene and naturally occurring alkenes has been studied using a 31 m{sup 3} reaction chamber. H{sub 2}O{sub 2} and organic peroxides were found to be products of the O{sub 3} reaction with trans-2-butene, isoprene, {alpha} and {beta}-pinene, and limonene. Water is necessary for the formation of H{sub 2}O{sub 2} and most of the H{sub 2}O{sub 2} is formed via a route that does not involve HO{sub 2} radicals. These results indicate that the reaction of O{sub 3} with natural alkenes may be a significant source of atmospheric H{sub 2}O{sub 2}, particularly in forest and rural areas.

  14. The different roles of a cationic gold(i) complex in catalysing hydroarylation of alkynes and alkenes with a heterocycle.

    PubMed

    Mehrabi, Tahmineh; Ariafard, Alireza

    2016-08-01

    The mechanism of twofold hydroarylation of terminal alkynes with pyrrole catalyzed by a cationic gold(i) complex was investigated using DFT. It was found that while both the hydroarylation reactions proceed via a Friedel-Crafts-type mechanism, the first hydroarylation is directly promoted by gold(i) but the second hydroarylation by a proton released through interaction of the alkene product with gold-bound acidic organic species such as acetic acid and terminal alkynes. PMID:27377712

  15. Catalyst-Free Difunctionalization of Activated Alkenes in Water: Efficient Synthesis of β-Keto Sulfides and Sulfones.

    PubMed

    Wang, Huamin; Wang, Guangyu; Lu, Qingquan; Chiang, Chien-Wei; Peng, Pan; Zhou, Jiufu; Lei, Aiwen

    2016-10-01

    Difunctionalization of activated alkenes, a powerful strategy in chemical synthesis, has been accomplished for direct synthesis of a series of β-keto sulfides and β-keto sulfones. The transformation, mediated by O2 , proceeds smoothly in water and without any catalyst. Prominent advantages of this method include mild reaction conditions, purification simplicity, and gram-scale synthesis, underlining the practical utility of this methodology. PMID:27500979

  16. Yields of beta-hydroxynitrates, dihydroxynitrates, and trihydroxynitrates formed from OH radical-initiated reactions of 2-methyl-1-alkenes.

    PubMed

    Matsunaga, Aiko; Ziemann, Paul J

    2010-04-13

    Yields of beta-hydroxynitrates, dihydroxynitrates, and trihydroxynitrates, in particles formed from OH radical-initiated reactions of C(9)-C(15) 2-methyl-1-alkenes in the presence of NO(x) were measured by using a thermal desorption particle beam mass spectrometer coupled to a high-performance liquid chromatograph with a UV-visible (UV-vis) detector. Yields of beta-hydroxynitrates and dihydroxynitrates increased with carbon number primarily due to enhanced gas-to-particle partitioning before reaching plateaus at approximately C(14)-C(15), where the compounds were essentially entirely in the particle phase. Plateau yields of beta-hydroxynitrates, dihydroxynitrates, and trihydroxynitrates were 0.183 +/- 0.005, 0.045 +/- 0.005, and 0.034 +/- 0.005, and, after normalization for OH radical addition to the C = C double bond, were 0.225 +/- 0.007, 0.055 +/- 0.006, and 0.042 +/- 0.006. The fractions of 1-hydroxy and 2-hydroxy beta-hydroxynitrate isomers were 0.90/0.10. Yields measured here and in our previous study of reactions of linear internal alkenes and linear 1-alkenes indicate that, for these alkene classes, the relative branching ratios for forming tertiary, secondary, and primary beta-hydroxyalkyl radicals by OH radical addition to the C=C double bond are 4.3/1.9/1.0, and the branching ratios for forming beta-hydroxynitrates from reactions of tertiary, secondary, and primary beta-hydroxyperoxy radicals with NO are 0.25, 0.15, and 0.12. The effects of H(2)O vapor and NH(3) on yields were also explored.

  17. Synthesis and acid-catalyzed transformations of 1-(1,6,6-trimethylbicyclo(2. 1. 1)hex-5-yl)-1-alkanones and 1-(1,6,6-trimethylbicyclo-(2. 1. 1)hex-5-yl)-1-alken-1-ones

    SciTech Connect

    Volkova, O.O.; Cherkaev, G.V.; Novikov, N.A.; Erman, M.B.; Aul'chenko, I.S.; Mochalin, V.B.

    1988-06-20

    The reaction of 1,6,6-trimethylbicyclo(2.1.1)hexane-5-carbaldehyde (photocitral B) with Grignard reagents followed by oxidation of the obtained alcohols gave 1-(1,6,6-trimethylbicyclo(2.1.1)hex-5-yl)-1-alkanones and 1-(1,6,6-trimethylbicyclo(2.1.1)hex-5-yl)-1-alken-1-ones, which isomerize to 1-(2,3,3-trimethyl-1-cyclopentenyl)-2-alkanones when heated in the presence of p-toluenesulfonic acid. It was shown that the intermediate compounds in this reaction are 1-(2,2,3-trimethyl-3-cyclopentenyl)-2-alkanones. Underanalogous conditions photocitral B isomerizes to /alpha/-campholenaldehyde.

  18. Metal-catalyzed hydrosilylation of alkenes and alkynes using dimethyl(pyridyl)silane.

    PubMed

    Itami, Kenichiro; Mitsudo, Koichi; Nishino, Akira; Yoshida, Jun-ichi

    2002-04-19

    Metal-catalyzed hydrosilylation of alkenes and alkynes using dimethyl(pyridyl)silane is described. The hydrosilylation of alkenes using dimethyl(2-pyridyl)silane (2-PyMe(2)SiH) proceeded well in the presence of a catalytic amount of RhCl(PPh(3))(3) with virtually complete regioselectivity. By taking advantage of the phase tag property of the 2-PyMe(2)Si group, hydrosilylation products were isolated in greater than 95% purity by simple acid-base extraction. Strategic catalyst recovery was also demonstrated. The hydrosilylation of alkynes using 2-PyMe(2)SiH proceeded with a Pt(CH(2)=CHSiMe(2))(2)O/P(t-Bu)(3) catalyst to give alkenyldimethyl(2-pyridyl)silanes in good yield with high regioselectivity. A reactivity comparison of 2-PyMe(2)SiH with other related hydrosilanes (3-PyMe(2)SiH, 4-PyMe(2)SiH, and PhMe(2)SiH) was also performed. In the rhodium-catalyzed reaction, the reactivity order of hydrosilane was 2-PyMe(2)SiH > 3-PyMe(2)SiH, 4-PyMe(2)SiH, PhMe(2)SiH, indicating a huge rate acceleration with 2-PyMe(2)SiH. In the platinum-catalyzed reaction, the reactivity order of hydrosilane was PhMe(2)SiH, 3-PyMe(2)SiH > 4-PyMe(2)SiH > 2-PyMe(2)SiH, indicating a rate deceleration with 2-PyMe(2)SiH and 4-PyMe(2)SiH. It seems that these reactivity differences stem primarily from the governance of two different mechanisms (Chalk-Harrod and modified Chalk-Harrod mechanisms). From the observed reactivity order, coordination and electronic effects of dimethyl(pyridyl)silanes have been implicated.

  19. Iron-copper cooperative catalysis in the reactions of alkyl Grignard reagents: exchange reaction with alkenes and carbometalation of alkynes.

    PubMed

    Shirakawa, Eiji; Ikeda, Daiji; Masui, Seiji; Yoshida, Masatoshi; Hayashi, Tamio

    2012-01-11

    Iron-copper cooperative catalysis is shown to be effective for an alkene-Grignard exchange reaction and alkylmagnesiation of alkynes. The Grignard exchange between terminal alkenes (RCH═CH(2)) and cyclopentylmagnesium bromide was catalyzed by FeCl(3) (2.5 mol %) and CuBr (5 mol %) in combination with PBu(3) (10 mol %) to give RCH(2)CH(2)MgBr in high yields. 1-Alkyl Grignard reagents add to alkynes in the presence of a catalyst system consisting of Fe(acac)(3), CuBr, PBu(3), and N,N,N',N'-tetramethylethylenediamine to give β-alkylvinyl Grignard reagents. The exchange reaction and carbometalation take place on iron, whereas copper assists with the exchange of organic groups between organoiron and organomagnesium species through transmetalation with these species. Sequential reactions consisting of the alkene-Grignard exchange and the alkylmagnesiation of alkynes were successfully conducted by adding an alkyne to a mixture of the first reaction. Isomerization of Grignard reagents from 2-alkyl to 1-alkyl catalyzed by Fe-Cu also is applicable as the first 1-alkyl Grignard formation step. PMID:22128888

  20. Yields of beta-hydroxynitrates and dihydroxynitrates in aerosol formed from OH radical-initiated reactions of linear alkenes in the presence of NO(x).

    PubMed

    Matsunaga, Aiko; Ziemann, Paul J

    2009-01-22

    Yields of beta-hydroxynitrates and dihydroxynitrates in aerosol formed from OH radical-initiated reactions of linear C(8)-C(17) 1-alkenes and C(14)-C(17) internal alkenes in the presence of NO(x) were measured using a thermal desorption particle beam mass spectrometer coupled to a high-performance liquid chromatograph (HPLC) with UV-vis detector for identification and quantification. For 1-alkenes, total yields of beta-hydroxynitrates normalized for OH radical addition to the CC double bond increased with carbon number, primarily because of enhanced gas-to-particle partitioning, to a plateau of 0.140 +/- 0.009 in the C(14)-C(17) range, with 1-hydroxy/2-hydroxy isomer fractions of 0.7:0.3. When combined with yields measured by O'Brien et al. ( O'Brien , J. M. , Czuba , E. , Hastie , D. R. , Francisco , J. S. , and Shepson , P. S. J. Phys. Chem. A 1998 , 102 , 8903 ) for reactions of smaller alkenes, the results for both 1-alkenes and internal alkenes indicate that the branching ratios for the formation of beta-hydroxynitrates from the reactions of NO with beta-hydroxyperoxy radicals (averaged over both isomers) increase from 0.009 for C(2) up to 0.13-0.15 for C(14) and larger and are approximately half the values determined by Arey et al. ( Arey , J. , Aschmann , S. M. , Kwok , E. S. C. , and Atkinson , R. J. Phys. Chem. A 2001 , 105 , 1020 ) for the corresponding alkyl peroxy radicals. The range of branching ratios may be higher for individual isomers, but this could not be determined. It is estimated that for 1-alkenes, approximately 60-70% of OH radical addition occurred at the terminal carbon atom. Average yields of dihydroxynitrates normalized for OH radical addition were 0.039 +/- 0.006 and 0.006 +/- 0.002 for 1-alkenes and internal alkenes, with differences reflecting enhanced decomposition of beta-hydroxyalkoxy radicals formed from internal alkenes. The addition of NH(3) reduced yields significantly, apparently by altering hydrogen bonding between hydroxy

  1. Residues Controlling Facial Selectivity in an Alkene Reductase and Semirational Alterations to Create Stereocomplementary Variants

    PubMed Central

    2015-01-01

    A systematic saturation mutagenesis campaign was carried out on an alkene reductase from Pichia stipitis (OYE 2.6) to develop variants with reversed stereoselectivities. Wild-type OYE 2.6 reduces three representative Baylis–Hillman adducts to the corresponding S products with almost complete stereoselectivities and good catalytic efficiencies. We created and screened 13 first-generation, site-saturation mutagenesis libraries, targeting residues found near the bound substrate. One variant (Tyr78Trp) showed high R selectivity toward one of the three substrates, but no change (cyclohexenone derivative) and no catalytic activity (acrylate derivative) for the other two. Subsequent rounds of mutagenesis retained the Tyr78Trp mutation and explored other residues that impacted stereoselectivity when altered in a wild-type background. These efforts yielded double and triple mutants that possessed inverted stereoselectivities for two of the three substrates (conversions >99% and at least 91% ee (R)). To understand the reasons underlying the stereochemical changes, we solved crystal structures of two key mutants: Tyr78Trp and Tyr78Trp/Ile113Cys, the latter with substrate partially occupying the active site. By combining these experimental data with modeling studies, we have proposed a rationale that explains the impacts of the most useful mutations. PMID:25068071

  2. Secondary ozonides of endo-cyclic alkenes analyzed by atmospheric sampling Townsend discharge ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Nøjgaard, J. K.; Nørgaard, A. W.; Wolkoff, P.

    2007-05-01

    Secondary ozonides (SOZ) of cyclohexene, 1-methylcyclohexene, 4-isopropyl-1-methylcyclohexene and d-limonene were cryo-synthesized by ozonolysis in pentane and purified on a silica gel column. The mass spectra obtained by atmospheric sampling Townsend discharge ionization (ASTDI) and collision activated dissociation (CAD) of the protonized SOZ showed characteristic losses evident of the ozonide structure. Oxygen was eliminated as, e.g., O and O2, and loss of (HCHO + HCHO) or (O + CO2) corresponded to the SOZ base-peak for the substituted cyclohexenes by ASTDI-MS. The CAD spectra of the protonized species by use of methane as chemical ionization gas, showed consecutive losses of three oxygen atoms. Elimination of hydroxy-methyl hydroperoxide (HMHP) was particular important for the protonized SOZ, unlike consecutive loss of (HCHO + HCHO) or (O + CO2). In addition, the spectra of d-limonene were characterized by an unique loss of H2O2. These losses appear to be useful for identification of SOZ in gas-phase ozonolysis mixtures of endo-cyclic alkenes, which makes ASTDI an alternative to other on-line techniques for analysis of SOZ in ozonolysis mixtures.

  3. Microbial biosynthesis of medium-chain 1-alkenes by a nonheme iron oxidase.

    PubMed

    Rui, Zhe; Li, Xin; Zhu, Xuejun; Liu, Joyce; Domigan, Bonnie; Barr, Ian; Cate, Jamie H D; Zhang, Wenjun

    2014-12-23

    Aliphatic medium-chain 1-alkenes (MCAEs, ∼10 carbons) are "drop-in" compatible next-generation fuels and precursors to commodity chemicals. Mass production of MCAEs from renewable resources holds promise for mitigating dependence on fossil hydrocarbons. An MCAE, such as 1-undecene, is naturally produced by Pseudomonas as a semivolatile metabolite through an unknown biosynthetic pathway. We describe here the discovery of a single gene conserved in Pseudomonas responsible for 1-undecene biosynthesis. The encoded enzyme is able to convert medium-chain fatty acids (C10-C14) into their corresponding terminal olefins using an oxygen-activating, nonheme iron-dependent mechanism. Both biochemical and X-ray crystal structural analyses suggest an unusual mechanism of β-hydrogen abstraction during fatty acid substrate activation. Our discovery unveils previously unidentified chemistry in the nonheme Fe(II) enzyme family, provides an opportunity to explore the biology of 1-undecene in Pseudomonas, and paves the way for tailored bioconversion of renewable raw materials to MCAE-based biofuels and chemical commodities.

  4. Formation of hydrogen peroxide in the ozonolysis of isoprene and simple alkenes under humid conditions

    NASA Astrophysics Data System (ADS)

    Sauer, Frank; Schäfer, Christian; Neeb, Peter; Horie, Osamu; Moortgat, Geert K.

    The ozonolysis of isobutene and isoprene was performed in a 570 ℓ static reactor at 295 K and 730 Torr synthetic air in the presence and absence of water vapour, with the reactant concentration ranges of 1-6 ppmv. Products were analysed by a combination of FTIR spectroscopy, GC-FID, and HPLC. For both alkenes, the yields of H 2O 2 and the primary carbonyl products (acetone for isobutene, methacrolein and methylvinyl ketone for isoprene) increased under humid conditions. In the isoprene ozonolysis, the H 2O 2 yields relative to the O 3 conversion were, as determined from the initial rate of the formation, 1 and 9% for dry and humid conditions, respectively. The increase in its yield under the humid conditions was correlated with the sum of the increase in the yields of methacrolein and methylvinyl ketone (˜13%). This was explained by rapid decomposition of the transient α-hydroxy hydroperoxides formed in the reaction of H 2O with the two stabilised C 4 Criegee intermediates. Atmospheric relevance of the results is discussed.

  5. Biocatalytic organic synthesis of optically pure (S)-scoulerine and berbine and benzylisoquinoline alkaloids.

    PubMed

    Schrittwieser, Joerg H; Resch, Verena; Wallner, Silvia; Lienhart, Wolf-Dieter; Sattler, Johann H; Resch, Jasmin; Macheroux, Peter; Kroutil, Wolfgang

    2011-08-19

    A chemoenzymatic approach for the asymmetric total synthesis of the title compounds is described that employs an enantioselective oxidative C-C bond formation catalyzed by berberine bridge enzyme (BBE) in the asymmetric key step. This unique reaction yielded enantiomerically pure (R)-benzylisoquinoline derivatives and (S)-berbines such as the natural product (S)-scoulerine, a sedative and muscle relaxing agent. The racemic substrates rac-1 required for the biotransformation were prepared in 4-8 linear steps using either a Bischler-Napieralski cyclization or a C1-Cα alkylation approach. The chemoenzymatic synthesis was applied to the preparation of fourteen enantiomerically pure alkaloids, including the natural products (S)-scoulerine and (R)-reticuline, and gave overall yields of up to 20% over 5-9 linear steps.

  6. Biocatalytic Organic Synthesis of Optically Pure (S)-Scoulerine and Berbine and Benzylisoquinoline Alkaloids

    PubMed Central

    2011-01-01

    A chemoenzymatic approach for the asymmetric total synthesis of the title compounds is described that employs an enantioselective oxidative C–C bond formation catalyzed by berberine bridge enzyme (BBE) in the asymmetric key step. This unique reaction yielded enantiomerically pure (R)-benzylisoquinoline derivatives and (S)-berbines such as the natural product (S)-scoulerine, a sedative and muscle relaxing agent. The racemic substrates rac-1 required for the biotransformation were prepared in 4–8 linear steps using either a Bischler–Napieralski cyclization or a C1–Cα alkylation approach. The chemoenzymatic synthesis was applied to the preparation of fourteen enantiomerically pure alkaloids, including the natural products (S)-scoulerine and (R)-reticuline, and gave overall yields of up to 20% over 5–9 linear steps. PMID:21739961

  7. Oxidation of dibenzothiophene catalyzed by hemoglobin and other hemoproteins in various aqueous-organic media

    SciTech Connect

    Klyachko, N.L. Klibanov, A.M. )

    1992-10-01

    Biocatalytic oxidation of dibenzothiophene (a model of organic sulfur in coal) with hydrogen peroxide was investigated. It was found that various hemoproteins, both enzymic (e.g., horseradish peroxidase) and nonenzymic (e.g., bovine blood hemoglobin), readily oxidized dibensothiophene to its S-oxide and, to a minor extent, further to its S-dioxide (sulfone). This process catalyzed by hemoglobin was competent as an oxidation catalyst even in nearly dry organic solvents (with protic, acidic solvents being optimal), the highest conversions were observed in predominantly aqueous media. The hemoglobin-catalyzed oxidation of dibenzothiophene at low concentrations of the protein stopped long before all the substrate was oxidized. This phenomenon was caused by inactivation of hemoglobin by hydrogen peroxide that destroyed the heme moiety. The maximal degree of the hemoglobin-catalyzed dibenzothiophene oxidation was predicted, and found, to be strongly dependent on the reaction medium composition. 24 refs., 7 figs., 3 tabs.

  8. Biocatalytic carboxylation of phenol derivatives: kinetics and thermodynamics of the biological Kolbe-Schmitt synthesis.

    PubMed

    Pesci, Lorenzo; Glueck, Silvia M; Gurikov, Pavel; Smirnova, Irina; Faber, Kurt; Liese, Andreas

    2015-04-01

    Microbial decarboxylases, which catalyse the reversible regioselective ortho-carboxylation of phenolic derivatives in anaerobic detoxification pathways, have been studied for their reverse carboxylation activities on electron-rich aromatic substrates. Ortho-hydroxybenzoic acids are important building blocks in the chemical and pharmaceutical industries and are currently produced via the Kolbe-Schmitt process, which requires elevated pressures and temperatures (≥ 5 bar, ≥ 100 °C) and often shows incomplete regioselectivities. In order to resolve bottlenecks in view of preparative-scale applications, we studied the kinetic parameters for 2,6-dihydroxybenzoic acid decarboxylase from Rhizobium sp. in the carboxylation- and decarboxylation-direction using 1,2-dihydroxybenzene (catechol) as starting material. The catalytic properties (K(m), V(max)) are correlated with the overall thermodynamic equilibrium via the Haldane equation, according to a reversible random bi-uni mechanism. The model was subsequently verified by comparing experimental results with simulations. This study provides insights into the catalytic behaviour of a nonoxidative aromatic decarboxylase and reveals key limitations (e.g. substrate oxidation, CO2 pressure, enzyme deactivation, low turnover frequency) in view of the employment of this system as a 'green' alternative to the Kolbe-Schmitt processes.

  9. Biocatalytic synthesis of polymeric nanowires by micellar templates of ionic surfactants

    SciTech Connect

    Nazari, K.; Adhami, F.; Najjar-Safari, A.; Salmani, S.; Mahmoudi, A.

    2011-07-15

    Highlights: {yields} Soft-template production of polyguaiacol nanowire was done by peroxidase enzyme. {yields} Main advantage of this simple method is producing soluble encapsulated nanowires. {yields} Nanowire can be easily precipitated and separated by dilution with distilled water. {yields} Size tuned templates of sodium decyl sulfate (d = 2.7 nm) gave nanowires with d = 2-4 nm. {yields} Dried surfactant-coated wires recover freshly on specified and desired applications. -- Abstract: Micelle-templated polyguaiacol nanowires were successfully prepared via polymerization oxidation of guaiacol (o-methoxy phenol) by peroxidase enzyme in the presence of hydrogen peroxide at mild reaction conditions. The dimensions of the prepared nanowires were controlled by tuning the size and shape of the micelle structure via changing and controlling the type, chain length and molar concentrations of the ionic surfactant. The progress of the reaction and estimation of the size of soft micellar templates were followed by UV-Vis spectroscopy and dynamic light scattering (DLS). The resulting micelle encapsulated or purified polyguaiacol nanowires were characterized using transmission electron microscopy (TEM).

  10. Metal-Organic Frameworks as Catalysts for Oxidation Reactions.

    PubMed

    Dhakshinamoorthy, Amarajothi; Asiri, Abdullah M; Garcia, Hermenegildo

    2016-06-01

    This Concept is aimed at describing the current state of the art in metal-organic frameworks (MOFs) as heterogeneous catalysts for liquid-phase oxidations, focusing on three important substrates, namely, alkenes, alkanes and alcohols. Emphases are on the nature of active sites that have been incorporated within MOFs and on future targets to be set in this area. Thus, selective alkene epoxidation with peroxides or oxygen catalyzed by constitutional metal nodes of MOFs as active sites are still to be developed. Moreover, no noble metal-free MOF has been reported to date that can act as a general catalyst for the aerobic oxidation of primary and secondary aliphatic alcohols. In contrast, in the case of alkanes, a target should be to tune the polarity of MOF internal pores to control the outcome of the autooxidation process, resulting in the selective formation of alcohol/ketone mixtures at high conversion.

  11. Determination of lipid oxidation products in vegetable oils and marine omega-3 supplements

    PubMed Central

    Halvorsen, Bente Lise; Blomhoff, Rune

    2011-01-01

    Background There is convincing evidence that replacing dietary saturated fats with polyunsaturated fats (PUFA) decreases risk of cardiovascular diseases. Therefore, PUFA rich foods such as vegetable oils, fatty fish, and marine omega-3 supplements are recommended. However, PUFA are easily oxidizable and there is concern about possible negative health effects from intake of oxidized lipids. Little is known about the degree of lipid oxidation in such products. Objective To assess the content of lipid oxidation products in a large selection of vegetable oils and marine omega-3 supplements available in Norway. Both fresh and heated vegetable oils were studied. Design A large selection of commercially available vegetable oils and marine omega-3 supplements was purchased from grocery stores, pharmacies, and health food stores in Norway. The content of lipid oxidation products were measured as peroxide value and alkenal concentration. Twelve different vegetable oils were heated for a temperature (225°C) and time (25 minutes) resembling conditions typically used during cooking. Results The peroxide values were in the range 1.04–10.38 meq/kg for omega-3 supplements and in the range 0.60–5.33 meq/kg for fresh vegetable oils. The concentration range of alkenals was 158.23–932.19 nmol/mL for omega-3 supplements and 33.24–119.04 nmol/mL for vegetable oils. After heating, a 2.9–11.2 fold increase in alkenal concentration was observed for vegetable oils. Conclusions The contents of hydroperoxides and alkenals in omega-3 supplements are higher than in vegetable oils. After heating vegetable oils, a large increase in alkenal concentration was observed. PMID:21691461

  12. Alcohol Selectivity in a Synthetic Thermophilic n-Butanol Pathway Is Driven by Biocatalytic and Thermostability Characteristics of Constituent Enzymes

    PubMed Central

    Loder, Andrew J.; Zeldes, Benjamin M.; Garrison, G. Dale; Lipscomb, Gina L.; Adams, Michael W. W.

    2015-01-01

    n-Butanol is generated as a natural product of metabolism by several microorganisms, but almost all grow at mesophilic temperatures. A synthetic pathway for n-butanol production from acetyl coenzyme A (acetyl-CoA) that functioned at 70°C was assembled in vitro from enzymes recruited from thermophilic bacteria to inform efforts for engineering butanol production into thermophilic hosts. Recombinant versions of eight thermophilic enzymes (β-ketothiolase [Thl], 3-hydroxybutyryl-CoA dehydrogenase [Hbd], and 3-hydroxybutyryl-CoA dehydratase [Crt] from Caldanaerobacter subterraneus subsp. tengcongensis; trans-2-enoyl-CoA reductase [Ter] from Spirochaeta thermophila; bifunctional acetaldehyde dehydrogenase/alcohol dehydrogenase [AdhE] from Clostridium thermocellum; and AdhE, aldehyde dehydrogenase [Bad], and butanol dehydrogenase [Bdh] from Thermoanaerobacter sp. strain X514) were utilized to examine three possible pathways for n-butanol. These pathways differed in the two steps required to convert butyryl-CoA to n-butanol: Thl-Hbd-Crt-Ter-AdhE (C. thermocellum), Thl-Hbd-Crt-Ter-AdhE (Thermoanaerobacter X514), and Thl-Hbd-Crt-Ter-Bad-Bdh. n-Butanol was produced at 70°C, but with different amounts of ethanol as a coproduct, because of the broad substrate specificities of AdhE, Bad, and Bdh. A reaction kinetics model, validated via comparison to in vitro experiments, was used to determine relative enzyme ratios needed to maximize n-butanol production. By using large relative amounts of Thl and Hbd and small amounts of Bad and Bdh, >70% conversion to n-butanol was observed in vitro, but with a 60% decrease in the predicted pathway flux. With more-selective hypothetical versions of Bad and Bdh, >70% conversion to n-butanol is predicted, with a 19% increase in pathway flux. Thus, more-selective thermophilic versions of Bad, Bdh, and AdhE are needed to fully exploit biocatalytic n-butanol production at elevated temperatures. PMID:26253677

  13. Chronic toxicity of a mixture of chlorinated alkanes and alkenes in ICR mice.

    PubMed

    Wang, Fun-In; Kuo, Min-Liang; Shun, Chia-Tung; Ma, Yee-Chung; Wang, Jung-Der; Ueng, Tzuu-Huei

    2002-02-01

    The aim of this study was to determine the chronic toxicity of a mixture of chlorinated alkanes and alkenes (CA) consisting of chloroform, 1,1-dichloroethane, 1,1-dichloroethylene, 1,1,1-trichloroethane, trichloroethylene, and tetrachloroethylene. These chlorinated organic solvents were present in the underground water near an electronic appliances manufactory in Taoyuan, Taiwan. Male and female weanling ICR mice were treated with low-, medium-, and high-dose CA mixtures in drinking water for 16 and 18 mo, respectively. A significant number of male mice treated with the high-dose CA mixture developed tail alopecia and deformation, which was not prominent in CA-treated female mice. Medium- and high-dose CA mixtures induced marginal increases of liver and lung weights, blood urea nitrogen, and serum creatinine levels in male mice. In female mice, the high-dose CA mixture increased liver, kidney, and uterus and ovary total weights, without affecting serum biochemistry parameters. CA mixtures had no effects on the total glutathione content or the level of glutathione S-transferase activity in the livers and kid- neys of male and female mice. Treatments with CA mixtures produced a trend of increasing frequency of hepatocelluar neoplasms in male mice, compared to male and female controls and CA-treated female mice. The high-dose CA mixture induced a significantly higher incidence of mammary adenocarcinoma in female mice. The calculated odds ratios of mammary adenocarcinoma in female mice induced by low-, medium-, and high-dose CA mixtures were 1.14, 1.37, and 3.53 times that of the controls, respectively. The low-dose CA mixture induced a higher incidence of cysts and inflammation in and around the ovaries. This study has demonstrated that the CA mixture is a potential carcinogen to male and female mice. These animal toxicology data may be important in assessing the health effects of individuals exposed to the CA mixture.

  14. Terminal Alkene Formation by the Thioesterase of Curacin A Biosynthesis: Structure of a Decarboxylating Thioesterase

    SciTech Connect

    Gehret, Jennifer J.; Gu, Liangcai; Gerwick, William H.; Wipf, Peter; Sherman, David H.; Smith, Janet L.

    2011-11-07

    Curacin A is a polyketide synthase (PKS)-non-ribosomal peptide synthetase-derived natural product with potent anticancer properties generated by the marine cyanobacterium Lyngbya majuscula. Type I modular PKS assembly lines typically employ a thioesterase (TE) domain to off-load carboxylic acid or macrolactone products from an adjacent acyl carrier protein (ACP) domain. In a striking departure from this scheme the curacin A PKS employs tandem sulfotransferase and TE domains to form a terminal alkene moiety. Sulfotransferase sulfonation of {beta}-hydroxy-acyl-ACP is followed by TE hydrolysis, decarboxylation, and sulfate elimination (Gu, L., Wang, B., Kulkarni, A., Gehret, J. J., Lloyd, K. R., Gerwick, L., Gerwick, W. H., Wipf, P., Hakansson, K., Smith, J. L., and Sherman, D. H. (2009) J. Am. Chem. Soc. 131, 16033-16035). With low sequence identity to other PKS TEs (<15%), the curacin TE represents a new thioesterase subfamily. The 1.7-{angstrom} curacin TE crystal structure reveals how the familiar {alpha}/{beta}-hydrolase architecture is adapted to specificity for {beta}-sulfated substrates. A Ser-His-Glu catalytic triad is centered in an open active site cleft between the core domain and a lid subdomain. Unlike TEs from other PKSs, the lid is fixed in an open conformation on one side by dimer contacts of a protruding helix and on the other side by an arginine anchor from the lid into the core. Adjacent to the catalytic triad, another arginine residue is positioned to recognize the substrate {beta}-sulfate group. The essential features of the curacin TE are conserved in sequences of five other putative bacterial ACP-ST-TE tridomains. Formation of a sulfate leaving group as a biosynthetic strategy to facilitate acyl chain decarboxylation is of potential value as a route to hydrocarbon biofuels.

  15. Photoreactions of biacetyl, benzophenone, and benzil with electron-rich alkenes

    SciTech Connect

    Gersdorf, J.; Mattay, J.; Goerner, H.

    1987-02-18

    The rate constants (k/sub q/) for fluorescence and phosphorescence quenching of biacetyl by electron-rich alkenes were measured in acetonitrile solution at room temperature. A weak dependence of log k/sub q/ on the free enthalpy change (..delta..G/sub 2/) for electron transfer in the triplet state in the range 0 < ..delta..G/sub 2/ < 1.0 eV indicates formation of a polar exciplex. The strong enhancement of k/sub q/ for 0 > ..delta..G/sub 2/ > -0.70 eV points to electron-transfer processes in singlet and triplet states. Quenching of the phosphorescence and the T-T absorption of benzophenone reveals larger (smaller) k/sub q/ values in the endergonic (exergonic) region, as compared to the Rehm-Weller correlation. The slope of the plot of log k/sub q/ vs. ..delta..G/sub 2/ is similar to that of biacetyl in the endergonic region. The latter indicates that electron transfer in this instance is not the primary step. For benzil the plot of log k/sub q/ vs ..delta..G/sub 2/ resembles more closely that of biacetyl, pointing to a similar mechanism. In the exergonic region electron transfer is observed for benzil (major process) and benzophenone (minor process) by detection of the radical anion with use of nanosecond laser flash photolysis. The yield and half-life of the radical anion depend on the nature of the electron donor and the ketone, the solvent polarity, and the additives (e.g., LiClO/sub 4/, special salt effect). The solvent effect on the photoproducts (oxetanes) is correlated with the free enthalpies of radical ion pair formation.

  16. Asymmetric ozone oxidation of silylalkenes using a C2-symmetrical dialkoxysilyl group as a chiral auxiliary.

    PubMed

    Igawa, Kazunobu; Kawasaki, Yuuya; Nishino, Kosuke; Mitsuda, Naoto; Tomooka, Katsuhiko

    2014-07-21

    Ozone oxidation of silyl-substituted alkenes, namely silylalkenes, proceeds in an addition-type manner to afford α-silylperoxy carbonyl compounds in good to excellent yields, without the formation of normal ozonolysis products. Herein the ozone oxidation of chiral alkenylsilanes prepared from alkynes and a newly designed chiral hydrosilane is reported. The reaction affords silylperoxides with high diastereoselectivity (up to 94 % d.r.). The silylperoxides are convertible into enantioenriched chiral acyloins in a stereospecific manner. PMID:24939819

  17. A highly catalytic and selective conversion of carboxylic acids to 1-alkenes of one less carbon atom

    SciTech Connect

    Miller, J.A.; Nelson, J.A.; Byrne, M.P. )

    1993-01-01

    An equimolar mixture of a carboxylic acid and acetic anhydride produces a reagent combination that undergoes a highly efficient decarbonylation/dehydration at 250[degrees]C using either Pd- or Rh-based catalyst systems, affording excellent yields of the corresponding 1-alkenes and one less carbon atom. The stoichiometric and catalytic decarbonylation of aliphatic aldehydes and acid chlorides to alkanes and alkenes, respectively, by transition-metal complexes are well-known and synthetically useful transformations. Relatively little, however, has been reported concerning the analogous decarbonylation/dehydration of aliphatic carboxylic acids to olefins, with generally poor results achieved in terms of catalyst efficiency and selectivity toward terminal olefin formation in the product. For example, the decarbonylation/dehydration of stearic acid to heptadecane using a Rh-based catalyst was reported to proceed with a maximum catalyst turnover number (TON; moles of olefin product formed per mole of catalyst used) of ca. 250, with selectivities toward 1-heptadecene formation typically below 50%. Interestingly, results were presented in this work which suggested that the decarbonylation of stearic acid proceeded via intermediate formation of stearic anhydride. Use of a preformed, symmetrical anhydride is not desirable from an economic or synthetic viewpoint, particularly since its decarbonylation should result in the formation of equal amounts of olefin and carboxylic acid coproducts. The authors now report here that the use of a carboxylic acid substrate as an equimolar mixture with acetic anhydride (Ac[sub 2]O) produces a mixed anhydride system which undergoes an extremely facile decarbonylation reaction to provide a general and highly selective route to the corresponding 1-alkenes of one less carbon atom. 19 refs., 1 tab.

  18. Binding Energy of d¹º Transition Metals to Alkenes By Wave Function Theory and Density Functional Theory

    SciTech Connect

    Averkiev, Boris B; Zhao, Yan; Truhlar, Donald G

    2010-06-01

    The structures of Pd(PH₃)₂ and Pt(PH₃)₂ complexes with ethene and conjugated CnHn+2 systems (n=4, 6, 8, and 10) were studied. Their binding energies were calculated using both wave function theory (WFT) and density functional theory (DFT). Previously it was reported that the binding energy of the alkene to the transition metal does not depend strongly on the size of the conjugated CnHn+2 ligand, but that DFT methods systematically underestimate the binding energy more and more significantly as the size of the conjugated system is increased. Our results show that recently developed density functionals predict the binding energy for these systems much more accurately. New benchmark calculations carried out by the coupled cluster method based on Brueckner orbitals with double excitations and a quasiperturbative treatment of connected triple excitations (BCCD(T)) with a very large basis set agree even better with the DFT predictions than do the previous best estimates. The mean unsigned error in absolute and relative binding energies of the alkene ligands to Pd(PH₃)₂ is 2.5 kcal/mol for the ωB97 and M06 density functionals and 2.9 kcal/mol for the M06-L functional. Adding molecular mechanical damped dispersion yields even smaller mean unsigned errors: 1.3 kcal/mol for the M06-D functional, 1.5 kcal/mol for M06- L-D, and 1.8 kcal/mol for B97-D and ωB97X-D. The new functionals also lead to improved accuracy for the analogous Pt complexes. These results show that recently developed density functionals may be very useful for studying catalytic systems involving Pd d¹º centers and alkenes.

  19. Protection against Photooxidative Injury of Tobacco Leaves by 2-Alkenal Reductase. Detoxication of Lipid Peroxide-Derived Reactive Carbonyls1

    PubMed Central

    Mano, Jun'ichi; Belles-Boix, Enric; Babiychuk, Elena; Inzé, Dirk; Torii, Yoshimitsu; Hiraoka, Eiji; Takimoto, Koichi; Slooten, Luit; Asada, Kozi; Kushnir, Sergei

    2005-01-01

    Degradation of lipid peroxides leads to the formation of cytotoxic 2-alkenals and oxenes (collectively designated reactive carbonyls). The novel NADPH-dependent oxidoreductase 2-alkenal reductase (AER; EC 1.3.1.74) from Arabidopsis (Arabidopsis thaliana), which is encoded by the gene At5g16970, catalyzes the reduction of the α,β-unsaturated bond of reactive carbonyls, and hence is presumed to function in antioxidative defense in plants. Here we show that Arabidopsis AER (At-AER) has a broad substrate spectrum to biologically relevant reactive carbonyls. Besides 2-alkenals, the enzyme recognized as substrates the lipid peroxide-derived oxenes 9-oxo-octadeca-(10E),(12Z)-dienoic acid and 13-oxo-octadeca-(9E),(11Z)-dienoic acid, as well as the potent genotoxin 4-oxo-(2E)-nonenal, altogether suggesting AER has a key role in the detoxification of reactive carbonyls. To validate this conclusion by in vivo studies, transgenic tobacco (Nicotiana tabacum) plants that had 100- to 250-fold higher AER activity levels than control plants were generated. The engineered plants exhibited significantly less damage from either (1) the exogenously administered 4-hydroxy-(2E)-nonenal, (2) treatment with methyl viologen plus light, or (3) intense light. We further show that the At-AER protein fused with the Aequorea victoria green fluorescent protein localizes in cytosol and the nucleus in Bright-Yellow 2 cells. These results indicate that reactive carbonyls mediate photooxidative injury in leaf cells, and At-AER in the cytosol protects the cells by reducing the α,β-unsaturated bond of the photoproduced reactive carbonyls. PMID:16299173

  20. Formation of alkenes via degradation of tert-alkyl ethers and alcohols by Aquincola tertiaricarbonis L108 and Methylibium spp.

    PubMed

    Schäfer, Franziska; Muzica, Liudmila; Schuster, Judith; Treuter, Naemi; Rosell, Mònica; Harms, Hauke; Müller, Roland H; Rohwerder, Thore

    2011-09-01

    Bacterial degradation pathways of fuel oxygenates such as methyl tert-butyl and tert-amyl methyl ether (MTBE and TAME, respectively) have already been studied in some detail. However, many of the involved enzymes are still unknown, and possible side reactions have not yet been considered. In Aquincola tertiaricarbonis L108, Methylibium petroleiphilum PM1, and Methylibium sp. strain R8, we have now detected volatile hydrocarbons as by-products of the degradation of the tert-alkyl ether metabolites tert-butyl and tert-amyl alcohol (TBA and TAA, respectively). The alkene isobutene was formed only during TBA catabolism, while the beta and gamma isomers of isoamylene were produced only during TAA conversion. Both tert-alkyl alcohol degradation and alkene production were strictly oxygen dependent. However, the relative contribution of the dehydration reaction to total alcohol conversion increased with decreasing oxygen concentrations. In resting-cell experiments where the headspace oxygen content was adjusted to less than 2%, more than 50% of the TAA was converted to isoamylene. Isobutene formation from TBA was about 20-fold lower, reaching up to 4% alcohol turnover at low oxygen concentrations. It is likely that the putative tert-alkyl alcohol monooxygenase MdpJ, belonging to the Rieske nonheme mononuclear iron enzymes and found in all three strains tested, or an associated enzymatic step catalyzed the unusual elimination reaction. This was also supported by the detection of mdpJK genes in MTBE-degrading and isobutene-emitting enrichment cultures obtained from two treatment ponds operating at Leuna, Germany. The possible use of alkene formation as an easy-to-measure indicator of aerobic fuel oxygenate biodegradation in contaminated aquifers is discussed. PMID:21742915

  1. Integrated lipase production and in situ biodiesel synthesis in a recombinant Pichia pastoris yeast: an efficient dual biocatalytic system composed of cell free enzymes and whole cell catalysts

    PubMed Central

    2014-01-01

    Background Lipase-catalyzed biotransformation of acylglycerides or fatty acids into biodiesel via immobilized enzymes or whole cell catalysts has been considered as one of the most promising methods to produce renewable and environmentally friendly alternative liquid fuels, thus being extensively studied so far. In all previously pursued approaches, however, lipase enzymes are prepared in an independent process separated from enzymatic biodiesel production, which would unavoidably increase the cost and energy consumption during industrial manufacture of this cost-sensitive energy product. Therefore, there is an urgent need to develop novel cost-effective biocatalysts and biocatalytic processes with genuine industrial feasibility. Result Inspired by the consolidated bioprocessing of lignocellulose to generate bioethanol, an integrated process with coupled lipase production and in situ biodiesel synthesis in a recombinant P. pastoris yeast was developed in this study. The novel and efficient dual biocatalytic system based on Thermomyces lanuginosus lipase took advantage of both cell free enzymes and whole cell catalysts. The extracellular and intracellular lipases of growing yeast cells were simultaneously utilized to produce biodiesel from waste cooking oils in situ and in one pot. This integrated system effectively achieved 58% and 72% biodiesel yield via concurrent esterified-transesterified methanolysis and stepwise hydrolysis-esterification at 3:1 molar ratio between methanol and waste cooking oils, respectively. Further increasing the molar ratio of methanol to waste cooking oils to 6:1 led to an 87% biodiesel yield using the stepwise strategy. Both water tolerance and methanol tolerance of this novel system were found to be significantly improved compared to previous non-integrated biodiesel production processes using separately prepared immobilized enzymes or whole cell catalysts. Conclusion We have proposed a new concept of integrated biodiesel production

  2. Organosulfate Formation through the Heterogeneous Reaction of Sulfur Dioxide with Unsaturated Fatty Acids and Long-Chain Alkenes.

    PubMed

    Passananti, Monica; Kong, Lingdong; Shang, Jing; Dupart, Yoan; Perrier, Sébastien; Chen, Jianmin; Donaldson, D James; George, Christian

    2016-08-22

    The heterogeneous reaction between SO2 and unsaturated compounds results in the efficient production of organosulfates for several fatty acids and long-chain alkenes. The presence of an acid group, the physical state of the reactants (solid or liquid), the nature of the double bond (cis, trans, terminal), and the use of light irradiation all have an impact on the reaction rate. The reaction was investigated using different set-ups (coated flow tube, aerosol flow tube, and diffuse reflectance infrared Fourier transform cell). The reaction products were identified by high-resolution mass spectrometry and the impact of this reaction on organosulfate formation in the atmosphere is discussed.

  3. Organosulfate Formation through the Heterogeneous Reaction of Sulfur Dioxide with Unsaturated Fatty Acids and Long-Chain Alkenes.

    PubMed

    Passananti, Monica; Kong, Lingdong; Shang, Jing; Dupart, Yoan; Perrier, Sébastien; Chen, Jianmin; Donaldson, D James; George, Christian

    2016-08-22

    The heterogeneous reaction between SO2 and unsaturated compounds results in the efficient production of organosulfates for several fatty acids and long-chain alkenes. The presence of an acid group, the physical state of the reactants (solid or liquid), the nature of the double bond (cis, trans, terminal), and the use of light irradiation all have an impact on the reaction rate. The reaction was investigated using different set-ups (coated flow tube, aerosol flow tube, and diffuse reflectance infrared Fourier transform cell). The reaction products were identified by high-resolution mass spectrometry and the impact of this reaction on organosulfate formation in the atmosphere is discussed. PMID:27458109

  4. Five-membered cyclic metal carbyne: synthesis of osmapentalynes by the reactions of osmapentalene with allene, alkyne, and alkene.

    PubMed

    Zhu, Congqing; Yang, Yuhui; Wu, Jingjing; Luo, Ming; Fan, Jinglan; Zhu, Jun; Xia, Haiping

    2015-06-01

    The synthesis of small cyclic metal carbynes is challenging due to the large angle strain associated with the highly distorted nonlinear triple bonds. Herein, we report a general route for the synthesis of five-membered cyclic metal carbyne complexes, osmapentalynes, by the reactions of an osmapentalene derivative with allene, alkyne, and alkene. Experimental observations and theoretical calculations document the aromaticity in the fused five-membered rings of osmapentalynes. The realization of transforming osmapentalene to osmapentalyne through this general route would not only allow further exploration of metallapentalyne chemistry but also show promising applications of this novel aromatic system with broad absorption band and high molar absorption coefficient. PMID:25917530

  5. Conjugate Addition of 3-Buytn-2-one to Anilines in Ethanol: Alkene Geometric Insights through In Situ FTIR Monitoring.

    PubMed

    Chisholm, David R; Valentine, Roy; Pohl, Ehmke; Whiting, Andrew

    2016-09-01

    A convenient, mild and effective conjugate addition of 3-butyn-2-one to a variety of anilines in ethanol is reported. The reaction was monitored and characterized through in situ FTIR, and the dynamics of the facile E/Z alkene geometry interconversion of the resultant aniline-derived enaminones was explored through NMR, FTIR and X-ray crystallography. A straightforward purification protocol that employs direct Kugelrohr distillation was identified, and the method was further extended to other amines and ynones, allowing rapid access to these interesting compounds. PMID:27467234

  6. Palladium-Catalyzed 1,3-Difunctionalization Using Terminal Alkenes with Alkenyl Nonaflates and Aryl Boronic Acids.

    PubMed

    McCammant, Matthew S; Shigeta, Takashi; Sigman, Matthew S

    2016-04-15

    A Pd-catalyzed 1,3-difunctionalization of terminal alkenes using 1,1-disubstituted alkenyl nonaflates and arylboronic acid coupling partners is reported. This transformation affords allylic arene products that are difficult to selectively access using traditional Heck cross-coupling methodologies. The evaluation of seldom employed 1,1-disubstituted alkenyl nonaflate coupling partners led to the elucidation of subtle mechanistic features of π-allyl stabilized Pd-intermediates. Good stereo- and regioselectivity for the formation of 1,3-addition products can be accessed through a minimization of steric interactions that emanate from alkenyl nonaflate substitution.

  7. Brønsted Acid Catalyzed Asymmetric Hydroamination of Alkenes: Synthesis of Pyrrolidines Bearing a Tetrasubstituted Carbon Stereocenter.

    PubMed

    Lin, Jin-Shun; Yu, Peng; Huang, Lin; Zhang, Pan; Tan, Bin; Liu, Xin-Yuan

    2015-06-26

    The first highly enantioselective Brønsted acid catalyzed intramolecular hydroamination of alkenes enables the efficient construction of a series of chiral (spirocyclic) pyrrolidines with an α-tetrasubstituted carbon stereocenter with excellent functional group tolerance. A unique feature of this strategy is the use of a thiourea group acting as both the activating and the directing group through cooperative multiple hydrogen bonding with a Brønsted acid and the double bond. The utility of this method is highlighted by the facile construction of chiral synthetic intermediates and important structural motifs that are widely found in organic synthesis.

  8. Pd(II)-Catalyzed Aminofluorination of Alkenes in Total Synthesis 6-(R)-Fluoroswainsonine and 5-(R)-Fluorofebrifugine.

    PubMed

    Wu, Liang; Chen, Pinhong; Liu, Guosheng

    2016-03-01

    The total syntheses of two fluorinated alkaloids, 6-(R)-fluoroswainsonine and 5-(R)-fluorofebrifugine, are described. Both encompass (4aS,7R,8aR)-7-fluoro-5-tosylhexahydro-4H-[1,3]dioxino[5,4-b]pyridine as a key synthon which is obtained through a further optimized palladium-catalyzed aminofluorination of alkenes with high diastereoselectivity. 6-(R)-Fluoroswainsonine is synthesized from the key synthon in 14 steps, and 5-(R)-fluorofebrifugine requires a sequential 15-step transformation.

  9. Rhodium-Catalyzed Stereoselective Intramolecular [5 + 2] Cy-cloaddition of 3-Acyloxy-1,4-enyne and Alkene

    PubMed Central

    Shu, Xing-zhong; Schienebeck, Casi M.; Li, Xiaoxun; Zhou, Xin; Song, Wangze; Chen, Lianqing; Guzei, Ilia A.; Tang, Weiping

    2015-01-01

    The first rhodium-catalyzed intramolecular [5 + 2] cycloaddition of 3-acyloxy-1,4-enyne and alkene was developed. The cycloaddition is highly diastereoselective in most cases. Various cis-fused bicyclo[5.3.0]decadienes were prepared stereoselectively. The chirality in the propargylic ester starting materials could be transferred to the bicyclic products with high efficiency. Electron-deficient phosphine ligand greatly facilitated the cycloaddition. Up to three new stereogenic centers could be generated. The resulting diene in the products could be hydrolyzed to enones, which allowed the introduction of more functional groups to the seven-membered ring. PMID:26440751

  10. Three-dimensional topographic index applied to the prediction of acyclic C5-C8 alkenes Kováts retention indices on polydimethylsiloxane and squalane columns.

    PubMed

    Ren, Yueying; Liu, Huanxiang; Yao, Xiaojun; Liu, Mancang

    2007-06-29

    A novel approach is described for the prediction of gas chromatographic Kováts retention indices of 150 acyclic C5-C8 alkenes on two stationary phases (polydimethylsiloxane, PDMS, and squalane, SQ). The heuristic method was used to build multiple linear regression models using descriptors calculated by MODLESLAB software and CODESSA program. The resulting quantitative structure-retention relationship (QSRR) models were well-correlated, with predictive R2 values of 0.970 and 0.958 for retention indices on PDMS and SQ columns, respectively. 1Omegap, a three-dimensional (3D) topographic index, was found to play the most important role in the description of the chromatographic retention behavior of the alkenes in these two stationary phases. Moreover, this index could completely distinguish different isomers of alkene. Therefore, it can also be extended to distinguish different isomers of other compounds so that can well describe their quantitative structure-retention relationships.

  11. Partial oxidation of {alpha}-olefins over iron antimony oxide - influence of carbon number

    SciTech Connect

    Steen, E. van; Schnobel, M.; O`Connor, C.T.

    1996-10-01

    Iron antimony oxide is a well known catalyst for the partial oxidation of propane and 1-butene. Kinetic studies of the partial oxidation of {alpha}-olefins (C{sub 2}-C{sub 9}) revealed that the activity showed a maximum at C{sub 4}. The main products of the partial oxidation of {alpha}-olefins (larger than C{sub 2}) are the conjugated alkenal (acrolein) and dienes. The selectivity to these desired products decreases with increasing chain length probably caused by both the decrease in number of allylic hydrogen atoms and the shielding of them. Ethene could only be oxidized at relatively high temperatures (over 450{degrees}C) and the only observed products were CO and CO{sub 2} indicating the need for the presence of allylic hydrogen for low temperature selective partial oxidation. Increasing the carbon number increases the yield of CO and CO{sub 2} due to shielding of the allylic hydrogen.

  12. Cycloaddition Reaction of Vinylphenylfurans and Dimethyl Acetylenedicarboxylate to [8 + 2] Isomers via Tandem [4 + 2]/Diradical Alkene-Alkene Coupling/[1,3]-H Shift Reactions: Experimental Exploration and DFT Understanding of Reaction Mechanisms.

    PubMed

    Chen, Kai; Wu, Feng; Ye, Lijuan; Tian, Zi-You; Yu, Zhi-Xiang; Zhu, Shifa

    2016-09-16

    An experimental test of designed [8 + 2] reaction of vinylphenylfuran and dimethyl acetylenedicarboxylate (DMAD) has been carried out, showing that the reaction gave unexpected addition products under different conditions. When the reaction was conducted under thermal conditions in toluene, expoxyphenanthrene, which was named as a [8 + 2] isomer, was generated. The scope of this reaction has been investigated in the present study. In addition, experiments and DFT calculations have been conducted to investigate how the reaction between vinylphenylfuran and DMAD took place. Surprisingly, the reaction did not involve the expected [8 + 2] intermediate, o-quinodimethane. Instead, the reaction starts from intermolecular Diels-Alder reactions between DMAD and the furan moiety of vinylphenylfuran, followed by unexpected intramolecular alkene-alkene coupling. This step generates a diradical species, which then undergoes [1,3]-H shift to give the experimentally observed expoxyphenanthrene. DFT calculations revealed that, the [8 + 2] cycloadduct cannot be obtained because the [1,5]-H shift process from the [1,5]-vinyl shift intermediate is disfavored kinetically compared to the [1,3]-H shift to the [8 + 2] isomer.

  13. Cycloaddition Reaction of Vinylphenylfurans and Dimethyl Acetylenedicarboxylate to [8 + 2] Isomers via Tandem [4 + 2]/Diradical Alkene-Alkene Coupling/[1,3]-H Shift Reactions: Experimental Exploration and DFT Understanding of Reaction Mechanisms.

    PubMed

    Chen, Kai; Wu, Feng; Ye, Lijuan; Tian, Zi-You; Yu, Zhi-Xiang; Zhu, Shifa

    2016-09-16

    An experimental test of designed [8 + 2] reaction of vinylphenylfuran and dimethyl acetylenedicarboxylate (DMAD) has been carried out, showing that the reaction gave unexpected addition products under different conditions. When the reaction was conducted under thermal conditions in toluene, expoxyphenanthrene, which was named as a [8 + 2] isomer, was generated. The scope of this reaction has been investigated in the present study. In addition, experiments and DFT calculations have been conducted to investigate how the reaction between vinylphenylfuran and DMAD took place. Surprisingly, the reaction did not involve the expected [8 + 2] intermediate, o-quinodimethane. Instead, the reaction starts from intermolecular Diels-Alder reactions between DMAD and the furan moiety of vinylphenylfuran, followed by unexpected intramolecular alkene-alkene coupling. This step generates a diradical species, which then undergoes [1,3]-H shift to give the experimentally observed expoxyphenanthrene. DFT calculations revealed that, the [8 + 2] cycloadduct cannot be obtained because the [1,5]-H shift process from the [1,5]-vinyl shift intermediate is disfavored kinetically compared to the [1,3]-H shift to the [8 + 2] isomer. PMID:27541179

  14. Biocatalytic preparation and absolute configuration of enantiomerically pure fungistatic anti-2-benzylindane derivatives. Study of the detoxification mechanism by Botrytis cinerea.

    PubMed

    Pinedo-Rivilla, Cristina; Aleu, Josefina; Grande Benito, Manuel; Collado, Isidro G

    2010-08-21

    Enantiomerically pure 2-benzylindane derivatives were prepared using biocatalytic methods and their absolute configuration determined. (1R,2S)-2-Benzylindan-1-ol ((1R,2S)-2) and (S)-2-benzylindan-1-one ((S)-3) were produced by fermenting baker's yeast. Lipase-mediated esterifications and hydrolysis of the corresponding racemic substrates gave rise to the enantiopure compounds (1S,2R)-2-benzylindan-1-ol ((1S,2R)-2) and (1R,2S)-2-benzylindan-1-ol ((1R,2S)-2), respectively. The antifungal activity of these products against two strains of the plant pathogen Botrytis cinerea was tested. The metabolism of anti-(+/-)-2-benzylindan-1-ol (anti-(+/-)-2) by B. cinerea as part of the fungal detoxification mechanism is also described and revealed interesting differences in the genome of both strains.

  15. Tetrahydroxydiboron-Mediated Palladium-Catalyzed Transfer Hydrogenation and Deuteriation of Alkenes and Alkynes Using Water as the Stoichiometric H or D Atom Donor.

    PubMed

    Cummings, Steven P; Le, Thanh-Ngoc; Fernandez, Gilberto E; Quiambao, Lorenzo G; Stokes, Benjamin J

    2016-05-18

    There are few examples of catalytic transfer hydrogenations of simple alkenes and alkynes that use water as a stoichiometric H or D atom donor. We have found that diboron reagents efficiently mediate the transfer of H or D atoms from water directly onto unsaturated C-C bonds using a palladium catalyst. This reaction is conducted on a broad variety of alkenes and alkynes at ambient temperature, and boric acid is the sole byproduct. Mechanistic experiments suggest that this reaction is made possible by a hydrogen atom transfer from water that generates a Pd-hydride intermediate. Importantly, complete deuterium incorporation from stoichiometric D2O has also been achieved. PMID:27135185

  16. Remarkable steric effect in palladium-catalyzed Grignard coupling: region- and stereoselective monoalkylation and -arylation of 1,1-dichloro-1-alkenes

    SciTech Connect

    Minato, A.; Suzuki, K.; Tamao, K.

    1987-02-18

    Functionalized carbon chain elongation has been a central concern in transition-metal complex catalyzed carbon-carbon bond-forming reactions. As part of their continued studies on the palladium-phosphine complex catalyzed selective monoalkylation of organic polyhalides, they report here the first success in the regio- and stereoselective monoalkylation and -arylation of 1,1-dichloro-1-alkenes by Grignard or organozinc reagents in the presence of (PdCl/sub 2/(dppb)), dppb = Ph/sub 2/P(CH/sub 2/)/sub 4/PPh/sub 2/, as a catalyst to produce 1-substituted (Z)-1-chloro-1-alkenes.

  17. Anti-Markovnikov hydroheteroarylation of unactivated alkenes with indoles, pyrroles, benzofurans, and furans catalyzed by a nickel-N-heterocyclic carbene system.

    PubMed

    Schramm, York; Takeuchi, Makoto; Semba, Kazuhiko; Nakao, Yoshiaki; Hartwig, John F

    2015-09-30

    We report the catalytic addition of C-H bonds at the C2 position of heteroarenes, including pyrroles, indoles, benzofurans, and furans, to unactivated terminal and internal alkenes. The reaction is catalyzed by a combination of Ni(COD)2 and a sterically hindered, electron-rich N-heterocyclic carbene ligand or its analogous Ni(NHC)(arene) complex. The reaction is highly selective for anti-Markovnikov addition to α-olefins, as well as for the formation of linear alkylheteroarenes from internal alkenes. The reaction occurs with substrates containing ketones, esters, amides, boronate esters, silyl ethers, sulfonamides, acetals, and free amines. PMID:26334367

  18. Anti-Markovnikov hydroheteroarylation of unactivated alkenes with indoles, pyrroles, benzofurans, and furans catalyzed by a nickel-N-heterocyclic carbene system.

    PubMed

    Schramm, York; Takeuchi, Makoto; Semba, Kazuhiko; Nakao, Yoshiaki; Hartwig, John F

    2015-09-30

    We report the catalytic addition of C-H bonds at the C2 position of heteroarenes, including pyrroles, indoles, benzofurans, and furans, to unactivated terminal and internal alkenes. The reaction is catalyzed by a combination of Ni(COD)2 and a sterically hindered, electron-rich N-heterocyclic carbene ligand or its analogous Ni(NHC)(arene) complex. The reaction is highly selective for anti-Markovnikov addition to α-olefins, as well as for the formation of linear alkylheteroarenes from internal alkenes. The reaction occurs with substrates containing ketones, esters, amides, boronate esters, silyl ethers, sulfonamides, acetals, and free amines.

  19. Solvent Stability Study with Thermodynamic Analysis and Superior Biocatalytic Activity of Burkholderia cepacia Lipase Immobilized on Biocompatible Hybrid Matrix of Poly(vinyl alcohol) and Hypromellose.

    PubMed

    Badgujar, Kirtikumar C; Bhanage, Bhalchandra M

    2014-12-26

    In the present study, we have synthesized a biocompatible hybrid carrier of hypromellose (HY) and poly(vinyl alcohol) (PVA) for immobilization of Burkholderia cepacia lipase (BCL). The immobilized biocatalyst HY:PVA:BCL was subjected to determination of half-life time (τ) and deactivation rate constant (K(D)) in various organic solvents. Biocatalyst showed higher τ-value in a nonpolar solvent like cyclohexane (822 h) as compared to that of a polar solvent such as acetone (347 h), which signifies better compatibility of biocatalyst in the nonpolar solvents. Furthermore, the K(D)-value was found to be less in cyclohexane (0.843 × 10(-3)) as compared to acetone (1.997 × 10(-3)), indicating better stability in the nonpolar solvents. Immobilized-BCL (35 mg) was sufficient to achieve 99% conversion of phenethyl butyrate (natural constituent of essential oils and has wide industrial applications) using phenethyl alcohol (2 mmol) and vinyl butyrate (6 mmol) at 44 °C in 3 h. The activation energy (E(a)) was found to be lower for immobilized-BCL than crude-BCL, indicating better catalytic efficiency of immobilized lipase BCL. The immobilized-BCL reported 6-fold superior biocatalytic activity and 8 times recyclability as compared to crude-BCL. Improved catalytic activity of immobilized enzyme in nonpolar media was also supported by thermodynamic activation parameters such as enthalpy (ΔH(⧧)), entropy (ΔS(⧧)) and Gibb's free energy (ΔG(⧧)) study, which showed that phenethyl butyrate synthesis catalyzed by immobilized-BCL was feasible as compared to crude-BCL. The present work explains a thermodynamic investigation and superior biocatalytic activity for phenethyl butyrate synthesis using biocompatible immobilized HY:PVA:BCL in nonaqueous media for the first time. PMID:25474503

  20. Photooxygenation of allylic alcohols: kinetic comparison of unfunctionalized alkenes with prenol-type allylic alcohols, ethers and acetates.

    PubMed

    Griesbeck, Axel G; Adam, Waldemar; Bartoschek, Anna; El-Idreesy, Tamer T

    2003-08-01

    The kinetics of the chemical and physical quenching of the first excited singlet state of oxygen [1O2 (1delta(g))] by unfunctionalized alkenes 1-4, allylic alcohols 5-7 and 9, allylic acetates 8 and 11, and the allylic ether 10 display small solvent-polarity effects on the reactivity. The regioselectivity of the singlet oxygen ene reaction is solvent independent for the unfunctionalized alkenes as well as the prenol-type substrates, the latter showing substantial solvent effects on the diastereoselectivity. Pronounced physical quenching is detected only for the allylic alcohols 5 and 6. These results are interpreted in terms of the interactions between singlet oxygen and the allylic hydroxy groups, conformationally promoted by allylic strain which lead either to chemical activation or to physical quenching. The results for substrate 9 in deuterated v.s non-deuterated methanol are in accord with hydrogen bonding between the allylic alcohol and 1O2, which directs the diastereoselectivity of the ene reaction with chiral allylic alcohols.

  1. Size-Dependent Catalytic Activity of Palladium Nanoparticles Fabricated in Porous Organic Polymers for Alkene Hydrogenation at Room Temperature.

    PubMed

    Mondal, John; Trinh, Quang Thang; Jana, Avijit; Ng, Wilson Kwok Hung; Borah, Parijat; Hirao, Hajime; Zhao, Yanli

    2016-06-22

    Ultrafine palladium nanoparticles (Pd NPs) with 8 and 3 nm sizes were effectively fabricated in triazine functionalized porous organic polymer (POP) TRIA that was developed by nonaqueous polymerization of 2,4,6-triallyoxy-1,3,5-triazine. The Pd NPs encapsulated POP (Pd-POP) was fully characterized using several techniques. Further studies revealed an excellent capability of Pd-POP for catalytic transfer hydrogenation of alkenes at room temperature with superior catalytic performance and high selectivity of desired products. Highly flammable H2 gas balloon at high pressure and temperature used in conventional hydrogenation reactions was not needed in the present synthetic system. Catalytic activity is strongly dependent on the size of encapsulated Pd NPs in the POP. The Pd-POP catalyst with Pd NPs of 8 nm in diameter exhibited higher catalytic activity for alkene hydrogenation as compared with the Pd-POP catalyst encapsulating 3 nm Pd NPs. Computational studies were undertaken to gain insights into different catalytic activities of these two Pd-POP catalysts. High reusability and stability as well as no Pd leaching of these Pd-POP catalysts make them highly applicable for hydrogenation reactions at room temperature. PMID:27258184

  2. Catalytic conversion of alcohols. 28. Product selectivities for 2-methylcyclohexanol conversion with metal oxide catalysts

    SciTech Connect

    Dabbagh, H.A.; Hughes, C.G.; Davis, B.H. )

    1992-02-01

    Metal oxides exhibit a range of selectivities (dehydration percentage, alkene distribution and alcohol isomerization) for the conversion of a 2-methylcyclohexanol isomer. For many metal oxide catalysts, trans-2-methylcyclohexanol produces a predominance of the less stable 3-methylcyclohexene isomer. The grouping of metal oxides based on the production of the less stable alkene isomers from 2-octanol is similar to that for trans-2-methlycyclohexanol. It is proposed that the same catalytic properties determine the selectivity for both reactants: for smaller metal cations the product selectivity is determined by steric crowding in the transition state, and for the larger cations the product selectivity is determined by the basicity of the oxygen anion and the relative acidity of the {beta}-hydrogens that are eliminated to produce water.

  3. Palladium-catalyzed oxidative arylalkylation of activated alkenes: dual C-H bond cleavage of an arene and acetonitrile.

    PubMed

    Wu, Tao; Mu, Xin; Liu, Guosheng

    2011-12-23

    Not one but two: The title reaction proceeds through the dual C-H bond cleavage of both aniline and acetonitrile. The reaction affords a variety of cyano-bearing indolinones in excellent yield. Mechanistic studies demonstrate that this reaction involves a fast arylation of the olefin and a rate-determining C-H activation of the acetonitrile.

  4. Oligomer formation during gas-phase ozonolysis of small alkenes and enol ethers: new evidence for the central role of the Criegee Intermediate as oligomer chain unit

    NASA Astrophysics Data System (ADS)

    Sadezky, A.; Winterhalter, R.; Kanawati, B.; Römpp, A.; Spengler, B.; Mellouki, A.; Le Bras, G.; Chaimbault, P.; Moortgat, G. K.

    2008-05-01

    An important fraction of secondary organic aerosol (SOA) formed by atmospheric oxidation of diverse volatile organic compounds (VOC) has recently been shown to consist of high-molecular weight oligomeric species. In our previous study (Sadezky et al., 2006), we reported the identification and characterization of oligomers as main constituents of SOA from gas-phase ozonolysis of small enol ethers. These oligomers contained repeated chain units of the same chemical composition as the main Criegee Intermediates (CI) formed during the ozonolysis reaction, which were CH2O2 (mass 46) for alkyl vinyl ethers (AVE) and C2H4O2 (mass 60) for ethyl propenyl ether (EPE). In the present work, we extend our previous study to another enol ether (ethyl butenyl ether EBE) and a variety of structurally related small alkenes (trans-3-hexene, trans-4-octene and 2,3-dimethyl-2-butene). Experiments have been carried out in a 570 l spherical glass reactor at atmospheric conditions in the absence of seed aerosol. SOA formation was measured by a scanning mobility particle sizer (SMPS). SOA filter samples were collected and chemically characterized off-line by ESI(+)/TOF MS and ESI(+)/TOF MS/MS, and elemental compositions were determined by ESI(+)/FTICR MS and ESI(+)/FTICR MS/MS. The results for all investigated unsaturated compounds are in excellent agreement with the observations of our previous study. Analysis of the collected SOA filter samples reveal the presence of oligomeric compounds in the mass range 200 to 800 u as major constituents. The repeated chain units of these oligomers are shown to systematically have the same chemical composition as the respective main Criegee Intermediate (CI) formed during ozonolysis of the unsaturated compounds, which is C3H6O2 (mass 74) for ethyl butenyl ether (EBE), trans-3-hexene, and 2,3-dimethyl-2-butene, and C4H8O2 (mass 88) for trans-4-octene. Analogous fragmentation pathways among the oligomers formed by gas-phase ozonolysis of the different

  5. Oligomer formation during gas-phase ozonolysis of small alkenes and enol ethers: new evidence for the central role of the Criegee Intermediate as oligomer chain unit

    NASA Astrophysics Data System (ADS)

    Sadezky, A.; Winterhalter, R.; Kanawati, B.; Römpp, A.; Spengler, B.; Mellouki, A.; Le Bras, G.; Chaimbault, P.; Moortgat, G. K.

    2007-10-01

    An important fraction of secondary organic aerosol (SOA) formed by atmospheric oxidation of diverse volatile organic compounds (VOC) has recently been shown to consist of high-molecular weight oligomeric species. In our previous study (Sadezky et al., 2006), we reported the identification and characterization of oligomers as main constituents of SOA from gas-phase ozonolysis of small enol ethers. These oligomers contained repeated chain units of the same chemical composition as the main Criegee Intermediates (CI) formed during the ozonolysis reaction, which were CH2O2 (mass 46) for alkyl vinyl ethers (AVE) and C2H4O2 (mass 60) for ethyl propenyl ether (EPE). In the present work, we extend our previous study (Sadezky et al., 2006) to another enol ether (ethyl butenyl ether EBE) and a variety of structurally related small alkenes (trans-3-hexene, trans-4-octene and 2,3-dimethyl-2-butene). Experiments have been carried out in a 570 l spherical glass reactor at atmospheric conditions in the absence of seed aerosol. SOA formation was measured by a scanning mobility particle sizer (SMPS). SOA filter samples were collected and chemically characterized off-line by ESI(+)/MS-TOF and ESI(+)/MS/MS-TOF, and elemental compositions were confirmed by ESI(+)/MS/MS-FTICR. The results for all investigated unsaturated compounds are in excellent agreement with the observations of our previous study (Sadezky et al., 2006). Analysis of the collected SOA filter samples reveal the presence of oligomeric compounds in the mass range 200 to 800 u as major constituents. The repeated chain units of these oligomers are shown to systematically have the same chemical composition as the respective main Criegee Intermediate (CI) formed during ozonolysis of the unsaturated compounds, which is C3H6O2 (mass 74) for ethyl butenyl ether (EBE), trans-3-hexene, and 2,3-dimethyl-2-butene, and C4H8O2 (mass 88) for trans-4-octene. Analogous fragmentation pathways among the oligomers formed by gas

  6. THE BIOCATALYTIC DESULFURIZATION PROJECT

    SciTech Connect

    Scott Collins; David Nunn

    2003-10-01

    The analysis of Petro Star diesel sulfur species is complete and a report is attached. Further analytical efforts will concentrate on characterization of diesel fuel, hydrodesulfurized to varying degrees, in order to determine sulfur species that may be problematic to hydrogen treatment and represent potential target substrates for biodesulfurization in a combined HDS-BDS process. Quotes have been received and are being considered for the partial treatment of Petro Star Inc. marine diesel fuel. Direction of research is changing slightly; economic analysis of the hyphenated--BDSHDS, BDS-CED--has shown the highest probability of success to be with a BDS-HDS process where the biodesulfurization precedes hydrodesulfurization. Thus, the microorganisms will be tailored to focus on those compounds that tend to be recalcitrant to hydrodesulfurization and decrease the severity of the hydrodesulfurization step. A separate, detailed justification for this change is being prepared. Research activities have continued in the characterization of the desulfurization enzymes from multiple sources. Genes for all DszA, -B, -C and -D enzymes (and homologs) have been cloned and expressed. Activity determinations, on a variety of substituted benzothiophene and dibenzothiophene substrates, have been carried out and continue. In addition, chemical synthesis efforts have been carried out to generate additional substrates for analytical standards and activity determinations. The generation of a GSSM mutant library of the ''Rhodococcus IGTS8 dszA'' gene has been completed and development of protocols for a high throughput screen to expand substrate specificity are nearing completion. In an effort to obtain improved hosts as biocatalyst, one hundred-thirty ''Rhodococcus'' and related strains are being evaluated for growth characteristics and other criteria deemed important for an optimal biocatalyst strain. We have also begun an effort to generate derivatives of the entire IGTS8 BDS plasmid that will allow for its easy transfer and manipulation into a variety of hosts. To support this activity and to gain an understanding of additional genes that may potentially affect BDS activity, the nucleotide sequence of the entire complement of plasmids in IGTS8 is being determined. Lastly, we continue to develop genetic screens and selections for the discovery and improvement of the biodesulfurization genes and strains.

  7. Biocatalytic Single Enzyme Nanoparticles

    SciTech Connect

    Grate, Jay W.; Kim, Jungbae

    2004-03-31

    As an innovative way of enzyme stabilization, we recently developed a new enzyme composite of nano-meter scale that we call "single-enzyme nanoparticles (SENs)" (9). Each enzyme molecule is surrounded with a porous composite organic/inorganic network of less than a few nanometers think. This approach represents a new type of enzyme-containing nanostructure. In experiments with perotease (chymotrypsin, CT), the activity of single enzyme nanoparticle form of the enzyme was greatly stabilized compared to the free form, without imposing a serious mass transfer limitation of substrates. In this chapter we will describe the synthesis, characterization and catalytic activity of the new SENs.

  8. Biocatalytic Synthesis of Vanillin

    PubMed Central

    Li, Tao; Rosazza, John P. N.

    2000-01-01

    The conversions of vanillic acid and O-benzylvanillic acid to vanillin were examined by using whole cells and enzyme preparations of Nocardia sp. strain NRRL 5646. With growing cultures, vanillic acid was decarboxylated (69% yield) to guaiacol and reduced (11% yield) to vanillyl alcohol. In resting Nocardia cells in buffer, 4-O-benzylvanillic acid was converted to the corresponding alcohol product without decarboxylation. Purified Nocardia carboxylic acid reductase, an ATP and NADPH-dependent enzyme, quantitatively reduced vanillic acid to vanillin. Structures of metabolites were established by 1H nuclear magnetic resonance and mass spectral analyses. PMID:10653736

  9. Water-Assisted Nitrile Oxide Cycloadditions: Synthesis of Isoxazoles and Stereoselective Syntheses of Isoxazolines and 1,2,4-Oxadiazoles.

    PubMed

    Kesornpun, Chatchai; Aree, Thammarat; Mahidol, Chulabhorn; Ruchirawat, Somsak; Kittakoop, Prasat

    2016-03-14

    Conventional methods generate nitrile oxides from oxime halides in organic solvents under basic conditions. However, the present work revealed that water-assisted generation of nitrile oxides proceeds under mild acidic conditions (pH 4-5). Cycloadditions of nitrile oxides with alkynes and alkenes easily occurred in water without using catalysts, thus yielding isoxazoles and isoxazolines, respectively, with excellent stereoselectivity toward five- and six-membered cyclic alkenes. A double stereoselective cycloaddition of two units of a nitrile oxide with cyclohexene was also achieved, thus yielding 1,2,4-oxadiazole derivatives having a unique hybrid isoxazoline-oxadiazole skeleton. Enantiomerically pure isoxazolines were prepared from monoterpenes with a ring strain. In one case, the isoxazoline with a butterfly-like structure was simply prepared, and it might be used as a ligand in asymmetric catalysis. PMID:26914177

  10. Photocatalyzed oxidation of hydrocarbons in zeolite cages

    SciTech Connect

    Frei, H.; Blatter, F.; Sun, H.

    1996-06-01

    Oxidation of hydrocarbons by molecular oxygen is a key process in chemical industry. But reactions that use O{sub 2} as the primary oxidant often produce large amounts of unwanted byproducts. One major reason that selectivities are low is that the desired products (such as alcohols or carbonyls) are more easily oxidized by O{sub 2} than the parent hydrocarbon. The authors recently discovered a simple method that gives partial oxidation of small alkenes, alkanes, and alkyl-substituted benzenes by O{sub 2} at unprecedented selectivity, even at high conversion of the hydrocarbon. The approach is based on visible light-induced chemistry of hydrocarbon-O{sub 2} collisional pairs in the cages of large-pore zeolites. Reactions are conducted at ambient temperature in the absence of solvent or photosensitizer. Here the authors describe the most interesting reactions established thus far and define issues that pertain to scale-up of the method.

  11. Copper-catalyzed aerobic oxidation of hydroxamic acids leads to a mild and versatile acylnitroso ene reaction.

    PubMed

    Frazier, Charles P; Engelking, Jarred R; Read de Alaniz, Javier

    2011-07-13

    A mild formation of transient acylnitroso intermediates using a copper chloride catalyst and 1 atm of air as the terminal oxidant is described. The mild reaction conditions enable the inter- and intramolecular acylnitroso ene reaction with a wide range of functionalized alkene partners, as well as the first asymmetric variant. Notably, this transformation provides a practical and operationally simple method for effecting allylic amidation using an environmentally benign oxidant and a readily abundant transition metal. PMID:21678942

  12. Cracking and aromatization of C{sub 6}-C{sub 10} n-alkanes and n-alkenes on a zeolite-containing catalyst

    SciTech Connect

    Gairbekov, T.M.; Takaeva, M.I.; Khadzhiev, S.N.; Manovyan, A.K.

    1992-05-10

    Despite the extensive studies on catalysis on zeolites, the question of the mechanism of the reactions of cracking and aromatization of hydrocarbons is still debated. The classic Whitmore theory hypothesizes that cracking of alkanes and alkenes takes place through the formation of the same intermediate trivalent carbenium ions of the (C{sub n}H{sub 2n+1}){sup +} type. Ola`s protolytic mechanism hypothesizes nonclassic five- (four-)coordinated ions of the (C{sub n}H{sub 2n+3}){sup +} type for cracking of alkanes and classic carbenium ions for alkenes. When the classic mechanism occurs on zeolites, an analogous effect on the rate of the reactions of alkanes and alkenes with the molecular weight of the starting hydrocarbons and similar compositions of the products obtained should be predicted. The authors investigated the transformation of individual n-alkanes and n-1-alkenes of C{sub 6}-C{sub 10} composition in the presence of a catalyst synthesized by addition of 30 wt.% decationized ultrahigh-silicon zeolite of the ZSM type (Si/Al - 16) modified with 1 wt.% zinc on {gamma}-Al{sub 2}O{sub 3}. The experiment was conducted on a flow-type laboratory setup at 425{degrees}C in conditions of the minimum effect of diffusion factors with the method described in detail previously. 13 refs., 4 figs., 1 tab.

  13. Influence of Catalyst Structure and Reaction Conditions on Anti- vs. Syn-Aminopalladation Pathways in Pd-Catalyzed Alkene Carboamination Reactions of N-Allyl Sulfamides

    PubMed Central

    Fornwald, Ryan M.; Fritz, Jonathan A.

    2014-01-01

    The Pd-catalyzed coupling of N-allyl sulfamides with aryl and alkenyl triflates to afford cyclic sulfamide products is described. In contrast to other known Pd-catalyzed alkene carboamination reactions, these transformations may be selectively induced to occur by way of either anti- or syn-aminopalladation mechanistic pathways by modifying catalyst structure and reaction conditions. PMID:24938206

  14. Metal-free nitro-carbocyclization of activated alkenes: a direct approach to synthesize oxindoles by cascade C-N and C-C bond formation.

    PubMed

    Shen, Tao; Yuan, Yizhi; Jiao, Ning

    2014-01-18

    A novel and direct metal-free nitro-carbocyclization of activated alkenes leading to valuable nitro-containing oxindoles via cascade C-N and C-C bond formation has been developed. The mechanistic study indicates that the initial NO and NO2 radical addition and the following C-H functionalization processes are involved in this transformation.

  15. Mechanisms and reactivity differences for the cobalt-catalyzed enantioselective intramolecular hydroacylation of ketones and alkenes: insights from density functional calculations.

    PubMed

    Meng, Qingxi; Wang, Fen

    2016-03-01

    Density functional theory (DFT) was used to study the cobalt(I)-catalyzed enantioselective intramolecular hydroacylation of ketones and alkenes. All intermediates and transition states were fully optimized at the M06/6-31G(d,p) level (LANL2DZ(f) for Co). The results demonstrated that the ketone and alkene present different reactivities in the enantioselective hydroacylation. In ketone hydroacylation catalyzed by the cobalt(I)-(R,R)-Ph-BPE complex, reaction channel "a" to (R)-phthalide was more favorable than channel "b" to (S)-phthalide. Hydrogen migration was both the rate-determining and chirality-limiting step, and this step was endothermic. In alkene hydroacylation catalyzed by the cobalt(I)-(R,R)-BDPP complex, reaction channel "c" leading to the formation of (S)-indanone was the most favorable, both thermodynamically and kinetically. Reductive elimination was the rate-determining step, but the chirality-limiting step was hydrogen migration, which occurred easily. The results also indicated that the alkene hydroacylation leading to (S)-indanone formation was more energetically favorable than the ketone hydroacylation that gave (R)-phthalide, both thermodynamically and kinetically. PMID:26888484

  16. Efficient conversion of vicinal diols to alkenes by treatment of the corresponding dimesylates with a catalytic, minimally fluorous, recoverable diaryl diselenide and sodium borohydride

    PubMed

    Crich; Neelamkavil; Sartillo-Piscil

    2000-12-14

    In conjunction with sodium borohydride as stoichiometric reagent a catalytic quantity of bis(4-perfluorohexylphenyl) diselenide converts vicinal dimesylates to the corresponding alkenes in good yield on warming in ethanol. The diselenide is recovered in high yield by continuous fluorous extraction.

  17. Regioselective Synthesis of a Stereodefined Heterocyclic Push-Pull Alkene (Super 1)H NMR Studies and Two-Dimensional TLC Illustrating Z/E Isomerization

    ERIC Educational Resources Information Center

    Markovic, Rade; Baranac, Marija; Jovanovic, Vesna; Dzambaski, Zdravko

    2004-01-01

    The experiment describes the regioselective synthesis of a stereodefined push-pull alkene from inexpensive chemicals. Important concepts in organic chemistry, such as resonance theory and role of solvent polarity on formation of intra- and intermolecular hydrogen bonds, which affect the configuration of the double bond in predictable way are…

  18. Quantitative determination of triperpene saponins and alkenated-phenolics from Labisia pumila using LC-UV/ELSD method and confirmation by LC-ESI-TOF

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study describes the first analytical method for the determination of saponins and alkenated-phenolics from the leaves, leaves/stems and roots of Labisia pumila using a HPLC-UV-ELSD method. The separation was achieved using a reversed phase column, PDA and ELS detection, and a water/acetonitrile...

  19. Quantitative determination of triterpene saponins and alkenated-phenolics from Labisia pumila using LC-UV/ELSD method and confirmation by LC-ESI-TOF

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study describes the first analytical method for the determination of saponins and alkenated-phenolics from the leaves, leaves/stems and roots of Labisia pumila using a HPLC-UV-ELSD method. The separation was achieved using a reversed phase column, PDA and ELS detection, and a water/acetonitrile...

  20. Investigations into Chemical Hydrogen Storage and the anti-Markovnikov Hydroamination of Alkenes

    NASA Astrophysics Data System (ADS)

    St. John, Anthony J.

    The known carbon-boron-nitrogen (CBN) material ethylenediamine bisborane (EDBB) has been prepared and tested as a potential hydrogen storage material. Dehydrogenation of EDBB was achieved using the (t BuPOCOP)Ir(H)2 (t BuPOCOP = 2,6-bis(OPtBu2)C 6H3) catalyst. This reaction results in the release of two equivalents of hydrogen per molecule of EDBB. The product of this reaction is an insoluble, likely oligomeric, species. Heating the reaction mixture does not result in the release of additional equivalents of hydrogen. A new CBN material, 1,2-B,N-cyclohexane, was targeted as a potential hydrogen storage material. The enthalpy of dehydrogenation of 1,2-B,N-cyclohexane to 1,2-dihydro-1,2-azaborine was calculated to be 23.5 kcal/mol at 298 K using the B3LYP basis set. Ultimately, our collaborators at the University of Oregon prepared 1,2-B,N-cyclohexane. This molecule is a stable solid and undergoes thermal dehydrogenation of the B-N bond at 150 °C. The dehydrogenation of a variety of cyclic CBN materials was studied with the ( tBuPOCOP)Ir(H)2 catalyst. A number of cobalt-pincer complexes were tested as ammonia borane (AB) dehydrogenation catalysts. (PhPSiNSiP)CoCl (PhPSiNSiP = (N(SiMe2CH2PPh 2)2) was found to be a very active precatalyst for AB dehydrogenation, releasing 1 equivalent of hydrogen at 2.0 mol % catalyst loading within 5 minutes. The product of this reaction was characterized as cyclopentaborazane. The catalyst lifetime is limited and the identity of the active species remains unknown. A novel [(tBuPOCOP)Co] 2Hg complex was synthesized by reaction of (t BuPOCOP)CoI with Na/Hg. This complex was fully characterized by 1H NMR spectroscopy, elemental analysis, and X-ray crystallography. A new catalytic pathway for the anti-Markovnikov hydroamination of alkenes is proposed. The individual steps of this pathway were studied with the [(MTPA)Rh(propene)][BPh 4] (MTPA = tris((6-methyl-2-pyridyl)methyl)amine) complex. Protonation of this complex with anilinium

  1. Evaluation of insect CAP2b analogs with either an (E)-alkene, trans- or a (Z)-alkene, cis-Pro isostere identifies the Pro orientation for antidiuretic activity in the stink bug.

    PubMed

    Nachman, Ronald J; Wang, Xiaodong J; Etzkorn, Felicia A; Kaczmarek, Krzysztof; Zabrocki, Janusz; Lopez, Juan; Coast, Geoffrey M

    2013-03-01

    The CAP2b neuropeptide family plays an important role in the regulation of the processes of diuresis and/or antidiuresis in a variety of insects. While Manse-CAP2b (pELYAFPRV-NH2) and native CAP2bs elicit diuretic activity in a number of species of flies, native CAP2b sequences have been shown to elicit antidiuretic activity in the kissing bug Rhodnius prolixus and the green stink bug Acrosternum hilare, the latter being an important pest of cotton and soybean in the southern United States. Analogs of CAP2b containing either a (Z)-alkene, cis-Pro or an (E)-alkene, trans-Pro isosteric component were synthesized and evaluated in an in vitro stink bug diuretic assay, which involved measurement of fluid secretion by Malpighian tubules isolated from A. hilare. The conformationally constrained trans-Pro analog demonstrated statistically significant antidiuretic activity, whereas the cis-Pro analog failed to elicit activity. The results are consistent with the adoption of a trans orientation for the Pro in CAP2b neuropeptides during interaction with receptors associated with the antidiuretic process in the stink bug. In addition, the results are further consistent with a theory of ligand-receptor coevolution between the CAP2b and pyrokinin/PBAN neuropeptide classes, both members of the '-PRXamide' superfamily. This work further identifies a scaffold with which to design mimetic CAP2b analogs as potential leads in the development of environmentally favorable pest management agents capable of disrupting CAP2b-regulated diuretic/antidiuretic functions.

  2. Iododesilylation of TIPS-, TBDPS-, and TBS-substituted alkenes in connection with the synthesis of amphidinolides B/D.

    PubMed

    Sidera, Mireia; Costa, Anna M; Vilarrasa, Jaume

    2011-09-16

    The C-Si bonds of triisopropylsilyl-substituted alkenes, 1,3-dienes, and related multifunctional substrates, as well as analogous C-TBDPS and C-TBS bonds, are readily and chemoselectively cleaved with NIS (or other sources of I(+), such as N-iodosaccharin, 1,3-diodohydantoin, and Ipy(2)BF(4)). The desired iodoalkenes are obtained stereospecifically without byproducts, provided that the reactions are carried out in CF(3)CHOHCF(3) and, in general, with 30 mol % of Ag(2)CO(3) (or AgOAc/2,6-lutidine) as an additive. Fragment C10-C18 of cytotoxic amphidinolides B1-B3 and D has been synthesized using this improved procedure.

  3. A new series of two-photon blue/violet fluorescent trans-alkenes: Green synthesis and optical properties

    NASA Astrophysics Data System (ADS)

    Huang, Jiu-Qiang; Cai, Zhi-Bin; Jin, Fan; Li, Sheng-Li; Tian, Yu-Peng

    2016-02-01

    A new series of trans-alkenes (3a-3e) containing different electron-donating groups were synthesized by the solvent-free Horner-Wadsworth-Emmons reaction, and characterized by infrared, hydrogen nuclear magnetic resonance, mass spectrometry and elemental analysis. Their UV-visible absorption, one-photon excited fluorescence, two-photon absorption, and two-photon excited fluorescence were systematically investigated in different solvents. Experimental results show different trends in linear and nonlinear optical properties with different donor units. 3a with triphenylamine donor exhibits the best optical properties. It emits strong blue up-converted fluorescence, and the two-photon absorption cross-section can be as large as 218 GM in DCM.

  4. Copper-catalysed cyanoalkylative cycloetherification of alkenes to 1,3-dihydroisobenzofurans: development and application to the synthesis of citalopram.

    PubMed

    Ha, Tu M; Wang, Qian; Zhu, Jieping

    2016-09-25

    A copper-catalysed cyanoalkylative cycloetherification of alkenes was developed. Heating a solution of substituted (2-vinylphenyl)methanol in MeCN/MeOH (v/v 7/3) in the presence of a catalytic amount of copper(ii) tetrafluoroborate hydrate [Cu(BF4)2·6H2O], bathophenanthroline, K3PO4, BnOH and (tBuO)2 afforded 1,3-dihydroisobenzofurans (phthalanes) via formation of one C(sp(3))-C(sp(3)) and one C(sp(3))-O bonds. A concise synthesis of citalopram, a marketed anti-depressant drug, was accomplished by applying this novel synthetic transformation. PMID:27546372

  5. A new series of two-photon blue/violet fluorescent trans-alkenes: Green synthesis and optical properties.

    PubMed

    Huang, Jiu-Qiang; Cai, Zhi-Bin; Jin, Fan; Li, Sheng-Li; Tian, Yu-Peng

    2016-02-01

    A new series of trans-alkenes (3a-3e) containing different electron-donating groups were synthesized by the solvent-free Horner-Wadsworth-Emmons reaction, and characterized by infrared, hydrogen nuclear magnetic resonance, mass spectrometry and elemental analysis. Their UV-visible absorption, one-photon excited fluorescence, two-photon absorption, and two-photon excited fluorescence were systematically investigated in different solvents. Experimental results show different trends in linear and nonlinear optical properties with different donor units. 3a with triphenylamine donor exhibits the best optical properties. It emits strong blue up-converted fluorescence, and the two-photon absorption cross-section can be as large as 218 GM in DCM.

  6. Cobalt-mediated cyclic and linear 2:1 cooligomerization of alkynes with alkenes: a DFT study.

    PubMed

    Gandon, Vincent; Agenet, Nicolas; Vollhardt, K Peter C; Malacria, Max; Aubert, Corinne

    2006-07-01

    The mechanism of the cobalt-mediated [2 + 2 + 2] cycloaddition of two alkynes to one alkene to give CpCo-complexed 1,3-cyclohexadienes (cyclic oligomerization) has been studied by means of DFT computations. In contrast to the mechanism of alkyne cyclotrimerization, in which final alkyne inclusion into the common cobaltacyclopentadiene features a direct "collapse" pathway to the complexed arene, alkene incorporation proceeds via insertion into a Co-C sigma-bond rather than inter- or intramolecular [4 + 2] cycloaddition. The resulting seven-membered metallacycle 7 is a key intermediate which leads to either CpCo-complexed cyclohexadiene 5 or hexatriene 13. The latter transformation, particularly favorable for ethene, accounts, in part, for the linear oligomerization observed occasionally in these reactions. With aromatic double bonds, a C-H activation mechanism by the cobaltacyclopentadiene seems more advantageous in hexatriene product formation. Detailed investigations of high- and low-spin potential energy surfaces are presented. The reactivity of triplet cobalt species was found kinetically disfavored over that of their singlet counterparts. Moreover, it could not account for the formation of CpCo-complexed hexatrienes. However, triplet cobalt complexes cannot be ruled out since all unsaturated species appearing in this study were found to exhibit triplet ground states. Consequently, a reaction pathway that involves a mixing of both spin-state energy surfaces is also described (two-state reactivity). Support for such a pathway comes from the location of several low-lying minimum-energy crossing points (MECPs) of the two surfaces.

  7. Encapsulated Laccases for the Room-Temperature Oxidation of Aromatics: Towards Synthetic Low-Molecular-Weight Lignins.

    PubMed

    Pistone, Lucia; Ottolina, Gianluca; De, Sudipta; Romero, Antonio A; Martins, Lígia O; Luque, Rafael

    2016-04-01

    A new approach for the encapsulation of laccases with enhanced activity and stability by biomimetic silica mineralisation is reported. A range of lignin model compounds, which includes syringol, syringyl acid, 4-vinylphenol, gallic acid, vanillic acid and guaiacol, was oxidised to lignin-type polymers by the silica-immobilised laccase systems at room temperature. The oxidation rate of the immobilised systems was lower than that of the free enzyme counterparts, but interesting products were observed with the new bio-catalytic materials, which showed reusability and good stability.

  8. Copper(II) Carboxylate Promoted Intramolecular Carboamination of Alkenes for the Synthesis of Polycyclic Lactams

    PubMed Central

    Fuller, Peter H.; Chemler, Sherry R.

    2008-01-01

    The copper(II) carboxylate promoted intramolecular carboamination reactions of variously substituted γ-alkenyl amides have been investigated. These oxidative cyclization reactions efficiently provide polycyclic lactams, useful intermediates in nitrogen heterocycle synthesis, in good to excellent yields. The efficiency of the carboamination process is dependent upon the structure of the amide backbone as well as the nitrogen substituent. PMID:18044907

  9. KetoABNO/NOx Cocatalytic Aerobic Oxidation of Aldehydes to Carboxylic Acids and Access to α-Chiral Carboxylic Acids via Sequential Asymmetric Hydroformylation/Oxidation.

    PubMed

    Miles, Kelsey C; Abrams, M Leigh; Landis, Clark R; Stahl, Shannon S

    2016-08-01

    A method for aerobic oxidation of aldehydes to carboxylic acids has been developed using organic nitroxyl and NOx cocatalysts. KetoABNO (9-azabicyclo[3.3.1]nonan-3-one N-oxyl) and NaNO2 were identified as the optimal nitroxyl and NOx sources, respectively. The mildness of the reaction conditions enables sequential asymmetric hydroformylation of alkenes/aerobic aldehyde oxidation to access α-chiral carboxylic acids without racemization. The scope, utility, and limitations of the oxidation method are further evaluated with a series of achiral aldehydes bearing diverse functional groups.

  10. Enhanced biocatalytic production of L-cysteine by Pseudomonas sp. B-3 with in situ product removal using ion-exchange resin.

    PubMed

    Wang, Pu; He, Jun-Yao; Yin, Jiang-Feng

    2015-03-01

    Bioconversion of DL-2-amino-Δ(2)-thiazoline-4-carboxylic acid (DL-ATC) catalyzed by whole cells of Pseudomonas sp. was successfully applied for the production of L-cysteine. It was found, however, like most whole-cell biocatalytic processes, the accumulated L-cysteine produced obvious inhibition to the activity of biocatalyst and reduced the yield. To improve L-cysteine productivity, an anion exchange-based in situ product removal (ISPR) approach was developed. Several anion-exchange resins were tested to select a suitable adsorbent used in the bioconversion of DL-ATC for the in situ removal of L-cysteine. The strong basic anion-exchange resin 201 × 7 exhibited the highest adsorption capacity for L-cysteine and low adsorption for DL-ATC, which is a favorable option. With in situ addition of 60 g L(-1) resin 201 × 7, the product inhibition can be reduced significantly and 200 mmol L(-1) of DL-ATC was converted to L-cysteine with 90.4 % of yield and 28.6 mmol L(-1 )h(-1) of volumetric productivity. Compared to the bioconversion without the addition of resin, the volumetric productivity of L-cysteine was improved by 2.27-fold using ISPR method.

  11. Combination of deep eutectic solvent and ionic liquid to improve biocatalytic reduction of 2-octanone with Acetobacter pasteurianus GIM1.158 cell

    PubMed Central

    Xu, Pei; Du, Peng-Xuan; Zong, Min-Hua; Li, Ning; Lou, Wen-Yong

    2016-01-01

    The efficient anti-Prelog asymmetric reduction of 2-octanone with Acetobacter pasteurianus GIM1.158 cells was successfully performed in a biphasic system consisting of deep eutectic solvent (DES) and water-immiscible ionic liquid (IL). Various DESs exerted different effects on the synthesis of (R)-2-octanol. Choline chloride/ethylene glycol (ChCl/EG) exhibited good biocompatibility and could moderately increase the cell membrane permeability thus leading to the better results. Adding ChCl/EG increased the optimal substrate concentration from 40 mM to 60 mM and the product e.e. kept above 99.9%. To further improve the reaction efficiency, water-immiscible ILs were introduced to the reaction system and an enhanced substrate concentration (1.5 M) was observed with C4MIM·PF6. Additionally, the cells manifested good operational stability in the reaction system. Thus, the efficient biocatalytic process with ChCl/EG and C4MIM·PF6 was promising for efficient synthesis of (R)-2-octanol. PMID:27185089

  12. Biocatalytic behaviour of immobilized Rhizopus oryzae lipase in the 1,3-selective ethanolysis of sunflower oil to obtain a biofuel similar to biodiesel.

    PubMed

    Luna, Carlos; Verdugo, Cristóbal; Sancho, Enrique D; Luna, Diego; Calero, Juan; Posadillo, Alejandro; Bautista, Felipa M; Romero, Antonio A

    2014-01-01

    A new biofuel similar to biodiesel was obtained in the 1,3-selective transesterification reaction of sunflower oil with ethanol using as biocatalyst a Rhizopus oryzae lipase (ROL) immobilized on Sepiolite, an inorganic support. The studied lipase was a low cost powdered enzyme preparation, Biolipase-R, from Biocon-Spain, a multipurpose additive used in food industry. In this respect, it is developed a study to optimize the immobilization procedure of these lipases on Sepiolite. Covalent immobilization was achieved by the development of an inorganic-organic hybrid linker formed by a functionalized hydrocarbon chain with a pendant benzaldehyde, bonded to the AlPO4 support surface. Thus, the covalent immobilization of lipases on amorphous AlPO4/sepiolite (20/80 wt %) support was evaluated by using two different linkers (p-hydroxybenzaldehyde and benzylamine-terephthalic aldehyde, respectively). Besides, the catalytic behavior of lipases after physical adsorption on the demineralized sepiolite  was also evaluated. Obtained results indicated that covalent immobilization with the p-hydroxybenzaldehyde linker gave the best biocatalytic behavior. Thus, this covalently immobilized lipase showed a remarkable stability as well as an excellent capacity of reutilization (more than five successive reuses) without a significant loss of its initial catalytic activity. This could allow a more efficient fabrication of biodiesel minimizing the glycerol waste production. PMID:25093983

  13. Biocatalytic behaviour of immobilized Rhizopus oryzae lipase in the 1,3-selective ethanolysis of sunflower oil to obtain a biofuel similar to biodiesel.

    PubMed

    Luna, Carlos; Verdugo, Cristóbal; Sancho, Enrique D; Luna, Diego; Calero, Juan; Posadillo, Alejandro; Bautista, Felipa M; Romero, Antonio A

    2014-08-04

    A new biofuel similar to biodiesel was obtained in the 1,3-selective transesterification reaction of sunflower oil with ethanol using as biocatalyst a Rhizopus oryzae lipase (ROL) immobilized on Sepiolite, an inorganic support. The studied lipase was a low cost powdered enzyme preparation, Biolipase-R, from Biocon-Spain, a multipurpose additive used in food industry. In this respect, it is developed a study to optimize the immobilization procedure of these lipases on Sepiolite. Covalent immobilization was achieved by the development of an inorganic-organic hybrid linker formed by a functionalized hydrocarbon chain with a pendant benzaldehyde, bonded to the AlPO4 support surface. Thus, the covalent immobilization of lipases on amorphous AlPO4/sepiolite (20/80 wt %) support was evaluated by using two different linkers (p-hydroxybenzaldehyde and benzylamine-terephthalic aldehyde, respectively). Besides, the catalytic behavior of lipases after physical adsorption on the demineralized sepiolite  was also evaluated. Obtained results indicated that covalent immobilization with the p-hydroxybenzaldehyde linker gave the best biocatalytic behavior. Thus, this covalently immobilized lipase showed a remarkable stability as well as an excellent capacity of reutilization (more than five successive reuses) without a significant loss of its initial catalytic activity. This could allow a more efficient fabrication of biodiesel minimizing the glycerol waste production.

  14. Biocatalytic synthesis of flavor ester "pentyl valerate" using Candida rugosa lipase immobilized in microemulsion based organogels: effect of parameters and reusability.

    PubMed

    Raghavendra, Tripti; Panchal, Nilam; Divecha, Jyoti; Shah, Amita; Madamwar, Datta

    2014-01-01

    Pentyl valerate was synthesized biocatalytically using Candida rugosa lipase (CRL) immobilized in microemulsion based organogels (MBGs). The optimum conditions were found to be pH 7.0, temperature of 37 °C, ratio of concentration of water to surfactant (Wo) of 60, and the surfactant sodium bis-2-(ethylhexyl)sulfosuccinate (AOT) for MBG preparation. Although kinetic studies revealed that the enzyme in free form had high affinity towards substrates (K(m) = 23.2 mM for pentanol and 76.92 mM for valeric acid) whereas, after immobilization, the K(m) values increased considerably (74.07 mM for pentanol and 83.3 mM for valeric acid) resulting in a slower reaction rate, the maximum conversion was much higher in case of immobilized enzyme (~99%) as compared to free enzyme (~19%). Simultaneous effects of important parameters were studied using response surface methodology (RSM) conjugated with Box-Behnken design (BBD) with five variables (process parameters), namely, enzyme concentration, initial water content (Wo), solvent used for MBG preparation, substrate ratio and time, and response as the final product formation, that is, pentyl valerate (%). The MBGs were reused for 10 consecutive cycles for ester synthesis. Efficacy of AOT/isooctane as dehydrating agent for extracting excess water from MBGs was found to exert a positive effect on the esterification reaction.

  15. Combination of deep eutectic solvent and ionic liquid to improve biocatalytic reduction of 2-octanone with Acetobacter pasteurianus GIM1.158 cell.

    PubMed

    Xu, Pei; Du, Peng-Xuan; Zong, Min-Hua; Li, Ning; Lou, Wen-Yong

    2016-01-01

    The efficient anti-Prelog asymmetric reduction of 2-octanone with Acetobacter pasteurianus GIM1.158 cells was successfully performed in a biphasic system consisting of deep eutectic solvent (DES) and water-immiscible ionic liquid (IL). Various DESs exerted different effects on the synthesis of (R)-2-octanol. Choline chloride/ethylene glycol (ChCl/EG) exhibited good biocompatibility and could moderately increase the cell membrane permeability thus leading to the better results. Adding ChCl/EG increased the optimal substrate concentration from 40 mM to 60 mM and the product e.e. kept above 99.9%. To further improve the reaction efficiency, water-immiscible ILs were introduced to the reaction system and an enhanced substrate concentration (1.5 M) was observed with C4MIM·PF6. Additionally, the cells manifested good operational stability in the reaction system. Thus, the efficient biocatalytic process with ChCl/EG and C4MIM·PF6 was promising for efficient synthesis of (R)-2-octanol.

  16. Stereoselective Synthesis of Trisubstituted Alkenes through Sequential Iron-Catalyzed Reductive anti-Carbozincation of Terminal Alkynes and Base-Metal-Catalyzed Negishi Cross-Coupling.

    PubMed

    Cheung, Chi Wai; Hu, Xile

    2015-12-01

    The stereoselective synthesis of trisubstituted alkenes is challenging. Here, we show that an iron-catalyzed anti-selective carbozincation of terminal alkynes can be combined with a base-metal-catalyzed cross-coupling to prepare trisubstituted alkenes in a one-pot reaction and with high regio- and stereocontrol. Cu-, Ni-, and Co-based catalytic systems are developed for the coupling of sp-, sp(2) -, and sp(3) -hybridized carbon electrophiles, respectively. The method encompasses a large substrate scope, as various alkynyl, aryl, alkenyl, acyl, and alkyl halides are suitable coupling partners. Compared with conventional carbometalation reactions of alkynes, the current method avoids pre-made organometallic reagents and has a distinct stereoselectivity.

  17. The role of minerals in the thermal alteration of organic matter. IV - Generation of n-alkanes, acyclic isoprenoids, and alkenes in laboratory experiments

    NASA Technical Reports Server (NTRS)

    Huizinga, Bradley J.; Tannenbaum, Eli; Kaplan, Isaac R.

    1987-01-01

    The effect of common sedimentary minerals (illite, Na-montmorillonite, or calcite) under different water concentrations on the generation and release of n-alkanes, acyclic isoprenoids, and select alkenes from oil-prone kerogens was investigated. Matrices containing Green River Formation kerogen or Monterey Formation kerogen, alone or in the presence of minerals, were heated at 200 or 300 C for periods of up to 1000 hours, and the pyrolysis products were analyzed. The influence of the first two clay minerals was found to be critically dependent on the water content. Under the dry pyrolysis conditions, both minerals significantly reduced alkene formation; the C12+ n-alkanes and acyclic isoprenoids were mostly destroyed by montmorillonite, but underwent only minor alteration with illite. Under hydrous conditions (mineral/water of 2/1), the effects of both minerals were substantially reduced. Calcite had no significant effect on the thermal evolution of the hydrocarbons.

  18. Molecular weight growth in Titan's atmosphere: branching pathways for the reaction of 1-propynyl radical (H3CC≡C˙) with small alkenes and alkynes.

    PubMed

    Kirk, Benjamin B; Savee, John D; Trevitt, Adam J; Osborn, David L; Wilson, Kevin R

    2015-08-28

    The reaction of small hydrocarbon radicals (i.e.˙CN, ˙C2H) with trace alkenes and alkynes is believed to play an important role in molecular weight growth and ultimately the formation of Titan's characteristic haze. Current photochemical models of Titan's atmosphere largely assume hydrogen atom abstraction or unimolecular hydrogen elimination reactions dominate the mechanism, in contrast to recent experiments that reveal significant alkyl radical loss pathways during reaction of ethynyl radical (˙C2H) with alkenes and alkynes. In this study, the trend is explored for the case of a larger ethynyl radical analogue, the 1-propynyl radical (H3CC[triple bond, length as m-dash]C˙), a likely product from the high-energy photolysis of propyne in Titan's atmosphere. Using synchrotron vacuum ultraviolet photoionization mass spectrometry, product branching ratios are measured for the reactions of 1-propynyl radical with a suite of small alkenes (ethylene and propene) and alkynes (acetylene and d4-propyne) at 4 Torr and 300 K. Reactions of 1-propynyl radical with acetylene and ethylene form single products, identified as penta-1,3-diyne and pent-1-en-3-yne, respectively. These products form by hydrogen atom loss from the radical-adduct intermediates. The reactions of 1-propynyl radical with d4-propyne and propene form products from both hydrogen atom and methyl loss, (-H = 27%, -CH3 = 73%) and (-H = 14%, -CH3 = 86%), respectively. Together, these results indicate that reactions of ethynyl radical analogues with alkenes and alkynes form significant quantities of products by alkyl loss channels, suggesting that current photochemical models of Titan over predict both hydrogen atom production as well as the efficiency of molecular weight growth in these reactions.

  19. Molecular weight growth in Titan's atmosphere: Branching pathways for the reaction of 1-propynyl radical (H3CC≡C˙) with small alkenes and alkynes

    DOE PAGESBeta

    Kirk, Benjamin B.; Savee, John D.; Trevitt, Adam J.; Osborn, David L.; Wilson, Kevin R.

    2015-07-16

    The reaction of small hydrocarbon radicals (i.e. ˙CN, ˙C2H) with trace alkenes and alkynes is believed to play an important role in molecular weight growth and ultimately the formation of Titan's characteristic haze. Current photochemical models of Titan's atmosphere largely assume hydrogen atom abstraction or unimolecular hydrogen elimination reactions dominate the mechanism, in contrast to recent experiments that reveal significant alkyl radical loss pathways during reaction of ethynyl radical (˙C2H) with alkenes and alkynes. In this study, the trend is explored for the case of a larger ethynyl radical analogue, the 1-propynyl radical (H3CC≡C˙), a likely product from the high-energymore » photolysis of propyne in Titan's atmosphere. Using synchrotron vacuum ultraviolet photoionization mass spectrometry, product branching ratios are measured for the reactions of 1-propynyl radical with a suite of small alkenes (ethylene and propene) and alkynes (acetylene and d4-propyne) at 4 Torr and 300 K. Reactions of 1-propynyl radical with acetylene and ethylene form single products, identified as penta-1,3-diyne and pent-1-en-3-yne, respectively. These products form by hydrogen atom loss from the radical-adduct intermediates. The reactions of 1-propynyl radical with d4-propyne and propene form products from both hydrogen atom and methyl loss, (–H = 27%, –CH3 = 73%) and (–H = 14%, –CH3 = 86%), respectively. Altogether, these results indicate that reactions of ethynyl radical analogues with alkenes and alkynes form significant quantities of products by alkyl loss channels, suggesting that current photochemical models of Titan over predict both hydrogen atom production as well as the efficiency of molecular weight growth in these reactions.« less

  20. Molecular weight growth in Titan's atmosphere: Branching pathways for the reaction of 1-propynyl radical (H3CC≡C˙) with small alkenes and alkynes

    SciTech Connect

    Kirk, Benjamin B.; Savee, John D.; Trevitt, Adam J.; Osborn, David L.; Wilson, Kevin R.

    2015-07-16

    The reaction of small hydrocarbon radicals (i.e. ˙CN, ˙C2H) with trace alkenes and alkynes is believed to play an important role in molecular weight growth and ultimately the formation of Titan's characteristic haze. Current photochemical models of Titan's atmosphere largely assume hydrogen atom abstraction or unimolecular hydrogen elimination reactions dominate the mechanism, in contrast to recent experiments that reveal significant alkyl radical loss pathways during reaction of ethynyl radical (˙C2H) with alkenes and alkynes. In this study, the trend is explored for the case of a larger ethynyl radical analogue, the 1-propynyl radical (H3CC≡C˙), a likely product from the high-energy photolysis of propyne in Titan's atmosphere. Using synchrotron vacuum ultraviolet photoionization mass spectrometry, product branching ratios are measured for the reactions of 1-propynyl radical with a suite of small alkenes (ethylene and propene) and alkynes (acetylene and d4-propyne) at 4 Torr and 300 K. Reactions of 1-propynyl radical with acetylene and ethylene form single products, identified as penta-1,3-diyne and pent-1-en-3-yne, respectively. These products form by hydrogen atom loss from the radical-adduct intermediates. The reactions of 1-propynyl radical with d4-propyne and propene form products from both hydrogen atom and methyl loss, (–H = 27%, –CH3 = 73%) and (–H = 14%, –CH3 = 86%), respectively. Altogether, these results indicate that reactions of ethynyl radical analogues with alkenes and alkynes form significant quantities of products by alkyl loss channels, suggesting that current photochemical models of Titan over predict both hydrogen atom production as well as the efficiency of molecular weight growth in these reactions.

  1. Synthesis of 3,3-Spiroindolines via FeCl3-Mediated Cyclization of Aryl- or Alkene-Containing 3-Substituted N-Ac Indoles.

    PubMed

    Nandi, Raj Kumar; Guillot, Régis; Kouklovsky, Cyrille; Vincent, Guillaume

    2016-04-15

    We report the cyclization of 3-substituted N-acetylindoles for the straightforward synthesis of 3,3-spiroindolines via the Friedel-Crafts reaction of an appended aryl group or the formal [2 + 2] cycloaddition of an appended alkene. Our strategy involves an Umpolung of the C2═C3 bond of the indole nucleus during FeCl3-mediated hydroarylation or annulation reactions. PMID:27015315

  2. Molecular weight growth in Titan's atmosphere: branching pathways for the reaction of 1-propynyl radical (H3CC≡C˙) with small alkenes and alkynes.

    PubMed

    Kirk, Benjamin B; Savee, John D; Trevitt, Adam J; Osborn, David L; Wilson, Kevin R

    2015-08-28

    The reaction of small hydrocarbon radicals (i.e.˙CN, ˙C2H) with trace alkenes and alkynes is believed to play an important role in molecular weight growth and ultimately the formation of Titan's characteristic haze. Current photochemical models of Titan's atmosphere largely assume hydrogen atom abstraction or unimolecular hydrogen elimination reactions dominate the mechanism, in contrast to recent experiments that reveal significant alkyl radical loss pathways during reaction of ethynyl radical (˙C2H) with alkenes and alkynes. In this study, the trend is explored for the case of a larger ethynyl radical analogue, the 1-propynyl radical (H3CC[triple bond, length as m-dash]C˙), a likely product from the high-energy photolysis of propyne in Titan's atmosphere. Using synchrotron vacuum ultraviolet photoionization mass spectrometry, product branching ratios are measured for the reactions of 1-propynyl radical with a suite of small alkenes (ethylene and propene) and alkynes (acetylene and d4-propyne) at 4 Torr and 300 K. Reactions of 1-propynyl radical with acetylene and ethylene form single products, identified as penta-1,3-diyne and pent-1-en-3-yne, respectively. These products form by hydrogen atom loss from the radical-adduct intermediates. The reactions of 1-propynyl radical with d4-propyne and propene form products from both hydrogen atom and methyl loss, (-H = 27%, -CH3 = 73%) and (-H = 14%, -CH3 = 86%), respectively. Together, these results indicate that reactions of ethynyl radical analogues with alkenes and alkynes form significant quantities of products by alkyl loss channels, suggesting that current photochemical models of Titan over predict both hydrogen atom production as well as the efficiency of molecular weight growth in these reactions. PMID:26204935

  3. Cross metathesis with hydroxamate and benzamide BOC-protected alkenes to access HDAC inhibitors and their biological evaluation highlighted intrinsic activity of BOC-protected dihydroxamates.

    PubMed

    Zwick, Vincent; Nurisso, Alessandra; Simões-Pires, Claudia; Bouchet, Samuel; Martinet, Nadine; Lehotzky, Attila; Ovadi, Judit; Cuendet, Muriel; Blanquart, Christophe; Bertrand, Philippe

    2016-01-01

    Conditions for the metathesis of alkenes in the convergent synthesis of HDAC inhibitors have been improved by continuous catalyst flow injection in the reaction media. Intermediate and target compounds obtained were tested for their ability to induce HDAC inhibition and tubulin acetylation, revealing the key role of the tert-butyloxycarbonyl (BOC) group for more HDAC6 selectivity. Molecular modelling added rationale for this BOC effect.

  4. Cross metathesis with hydroxamate and benzamide BOC-protected alkenes to access HDAC inhibitors and their biological evaluation highlighted intrinsic activity of BOC-protected dihydroxamates.

    PubMed

    Zwick, Vincent; Nurisso, Alessandra; Simões-Pires, Claudia; Bouchet, Samuel; Martinet, Nadine; Lehotzky, Attila; Ovadi, Judit; Cuendet, Muriel; Blanquart, Christophe; Bertrand, Philippe

    2016-01-01

    Conditions for the metathesis of alkenes in the convergent synthesis of HDAC inhibitors have been improved by continuous catalyst flow injection in the reaction media. Intermediate and target compounds obtained were tested for their ability to induce HDAC inhibition and tubulin acetylation, revealing the key role of the tert-butyloxycarbonyl (BOC) group for more HDAC6 selectivity. Molecular modelling added rationale for this BOC effect. PMID:26611919

  5. An efficient protocol for the stereoselective construction of multisubstituted fluorine-containing alkenes. A palladium-catalyzed bisstannylation of fluorinated internal alkynes.

    PubMed

    Konno, Tsutomu; Kinugawa, Ryoko; Morigaki, Atsunori; Ishihara, Takashi

    2009-11-01

    On treatment of various fluorinated internal alkynes with 1.2 equiv of hexabutylditin under the influence of 2.5 mol % of Pd(t-BuNC)(2)Cl(2) in THF at room temperature for 4 h, the bisstannylation proceeded smoothly to afford the corresponding bisstannylated cis-adducts in high yields. Thus obtained adducts were subjected to the Stille cross-coupling reaction to give the corresponding tetrasubstituted fluorine-containing alkenes with defined stereochemistry in good yields.

  6. Base-promoted synthesis of coumarins from salicylaldehydes and aryl-substituted 1,1-dibromo-1-alkenes under transition-metal-free conditions.

    PubMed

    Liu, Jianming; Zhang, Xin; Shi, Lijun; Liu, Muwen; Yue, Yuanyuan; Li, Fuwei; Zhuo, Kelei

    2014-09-01

    Facile synthesis of coumarin via the tandem reaction of salicylaldehyde with aryl-substituted 1,1-dibromo-1-alkene was developed. This new protocol proceeds smoothly under mild and transition-metal-free conditions, it allows rapid access to coumarins containing various heteroatoms that are more difficult to prepare by traditional methods. Based on the isolated intermediate of 4-(diethylamino)-3-phenylchroman-2-one and detailed mechanistic studies, a credible tandem pathway was proposed. PMID:25027244

  7. Synthesis and Characterization of α-Diimine Complexes of Group 13 Metals and Their Catalytic Activity toward the Epoxidation of Alkenes.

    PubMed

    Koellner, Connor A; Piro, Nicholas A; Kassel, W Scott; Goldsmith, Christian R; Graves, Christopher R

    2015-08-01

    Complexes of group 13 metal (Al, Ga, In) ions with neutral α-diimine ligands have been prepared and characterized. The Al(III) and Ga(III) [M(α-diimine)2Cl2][MCl4] complexes catalyze the epoxidation of alkenes by peracetic acid under ambient conditions. The two complexes display nearly identical reactivity, demonstrating that inexpensive and highly abundant aluminum is a viable catalytic metal for these reactions. PMID:26192441

  8. Synthesis of Highly Functionalized Tri- and Tetrasubstituted Alkenes via Pd-Catalyzed 1,2-Hydrovinylation of Terminal 1,3-Dienes

    PubMed Central

    2016-01-01

    An efficient method for the construction of Csp2–Csp3 bond in a regio- and stereoselective fashion involving 1,3-terminal dienes, enol triflates/nonaflates, and sodium formate under Pd(0)-catalysis is described. The three component assembly allows trapping of a π-allyl intermediate, after the initial migratory insertion of the diene, by a hydride source that leads to structurally complex and synthetically challenging tri- and tetrasubstituted alkene building blocks. PMID:25555197

  9. Implications of carbon isotope ratios of C27-C33 alkanes and C37 alkenes for the sources of organic matter in the southern ocean surface sediments

    NASA Astrophysics Data System (ADS)

    Ohkouchi, N.; Kawamura, K.; Takemoto, N.; Ikehara, M.; Nakatsuka, T.

    2000-01-01

    Carbon isotopic ratios (δ13C) of C27-C33 n-alkanes and C37 alkenes were measured in the surface sediments from Australian sector of Southern Ocean (47.6°-65.5°S). The δ13C of C31 n-alkane derived from higher plant wax shows little change along the latitude (-28.7±0.6 ‰), whereas δ13C of C37 alkenes derived from haptophyte algae decreases from -24.6±0.7 ‰ at 47.6°S to -32.1±1.2 ‰ at 63.9°S. Relatively heavy δ13C values of C31 n-alkane suggest significant contribution of C4 plant waxes or conifer resin whose δ13C of n-alkanes are significantly heavier than those of C3 plants. The δ13C of total organic carbon exhibits a latitudinal pattern similar to that of C37 alkenes, suggesting that organic carbon in the sediments is primarily of marine origin.

  10. Iridium(I) complexes with anionic N-heterocyclic carbene ligands as catalysts for the hydrogenation of alkenes in nonpolar media.

    PubMed

    Kolychev, Eugene L; Kronig, Sabrina; Brandhorst, Kai; Freytag, Matthias; Jones, Peter G; Tamm, Matthias

    2013-08-21

    A series of lithium complexes of anionic N-heterocyclic carbenes that contain a weakly coordinating borate moiety (WCA-NHC) was prepared in one step from free N-heterocyclic carbenes by deprotonation with n-butyl lithium followed by borane addition. The reaction of the resulting lithium-carbene adducts with [M(COD)Cl]2 (M = Rh, Ir; COD = 1,5-cyclooctadiene) afforded zwitterionic rhodium(I) and iridium(I) complexes of the type [(WCA-NHC)M(COD)], in which the metal atoms exhibit an intramolecular interaction with the N-aryl groups of the carbene ligands. For M = Rh, the neutral complex [(WCA-NHC)Rh(CO)2] and the ate complex (NEt4)[(WCA-NHC)Rh(CO)2Cl] were prepared, with the latter allowing an assessment of the donor ability of the ligand by IR spectroscopy. The zwitterionic iridium-COD complexes were tested as catalysts for the homogeneous hydrogenation of alkenes, which can be performed in the presence of nonpolar solvents or in the neat alkene substrate. Thereby, the most active complex showed excellent stability and activity in hydrogenation of alkenes at low catalyst loadings (down to 10 ppm).

  11. New insights into the stability of alkenes and alkynes, fluoro-substituted or not: a DFT, G4, QTAIM and GVB study.

    PubMed

    Silva de Freitas, Gutto Raffyson; Firme, Caio Lima

    2013-12-01

    Many undergraduate organic chemistry books do not agree with the order of relative stability of alkenes towards hydrogenation reactions. Although they ascribe the stability of alkenes to the number and spatial position of the alkyl groups attached to the vinyl carbon atoms, results from the quantum theory of atoms in molecules indicate that the influence of an alkyl substituent on the stability of unsaturated hydrocarbons arises from the slight removal of electron density of the π bond, not from donation of their charge density to unsaturated carbon atoms as stated in many text books. There is an inverse relation between delocalization index--the number of shared electrons between two atoms, or Wiberg bond index of C=C bond--and the number of methyl groups attached to the vinyl carbon atoms. Electron withdrawing groups (EWGs) attached to unsaturated carbon atoms of alkenes and alkynes have two different behaviors: slight EWGs (alkyl groups) stabilize unsaturated carbon atoms while the strong EWG destabilizes the unsaturated carbon atoms. Generalized valence bond theory was also used to study the ambiguous behavior of fluorine substituents bonded to vinyl carbon atoms.

  12. Copper(I)-induced amplification of a [2]catenane in a virtual dynamic library of macrocyclic alkenes.

    PubMed

    Berrocal, José Augusto; Nieuwenhuizen, Marko M L; Mandolini, Luigi; Meijer, E W; Di Stefano, Stefano

    2014-08-28

    Olefin cross-metathesis of diluted dichloromethane solutions (≤0.15 M) of the 28-membered macrocyclic alkene C1, featuring a 1,10-phenanthroline moiety in the backbone, as well as of catenand 1, composed of two identical interlocked C1 units, generates families of noninterlocked oligomers Ci. The composition of the libraries is strongly dependent on the monomer concentration, but independent of whether C1 or 1 is used as feedstock, as expected for truly equilibrated systems. Accordingly, the limiting value 0.022 M approached by the equilibrium concentration of C1 when the total monomer concentration approaches the critical value, as predicted by the Jacobson-Stockmayer theory, provides a reliable estimate of the thermodynamically effective molarity. Catenand 1 behaves as a virtual component of the dynamic libraries, in that there is no detectable trace of its presence in the equilibrated mixtures, but becomes the major component - in the form of its copper(I) complex - when olefin cross-metathesis is carried out in the presence of a copper(I) salt.

  13. Reaction of sp/sup 2/ C-H bonds in unactivated alkenes with bis(diphosphine) complexes of iron

    SciTech Connect

    Baker, M.V.; Field, L.D.

    1986-11-12

    Over the last 10 years, there has been much interest in the chemistry of coordinatively unsaturated transition-metal complexes, particularly in the activation of alkyl C-H bonds by complexes of Ir, Rh, Re, and W. Some early fundamental work in the area of C-H bond activation involved Fe(DMPE)/sub 2/ (1) (DMPE = 1,2-bis(dimethylphosphino)ethane), a reactive intermediate generated by reductive elimination of naphthalene from cis-FeH(Np)DMPE)/sub 2/ (Np = 2-naphthyl); however, this system was limited in that only substrates with a reactivity greater than (or comparable to) that of the naphthalene byproduct could be examined. In addition, this route to 1 necessarily required reaction temperatures close to room temperature, where any thermally labile products may not have been sufficiently stable to be observed or characterized. An alternative, more versatile route to 1 is by photolysis of the dihydride FeH/sub 2/(DMPE)/sub 2/ (2). The authors have examined the reactions of 1, generated photochemically at low temperature, with hydrocarbons, and report here the formation of products arising from Fe insertion into sp/sup 2/ C-H bonds of unactivated alkenes.

  14. Gas-Phase Reactions of Doubly Charged Lanthanide Cations with Alkanes and Alkenes. Trends in Metal(2+) Reactivity

    SciTech Connect

    Gibson, John K.; Marcalo, Joaquim; Santos, Marta; Pires de Matos, Antonio; Haire, Richard G.

    2008-12-08

    The gas-phase reactivity of doubly-charged lanthanide cations, Ln2+ (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), with alkanes (methane, ethane, propane, n-butane) and alkenes (ethene, propene, 1-butene) was studied by Fourier transform ion cyclotron resonance mass spectrometry. The reaction products consisted of different combinations of doubly-charged organometallic ions?adducts or species formed via metal-ion-induced hydrogen, dihydrogen, alkyl, or alkane eliminations from the hydrocarbons?and singly-charged ions that resulted from electron, hydride, or methide transfers from the hydrocarbons to the metal ions. The only lanthanide cations capable of activating the hydrocarbons to form doubly-charged organometallic ions were La2+, Ce2+, Gd2+, and Tb2+, which have ground-state or low-lying d1 electronic configurations. Lu2+, with an accessible d1 electronic configuration but a rather high electron affinity, reacted only through transfer channels. The remaining Ln2+ reacted via transfer channels or adduct formation. The different accessibilities of d1 electronic configurations and the range of electron affinities of the Ln2+ cations allowed for a detailed analysis of the trends for metal(2+) reactivity and the conditions for occurrence of bond activation, adduct formation, and electron, hydride, and methide transfers.

  15. Terminal Olefin (1-Alkene) Biosynthesis by a Novel P450 Fatty Acid Decarboxylase from Jeotgalicoccus Species ▿ †

    PubMed Central

    Rude, Mathew A.; Baron, Tarah S.; Brubaker, Shane; Alibhai, Murtaza; Del Cardayre, Stephen B.; Schirmer, Andreas

    2011-01-01

    Terminal olefins (1-alkenes) are natural products that have important industrial applications as both fuels and chemicals. However, their biosynthesis has been largely unexplored. We describe a group of bacteria, Jeotgalicoccus spp., which synthesize terminal olefins, in particular 18-methyl-1-nonadecene and 17-methyl-1-nonadecene. These olefins are derived from intermediates of fatty acid biosynthesis, and the key enzyme in Jeotgalicoccus sp. ATCC 8456 is a terminal olefin-forming fatty acid decarboxylase. This enzyme, Jeotgalicoccus sp. OleT (OleTJE), was identified by purification from cell lysates, and its encoding gene was identified from a draft genome sequence of Jeotgalicoccus sp. ATCC 8456 using reverse genetics. Heterologous expression of the identified gene conferred olefin biosynthesis to Escherichia coli. OleTJE is a P450 from the cyp152 family, which includes bacterial fatty acid hydroxylases. Some cyp152 P450 enzymes have the ability to decarboxylate and to hydroxylate fatty acids (in α- and/or β-position), suggesting a common reaction intermediate in their catalytic mechanism and specific structural determinants that favor one reaction over the other. The discovery of these terminal olefin-forming P450 enzymes represents a third biosynthetic pathway (in addition to alkane and long-chain olefin biosynthesis) to convert fatty acid intermediates into hydrocarbons. Olefin-forming fatty acid decarboxylation is a novel reaction that can now be added to the catalytic repertoire of the versatile cytochrome P450 enzyme family. PMID:21216900

  16. Metal Catalysis in Thiolation and Selenation Reactions of Alkynes Leading to Chalcogen‐Substituted Alkenes and Dienes

    PubMed Central

    2015-01-01

    Abstract This review covers recent achievements in metal‐catalyzed Z−H and Z−Z (Z=S, Se) bond addition to the triple bonds of alkynes—a convenient and atom‐efficient way to carbon‐element bond formation. Various catalytic systems (both homogeneous and heterogeneous) developed to date to obtain mono‐ and bis‐chalcogen‐substituted alkenes or dienes, as well as carbonyl compounds or heterocycles, starting from simple and available alkynes and chalcogenols or dichalcogenides are described. The right choice of metal and ligands allows us to perform these transformations with high selectivities under mild reaction conditions, thus tolerating unprotected functional groups in substrates and broadening ways of further modification of the products. The main aim of the review is to show the potential of the catalytic methods developed in synthetic organic chemistry. Thus, emphasis is made on the scope of reactions, types of products that can be selectively formed, convenience, and scalability of the catalytic procedures. A brief mechanistic description is also given to introduce new readers to the topic. PMID:27308193

  17. N-Heterocyclic Carbene-Ytterbium Amide as a Recyclable Homogeneous Precatalyst for Hydrophosphination of Alkenes and Alkynes.

    PubMed

    Yuan, Jia; Hu, Hongfan; Cui, Chunming

    2016-04-11

    The N-heterocyclic carbene-ytterbium(II) amides (NHC)2Yb[N(SiMe3)2]2 (1: NHC: 1,3,4,5-tetramethylimidazo-2-ylidene (IMe4); 2: NHC: 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (IiPr)) and the NHC-stabilized rare-earth phosphide (IMe4)3Yb(PPh2)2 (3) have been synthesized and fully characterized. Complexes 1-3 are active precatalysts for the hydrophosphination of alkenes, alkynes, and dienes and exhibited much superior catalytic activity to that of the NHC-free amide (THF)2Yb[N(SiMe)2]2. Complex 1 is the most active precursor among the three complexes. In particular, complex 1 can be recycled and recovered from the reaction media after the catalytic reactions. Furthermore, it was found that complex 3 could catalyze the polymerization of styrene to yield atactic polystyrenes with low molecular weights. To the best of our knowledge, complex 1 represents the first rare-earth complex that can be recovered after catalytic reactions. PMID:26934571

  18. Immobilisation and characterisation of biocatalytic co-factor recycling enzymes, glucose dehydrogenase and NADH oxidase, on aldehyde functional ReSyn™ polymer microspheres.

    PubMed

    Twala, Busisiwe V; Sewell, B Trevor; Jordaan, Justin

    2012-05-10

    The use of enzymes in industrial applications is limited by their instability, cost and difficulty in their recovery and re-use. Immobilisation is a technique which has been shown to alleviate these limitations in biocatalysis. Here we describe the immobilisation of two biocatalytically relevant co-factor recycling enzymes, glucose dehydrogenase (GDH) and NADH oxidase (NOD) on aldehyde functional ReSyn™ polymer microspheres with varying functional group densities. The successful immobilisation of the enzymes on this new high capacity microsphere technology resulted in the maintenance of activity of ∼40% for GDH and a maximum of 15.4% for NOD. The microsphere variant with highest functional group density of ∼3500 μmol g⁻¹ displayed the highest specific activity for the immobilisation of both enzymes at 33.22 U mg⁻¹ and 6.75 U mg⁻¹ for GDH and NOD with respective loading capacities of 51% (0.51 mg mg⁻¹) and 129% (1.29 mg mg⁻¹). The immobilised GDH further displayed improved activity in the acidic pH range. Both enzymes displayed improved pH and thermal stability with the most pronounced thermal stability for GDH displayed on ReSyn™ A during temperature incubation at 65 °C with a 13.59 fold increase, and NOD with a 2.25-fold improvement at 45 °C on the same microsphere variant. An important finding is the suitability of the microspheres for stabilisation of the multimeric protein GDH.

  19. Biocatalytic synthesis of flavones and hydroxyl-small molecules by recombinant Escherichia coli cells expressing the cyanobacterial CYP110E1 gene

    PubMed Central

    2012-01-01

    Background Cyanobacteria possess several cytochrome P450s, but very little is known about their catalytic functions. CYP110 genes unique to cyanaobacteria are widely distributed in heterocyst-forming cyanobacteria including nitrogen-fixing genera Nostoc and Anabaena. We screened the biocatalytic functions of all P450s from three cyanobacterial strains of genus Nostoc or Anabaena using a series of small molecules that contain flavonoids, sesquiterpenes, low-molecular-weight drugs, and other aromatic compounds. Results Escherichia coli cells carrying each P450 gene that was inserted into the pRED vector, containing the RhFRed reductase domain sequence from Rhodococcus sp. NCIMB 9784 P450RhF (CYP116B2), were co-cultured with substrates and products were identified when bioconversion reactions proceeded. Consequently, CYP110E1 of Nostoc sp. strain PCC 7120, located in close proximity to the first branch point in the phylogenetic tree of the CYP110 family, was found to be promiscuous for the substrate range mediating the biotransformation of various small molecules. Naringenin and (hydroxyl) flavanones were respectively converted to apigenin and (hydroxyl) flavones, by functioning as a flavone synthase. Such an activity is reported for the first time in prokaryotic P450s. Additionally, CYP110E1 biotransformed the notable sesquiterpene zerumbone, anti-inflammatory drugs ibuprofen and flurbiprofen (methylester forms), and some aryl compounds such as 1-methoxy and 1-ethoxy naphthalene to produce hydroxylated compounds that are difficult to synthesize chemically, including novel compounds. Conclusion We elucidated that the CYP110E1 gene, C-terminally fused to the P450RhF RhFRed reductase domain sequence, is functionally expressed in E. coli to synthesize a robust monooxygenase, which shows promiscuous substrate specificity (affinity) for various small molecules, allowing the biosynthesis of not only flavones (from flavanones) but also a variety of hydroxyl-small molecules

  20. Synthesis and characterization of biocatalytic γ-Fe2O3@SiO2 particles as recoverable bioreactors.

    PubMed

    Vaz, A M; Serrano-Ruiz, D; Laurenti, M; Alonso-Cristobal, P; Lopez-Cabarcos, E; Rubio-Retama, J

    2014-02-01

    In this work, we present a suitable methodology to produce magnetically recoverable bioreactors based on enzymes, which are covalently attached on the surface of iron oxide@silica nanoparticles. In order to produce this system, iron oxide clusters with a mean diameter of 68 nm were covered with silica. This strategy yields spherical γ-Fe2O3@SiO2 cluster@shell nanoparticles with a mean diameter of 200 nm which present magnetic responsiveness and enhanced stability. The surface of these nanoparticles was modified into two steps with the aim to obtain carboxylic functional groups, which were activated to react with the enzyme glucose oxidase (GOx) that was thus immobilized on the surface of the nanoparticles. The objective of this chemistry at the nanoparticles interface is to produce magnetic-responsive bioreactors. The enzymatic activity was evaluated by using the recoverable bioreactors as part of an amperometric biosensor. These measurements allowed determining the stability, catalytic activity and the amount of enzyme immobilized on the surface of the nanoparticles. Furthermore, the functionalized nanoparticles can be recovered by applying an external magnetic field, which allows them to be employed in chemical processes where the recovery of the biocatalyst is important.