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Sample records for alkene metathesis catalysts

  1. Reactions of strained hydrocarbons with alkene and alkyne metathesis catalysts.

    PubMed

    Carnes, Matthew; Buccella, Daniela; Siegrist, Theo; Steigerwald, Michael L; Nuckolls, Colin

    2008-10-29

    Here we describe the metathesis reactions of a strained eight-membered ring that contains both alkene and alkyne functionality. We find that the alkyne metathesis catalyst produces polymer through a ring-opening alkyne metathesis reaction that is driven by the strain release from the monomer. The strained monomer provides unusual reactivity with ruthenium-based alkene metathesis catalysts. We isolate a discrete trimeric species a Dewar benzene derivative that is locked in this form through an unsaturated cyclophane strap. PMID:18826219

  2. 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

  3. 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.

  4. 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.

  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

    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.

  7. 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...

  8. 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.

  9. Organorhenium surface and catalytic chemistry: silica-supported alkene metathesis catalysts derived from dodecacarbonyltetrakis(. mu. -hydrido)-tetrahedro-tetrarhenium and tetrakis(tricarbonyl(. mu. -hydroxo)rhenium)

    SciTech Connect

    Kirlin, P.S.; Gates, B.C.

    1985-11-06

    Silica-supported (Re(CO)/sub 3/OH)/sub 4/ was formed by direct deposition from solution and, alternatively, by reaction of (H/sub 4/Re/sub 4/(CO)/sub 12/) with adsorbed water, as shown by comparisons of infrared, ultraviolet, and /sup 1/H NMR spectra of the surface and of the complex extracted into tetrahydrofuran. The supported (Re(CO)/sub 3/OH)/sub 4/ is inferred to be hydrogen bonded to surface -OH groups; its chemistry is similar to that of (Re(CO)/sub 3/OH)/sub 4/ in solution, but new reactivity is induced by the surface, with adsorbed (HRe/sub 3/(CO)/sub 14/) being formed from (Re(CO)/sub 3/OH)/sub 4/ (or (H/sub 3/Re/sub 3/(CO)/sub 12/)) in the presence of CO at 150/sup 0/C. The supported (Re(CO)/sub 3/OH)/sub 4/ is the precursor of a highly active and stable catalyst for the metathesis of propene: the activity is associated with a small fraction of the rhenium in a higher oxidation state. The oxidation to form the active species takes place under conditions so mild that more highly oxidized species, which are active for alkene polymerization and coke formation, are not formed, and the catalyst is consequently resistant to deactivation. 38 references, 10 figures, 2 tables.

  10. Beyond catalyst deactivation: cross-metathesis involving olefins containing N-heteroaromatics

    PubMed Central

    Lafaye, Kevin; Bosset, Cyril; Nicolas, Lionel

    2015-01-01

    Summary Alkenes containing N-heteroaromatics are known to be poor partners in cross-metathesis reactions, probably due to catalyst deactivation caused by the presence of a nitrogen atom. However, some examples of ring-closing and cross-metathesis involving alkenes that incorporate N-heteroaromatics can be found in the literature. In addition, recent mechanistic studies have focused on the rationalization of nitrogen-induced catalysts deactivation. The purpose of this mini-review is to give a brief overview of successful metathesis reactions involving olefins containing N-heteroaromatics in order to delineate some guidelines for the use of these challenging substrates in metathesis reactions. PMID:26664645

  11. Highly Selective Ruthenium Metathesis Catalysts for Ethenolysis

    PubMed Central

    Thomas, Renee M.; Keitz, Benjamin K.; Champagne, Timothy M.; Grubbs, Robert H.

    2011-01-01

    N-aryl, N-alkyl N-heterocyclic carbene (NHC) ruthenium metathesis catalysts are highly selective toward the ethenolysis of methyl oleate, giving selectivity as high as 95% for the kinetic, ethenolysis products over the thermodynamic, self-metathesis products. The examples described herein represent some of the most selective NHC-based ruthenium catalysts for ethenolysis reactions to date. Furthermore, many of these catalysts show unusual preference and stability toward propagating as a methylidene species, and provide good yields and turnover numbers (TONs) at relatively low catalyst loading (<500 ppm). A catalyst comparison showed that ruthenium complexes bearing sterically hindered NHC substituents afforded greater selectivity and stability, and exhibited longer catalyst lifetime during reactions. Comparative analysis of the catalyst preference for kinetic versus thermodynamic product formation was achieved via evaluation of their steady-state conversion in the cross-metathesis reaction of terminal olefins. These results coincided with the observed ethenolysis selectivities, in which the more selective catalysts reach a steady-state characterized by lower conversion to cross-metathesis products compared to less selective catalysts, which show higher conversion to cross-metathesis products. PMID:21510645

  12. Highly active water-soluble olefin metathesis catalyst.

    PubMed

    Hong, Soon Hyeok; Grubbs, Robert H

    2006-03-22

    A novel water-soluble ruthenium olefin metathesis catalyst supported by a poly(ethylene glycol) conjugated saturated 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene ligand is reported. The catalyst displays improved activity in ring-opening metathesis polymerization, ring-closing metathesis, and cross-metathesis reactions in aqueous media. PMID:16536510

  13. Nitro-Grela-type complexes containing iodides – robust and selective catalysts for olefin metathesis under challenging conditions

    PubMed Central

    Tracz, Andrzej; Matczak, Mateusz; Urbaniak, Katarzyna

    2015-01-01

    Summary Iodide-containing nitro-Grela-type catalysts have been synthesized and applied to ring closing metathesis (RCM) and cross metathesis (CM) reactions. These new catalysts have exhibited improved efficiency in the transformation of sterically, non-demanding alkenes. Additional steric hindrance in the vicinity of ruthenium related to the presence of iodides ensures enhanced catalyst stability. The benefits are most apparent under challenging conditions, such as very low reaction concentrations, protic solvents or with the occurrence of impurities. PMID:26664602

  14. Atomistic Description of Reaction Intermediates for Supported Metathesis Catalysts Enabled by DNP SENS.

    PubMed

    Ong, Ta-Chung; Liao, Wei-Chih; Mougel, Victor; Gajan, David; Lesage, Anne; Emsley, Lyndon; Copéret, Christophe

    2016-04-01

    Obtaining detailed structural information of reaction intermediates remains a key challenge in heterogeneous catalysis because of the amorphous nature of the support and/or the support interface that prohibits the use of diffraction-based techniques. Combining isotopic labeling and dynamic nuclear polarization (DNP) increases the sensitivity of surface enhanced solid-state NMR spectroscopy (SENS) towards surface species in heterogeneous alkene metathesis catalysts; this in turn allows direct determination of the bond connectivity and measurement of the carbon-carbon bond distance in metallacycles, which are the cycloaddition intermediates in the alkene metathesis catalytic cycle. Furthermore, this approach makes possible the understanding of the slow initiation and deactivation steps in these heterogeneous metathesis catalysts. PMID:26953812

  15. Metathesis catalysts and methods thereof

    DOEpatents

    Schrock, Richard Royce; Yuan, Jian

    2016-04-19

    The present application provides, among other things, novel compounds for metathesis reactions, and methods for preparing and using provided compounds. In some embodiments, the present invention provides compounds having the structure of formula I or II. In some embodiments, the present invention provides methods for preparing a compound of formula I or II. In some embodiments, the present invention provides methods for using a provided compound. In some embodiments, a provided compound is useful for stereoselective ring-opening metathesis polymerization. In some embodiments, a provided metathesis method provides cis and/or isotactic polymers.

  16. Cationic Silica-Supported N-Heterocyclic Carbene Tungsten Oxo Alkylidene Sites: Highly Active and Stable Catalysts for Olefin Metathesis.

    PubMed

    Pucino, Margherita; Mougel, Victor; Schowner, Roman; Fedorov, Alexey; Buchmeiser, Michael R; Copéret, Christophe

    2016-03-18

    Designing supported alkene metathesis catalysts with high activity and stability is still a challenge, despite significant advances in the last years. Described herein is the combination of strong σ-donating N-heterocyclic carbene ligands with weak σ-donating surface silanolates and cationic tungsten sites leading to highly active and stable alkene metathesis catalysts. These well-defined silica-supported catalysts, [(≡SiO)W(=O)(=CHCMe2 Ph)(IMes)(OTf)] and [(≡SiO)W(=O)(=CHCMe2 Ph)(IMes)(+) ][B(Ar(F) )4 (-) ] [IMes=1,3-bis(2,4,6-trimethylphenyl)-imidazol-2-ylidene, B(Ar(F) )4 =B(3,5-(CF3 )2 C6 H3 )4 ] catalyze alkene metathesis, and the cationic species display unprecedented activity for a broad range of substrates, especially for terminal olefins with turnover numbers above 1.2 million for propene. PMID:26928967

  17. Thermally Stable, Latent Olefin Metathesis Catalysts.

    PubMed

    Thomas, Renee M; Fedorov, Alexey; Keitz, Benjamin K; Grubbs, Robert H

    2011-12-26

    Highly thermally stable N-aryl,N-alkyl N-heterocyclic carbene (NHC) ruthenium catalysts were designed and synthesized for latent olefin metathesis. These catalysts showed excellent latent behavior toward metathesis reactions, whereby the complexes were inactive at ambient temperature and initiated at elevated temperatures, a challenging property to achieve with second generation catalysts. A sterically hindered N-tert-butyl substituent on the NHC ligand of the ruthenium complex was found to induce latent behavior toward cross-metathesis reactions, and exchange of the chloride ligands for iodide ligands was necessary to attain latent behavior during ring-opening metathesis polymerization (ROMP). Iodide-based catalysts showed no reactivity toward ROMP of norbornene-derived monomers at 25 °C, and upon heating to 85 °C gave complete conversion of monomer to polymer in less than 2 hours. All of the complexes were very stable to air, moisture, and elevated temperatures up to at least 90 °C, and exhibited a long catalyst lifetime in solution at elevated temperatures. PMID:22282652

  18. Recent Applications of Alkene Metathesis in Fine Chemical Synthesis

    NASA Astrophysics Data System (ADS)

    Bicchielli, Dario; Borguet, Yannick; Delaude, Lionel; Demonceau, Albert; Dragutan, Ileana; Dragutan, Valerian; Jossifov, Christo; Kalinova, Radostina; Nicks, François; Sauvage, Xavier

    During the last decade or so, the emergence of the metathesis reaction in organic synthesis has revolutionised the strategies used for the construction of complex molecular structures. Olefin metathesis is indeed particularly suited for the construction of small open-chain molecules and macrocycles using crossmetathesis and ring-closing metathesis, respectively. These reactions serve, inter alia, as key steps in the synthesis of various agrochemicals and pharmaceuticals such as macrocyclic peptides, cyclic sulfonamides, novel macrolides, or insect pheromones. The present chapter is aiming at illustrating the great synthetic potential of metathesis reactions. Shortcomings, such as the control of olefin geometry and the unpredictable effect of substituents on the reacting olefins, will also be addressed. Examples to be presented include epothilones, amphidinolides, spirofungin A, and archazolid. Synthetic approaches involving silicon-tethered ring-closing metathesis, relay ring-closing metathesis, sequential reactions, domino as well as tandem metathesis reactions will also be illustrated.

  19. 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

  20. 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

  1. Cross-metathesis reaction of α- and β-vinyl C-glycosides with alkenes

    PubMed Central

    Šnajdr, Ivan; Parkan, Kamil; Hessler, Filip

    2015-01-01

    Summary 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

  2. Profluorescent substrates for the screening of olefin metathesis catalysts

    PubMed Central

    Reuter, Raphael

    2015-01-01

    Summary Herein we report on a 96-well plate assay based on the fluorescence resulting from the ring-closing metathesis of two profluorophoric substrates. To demonstrate the validity of the approach, four commercially available ruthenium-metathesis catalysts were evaluated in six different solvents. The results from the fluorescent assay agree well with HPLC conversions, validating the usefulness of the approach. PMID:26664607

  3. Low Temperature Activation of Supported Metathesis Catalysts by Organosilicon Reducing Agents

    PubMed Central

    2016-01-01

    Alkene metathesis is a widely and increasingly used reaction in academia and industry because of its efficiency in terms of atom economy and its wide applicability. This reaction is notably responsible for the production of several million tons of propene annually. Such industrial processes rely on inexpensive silica-supported tungsten oxide catalysts, which operate at high temperatures (>350 °C), in contrast with the mild room temperature reaction conditions typically used with the corresponding molecular alkene metathesis homogeneous catalysts. This large difference in the temperature requirements is generally thought to arise from the difficulty in generating active sites (carbenes or metallacyclobutanes) in the classical metal oxide catalysts and prevents broader applicability, notably with functionalized substrates. We report here a low temperature activation process of well-defined metal oxo surface species using organosilicon reductants, which generate a large amount of active species at only 70 °C (0.6 active sites/W). This high activity at low temperature broadens the scope of these catalysts to functionalized substrates. This activation process can also be applied to classical industrial catalysts. We provide evidence for the formation of a metallacyclopentane intermediate and propose how the active species are formed. PMID:27610418

  4. Low Temperature Activation of Supported Metathesis Catalysts by Organosilicon Reducing Agents.

    PubMed

    Mougel, Victor; Chan, Ka-Wing; Siddiqi, Georges; Kawakita, Kento; Nagae, Haruki; Tsurugi, Hayato; Mashima, Kazushi; Safonova, Olga; Copéret, Christophe

    2016-08-24

    Alkene metathesis is a widely and increasingly used reaction in academia and industry because of its efficiency in terms of atom economy and its wide applicability. This reaction is notably responsible for the production of several million tons of propene annually. Such industrial processes rely on inexpensive silica-supported tungsten oxide catalysts, which operate at high temperatures (>350 °C), in contrast with the mild room temperature reaction conditions typically used with the corresponding molecular alkene metathesis homogeneous catalysts. This large difference in the temperature requirements is generally thought to arise from the difficulty in generating active sites (carbenes or metallacyclobutanes) in the classical metal oxide catalysts and prevents broader applicability, notably with functionalized substrates. We report here a low temperature activation process of well-defined metal oxo surface species using organosilicon reductants, which generate a large amount of active species at only 70 °C (0.6 active sites/W). This high activity at low temperature broadens the scope of these catalysts to functionalized substrates. This activation process can also be applied to classical industrial catalysts. We provide evidence for the formation of a metallacyclopentane intermediate and propose how the active species are formed. PMID:27610418

  5. Nonproductive Events in Ring-Closing Metathesis using Ruthenium Catalysts

    PubMed Central

    Stewart, Ian C.; Keitz, Benjamin K.; Kuhn, Kevin M.; Thomas, Renee M.

    2010-01-01

    The relative TONs of productive and nonproductive metathesis reactions of diethyl diallylmalonate are compared for eight different ruthenium-based catalysts. Nonproductive cross metathesis is proposed to involve a chain-carrying ruthenium methylidene. A second more-challenging substrate (dimethyl allylmethylallylmalonate) that forms a trisubstituted olefin product is used to further delineate the effect of catalyst structure on the relative efficiencies of these processes. A steric model is proposed to explain the observed trends. PMID:20518557

  6. Comparative investigation of ruthenium-based metathesis catalysts bearing N-heterocyclic carbene (NHC) ligands.

    PubMed

    Fürstner, A; Ackermann, L; Gabor, B; Goddard, R; Lehmann, C W; Mynott, R; Stelzer, F; Thiel, O R

    2001-08-01

    Exchange of one PCy3 unit of the classical Grubbs catalyst 1 by N-heterocyclic carbene (NHC) ligands leads to "second-generation" metathesis catalysts of superior reactivity and increased stability. Several complexes of this type have been prepared and fully characterized, six of them by X-ray crystallography. These include the unique chelate complexes 13 and 14 in which the NHC- and the Ru-CR entities are tethered to form a metallacycle. A particularly favorable design feature is that the reactivity of such catalysts can be easily adjusted by changing the electronic and steric properties of the NHC ligands. The catalytic activity also strongly depends on the solvent used; NMR investigations provide a tentative explanation of this effect. Applications of the "second-generation" catalysts to ring closing alkene metathesis and intramolecular enyne cycloisomerization reactions provide insights into their catalytic performance. From these comparative studies it is deduced that no single catalyst is optimal for different types of applications. The search for the most reactive catalyst for a specific transformation is facilitated by IR thermography allowing a rapid and semi-quantitative ranking among a given set of catalysts. PMID:11531110

  7. Ruthenium olefin metathesis catalysts featuring unsymmetrical N-heterocyclic carbenes.

    PubMed

    Paradiso, Veronica; Bertolasi, Valerio; Costabile, Chiara; Grisi, Fabia

    2016-01-14

    New ruthenium Grubbs' and Hoveyda-Grubbs' second generation catalysts bearing N-alkyl/N-isopropylphenyl N-heterocyclic carbene (NHC) ligands with syn or anti backbone configuration were obtained and compared in model olefin metathesis reactions. Different catalytic efficiencies were observed depending on the size of the N-alkyl group (methyl or cyclohexyl) and on the backbone configuration. The presence of an N-cyclohexyl substituent determined the most significant reactivity differences between catalysts with syn or anti phenyl groups on the backbone. In particular, anti catalysts proved highly efficient, especially in the ring-closing metathesis (RCM) of encumbered diolefins, while syn catalysts showed low efficiency in the RCM of less hindered diolefins. This peculiar behavior, rationalized through DFT studies, was found to be related to the high propensity of these catalysts to give nonproductive metathesis events. Enantiopure anti catalysts were also tested in asymmetric metathesis reactions, where moderate enantioselectivities were observed. The steric and electronic properties of unsymmetrical NHCs with the N-cyclohexyl group were then evaluated using the corresponding rhodium complexes. While steric factors proved unimportant for both syn and anti NHCs, a major electron-donating character was found for the unsymmetrical NHC with anti phenyl substituents on the backbone. PMID:26608162

  8. Low catalyst loadings in olefin metathesis: synthesis of nitrogen heterocycles by ring-closing metathesis.

    PubMed

    Kuhn, Kevin M; Champagne, Timothy M; Hong, Soon Hyeok; Wei, Wen-Hao; Nickel, Andrew; Lee, Choon Woo; Virgil, Scott C; Grubbs, Robert H; Pederson, Richard L

    2010-03-01

    A series of ruthenium catalysts have been screened under ring-closing metathesis (RCM) conditions to produce five-, six-, and seven-membered carbamate-protected cyclic amines. Many of these catalysts demonstrated excellent RCM activity and yields with as low as 500 ppm catalyst loadings. RCM of the five-membered carbamate series could be run neat, the six-membered carbamate series could be run at 1.0 M, and the seven-membered carbamate series worked best at 0.2-0.05 M. PMID:20141172

  9. Highly Active Multidentate Ligand-Based Alkyne Metathesis Catalysts.

    PubMed

    Du, Ya; Yang, Haishen; Zhu, Chengpu; Ortiz, Michael; Okochi, Kenji D; Shoemaker, Richard; Jin, Yinghua; Zhang, Wei

    2016-06-01

    Alkyne metathesis catalysts composed of molybdenum(VI) propylidyne and multidentate tris(2-hydroxylbenzyl)methane ligands have been developed, which exhibit excellent stability (remains active in solution for months at room temperature), high activity, and broad functional-group tolerance. The homodimerization and cyclooligomerization of monopropynyl or dipropynyl substrates, including challenging heterocycle substrates (e.g., pyridine), proceed efficiently at 40-55 °C in a closed system. The ligand structure and catalytic activity relationship has been investigated, which shows that the ortho groups of the multidentate phenol ligands are critical to the stability and activity of such a catalyst system. PMID:27113640

  10. Low catalyst loading in ring-closing metathesis reactions.

    PubMed

    Kadyrov, Renat

    2013-01-14

    An efficient procedure is described for ring-closing metathesis reactions. A conversion of 95% for diethyl diallylmalonate in dilute solution could be achieved within a few minutes, reaching TOF = 4173 min(-1), with very low loading of commercially available Ru catalysts that contained unsaturated NHC ligands. In general, only 50 to 250 ppm of the catalyst is required to achieve near-quantitative conversion into a broad variety of 5-16-membered heterocyclic compounds. The practicality of this procedure was illustrated in the synthesis of 5-8-membered N-tert-butoxycarbonyl (N-Boc)- and N-para-toluenesulfonyl (N-Ts)-protected cyclic amines and 9-16-membered lactones. The synthesis of macrocyclic proline-based lactams required slightly higher catalyst loadings. Along with monocyclic products, oligomeric byproducts, mostly cyclodimers, were isolated and characterized. PMID:23180647

  11. A Ruthenium Catalyst for Olefin Metathesis Featuring an Anti-Bredt N-Heterocyclic Carbene Ligand

    PubMed Central

    Martin, David; Marx, Vanessa M.

    2016-01-01

    A ruthenium complex bearing an “anti-Bredt” N-heterocyclic carbene was synthesized, characterized and evaluated as a catalyst for olefin metathesis. Good conversions were observed at room temperature for the formation of di- and tri-substituted olefins by ring-closing metathesis. It also allowed for the ring-opening metathesis polymerization of cyclooctadiene, as well as for the cross-metathesis of cis-1,4-diacetoxy-2-butene with allyl-benzene, with enhanced Z/E kinetic selectivity over classical NHC-based catalysts.

  12. The generation of efficient supported (Heterogeneous) olefin metathesis catalysts

    SciTech Connect

    Grubbs, Robert H

    2013-04-05

    Over the past decade, a new family of homogeneous metathesis catalysts has been developed that will tolerate most organic functionalities as well as water and air. These homogeneous catalysts are finding numerous applications in the pharmaceutical industry as well as in the production of functional polymers. In addition the catalysts are being used to convert seed oils into products that can substitute for those that are now made from petroleum products. Seed oils are unsaturated, contain double bonds, and are a ready source of linear hydrocarbon fragments that are specifically functionalized. To increase the number of applications in the area of biomaterial conversion to petrol chemicals, the activity and efficiency of the catalysts need to be as high as possible. The higher the efficiency of the catalysts, the lower the cost of the conversion and a larger number of practical applications become available. Active supported catalysts were prepared and tested in the conversion of seed oils and other important starting materials. The outcome of the work was successful and the technology has been transferred to a commercial operation to develop viable applications of the discovered systems. A biorefinery that converts seed oils is under construction in Indonesia. The catalysts developed in this study will be considered for the next generation of operations.

  13. 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.

  14. Z-Selective Ruthenium Metathesis Catalysts: Comparison of Nitrate and Nitrite X-type Ligands

    PubMed Central

    Pribisko, Melanie A.; Ahmed, Tonia S.; Grubbs, Robert H.

    2014-01-01

    Two new Ru-based metathesis catalysts, 3 and 4, have been synthesized for the purpose of comparing their catalytic properties to those of their cis-selective nitrate analogues, 1 and 2. Although catalysts 3 and 4 exhibited slower initiation rates than 1 and 2, they maintained high cis-selectivity in homodimerization and ring-opening metathesis polymerization reactions. Furthermore, the nitrite catalysts displayed higher cis-selectivity than 2 for ring-opening metathesis polymerizations, and 4 delivered higher yields of polymer. PMID:25484484

  15. 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%.

  16. 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%.

  17. The Discovery of Quinoxaline-Based Metathesis Catalysts from Synthesis of Grazoprevir (MK-5172).

    PubMed

    Williams, Michael J; Kong, Jongrock; Chung, Cheol K; Brunskill, Andrew; Campeau, Louis-Charles; McLaughlin, Mark

    2016-05-01

    Olefin metathesis (OM) is a reliable and practical synthetic methodology for challenging carbon-carbon bond formations. While existing catalysts can effect many of these transformations, the synthesis and development of new catalysts is essential to increase the application breadth of OM and to achieve improved catalyst activity. The unexpected initial discovery of a novel olefin metathesis catalyst derived from synthetic efforts toward the HCV therapeutic agent grazoprevir (MK-5172) is described. This initial finding has evolved into a class of tunable, shelf-stable ruthenium OM catalysts that are easily prepared and exhibit unique catalytic activity. PMID:27123552

  18. Tandem Ru-alkylidene-catalysed cross metathesis/hydrogenation: synthesis of lipophilic amino acids.

    PubMed

    Wang, Zhen J; Spiccia, Nicolas D; Jackson, W Roy; Robinson, Andrea J

    2013-08-01

    Highly efficient synthesis of lipidic amino acids can be achieved via Ru-alkylidene-catalysed cross metathesis of long chain alkenes with commercially available allylglycine. The resultant unsaturated analogues can be then optionally hydrogenated under mild reaction conditions by using the spent metathesis catalyst. PMID:23733491

  19. Ruthenium-based olefin metathesis catalysts bearing pH-responsive ligands: External control of catalyst solubility and activity

    NASA Astrophysics Data System (ADS)

    Balof, Shawna Lynn

    2011-12-01

    Sixteen novel, Ru-based olefin metathesis catalysts bearing pH responsive ligands were synthesized. The pH-responsive groups employed with these catalysts included dimethylamino (NMe2) modified NHC ligands as well as N-donor dimethylaminopyridine (DMAP) and 3-(o-pyridyl)propylidene ligands. These pH-responsive ligands provided the means by which the solubility and/or activity profiles of the catalysts produced could be controlled via acid addition. The main goal of this dissertation was to design catalyst systems capable of performing ring opening metathesis (ROMP) and ring closing metathesis (RCM) reactions in both organic and aqueous media. In an effort to quickly gain access to new catalyst structures, a template synthesis for functionalized NHC ligand precursors was designed, in addition to other strategies, to obtain ligand precursors with ancillary NMe2 groups. Kinetic studies for the catalysts produced from these precursors showed external control of catalyst solubility was afforded via protonation of the NMe2 groups of their NHC ligands. Additionally, this protonation afforded external control of catalyst propagation rates for several catalysts. This is the first known independent external control for the propagation rates of ROMP catalysts. The incorporation of pH-responsive N-donor ligands into catalyst structures also provided the means for the external control of metathesis activity, as the protonation of these ligands resulted in an increased initiation rate based on their fast and irreversible dissociation from the metal center. The enhanced external control makes these catalysts applicable to a wide range of applications, some of which have been explored by us and/or through collaboration. Three of the catalysts designed showed remarkable metathesis activity in aqueous media. These catalysts displayed comparable RCM activity in aqueous media to a class of water-soluble catalysts reported by Grubbs et al., considered to be the most active catalyst for

  20. Bond Energies in Models of the Schrock Metathesis Catalyst

    SciTech Connect

    Vasiliu, Monica; Li, Shenggang; Arduengo, Anthony J.; Dixon, David A.

    2011-06-23

    Heats of formation, adiabatic and diabatic bond dissociation energies (BDEs) of the model Schrock-type metal complexes M(NH)(CRR)(OH)₂ (M = Cr, Mo, W; CRR = CH₂, CHF, CF₂) and MO₂(OH)₂ compounds, and Brønsted acidities and fluoride affinities for the M(NH)(CH₂)(OH) ₂ transition metal complexes are predicted using high level CCSD(T) calculations. The metallacycle intermediates formed by reaction of C₂H4 with M(NH)-(CH₂)(OH)2 and MO₂(OH)₂ are investigated at the same level of theory. Additional corrections were added to the complete basis set limit to obtain near chemical accuracy ((1 kcal/mol). A comparison between adiabatic and diabatic BDEs is made and provides an explanation of trends in the BDEs. Electronegative groups bonded on the carbenic carbon lead to less stable Schrock-type complexes as the adiabatic BDEs ofMdCF₂ andMdCHF bonds are much lower than theMdCH₂ bonds. The Cr compounds have smaller BDEs than theWorMo complexes and should be less stable. Different M(NH)(OH)₂(C₃H₆) and MO(OH)₂(OC₂H4) metallacycle intermediates are investigated, and the lowest-energy metallacycles have a square pyramidal geometry. The results show that consideration of the singlet_triplet splitting in the carbene in the initial catalyst as well as in the metal product formed by the retro [2+2] cycloaddition is a critical component in the design of an effective olefin metathesis catalyst in terms of the parent catalyst and the groups being transferred.

  1. Diphenylamido Precursors to Bisalkoxide Molybdenum Olefin Metathesis Catalysts

    PubMed Central

    Sinha, Amritanshu; Müller, Peter; Hoveyda, Amir H.

    2008-01-01

    We have found that Mo(NAr)(CHR′)(NPh2)2 (R′ = t-Bu or CMe2Ph) and Mo(NAr′)(CHCMe2Ph)(NPh2)2 (Ar = 2,6-i-Pr2C6H3; Ar′ = 2,6-Me2C6H3) can be prepared through addition of two equivalents of LiNPh2 to Mo(NR″)(CHR′)(OTf)2(dme) species (R″ = Ar or Ar′ dme = 1,2-dimethoxyethane), although yields are low. A high yield route consists of addition of LiNPh2 to bishexafluro-t-butoxide species. An X-ray structure of Mo(NAr)(CHCMe2Ph)(NPh2)2 reveals that the two diphenylamido groups are oriented in a manner that allows an 18 electron count to be achieved. The diphenylamido complexes react readily with t-BuOH and (CF3)2MeCOH, but not readily with the sterically demanding biphenol H2[Biphen] (Biphen2- = 3,3′-Di-t-butyl-5,5′,6,6′-tetramethyl-1,1′-Biphenyl-2,2′-diolate). The diphenylamido complexes do react with various 3,3′-disubstituted binaphthols to yield binaphtholate catalysts that can be prepared in situ and employed for a simple asymmetric ring-closing metathesis reaction. In several cases conversions and enantioselectivities were comparable to reactions in which isolated catalysts were employed. PMID:19030118

  2. Nobel Chemistry in the Laboratory: Synthesis of a Ruthenium Catalyst for Ring-Closing Olefin Metathesis--An Experiment for the Advanced Inorganic or Organic Laboratory

    ERIC Educational Resources Information Center

    Greco, George E.

    2007-01-01

    An experiment for the upper-level undergraduate laboratory is described in which students synthesize a ruthenium olefin metathesis catalyst, then use the catalyst to carry out the ring-closing metathesis of diethyl diallylmalonate. The olefin metathesis reaction was the subject of the 2005 Nobel Prize in chemistry. The catalyst chosen for this…

  3. Role of Tricoordinate Al Sites in CH3ReO3/Al2O3 Olefin Metathesis Catalysts.

    PubMed

    Valla, Maxence; Wischert, Raphael; Comas-Vives, Aleix; Conley, Matthew P; Verel, René; Copéret, Christophe; Sautet, Philippe

    2016-06-01

    Re2O7 supported on γ-alumina is an alkene metathesis catalyst active at room temperature, compatible with functional groups, but the exact structures of the active sites are unknown. Using CH3ReO3/Al2O3 as a model for Re2O7/Al2O3, we show through a combination of reactivity studies, in situ solid-state NMR, and an extensive series of DFT calculations, that μ-methylene structures (Al-CH2-ReO3-Al) containing a Re═O bound to a tricoordinated Al (AlIII) and CH2 bound to a four-coordinated Al (AlIVb) are the precursors of the most active sites for olefin metathesis. The resting state of CH3ReO3/Al2O3 is a distribution of μ-methylene species formed by the activation of the C-H bond of CH3ReO3 on different surface Al-O sites. In situ reaction with ethylene results in the formation of Re metallacycle intermediates, which were studied in detail through a combination of solid-state NMR experiments, using labeled ethylene, and DFT calculations. In particular, we were able to distinguish between metallacycles in TBP (trigonal-bipyramidal) and SP (square-pyramidal) geometry, the latter being inactive and detrimental to catalytic activity. The SP sites are more likely to be formed on other Al sites (AlIVa/AlIVa). Experimentally, the activity of CH3ReO3/Al2O3 depends on the activation temperature of alumina; catalysts activated at or above 500 °C contain more active sites than those activated at 300 °C. We show that the dependence of catalytic activity on the Al2O3 activation temperature is related to the quantity of available AlIII-defect sites and adsorbed H2O. PMID:27140286

  4. Olefin Ring Closing Metathesis and Hydrosilylation Reaction in Aqueous Medium by Grubbs Second Generation Ruthenium Catalyst

    EPA Science Inventory

    The Grubbs second generation ruthenium catalyst was shown to catalyze various olefin ring closing metathesis and hydrosilylation reactions in aqueous medium. Reactions proceeded in pure water without any additives or co-solvents, in a short period of time. We found that inhomogen...

  5. 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...

  6. Ruthenium indenylidene “1st generation” olefin metathesis catalysts containing triisopropyl phosphite

    PubMed Central

    Guidone, Stefano; Nahra, Fady; Slawin, Alexandra M Z

    2015-01-01

    Summary The reaction of triisopropyl phosphite with phosphine-based indenylidene pre-catalysts affords “1st generation” cis-complexes. These have been used in olefin metathesis reactions. The cis-Ru species exhibit noticeable differences with the trans-Ru parent complexes in terms of structure, thermal stability and reactivity. Experimental data underline the importance of synergistic effects between phosphites and L-type ligands. PMID:26425210

  7. Designing Sequence Selectivity into a Ring-Opening Metathesis Polymerization Catalyst.

    PubMed

    Chen, Peter

    2016-05-17

    The development of a chemoselective catalyst for the sequence-selective copolymerization of two cycloolefins by ring-opening metathesis polymerization is described, starting with the mechanistic work that established the structure of the key metallacyclobutane intermediate. Experimental and computational investigations converged to a conclusion that the lowest energy metallacyclobutane intermediate in the ruthenium carbene-catalyzed metathesis reaction had the four-membered ring trans to the phosphine or NHC ligand. The trans-metallacyclobutane structure, for the case of a degenerate metathesis reaction catalyzed by a Grubbs first-generation complex, necessitated a rotation of the 3-fold symmetric tricyclohexylphosphine ligand, with respect to the 2-fold symmetric metallacyclobutane substructure. The degeneracy could be lifted by constraining the rotation. Lifting the degeneracy created the possibility of chemoselectivity. This mechanistic work led to a concept for the "tick-tock" catalyst for a chemoselective, alternating copolymerization of cyclooctene and norbornene from a mixture of the two monomers. The design concept could be post facto elaborated in terms of stereochemistry and topological theory, both viewpoints providing deeper insight into the design of selectivity into the catalytic reaction. The iterative interaction of theory and experiment provided the basis for the rational design and optimization of a new selectivity into an existing catalytic system with decidedly modest structural modifications of the original carbene complex. PMID:27105333

  8. Poly(fluoroalkyl acrylate)-bound ruthenium carbene complex: a fluorous and recyclable catalyst for ring-closing olefin metathesis.

    PubMed

    Yao, Qingwei; Zhang, Yiliang

    2004-01-14

    The synthesis of a fluorous olefin metathesis catalyst derived from the Grubbs second-generation ruthenium carbene complex is described. The air stable fluorous polymer-bound ruthenium carbene complex 1 shows high reactivity in effecting the ring-closing metathesis of a broad spectrum of diene and enyne substrates leading to the formation of di-, tri-, and tetrasubstituted cyclic olefins in minimally fluorous solvent systems (PhCF3/CH2Cl2, 1:9-1:49 v/v). The catalyst can be readily separated from the reaction mixture by fluorous extraction with FC-72 and repeatedly reused. The practical advantage offered by the fluorous catalyst is demonstrated by its sequential use in up to five different metathesis reactions. PMID:14709066

  9. Effective immobilisation of a metathesis catalyst bearing an ammonium-tagged NHC ligand on various solid supports.

    PubMed

    Skowerski, Krzysztof; Białecki, Jacek; Czarnocki, Stefan J; Żukowska, Karolina; Grela, Karol

    2016-01-01

    An ammonium-tagged ruthenium complex, 8, was deposited on several widely available commercial solid materials such as silica gel, alumina, cotton, filter paper, iron powder or palladium on carbon. The resulting catalysts were tested in toluene or ethyl acetate, and found to afford metathesis products in high yield and with extremely low ruthenium contamination. Depending on the support used, immobilised catalyst 8 shows also additional traits, such as the possibility of being magnetically separated or the use for metathesis and subsequent reduction of the obtained double bond in one pot. PMID:26877803

  10. Effective immobilisation of a metathesis catalyst bearing an ammonium-tagged NHC ligand on various solid supports

    PubMed Central

    Białecki, Jacek; Czarnocki, Stefan J; Żukowska, Karolina

    2016-01-01

    Summary An ammonium-tagged ruthenium complex, 8, was deposited on several widely available commercial solid materials such as silica gel, alumina, cotton, filter paper, iron powder or palladium on carbon. The resulting catalysts were tested in toluene or ethyl acetate, and found to afford metathesis products in high yield and with extremely low ruthenium contamination. Depending on the support used, immobilised catalyst 8 shows also additional traits, such as the possibility of being magnetically separated or the use for metathesis and subsequent reduction of the obtained double bond in one pot. PMID:26877803

  11. Phosphotungstic acid supported on magnetic nanoparticles as an efficient reusable catalyst for epoxidation of alkenes

    SciTech Connect

    Kooti, M.; Afshari, M.

    2012-11-15

    Highlights: ► Phosphotungstic acid supported on functionalized cobalt ferrite was prepared. ► Silica coated cobalt ferrite nanoparticles were used as support. ► This composite was successfully used as catalyst for epoxidation of alkenes. ► Oxidation reactions were carried out in the presence of t-BuOOH as oxidant. ► The catalyst can be readily separated from solution by magnetic field. -- Abstract: A new magnetically separable catalyst consisting of phosphotungstic acid supported on imidazole functionalized silica coated cobalt ferrite nanoparticles was prepared. The synthesized catalyst was characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR), and inductively coupled plasma atomic emission spectroscopy (ICP-AES). This immobilized phosphotungstic acid was shown to be an efficient heterogeneous catalyst for the epoxidation of various alkenes using tert-butylhydroperoxide (t-BuOOH) as oxidant. The catalyst is readily recovered by simple magnetic decantation and can be recycled several times with no significant loss of catalytic activity.

  12. Highly Tactic Cyclic Polynorbornene: Stereoselective Ring Expansion Metathesis Polymerization of Norbornene Catalyzed by a New Tethered Tungsten-Alkylidene Catalyst.

    PubMed

    Gonsales, Stella A; Kubo, Tomohiro; Flint, Madison K; Abboud, Khalil A; Sumerlin, Brent S; Veige, Adam S

    2016-04-20

    The tungsten alkylidyne [(t)BuOCO]W≡C((t)Bu) (THF)2 (1) reacts with CO2, leading to complete cleavage of one C═O bond, followed by migratory insertion to generate the tungsten-oxo alkylidene 2. Complex 2 is the first catalyst to polymerize norbornene via ring expansion metathesis polymerization to yield highly cis-syndiotactic cyclic polynorbornene. PMID:27043711

  13. Design and Stereoselective Preparation of a New Class of Chiral Olefin Metathesis Catalysts and Application to Enantioselective Synthesis of Quebrachamine: Catalyst Development Inspired by Natural Product Synthesis

    PubMed Central

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

    2010-01-01

    A total synthesis of the Aspidosperma alkaloid quebrachamine in racemic form is first described. A key catalytic ring-closing metathesis of an achiral triene is used to establish the all-carbon quaternary stereogenic center and the tetracyclic structure of the natural product; the catalytic transformation proceeds with reasonable efficiency through the use of existing achiral Ru or Mo catalysts. Ru- or Mo-based chiral olefin metathesis catalysts have proven to be inefficient and entirely nonselective in cases where the desired product is observed. In the present study, the synthesis route thus serves as a platform for the discovery of new olefin metathesis catalysts that allow for efficient completion of an enantioselective synthesis of quebrachamine. Accordingly, on the basis of mechanistic principles, stereogenic-at-Mo complexes bearing only monodentate ligands have been designed. The new catalysts provide significantly higher levels of activity than observed with the previously reported Ru- or Mo-based complexes. Enantiomerically enriched chiral alkylidenes are generated through diastereoselective reactions involving achiral Mo-based bispyrrolides and enantiomerically pure silyl-protected binaphthols. Such chiral catalysts initiate the key enantioselective ring-closing metathesis step in the total synthesis of quebrachamine efficiently (1 mol % loading, 22 °C, 1 h, >98% conversion, 84% yield) and with high selectivity (98:2 er, 96% ee). PMID:19113867

  14. Olefin metathesis for effective polymer healing via dynamic exchange of strong carbon-carbon bonds

    DOEpatents

    Guan, Zhibin; Lu, Yixuan

    2015-09-15

    A method of preparing a malleable and/or self-healing polymeric or composite material is provided. The method includes providing a polymeric or composite material comprising at least one alkene-containing polymer, combining the polymer with at least one homogeneous or heterogeneous transition metal olefin metathesis catalyst to form a polymeric or composite material, and performing an olefin metathesis reaction on the polymer so as to form reversible carbon-carbon double bonds in the polymer. Also provided is a method of healing a fractured surface of a polymeric material. The method includes bringing a fractured surface of a first polymeric material into contact with a second polymeric material, and performing an olefin metathesis reaction in the presence of a transition metal olefin metathesis catalyst such that the first polymeric material forms reversible carbon-carbon double bonds with the second polymeric material. Compositions comprising malleable and/or self-healing polymeric or composite material are also provided.

  15. Development of a Method for the Preparation of Ruthenium Indenylidene-Ether Olefin Metathesis Catalysts

    PubMed Central

    Jimenez, Leonel R.; Tolentino, Daniel R.; Gallon, Benjamin J.; Schrodi, Yann

    2012-01-01

    The reactions between several derivatives of 1-(3,5-dimethoxyphenyl)-prop-2-yn-1-ol and different ruthenium starting materials [i.e., RuCl2(PPh3)3 and RuCl2(pcymene)(L), where L is tricyclohexylphosphine di-t-butylmethylphosphine, dicyclohexylphenylphosphine, triisobutylphosphine, triisopropylphosphine, or tri-npropylphosphine] are described. Several of these reactions allow for the easy, in-situ and atom-economic preparation of olefin metathesis catalysts. Organic precursor 1-(3,5-dimethoxyphenyl)-1-phenyl-prop-2-yn-1-ol led to the formation of active ruthenium indenylidene-ether complexes, while 1-(3,5-dimethoxyphenyl)-prop-2-yn-1-ol and 1-(3,5-dimethoxyphenyl)-1-methyl-prop-2-yn-1-ol did not. It was also found that a bulky and strong σ-donor phosphine ligand was required to impart good catalytic activity to the new ruthenium complexes. PMID:22580400

  16. Statistical Ring Opening Metathesis Copolymerization of Norbornene and Cyclopentene by Grubbs' 1st-Generation Catalyst.

    PubMed

    Nikovia, Christiana; Maroudas, Andreas-Philippos; Goulis, Panagiotis; Tzimis, Dionysios; Paraskevopoulou, Patrina; Pitsikalis, Marinos

    2015-01-01

    Statistical copolymers of norbornene (NBE) with cyclopentene (CP) were prepared by ring-opening metathesis polymerization, employing the 1st-generation Grubbs' catalyst, in the presence or absence of triphenylphosphine, PPh₃. The reactivity ratios were estimated using the Finemann-Ross, inverted Finemann-Ross, and Kelen-Tüdos graphical methods, along with the computer program COPOINT, which evaluates the parameters of binary copolymerizations from comonomer/copolymer composition data by integrating a given copolymerization equation in its differential form. Structural parameters of the copolymers were obtained by calculating the dyad sequence fractions and the mean sequence length, which were derived using the monomer reactivity ratios. The kinetics of thermal decomposition of the copolymers along with the respective homopolymers was studied by thermogravimetric analysis within the framework of the Ozawa-Flynn-Wall and Kissinger methodologies. Finally, the effect of triphenylphosphine on the kinetics of copolymerization, the reactivity ratios, and the kinetics of thermal decomposition were examined. PMID:26343620

  17. Highly selective Markovnikov hydroboration of alkyl-substituted terminal alkenes with a phosphine-copper(i) catalyst.

    PubMed

    Iwamoto, Hiroaki; Kubota, Koji; Ito, Hajime

    2016-05-21

    A new method has been developed for the Markovnikov hydroboration of alkyl-substituted terminal alkenes. Notably, the use of a bulky bisphosphine-copper(i) catalyst system resulted in high regioselectivity to afford secondary alkylboronates from the corresponding terminal alkenes (branch/linear = 92 : 8-97 : 3). This method also exhibited good functional group compatibility. PMID:26975671

  18. Olefin metathesis for chemical biology.

    PubMed

    Binder, Joseph B; Raines, Ronald T

    2008-12-01

    Chemical biology relies on effective synthetic chemistry for building molecules to probe and modulate biological function. Olefin metathesis in organic solvents is a valuable addition to this armamentarium, and developments during the previous decade are enabling metathesis in aqueous solvents for the manipulation of biomolecules. Functional group-tolerant ruthenium metathesis catalysts modified with charged moieties or hydrophilic polymers are soluble and active in water, enabling ring-opening metathesis polymerization, cross metathesis, and ring-closing metathesis. Alternatively, conventional hydrophobic ruthenium complexes catalyze a similar array of metathesis reactions in mixtures of water and organic solvents. This strategy has enabled cross metathesis on the surface of a protein. Continuing developments in catalyst design and methodology will popularize the bioorthogonal reactivity of metathesis. PMID:18935975

  19. Highly Tunable Selectivity for Syngas-Derived Alkenes over Zinc and Sodium-Modulated Fe5 C2 Catalyst.

    PubMed

    Zhai, Peng; Xu, Cong; Gao, Rui; Liu, Xi; Li, Mengzhu; Li, Weizhen; Fu, Xinpu; Jia, Chunjiang; Xie, Jinglin; Zhao, Ming; Wang, Xiaoping; Li, Yong-Wang; Zhang, Qianwen; Wen, Xiao-Dong; Ma, Ding

    2016-08-16

    Zn- and Na-modulated Fe catalysts were fabricated by a simple coprecipitation/washing method. Zn greatly changed the size of iron species, serving as the structural promoter, while the existence of Na on the surface of the Fe catalyst alters the electronic structure, making the catalyst very active for CO activation. Most importantly, the electronic structure of the catalyst surface suppresses the hydrogenation of double bonds and promotes desorption of products, which renders the catalyst unexpectedly reactive toward alkenes-especially C5+ alkenes (with more than 50% selectivity in hydrocarbons)-while lowering the selectivity for undesired products. This study enriches C1 chemistry and the design of highly selective new catalysts for high-value chemicals. PMID:27445106

  20. Organometallic chemistry: A new metathesis

    NASA Astrophysics Data System (ADS)

    Hennessy, Elisabeth T.; Jacobsen, Eric N.

    2016-08-01

    Carbonyls and alkenes, two of the most common functional groups in organic chemistry, generally do not react with one another. Now, a simple Lewis acid has been shown to catalyse metathesis between alkenes and ketones in a new carbonyl olefination reaction.

  1. Molybdenum Imido Alkylidene Metathesis Catalysts that Contain Electron Withdrawing Biphenolates or Binaphtholates

    PubMed Central

    Singh, Rojendra; Czekelius, Constantin; Schrock, Richard R.; Müller, Peter; Hoveyda, Amir H.

    2008-01-01

    We have prepared new Mo(NR)(CHCMe2Ph)(diolate) complexes (R = 2,6-i-Pr2C6H3, 2,6-Me2C6H3, 1-Adamantyl, or 2-CF3C6H4) that contain relatively electron-withdrawing binaphtholate (3,3′-bis-(9-anthracenyl), 3,3′-bispentafluorophenyl, or 3,3′-bis(3,5-bis(trifluoromethyl)phenyl) or biphenolate (3,3′-di-tert-butyl-5,5′-bistrifluoromethyl-6,6′-dimethyl-1,1′-biphenyl-2,2′-diolate) ligands. We also have prepared new monomeric Mo(NR)(CHCMe2Ph)(2,5-dimethylpyrrolide)2 complexes and have treated them with biphenols or binaphthols in order to prepare several Mo(NR)(CHCMe2Ph)(diolate) species. In one case the new Mo(NR)(CHCMe2Ph)(diolate) complexes could be prepared only through reaction of a binaphthol [3,3′-bis(pentafluorophenyl)binaphthol] with a bis(2,5-dimethylpyrrolide) complex. The pyrrolide approach can be employed either to isolate catalysts on a preparative scale or to generate catalysts in situ. Several simple preliminary ring-closing metathesis reactions show that the new complexes are catalytically competent. PMID:18953421

  2. Molybdenum Imido Alkylidene Metathesis Catalysts that Contain Electron Withdrawing Biphenolates or Binaphtholates.

    PubMed

    Singh, Rojendra; Czekelius, Constantin; Schrock, Richard R; Müller, Peter; Hoveyda, Amir H

    2007-01-01

    We have prepared new Mo(NR)(CHCMe(2)Ph)(diolate) complexes (R = 2,6-i-Pr(2)C(6)H(3), 2,6-Me(2)C(6)H(3), 1-Adamantyl, or 2-CF(3)C(6)H(4)) that contain relatively electron-withdrawing binaphtholate (3,3'-bis-(9-anthracenyl), 3,3'-bispentafluorophenyl, or 3,3'-bis(3,5-bis(trifluoromethyl)phenyl) or biphenolate (3,3'-di-tert-butyl-5,5'-bistrifluoromethyl-6,6'-dimethyl-1,1'-biphenyl-2,2'-diolate) ligands. We also have prepared new monomeric Mo(NR)(CHCMe(2)Ph)(2,5-dimethylpyrrolide)(2) complexes and have treated them with biphenols or binaphthols in order to prepare several Mo(NR)(CHCMe(2)Ph)(diolate) species. In one case the new Mo(NR)(CHCMe(2)Ph)(diolate) complexes could be prepared only through reaction of a binaphthol [3,3'-bis(pentafluorophenyl)binaphthol] with a bis(2,5-dimethylpyrrolide) complex. The pyrrolide approach can be employed either to isolate catalysts on a preparative scale or to generate catalysts in situ. Several simple preliminary ring-closing metathesis reactions show that the new complexes are catalytically competent. PMID:18953421

  3. Acrylate metathesis via the second-generation Grubbs catalyst: unexpected pathways enabled by a PCy3-generated enolate.

    PubMed

    Bailey, Gwendolyn A; Fogg, Deryn E

    2015-06-17

    The diverse applications of acrylate metathesis range from synthesis of high-value α,β-unsaturated esters to depolymerization of unsaturated polymers. Examined here are unexpected side reactions promoted by the important Grubbs catalyst GII. Evidence is presented for attack of PCy3 on the acrylate olefin to generate a reactive carbanion, which participates in multiple pathways, including further Michael addition, proton abstraction, and catalyst deactivation. Related chemistry may be anticipated whenever labile metal-phosphine complexes are used to catalyze reactions of substrates bearing an electron-deficient olefin. PMID:26030596

  4. A Bulky Thiyl-Radical Catalyst for the [3+2] Cyclization of N-Tosyl Vinylaziridines and Alkenes.

    PubMed

    Hashimoto, Takuya; Takino, Kohei; Hato, Kazuki; Maruoka, Keiji

    2016-07-01

    Thiyl-radical-catalyzed cyclization reactions of N-tosyl vinylaziridines and alkenes were developed as a new synthetic method for the generation of substituted pyrrolidines. The key to making this process accessible to a broad range of substrates is the use of a sterically demanding thiyl radical, which prevents the undesired degradation of the catalyst. PMID:27169816

  5. 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...

  6. Epoxidation of alkenes through oxygen activation over a bifunctional CuO/Al2O3 catalyst.

    PubMed

    Scotti, Nicola; Ravasio, Nicoletta; Zaccheria, Federica; Psaro, Rinaldo; Evangelisti, Claudio

    2013-03-01

    The epoxidation of alkenes was carried out over a CuO/Al(2)O(3) catalyst using cumene as an oxygen carrier, through a one-pot reaction, giving high conversion and selectivity with different substrates. Trans-β-methylstyrene gave the corresponding epoxide in 95% yield after 3 h. PMID:23358661

  7. In Silico Olefin Metathesis with Ru-Based Catalysts Containing N-Heterocyclic Carbenes Bearing C60 Fullerenes.

    PubMed

    Martínez, Juan Pablo; Vummaleti, Sai Vikrama Chaitanya; Falivene, Laura; Nolan, Steven P; Cavallo, Luigi; Solà, Miquel; Poater, Albert

    2016-05-01

    Density functional theory calculations have been used to explore the potential of Ru-based complexes with 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (SIMes) ligand backbone (A) being modified in silico by the insertion of a C60 molecule (B and C), as olefin metathesis catalysts. To this end, we investigated the olefin metathesis reaction catalyzed by complexes A, B, and C using ethylene as the substrate, focusing mainly on the thermodynamic stability of all possible reaction intermediates. Our results suggest that complex B bearing an electron-withdrawing N-heterocyclic carbene improves the performance of unannulated complex A. The efficiency of complex B is only surpassed by complex A when the backbone of the N-heterocyclic carbene of complex A is substituted by two amino groups. The particular performance of complexes B and C has to be attributed to electronic factors, that is, the electronic-donating capacity of modified SIMes ligand rather than steric effects, because the latter are predicted to be almost identical for complexes B and C when compared to those of A. Overall, this study indicates that such Ru-based complexes B and C might have the potential to be effective olefin metathesis catalysts. PMID:27059290

  8. Synthesis and polymerization of renewable 1,3-cyclohexadiene using metathesis, isomerization, and cascade reactions with late-metal catalysts.

    PubMed

    Mathers, Robert T; Shreve, Michael J; Meyler, Etan; Damodaran, Krishnan; Iwig, David F; Kelley, Diana J

    2011-09-01

    Synthesis and subsequent polymerization of renewable 1,3-cyclohexadiene (1,3-CHD) from plant oils is reported via metathesis and isomerization reactions. The metathesis reaction required no plant oil purification, minimal catalyst loading, no organic solvents, and simple product recovery by distillation. After treating soybean oil with a ruthenium metathesis catalyst, the resulting 1,4-cyclohexadiene (1,4-CHD) was isomerized with RuHCl(CO)(PPh3)3. The isomerization reaction was conducted for 1 h in neat 1,4-CHD with [1,4-CHD]/[RuHCl(CO)(PPh3)3] ratios as high as 5000. The isomerization and subsequent polymerization of the renewable 1,3-CHD was examined as a two-step sequence and as a one-step cascade reaction. The polymerization was catalyzed with nickel(II)acetylacetonate/methaluminoxane in neat monomer, hydrogenated d-limonene, and toluene. The resulting polymers were characterized by FTIR, DSC, and TGA. PMID:21648003

  9. Grubbs–Hoveyda type catalysts bearing a dicationic N-heterocyclic carbene for biphasic olefin metathesis reactions in ionic liquids

    PubMed Central

    Koy, Maximilian; Altmann, Hagen J; Autenrieth, Benjamin; Frey, Wolfgang

    2015-01-01

    Summary The novel dicationic metathesis catalyst [(RuCl2(H2ITapMe2)(=CH–2-(2-PrO)-C6H4))2+ (OTf−)2] (Ru-2, H2ITapMe2 = 1,3-bis(2’,6’-dimethyl-4’-trimethylammoniumphenyl)-4,5-dihydroimidazol-2-ylidene, OTf− = CF3SO3 −) based on a dicationic N-heterocyclic carbene (NHC) ligand was prepared. The reactivity was tested in ring opening metathesis polymerization (ROMP) under biphasic conditions using a nonpolar organic solvent (toluene) and the ionic liquid (IL) 1-butyl-2,3-dimethylimidazolium tetrafluoroborate [BDMIM+][BF4 −]. The structure of Ru-2 was confirmed by single crystal X-ray analysis. PMID:26664582

  10. Methods for suppressing isomerization of olefin metathesis products

    SciTech Connect

    Firth, Bruce E.; Kirk, Sharon E.

    2015-10-27

    A method for suppressing isomerization of an olefin metathesis product produced in a metathesis reaction includes adding an isomerization suppression agent that includes nitric acid to a mixture that includes the olefin metathesis product and residual metathesis catalyst from the metathesis reaction under conditions that are sufficient to passivate at least a portion of the residual metathesis catalyst. Methods of refining a natural oil are described.

  11. Methods for suppressing isomerization of olefin metathesis products

    SciTech Connect

    Firth, Bruce E.; Kirk, Sharon E.; Gavaskar, Vasudeo S.

    2015-09-22

    A method for suppressing isomerization of an olefin metathesis product produced in a metathesis reaction includes adding an isomerization suppression agent to a mixture that includes the olefin metathesis product and residual metathesis catalyst from the metathesis reaction under conditions that are sufficient to passivate at least a portion of the residual metathesis catalyst. The isomerization suppression agent is phosphorous acid, a phosphorous acid ester, phosphinic acid, a phosphinic acid ester or combinations thereof. Methods of refining natural oils are described.

  12. Towards New Generations of Metathesis Metal-Carbene Pre-catalysts

    NASA Astrophysics Data System (ADS)

    Allaert, Bart; Dieltiens, Nicolai; Stevens, Chris; Drozdzak, Renata; Dragutan, Ileana; Dragutan, Valerian; Verpoort, Francis

    : A short general introduction combined with some historical milestones in the field of olefin metathesis is presented followed by an overview of recent representatives of metal carbene initiators. This paper attempts to relief the many superb contributions and overwhelming work invested in intelligent design and innovative synthesis in this area. Despites of recent advances there is still a great interest in the generation of new, better performing, and more environment friendly metathesis.

  13. 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.

  14. α-Allyl-α-aryl α-Amino Esters in the Asymmetric Synthesis of Acyclic and Cyclic Amino Acid Derivatives by Alkene Metathesis

    PubMed Central

    2015-01-01

    Allylating agents were explored for the asymmetric synthesis of α-allyl-α-aryl α-amino acids by tandem N-alkylation/π-allylation. Cross-metathesis of the tandem product was developed to provide allylic diversity not afforded in the parent reaction; the synthesis of homotyrosine and homoglutamate analogues was completed. Cyclic α-amino acid derivatives could be accessed by ring-closing metathesis presenting a viable strategy to higher ring homologue of enantioenriched α-substituted proline. The eight-membered proline analogue was successfully converted to the pyrrolizidine natural product backbone. PMID:24828423

  15. Synergy between Two Metal Catalysts: A Highly Active Silica-Supported Bimetallic W/Zr Catalyst for Metathesis of n-Decane.

    PubMed

    Samantaray, Manoja K; Dey, Raju; Kavitake, Santosh; Abou-Hamad, Edy; Bendjeriou-Sedjerari, Anissa; Hamieh, Ali; Basset, Jean-Marie

    2016-07-13

    A well-defined, silica-supported bimetallic precatalyst [≡Si-O-W(Me)5≡Si-O-Zr(Np)3] (4) has been synthesized for the first time by successively grafting two organometallic complexes [W(Me)6 (1) followed by ZrNp4 (2)] on a single silica support. Surprisingly, multiple-quantum NMR characterization demonstrates that W and Zr species are in close proximity to each other. Hydrogenation of this bimetallic catalyst at room temperature showed the easy formation of zirconium hydride, probably facilitated by tungsten hydride which was formed at this temperature. This bimetallic W/Zr hydride precatalyst proved to be more efficient (TON = 1436) than the monometallic W hydride (TON = 650) in the metathesis of n-decane at 150 °C. This synergy between Zr and W suggests that the slow step of alkane metathesis is the C-H bond activation that occurs on Zr. The produced olefin resulting from a β-H elimination undergoes easy metathesis on W. PMID:27248839

  16. Probing Stereoselectivity in Ring-Opening Metathesis Polymerization Mediated by Cyclometalated Ruthenium-Based Catalysts: A Combined Experimental and Computational Study.

    PubMed

    Rosebrugh, L E; Ahmed, T S; Marx, V M; Hartung, J; Liu, P; López, J G; Houk, K N; Grubbs, R H

    2016-02-01

    The microstructures of polymers produced by ring-opening metathesis polymerization (ROMP) with cyclometalated Ru-carbene metathesis catalysts were investigated. A strong bias for a cis,syndiotactic microstructure with minimal head-to-tail bias was observed. In instances where trans errors were introduced, it was determined that these regions were also syndiotactic. Furthermore, hypothetical reaction intermediates and transition structures were analyzed computationally. Combined experimental and computational data support a reaction mechanism in which cis,syndio-selectivity is a result of stereogenic metal control, while microstructural errors are predominantly due to alkylidene isomerization via rotation about the Ru═C double bond. PMID:26726835

  17. Pulsed-addition ring-opening metathesis polymerization: catalyst-economical syntheses of homopolymers and block copolymers.

    PubMed

    Matson, John B; Virgil, Scott C; Grubbs, Robert H

    2009-03-11

    Poly(tert-butyl ester norbornene imide) homopolymers and poly(tert-butyl ester norbornene imide-b-N-methyloxanorbornene imide) copolymers were prepared by pulsed-addition ring-opening metathesis polymerization (PA-ROMP). PA-ROMP is a unique polymerization method that employs a symmetrical cis-olefin chain transfer agent (CTA) to simultaneously cap a living polymer chain and regenerate the ROMP initiator with high fidelity. Unlike traditional ROMP with chain transfer, the CTA reacts only with the living chain end, resulting in narrowly dispersed products. The regenerated initiator can then initiate polymerization of a subsequent batch of monomer, allowing for multiple polymer chains with controlled molecular weight and low polydispersity to be generated from one metal initiator. Using the fast-initiating ruthenium metathesis catalyst (H(2)IMes)(Cl)(2)(pyr)(2)RuCHPh and cis-4-octene as a CTA, the capabilities of PA-ROMP were investigated with a Symyx robotic system, which allowed for increased control and precision of injection volumes. The results from a detailed study of the time required to carry out the end-capping/initiator-regeneration step were used to design several experiments in which PA-ROMP was performed from one to ten cycles. After determination of the rate of catalyst death, a single, low polydispersity polymer was prepared by adjusting the amount of monomer injected in each cycle, maintaining a constant monomer/catalyst ratio. Additionally, PA-ROMP was used to prepare nearly perfect block copolymers by quickly injecting a second monomer at a specific time interval after the first monomer injection, such that chain transfer had not yet occurred. Polymers were characterized by gel permeation chromatography with multiangle laser light scattering. PMID:19215131

  18. Synthesis, characterization and insights into stable and well organized hexagonal mesoporous zinc-doped alumina as promising metathesis catalysts carrier.

    PubMed

    Abidli, Abdelnasser; Hamoudi, Safia; Belkacemi, Khaled

    2015-06-01

    A series of highly ordered hexagonal mesoporous alumina and zinc-modified mesoporous alumina samples are synthesized via a sol-gel method through an evaporation-induced self-assembly process using Pluronic F127 as nonionic templating agent and several aluminum precursors. The process was mediated using several carboxylic acids along with hydrochloric acid in ethanol. Successful impregnation of ZnCl2 was achieved while maintaining the ordered structure. The surface and textural properties of the materials were investigated. N2-physisorption analysis revealed a BET surface area of 394 m(2) g(-1) and a pore volume around 0.55 cm(3) g(-1). Moreover, small-angle XRD diffraction patterns highlighted the well-organized hexagonal structure even upon the incorporation of zinc chloride. The organized-structure arrangement was further confirmed by transmission electron microscopy (TEM) analysis. The Zn/Al composition of the final materials was confirmed by EDX and XPS analysis, and the zinc amount incorporated was analyzed by ICP. Furthermore, the surface modification with zinc chloride impregnation was analyzed by XPS, (1)H and (27)Al MAS-NMR and FTIR spectroscopic techniques. In addition, the effects of synthesis conditions and the mechanism of the mesostructure formation were explored. The catalytic activity of several methyltrioxorhenium (MTO)-based catalysts supported on these hexagonal mesoporous alumina materials was tested for methyl oleate self-metathesis. The results showed improved kinetics using hexagonal alumina in comparison to those using wormhole-like alumina counterparts. This behavior could be attributed to better mass transfer features of hexagonal mesoporous alumina. The prepared materials with desirable pore size and structure are suitable candidates as catalyst supports for metathesis of bulky functionalized olefins and other catalytic transformations due to their enhanced Lewis acidity and more uniform pore networks favoring enhanced and selective mass

  19. An inexpensive and recyclable silver-foil catalyst for the cyclopropanation of alkenes with diazoacetates under mechanochemical conditions.

    PubMed

    Chen, Longrui; Bovee, Mark O; Lemma, Betsegaw E; Keithley, Kimberlee S M; Pilson, Sara L; Coleman, Michael G; Mack, James

    2015-09-14

    The diastereoselective cyclopropanation of various alkenes with diazoacetate derivatives can be achieved under mechanochemical conditions using metallic silver foil and a stainless-steel vial and ball system. This solvent-free method displays analogous reactivity and selectivity to solution-phase reactions without the need for slow diazoacetate addition or an inert atmosphere. The heterogeneous silver-foil catalyst system is easily recyclable without any appreciable loss of activity or selectivity being observed. The cyclopropanation products were obtained with excellent diastereoselectivities (up to 98:2 d.r.) and in high yields (up to 96 %). PMID:26352021

  20. Olefin metathesis in air

    PubMed Central

    Piola, Lorenzo; Nahra, Fady

    2015-01-01

    Summary Since the discovery and now widespread use of olefin metathesis, the evolution of metathesis catalysts towards air stability has become an area of significant interest. In this fascinating area of study, beginning with early systems making use of high oxidation state early transition metal centers that required strict exclusion of water and air, advances have been made to render catalysts more stable and yet more functional group tolerant. This review summarizes the major developments concerning catalytic systems directed towards water and air tolerance. PMID:26664625

  1. Preparation and characterization of active niobium, tantalum, and tungsten metathesis catalysts

    SciTech Connect

    Schrock, R.; Rocklage, S.; Wengrovius, J.; Rupprecht, G.; Fellmann, J.

    1980-03-01

    Complexes of the types M(CHCR/sub 3/)L/sub 2/X/sub 3/, M(CHCR/sub 3/)(OCR/sub 3/)/sub 2/LX, and WO(CHCR/sub 3/)L/sub 2/Cl/sub 2/, where M is Nb or Ta, R is methyl, L is a tertiary phosphine, and X is Cl or Br, showed good activities in metathesis of terminal olefins, including ethylene, propylene, styrene, 1-butene, and cis-2-pentene, at 25/sup 0/C in the presence of traces of AlCl/sub 3/.

  2. Ruthenium-catalyzed intramolecular metathesis of dienes and its application in the synthesis of bridged and spiro azabicycles

    NASA Astrophysics Data System (ADS)

    Kuznetsov, N. Yu; Bubnov, Yu N.

    2015-07-01

    The review presents a historical excursion into catalytic alkene metathesis, covering the problems of history of the discovery of this process, as well as investigations on the properties, structure and reactivity of the most popular ruthenium catalysts for metathesis, mechanism of their action and decomposition. The main part covers studies devoted to the syntheses of bridged azabicyclic and 1-azaspirocyclic compounds comprising the intramolecular metathesis of dienes as the key step. The formation of a bicyclic skeleton of a series of natural bridged (cocaine, ferruginine, calystegines, and anatoxin-a) and spiro (pinnaic acids, halichlorine, hystrionicotoxin, and cephalotaxine) azabicycles, as well as their analogues and compounds with larger rings is demonstrated. The methods for the synthesis of diene precursors and the conditions for final assembling of the bicyclic compounds are considered in detail. The generalization of the literature data allows one to efficiently carry out the mentioned process taking into account the most important features. The bibliography includes 129 references.

  3. Consequences of the electronic tuning of latent ruthenium-based olefin metathesis catalysts on their reactivity

    PubMed Central

    Pump, Eva; Pazio, Aleksandra E; Woźniak, Krzysztof; Cavallo, Luigi

    2015-01-01

    Summary Two ruthenium olefin metathesis initiators featuring electronically modified quinoline-based chelating carbene ligands are introduced. Their reactivity in RCM and ROMP reactions was tested and the results were compared to those obtained with the parent unsubstituted compound. The studied complexes are very stable at high temperatures up to 140 °C. The placement of an electron-withdrawing functionality translates into an enhanced activity in RCM. While electronically modified precatalysts, which exist predominantly in the trans-dichloro configuration, gave mostly the RCM and a minor amount of the cycloisomerization product, the unmodified congener, which preferentially exists as its cis-dichloro isomer, shows a switched reactivity. The position of the equilibrium between the cis- and the trans-dichloro species was found to be the crucial factor governing the reactivity of the complexes. PMID:26425202

  4. Consequences of the electronic tuning of latent ruthenium-based olefin metathesis catalysts on their reactivity.

    PubMed

    Żukowska, Karolina; Pump, Eva; Pazio, Aleksandra E; Woźniak, Krzysztof; Cavallo, Luigi; Slugovc, Christian

    2015-01-01

    Two ruthenium olefin metathesis initiators featuring electronically modified quinoline-based chelating carbene ligands are introduced. Their reactivity in RCM and ROMP reactions was tested and the results were compared to those obtained with the parent unsubstituted compound. The studied complexes are very stable at high temperatures up to 140 °C. The placement of an electron-withdrawing functionality translates into an enhanced activity in RCM. While electronically modified precatalysts, which exist predominantly in the trans-dichloro configuration, gave mostly the RCM and a minor amount of the cycloisomerization product, the unmodified congener, which preferentially exists as its cis-dichloro isomer, shows a switched reactivity. The position of the equilibrium between the cis- and the trans-dichloro species was found to be the crucial factor governing the reactivity of the complexes. PMID:26425202

  5. Solvent-free cyclization of linear dienes using olefin metathesis and the Thorpe-Ingold effect

    SciTech Connect

    Forbees, M.D.E.; Myers, T.L.; Maynard, H.D.; Schulz, G.R. ); Patton, J.T.; Smith, D.W. Jr.; Wagener, K.B. )

    1992-12-30

    The olefin metathesis reaction is of great synthetic utility in polymer chemistry. The recent development of ring-opening (ROMP) and acyclic diene (ADMET) metathesis polymerization reactions has opened new avenues for the synthesis of novel polymeric materials. Recently the authors used ADMET to synthesize several photochemically active poly(keto olefins) using the catalyst Mo(CHCMe[sub 2]Ph)(NAr)(OCMe(CF[sub 3])[sub 2])[sub 2] (Ar = 2,6-diisopropylphenyl) (1) developed by Schrock and co-workers in 1990. In the course of that work, they discovered that neat samples of highly substituted dienes will cyclize quantitatively via metathesis to give difunctional five- and seven-membered rings instead of the expected linear polymer. Examples of substituted diene cyclizations by metathesis even in the presence of a solvent are rare. Their systematic exploitation in organic synthesis has therefore been limited to two recent studies by Fu and Grubbs, who cyclized several substituted diene ethers, amines, and amides to unsaturated oxygen and nitrogen heterocycles. Cyclization of unsubstituted dienes in various solvents has been reported, but complete conversion occurred in only a few cases. Formation of cyclic alkene oligomers from back-biting during the ROMP reaction is also known. The reactions reported here are unusual in that they are intermolecular between catalyst and substrate, yet can give 100% yield of product solely from the monomer in the absence of solvent. 13 refs.

  6. New metathesis catalyst bearing chromanyl moieties at the N-heterocyclic carbene ligand

    PubMed Central

    Suchodolski, Szymon; Wojtkielewicz, Agnieszka; Morzycki, Jacek W

    2015-01-01

    Summary The synthesis of a new type of Hoveyda–Grubbs 2nd generation catalyst bearing a modified N-heterocyclic carbene ligands is reported. The new catalyst contains an NHC ligand symmetrically substituted with chromanyl moieties. The complex was tested in model CM and RCM reactions. It showed very high activity in CM reactions with electron-deficient α,β-unsaturated compounds even at 0 °C. It was also examined in more demanding systems such as conjugated dienes and polyenes. The catalyst is stable, storable and easy to purify. PMID:26877801

  7. From Resting State to the Steady State: Mechanistic Studies of Ene-Yne Metathesis Promoted by the Hoveyda Complex.

    PubMed

    Griffiths, Justin R; Keister, Jerome B; Diver, Steven T

    2016-04-27

    The kinetics of intermolecular ene-yne metathesis (EYM) with the Hoveyda precatalyst (Ru1) has been studied. For 1-hexene metathesis with 2-benzoyloxy-3-butyne, the experimental rate law was determined to be first-order in 1-hexene (0.3-4 M), first-order in initial catalyst concentration, and zero-order for the terminal alkyne. At low catalyst concentrations (0.1 mM), the rate of precatalyst initiation was observed by UV-vis and the alkyne disappearance was observed by in situ FT-IR. Comparison of the rate of precatalyst initiation and the rate of EYM shows that a low, steady-state concentration of active catalyst is rapidly produced. Application of steady-state conditions to the carbene intermediates provided a rate treatment that fit the experimental rate law. Starting from a ruthenium alkylidene complex, competition between 2-isopropoxystyrene and 1-hexene gave a mixture of 2-isopropoxyarylidene and pentylidene species, which were trappable by the Buchner reaction. By varying the relative concentration of these alkenes, 2-isopropoxystyrene was found to be 80 times more effective than 1-hexene in production of their respective Ru complexes. Buchner-trapping of the initiation of Ru1 with excess 1-hexene after 50% loss of Ru1 gave 99% of the Buchner-trapping product derived from precatalyst Ru1. For the initiation process, this shows that there is an alkene-dependent loss of precatalyst Ru1, but this does not directly produce the active catalyst. A faster initiating precatalyst for alkene metathesis gave similar rates of EYM. Buchner-trapping of ene-yne metathesis failed to deliver any products derived from Buchner insertion, consistent with rapid decomposition of carbene intermediates under ene-yne conditions. An internal alkyne, 1,4-diacetoxy-2-butyne, was found to obey a different rate law. Finally, the second-order rate constant for ene-yne metathesis was compared to that previously determined by the Grubbs second-generation carbene complex: Ru1 was found to

  8. Extrudate versus powder silica alumina as support for Re₂O₇ catalyst in the metathesis of seed oil-derivatives - a comparison.

    PubMed

    Marvey, Bassie B

    2009-01-01

    Self- and cross-metathesis of fatty acid methyl esters (FAMEs) was investigated using a silica alumina supported Re(2)O(7) catalyst. Although a 3 wt% Re(2)O(7)/SiO(2)-Al(2)O(3)/SnBu(4) is already active for the metathesis of unsaturated FAMEs, the results have shown that particle size of silica alumina support has a profound influence on its activity and selectivity. Consequently, high substrate conversions coupled with improved product yields (for mono- and diesters) and reaction rates were obtained upon using powder, as opposed to extrudate silica alumina as the support material. Diesters are platform compounds for the synthesis of polymers and fragrances. In this paper a comparative outline of the influence of particle size of silica alumina (extrudate versus powder) on catalytic performance of a 3 wt% Re(2)O(7)/SiO(2)-Al(2)O(3)/SnBu(4) for self- and cross-metathesis of FAMEs is made. Low surface area and diffusion constraints associated with extrudates were identified as some of the factors leading to low catalytic activity and selectivity. PMID:19333442

  9. Ring-opening metathesis polymerization of 18-e Cobalt(I)-containing norbornene and application as heterogeneous macromolecular catalyst in atom transfer radical polymerization.

    PubMed

    Yan, Yi; Zhang, Jiuyang; Wilbon, Perry; Qiao, Yali; Tang, Chuanbing

    2014-11-01

    In the last decades, metallopolymers have received great attention due to their various applications in the fields of materials and chemistry. In this article, a neutral 18-electron exo-substituted η(4) -cyclopentadiene CpCo(I) unit-containing polymer is prepared in a controlled/"living" fashion by combining facile click chemistry and ring-opening meta-thesis polymerization (ROMP). This Co(I)-containing polymer is further used as a heterogeneous macromolecular catalyst for atom transfer radical polymerization (ATRP) of methyl methacrylate and styrene. PMID:25250694

  10. A metathesis model for the dehydrogenative coupling of amines with alcohols and esters into carboxamides by Milstein's [Ru(PNN)(CO)(H)] catalysts.

    PubMed

    Hasanayn, Faraj; Harb, Hassan

    2014-08-18

    Milstein's [Ru(PNN)(CO)(H)] catalyst (1-Ru) is known to mediate the dehydrogenative coupling of alcohols into esters. When it is used in alcohol-amine mixtures it catalyzes carboxamide formation selectively over esters and imines. The given chemistry is generally accepted to follow metal-ligand cooperation (MLC) mechanisms involving hemiacetals and hemiaminals as intermediates. Using electronic structure DFT methods we investigate alternative, more direct OR/H and NHR/H metal/acyl metathesis routes to coupling that circumvent the intermediacy of the hemiacetal and the hemiaminal. The newly proposed mechanism involves formation of hemiacetaloxide and hemiaminaloxide ion-pairs by addition of an aldehyde (from metal-catalyzed alcohol dehydrogenation) to an octahedral ruthenium-alkoxide or ruthenium-amide intermediate (from alcohol or amine addition to 1-Ru), followed by simple rearrangement (slippage) within the intact ion-pairs to transfer a hydride from the hemiacetaloxide or hemiaminaloxide to the metal. We show that the computed potential energy surfaces that are sometimes invoked to support the MLC mechanism correspond to indirect routes to metathesis. Both the ion-pair and the MLC routes predict the dehydrogenative coupling of ethanol and methanol into methyl acetate to be kinetically much more favored than the kinetics of formation of N-methylacetamide from ethanol and methylamine. However, the calculations provide evidence for the accessibility of a low energy NHR/OR metathesis path that would amidate the ester into the experimentally observed thermodynamically more favored carboxamide product. In fact, 1-Ru is known to be a catalyst for ester amidation. PMID:25079590

  11. Alkene Isomerization Using a Solid Acid as Activator and Support for a Homogeneous Catalyst

    ERIC Educational Resources Information Center

    Seen, Andrew J.

    2004-01-01

    An upper-level undergraduate experiment that, in addition to introducing students to catalysis using an air sensitive transition-metal complex, introduces the use of a solid acid as an activator and support for the catalyst is developed. The increased stability acquired in the course of the process affords the opportunity to characterize the…

  12. Methods of making organic compounds by metathesis

    DOEpatents

    Abraham, Timothy W.; Kaido, Hiroki; Lee, Choon Woo; Pederson, Richard L.; Schrodi, Yann; Tupy, Michael John

    2015-09-01

    Described are methods of making organic compounds by metathesis chemistry. The methods of the invention are particularly useful for making industrially-important organic compounds beginning with starting compositions derived from renewable feedstocks, such as natural oils. The methods make use of a cross-metathesis step with an olefin compound to produce functionalized alkene intermediates having a pre-determined double bond position. Once isolated, the functionalized alkene intermediate can be self-metathesized or cross-metathesized (e.g., with a second functionalized alkene) to produce the desired organic compound or a precursor thereto. The method may be used to make bifunctional organic compounds, such as diacids, diesters, dicarboxylate salts, acid/esters, acid/amines, acid/alcohols, acid/aldehydes, acid/ketones, acid/halides, acid/nitriles, ester/amines, ester/alcohols, ester/aldehydes, ester/ketones, ester/halides, ester/nitriles, and the like.

  13. Switching on the Metathesis Activity of Re Oxo Alkylidene Surface Sites through a Tailor-Made Silica-Alumina Support.

    PubMed

    Valla, Maxence; Stadler, David; Mougel, Victor; Copéret, Christophe

    2016-01-18

    Re oxo alkylidene surface species are putative active sites in classical heterogeneous Re-based alkene-metathesis catalysts. However, the lack of evidence for such species questions their existence and/or relevance as reaction intermediates. Using Re(O)(=CH-CH=CPh2)(OtBuF6)3(THF), the corresponding well-defined Re oxo alkylidene surface species can be generated on both silica and silica-alumina supports. While inactive on the silica support, it displays very good activity, even for functionalized olefins, on the silica-alumina support. PMID:26756446

  14. A Two-Component Alkyne Metathesis Catalyst System with an Improved Substrate Scope and Functional Group Tolerance: Development and Applications to Natural Product Synthesis.

    PubMed

    Schaubach, Sebastian; Gebauer, Konrad; Ungeheuer, Felix; Hoffmeister, Laura; Ilg, Marina K; Wirtz, Conny; Fürstner, Alois

    2016-06-13

    Although molybdenum alkylidyne complexes such as 1 endowed with triarylsilanolate ligands are excellent catalysts for alkyne metathesis, they can encounter limitations when (multiple) protic sites are present in a given substrate and/or when forcing conditions are necessary. In such cases, a catalyst formed in situ upon mixing of the trisamidomolybenum alkylidyne complex 3 and the readily available trisilanol derivatives 8 or 11 shows significantly better performance. This two-component system worked well for a series of model compounds comprising primary, secondary or phenolic -OH groups, as well as for a set of challenging (bis)propargylic substrates. Its remarkable efficiency is also evident from applications to the total syntheses of manshurolide, a highly strained sesquiterpene lactone with kinase inhibitory activity, and the structurally demanding immunosuppressive cyclodiyne ivorenolide A; in either case, the standard catalyst 1 largely failed to effect the critical macrocyclization, whereas the two-component system was fully operative. A study directed toward the quinolizidine alkaloid lythrancepine I features yet another instructive example, in that a triyne substrate was metathesized with the help of 3/11 such that two of the triple bonds participated in ring closure, while the third one passed uncompromised. As a spin-off of this project, a much improved ruthenium catalyst for the redox isomerization of propargyl alcohols to the corresponding enones was developed. PMID:27203803

  15. 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…

  16. On the nature and formation of the active sites in Re[sub 2]O[sub 7] metathesis catalysts supported on borated alumina

    SciTech Connect

    Sibeijn, M.; Bliek, A. ); Veen, J.A.R. van ); Moulijn, J.A. )

    1994-02-01

    Re[sub 2]O[sub 7] catalysts on borated aluminas have been investigated with a view to correlating the structure of the active site and its activity in the metathesis of methyl oleate. Modification of alumina with boria results in much more active metathesis catalysts. Infrared spectroscopy was used for the characterization, pyridine adsorption measurements for determining the Lewis acid and Bronsted acid sites, and temperature-programmed IR measurements to follow the reactions occurring during calcination of the supports and catalysts. Boria binds to the surface via the alumina hydroxyls. Upon Re[sub 2]O[sub 7] loading of nonborated alumina, the ReO[sub 4] groups react first with Lewis acid sites, onto which they are strongly bonded. Above a Re[sub 2]O[sub 7] loading of 3 wt% surface hydroxyls are also substituted by Re[sub 2]O[sub 7] groups, resulting in an increase in catalytic activity. When the borated supports are loaded with Re[sub 2]O[sub 7], the ReO[sub 4] groups are also first bonded to the Lewis acid sites. During calcination these ReO[sub 4] groups substitute surface hydroxyls preferably on alumina hydroxyls. The substitution of the boron hydroxyls only takes place at a calcination time of at least 2 h at 823 K. At high borate loadings (>10 wt%) the reaction of ReO[sub 4] groups with boron hydroxyls competes with the condensation reaction of two neighbouring boron hydroxyls. Taking into account that a ReO[sub 4] group which has substituted in acidic OH group on the support is the precursor of an active site, the increase in activity of Re[sub 2]O[sub 7] catalysts by modification of the alumina support with boria can be ascribed to two effects, namely, the reduction of the bonding strength of Lewis acid sites with ReO[sub 4], making the ReO[sub 4]-OH substitution reaction possible during calcination even at low rhenium loadings, and the formation of acidic surface hydroxyls. 16 refs., 11 figs., 3 tabs.

  17. Metathesis depolymerizable surfactants

    DOEpatents

    Jamison, Gregory M.; Wheeler, David R.; Loy, Douglas A.; Simmons, Blake A.; Long, Timothy M.; McElhanon, James R.; Rahimian, Kamyar; Staiger, Chad L.

    2008-04-15

    A class of surfactant molecules whose structure includes regularly spaced unsaturation in the tail group and thus, can be readily decomposed by ring-closing metathesis, and particularly by the action of a transition metal catalyst, to form small molecule products. These small molecules are designed to have increased volatility and/or enhanced solubility as compared to the original surfactant molecule and are thus easily removed by solvent extraction or vacuum extraction at low temperature. By producing easily removable decomposition products, the surfactant molecules become particularly desirable as template structures for preparing meso- and microstructural materials with tailored properties.

  18. Cationic bis-N-heterocyclic carbene (NHC) ruthenium complex: structure and application as latent catalyst in olefin metathesis.

    PubMed

    Rouen, Mathieu; Queval, Pierre; Falivene, Laura; Allard, Jessica; Toupet, Loïc; Crévisy, Christophe; Caijo, Frédéric; Baslé, Olivier; Cavallo, Luigi; Mauduit, Marc

    2014-10-13

    An unexpected cationic bis-N-heterocyclic carbene (NHC) benzylidene ether based ruthenium complex (2 a) was prepared through the double incorporation of an unsymmetrical unsaturated N-heterocyclic carbene (U2 -NHC) ligand that bore an N-substituted cyclododecyl side chain. The isolation and full characterization (including X-ray diffraction studies) of key synthetic intermediates along with theoretical calculations allowed us to understand the mechanism of the overall cationization process. Finally, the newly developed complex 2 a displayed interesting latent behavior during ring-closing metathesis, which could be "switched on" under acidic conditions. PMID:25212827

  19. Enantioselective Olefin Metathesis with Cyclometalated Ruthenium Complexes

    PubMed Central

    2015-01-01

    The success of enantioselective olefin metathesis relies on the design of enantioenriched alkylidene complexes capable of transferring stereochemical information from the catalyst structure to the reactants. Cyclometalation of the NHC ligand has proven to be a successful strategy to incorporate stereogenic atoms into the catalyst structure. Enantioenriched complexes incorporating this design element catalyze highly Z- and enantioselective asymmetric ring opening/cross metathesis (AROCM) of norbornenes and cyclobutenes, and the difference in ring strain between these two substrates leads to different propagating species in the catalytic cycle. Asymmetric ring closing metathesis (ARCM) of a challenging class of prochiral trienes has also been achieved. The extent of reversibility and effect of reaction setup was also explored. Finally, promising levels of enantioselectivity in an unprecedented Z-selective asymmetric cross metathesis (ACM) of a prochiral 1,4-diene was demonstrated. PMID:25137310

  20. Chemical imaging of catalyst deactivation during the conversion of renewables at the single particle level: etherification of biomass-based polyols with alkenes over H-Beta zeolites.

    PubMed

    Parvulescu, Andrei N; Mores, Davide; Stavitski, Eli; Teodorescu, Cristian M; Bruijnincx, Pieter C A; Gebbink, Robertus J M Klein; Weckhuysen, Bert M

    2010-08-01

    The etherification of biomass-based alcohols with various linear alpha-olefins under solvent-free conditions was followed in a space- and time-resolved manner on 9 microm large H-Beta zeolite crystals by confocal fluorescence microscopy. This allowed us to visualize the interaction with the substrate and distribution of the coke products into the catalyst at the level of an individual zeolite crystal during the etherification process. The spectroscopic information obtained on the micrometer-scale zeolite was in line with the results obtained with bulk characterization techniques and further confirmed by the catalytic results obtained both for micrometer-scale and nanoscale zeolites. This allowed us to explain the influence of the substrate type (glycerol, glycols, and alkenes) and zeolite properties (Si/Al ratio and particle size) on the etherification activity. The etherification of the biomass-based alcohols takes place mainly on the external surface of the zeolite particles. The gradual blockage of the external surface of the zeolite results in a partial or total loss of etherification activity. The deactivation could be attributed to olefin oligomerization. The high conversions obtained in the etherification of 1,2-propylene glycol with long linear alkenes (up to 80%) and the pronounced deactivation of the zeolite observed in the etherification of glycerol with long linear alkenes (max. 20% conversion) were explained by the spectroscopic measurements and is due to differences in the adsorption, i.e., in the center of the zeolite particle for glycerol and on the external surface in the case of glycols. PMID:20662520

  1. Hexacoordinate Ru-based olefin metathesis catalysts with pH-responsive N-heterocyclic carbene (NHC) and N-donor ligands for ROMP reactions in non-aqueous, aqueous and emulsion conditions.

    PubMed

    Balof, Shawna L; Nix, K Owen; Olliff, Matthew S; Roessler, Sarah E; Saha, Arpita; Müller, Kevin B; Behrens, Ulrich; Valente, Edward J; Schanz, Hans-Jörg

    2015-01-01

    Three new ruthenium alkylidene complexes (PCy3)Cl2(H2ITap)Ru=CHSPh (9), (DMAP)2Cl2(H2ITap)Ru=CHPh (11) and (DMAP)2Cl2(H2ITap)Ru=CHSPh (12) have been synthesized bearing the pH-responsive H2ITap ligand (H2ITap = 1,3-bis(2',6'-dimethyl-4'-dimethylaminophenyl)-4,5-dihydroimidazol-2-ylidene). Catalysts 11 and 12 are additionally ligated by two pH-responsive DMAP ligands. The crystal structure was solved for complex 12 by X-ray diffraction. In organic, neutral solution, the catalysts are capable of performing standard ring-opening metathesis polymerization (ROMP) and ring closing metathesis (RCM) reactions with standard substrates. The ROMP with complex 11 is accelerated in the presence of two equiv of H3PO4, but is reduced as soon as the acid amount increased. The metathesis of phenylthiomethylidene catalysts 9 and 12 is sluggish at room temperature, but their ROMP can be dramatically accelerated at 60 °C. Complexes 11 and 12 are soluble in aqueous acid. They display the ability to perform RCM of diallylmalonic acid (DAMA), however, their conversions are very low amounting only to few turnovers before decomposition. However, both catalysts exhibit outstanding performance in the ROMP of dicyclopentadiene (DCPD) and mixtures of DCPD with cyclooctene (COE) in acidic aqueous microemulsion. With loadings as low as 180 ppm, the catalysts afforded mostly quantitative conversions of these monomers while maintaining the size and shape of the droplets throughout the polymerization process. Furthermore, the coagulate content for all experiments stayed <2%. This represents an unprecedented efficiency in emulsion ROMP based on hydrophilic ruthenium alkylidene complexes. PMID:26664616

  2. Hexacoordinate Ru-based olefin metathesis catalysts with pH-responsive N-heterocyclic carbene (NHC) and N-donor ligands for ROMP reactions in non-aqueous, aqueous and emulsion conditions

    PubMed Central

    Balof, Shawna L; Nix, K Owen; Olliff, Matthew S; Roessler, Sarah E; Saha, Arpita; Müller, Kevin B; Behrens, Ulrich; Valente, Edward J

    2015-01-01

    Summary Three new ruthenium alkylidene complexes (PCy3)Cl2(H2ITap)Ru=CHSPh (9), (DMAP)2Cl2(H2ITap)Ru=CHPh (11) and (DMAP)2Cl2(H2ITap)Ru=CHSPh (12) have been synthesized bearing the pH-responsive H2ITap ligand (H2ITap = 1,3-bis(2’,6’-dimethyl-4’-dimethylaminophenyl)-4,5-dihydroimidazol-2-ylidene). Catalysts 11 and 12 are additionally ligated by two pH-responsive DMAP ligands. The crystal structure was solved for complex 12 by X-ray diffraction. In organic, neutral solution, the catalysts are capable of performing standard ring-opening metathesis polymerization (ROMP) and ring closing metathesis (RCM) reactions with standard substrates. The ROMP with complex 11 is accelerated in the presence of two equiv of H3PO4, but is reduced as soon as the acid amount increased. The metathesis of phenylthiomethylidene catalysts 9 and 12 is sluggish at room temperature, but their ROMP can be dramatically accelerated at 60 °C. Complexes 11 and 12 are soluble in aqueous acid. They display the ability to perform RCM of diallylmalonic acid (DAMA), however, their conversions are very low amounting only to few turnovers before decomposition. However, both catalysts exhibit outstanding performance in the ROMP of dicyclopentadiene (DCPD) and mixtures of DCPD with cyclooctene (COE) in acidic aqueous microemulsion. With loadings as low as 180 ppm, the catalysts afforded mostly quantitative conversions of these monomers while maintaining the size and shape of the droplets throughout the polymerization process. Furthermore, the coagulate content for all experiments stayed <2%. This represents an unprecedented efficiency in emulsion ROMP based on hydrophilic ruthenium alkylidene complexes. PMID:26664616

  3. Tandem ammonia borane dehydrogenation/alkene hydrogenation mediated by [Pd(NHC)(PR3)] (NHC = N-heterocyclic carbene) catalysts.

    PubMed

    Hartmann, Caroline E; Jurčík, Václav; Songis, Olivier; Cazin, Catherine S J

    2013-02-01

    [Pd(NHC)(PR(3))] complexes were shown to be active catalysts in the dehydrogenation of ammonia borane and the subsequent hydrogenation of unsaturated compounds at very low catalyst loadings (0.05 mol% for some substrates). PMID:23254388

  4. Recent developments in alkene hydro-functionalisation promoted by homogeneous catalysts based on earth abundant elements: formation of C-N, C-O and C-P bond.

    PubMed

    Rodriguez-Ruiz, Violeta; Carlino, Romain; Bezzenine-Lafollée, Sophie; Gil, Richard; Prim, Damien; Schulz, Emmanuelle; Hannedouche, Jérôme

    2015-07-21

    This Perspective article provides an overview of the recent advancements in the field of intra- and inter-molecular C-N, C-O and C-P bond formation by hydroamination, hydroalkoxylation, hydrophosphination, hydrophosphonylation or hydrophosphinylation of unactivated alkenes, including allenes, 1,3-dienes and strained alkenes, promoted by (chiral) homogeneous catalysts based on earth abundant elements of the s and p blocks, the first row transition metals and the rare-earth metals. The relevant literature from 2009 until late 2014 has been covered. PMID:25803322

  5. Metathesis of alkanes and related reactions.

    PubMed

    Basset, Jean-Marie; Copéret, Christophe; Soulivong, Daravong; Taoufik, Mostafa; Cazat, Jean Thivolle

    2010-02-16

    The transformation of alkanes remains a difficult challenge because of the relative inertness of the C-H and C-C bonds. The rewards for asserting synthetic control over unfunctionalized, saturated hydrocarbons are considerable, however, because converting short alkanes into longer chain analogues is usually a value-adding process. Alkane metathesis is a novel catalytic and direct transformation of two molecules of a given alkane into its lower and higher homologues; moreover, the process proceeds at relatively low temperature (ambient conditions or higher). It was discovered through the use of a silica-supported tantalum hydride, ([triple bond]SiO)(2)TaH, a multifunctional catalyst with a single site of action. This reaction completes the story of the metathesis reactions discovered over the past 40 years: olefin metathesis, alkyne metathesis, and ene-yne cyclizations. In this Account, we examine the fundamental mechanistic aspects of alkane metathesis as well as the novel reactions that have been derived from its study. The silica-supported tantalum hydride catalyst was developed as the result of systematic and meticulous studies of the interaction between oxide supports and organometallic complexes, a field of study denoted surface organometallic chemistry (SOMC). A careful examination of this surface-supported tantalum hydride led to the later discovery of alumina-supported tungsten hydride, W(H)(3)/Al(2)O(3), which proved to be an even better catalyst for alkane metathesis. Supported tantalum and tungsten hydrides are highly unsaturated, electron-deficient species that are very reactive toward the C-H and C-C bonds of alkanes. They show a great versatility in various other reactions, such as cross-metathesis between methane and alkanes, cross-metathesis between toluene and ethane, or even methane nonoxidative coupling. Moreover, tungsten hydride exhibits a specific ability in the transformation of isobutane into 2,3-dimethylbutane as well as in the metathesis

  6. Metal-Organic Frameworks Stabilize Solution-Inaccessible Cobalt Catalysts for Highly Efficient Broad-Scope Organic Transformations.

    PubMed

    Zhang, Teng; Manna, Kuntal; Lin, Wenbin

    2016-03-01

    New and active earth-abundant metal catalysts are critically needed to replace precious metal-based catalysts for sustainable production of commodity and fine chemicals. We report here the design of highly robust, active, and reusable cobalt-bipyridine- and cobalt-phenanthroline-based metal-organic framework (MOF) catalysts for alkene hydrogenation and hydroboration, aldehyde/ketone hydroboration, and arene C-H borylation. In alkene hydrogenation, the MOF catalysts tolerated a variety of functional groups and displayed unprecedentedly high turnover numbers of ∼2.5 × 10(6) and turnover frequencies of ∼1.1 × 10(5) h(-1). Structural, computational, and spectroscopic studies show that site isolation of the highly reactive (bpy)Co(THF)2 species in the MOFs prevents intermolecular deactivation and stabilizes solution-inaccessible catalysts for broad-scope organic transformations. Computational, spectroscopic, and kinetic evidence further support a hitherto unknown (bpy(•-))Co(I)(THF)2 ground state that coordinates to alkene and dihydrogen and then undergoing σ-complex-assisted metathesis to form (bpy)Co(alkyl)(H). Reductive elimination of alkane followed by alkene binding completes the catalytic cycle. MOFs thus provide a novel platform for discovering new base-metal molecular catalysts and exhibit enormous potential in sustainable chemical catalysis. PMID:26864496

  7. Carboxylation of alkylboranes by N-heterocyclic carbene copper catalysts: synthesis of carboxylic acids from terminal alkenes and carbon dioxide.

    PubMed

    Ohishi, Takeshi; Zhang, Liang; Nishiura, Masayoshi; Hou, Zhaomin

    2011-08-22

    Caught in the act: N-Heterocyclic carbene copper(I) complexes (1; IPr=1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) serve as an excellent catalyst for the carboxylation of alkylboranes (2; R=alkyl) with CO(2) to afford a variety of functionalized carboxylic acids (3) in high yields. A novel copper methoxide/alkylborane adduct (A) and its subsequent CO(2) insertion product (B) have been isolated and shown to be true active catalyst species. PMID:21739544

  8. 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

  9. Tandem Catalysis Utilizing Olefin Metathesis Reactions.

    PubMed

    Zieliński, Grzegorz K; Grela, Karol

    2016-07-01

    Since olefin metathesis transformation has become a favored synthetic tool in organic synthesis, more and more distinct non-metathetical reactions of alkylidene ruthenium complexes have been developed. Depending on the conditions applied, the same olefin metathesis catalysts can efficiently promote isomerization reactions, hydrogenation of C=C double bonds, oxidation reactions, and many others. Importantly, these transformations can be carried out in tandem with olefin metathesis reactions. Through addition of one portion of a catalyst, a tandem process provides structurally advanced products from relatively simple substrates without the need for isolation of the intermediates. These aspects not only make tandem catalysis very attractive from a practical point of view, but also open new avenues in (retro)synthetic planning. However, in the literature, the term "tandem process" is sometimes used improperly to describe other types of multi-reaction sequences. In this Concept, a number of examples of tandem catalysis involving olefin metathesis are discussed with an emphasis on their synthetic value. PMID:27203528

  10. Alkane metathesis by tandem alkane-dehydrogenation-olefin-metathesis catalysis and related chemistry.

    PubMed

    Haibach, Michael C; Kundu, Sabuj; Brookhart, Maurice; Goldman, Alan S

    2012-06-19

    Methods for the conversion of both renewable and non-petroleum fossil carbon sources to transportation fuels that are both efficient and economically viable could greatly enhance global security and prosperity. Currently, the major route to convert natural gas and coal to liquids is Fischer-Tropsch catalysis, which is potentially applicable to any source of synthesis gas including biomass and nonconventional fossil carbon sources. The major desired products of Fischer-Tropsch catalysis are n-alkanes that contain 9-19 carbons; they comprise a clean-burning and high combustion quality diesel, jet, and marine fuel. However, Fischer-Tropsch catalysis also results in significant yields of the much less valuable C(3) to C(8)n-alkanes; these are also present in large quantities in oil and gas reserves (natural gas liquids) and can be produced from the direct reduction of carbohydrates. Therefore, methods that could disproportionate medium-weight (C(3)-C(8)) n-alkanes into heavy and light n-alkanes offer great potential value as global demand for fuel increases and petroleum reserves decrease. This Account describes systems that we have developed for alkane metathesis based on the tandem operation of catalysts for alkane dehydrogenation and olefin metathesis. As dehydrogenation catalysts, we used pincer-ligated iridium complexes, and we initially investigated Schrock-type Mo or W alkylidene complexes as olefin metathesis catalysts. The interoperability of the catalysts typically represents a major challenge in tandem catalysis. In our systems, the rate of alkane dehydrogenation generally limits the overall reaction rate, whereas the lifetime of the alkylidene complexes at the relatively high temperatures required to obtain practical dehydrogenation rates (ca. 125 -200 °C) limits the total turnover numbers. Accordingly, we have focused on the development and use of more active dehydrogenation catalysts and more stable olefin-metathesis catalysts. We have used thermally

  11. Catalytic, Diastereoselective 1,2-Difluorination of Alkenes.

    PubMed

    Banik, Steven M; Medley, Jonathan William; Jacobsen, Eric N

    2016-04-20

    We describe a direct, catalytic approach to the 1,2-difluorination of alkenes. The method utilizes a nucleophilic fluoride source and an oxidant in conjunction with an aryl iodide catalyst and is applicable to alkenes with all types of substitution patterns. In general, the vicinal difluoride products are produced with high diastereoselectivities. The observed sense of stereoinduction implicates anchimeric assistance pathways in reactions of alkenes bearing neighboring Lewis basic functionality. PMID:27046019

  12. Complex polycyclic scaffolds by metathesis rearrangement of Himbert arene/allene cycloadducts.

    PubMed

    Lam, Jonathan K; Schmidt, Yvonne; Vanderwal, Christopher D

    2012-11-01

    The intramolecular arene/allene cycloaddition first described 30 years ago by Himbert and Henn permits rapid access to strained polycyclic compounds. Alkene metathesis processes cleanly rearrange appropriately substituted cycloadducts into complex, functional-group-rich polycyclic lactams of potential utility for natural product synthesis and medicinal chemistry. PMID:23067058

  13. Asymmetric fluorocyclizations of alkenes.

    PubMed

    Wolstenhulme, Jamie R; Gouverneur, Véronique

    2014-12-16

    .g., TRIP and derivatives) brings into solution the resulting chiral Selectfluor reagent, now capable of asymmetric fluorocyclization. This strategy is best applied to a subset of substrates bearing a nucleophilic pendent group (benzamide is best) capable of hydrogen bonding for association with the chiral phosphate catalyst. These contributions focused on fluoroheterocyclization involving either O- or N-nucleophiles. As for other halocyclizations, alkenes armed with π C-nucleophiles represent the most demanding class of substrates for asymmetric F(+)-induced electrophilic fluorination-cyclization. Successful implementation required the design of new chiral Selectfluor reagents featuring stereogenicity on the DABCO core. These reagents, accessible from chiral vicinal diamines, allowed the synthesis of unusual chiral fluorine-containing tetracyclic compounds, some composed of carbon, hydrogen, and fluorine exclusively. The challenges associated with F(+)-induced fluorocarbocyclizations prompted methodologists to consider chemistry where the Csp(3)-F bond formation event follows a catalyst-controlled cyclization. An exciting development built on in the area of transition metal π-cyclization of polyenes leading to cationic metal-alkyl intermediates. When intercepted by oxidative fluorodemetalation with a F(+) source, the resulting products are complex polycyclic structures emerging from an overall catalytic cascade fluorocarbocyclization. Complementing F(+)-based reactions, examples of fluorocyclizations with fluoride in the presence of an oxidant were reported. Despite some exciting developments, the field of asymmetric fluorocyclizations is in its infancy and undoubtedly requires new activation modes, catalysts, as well as F(+) and F(-) reagents to progress into general retrosynthetic approach toward enantioenriched fluorocycles. Numerous opportunities emerge, not least the use of a latent fluorine source as a means to minimize background fluorination. PMID:25379791

  14. New library of aminosulfonyl-tagged Hoveyda–Grubbs type complexes: Synthesis, kinetic studies and activity in olefin metathesis transformations

    PubMed Central

    Borré, Etienne; Caijo, Frederic

    2010-01-01

    Summary Seven novel Hoveyda–Grubbs precatalysts bearing an aminosulfonyl function are reported. Kinetic studies indicate an activity enhancement compared to Hoveyda’s precatalyst. A selection of these catalysts was investigated with various substrates in ring-closing metathesis of dienes or enynes and cross metathesis. The results demonstrate that these catalysts show a good tolerance to various chemical functions. PMID:21165173

  15. Iron(III)-catalysed carbonyl-olefin metathesis.

    PubMed

    Ludwig, Jacob R; Zimmerman, Paul M; Gianino, Joseph B; Schindler, Corinna S

    2016-05-19

    The olefin metathesis reaction of two unsaturated substrates is one of the most powerful carbon-carbon-bond-forming reactions in organic chemistry. Specifically, the catalytic olefin metathesis reaction has led to profound developments in the synthesis of molecules relevant to the petroleum, materials, agricultural and pharmaceutical industries. These reactions are characterized by their use of discrete metal alkylidene catalysts that operate via a well-established mechanism. While the corresponding carbonyl-olefin metathesis reaction can also be used to construct carbon-carbon bonds, currently available methods are scarce and severely hampered by either harsh reaction conditions or the required use of stoichiometric transition metals as reagents. To date, no general protocol for catalytic carbonyl-olefin metathesis has been reported. Here we demonstrate a catalytic carbonyl-olefin ring-closing metathesis reaction that uses iron, an Earth-abundant and environmentally benign transition metal, as a catalyst. This transformation accommodates a variety of substrates and is distinguished by its operational simplicity, mild reaction conditions, high functional-group tolerance, and amenability to gram-scale synthesis. We anticipate that these characteristics, coupled with the efficiency of this reaction, will allow for further advances in areas that have historically been enhanced by olefin metathesis. PMID:27120158

  16. Iron(III)-catalysed carbonyl–olefin metathesis

    NASA Astrophysics Data System (ADS)

    Ludwig, Jacob R.; Zimmerman, Paul M.; Gianino, Joseph B.; Schindler, Corinna S.

    2016-05-01

    The olefin metathesis reaction of two unsaturated substrates is one of the most powerful carbon–carbon-bond-forming reactions in organic chemistry. Specifically, the catalytic olefin metathesis reaction has led to profound developments in the synthesis of molecules relevant to the petroleum, materials, agricultural and pharmaceutical industries. These reactions are characterized by their use of discrete metal alkylidene catalysts that operate via a well-established mechanism. While the corresponding carbonyl–olefin metathesis reaction can also be used to construct carbon–carbon bonds, currently available methods are scarce and severely hampered by either harsh reaction conditions or the required use of stoichiometric transition metals as reagents. To date, no general protocol for catalytic carbonyl–olefin metathesis has been reported. Here we demonstrate a catalytic carbonyl–olefin ring-closing metathesis reaction that uses iron, an Earth-abundant and environmentally benign transition metal, as a catalyst. This transformation accommodates a variety of substrates and is distinguished by its operational simplicity, mild reaction conditions, high functional-group tolerance, and amenability to gram-scale synthesis. We anticipate that these characteristics, coupled with the efficiency of this reaction, will allow for further advances in areas that have historically been enhanced by olefin metathesis.

  17. AN EFFICIENT AND ECOFRIENDLY OXIDATION OF ALKENES USING IRON NITRATE AND MOLECULAR OXYGEN

    EPA Science Inventory

    An environmentally friendly solventless oxidation of alkenes is accomplished efficiently using relatively benign iron nitrate as catalyst in the pressence of molecular oxygen under pressurized conditions.

  18. Computational study of productive and non-productive cycles in fluoroalkene metathesis.

    PubMed

    Rybáčková, Markéta; Hošek, Jan; Šimůnek, Ondřej; Kolaříková, Viola; Kvíčala, Jaroslav

    2015-01-01

    A detailed DFT study of the mechanism of metathesis of fluoroethene, 1-fluoroethene, 1,1-difluoroethene, cis- and trans-1,2-difluoroethene, tetrafluoroethene and chlorotrifluoroethene catalysed with the Hoveyda-Grubbs 2(nd) generation catalyst was performed. It revealed that a successful metathesis of hydrofluoroethenes is hampered by a high preference for a non-productive catalytic cycle proceeding through a ruthenacyclobutane intermediate bearing fluorines in positions 2 and 4. Moreover, the calculations showed that the cross-metathesis of perfluoro- or perhaloalkenes should be a feasible process and that the metathesis is not very sensitive to stereochemical issues. PMID:26664636

  19. Computational study of productive and non-productive cycles in fluoroalkene metathesis

    PubMed Central

    Rybáčková, Markéta; Hošek, Jan; Šimůnek, Ondřej; Kolaříková, Viola

    2015-01-01

    Summary A detailed DFT study of the mechanism of metathesis of fluoroethene, 1-fluoroethene, 1,1-difluoroethene, cis- and trans-1,2-difluoroethene, tetrafluoroethene and chlorotrifluoroethene catalysed with the Hoveyda–Grubbs 2nd generation catalyst was performed. It revealed that a successful metathesis of hydrofluoroethenes is hampered by a high preference for a non-productive catalytic cycle proceeding through a ruthenacyclobutane intermediate bearing fluorines in positions 2 and 4. Moreover, the calculations showed that the cross-metathesis of perfluoro- or perhaloalkenes should be a feasible process and that the metathesis is not very sensitive to stereochemical issues. PMID:26664636

  20. Pt/[Fe]ZSM-5 modified by Na and Cs cations: an active and selective catalyst for dehydrogenation of n-alkanes to n-alkenes.

    PubMed

    Li, Xuebing; Iglesia, Enrique

    2008-02-01

    Pt clusters within [Fe]ZSM-5 channels provide active and stable sites for the selective catalytic dehydrogenation of n-alkanes to n-alkenes. Cs and Na cations titrate acid sites and inhibit skeletal isomerization and cracking side reactions. PMID:18209800

  1. Chemical Imaging of Catalyst Deactivation during the Conversion of Renewables at the Single Particle Level: The Etherification of Biomass-based Polyols with Alkenes over H-Beta Zeolites

    SciTech Connect

    A Parvulescu; D Mores; E Stavitski; C Teodorescu; P Bruijnicx; R Klein Gebbing; B Weckhuysen

    2011-12-31

    The etherification of biomass-based alcohols with various linear {alpha}-olefins under solvent-free conditions was followed in a space- and time-resolved manner on 9 {micro}m large H-Beta zeolite crystals by confocal fluorescence microscopy. This allowed us to visualize the interaction with the substrate and distribution of the coke products into the catalyst at the level of an individual zeolite crystal during the etherification process. The spectroscopic information obtained on the micrometer-scale zeolite was in line with the results obtained with bulk characterization techniques and further confirmed by the catalytic results obtained both for micrometer-scale and nanoscale zeolites. This allowed us to explain the influence of the substrate type (glycerol, glycols, and alkenes) and zeolite properties (Si/Al ratio and particle size) on the etherification activity. The etherification of the biomass-based alcohols takes place mainly on the external surface of the zeolite particles. The gradual blockage of the external surface of the zeolite results in a partial or total loss of etherification activity. The deactivation could be attributed to olefin oligomerization. The high conversions obtained in the etherification of 1,2-propylene glycol with long linear alkenes (up to 80%) and the pronounced deactivation of the zeolite observed in the etherification of glycerol with long linear alkenes (max. 20% conversion) were explained by the spectroscopic measurements and is due to differences in the adsorption, i.e., in the center of the zeolite particle for glycerol and on the external surface in the case of glycols.

  2. An Efficient Synthesis of (±)-Grandisol Featuring 1,5-Enyne Metathesis

    PubMed Central

    Graham, Thomas J. A.; Gray, Erin E.; Burgess, James M.; Goess, Brian C.

    2009-01-01

    An eight step synthesis of (±)-grandisol features a key sequence involving a high-yielding, microwave-assisted enyne metathesis to yield a 1-alkenylcyclobutene that is semihydrogenated to yield a silyl-protected grandisol. Metathesis catalyst screens revealed an intriguing trend whereby substrate conversion correlated strongly with the identity of the ligands on the catalyst. In addition, new reactivity of 1-alkenylcyclobutenes toward hydrogenation is described. PMID:19957923

  3. Z-Selective Olefin Metathesis on Peptides: Investigation of Side-Chain Influence, Preorganization, and Guidelines in Substrate Selection

    PubMed Central

    2015-01-01

    Olefin metathesis has emerged as a promising strategy for modulating the stability and activity of biologically relevant compounds; however, the ability to control olefin geometry in the product remains a challenge. Recent advances in the design of cyclometalated ruthenium catalysts has led to new strategies for achieving such control with high fidelity and Z selectivity, but the scope and limitations of these catalysts on substrates bearing multiple functionalities, including peptides, remained unexplored. Herein, we report an assessment of various factors that contribute to both productive and nonproductive Z-selective metathesis on peptides. The influence of sterics, side-chain identity, and preorganization through peptide secondary structure are explored by homodimerization, cross metathesis, and ring-closing metathesis. Our results indicate that the amino acid side chain and identity of the olefin profoundly influence the activity of cyclometalated ruthenium catalysts in Z-selective metathesis. The criteria set forth for achieving high conversion and Z selectivity are highlighted by cross metathesis and ring-closing metathesis on diverse peptide substrates. The principles outlined in this report are important not only for expanding the scope of Z-selective olefin metathesis to peptides but also for applying stereoselective olefin metathesis in general synthetic endeavors. PMID:25102124

  4. Synthesis of epoxybenzo[d]isothiazole 1,1-dioxides via a reductive-Heck, metathesis-sequestration protocol†‡

    PubMed Central

    Asad, Naeem; Hanson, Paul R.; Long, Toby R.; Rayabarapu, Dinesh K.; Rolfe, Alan

    2011-01-01

    An atom-economical purification protocol, using solution phase processing via ring-opening metathesis polymerization (ROMP) has been developed for the synthesis of tricyclic sultams. This chromatography-free method allows for convenient isolation of reductive-Heck products and reclamation of excess starting material via sequestration involving metathesis catalysts and a catalyst-armed Si-surface. PMID:21727956

  5. 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

  6. Ru complexes of Hoveyda–Grubbs type immobilized on lamellar zeolites: activity in olefin metathesis reactions

    PubMed Central

    Žilková, Naděžda; Kubů, Martin; Mazur, Michal; Bastl, Zdeněk; Čejka, Jiří

    2015-01-01

    Summary Hoveyda–Grubbs type catalysts with cationic tags on NHC ligands were linker-free immobilized on the surface of lamellar zeolitic supports (MCM-22, MCM-56, MCM-36) and on mesoporous molecular sieves SBA-15. The activity of prepared hybrid catalysts was tested in olefin metathesis reactions: the activity in ring-closing metathesis of citronellene and N,N-diallyltrifluoroacetamide decreased in the order of support MCM-22 ≈ MCM-56 > SBA-15 > MCM-36; the hybrid catalyst based on SBA-15 was found the most active in self-metathesis of methyl oleate. All catalysts were reusable and exhibited low Ru leaching (<1% of Ru content). XPS analysis revealed that during immobilization ion exchange between Hoveyda–Grubbs type catalyst and zeolitic support occurred in the case of Cl− counter anion; in contrast, PF6 − counter anion underwent partial decomposition. PMID:26664629

  7. Room Temperature Hydrosilylation of Silicon Nanocrystals with Bifunctional Terminal Alkenes

    PubMed Central

    Yu, Yixuan; Hessel, Colin M.; Bogart, Timothy; Panthani, Matthew G.; Rasch, Michael R.; Korgel, Brian A.

    2013-01-01

    H-terminated Si nanocrystals undergo room temperature hydrosilylation with bifunctional alkenes with distal polar moieties—ethyl-, methyl-ester or carboxylic acids—without the aid of light or added catalyst. The passivated Si nanocrystals exhibit bright photoluminescence (PL) and disperse in polar solvents, including water. We propose a reaction mechanism in which ester or carboxylic acid groups facilitate direct nucleophilic attack of the highly curved Si surface of the nanocrystals by the alkene. PMID:23312033

  8. Ruthenium Carbene Mediated Metathesis of Oleate-Type Fatty Compounds

    PubMed Central

    Marvey, Bassie B.; Segakweng, Constance K.; Vosloo, Manie H. C.

    2008-01-01

    The complexes RuCl2(PCy3)2(=CHPh), 1, and RuCl2(PCy3)(H2IMes)(=CHPh), 2, proved to be active catalysts for the self-metathesis of oleate-type fatty compounds containing the ester, hydroxyl, epoxy and carboxylic acid functional groups. At elevated reaction temperatures 2 showed a higher activity, stability and lower selectivity for primary metathesis products compared to 1. A profound influence of organic functional groups on catalyst activity and selectivity was found and from relative activities and selectivities 2 has proved to be more resistant to deactivation by polar functional groups and more inclined to promote double bond isomerisation than 1. The observed catalyst deactivation by oxygen-containing functional groups could be attributed to a phosphine displacement side reaction. PMID:19325774

  9. Base-Metal-Catalyzed Regiodivergent Alkene Hydrosilylations.

    PubMed

    Du, Xiaoyong; Zhang, Yanlu; Peng, Dongjie; Huang, Zheng

    2016-06-01

    A complementary set of base metal catalysts has been developed for regiodivergent alkene hydrosilylations: iron complexes of phosphine-iminopyridine are selective for anti-Markovnikov hydrosilylations (linear/branched up to >99:1), while the cobalt complexes bearing the same type of ligands provide an unprecedented high level of Markovnikov selectivity (branched/linear up to >99:1). Both systems exhibit high efficiency and wide functional group tolerance. PMID:27111001

  10. Prosodically Driven Metathesis in Mutsun

    ERIC Educational Resources Information Center

    Butler, Lynnika

    2013-01-01

    Among the many ways in which sounds alternate in the world's languages, changes in the order of sounds (metathesis) are relatively rare. Mutsun, a Southern Costanoan language of California which was documented extensively before the death of its last speaker in 1930, displays three patterns of synchronic consonant-vowel (CV) metathesis. Two of…

  11. Effects of NHC-backbone substitution on efficiency in ruthenium-based olefin metathesis.

    PubMed

    Kuhn, Kevin M; Bourg, Jean-Baptiste; Chung, Cheol K; Virgil, Scott C; Grubbs, Robert H

    2009-04-15

    A series of ruthenium olefin metathesis catalysts bearing N-heterocyclic carbene (NHC) ligands with varying degrees of backbone and N-aryl substitution have been prepared. These complexes show greater resistance to decomposition through C-H activation of the N-aryl group, resulting in increased catalyst lifetimes. This work has utilized robotic technology to examine the activity and stability of each catalyst in metathesis, providing insights into the relationship between ligand architecture and enhanced efficiency. The development of this robotic methodology has also shown that, under optimized conditions, catalyst loadings as low as 25 ppm can lead to 100% conversion in the ring-closing metathesis of diethyl diallylmalonate. PMID:19351207

  12. Light-induced olefin metathesis

    PubMed Central

    Vidavsky, Yuval

    2010-01-01

    Summary Light activation is a most desirable property for catalysis control. Among the many catalytic processes that may be activated by light, olefin metathesis stands out as both academically motivating and practically useful. Starting from early tungsten heterogeneous photoinitiated metathesis, up to modern ruthenium methods based on complex photoisomerisation or indirect photoactivation, this survey of the relevant literature summarises past and present developments in the use of light to expedite olefin ring-closing, ring-opening polymerisation and cross-metathesis reactions. PMID:21160912

  13. 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

  14. Photocatalytic oxidation of alkenes and alcohols in water by a manganese(v) nitrido complex.

    PubMed

    Chen, Gui; Chen, Lingjing; Ma, Li; Kwong, Hoi-Ki; Lau, Tai-Chu

    2016-07-28

    Mn(v) nitrido complex [Mn(N)(CN)4](2-) is an efficient catalyst for visible-light induced oxidation of alkenes and alcohols in water using [Ru(bpy)3](2+) as a photosensitizer and [Co(NH3)5Cl](2+) as a sacrificial oxidant. Alkenes are oxidized to epoxides and alcohols to carbonyl compounds. PMID:27358025

  15. 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. PMID:26878987

  16. 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.

  17. 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

  18. Simple activation by acid of latent Ru-NHC-based metathesis initiators bearing 8-quinolinolate co-ligands

    PubMed Central

    Wappel, Julia; Fischer, Roland C; Cavallo, Luigi; Slugovc, Christian

    2016-01-01

    Summary A straightforward synthesis utilizing the ring-opening metathesis polymerization (ROMP) reaction is described for acid-triggered N,O-chelating ruthenium-based pre-catalysts bearing one or two 8-quinolinolate ligands. The innovative pre-catalysts were tested regarding their behavior in ROMP and especially for their use in the synthesis of poly(dicyclopentadiene) (pDCPD). Bearing either the common phosphine leaving ligand in the first and second Grubbs olefin metathesis catalysts, or the Ru–O bond cleavage for the next Hoveyda-type catalysts, this work is a step forward towards the control of polymer functionalization and living or switchable polymerizations. PMID:26877818

  19. Predicting the enantioselectivity of the copper-catalysed cyclopropanation of alkenes by using quantitative quadrant-diagram representations of the catalysts.

    PubMed

    Aguado-Ullate, Sonia; Urbano-Cuadrado, Manuel; Villalba, Isabel; Pires, Elísabet; García, José I; Bo, Carles; Carbó, Jorge J

    2012-10-29

    We present a new methodology to predict the enantioselectivity of asymmetric catalysis based on quantitative quadrant-diagram representations of the catalysts and quantitative structure-selectivity relationship (QSSR) modelling. To account for quadrant occupation, we used two types of molecular steric descriptors: the Taft-Charton steric parameter (ν(Charton)) and the distance-weighted volume (V(W) ). By assigning the value of the steric descriptors to each of the positions of the quadrant diagram, we generated the independent variables to build the multidimensional QSSR models. The methodology was applied to predict the enantioselectivity in the cyclopropanation of styrene catalysed by copper complexes. The dataset comprised 30 chiral ligands belonging to four different oxazoline-based ligand families: bis- (Box), azabis- (AzaBox), quinolinyl- (Quinox) and pyridyl-oxazoline (Pyox). In the first-order approximation, we generated QSSR models with good predictive ability (r(2) =0.89 and q(2) =0.88). The derived stereochemical model indicated that placing very large groups at two diagonal quadrants and leaving free the other two might be enough to obtain an enantioselective catalyst. Fitting the data to a higher-order polynomial, which included crossterms between the descriptors of the quadrants, resulted in an improvement of the predicting ability of the QSSR model (r(2) =0.96 and q(2) =0.93). This suggests that the relationship between the steric hindrance and the enantioselectivity is non-linear, and that bulky substituents in diagonal quadrants operate synergistically. We believe that the quantitative quadrant-diagram-based QSSR modelling is a further conceptual tool that can be used to predict the selectivity of chiral catalysts and other aspects of catalytic performance. PMID:22987760

  20. Olefin Metathesis Reaction in Water and in Air Improved by Supramolecular Additives.

    PubMed

    Tomasek, Jasmine; Seßler, Miriam; Gröger, Harald; Schatz, Jürgen

    2015-01-01

    A range of water-immiscible commercially available Grubbs-type precatalysts can be used in ring-closing olefin metathesis reaction in high yields. The synthetic transformation is possible in pure water under ambient conditions. Sulfocalixarenes can help to boost the reactivity of the metathesis reaction by catalyst activation, improved mass transfer, and solubility of reactants in the aqueous reaction media. Additionally, the use of supramolecular additives allows lower catalyst loadings, but still high activity in pure water under aerobic conditions. PMID:26506329

  1. Sunflower-based Feedstocks in Nonfood Applications: Perspectives from Olefin Metathesis

    PubMed Central

    Marvey, Bassie B.

    2008-01-01

    Sunflower (Helianthus annuus L.) oil remains under-utilised albeit one of the major seed oils produced world-wide. Moreover, the high oleic sunflower varieties make the oil attractive for applications requiring high temperature processes and those targeting the C=C double bond functionality. Herein an overview of the recent developments in olefin metathesis of sunflower-based feedstocks is presented. The improved performance of olefin metathesis catalysts leading to high turnover numbers, high selectivity and catalyst recyclability, opens new opportunities for tailoring sunflower-based feedstocks into products required for possible new niche market applications. Promising results in biofuel, biopolymers, fragrances and fine chemicals applications have been reported. PMID:19325810

  2. Gold-Catalyzed Anti-Markovnikov Selective Hydrothiolation of Unactivated Alkenes.

    PubMed

    Tamai, Taichi; Fujiwara, Keiko; Higashimae, Shinya; Nomoto, Akihiro; Ogawa, Akiya

    2016-05-01

    Despite the widespread use of transition-metal catalysts in organic synthesis, transition-metal-catalyzed reactions of organosulfur compounds, which are known as catalyst poisons, have been difficult. In particular, the transition-metal-catalyzed addition of organosulfur compounds to unactivated alkenes remains a challenge. A novel gold-catalyzed hydrothiolation of unactivated alkenes is presented, which proceeds effectively to give the anti-Markovnikov-selective adducts in good yields and in a regioselective manner. PMID:27057590

  3. Catalytic and Atom-Economic Intermolecular Amidoselenenylation of Alkenes.

    PubMed

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

    2016-01-15

    A method for the simple, efficient, and atom-economic amidoselenenylation of simple alkenes under mild conditions using TiCl4 as a catalyst and N-(phenylseleno)phthalimide as both a nitrogen and selenium source was developed. A broad range of olefins can be applied to afford vicinal amidoselenides in good yield and with high regioselectivity and diastereoselectivity. PMID:26704901

  4. Synthesis of interlocked molecules by olefin metathesis

    NASA Astrophysics Data System (ADS)

    Clark, Paul Gregory

    A large body of work in the Grubbs group has focused on the development of functional-group tolerant ruthenium alkylidene catalysts that perform a number of olefin metathesis reactions. These catalysts have seen application in a wide range of fields, including classic total synthesis as well as polymer and materials chemistry. One particular family of compounds, interlocked molecules, has benefitted greatly from these advances in catalyst stability and activity. This thesis describes several elusive and challenging interlocked architectures whose syntheses have been realized through the utilization of different types of ruthenium-catalyzed olefin metathesis reactions. Ring-closing olefin metathesis has enabled the synthesis of a [c2]daisy-chain dimer with the ammonium binding site near the cap of the dimer. A deprotonated DCD possessing such a structural attribute will more forcefully seek to restore coordinating interactions upon reprotonation, enhancing its utility as a synthetic molecular actuator. Dimer functionalization facilitated incorporation into linear polymers, with a 48% size increase of an unbound, extended analogue of the polymer demonstrating slippage of the dimer units. Ongoing work is directed at further materials studies, in particular, exploring the synthesis of macroscopic networks containing the DCD units and analyzing the correlation between molecular-scale extension-contraction manipulations and resulting macro-scale changes. A "clipping" approach to a polycatenated cyclic polymer, a structure that resembles a molecular "charm bracelet", has been described. The use of ring-opening metathesis polymerization of a carbamate monomer in the presence of a chain transfer agent allowed for the synthesis of a linear polymer that was subsequently functionalized and cyclized to the corresponding cyclic analogue. This cyclic polymer was characterized through a variety of techniques, and subjected to further functionalization reactions, affording a cyclic

  5. Alkenes in [2+2+2] Cycloadditions.

    PubMed

    Domínguez, Gema; Pérez-Castells, Javier

    2016-05-10

    Participation of alkenes and allenes in [2+2+2] cycloaddition reactions has attracted much attention recently. This version of the well-established alkyne cyclotrimerization renders interesting products, such as cyclohexadienes and other polycycles, through cascade processes. Many mechanistic variations are observed when using certain metal complexes as catalysts. The frequent generation of stereogenic centers has prompted the development of efficient asymmetric versions. This Minireview summarizes the efforts reported to date on the use of double bonds as partners in [2+2+2] cyclotrimerizations. PMID:26918553

  6. Metathesis process for preparing an alpha, omega-functionalized olefin

    DOEpatents

    Burdett, Kenneth A.; Mokhtarzadeh, Morteza; Timmers, Francis J.

    2010-10-12

    A cross-metathesis process for preparing an .alpha.,.omega.-functionalized olefin, such as methyl 9-decenoate, and an .alpha.-olefin having three or more carbon atoms, such as 1-decene. The process involves contacting in a first reaction zone an .alpha.-functionalized internal olefin, such as methyl oleate, and an .alpha.-olefinic monomer having three or more carbon atoms, such as 1-decene, with a first metathesis catalyst to prepare an effluent stream containing the .alpha.,.omega.-functionalized olefin, such as methyl 9-decenoate, an unfunctionalized internal olefin, such as 9-octadecene, unconverted reactant olefins, and optionally, an .alpha.,.omega.-difunctionalized internal olefinic dimer, such as dimethyl 9-octadecen-1,18-dioate; separating said effluent streams; then contacting in a second reaction zone the unfunctionalized internal olefin with ethylene in the presence of a second metathesis catalyst to obtain a second product effluent containing the .alpha.-olefinic monomer having three or more carbon atoms; and cycling a portion of the .alpha.-olefinic monomer stream(s) to the first zone.

  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. Ruthenium Vinyl Carbene Intermediates in Enyne Metathesis

    PubMed Central

    Diver, Steven T.

    2009-01-01

    This review provides an overview of ruthenium vinyl carbene reactivity as it relates to enyne metathesis. Methods for the synthesis of metathesis-active and metathesis-inactive complexes are also summarized. Some of the early hypotheses about vinyl carbene intermediates in enyne metatheses were tested in the arena of synthetic chemistry and subsequently led to mechanistic studies. In these two areas, studies from the author's labs are described. There are still many unresolved questions in enyne metathesis that trace back to vinyl carbene reactivity. Hopefully this review will stimulate further investigation into vinyl carbene reactivity which should further refine our understanding of catalytic enyne metathesis. PMID:19590747

  9. Kinetically controlled E-selective catalytic olefin metathesis.

    PubMed

    Nguyen, Thach T; Koh, Ming Joo; Shen, Xiao; Romiti, Filippo; Schrock, Richard R; Hoveyda, Amir H

    2016-04-29

    A major shortcoming in olefin metathesis, a chemical process that is central to research in several branches of chemistry, is the lack of efficient methods that kinetically favor E isomers in the product distribution. Here we show that kinetically E-selective cross-metathesis reactions may be designed to generate thermodynamically disfavored alkenyl chlorides and fluorides in high yield and with exceptional stereoselectivity. With 1.0 to 5.0 mole % of a molybdenum-based catalyst, which may be delivered in the form of air- and moisture-stable paraffin pellets, reactions typically proceed to completion within 4 hours at ambient temperature. Many isomerically pure E-alkenyl chlorides, applicable to catalytic cross-coupling transformations and found in biologically active entities, thus become easily and directly accessible. Similarly, E-alkenyl fluorides can be synthesized from simpler compounds or more complex molecules. PMID:27126041

  10. Ring-Closing Metathesis: An Advanced Guided-Inquiry Experiment for the Organic Laboratory

    ERIC Educational Resources Information Center

    Schepmann, Hala G.; Mynderse, Michelle

    2010-01-01

    The design and implementation of an advanced guided-inquiry experiment for the organic laboratory is described. Grubbs's second-generation catalyst is used to effect the ring-closing metathesis of diethyl diallylmalonate. The reaction is carried out under an inert atmosphere at room temperature and monitored by argentic TLC. The crude reaction is…

  11. Intramolecular σ-bond metathesis between carbon-carbon and silicon-silicon bonds.

    PubMed

    Ishida, Naoki; Ikemoto, Wataru; Murakami, Masahiro

    2012-06-15

    An intramolecular σ-bond metathesis between carbon-carbon and silicon-silicon bonds took place on treatment of a disilane tethered to a cyclobutanone with a palladium(0) catalyst, furnishing a silaindane skeleton as well as an acylsilane functionality at once. PMID:22651103

  12. A ring closing metathesis strategy for carbapyranosides of xylose and arabinose.

    PubMed

    Mattis, Clayton E; Mootoo, David R

    2016-06-24

    The synthesis of β-carba-xylo and arabino pyranosides of cholestanol is described. The synthetic strategy, which is analogous to the Postema approach to C-glycosides, centers on the ring closing metathesis of an enol ether-alkene precursor to give a cyclic enol ether that is elaborated to a carba-pyranoside via hydroboration-oxidation on the olefin. The method, which is attractive for its modularity and stereoselectivity, may find wider applications to carba-hexopyranosides and other complex cycloalkyl ether frameworks. PMID:27236269

  13. A ring closing metathesis strategy for carbapyranosides of xylose and arabinose.

    PubMed

    Mattis, Clayton E; Mootoo, David R

    2016-04-29

    The synthesis of β-carba-xylo and arabino pyranosides of cholestanol is described. The synthetic strategy, which is analogous to the Postema approach to C-glycosides, centers on the ring closing metathesis of an enol ether-alkene precursor to give a cyclic enol ether that is elaborated to a carba-pyranoside via hydroboration-oxidation on the olefin. The method, which is attractive for its modularity and stereoselectivity, may find wider applications to carba-hexopyranosides and other complex cycloalkyl ether frameworks. PMID:27035910

  14. A Thermo- and Photo-Switchable Ruthenium Initiator For Olefin Metathesis.

    PubMed

    Sashuk, Volodymyr; Danylyuk, Oksana

    2016-05-01

    A ruthenium carbene complex bearing azobenzene functionality is reported. The complex exists in the form of two isomers differing by the size of the chelate ring. Both isomers were isolated by applying kinetic or thermodynamic control during the synthesis and characterized by X-ray diffraction analysis. The isomerization of the complex was studied by UV/Vis spectroscopy. The stable isomer was tested as a catalyst in olefin metathesis. The complex was activated at about 100 °C to promote ring-closing and ring-opening polymerization metathesis reactions. The activation took place also at room temperature under middle ultraviolet radiation. PMID:27004928

  15. 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...

  16. Chemoselective single-site Earth-abundant metal catalysts at metal-organic framework nodes.

    PubMed

    Manna, Kuntal; Ji, Pengfei; Lin, Zekai; Greene, Francis X; Urban, Ania; Thacker, Nathan C; Lin, Wenbin

    2016-01-01

    Earth-abundant metal catalysts are critically needed for sustainable chemical synthesis. Here we report a simple, cheap and effective strategy of producing novel earth-abundant metal catalysts at metal-organic framework (MOF) nodes for broad-scope organic transformations. The straightforward metalation of MOF secondary building units (SBUs) with cobalt and iron salts affords highly active and reusable single-site solid catalysts for a range of organic reactions, including chemoselective borylation, silylation and amination of benzylic C-H bonds, as well as hydrogenation and hydroboration of alkenes and ketones. Our structural, spectroscopic and kinetic studies suggest that chemoselective organic transformations occur on site-isolated, electron-deficient and coordinatively unsaturated metal centres at the SBUs via σ-bond metathesis pathways and as a result of the steric environment around the catalytic site. MOFs thus provide a novel platform for the development of highly active and affordable base metal catalysts for the sustainable synthesis of fine chemicals. PMID:27574182

  17. 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)

  18. Catalytic synthesis of n-alkyl arenes through alkyl group cross-metathesis.

    PubMed

    Dobereiner, Graham E; Yuan, Jian; Schrock, Richard R; Goldman, Alan S; Hackenberg, Jason D

    2013-08-28

    n-Alkyl arenes were prepared in a one-pot tandem dehydrogenation/olefin metathesis/hydrogenation sequence directly from alkanes and ethylbenzene. Excellent selectivity was observed when ((tBu)PCP)IrH2 was paired with tungsten monoaryloxide pyrrolide complexes such as W(NAr)(C3H6)(pyr)(OHIPT) (1a) [Ar = 2,6-i-Pr2C6H3; pyr = pyrrolide; OHIPT = 2,6-(2,4,6-i-Pr3C6H2)2C6H3O]. Complex 1a was also especially active in n-octane self-metathesis, providing the highest product concentrations reported to date. The thermal stability of selected olefin metathesis catalysts allowed elevated temperatures and extended reaction times to be employed. PMID:23909821

  19. Epoxidation catalyst and process

    DOEpatents

    Linic, Suljo; Christopher, Phillip

    2010-10-26

    Disclosed herein is a catalytic method of converting alkenes to epoxides. This method generally includes reacting alkenes with oxygen in the presence of a specific silver catalyst under conditions suitable to produce a yield of the epoxides. The specific silver catalyst is a silver nanocrystal having a plurality of surface planes, a substantial portion of which is defined by Miller indices of (100). The reaction is performed by charging a suitable reactor with this silver catalyst and then feeding the reactants to the reactor under conditions to carry out the reaction. The reaction may be performed in batch, or as a continuous process that employs a recycle of any unreacted alkenes. The specific silver catalyst has unexpectedly high selectivity for epoxide products. Consequently, this general method (and its various embodiments) will result in extraordinarily high epoxide yields heretofore unattainable.

  20. 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

  1. Regioselective Intermolecular Diamination and Aminooxygenation of Alkenes with Saccharin.

    PubMed

    Martínez, Claudio; Pérez, Edwin G; Iglesias, Álvaro; Escudero-Adán, Eduardo C; Muñiz, Kilian

    2016-06-17

    Palladium catalysis enables the regioselective difunctionalization of alkenes using saccharin as the nitrogen source in the initial step of aminopalladation. Depending on the reaction conditions, diamination or aminooxygenation pathways can be accessed using hypervalent iodine reagents as the terminal oxidants. The aminooxygenation of allylic ethers originates from an unprecedented ambident behavior of saccharin. The participating palladium catalysts contain a palladium-saccharide unit. Two representative complexes of this type could be isolated and characterized. PMID:27266654

  2. Catalyst system comprising a first catalyst system tethered to a supported catalyst

    DOEpatents

    Angelici, Robert J.; Gao, Hanrong

    1998-08-04

    The present invention provides new catalyst formats which comprise a supported catalyst tethered to a second and different catalyst by a suitable tethering ligand. A preferred system comprises a heterogeneous supported metal catalyst tethered to a homogeneous catalyst. This combination of homogeneous and heterogeneous catalysts has a sufficient lifetime and unusually high catalytic activity in arene hydrogenations, and potentially many other reactions as well, including, but not limited to hydroformylation, hydrosilation, olefin oxidation, isomerization, hydrocyanation, olefin metathesis, olefin polymerization, carbonylation, enantioselective catalysis and photoduplication. These catalysts are easily separated from the products, and can be reused repeatedly, making these systems very economical.

  3. Catalyst system comprising a first catalyst system tethered to a supported catalyst

    DOEpatents

    Angelici, R.J.; Gao, H.

    1998-08-04

    The present invention provides new catalyst formats which comprise a supported catalyst tethered to a second and different catalyst by a suitable tethering ligand. A preferred system comprises a heterogeneous supported metal catalyst tethered to a homogeneous catalyst. This combination of homogeneous and heterogeneous catalysts has a sufficient lifetime and unusually high catalytic activity in arene hydrogenations, and potentially many other reactions as well, including, but not limited to hydroformylation, hydrosilication, olefin oxidation, isomerization, hydrocyanidation, olefin metathesis, olefin polymerization, carbonylation, enantioselective catalysis and photoduplication. These catalysts are easily separated from the products, and can be reused repeatedly, making these systems very economical. 2 figs.

  4. Anaerobic biotransformation of chlorinated alkenes

    SciTech Connect

    Zhuang, P.

    1994-01-01

    Chlorinated alkenes are widely found in contaminated subsurface soil and groundwater. The highly chlorinated alkene (i.e., PCE) is not subject to aerobic biotransformation. The aim of this research was to explore the potential of using anaerobic processes (i.e., denitrification, sulfate-reduction and methanogenesis) for chlorinated alkenes biotransformation. Contaminated soil samples were used throughout this study. Soil microcosms simulating field anoxic conditions with various nutrients amendment, liquid microcosms as well as enrichment liquid cultures were developed to delineate the dechlorination process. The effect of biomass, chlorinated alkenes concentration and site specific conditions (e.g., temperature and pH) on the dechlorination and the primary metabolic process was investigated. The role of sorption and nutritional needs (i.e., electron donor) were also studied. A preliminary study revealed that denitrification was the least affected by low temperatures as compared to sulfate-reduction and methanogenesis. Although dechlorination took place under sequential denitrifying and methanogenic conditions and under sulfate-reducing conditions, further studies concluded that fermentative and methanogenic bacteria were responsible for the observed dechlorination. In most cases, dechlorination of PCE or TCE resulted in the accumulation of cDCE. However, a VC-producing culture was developed from the PCE-contaminated soil. In general, the dechlorination process could be enhanced by increasing electron donor and biomass concentration. At relatively low concentrations, the dechlorination rate was also increased with increasing chlorinated alkene concentration. Dechlorination even proceeded at high chlorinated alkene concentrations when methane production was inhibited. However, as the concentration of the chlorinated alkenes increased, severe toxicity eventually halted the dechlorination process.

  5. Catalytic living ring-opening metathesis polymerization

    NASA Astrophysics Data System (ADS)

    Nagarkar, Amit A.; Kilbinger, Andreas F. M.

    2015-09-01

    In living ring-opening metathesis polymerization (ROMP), a transition-metal-carbene complex polymerizes ring-strained olefins with very good control of the molecular weight of the resulting polymers. Because one molecule of the initiator is required for each polymer chain, however, this type of polymerization is expensive for widespread use. We have now designed a chain-transfer agent (CTA) capable of reducing the required amount of metal complex while still maintaining full control over the living polymerization process. This new method introduces a degenerative transfer process to ROMP. We demonstrate that substituted cyclohexene rings are good CTAs, and thereby preserve the ‘living’ character of the polymerization using catalytic quantities of the metal complex. The resulting polymers show characteristics of a living polymerization, namely narrow molecular-weight distribution, controlled molecular weights and block copolymer formation. This new technique provides access to well-defined polymers for industrial, biomedical and academic use at a fraction of the current costs and significantly reduced levels of residual ruthenium catalyst.

  6. Candle and candle wax containing metathesis and metathesis-like products

    SciTech Connect

    Murphy, Timothy A; Tupy, Michael J; Abraham, Timothy W; Shafer, Andy

    2014-04-01

    A wax comprises a metathesis product and/or a product that resembles, at least in part, a product which may be formed from a metathesis reaction. The wax may be used to form articles, for example, candles (container candles, votive candles, and/or a pillar candles), crayons, fire logs, or tarts. The wax commonly includes other components in addition to the metathesis product.

  7. Candle and candle wax containing metathesis and metathesis-like products

    DOEpatents

    Murphy, Timothy A; Tupy, Michael J; Abraham, Timothy W; Shafer, Andy

    2014-12-16

    A wax comprises a metathesis product and/or a product that resembles, at least in part, a product which may be formed from a metathesis reaction. The wax may be used to form articles for example, candles (container candles, votive candles, and/or a pillar candles), crayons, fire logs or tarts. The wax commonly includes other components in addition to the metathesis product.

  8. High-Performance Isocyanide Scavengers for Use in Low-Waste Purification of Olefin Metathesis Products

    PubMed Central

    Szczepaniak, Grzegorz; Urbaniak, Katarzyna; Wierzbicka, Celina; Kosiński, Krzysztof; Skowerski, Krzysztof; Grela, Karol

    2015-01-01

    Three isocyanides containing a tertiary nitrogen atom were investigated for use as small-molecule ruthenium scavenging agents in the workup of olefin metathesis reactions. The proposed compounds are odorless, easy to obtain, and highly effective in removing metal residues, sometimes bringing the metal content below 0.0015 ppm. The most successful of the tested compounds, II, performs very well, even with challenging polar products. The performance of these scavengers is compared and contrasted with other known techniques, such as silica gel filtration and the use of self-scavenging catalysts. As a result, a new hybrid purification method is devised, which gives better results than using either a self-scavenging catalyst or a scavenger alone. Additionally, isocyanide II is shown to be a deactivating (reaction quenching) agent for olefin metathesis and superior to ethyl vinyl ether. PMID:26556779

  9. 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

  10. Rapid assembly of structurally defined and highly functionalized conjugated dienes via tethered enyne metathesis.

    PubMed

    Yao, Q

    2001-06-28

    [reaction: see text] Conjugated dienes are versatile building blocks in organic synthesis, and the development of new methods for their synthesis remains an important topic in modern synthetic organic chemistry. We describe here an expedient synthesis of highly functionalized conjugated dienes through sequential silicon-tethered ring-closing enyne metathesis mediated by Grubbs' Ru carbene catalysts and Tamao oxidation. Notable attributes of this methodology include short synthetic manipulations and the structural complexity it confers on the resulting diene moiety. PMID:11418051

  11. 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.

  12. Cross-metathesis of polynorbornene with polyoctenamer: a kinetic study

    PubMed Central

    Denisova, Yulia I; Gringolts, Maria L; Peregudov, Alexander S; Krentsel, Liya B; Litmanovich, Ekaterina A; Litmanovich, Arkadiy D; Finkelshtein, Eugene Sh

    2015-01-01

    Summary The cross-metathesis of polynorbornene and polyoctenamer in d-chloroform mediated by the 1st generation Grubbs’ catalyst Cl2(PCy3)2Ru=CHPh is studied by monitoring the kinetics of carbene transformation and evolution of the dyad composition of polymer chains with in situ 1H and ex situ 13C NMR spectroscopy. The results are interpreted in terms of a simple kinetic two-stage model. At the first stage of the reaction all Ru-benzylidene carbenes are transformed into Ru-polyoctenamers within an hour, while the polymer molar mass is considerably decreased. The second stage actually including interpolymeric reactions proceeds much slower and takes one day or more to achieve a random copolymer of norbornene and cyclooctene. Its rate is limited by the interaction of polyoctenamer-bound carbenes with polynorbornene units, which is hampered, presumably due to steric reasons. Polynorbornene-bound carbenes are detected in very low concentrations throughout the whole process thus indicating their higher reactivity, as compared with the polyoctenamer-bound ones. Macroscopic homogeneity of the reacting media is proved by dynamic light scattering from solutions containing the polymer mixture and its components. In general, the studied process can be considered as a new way to unsaturated multiblock statistical copolymers. Their structure can be controlled by the amount of catalyst, mixture composition, and reaction time. It is remarkable that this goal can be achieved with a catalyst that is not suitable for ring-opening metathesis copolymerization of norbornene and cis-cyclooctene because of their substantially different monomer reactivities. PMID:26664599

  13. Cross-metathesis of polynorbornene with polyoctenamer: a kinetic study.

    PubMed

    Denisova, Yulia I; Gringolts, Maria L; Peregudov, Alexander S; Krentsel, Liya B; Litmanovich, Ekaterina A; Litmanovich, Arkadiy D; Finkelshtein, Eugene Sh; Kudryavtsev, Yaroslav V

    2015-01-01

    The cross-metathesis of polynorbornene and polyoctenamer in d-chloroform mediated by the 1(st) generation Grubbs' catalyst Cl2(PCy3)2Ru=CHPh is studied by monitoring the kinetics of carbene transformation and evolution of the dyad composition of polymer chains with in situ (1)H and ex situ (13)C NMR spectroscopy. The results are interpreted in terms of a simple kinetic two-stage model. At the first stage of the reaction all Ru-benzylidene carbenes are transformed into Ru-polyoctenamers within an hour, while the polymer molar mass is considerably decreased. The second stage actually including interpolymeric reactions proceeds much slower and takes one day or more to achieve a random copolymer of norbornene and cyclooctene. Its rate is limited by the interaction of polyoctenamer-bound carbenes with polynorbornene units, which is hampered, presumably due to steric reasons. Polynorbornene-bound carbenes are detected in very low concentrations throughout the whole process thus indicating their higher reactivity, as compared with the polyoctenamer-bound ones. Macroscopic homogeneity of the reacting media is proved by dynamic light scattering from solutions containing the polymer mixture and its components. In general, the studied process can be considered as a new way to unsaturated multiblock statistical copolymers. Their structure can be controlled by the amount of catalyst, mixture composition, and reaction time. It is remarkable that this goal can be achieved with a catalyst that is not suitable for ring-opening metathesis copolymerization of norbornene and cis-cyclooctene because of their substantially different monomer reactivities. PMID:26664599

  14. Olefin cross-metathesis as a source of polysaccharide derivatives: cellulose ω-carboxyalkanoates.

    PubMed

    Meng, Xiangtao; Matson, John B; Edgar, Kevin J

    2014-01-13

    Cross-metathesis has been shown for the first time to be a useful method for the synthesis of polysaccharide derivatives, focusing herein on preparation of cellulose ω-carboxyalkanoates. Commercially available cellulose esters were first acylated with 10-undecenoyl chloride, providing esters with olefin-terminated side chains. Subsequent cross-metathesis of these terminal olefin moieties with acrylic acid was performed in solvents including acrylic acid, THF, and CH2Cl2. Complete conversion to discrete, soluble cross-metathesis products was achieved by using the Hoveyda-Grubbs second generation ruthenium catalyst and an excess of acrylic acid. Oligomerization during storage, caused by a free radical mechanism, was observed and successfully suppressed by the addition of a free radical scavenger (BHT). Furthermore, the cross-metathesis products exhibited glass transition temperatures (Tg) that were at least 50 °C higher than ambient temperature, supporting the potential for application of these polymers as amorphous solid dispersion matrices for enhancing drug aqueous solubility. PMID:24328072

  15. Iron- and Cobalt-Catalyzed Alkene Hydrogenation: Catalysis with Both Redox-Active and Strong Field Ligands.

    PubMed

    Chirik, Paul J

    2015-06-16

    The hydrogenation of alkenes is one of the most impactful reactions catalyzed by homogeneous transition metal complexes finding application in the pharmaceutical, agrochemical, and commodity chemical industries. For decades, catalyst technology has relied on precious metal catalysts supported by strong field ligands to enable highly predictable two-electron redox chemistry that constitutes key bond breaking and forming steps during turnover. Alternative catalysts based on earth abundant transition metals such as iron and cobalt not only offer potential environmental and economic advantages but also provide an opportunity to explore catalysis in a new chemical space. The kinetically and thermodynamically accessible oxidation and spin states may enable new mechanistic pathways, unique substrate scope, or altogether new reactivity. This Account describes my group's efforts over the past decade to develop iron and cobalt catalysts for alkene hydrogenation. Particular emphasis is devoted to the interplay of the electronic structure of the base metal compounds and their catalytic performance. First generation, aryl-substituted pyridine(diimine) iron dinitrogen catalysts exhibited high turnover frequencies at low catalyst loadings and hydrogen pressures for the hydrogenation of unactivated terminal and disubstituted alkenes. Exploration of structure-reactivity relationships established smaller aryl substituents and more electron donating ligands resulted in improved performance. Second generation iron and cobalt catalysts where the imine donors were replaced by N-heterocyclic carbenes resulted in dramatically improved activity and enabled hydrogenation of more challenging unactivated, tri- and tetrasubstituted alkenes. Optimized cobalt catalysts have been discovered that are among the most active homogeneous hydrogenation catalysts known. Synthesis of enantiopure, C1 symmetric pyridine(diimine) cobalt complexes have enabled rare examples of highly enantioselective

  16. Operationally simple hydrotrifluoromethylation of alkenes with sodium triflinate enabled by Ir photoredox catalysis.

    PubMed

    Zhu, Lei; Wang, Lian-Sheng; Li, Bojie; Fu, Boqiao; Zhang, Cheng-Pan; Li, Wei

    2016-05-11

    We report herein a single component Ir photoredox catalyst which is capable of catalyzing the hydrotrifluoromethylation of terminal alkenes and Michael acceptors with sodium triflinate (Langlois reagent) in methanol under irradiation at room temperature. Various synthetically useful functional groups, including ester, amide, ether, aldehyde, sulfone, ketone and aryl boronate, are well tolerated in this reaction. PMID:26996326

  17. Recent applications of ring-rearrangement metathesis in organic synthesis.

    PubMed

    Kotha, Sambasivarao; Meshram, Milind; Khedkar, Priti; Banerjee, Shaibal; Deodhar, Deepak

    2015-01-01

    Ring-rearrangement metathesis (RRM) involves multiple metathesis processes such as ring-opening metathesis (ROM)/ring-closing metathesis (RCM) in a one-pot operation to generate complex targets. RRM delivers complex frameworks that are difficult to assemble by conventional methods. The noteworthy point about this type of protocol is multi-bond formation and it is an atom economic process. In this review, we have covered literature that appeared during the last seven years (2008-2014). PMID:26664603

  18. Recent applications of ring-rearrangement metathesis in organic synthesis

    PubMed Central

    Meshram, Milind; Khedkar, Priti; Banerjee, Shaibal; Deodhar, Deepak

    2015-01-01

    Summary Ring-rearrangement metathesis (RRM) involves multiple metathesis processes such as ring-opening metathesis (ROM)/ring-closing metathesis (RCM) in a one-pot operation to generate complex targets. RRM delivers complex frameworks that are difficult to assemble by conventional methods. The noteworthy point about this type of protocol is multi-bond formation and it is an atom economic process. In this review, we have covered literature that appeared during the last seven years (2008–2014). PMID:26664603

  19. 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.

  20. Metal-free ring-opening metathesis polymerization.

    PubMed

    Ogawa, Kelli A; Goetz, Adam E; Boydston, Andrew J

    2015-02-01

    We have developed a method to achieve ring-opening metathesis polymerization (ROMP) mediated by oxidation of organic initiators in the absence of any transition metals. Radical cations, generated via one-electron oxidation of vinyl ethers, were found to react with norbornene to give polymeric species with microstructures essentially identical to those traditionally obtained via metal-mediated ROMP. We found that vinyl ether oxidation could be accomplished under mild conditions using an organic photoredox mediator. This led to high yields of polymer and generally good correlation between M(n) values and initial monomer to catalyst loadings. Moreover, temporal control over reinitiation of polymer growth was achieved during on/off cycles of light exposure. This method demonstrates the first metal-free method for controlled ROMP. PMID:25573294

  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. Solid-supported cross-metathesis and a formal alkane metathesis for the generation of biologically relevant molecules.

    PubMed

    Méndez, Luciana; Mata, Ernesto G

    2015-02-01

    Solid-phase synthetic strategies toward the generation of libraries of biologically relevant molecules were developed using olefin cross-metathesis as a key step. It is remarkably the formal alkane metathesis based on a one-pot, microwave-assisted, ruthenium-catalyzed cross-metathesis and reduction to obtain Csp3-Csp3 linkages. PMID:25569690

  4. Asymmetric Palladium-Catalyzed Alkene Carboamination Reactions for the Synthesis of Cyclic Sulfamides.

    PubMed

    Garlets, Zachary J; Parenti, Kaia R; Wolfe, John P

    2016-04-18

    The synthesis of cyclic sulfamides by enantioselective Pd-catalyzed alkene carboamination reactions between N-allylsulfamides and aryl or alkenyl bromides is described. High levels of asymmetric induction (up to 95:5 e.r.) are achieved using a catalyst composed of [Pd2 (dba)3 ] and (S)-Siphos-PE. Deuterium-labelling studies indicate the reactions proceed through syn-aminopalladation of the alkene and suggest that the control of syn- versus anti-aminopalladation pathways is important for asymmetric induction. PMID:26968748

  5. 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

  6. 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

  7. Cross-metathesis of biosourced fatty acid derivatives: a step further toward improved reactivity.

    PubMed

    Vignon, Paul; Vancompernolle, Tom; Couturier, Jean-Luc; Dubois, Jean-Luc; Mortreux, André; Gauvin, Régis M

    2015-04-13

    The improved catalytic conversion of bioresources, namely unsaturated fatty acid derivatives, is presented. The targeted reaction is ruthenium-catalyzed cross-metathesis with functionalized olefins (α,β-unsaturated esters), that affords shorter diesters. These can be used as biosourced (pre)monomers for the production of polyesters. It is demonstrated that switch from terminal to internal cross-metathesis partners (that is, from methyl acrylate to methyl crotonate) allows use of ppm-level catalyst loadings, while retaining high productivity and selectivity. This was exemplified on a commercial biosourced fatty acid methyl esters mixture, using minimal purification of the substrate, on a 50 g scale. We propose that this improved catalytic behavior is due to the sole presence of more stable alkylidene intermediates, as the notoriously unstable ruthenium methylidene species are not formed using an internal functionalized olefin. PMID:25469823

  8. 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

  9. Thioamination of Alkenes with Hypervalent Iodine Reagents

    PubMed Central

    Mizar, Pushpak; Niebuhr, Rebecca; Hutchings, Matthew; Farooq, Umar; Wirth, Thomas

    2016-01-01

    An efficient thioamination of alkenes mediated by iodine(III) reagents is described. The use of different sulfur nucleophiles allows the flexible synthesis of 1,2-aminothiols from alkenes. By employing chiral iodine(III) reagents, a stereoselective version of the thioamination protocol has also been developed. PMID:26660291

  10. High-value alcohols and higher-oxidation-state compounds by catalytic Z-selective cross-metathesis

    NASA Astrophysics Data System (ADS)

    Koh, Ming Joo; Khan, R. Kashif M.; Torker, Sebastian; Yu, Miao; Mikus, Malte S.; Hoveyda, Amir H.

    2015-01-01

    Olefin metathesis catalysts provide access to molecules that are indispensable to physicians and researchers in the life sciences. A persisting problem, however, is the dearth of chemical transformations that directly generate acyclic Z allylic alcohols, including products that contain a hindered neighbouring substituent or reactive functional units such as a phenol, an aldehyde, or a carboxylic acid. Here we present an electronically modified ruthenium-disulfide catalyst that is effective in generating such high-value compounds by cross-metathesis. The ruthenium complex is prepared from a commercially available precursor and an easily generated air-stable zinc catechothiolate. Transformations typically proceed with 5.0 mole per cent of the complex and an inexpensive reaction partner in 4-8 hours under ambient conditions; products are obtained in up to 80 per cent yield and 98:2 Z:E diastereoselectivity. The use of this catalyst is demonstrated in the synthesis of the naturally occurring anti-tumour agent neopeltolide and in a single-step stereoselective gram-scale conversion of a renewable feedstock (oleic acid) to an anti-fungal agent. In this conversion, the new catalyst promotes cross-metathesis more efficiently than the commonly used dichloro-ruthenium complexes, indicating that its utility may extend beyond Z-selective processes.

  11. Magnetic Carbon Supported Palladium Nanoparticles: An Efficient and Sustainable Catalyst for Hydrogenation Reactions

    EPA Science Inventory

    Magnetic carbon supported Pd catalyst has been synthesized via in situ generation of nanoferrites and incorporation of carbon from renewable cellulose via calcination; the catalyst can be used for the hydrogenation of alkenes and reduction of aryl nitro compounds.

  12. Improving Grubbs' II type ruthenium catalysts by appropriately modifying the N-heterocyclic carbene ligand.

    PubMed

    Vieille-Petit, Ludovic; Luan, Xinjun; Gatti, Michele; Blumentritt, Sascha; Linden, Anthony; Clavier, Hervé; Nolan, Steven P; Dorta, Reto

    2009-07-01

    The introduction of N-heterocyclic carbene ligands that incorporate correctly substituted naphthyl side chains leads to increased activity and stability in second generation ruthenium metathesis catalysts. PMID:19557281

  13. 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

  14. Cyclic alkyl amino carbene (CAAC) ruthenium complexes as remarkably active catalysts for ethenolysis.

    PubMed

    Marx, Vanessa M; Sullivan, Alexandra H; Melaimi, Mohand; Virgil, Scott C; Keitz, Benjamin K; Weinberger, David S; Bertrand, Guy; Grubbs, Robert H

    2015-02-01

    An expanded family of ruthenium-based metathesis catalysts bearing cyclic alkyl amino carbene (CAAC) ligands was prepared. These catalysts exhibited exceptional activity in the ethenolysis of the seed-oil derivative methyl oleate. In many cases, catalyst turnover numbers (TONs) of more than 100,000 were achieved, at a catalyst loading of only 3 ppm. Remarkably, the most active catalyst system was able to achieve a TON of 340,000, at a catalyst loading of only 1 ppm. This is the first time a series of metathesis catalysts has exhibited such high performance in cross-metathesis reactions employing ethylene gas, with activities sufficient to render ethenolysis applicable to the industrial-scale production of linear α-olefins (LAOs) and other terminal-olefin products. PMID:25522160

  15. 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

  16. Defined Palladium-Phthalimidato Catalysts for Improved Oxidative Amination.

    PubMed

    Martínez, Claudio; Muñiz, Kilian

    2016-05-23

    New palladium(II)-phthalimidato complexes have been synthesized, isolated, and structurally characterized. As demonstrated from over 30 examples, they constitute superior catalysts for oxidative amination reactions of alkenes with phthalimide as the nitrogen source. This work streamlines vicinal difunctionalization of alkenes and provides access to significantly improved and experimentally simplified synthetic protocols. PMID:26990013

  17. 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

  18. 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.

  19. Neutral and Cationic Molybdenum Imido Alkylidene N-Heterocyclic Carbene Complexes: Reactivity in Selected Olefin Metathesis Reactions and Immobilization on Silica.

    PubMed

    Sen, Suman; Schowner, Roman; Imbrich, Dominik A; Frey, Wolfgang; Hunger, Michael; Buchmeiser, Michael R

    2015-09-21

    The synthesis and single-crystal X-ray structures of the novel molybdenum imido alkylidene N-heterocyclic carbene complexes [Mo(N-2,6-Me2C6H3)(IMesH2)(CHCMe2Ph)(OTf)2] (3), [Mo(N-2,6-Me2C6H3)(IMes)(CHCMe2Ph)(OTf)2] (4), [Mo(N-2,6-Me2C6H3)(IMesH2)(CHCMe2Ph)(OTf){OCH(CF3)2}] (5), [Mo(N-2,6-Me2C6H3)(CH3CN)(IMesH2)(CHCMe2Ph)(OTf)](+)BArF(-) (6), [Mo(N-2,6-Cl2C6H3)(IMesH2)(CHCMe3)(OTf)2] (7) and [Mo(N-2,6-Cl2C6H3)(IMes)(CHCMe3)(OTf)2] (8) are reported (IMesH2=1,3-dimesitylimidazolidin-2-ylidene, IMes=1,3-dimesitylimidazolin-2-ylidene, BArF(-)=tetrakis-[3,5-bis(trifluoromethyl)phenyl] borate, OTf=CF3SO3(-)). Also, silica-immobilized versions I1 and I2 were prepared. Catalysts 3-8, I1 and I2 were used in homo-, cross-, and ring-closing metathesis (RCM) reactions and in the cyclopolymerization of α,ω-diynes. In the RCM of α,ω-dienes, in the homometathesis of 1-alkenes, and in the ethenolysis of cyclooctene, turnover numbers (TONs) up to 100,000, 210,000 and 30,000, respectively, were achieved. With I1 and I2, virtually Mo-free products were obtained (<3 ppm Mo). With 1,6-hepta- and 1,7-octadiynes, catalysts 3, 4, and 5 allowed for the regioselective cyclopolymerization of 4,4-bis(ethoxycarbonyl)-1,6-heptadiyne, 4,4-bis(hydroxymethyl)-1,6-heptadiyne, 4,4-bis[(3,5-diethoxybenzoyloxy)methyl]-1,6-heptadiyne, 4,4,5,5-tetrakis(ethoxycarbonyl)-1,7-octadiyne, and 1,6-heptadiyne-4-carboxylic acid, underlining the high functional-group tolerance of these novel Group 6 metal alkylidenes. PMID:26249141

  20. Olefin cross-metathesis as a tool in natural product degradation. The stereochemistry of (+)-falcarindiol.

    PubMed

    Ratnayake, Anokha S; Hemscheidt, Thomas

    2002-12-26

    [reaction: see text] There are conflicting reports in the literature concerning the absolute sterochemistry at C-3 of the common plant polyacetylene oxylipin (+)-falcarindiol. We have employed olefin cross-metathesis using Grubbs' second generation catalyst and ethylene gas to degrade falcarindiol to the symmetrical 1,9-decadiene-4,6-diyne-3,8-diol. The reaction is completely selective for net removal of the aliphatic side chain. Degradation of (+)-falcarindiol from Tetraplasandra hawaiiensis yields a meso product as shown by chiral HPLC. Hence, (+)-falcarindiol from this source has a (3R,8S)-configuration. PMID:12489956

  1. Functional Materials from Nanostructured Block Polymers Prepared via Ring-opening Metathesis Polymerization

    NASA Astrophysics Data System (ADS)

    Pitet, Louis Marcel

    The structural and molecular versatility afforded to polymeric materials by ruthenium catalysts during ring-opening metathesis polymerization (ROMP) cannot be exaggerated. This dissertation describes the synthesis of functionalized polyolefins via ROMP with particular emphasis on designing straightforward approaches to materials in which the molecular structure is meticulously controlled. Moreover, large portions of the body are dedicated to describing functionalized polyolefins as precursors to more complex multicomponent block copolymers. Block copolymers having various components derived from mechanistically incompatible feedstocks were designed with translational targets in mind, including toughening agents for brittle plastics, and free-standing nanoporous membranes. Several fundamental structure-property relationships were also explored for the newly synthesized materials.

  2. Catalytic, Enantioselective Addition of Alkyl Radicals to Alkenes via Visible-Light-Activated Photoredox Catalysis with a Chiral Rhodium Complex.

    PubMed

    Huo, Haohua; Harms, Klaus; Meggers, Eric

    2016-06-01

    An efficient enantioselective addition of alkyl radicals, oxidatively generated from organotrifluoroborates, to acceptor-substituted alkenes is catalyzed by a bis-cyclometalated rhodium catalyst (4 mol %) under photoredox conditions. The practical method provides yields up to 97% with excellent enantioselectivities up to 99% ee and can be classified as a redox neutral, electron-transfer-catalyzed reaction. PMID:27218134

  3. 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

  4. Toluene Monooxygenase-Catalyzed Epoxidation of Alkenes

    PubMed Central

    McClay, Kevin; Fox, Brian G.; Steffan, Robert J.

    2000-01-01

    Several toluene monooxygenase-producing organisms were tested for their ability to oxidize linear alkenes and chloroalkenes three to eight carbons long. Each of the wild-type organisms degraded all of the alkenes that were tested. Epoxides were produced during the oxidation of butene, butadiene, and pentene but not hexene or octadiene. A strain of Escherichia coli expressing the cloned toluene-4-monooxygenase (T4MO) of Pseudomonas mendocina KR1 was able to oxidize butene, butadiene, pentene, and hexene but not octadiene, producing epoxides from all of the substrates that were oxidized. A T4MO-deficient variant of P. mendocina KR1 oxidized alkenes that were five to eight carbons long, but no epoxides were detected, suggesting the presence of multiple alkene-degrading enzymes in this organism. The alkene oxidation rates varied widely (ranging from 0.01 to 0.33 μmol of substrate/min/mg of cell protein) and were specific for each organism-substrate pair. The enantiomeric purity of the epoxide products also varied widely, ranging from 54 to >90% of a single epoxide enantiomer. In the absence of more preferred substrates, such as toluene or alkenes, the epoxides underwent further toluene monooxygenase-catalyzed transformations, forming products that were not identified. PMID:10788354

  5. Development of an Enyne Metathesis/Isomerization/Diels-Alder One-Pot Reaction for the Synthesis of a Novel Near-Infrared (NIR) Dye Core.

    PubMed

    Yamashita, Kohei; Fujii, Yuki; Yoshioka, Shohei; Aoyama, Hiroshi; Tsujino, Hirofumi; Uno, Tadayuki; Fujioka, Hiromichi; Arisawa, Mitsuhiro

    2015-11-23

    N-Alkyl-N-allyl-2-alkynylaniline derivatives undergo a tandem ring-closing enyne metathesis/isomerization/Diels-Alder cycloaddition sequence in the presence of a second-generation Grubbs catalyst and dienophiles. In practice, the acyclic enyne in the presence of the ruthenium alkylidene first undergoes ring-closing metathesis to generate cyclic 4-vinyl-1,2-dihydroquinolines; following diene isomerization and then the addition of a dienophile, these ring-closing metathesis products are selectively converted into a 7-methyl-4H-naphtho[3,2,1-de]quinoline-8,11-dione core. Overall, the reaction sequence converts simple aniline derivatives into π-conjugated small molecules, which have characteristic absorption in the near-infrared region, in a single operation through three unique ruthenium-catalyzed transformations. PMID:26449517

  6. Kinetically Trapped Tetrahedral Cages via Alkyne Metathesis.

    PubMed

    Lee, Semin; Yang, Anna; Moneypenny, Timothy P; Moore, Jeffrey S

    2016-02-24

    In dynamic covalent synthesis, kinetic traps are perceived as disadvantageous, hindering the system from reaching its thermodynamic equilibrium. Here we present the near-quantitative preparation of tetrahedral cages from simple tritopic precursors using alkyne metathesis. While the cages are the presumed thermodynamic sink, we experimentally demonstrate that the products no longer exchange their vertices once they have formed. The example reported here illustrates that kinetically trapped products may facilitate high yields of complex products from dynamic covalent synthesis. PMID:26854552

  7. 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

  8. 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).

  9. Ruthenium-catalysed alkoxycarbonylation of alkenes with carbon dioxide.

    PubMed

    Wu, Lipeng; Liu, Qiang; Fleischer, Ivana; Jackstell, Ralf; Beller, Matthias

    2014-01-01

    Alkene carbonylations represent a major technology for the production of value-added bulk and fine chemicals. Nowadays, all industrial carbonylation processes make use of highly toxic and flammable carbon monoxide. Here we show the application of abundantly available carbon dioxide as C1 building block for the alkoxycarbonylations of industrially important olefins in the presence of a convenient and inexpensive ruthenium catalyst system. In our system, carbon dioxide works much better than the traditional combination of carbon monoxide and alcohols. The unprecedented in situ formation of carbon monoxide from carbon dioxide and alcohols permits an efficient synthesis of carboxylic acid esters, which can be used as detergents and polymer-building blocks. Notably, this transformation allows the catalytic formation of C-C bonds with carbon dioxide as C1 source and avoids the use of sensitive and/or expensive reducing agents (for example, Grignard reagents, diethylzinc or triethylaluminum). PMID:24518431

  10. Generation of stoichiometric ethylene and isotopic derivatives and application in transition-metal-catalyzed vinylation and enyne metathesis.

    PubMed

    Min, Geanna K; Bjerglund, Klaus; Kramer, Søren; Gøgsig, Thomas M; Lindhardt, Anders T; Skrydstrup, Troels

    2013-12-16

    Ethylene is one of the most important building blocks in industry for the production of polymers and commodity chemicals. (13)C- and D-isotope-labeled ethylenes are also valuable reagents with applications ranging from polymer-structure determination, reaction-mechanism elucidation to the preparation of more complex isotopically labeled compounds. However, these isotopic derivatives are expensive, and are flammable gases, which are difficult to handle. We have developed a method for the controlled generation of ethylene and its isotopic variants including, for the first time, fully isotopically labeled ethylene, from simple alkene precursors by using Ru catalysis. Applying a two-chamber reactor allows both the synthesis of ethylene and its immediate consumption in a chemical transformation permitting reactions to be performed with only stoichiometric amounts of this two carbon olefin. This was demonstrated in the Ni-catalyzed Heck reaction with aryl triflates and benzyl chlorides, as well as Ru-mediated enyne metathesis. PMID:24243666

  11. Synthesis of β-Hydroxysulfones from Sulfonyl Chlorides and Alkenes Utilizing Visible Light Photocatalytic Sequences.

    PubMed

    Pagire, Santosh K; Paria, Suva; Reiser, Oliver

    2016-05-01

    The synthesis of β-hydroxysulfones from sulfonyl chlorides and styrenes in the presence of water by a visible light mediated atom transfer radical addition (ATRA)-like process utilizing fac[Ir(ppy)3] as photoredox catalyst was developed in high yields. This process could be combined with the visible light mediated synthesis of trifluoromethylated sulfonyl chlorides via an ATRA reaction between alkenes and CF3SO2Cl utilizing [Cu(dap)2Cl] as photoredox catalyst, demonstrating the possibility of sequential photoredox processes. PMID:27101416

  12. A combination of directing groups and chiral anion phase-transfer catalysis for enantioselective fluorination of alkenes

    PubMed Central

    Wu, Jeffrey; Wang, Yi-Ming; Drljevic, Amela; Rauniyar, Vivek; Phipps, Robert J.; Toste, F. Dean

    2013-01-01

    We report a catalytic enantioselective electrophilic fluorination of alkenes to form tertiary and quaternary C(sp3)-F bonds and generate β-amino- and β-aryl-allylic fluorides. The reaction takes advantage of the ability of chiral phosphate anions to serve as solid–liquid phase transfer catalysts and hydrogen bond with directing groups on the substrate. A variety of heterocyclic, carbocyclic, and acyclic alkenes react with good to excellent yields and high enantioselectivities. Further, we demonstrate a one-pot, tandem dihalogenation–cyclization reaction, using the same catalytic system twice in series, with an analogous electrophilic brominating reagent in the second step. PMID:23922394

  13. Synthesis of amide-functionalized cellulose esters by olefin cross-metathesis.

    PubMed

    Meng, Xiangtao; Edgar, Kevin J

    2015-11-01

    Cellulose esters with amide functionalities were synthesized by cross-metathesis (CM) reaction of terminally olefinic esters with different acrylamides, catalyzed by Hoveyda-Grubbs 2nd generation catalyst. Chelation by amides of the catalyst ruthenium center caused low conversions using conventional solvents. The effects of both solvent and structure of acrylamide on reaction conversion were investigated. While the inherent tendency of acrylamides to chelate Ru is governed by the acrylamide N-substituents, employing acetic acid as a solvent significantly improved the conversion of certain acrylamides, from 50% to up to 99%. Homogeneous hydrogenation using p-toluenesulfonyl hydrazide successfully eliminated the α,β-unsaturation of the CM products to give stable amide-functionalized cellulose esters. The amide-functionalized product showed higher Tg than its starting terminally olefinic counterpart, which may have resulted from strong hydrogen bonding interactions of the amide functional groups. PMID:26256383

  14. Metathesis of Fatty Acid Ester Derivatives in 1,1-Dialkyl and 1,2,3-Trialkyl Imidazolium Type Ionic Liquids

    PubMed Central

    Thomas, Priya A.; Marvey, Bassie B.; Ebenso, Eno E.

    2011-01-01

    The self-metathesis of methyl oleate and methyl ricinoleate was carried out in the presence of ruthenium alkylidene catalysts 1–4 in [bmim] and [bdmim][X] type ionic liquids (RTILs) (X = PF6−, BF4− and NTf2−) using the gas chromatographic technique. Best catalytic performance was obtained in [bdmim][X] type ionic liquids when compared with [bmim][X] type ionic liquids. Catalyst recycling studies were also carried out in the room temperature ionic liquids (RTILs) with catalysts 1–4 in order to explore their possible industrial application. PMID:21747719

  15. Nickel-Catalyzed Regioselective Cleavage of Csp(2)-S Bonds: Method for the Synthesis of Tri- and Tetrasubstituted Alkenes.

    PubMed

    Chen, Jinyang; Chen, Sihai; Xu, Xinhua; Tang, Zhi; Au, Chak-Tong; Qiu, Renhua

    2016-04-15

    We describe here an efficient route for the synthesis of (Z)-vinylic sulfides 3 via the highly regio- and stereoselective coupling of (Z)-1,2-bis(aryl(alkyl)thio)alkenes and Grignard reagents over a Ni catalyst under mild conditions. (Z)-Vinylic sulfides 3 are important intermediates in the synthesis of tri- and tetrasubstituted alkenes that are important construction blocks for drugs and natural products. The directing organosulfur groups (SR) can be converted to diaryl(alkyl) disulfides (RSSR) using H2O2 as oxidant, hence avoiding the waste of sulfur resources. The protocol provides a general method that is highly regio- and stereoselective for the synthesis of a diversity of tri- and tetrasubstituted alkenes. PMID:26999304

  16. 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...

  17. 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...

  18. Latent ruthenium–indenylidene catalysts bearing a N-heterocyclic carbene and a bidentate picolinate ligand

    PubMed Central

    Schmid, Thibault E; Modicom, Florian; Dumas, Adrien; Borré, Etienne; Toupet, Loic

    2015-01-01

    Summary A silver-free methodology was developed for the synthesis of unprecedented N-heterocyclic carbene ruthenium indenylidene complexes bearing a bidentate picolinate ligand. The highly stable (SIPr)(picolinate)RuCl(indenylidene) complex 4a (SIPr = 1,3-bis(2-6-diisopropylphenyl)imidazolidin-2-ylidene) demonstrated excellent latent behaviour in ring closing metathesis (RCM) reaction and could be activated in the presence of a Brønsted acid. The versatility of the catalyst 4a was subsequently demonstrated in RCM, cross-metathesis (CM) and enyne metathesis reactions. PMID:26425213

  19. 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.

  20. 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

  1. 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.

  2. Thermoset polymers via ring opening metathesis polymerization of functionalized oils

    DOEpatents

    Larock, Richard C; Henna, Phillip H; Kessier, Michael R

    2012-11-27

    The invention provides a method for producing a thermosetting resin from renewable oils, the method comprising supplying renewable oil molecules containing strained ring alkene moieties; reacting the alkene moieties with cyclic alkenes to create a polymer; and repeating the above two steps until the resin having desired characteristics are obtained. Also provided is a thermoset resin comprising functionalized renewable oil polymerized with a co-monomer.

  3. Interplay of olefin metathesis and multiple hydrogen bonding interactions: covalently cross-linked zippers.

    PubMed

    Zeng, Jisen; Wang, Wei; Deng, Pengchi; Feng, Wen; Zhou, Jingjing; Yang, Yuanyou; Yuan, Lihua; Yamato, Kazuhiro; Gong, Bing

    2011-08-01

    Hydrogen-bonded zippers bearing terminal alkene groups were treated with Grubbs' catalyst, leading to covalently cross-linked zippers without violating H-bonding sequence specificity. The yield of a cross-linked zipper depended on the stability of its H-bonded precursor, with a weakly associating pair giving reasonable yields only at high concentrations while strongly associating pairs showed nearly quantitative yields. The integration of thermodynamic (H-bonding) and kinetic (irreversible C═C bond formation) processes suggests the possibility of developing many different covalent association units for constructing molecular structures based on a self-assembling way. PMID:21699249

  4. An alkyne metathesis-based route toortho-dehydrobenzannulenes

    SciTech Connect

    Miljanic, Ognjen S.; Vollhardt, Peter C.; Whitener, Glenn D.

    2002-11-07

    An application of alkyne metathesis to 1,2-di(prop-1-ynyl)arenes, producing dehydrobenzannulenes, is described. An efficient method for selective Sonogashira couplings of bromoiodoarenes under conditions of microwave irradiation is also reported.

  5. Organic chemistry: No double bond left behind

    NASA Astrophysics Data System (ADS)

    Sarlah, David

    2016-03-01

    Alkenyl halides are some of the most useful building blocks for synthesizing small organic molecules. A catalyst has now allowed their direct preparation from widely available alkenes using the cross-metathesis reaction. See Article p.459

  6. Direct synthesis of Z-alkenyl halides through catalytic cross-metathesis

    NASA Astrophysics Data System (ADS)

    Koh, Ming Joo; Nguyen, Thach T.; Zhang, Hanmo; Schrock, Richard R.; Hoveyda, Amir H.

    2016-03-01

    Olefin metathesis has had a large impact on modern organic chemistry, but important shortcomings remain: for example, the lack of efficient processes that can be used to generate acyclic alkenyl halides. Halo-substituted ruthenium carbene complexes decompose rapidly or deliver low activity and/or minimal stereoselectivity, and our understanding of the corresponding high-oxidation-state systems is limited. Here we show that previously unknown halo-substituted molybdenum alkylidene species are exceptionally reactive and are able to participate in high-yielding olefin metathesis reactions that afford acyclic 1,2-disubstituted Z-alkenyl halides. Transformations are promoted by small amounts of a catalyst that is generated in situ and used with unpurified, commercially available and easy-to-handle liquid 1,2-dihaloethene reagents, and proceed to high conversion at ambient temperature within four hours. We obtain many alkenyl chlorides, bromides and fluorides in up to 91 per cent yield and complete Z selectivity. This method can be used to synthesize biologically active compounds readily and to perform site- and stereoselective fluorination of complex organic molecules.

  7. Direct synthesis of Z-alkenyl halides through catalytic cross-metathesis.

    PubMed

    Koh, Ming Joo; Nguyen, Thach T; Zhang, Hanmo; Schrock, Richard R; Hoveyda, Amir H

    2016-03-24

    Olefin metathesis has had a large impact on modern organic chemistry, but important shortcomings remain: for example, the lack of efficient processes that can be used to generate acyclic alkenyl halides. Halo-substituted ruthenium carbene complexes decompose rapidly or deliver low activity and/or minimal stereoselectivity, and our understanding of the corresponding high-oxidation-state systems is limited. Here we show that previously unknown halo-substituted molybdenum alkylidene species are exceptionally reactive and are able to participate in high-yielding olefin metathesis reactions that afford acyclic 1,2-disubstituted Z-alkenyl halides. Transformations are promoted by small amounts of a catalyst that is generated in situ and used with unpurified, commercially available and easy-to-handle liquid 1,2-dihaloethene reagents, and proceed to high conversion at ambient temperature within four hours. We obtain many alkenyl chlorides, bromides and fluorides in up to 91 per cent yield and complete Z selectivity. This method can be used to synthesize biologically active compounds readily and to perform site- and stereoselective fluorination of complex organic molecules. PMID:27008965

  8. 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.

  9. 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

  10. Rhodium-Catalyzed Alkene Difunctionalization with Nitrenes.

    PubMed

    Ciesielski, Jennifer; Dequirez, Geoffroy; Retailleau, Pascal; Gandon, Vincent; Dauban, Philippe

    2016-06-27

    The Rh(II) -catalyzed oxyamination and diamination of alkenes generate 1,2-amino alcohols and 1,2-diamines, respectively, in good to excellent yields and with complete regiocontrol. In the case of diamination, the intramolecular reaction provides an efficient method for the preparation of pyrrolidines, and the intermolecular reaction produces vicinal amines with orthogonal protecting groups. These alkene difunctionalizations proceed by aziridination followed by nucleophilic ring opening induced by an Rh-bound nitrene generated in situ, details of which were uncovered by both experimental and theoretical studies. In particular, DFT calculations show that the nitrogen atom of the putative [Rh]2 =NR metallanitrene intermediate is electrophilic and support an aziridine activation pathway by N⋅⋅⋅N=[Rh]2 bond formation, in addition to the N⋅⋅⋅[Rh]2 =NR coordination mode. PMID:27258005

  11. NMP and O2 as Radical Initiator: Trifluoromethylation of Alkenes to Tertiary β-Trifluoromethyl Alcohols at Room Temperature.

    PubMed

    Liu, Chao; Lu, Qingquan; Huang, Zhiyuan; Zhang, Jian; Liao, Fan; Peng, Pan; Lei, Aiwen

    2015-12-18

    A novel strategy was developed to trigger ·CF3 by using in situ generated peroxide in NMP under O2 or air as the radical initiator. Radical trifluoromethylation of alkenes was achieved toward tertiary β-trifluoromethyl alcohols. Various tertiary β-trifluoromethyl alcohols can be synthesized in good yields without extra oxidants or transition metal catalysts. Preliminary mechanistic investigation revealed that O2 diffusion can influence the reaction rate. PMID:26649920

  12. Catalytic Aminohalogenation of Alkenes and Alkynes

    PubMed Central

    Chemler, Sherry R.; Bovino, Michael T.

    2013-01-01

    Catalytic aminohalogenation methods enable the regio- and stereoselective vicinal difunctionalization of alkynes, allenes and alkenes with amine and halogen moieties. A range of protocols and reaction mechanisms including organometallic, Lewis base, Lewis acid and Brønsted acid catalysis have been disclosed, enabling the regio- and stereoselective synthesis of halogen-functionalized acyclic amines and nitrogen heterocycles. Recent advances including aminofluorination and catalytic enantioselective aminohalogenation reactions are summarized in this review. PMID:23828735

  13. Anaerobic 1-Alkene Metabolism by the Alkane- and Alkene-Degrading Sulfate Reducer Desulfatibacillum aliphaticivorans Strain CV2803T▿

    PubMed Central

    Grossi, Vincent; Cravo-Laureau, Cristiana; Méou, Alain; Raphel, Danielle; Garzino, Frédéric; Hirschler-Réa, Agnès

    2007-01-01

    The alkane- and alkene-degrading, marine sulfate-reducing bacterium Desulfatibacillum aliphaticivorans strain CV2803T, known to oxidize n-alkanes anaerobically by fumarate addition at C-2, was investigated for its 1-alkene metabolism. The total cellular fatty acids of this strain were predominantly C-(even number) (C-even) when it was grown on C-even 1-alkenes and predominantly C-(odd number) (C-odd) when it was grown on C-odd 1-alkenes. Detailed analyses of those fatty acids by gas chromatography-mass spectrometry after 6- to 10-week incubations allowed the identification of saturated 2- and 4-ethyl-, 2- and 4-methyl-, and monounsaturated 4-methyl-branched fatty acids with chain lengths that correlated with those of the 1-alkene. The growth of D. aliphaticivorans on (per)deuterated 1-alkenes provided direct evidence of the anaerobic transformation of these alkenes into the corresponding 1-alcohols and into linear as well as 10- and 4-methyl-branched fatty acids. Experiments performed with [13C]bicarbonate indicated that the initial activation of 1-alkene by the addition of inorganic carbon does not occur. These results demonstrate that D. aliphaticivorans metabolizes 1-alkene by the oxidation of the double bond at C-1 and by the subterminal addition of organic carbon at both ends of the molecule [C-2 and C-(ω-1)]. The detection of ethyl-branched fatty acids from unlabeled 1-alkenes further suggests that carbon addition also occurs at C-3. Alkylsuccinates were not observed as potential initial intermediates in alkene metabolism. Based on our observations, the first pathways for anaerobic 1-alkene metabolism in an anaerobic bacterium are proposed. Those pathways indicate that diverse initial reactions of 1-alkene activation can occur simultaneously in the same strain of sulfate-reducing bacterium. PMID:17965214

  14. Anaerobic 1-alkene metabolism by the alkane- and alkene-degrading sulfate reducer Desulfatibacillum aliphaticivorans strain CV2803T.

    PubMed

    Grossi, Vincent; Cravo-Laureau, Cristiana; Méou, Alain; Raphel, Danielle; Garzino, Frédéric; Hirschler-Réa, Agnès

    2007-12-01

    The alkane- and alkene-degrading, marine sulfate-reducing bacterium Desulfatibacillum aliphaticivorans strain CV2803(T), known to oxidize n-alkanes anaerobically by fumarate addition at C-2, was investigated for its 1-alkene metabolism. The total cellular fatty acids of this strain were predominantly C-(even number) (C-even) when it was grown on C-even 1-alkenes and predominantly C-(odd number) (C-odd) when it was grown on C-odd 1-alkenes. Detailed analyses of those fatty acids by gas chromatography-mass spectrometry after 6- to 10-week incubations allowed the identification of saturated 2- and 4-ethyl-, 2- and 4-methyl-, and monounsaturated 4-methyl-branched fatty acids with chain lengths that correlated with those of the 1-alkene. The growth of D. aliphaticivorans on (per)deuterated 1-alkenes provided direct evidence of the anaerobic transformation of these alkenes into the corresponding 1-alcohols and into linear as well as 10- and 4-methyl-branched fatty acids. Experiments performed with [(13)C]bicarbonate indicated that the initial activation of 1-alkene by the addition of inorganic carbon does not occur. These results demonstrate that D. aliphaticivorans metabolizes 1-alkene by the oxidation of the double bond at C-1 and by the subterminal addition of organic carbon at both ends of the molecule [C-2 and C-(omega-1)]. The detection of ethyl-branched fatty acids from unlabeled 1-alkenes further suggests that carbon addition also occurs at C-3. Alkylsuccinates were not observed as potential initial intermediates in alkene metabolism. Based on our observations, the first pathways for anaerobic 1-alkene metabolism in an anaerobic bacterium are proposed. Those pathways indicate that diverse initial reactions of 1-alkene activation can occur simultaneously in the same strain of sulfate-reducing bacterium. PMID:17965214

  15. Highly Enantioselective Iron-Catalyzed cis-Dihydroxylation of Alkenes with Hydrogen Peroxide Oxidant via an Fe(III) -OOH Reactive Intermediate.

    PubMed

    Zang, Chao; Liu, Yungen; Xu, Zhen-Jiang; Tse, Chun-Wai; Guan, Xiangguo; Wei, Jinhu; Huang, Jie-Sheng; Che, Chi-Ming

    2016-08-22

    The development of environmentally benign catalysts for highly enantioselective asymmetric cis-dihydroxylation (AD) of alkenes with broad substrate scope remains a challenge. By employing [Fe(II) (L)(OTf)2 ] (L=N,N'-dimethyl-N,N'-bis(2-methyl-8-quinolyl)-cyclohexane-1,2-diamine) as a catalyst, cis-diols in up to 99.8 % ee with 85 % isolated yield have been achieved in AD of alkenes with H2 O2 as an oxidant and alkenes in a limiting amount. This "[Fe(II) (L)(OTf)2 ]+H2 O2 " method is applicable to both (E)-alkenes and terminal alkenes (24 examples >80 % ee, up to 1 g scale). Mechanistic studies, including (18) O-labeling, UV/Vis, EPR, ESI-MS analyses, and DFT calculations lend evidence for the involvement of chiral Fe(III) -OOH active species in enantioselective formation of the two C-O bonds. PMID:27457506

  16. Metabolic alkene labeling and in vitro detection of histone acylation via the aqueous oxidative Heck reaction

    PubMed Central

    Ourailidou, Maria E.; Dockerty, Paul; Witte, Martin; Poelarends, Gerrit J.; Dekker, Frank J.

    2016-01-01

    The detection of protein lysine acylations remains a challenge due to a lack of specific antibodies for acylations with various chain lengths. This problem can be addressed by metabolic labeling techniques using carboxylates with reactive functionalities. Subsequent chemoselective reactions with a complementary moiety connected to a detection tag enable the visualization and quantification of the protein lysine acylome. In this study, we present EDTA-Pd(II) as a novel catalyst for the oxidative Heck reaction on protein-bound alkenes, which allows employment of fully aqueous reaction conditions. We used this reaction to monitor histone lysine acylation in vitro after metabolic incorporation of olefinic carboxylates as chemical reporters. PMID:25672493

  17. 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

  18. 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

  19. 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

  20. 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

  1. Tetrabutylammonium decatungstate-photosensitized alkylation of electrophilic alkenes: Convenient functionalization of aliphatic C-H bonds.

    PubMed

    Dondi, Daniele; Fagnoni, Maurizio; Albini, Angelo

    2006-05-15

    Tetrabutylammonium decatungstate (TBADT, 2 x 10(-3) m) is an effective photocatalyst for the alkylation of electrophilic alkenes (0.1 m, alpha,beta-unsaturated nitriles, esters, ketones) by alkanes, alcohols, and ethers. The products are in most cases obtained in >70 % isolated yields, through an experimentally very simple procedure. The kinetics of the radical processes following initial hydrogen abstraction by excited TBADT in deoxygenated MeCN have been studied. In the absence of a trap, back hydrogen transfer from reduced tungstate is the main pathway for alkyl radicals, while alpha-hydroxyalkyl radicals are oxidized to ketones by ground-state TBADT. With both radical types the reaction ceases at a few percent conversion. However, trapping by electrophilic alkenes is followed by reduction of the radical adduct and regeneration of the catalyst, which allows the alkylation to proceed up to complete alkene conversion with the mentioned good yields of products. With a nucleophilic (alpha-hydroxyalkyl) radical, alkylation is efficient (Phi = 0.58) and can also be carried out when degassing is omitted, the only difference being a short induction period. With a less reactive (cyclohexyl) radical, the quantum yield is lower (Phi = 0.06) and the reaction is considerably slowed in aerated solutions, but the chemical yield remains good. PMID:16521134

  2. 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

  3. Ring-opening metathesis polymerization-based recyclable magnetic acylation reagents.

    PubMed

    Kainz, Quirin M; Linhardt, Roland; Maity, Pradip K; Hanson, Paul R; Reiser, Oliver

    2013-04-01

    An operationally simple method for the acylation of amines utilizing carbon-coated metal nanoparticles as recyclable supports is reported. Highly magnetic carbon-coated cobalt (Co/C) and iron (Fe/C) nanobeads were functionalized with a norbornene tag (Nb-tag) through a "click" reaction followed by surface activation employing Grubbs-II catalyst and subsequent grafting of acylated N-hydroxysuccinimide ROMPgels (ROMP=ring-opening metathesis polymerization). The high loading (up to 2.6 mmolg(-1) ) hybrid material was applied in the acylation of various primary and secondary amines. The products were isolated in high yields (86-99%) and excellent purities (all >95 % by NMR spectroscopy) after rapid magnetic decantation and simple evaporation of the solvents. The spent resins were successfully re-acylated by acid chlorides, anhydrides, and carboxylic acids and reused for up to five consecutive cycles without considerable loss of activity. PMID:23427021

  4. An Efficient Approach to Surface-Initiated Ring-Opening Metathesis Polymerization of Cyclooctadiene

    PubMed Central

    Feng, Jianxin; Stoddart, Stephanie S.; Weerakoon, Kanchana A.; Chen, Wei

    2008-01-01

    Surface-initiated ring-opening metathesis polymerization of cyclooctadiene (COD), a low ring-strain olefin, is reported for the first time. Polymerization was carried out in the vapor phase, which is advantageous compared to conventional solution methods in terms of minimizing chain transfer by reducing polymer chain mobility at the vapor/solid interface. Attachments of a norbornenyl-containing silane and a Grubbs catalyst to silicon substrates were carried out before samples were exposed to COD vapor. The thickness of grafted 1,4-polybutadiene films was controlled by reaction time and reached ~40 nm after 7 h. The polymer films were further chemically modified to afford a new polymer, head-to-head poly(vinyl alcohol). PMID:17241005

  5. [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

  6. Two Ene-Yne Metathesis Approaches to the Total Synthesis of Amphidinolide P.

    PubMed

    Jecs, Edgars; Diver, Steven T

    2015-07-17

    The total synthesis of amphidinolide P was achieved through two different ene-yne metathesis approaches. In each approach, the metathesis step was performed at late stages in the synthesis with all other functionality present. By forging two successful pathways to the synthesis of 1, some of the strengths and weaknesses of metathesis-intensive synthetic strategies were identified. PMID:26114894

  7. Nucleophile-Assisted Alkene Activation: Olefins Alone Are Often Incompetent.

    PubMed

    Ashtekar, Kumar Dilip; Vetticatt, Mathew; Yousefi, Roozbeh; Jackson, James E; Borhan, Babak

    2016-07-01

    Emerging work on organocatalytic enantioselective halocyclizations naturally draws on conditions where both new bonds must be formed under delicate control, the reaction regime where the concerted nature of the AdE3 mechanism is of greatest importance. Without assistance, many simple alkene substrates react slowly or not at all with conventional halenium donors under synthetically relevant reaction conditions. As demonstrated earlier by Shilov, Cambie, Williams, Fahey, and others, alkenes can undergo a concerted AdE3-type reaction via nucleophile participation, which sets the configuration of the newly created stereocenters at both ends in one step. Herein, we explore the modulation of alkene reactivity and halocyclization rates by nucleophile proximity and basicity, through detailed analyses of starting material spectroscopy, addition stereopreferences, isotope effects, and nucleophile-alkene interactions, all obtained in a context directly relevant to synthesis reaction conditions. The findings build on the prior work by highlighting the reactivity spectrum of halocyclizations from stepwise to concerted, and suggest strategies for design of new reactions. Alkene reactivity is seen to span the range from the often overgeneralized "sophomore textbook" image of stepwise electrophilic attack on the alkene and subsequent nucleophilic bond formation, to the nucleophile-assisted alkene activation (NAAA) cases where electron donation from the nucleophilic addition partner activates the alkene for electrophilic attack. By highlighting the factors that control reactivity across this range, this study suggests opportunities to explain and control stereo-, regio-, and organocatalytic chemistry in this important class of alkene additions. PMID:27284808

  8. 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

  9. Asymmetric synthesis from terminal alkenes by cascades of diboration and cross-coupling

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    Terminal, monosubstituted alkenes are ideal prospective starting materials for organic synthesis because they are manufactured on very large scales and can be functionalized via a broad range of chemical transformations. Alkenes also have the attractive feature of being stable in the presence of many acids, bases, oxidants and reductants. In spite of these attributes, relatively few catalytic enantioselective transformations have been developed that transform aliphatic α-olefins into chiral products with an enantiomeric excess greater then 90 per cent. With the exception of site-controlled isotactic polymerization of α-olefins, none of these catalytic enantioselective processes results in chain-extending carbon-carbon bond formation to the terminal carbon. Here 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 number of chiral products. These reactions are facilitated by a neighbouring functional group that accelerates palladium-catalysed cross-coupling of 1,2-bis(boronates) relative to non-functionalized alkyl boronate analogues. In tandem with enantioselective diboration, this reactivity feature transforms alkene starting materials into a diverse array of chiral products. We note that the tandem diboration/cross-coupling reaction generally provides products in high yield and high selectivity (>95:5 enantiomer ratio), uses low loadings (1-2 mol per cent) of commercially available catalysts and reagents, 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.

  10. Catalysis alkene and arene hydrogenation by thermally activated silica

    SciTech Connect

    Rajagopal, V.; Guthrie, R.D.; Davis, B.H.

    1995-12-31

    Bittner, Bockrath and Solar have reported that thermal activation of fumed silica at 320{degrees}C under argon flow introduces catalytic activity for the reactions H{sub 2} + D{sub 2} {yields} 2 HD and D{sub 2} + CH{sub 2}=CH{sub 2} {yields} CH{sub 2}DCH{sub 2}D {yields} CD{sub 3}CD{sub 3}. Using the Bittner catalyst in a glass-walled, tube reactor we hydrogenate bulk samples of alkenes and arenes using D{sub 2} at pressures of 10-14 MPa and >300{degrees}C. Activation is required. Compounds hydrogenated include, stilbene, nonene, anthracene and diphenylacetylene. The aromatic rings of naphthalene, biphenyl and bibenzyl are partially hydrogenated on prolonged treatment at 350{degrees}C. At threshold temperature for the hydrogenation of diphenylacetylene, the less-stable cis-stilbene is formed faster than it proceeds to the predominantly transequilibrium mixture. Surface OH groups on the silica undergo complete equilibration to OD under our reaction conditions. However, only a barely-measurable trace of D-atom addition occurs when D{sub 2}-equilibrated silica is heated with stilbene after D{sub 2} removal.

  11. 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

  12. Mechanism and selectivity of N-triflylphosphoramide catalyzed (3(+) + 2) cycloaddition between hydrazones and alkenes.

    PubMed

    Hong, Xin; Küçük, Hatice Başpınar; Maji, Modhu Sudan; Yang, Yun-Fang; Rueping, Magnus; Houk, K N

    2014-10-01

    Brønsted acid catalyzed (3(+) + 2) cycloadditions between hydrazones and alkenes provide a general approach to pyrazolidines. The acidity of the Brønsted acid is crucial for the catalytic efficiency: the less acidic phosphoric acids are ineffective, while highly acidic chiral N-triflylphosphoramides are very efficient and can promote highly enantioselective cycloadditions. The mechanism and origins of catalytic efficiencies and selectivities of these reactions have been explored with density functional theory (M06-2X) calculations. Protonation of hydrazones by N-triflylphosphoramide produces hydrazonium-phosphoramide anion complexes. These ion-pair complexes are very reactive in (3(+) + 2) cycloadditions with alkenes, producing pyrazolidine products. Alternative 1,3-dipolar (3 + 2) cycloadditions with the analogous azomethine imines are much less favorable due to the endergonic isomerization of hydrazone to azomethine imine. With N-triflylphosphoramide catalyst, only a small distortion of the ion-pair complex is required to achieve its geometry in the (3(+) + 2) cycloaddition transition state. In contrast, the weak phosphoric acid does not protonate the hydrazone, and only a hydrogen-bonded complex is formed. Larger distortion energy is required for the hydrogen-bonded complex to achieve the "ion-pair" geometry in the cycloaddition transition state, and a significant barrier is found. On the basis of this mechanism, we have explained the origins of enantioselectivities when a chiral N-triflylphosphoramide catalyst is employed. We also report the experimental studies that extend the substrate scope of alkenes to ethyl vinyl ethers and thioethers. PMID:25226575

  13. 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

  14. Naturally Produced Defensive Alkenal Compounds Activate TRPA1.

    PubMed

    Blair, Nathaniel T; Philipson, Benjamin I; Richards, Paige M; Doerner, Julia F; Segura, Abraham; Silver, Wayne L; Clapham, David E

    2016-05-01

    (E)-2-alkenals are aldehydes containing an unsaturated bond between the alpha and beta carbons. 2-alkenals are produced by many organisms for defense against predators and secretions containing (E)-2-alkenals cause predators to stop attacking and allow the prey to escape. Chemical ecologists have described many alkenal compounds with 3-20 carbons common, having varied positions of double bonds and substitutions. How do these defensive alkenals act to deter predators? We have tested the effects of (E)-2-alkenals with 6-12 carbons on transient receptor potential channels (TRP) commonly found in sensory neurons. We find that (E)-2-alkenals activate transient receptor potential ankyrin subtype 1 (TRPA1) at low concentrations-EC50s 10-100 µM (in 0 added Ca(2+) external solutions). Other TRP channels were either weakly activated (TRPV1, TRPV3) or insensitive (TRPV2, TRPV4, TRPM8). (E)-2-alkenals may activate TRPA1 by modifying cysteine side chains. However, target cysteines include others beyond the 3 in the amino-terminus implicated in activation, as a channel with cysteines at 621, 641, 665 mutated to serine responded robustly. Related chemicals, including the aldehydes hexanal and decanal, and (E)-2-hexen-1-ol also activated TRPA1, but with weaker potency. Rat trigeminal nerve recordings and behavioral experiments showed (E)-2-hexenal was aversive. Our results suggest that TRPA1 is likely a major target of these commonly used defensive chemicals. PMID:26843529

  15. 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

  16. Synthesis and structural characterization of the individual diastereoisomers of a cross-stapled alkene-bridged nisin DE-ring mimic.

    PubMed

    Slootweg, Jack C; Kemmink, Johan; Liskamp, Rob M J; Rijkers, Dirk T S

    2013-11-21

    Herein, we describe the synthesis, structural characterization, and synthetic use as an advanced intermediate of a cross-stapled alkene-bridged hexapeptide to mimic the DE-ring of the lantibiotic nisin. The linear precursor was cyclized by ring-closing metathesis to give the correctly folded bicyclic hexapeptide in a single step, and the four individual diastereoisomers were isolated, structurally assigned and characterized by HPLC, NMR and MS, respectively. The bicyclic hexapeptide was used as a versatile advanced synthon and was modified at its C- and N-terminus, among others, with an azide moiety to access a building block suitable for Cu(I)-catalyzed alkyne-azide cycloaddition-based ligation reactions. PMID:24081149

  17. Self-healing polymers---The importance of choosing an adequate healing monomer, and the olefin metathesis polymerization of agricultural oils

    NASA Astrophysics Data System (ADS)

    Mauldin, Timothy C.

    Modern society's immense and ill-fated reliance on petrochemical-based polymeric materials will likely necessitate a shift in polymer production paradigms in the near future. The work presented herein attempts to address this issue via a two-pronged approach. First, efforts to improve the duration of composite materials by incorporation of a self-healing function are discussed, the fruitful application of which can potentially reduce or eliminate the massive carbon footprints associated with the repair/replacement of damaged materials. And second, polymeric materials derived predominately from natural and renewable feedstock---namely vegetable oils---are developed. Early microcapsule-based self-healing materials utilized dicyclopentadiene-filled microcapsules and Grubbs' olefin metathesis catalyst to initiate the healing mechanism. However, the patent-protected catalyst, made from the precious metal ruthenium and sometimes costly ligands, will likely never be inexpensive and therefore limit large-scale applications. Hence, clever approaches to reduce the healing catalyst loading in self-healing polymers are of great interest. To this end, our efforts have revolved around solving the problem of the relatively inefficient use of Grubbs' catalyst during the healing mechanism. Given that the mismatch of the olefin metathesis polymerization and Grubbs' catalyst dissolution (in monomer) kinetics is a known cause of this inefficient use of the catalyst, we attempted to tune the "latency" (i.e. pot life) of the olefin metathesis polymerization to ensure more complete dissolution of catalyst in monomer. In an alternative approach to improving efficient catalyst dissolution, we developed a simple model to predict relative dissolution rates of Grubbs' catalyst in a small library of healing monomers. This model was shown experimentally to be able to aid in the selection of, for example, reactive monomer additives that can yield impressive improvements in catalyst dissolution

  18. Benchmark Energetic Data in a Model System for Grubbs II Metathesis Catalysis and Their Use for the Development, Assessment, and Validation of Electronic Structure Methods

    SciTech Connect

    Zhao, Yan; Truhlar, Donald G.

    2009-01-31

    We present benchmark relative energetics in the catalytic cycle of a model system for Grubbs second-generation olefin metathesis catalysts. The benchmark data were determined by a composite approach based on CCSD(T) calculations, and they were used as a training set to develop a new spin-component-scaled MP2 method optimized for catalysis, which is called SCSC-MP2. The SCSC-MP2 method has improved performance for modeling Grubbs II olefin metathesis catalysts as compared to canonical MP2 or SCS-MP2. We also employed the benchmark data to test 17 WFT methods and 39 density functionals. Among the tested density functionals, M06 is the best performing functional. M06/TZQS gives an MUE of only 1.06 kcal/mol, and it is a much more affordable method than the SCSC-MP2 method or any other correlated WFT methods. The best performing meta-GGA is M06-L, and M06-L/DZQ gives an MUE of 1.77 kcal/mol. PBEh is the best performing hybrid GGA, with an MUE of 3.01 kcal/mol; however, it does not perform well for the larger, real Grubbs II catalyst. B3LYP and many other functionals containing the LYP correlation functional perform poorly, and B3LYP underestimates the stability of stationary points for the cis-pathway of the model system by a large margin. From the assessments, we recommend the M06, M06-L, and MPW1B95 functionals for modeling Grubbs II olefin metathesis catalysts. The local M06-L method is especially efficient for calculations on large systems.

  19. Synthesis of cyclic sulfones by ring-closing metathesis.

    PubMed

    Yao, Qingwei

    2002-02-01

    A general and highly efficient synthesis of cyclic sulfones based on ring-closing metathesis has been developed. The synthetic utility of the resulting cyclic sulfones was demonstrated by their participation in stereoselective Diels-Alder reactions and transformation to cyclic dienes by the Ramberg-Bäcklund reaction. PMID:11820896

  20. 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

  1. 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

  2. Metal-catalyzed oxidation of 2-alkenals generates genotoxic 4-oxo-2-alkenals during lipid peroxidation.

    PubMed

    Nuka, Erika; Tomono, Susumu; Ishisaka, Akari; Kato, Yoji; Miyoshi, Noriyuki; Kawai, Yoshichika

    2016-10-01

    Lipid peroxidation products react with cellular molecules, such as DNA bases, to form covalent adducts, which are associated with aging and disease processes. Since lipid peroxidation is a complex process and occurs in multiple stages, there might be yet unknown reaction pathways. Here, we analyzed comprehensively 2'-deoxyguanosine (dG) adducts with oxidized arachidonic acid using liquid chromatography-tandem mass spectrometry and found the formation of 7-(2-oxo-hexyl)-etheno-dG as one of the major unidentified adducts. The formation of this adduct was reproduced in the reaction of dG with 2-octenal and predominantly with 4-oxo-2-octenal (OOE). We also found that other 2-alkenals (with five or more carbons) generate corresponding 4-oxo-2-alkenal-type adducts. Importantly, it was found that transition metals enhanced the oxidation of C4-position of 2-octenal, leading to the formation of OOE-dG adduct. These findings demonstrated a new pathway for the formation of 4-oxo-2-alkenals during lipid peroxidation and might provide a mechanism for metal-catalyzed genotoxicity. PMID:27281652

  3. Synthesis of molybdenum nitrido complexes for triple-bond metathesis of alkynes and nitriles.

    SciTech Connect

    Wiedner, E. S.; Gallagher, K. J.; Johnson, M. A.; Kampf, J. W.

    2011-06-04

    Complexes of the type N {triple_bond} Mo(OR){sub 3} (R = tertiary alkyl, tertiary silyl, bulky aryl) have been synthesized in the search for molybdenum-based nitrile-alkyne cross-metathesis (NACM) catalysts. Protonolysis of known N {triple_bond} Mo(NMe{sub 2}){sub 3} led to the formation of N {triple_bond} Mo(O-2,6-{sup i}Pr{sub 2}C{sub 6}H{sub 3}){sub 3}(NHMe{sub 2}) (12), N {triple_bond} Mo(OSiPh{sub 3}){sub 3}(NHMe{sub 2}) (5-NHMe{sub 2}), and N {triple_bond} Mo(OCPh{sub 2}Me){sub 3}(NHMe{sub 2}) (17-NHMe{sub 2}). The X-ray structure of 12 revealed an NHMe{sub 2} ligand bound cis to the nitrido ligand, while 5-NHMe{sub 2} possessed an NHMe{sub 2} bound trans to the nitride ligand. Consequently, 17-NHMe{sub 2} readily lost its amine ligand to form N {triple_bond} Mo(OCPh{sub 2}Me){sub 3} (17), while 12 and 5-NHMe{sub 2} retained their amine ligands in solution. Starting from bulkier tris-anilide complexes, N {triple_bond} Mo(N[R]Ar){sub 3} (R = isopropyl, tert-butyl; Ar = 3,5-dimethylphenyl) allowed for the formation of base-free complexes N {triple_bond} Mo(OSiPh3)3 (5) and N {triple_bond} Mo(OSiPh{sub 2}tBu){sub 3} (16). Achievement of a NACM cycle requires the nitride complex to react with alkynes to form alkylidyne complexes; therefore the alkyne cross-metathesis (ACM) activity of the complexes was tested. Complex 5 was found to be an efficient catalyst for the ACM of 1-phenyl-1-butyne at room temperature. Complexes 12 and 5-NHMe{sub 2} were also active for ACM at 75 C, while 17-NHMe{sub 2} and 16 did not show ACM activity. Only 5 proved to be active for the NACM of anisonitrile, which is a reactive substrate in NACM catalyzed by tungsten. NACM with 5 required a reaction temperature of 180 C in order to initiate the requisite alkylidyne-to-nitride conversion, with slightly more than two turnovers achieved prior to catalyst deactivation. Known molybdenum nitrido complexes were screened for NACM activity under similar conditions, and only N {triple_bond} Mo

  4. Enantioselective copper-catalyzed carboetherification of unactivated alkenes.

    PubMed

    Bovino, Michael T; Liwosz, Timothy W; Kendel, Nicole E; Miller, Yan; Tyminska, Nina; Zurek, Eva; Chemler, Sherry R

    2014-06-16

    Chiral saturated oxygen heterocycles are important components of bioactive compounds. Cyclization of alcohols onto pendant alkenes is a direct route to their synthesis, but few catalytic enantioselective methods enabling cyclization onto unactivated alkenes exist. Herein reported is a highly efficient copper-catalyzed cyclization of γ-unsaturated pentenols which terminates in C-C bond formation, a net alkene carboetherification. Both intra- and intermolecular C-C bond formations are demonstrated, thus yielding functionalized chiral tetrahydrofurans as well as fused-ring and bridged-ring oxabicyclic products. Transition-state calculations support a cis-oxycupration stereochemistry-determining step. PMID:24798697

  5. Evolution of Catalytic Stereoselective Olefin Metathesis: From Ancillary Transformation to Purveyor of Stereochemical Identity

    PubMed Central

    2015-01-01

    There have been numerous significant advances in catalytic olefin metathesis (OM) during the past two decades. Such progress has transformed this important set of reactions to strategically pivotal processes that generate stereochemical identity while delivering molecules that cannot be easily prepared by alternative routes. In this Perspective, an analysis of the origin of the inception of bidentate benzylidene ligands for Ru-based OM catalysts is first presented. This is followed by an overview of the intellectual basis that culminated in the development of Mo-based diolates and stereogenic-at-Ru complexes for enantioselective OM. The principles accrued from the study of the latter Ru carbenes and Mo alkylidenes and utilized in the design of stereogenic-at-Mo, -W, and -Ru species applicable to enantioselective and Z-selective OM are then discussed. The influence of the recently introduced catalytic OM protocols on the design of synthesis routes leading to complex organic molecules is probed. The impact of a better understanding of the mechanistic nuances of OM toward the discovery of stereoselective catalysts is reviewed as well. PMID:24720633

  6. Activation of Ene-Diamido Samarium Methoxide with Hydrosilane for Selectively Catalytic Hydrosilylation of Alkenes and Polymerization of Styrene: an Experimental and Theoretical Mechanistic Study.

    PubMed

    Li, Jianfeng; Zhao, Chaoyue; Liu, Jinxi; Huang, Hanmin; Wang, Fengxin; Xu, Xiufang; Cui, Chunming

    2016-09-01

    Samarium methoxide incorporating the ene-diamido ligand L(DME)Sm(μ-OMe)2Sm(DME)L (1; L = [DipNC(Me)C(Me)NDip](2-), Dip = 2,6-iPr2C6H3, and DME = 1,2-dimethoxyethane) has been prepared and structurally characterized. Complex 1 catalyzed the syndiospecific polymerization of styrene upon activation with phenylsilane and regioselective hydrosilylation of styrenes and nonactivated terminal alkenes. Unprecedented regioselectivity (>99.0%) for both types of alkenes has been achieved with the formation of Markovnikov and anti-Markovnikov products in high yields, respectively, whereas the polymerization of styrene resulted in the formation of syndiotactic silyl-capped oligostyrenes. The kinetic experiments and density functional theory calculations strongly support a samarium hydride intermediate generated by σ-bond metathesis of the Sm-OMe bond in 1 with PhSiH3. In addition, the observed regioselectvity for hydrosilylation and polymerization is consistent with the calculated energy profiles, which suggests that the bulky ene-diamido ligand and samarium hydride intermediate have important roles for regio- and stereoselectivity. PMID:27547859

  7. Synthesis of an Epoxide Carbonylation Catalyst: Exploration of Contemporary Chemistry for Advanced Undergraduates

    ERIC Educational Resources Information Center

    Getzler, Yutan D. Y. L.; Schmidt, Joseph A. R.; Coates, Geoffrey W.

    2005-01-01

    A class of highly active, well-defined compounds for the catalytic carbonylation of epoxides and aziridines to beta-lactones and beta-lactams are introduced. The synthesis of one of the catalysts involves a simple imine condensation to form the ligand followed by air-sensitive metalation and salt metathesis steps.

  8. Synthesis of Cembranoid Analogues through Ring-Closing Metathesis of Terpenoid Precursors: A Challenge Regarding Ring-Size Selectivity.

    PubMed

    Heidt, Tanja; Baro, Angelika; Köhn, Andreas; Laschat, Sabine

    2015-08-24

    A systematic study on ring-closing metathesis with Grubbs II catalyst to cembranoid macrocycles is described. Acyclic terpenoids with a functional group X in the homoallylic position relative to an RCM active terminus and substituents R, R(1) directly attached to the other terminal double bond were prepared from geraniol derived trienes and fragments that are based on bromoalkenes and dimethyl malonate. Such terpenoids were suitable precursors, despite the presence of competing double bonds in their framework. The size of R and R(1) is crucial for successful macrocyclization. Whereas small alkyl substituents at the double bond directed the RCM towards six-membered ring formation, cross metathesis leading to dimers dominated for bulkier alkyl groups. A similar result was obtained for precursors without functional group X. In the case of unsymmetrically substituted terpenoid precursor (R = Et, R(1) = Me) with homoallylic OTBS or OMe group, the RCM could be controlled towards formation of macrocyclic cembranoids, which were isolated with excellent E-selectivity. The role of the substituents was further studied by quantum chemical calculations of simplified model substrates. Based on these results a mechanistic rationale is proposed. PMID:26227568

  9. Biomimetic iron-catalyzed asymmetric epoxidation of aromatic alkenes by using hydrogen peroxide.

    PubMed

    Gelalcha, Feyissa Gadissa; Anilkumar, Gopinathan; Tse, Man Kin; Brückner, Angelika; Beller, Matthias

    2008-01-01

    A novel and general biomimetic non-heme Fe-catalyzed asymmetric epoxidation of aromatic alkenes by using hydrogen peroxide is reported herein. The catalyst consists of ferric chloride hexahydrate (FeCl(3)6 H(2)O), pyridine-2,6-dicarboxylic acid (H(2)(pydic)), and readily accessible chiral N-arenesulfonyl-N'-benzyl-substituted ethylenediamine ligands. The asymmetric epoxidation of styrenes with this system gave high conversions but poor enantiomeric excesses (ee), whereas larger alkenes gave high conversions and ee values. For the epoxidation of trans-stilbene (1 a), the ligands (S,S)-N-(4-toluenesulfonyl)-1,2-diphenylethylenediamine ((S,S)-4 a) and its N'-benzylated derivative ((S,S)-5 a) gave opposite enantiomers of trans-stilbene oxide, that is, (S,S)-2 a and (R,R)-2 a, respectively. The enantioselectivity of alkene epoxidation is controlled by steric and electronic factors, although steric effects are more dominant. Preliminary mechanistic studies suggest the in situ formation of several chiral Fe-complexes, such as [FeCl(L*)(2)(pydic)]HCl (L*=(S,S)-4 a or (S,S)-5 a in the catalyst mixture), which were identified by ESIMS. A UV/Vis study of the catalyst mixture, which consisted of FeCl(3)6 H(2)O, H(2)(pydic), and (S,S)-4 a, suggested the formation of a new species with an absorbance peak at lambda=465 nm upon treatment with hydrogen peroxide. With the aid of two independent spin traps, we could confirm by EPR spectroscopy that the reaction proceeds via radical intermediates. Kinetic studies with deuterated styrenes showed inverse secondary kinetic isotope effects, with values of k(H)/k(D)=0.93 for the beta carbon and k(H)/k(D)=0.97 for the alpha carbon, which suggested an unsymmetrical transition state with stepwise O transfer. Competitive epoxidation of para-substituted styrenes revealed a linear dual-parameter Hammett plot with a slope of 1.00. Under standard conditions, epoxidation of 1 a in the presence of ten equivalents of H(2) (18)O resulted in an absence

  10. Facile synthesis of brush poly(phosphoamidate)s via one-pot tandem ring-opening metathesis polymerization and atom transfer radical polymerization.

    PubMed

    Ding, Liang; Qiu, Jun; Wei, Jun; Zhu, Zhenshu

    2014-09-01

    Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA)-based brush poly(phosphoamidate)s are successfully synthesized by a combination of ring-opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP) following either a commutative two-step procedure or a straightforward one-pot process using Grubbs ruthenium-based catalysts for tandem catalysis. Compared with the traditional polymerization method, combining ROMP and ATRP in a one-pot process allows the preparation of brush copolymers characterized by a relatively moderate molecular weight distribution and quantitative conversion of monomer. Moreover, the surface morphologies and aggregation behaviors of these polymers are studied by AFM and TEM measurements. PMID:24729161

  11. Fischer–Tropsch Synthesis: Characterization Rb Promoted Iron Catalyst

    SciTech Connect

    Sarkar,A.; Jacobs, G.; Ji, Y.; Hamdeh, H.; Davis, B.

    2008-01-01

    Rubidium promoted iron Fischer-Tropsch synthesis (FTS) catalysts were prepared with two Rb/Fe atomic ratios (1.44/100 and 5/100) using rubidium nitrate and rubidium carbonate as rubidium precursors. Results of catalytic activity and deactivation studies in a CSTR revealed that rubidium promoted catalysts result in a steady conversion with a lower deactivation rate than that of the corresponding unpromoted catalyst although the initial activity of the promoted catalyst was almost half that of the unpromoted catalyst. Rubidium promotion results in lower methane production, and higher CO2, alkene and 1-alkene fraction in FTS products. M{umlt o}ssbauer spectroscopic measurements of CO activated and working catalyst samples indicated that the composition of the iron carbide phase formed after carbidization was -Fe5 C2 for both promoted and unpromoted catalysts. However, in the case of the rubidium promoted catalyst, '-Fe2.2C became the predominant carbidic phase as FTS continued and the overall catalyst composition remained carbidic in nature. In contrast, the carbide content of the unpromoted catalyst was found to decline very quickly as a function of synthesis time. Results of XANES and EXAFS measurements suggested that rubidium was present in the oxidized state and that the compound most prevalent in the active catalyst samples closely resembled that of rubidium carbonate.

  12. Synthesis of rhenium-alkene complexes from the reaction of the heterobimetallic dihydride C sub 5 H sub 5 (CO) sub 2 HRe-PtH(PPh sub 3 ) sub 2 with alkynes

    SciTech Connect

    Casey, C.P.; Rutter, E.W. Jr. )

    1989-11-22

    Heterobimetallic compounds hold great promise as catalysts since the 2 different metals have the potential of acting cooperatively. The authors report that the new heterobimetallic dihydride C{sub 5}H{sub 5}(CO){sub 2}HRe-PtH(PPh{sub 3}){sub 2} (I){sup 2} acts as a catalyst for ethylene hydrogenation and reacts stoichiometrically with alkynes to produce rhenium-alkene complexes.

  13. Modification of the butenyl-spinosyns utilizing cross-metathesis.

    PubMed

    Daeuble, John; Sparks, Thomas C; Johnson, Peter; Graupner, Paul R

    2009-06-15

    The discovery of a strain of Saccharopolyspora sp. that produced a number of spinosyn analogs that had not before been seen gave an ideal opportunity for extending our knowledge of that SAR of these highly efficacious insecticides. In particular, these compounds contained a butenyl group connected to C-21 which in the regular spinosyns was substituted with a simple ethyl group. The double bond therefore gave us a handle to further modify this position allowing us to substitute different groups there. In this paper we show one of our approaches to this modification using olefin cross-metathesis. Even though the spinosyns were not highly efficient substrates for metathesis reactions, we were nevertheless successful in extending their chemistry accordingly. PMID:19303781

  14. Rare-earth-metal nitridophosphates through high-pressure metathesis.

    PubMed

    Kloss, Simon David; Schnick, Wolfgang

    2015-09-14

    Developing a synthetic method to target an broad spectrum of unknown phases can lead to fascinating discoveries. The preparation of the first rare-earth-metal nitridophosphate LiNdP4 N8 is reported. High-pressure solid-state metathesis between LiPN2 and NdF3 was employed to yield a highly crystalline product. The in situ formed LiF is believed to act both as the thermodynamic driving force and as a flux to aiding single-crystal formation in dimensions suitable for crystal structure analysis. Magnetic properties stemming from Nd(3+) ions were measured by SQUID magnetometry. LiNdP4 N8 serves as a model system for the exploration of rare-earth-metal nitridophosphates that may even be expanded to transition metals. High-pressure metathesis enables the systematic study of these uncharted regions of nitride-based materials with unprecedented properties. PMID:26352033

  15. A cross-metathesis approach to novel pantothenamide derivatives

    PubMed Central

    Guan, Jinming; Hachey, Matthew; Puri, Lekha; Howieson, Vanessa; Saliba, Kevin J

    2016-01-01

    Summary Pantothenamides are known for their in vitro antimicrobial activity. Our group has previously reported a new stereoselective route to access derivatives modified at the geminal dimethyl moiety. This route however fails in the addition of large substituents. Here we report a new synthetic route that exploits the known allyl derivative, allowing for the installation of larger groups via cross-metathesis. The method was applied in the synthesis of a new pantothenamide with improved stability in human blood. PMID:27340487

  16. Block copolymer adhesion promoters via ring-opening metathesis polymerization

    DOEpatents

    Kent, Michael S.; Saunders, Randall

    1997-01-01

    Coupling agents based on functionalized block copolymers for bonding thermoset polymers to solid materials. These are polymers which possess at least two types of functional groups, one which is able to attach to and react with solid surfaces, and another which can react with a thermoset resin, which are incorporated as pendant groups in monomers distributed in blocks (typically two) along the backbone of the chain. The block copolymers in this invention are synthesized by living ring-opening metathesis polymerization.

  17. 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

  18. 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

  19. Synthesis of cyclic polybutadiene via ring-opening metathesis polymerization: the importance of removing trace linear contaminants.

    PubMed

    Bielawski, Christopher W; Benitez, Diego; Grubbs, Robert H

    2003-07-16

    The synthesis of cyclic polybutadienes using ring-opening metathesis polymerization (ROMP) was accomplished. A cyclic Ru alkylidene catalyst, where a terminal ligand was covalently linked to the Ru alkylidene, was used to polymerize either 1,5-cyclooctadiene (COD) or 1,5,9-trans-cis-trans-cyclododecatriene (CDT). Trace amounts of an acyclic impurity, 4-vinylcyclohexene, found in the COD led to samples which were contaminated with linear polymer. In contrast, CDT, which was free of the impurity, afforded pure cyclic polymer. These results provide a convenient method for discerning samples of pure cyclic polymer from those which contain trace to large amounts of linear polymer. Furthermore, they emphasize the need to use monomers that are free of acyclic impurities when preparing cyclic polymers using ROMP. PMID:12848534

  20. Validating the alkene and alkyne hydrophosphonylation as an entry to organophosphonates.

    PubMed

    Dondoni, Alessandro; Marra, Alberto

    2015-02-28

    The first paper on the hydrophosphonylation of terminal alkenes was published in 1958 by Stiles and coworkers. Afterwards various papers described organometal-catalyzed and free-radical reactions leading to linear anti-Markovnikov adducts and/or branched Markovnikov products. In 1996 Han and Tanaka reported the first example of alkyne hydrophosphonylation catalyzed by a palladium complex. Further studies using other metal catalysts registered poor selectivity as mixtures of adducts were obtained in most of the cases examined. The first example of alkyne hydrophosphonylation by H-phosphonates under free-radical conditions leading to Z- and E-vinylphosphonates in a 1 : 1 ratio was reported by our group. Nevertheless, Z- to E-isomerization took place upon irradiation in the presence of a thiol. PMID:25609561

  1. Product Control in Alkene Trifluoromethylation: Hydrotrifluoromethylation, Vinylic Trifluoromethylation, and Iodotrifluoromethylation using Togni Reagent.

    PubMed

    Egami, Hiromichi; Usui, Yoshihiko; Kawamura, Shintaro; Nagashima, Sayoko; Sodeoka, Mikiko

    2015-10-01

    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

  2. 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

  3. Alkenes as azido precursors for the one-pot synthesis of 1,2,3-triazoles catalyzed by copper nanoparticles on activated carbon.

    PubMed

    Alonso, Francisco; Moglie, Yanina; Radivoy, Gabriel; Yus, Miguel

    2013-05-17

    A one-pot protocol for the synthesis of 1,2,3-triazoles has been developed starting from inactivated alkenes and based on two click reactions: the azidosulfenylation of the carbon-carbon double bond and the copper-catalyzed azide-alkyne cycloaddition (CuAAC). High yields of the β-methylsulfanyl triazoles have been attained using CuNPs/C as catalyst, with other commercial copper catalysts being completely inactive. The versatility of the methylsulfanyl group has been demonstrated through a series of synthetic transformations, including direct access to 1-vinyl and 4-monosubstituted triazoles. PMID:23617398

  4. Titania-Promoted Carboxylic Acid Alkylations of Alkenes and Cascade Addition–Cyclizations

    PubMed Central

    2014-01-01

    Photochemical reactions employing TiO2 and carboxylic acids under dry anaerobic conditions led to several types of C–C bond-forming processes with electron-deficient alkenes. The efficiency of alkylation varied appreciably with substituents in the carboxylic acids. The reactions of aryloxyacetic acids with maleimides resulted in a cascade process in which a pyrrolochromene derivative accompanied the alkylated succinimide. The selectivity for one or other of these products could be tuned to some extent by employing the photoredox catalyst under different conditions. Aryloxyacetic acids adapted for intramolecular ring closures by inclusion of 2-alkenyl, 2-aryl, or 2-oximinyl functionality reacted rather poorly. Profiles of reactant consumption and product formation for these systems were obtained by an in situ NMR monitoring technique. An array of different catalyst forms were tested for efficiency and ease of use. The proposed mechanism, involving hole capture at the TiO2 surface by the carboxylates followed by CO2 loss, was supported by EPR spectroscopic evidence of the intermediates. Deuterium labeling indicated that the titania likely donates protons from surface hydroxyl groups as well as supplying electrons and holes, thus acting as both a catalyst and a reaction partner. PMID:24437519

  5. Regioselective alkene carbon-carbon bond cleavage to aldehydes and chemoselective alcohol oxidation of allylic alcohols with hydrogen peroxide catalyzed by [cis-Ru(II)(dmp)2(H2O)2]2+ (dmp = 2,9-dimethylphenanthroline).

    PubMed

    Kogan, Vladimir; Quintal, Miriam M; Neumann, Ronny

    2005-10-27

    [reaction: see text] [cis-Ru(II)(dmp)2(H2O)2]2+ (dmp = 2,9-dimethylphenanthroline) was found to be a selective oxidation catalyst using hydrogen peroxide as oxidant. Thus, primary alkenes were very efficiently oxidized via direct carbon-carbon bond cleavage to the corresponding aldehydes as an alternative to ozonolysis. Secondary alkenes were much less reactive, leading to regioselective oxidation of substrates such as 4-vinylcyclohexene and 7-methyl-1,6-octadiene at the terminal position. Primary allylic alcohols were chemoselectively oxidized to the corresponding allylic aldehydes, e.g., geraniol to citral. PMID:16235952

  6. Subnanometer-sized Pt/Sn alloy cluster catalysts for the dehydrogenation of linear alkanes.

    PubMed

    Hauser, Andreas W; Gomes, Joseph; Bajdich, Michal; Head-Gordon, Martin; Bell, Alexis T

    2013-12-21

    The reaction pathways for the dehydrogenation of ethane, propane, and butane, over Pt are analyzed using density functional theory (DFT). Pt nanoparticles are represented by a tetrahedral Pt4 cluster. The objectives of this work were to establish which step is rate limiting and which one controls the selectivity for forming alkenes as opposed to causing further dehydrogenation of adsorbed alkenes to produce precursors responsible for catalyst deactivation due to coking. Further objectives of this work are to identify the role of adsorbed hydrogen, derived from H2 fed together with the alkane, on the reaction pathway, and the role of replacing one of the four Pt atoms by a Sn atom. A comparison of Gibbs free energies shows that in all cases the rate-determining step is cleavage of a C-H bond upon alkane adsorption. The selectivity to alkene formation versus precursors to coking is dictated by the relative magnitudes of the activation energies for alkene desorption and dehydrogenation of the adsorbed alkene. The presence of an adsorbed H atom on the cluster facilitates alkene desorption relative to dehydrogenation of the adsorbed alkene. Substitution of a Sn atom in the cluster to produce a Pt3Sn cluster leads to a downward shift of the potential energy surface for the reaction and causes an increase of the activity of the catalyst as suggested by recent experiments due to the lower net activation barrier for the rate limiting step. However, the introduction of Sn does not alter the relative activation barriers for gas-phase alkene formation versus loss of hydrogen from the adsorbed alkene, the process leading to the formation of coke precursors. PMID:24196250

  7. Reduction in Syllable Onsets in the Acquisition of Polish: Deletion, Coalescence, Metathesis and Gemination

    ERIC Educational Resources Information Center

    Lukaszewicz, Beata

    2007-01-01

    This paper focuses on four strategies of onset reduction employed by a single child (4;0-4;4) acquiring Polish: deletion, coalescence, metathesis, and gemination. Deletion and coalescence occur in word-initial onsets while metathesis and gemination are restricted to word-medial position. The data, which constitute an intriguing "conspiracy" case…

  8. 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. PMID:26164646

  9. 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

  10. The Olefin Metathesis Reactions Combined with Organo-Iron Arene Activation Towards Dendrimers, and Polymers

    NASA Astrophysics Data System (ADS)

    Astruc, Didier; Martinez, Victor

    The subjects treated in the two lectures of the North Atlantic Treaty Organization (NATO) summer course are (1) the combination of arene activation and perfunctionalization using organo-iron chemistry with olefin metathesis incuding metathesis of dendritic polyolefin molecules; (2) the synthesis of metallodendritic benzylidene complexes that catalyse ring-opening metathesis polymerization (ROMP) under ambient conditions and the formation of dendritic stars; (3) the use of stoichiometric and catalytic electron-transfer processes with standard reservoirs of electrons (reductants) or electron holes (oxidants) iron complexes to achieve noteworthy metathesis reactions or synthesize compounds that are useful in metathesis. Only the two first topics are treated in this chapter, and interested readers can find references concerning the third aspect called in the introduction and subsequently cited in the reference list.

  11. Non-aqueous metathesis as a general approach to prepare nanodispersed materials: Case study of scheelites

    NASA Astrophysics Data System (ADS)

    Afanasiev, Pavel

    2015-09-01

    A general approach to the preparation of inorganic nanoparticles is proposed, using metathesis of precursor salts in non-aqueous liquids. Nanoparticles of scheelites AMO4 (A=Ba, Sr, Ca; M=Mo, W), were obtained with a quantitative yield. Precipitations in formamide, N-methylformamide, propylene carbonate, DMSO and polyols often provide narrow particle size distributions. Advantageous morphology was explained by strong ionic association in non-aqueous solvents, leading to slow nucleation and negligible Ostwald ripening. Mean particle size below 10 nm and high specific surface areas were obtained for several Ca(Sr)Mo(W)O4 materials, making them promising for applications as adsorbents or catalysts. Zeta-potential of scheelites in aqueous suspensions showed negative values in a wide range of pH. Systematic study of optical properties demonstrated variation of optical gap in the sequences W>Mo and Ba>Sr>Ca. The observed trends were reproduced by DFT calculations. No quantum confinement effect was observed for small particles, though the surface states induce low-energy features in the optical spectra.

  12. DFT studies on the directing group dependent arene-alkene cross-couplings: arene activation vs. alkene activation.

    PubMed

    Zhang, Lei; Fang, De-Cai

    2015-08-01

    Due to its green-chemistry advantages, the dehydrogenative Heck reaction (DHR) has experienced enormous growth over the past few decades. In this work, two competing reaction channels were comparatively studied for the Pd(OAc)2-catalyzed DHRs of arenes with alkenes, referred to herein as the arene activation mechanism and the alkene activation mechanism, respectively, which mainly differ in the involvement of the reactants in the C-H activation step. Our calculations reveal that the commonly accepted arene activation mechanism is plausible for the desired arene-alkene cross-coupling; in contrast, the alternative alkene activation mechanism is kinetically inaccessible for the desired cross-coupling, but it is feasible for the homo-coupling of alkenes. The nature of directing groups on reactants could mainly determine the dominance of the two competing reaction routes, and therefore, influence the experimental yields. A wide range of directing groups experimentally used are examined by the density functional theory (DFT) method in this work, providing theoretical guidance for screening compatible reactants. PMID:26108375

  13. 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

  14. Structurally Defined Molecular Hypervalent Iodine Catalysts for Intermolecular Enantioselective Reactions

    PubMed Central

    Haubenreisser, Stefan; Wöste, Thorsten H.; Martínez, Claudio; Ishihara, Kazuaki

    2015-01-01

    Abstract Molecular structures of the most prominent chiral non‐racemic hypervalent iodine(III) reagents to date have been elucidated for the first time. The formation of a chirally induced supramolecular scaffold based on a selective hydrogen‐bonding arrangement provides an explanation for the consistently high asymmetric induction with these reagents. As an exploratory example, their scope as chiral catalysts was extended to the enantioselective dioxygenation of alkenes. A series of terminal styrenes are converted into the corresponding vicinal diacetoxylation products under mild conditions and provide the proof of principle for a truly intermolecular asymmetric alkene oxidation under iodine(I/III) catalysis. PMID:26596513

  15. Joint toxic effects of the type-2 alkene electrophiles.

    PubMed

    Zhang, Lihai; Geohagen, Brian C; Gavin, Terrence; LoPachin, Richard M

    2016-07-25

    Human populations are exposed to complex environmental mixtures of acrolein, methylvinyl ketone (MVK) and other type-2 alkenes. Many members of this chemical class are electrophiles that possess a common molecular mechanism of toxicity; i.e., protein inactivation via formation of stable cysteine adducts. Therefore, acute or chronic exposure to type-2 alkene mixtures could represent a health risk due to additive or synergistic interactions among component chemicals. Despite this risk, there is little experimental information regarding the joint effects of type-2 alkenes. In the present study we used sum of toxic units (TUsum = ∑TUi) to assess the relative toxicity of different type-2 alkene mixtures. These studies involved well characterized environmental type-2 alkene toxicants and included amide (acrylamide; ACR), ketone (methyl vinyl ketone; MVK), aldehyde (2-ethylacrolein; EA) and ester (methyl acrylate; MA) derivatives. In chemico analyses revealed that both binary and ternary mixtures could deplete thiol groups according to an additive joint effect at equitoxic and non-equitoxic ratios; i.e., TUsum = 1.0 ± 0.20. In contrast, analyses of joint effects in SNB19 cell cultures indicated that different permutations of type-2 alkene mixtures produced mostly synergistic joint effects with respect to cell lethality; i.e., TUsum < 0.80. A mixture of ACR and MA was shown to produce joint toxicity in a rat model. This mixture accelerated the onset and development of neurotoxicity relative to the effects of the individual toxicants. Synergistic effects in biological models might occur when different cellular proteomes are targeted, whereas additive effects develop when the mixtures encompasses a similar proteome. PMID:27288850

  16. 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

  17. 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.

  18. "Zipped Synthesis" by Cross-Metathesis Provides a Cystathionine β-Synthase Inhibitor that Attenuates Cellular H2S Levels and Reduces Neuronal Infarction in a Rat Ischemic Stroke Model.

    PubMed

    McCune, Christopher D; Chan, Su Jing; Beio, Matthew L; Shen, Weijun; Chung, Woo Jin; Szczesniak, Laura M; Chai, Chou; Koh, Shu Qing; Wong, Peter T-H; Berkowitz, David B

    2016-04-27

    The gaseous neuromodulator H2S is associated with neuronal cell death pursuant to cerebral ischemia. As cystathionine β-synthase (CBS) is the primary mediator of H2S biogenesis in the brain, it has emerged as a potential target for the treatment of stroke. Herein, a "zipped" approach by alkene cross-metathesis into CBS inhibitor candidate synthesis is demonstrated. The inhibitors are modeled after the pseudo-C 2-symmetric CBS product (l,l)-cystathionine. The "zipped" concept means only half of the inhibitor needs be constructed; the two halves are then fused by olefin cross-metathesis. Inhibitor design is also mechanism-based, exploiting the favorable kinetics associated with hydrazine-imine interchange as opposed to the usual imine-imine interchange. It is demonstrated that the most potent "zipped" inhibitor 6S reduces H2S production in SH-SY5Y cells overexpressing CBS, thereby reducing cell death. Most importantly, CBS inhibitor 6S dramatically reduces infarct volume (1 h post-stroke treatment; ∼70% reduction) in a rat transient middle cerebral artery occlusion model for ischemia. PMID:27163055

  19. “Zipped Synthesis” by Cross-Metathesis Provides a Cystathionine β-Synthase Inhibitor that Attenuates Cellular H2S Levels and Reduces Neuronal Infarction in a Rat Ischemic Stroke Model

    PubMed Central

    2016-01-01

    The gaseous neuromodulator H2S is associated with neuronal cell death pursuant to cerebral ischemia. As cystathionine β-synthase (CBS) is the primary mediator of H2S biogenesis in the brain, it has emerged as a potential target for the treatment of stroke. Herein, a “zipped” approach by alkene cross-metathesis into CBS inhibitor candidate synthesis is demonstrated. The inhibitors are modeled after the pseudo-C2-symmetric CBS product (l,l)-cystathionine. The “zipped” concept means only half of the inhibitor needs be constructed; the two halves are then fused by olefin cross-metathesis. Inhibitor design is also mechanism-based, exploiting the favorable kinetics associated with hydrazine-imine interchange as opposed to the usual imine–imine interchange. It is demonstrated that the most potent “zipped” inhibitor 6S reduces H2S production in SH-SY5Y cells overexpressing CBS, thereby reducing cell death. Most importantly, CBS inhibitor 6S dramatically reduces infarct volume (1 h post-stroke treatment; ∼70% reduction) in a rat transient middle cerebral artery occlusion model for ischemia. PMID:27163055

  20. Difluorocarbene Addition to Alkenes and Alkynes in Continuous Flow.

    PubMed

    Rullière, Pauline; Cyr, Patrick; Charette, André B

    2016-05-01

    The first in-flow difluorocarbene generation and addition to alkenes and alkynes is reported. The application of continuous flow technology allowed for the controlled generation of difluorocarbene from TMSCF3 and a catalytic quantity of NaI. The in situ generated electrophilic carbene reacts smoothly with a broad range of alkenes and alkynes, allowing the synthesis of the corresponding difluorocyclopropanes and difluorocyclopropenes. The reaction is complete within a 10 min residence time at high reaction concentrations. With a production flow rate of 1 mmol/min, continuous flow chemistry enables scale up of this process in a green, atom-economic, and safe manner. PMID:27119573

  1. 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. PMID:26777629

  2. Bottlebrush Polymer Synthesis by Ring-Opening Metathesis Polymerization: The Significance of the Anchor Group.

    PubMed

    Radzinski, Scott C; Foster, Jeffrey C; Chapleski, Robert C; Troya, Diego; Matson, John B

    2016-06-01

    Control over bottlebrush polymer synthesis by ring-opening metathesis polymerization (ROMP) of macromonomers (MMs) is highly dependent on the competition between the kinetics of the polymerization and the lifetime of the catalyst. We evaluated the effect of anchor group chemistry-the configuration of atoms linking the polymer to a polymerizable norbornene-on the kinetics of ROMP of polystyrene and poly(lactic acid) MMs initiated by (H2IMes)(pyr)2(Cl)2Ru═CHPh (Grubbs third generation catalyst). We observed a variance in the rate of propagation of >4-fold between similar MMs with different anchor groups. This phenomenon was conserved across all MMs tested, regardless of solvent, molecular weight (MW), or repeat unit identity. The observed >4-fold difference in propagation rate had a dramatic effect on the maximum obtainable backbone degree of polymerization, with slower propagating MMs reducing the maximum bottlebrush MW by an order of magnitude (from ∼10(6) to ∼10(5) Da). A chelation mechanism was initially proposed to explain the observed anchor group effect, but experimental and computational studies indicated that the rate differences likely resulted from a combination of varying steric demands and electronic structure among the different anchor groups. The addition of trifluoroacetic acid to the ROMP reaction substantially increased the propagation rate for all anchor groups tested, likely due to scavenging of the pyridine ligands. Based on these data, rational selection of the anchor group is critical to achieve high MM conversion and to prepare pure, high MW bottlebrush polymers by ROMP grafting-through. PMID:27219866

  3. 40 CFR 721.3780 - Substituted and disubstituted tetrafluoro alkenes (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... tetrafluoro alkenes (generic). 721.3780 Section 721.3780 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.3780 Substituted and disubstituted tetrafluoro alkenes... substance identified generically as substituted and disubstituted tetrafluoro alkene (PMN P-84-105)...

  4. 40 CFR 721.4464 - Mixture of hydrofluoro alkanes and hydrofluoro alkene.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... hydrofluoro alkene. 721.4464 Section 721.4464 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... 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...

  5. 40 CFR 721.4464 - Mixture of hydrofluoro alkanes and hydrofluoro alkene.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... hydrofluoro alkene. 721.4464 Section 721.4464 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... 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...

  6. 40 CFR 721.3780 - Substituted and disubstituted tetrafluoro alkenes (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... tetrafluoro alkenes (generic). 721.3780 Section 721.3780 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.3780 Substituted and disubstituted tetrafluoro alkenes... substance identified generically as substituted and disubstituted tetrafluoro alkene (PMN P-84-105)...

  7. 40 CFR 721.4464 - Mixture of hydrofluoro alkanes and hydrofluoro alkene.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... hydrofluoro alkene. 721.4464 Section 721.4464 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... 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...

  8. 40 CFR 721.3780 - Substituted and disubstituted tetrafluoro alkenes (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... tetrafluoro alkenes (generic). 721.3780 Section 721.3780 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.3780 Substituted and disubstituted tetrafluoro alkenes... substance identified generically as substituted and disubstituted tetrafluoro alkene (PMN P-84-105)...

  9. 40 CFR 721.3780 - Substituted and disubstituted tetrafluoro alkenes (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... tetrafluoro alkenes (generic). 721.3780 Section 721.3780 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.3780 Substituted and disubstituted tetrafluoro alkenes... substance identified generically as substituted and disubstituted tetrafluoro alkene (PMN P-84-105)...

  10. 40 CFR 721.4464 - Mixture of hydrofluoro alkanes and hydrofluoro alkene.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... hydrofluoro alkene. 721.4464 Section 721.4464 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... 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...

  11. 40 CFR 721.3780 - Substituted and disubstituted tetrafluoro alkenes (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... tetrafluoro alkenes (generic). 721.3780 Section 721.3780 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.3780 Substituted and disubstituted tetrafluoro alkenes... substance identified generically as substituted and disubstituted tetrafluoro alkene (PMN P-84-105)...

  12. 40 CFR 721.4464 - Mixture of hydrofluoro alkanes and hydrofluoro alkene.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... hydrofluoro alkene. 721.4464 Section 721.4464 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... 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...

  13. Ring-closing metathesis reactions: interpretation of conversion-time data.

    PubMed

    Thiel, Vasco; Wannowius, Klaus-Jürgen; Wolff, Christiane; Thiele, Christina M; Plenio, Herbert

    2013-11-25

    Conversion-time data were recorded for various ring-closing metathesis (RCM) reactions that lead to five- or six-membered cyclic olefins by using different precatalysts of the Hoveyda type. Slowly activated precatalysts were found to produce more RCM product than rapidly activated complexes, but this comes at the price of slower product formation. A kinetic model for the analysis of the conversion-time data was derived, which is based on the conversion of the precatalyst (Pcat) into the active species (Acat), with the rate constant k(act), followed by two parallel reactions: 1) the catalytic reaction, which utilizes Acat to convert reactants into products, with the rate k(cat), and 2) the conversion of Acat into the inactive species (Dcat), with the rate k(dec). The calculations employ two experimental parameters: the concentration of the substrate (c(S)) at a given time and the rate of substrate conversion (-dc(S)/dt). This provides a direct measure of the concentration of Acat and enables the calculation of the pseudo-first-order rate constants k(act), k(cat), and k(dec) and of k(S) (for the RCM conversion of the respective substrate by Acat). Most of the RCM reactions studied with different precatalysts are characterized by fast k(cat) rates and by the k(dec) value being greater than the k(act) value, which leads to quasistationarity for Acat. The active species formed during the activation step was shown to be the same, regardless of the nature of different Pcats. The decomposition of Acat occurs along two parallel pathways, a unimolecular (or pseudo-first-order) reaction and a bimolecular reaction involving two ruthenium complexes. Electron-deficient precatalysts display higher rates of catalyst deactivation than their electron-rich relatives. Slowly initiating Pcats act as a reservoir, by generating small stationary concentrations of Acat. Based on this, it can be understood why the use of different precatalysts results in different substrate conversions in

  14. Block copolymer adhesion promoters via ring-opening metathesis polymerization

    DOEpatents

    Kent, M.S.; Saunders, R.

    1997-02-18

    Coupling agents are disclosed based on functionalized block copolymers for bonding thermoset polymers to solid materials. These are polymers which possess at least two types of functional groups, one which is able to attach to and react with solid surfaces, and another which can react with a thermoset resin, which are incorporated as pendant groups in monomers distributed in blocks (typically two) along the backbone of the chain. The block copolymers in this invention are synthesized by living ring-opening metathesis polymerization. 18 figs.

  15. Cardanol-based materials as natural precursors for olefin metathesis.

    PubMed

    Vasapollo, Giuseppe; Mele, Giuseppe; Del Sole, Roberta

    2011-01-01

    Cardanol is a renewable, low cost natural material, widely available as a by-product of the cashew industry. It is a mixture of 3-n-pentadecylphenol, 3-(pentadeca-8-enyl)phenol, 3-(pentadeca-8,11-dienyl)phenol and 3-(pentadeca-8,11,14-trienyl)phenol. Olefin metathesis (OM) reaction on cardanol is an important class of reactions that allows for the synthesis of new olefins that are sometime impossible to prepare via other methods. The application of this natural and renewable material to both academic and industrial research will be discussed. PMID:25134775

  16. Isomerization of C[sub 4] alkenes

    DOEpatents

    Smith, L.A. Jr.

    1984-11-13

    A method is described for isomerizing isobutene or n-butene to produce a mixture of isobutene and normal butene, and polymerizing at least a portion thereof to produce isobutene/n-butene co-dimer, which comprises feeding at least 80 weight % of either the isobutene or n-butene to a catalytic distillation reactor containing a fixed bed acidic cation exchange resin catalyst packing which provides both the catalyst sites and distillation sites for the reaction products, isomerizing a portion of the isobutene or n-butene to produce a mixture of isobutene and n-butene and reacting at least a portion of the isobutene and n-butene to form co-dimer of isobutene and n-butene, whereby an overhead fraction containing any unreacted isobutene and n-butene and a bottoms fraction containing co-dimer is produced. The result of the reaction is substantially the same regardless whether the feed is isobutene or n-butene. Other aspects of the invention, include combinations of procedures to produce high purity isobutene and n-butene. Either isobutene or n-butene product (depending on the desired product) can be recycled as feed, thus substantially carrying out the isomerization to extinction and total conversion to the desired product. 1 fig.

  17. Isomerization of C.sub.4 alkenes

    DOEpatents

    Smith, Jr., Lawrence A.

    1984-01-01

    A method for isomerizing isobutene or n-butene to produce a mixture of isobutene and normal butene, and polymerizing at least a portion thereof to produce isobutene/n-butene codimer, which comprieses feeding at least 80 weight % of either the isobutene or n-butene to a catalytic distillation reactor containing a fixed bed acidic cation exchange resin catalyst packing which provides both the catalyst sites and distillation sites for the reaction products, isomerizing a portion of the isobutene or n-butene to produce a mixture of isobutene and n-butene and reacting at least a portion of the isobutene and n-butene to form codimer of isobutene and n-butene, whereby an overhead fraction containing any unreacted isobutene and n-butene and a bottoms fraction containing codimer is produced. The result of the reaction is substantially the same regardless whether the feed is isobutene or n-butene. Other aspects of the invention, include combinations of procedures to produce high purity isobutene and n-butene. Either isobutene or n-butene product (depending on the desired product) can be recycled as feed, thus substantially carrying out the isomerization to extinction and total conversion to the desired product.

  18. Isomerizing ethenolysis as an efficient strategy for styrene synthesis.

    PubMed

    Baader, Sabrina; Ohlmann, Dominik M; Gooßen, Lukas J

    2013-07-22

    A shrinking chain: A bimetallic system consisting of [{Pd(μ-Br)(tBu3P)}2] and a ruthenium metathesis catalyst has been found to efficiently promote the cross-metathesis between substituted alkenes and ethylene, while continuously migrating the double bond along the alkenyl chain (see scheme). When alkenylarenes, such as the natural products eugenol, safrol, or estragol, were treated with this catalyst under an ethylene atmosphere, they were cleanly converted into the corresponding styrenes and propylene gas. PMID:23776109

  19. 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…

  20. Copper-mediated oxidative trifluoromethylthiolation of unactivated terminal alkenes.

    PubMed

    Zhang, Ke; Liu, Jian-Bo; Qing, Feng-Ling

    2014-11-25

    A general method to form a C(SP(3))-SCF3 bond via copper-mediated oxidative trifluoromethylthiolation of unactivated alkenes with stable nucleophilic AgSCF3 was developed. This protocol provides a direct and efficient access to a series of trifluoromethylthiolated allylic compounds with broad functional group tolerance. PMID:25277082

  1. 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

  2. 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

  3. Slurry phase Fischer-Tropsch synthesis: Cobalt plus a water-gas shift catalyst

    SciTech Connect

    Yates, I.C.; Satterfield, C.N.

    1990-01-01

    Experiments on cobalt-catalyzed reactions of light 1-alkenes added to synthesis gas were performed. Data have been collected at 220C, 0.45 to 1.48 MPa and a synthesis gas flow rate between 0.015 and 0.030 Nl/(gcat[center dot]min) with H[sub 2]/CO of 1.45 to 2.25. Ethylene, propene, and butene were added to synthesis gas feed from 0.5 to 1.2 mole% of total feed. For each material balance in which 1-alkenes were added, a material balance was performed at similar process conditions without 1-alkenes added, as base case''. Material balances without added 1-alkenes were also repeated to verify of catalyst selectivity stability. 49 material balances were performed during a single run lasting over 2,500 hours-on-stream. The hydrocarbon data have been completely analyzed; data correlations are still being made. Since C[sub 3]/C[sub 1] ratios by ethene addition, C[sub 4]/C[sub 1] ratios by propene addition, and C[sub 5]/C[sub 1] ratios by 1-butene addition, it appears that 1-alkenes may incorporate into growing chains on the surface of the catalyst. Further evidence for incorporation can be seen by comparing selectivity to n-alcohol one carbon number higher than added 1-alkene. Yield of this n-alcohol increases when alkenes are present. Sensitivity of hydrocarbon distribution to process variables seems to be greater on Co than on Fe catalysts.

  4. Oxidation catalyst

    DOEpatents

    Ceyer, Sylvia T.; Lahr, David L.

    2010-11-09

    The present invention generally relates to catalyst systems and methods for oxidation of carbon monoxide. The invention involves catalyst compositions which may be advantageously altered by, for example, modification of the catalyst surface to enhance catalyst performance. Catalyst systems of the present invention may be capable of performing the oxidation of carbon monoxide at relatively lower temperatures (e.g., 200 K and below) and at relatively higher reaction rates than known catalysts. Additionally, catalyst systems disclosed herein may be substantially lower in cost than current commercial catalysts. Such catalyst systems may be useful in, for example, catalytic converters, fuel cells, sensors, and the like.

  5. Synthesis of a tricyclic lactam via Beckmann rearrangement and ring-rearrangement metathesis as key steps

    PubMed Central

    Ravikumar, Ongolu; Majhi, Jadab

    2015-01-01

    Summary A tricyclic lactam is reported in a four step synthesis sequence via Beckmann rearrangement and ring-rearrangement metathesis as key steps. Here, we used a simple starting material such as dicyclopentadiene. PMID:26425207

  6. The hydrocarbon selectivity of cobalt Fischer-Tropsch catalysts

    SciTech Connect

    Yates, I.C.; Satterfield, C.N.

    1991-07-01

    A cobalt Fischer-Tropsch catalyst was studied in a continuous-flow, well-stirred slurry reactor at 220 to 240{degrees}C, 0.5 to 1.5 MPa, H{sub 2}/CO feed ratios between 1.5 and 3.5, H{sub 2} conversions between 6 and 68%, and CO conversions between 11 and 73%. Increasing space velocity (decreasing conversion) or decreasing reactor H{sub 2}/CO ratio decreased the yield of (undesired) C{sub 1} products and increased the yield of (desired) C{sub 10}+ products. Reactor temperature and pressure had little effect on the carbon number distribution. These findings are interpreted in terms of the extent of the readsorption of 1-alkenes into growing chains on the catalyst surface. The relative selectivity to 1-alkenes by the primary synthesis and secondary reaction of l-alkenes to n-alkanes and 2-alkenes depends on reactor H{sub 2}/CO ratio and CO concentration. 25 refs., 15 figs.

  7. Self‐Assembly of Disorazole C1 through a One‐Pot Alkyne Metathesis Homodimerization Strategy†

    PubMed Central

    Ralston, Kevin J.; Ramstadius, H. Clinton; Brewster, Richard C.; Niblock, Helen S.

    2015-01-01

    Abstract Alkyne metathesis is increasingly explored as a reliable method to close macrocyclic rings, but there are no prior examples of an alkyne‐metathesis‐based homodimerization approach to natural products. In this approach to the cytotoxic C2‐symmetric marine‐derived bis(lactone) disorazole C1, a highly convergent, modular strategy is employed featuring cyclization through an ambitious one‐pot alkyne cross‐metathesis/ring‐closing metathesis self‐assembly process. PMID:27346897

  8. Non-aqueous metathesis as a general approach to prepare nanodispersed materials: Case study of scheelites

    SciTech Connect

    Afanasiev, Pavel

    2015-09-15

    A general approach to the preparation of inorganic nanoparticles is proposed, using metathesis of precursor salts in non-aqueous liquids. Nanoparticles of scheelites AMO{sub 4} (A=Ba, Sr, Ca; M=Mo, W), were obtained with a quantitative yield. Precipitations in formamide, N-methylformamide, propylene carbonate, DMSO and polyols often provide narrow particle size distributions. Advantageous morphology was explained by strong ionic association in non-aqueous solvents, leading to slow nucleation and negligible Ostwald ripening. Mean particle size below 10 nm and high specific surface areas were obtained for several Ca(Sr)Mo(W)O{sub 4} materials, making them promising for applications as adsorbents or catalysts. Zeta-potential of scheelites in aqueous suspensions showed negative values in a wide range of pH. Systematic study of optical properties demonstrated variation of optical gap in the sequences W>Mo and Ba>Sr>Ca. The observed trends were reproduced by DFT calculations. No quantum confinement effect was observed for small particles, though the surface states induce low-energy features in the optical spectra. - Graphical abstract: Scheelites AMO{sub 4} (A=Ca, Sr, Ba; M=Mo, W) were prepared in various non-aqueous liquids with high specific surface areas and narrow size distributions. The optical gap of scheelites changes in the series Ca

  9. Slurry phase Fischer-Tropsch synthesis: Cobalt plus a water-gas shift catalyst

    SciTech Connect

    Chanenchuk, C.A.; Yates, I.C.; Satterfield, C.N.

    1990-01-01

    Experiments to study the cobalt-catalyzed and iron-catalyzed reactions of light 1-alkenes added to synthesis gas have been performed and analyzed. On cobalt, data have been obtained at 220{degrees}C, 0.45 to 1.48 MPA and a synthesis gas flow rate between 0.015 and 0.030 Nl/gcat/min with H{sub 2}/CO feeds of 1.45 to 2.25. On fused iron, data were collected at 248{degrees}C, 0.79 to 1.48 MPa and a synthesis gas flow rate between 0.005 and 0.030 Nl/gcat/min of H{sub 2}/CO feeds of 0.5 to 1.5 C{sub 2}H{sub 4}, C{sub 3}H{sub 6}, and 1-C{sub 4}H{sub 8} were added to the synthesis gas feed in concentrations ranging from 0.5 to 1.2 mol. % of total feed. 1-Alkenes incorporate into growing chains on the catalyst surface of both catalysts, probably by initiating and/or terminating the chain growth process. Only ethene is believed to propagate chain growth significantly. The propensity of the 1-alkenes to incorporate decreases with increasing carbon number of the 1-alkene. The double-{alpha} behavior which is exhibited by most Fischer-Tropsch catalysts can be explained as the sum of two growth processes, one stepwise single-carbon growth and the other 1-alkene incorporation. Both alkene addition study data and the effects of process variables on the selectivity of Fischer-Tropsch catalysts can be explained within the framework of this theory. 19 refs., 12 figs., 2 tabs.

  10. 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

  11. Phosphine-Catalyzed [2 + 4] Annulation of Allenoates with Thiazolone-Derived Alkenes: Synthesis of Functionalized 6,7-Dihydro-5H-pyrano[2,3-d]thiazoles.

    PubMed

    Wang, Chang; Gao, Zhenzhen; Zhou, Leijie; Yuan, Chunhao; Sun, Zhanhu; Xiao, Yumei; Guo, Hongchao

    2016-07-15

    Phosphine-catalyzed [2 + 4] annulation of allenoates with thiazolone-derived alkenes has been achieved under mild conditions, giving biologically important 6,7-dihydro-5H-pyrano[2,3-d]thiazole derivatives in high to excellent yields. With the use of Kwon's phosphine as the chiral catalyst, optically active products were obtained in good yields with excellent enantioselectivities. PMID:27378106

  12. Green diacetoxylation of alkenes in a microchemical system.

    PubMed

    Park, Jeong Hyeon; Park, Chan Yi; Song, Hyun Seung; Huh, Yun Suk; Kim, Geon Hee; Park, Chan Pil

    2013-02-15

    The palladium-catalyzed diacetoxylation and trifluoromethanesulfonic acid-catalyzed diacetoxylation using inexpensive and environmentally friendly hydrogen peroxide and peracetic acid were successfully conducted with the help of microchemical technology. Excellent yield and selectivity were achieved in significantly shortened reaction times without the decomposition of explosive oxidants and further transformation of unstable products, offering a safe and efficient alternative to traditional methods for alkene diacetoxylation. PMID:23373522

  13. Directed, Regiocontrolled Hydroamination of Unactivated Alkenes via Protodepalladation.

    PubMed

    Gurak, John A; Yang, Kin S; Liu, Zhen; Engle, Keary M

    2016-05-11

    A directed, regiocontrolled hydroamination of unactivated terminal and internal alkenes is reported. The reaction is catalyzed by palladium(II) acetate and is compatible with a variety of nitrogen nucleophiles. A removable bidentate directing group is used to control the regiochemistry, prevent β-hydride elimination, and stabilize the nucleopalladated intermediate, facilitating a protodepalladation event. This method affords highly functionalized γ-amino acids in good yields with high regioselectivity. PMID:27093112

  14. Nickel-Catalyzed Coupling of Alkenes, Aldehydes, and Silyl Triflates

    PubMed Central

    Ng, Sze-sze; Ho, Chun-Yu; Jamison, Timothy F.

    2011-01-01

    A full account of two recently developed nickel-catalyzed coupling reactions of alkenes, aldehydes and silyl triflates is presented. These reactions provide either allylic alcohol or homoallylic alcohol derivatives selectively, depending on the ligand employed. These processes are believed to be mechanistically distinct from Lewis acid-catalyzed carbonyl-ene reactions, and several lines of evidence supporting this hypothesis are discussed. PMID:16939275

  15. 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.

  16. 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

  17. Bidirectional cross metathesis and ring-closing metathesis/ring opening of a C 2-symmetric building block: a strategy for the synthesis of decanolide natural products

    PubMed Central

    Kunz, Oliver

    2013-01-01

    Summary Starting from the conveniently available ex-chiral pool building block (R,R)-hexa-1,5-diene-3,4-diol, the ten-membered ring lactones stagonolide E and curvulide A were synthesized using a bidirectional olefin-metathesis functionalization of the terminal double bonds. Key steps are (i) a site-selective cross metathesis, (ii) a highly diastereoselective extended tethered RCM to furnish a (Z,E)-configured dienyl carboxylic acid and (iii) a Ru–lipase-catalyzed dynamic kinetic resolution to establish the desired configuration at C9. Ring closure was accomplished by macrolactonization. Curvulide A was synthesized from stagonolide E through Sharpless epoxidation. PMID:24367418

  18. 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. PMID:27113486

  19. Cp2TiCl2-Catalyzed Regioselective Hydrocarboxylation of Alkenes with CO2.

    PubMed

    Shao, Peng; Wang, Sheng; Chen, Chao; Xi, Chanjuan

    2016-05-01

    Cp2TiCl2-catalyzed regioselective hydrocarboxylation of alkenes with CO2 to give carboxylic acids in high yields has been developed in the presence of (i)PrMgCl. The reaction proceeds with a wide range of alkenes under mild conditions. Styrene and its derivatives can transform to α-aryl carboxylic acids, and aliphatic alkenes can transform to form alkanoic acids. PMID:27097225

  20. Production of stabilized Criegee intermediates and peroxides in the gas phase ozonolysis of alkenes: 2. Asymmetric and biogenic alkenes

    NASA Astrophysics Data System (ADS)

    Hasson, Alam S.; Ho, Andy W.; Kuwata, Keith T.; Paulson, Suzanne E.

    2001-12-01

    Organic hydroperoxide, hydrogen peroxide, and >C1 carbonyl yields have been measured from the reaction of a set of structurally diverse and atmospherically significant terminal and exocyclic alkenes with ozone. Product yields were investigated for 1-butene, 1-pentene, 1-octene, methylene cyclohexane, β-pinene, camphene and isoprene for humidities from 0 to 80% using gas chromatography with flame ionization detection and high-performance liquid chromatography with fluorescence detection. The yields of these products were used to estimate the following stabilized Criegee intermediate yields: 1-butene (0.27), 1-pentene (0.29), 1-octene (0.36), methylene cyclohexane (0.18), β-pinene (0.28), camphene (0.31), and isoprene (0.27). The reaction of stabilized Criegee intermediates with water produces primarily hydroxymethyl hydroperoxide from CH2OO, and H2O2 and a carbonyl compound for larger Criegee intermediates; acid formation is expected to be low. The exception is camphene, for which the large Criegee intermediate generates the corresponding hydroxyalkyl hydroperoxide in its reaction with water. These results were used to develop a structure activity relationship to estimate stabilized Criegee intermediate yields and to demonstrate that this model is consistent with literature values for OH yields from these ozone-alkene reactions. The mechanisms of the formation of these products are discussed and a hypothesis for the decrease in OH formation with increasing chain length for terminal alkenes is provided. Finally, a parameterization of the reactions for incorporation into atmospheric models is developed.

  1. In Situ Catalyst Modification in Atom Transfer Radical Reactions with Ruthenium Benzylidene Complexes.

    PubMed

    Lee, Juneyoung; Grandner, Jessica M; Engle, Keary M; Houk, K N; Grubbs, Robert H

    2016-06-01

    Ruthenium benzylidene complexes are well-known as olefin metathesis catalysts. Several reports have demonstrated the ability of these catalysts to also facilitate atom transfer radical (ATR) reactions, such as atom transfer radical addition (ATRA) and atom transfer radical polymerization (ATRP). However, while the mechanism of olefin metathesis with ruthenium benzylidenes has been well-studied, the mechanism by which ruthenium benzylidenes promote ATR reactions remains unknown. To probe this question, we have analyzed seven different ruthenium benzylidene complexes for ATR reactivity. Kinetic studies by (1)H NMR revealed that ruthenium benzylidene complexes are rapidly converted into new ATRA-active, metathesis-inactive species under typical ATRA conditions. When ruthenium benzylidene complexes were activated prior to substrate addition, the resulting activated species exhibited enhanced kinetic reactivity in ATRA with no significant difference in overall product yield compared to the original complexes. Even at low temperature, where the original intact complexes did not catalyze the reaction, preactivated catalysts successfully reacted. Only the ruthenium benzylidene complexes that could be rapidly transformed into ATRA-active species could successfully catalyze ATRP, whereas other complexes preferred redox-initiated free radical polymerization. Kinetic measurements along with additional mechanistic and computational studies show that a metathesis-inactive ruthenium species, generated in situ from the ruthenium benzylidene complexes, is the active catalyst in ATR reactions. Based on data from (1) H, (13)C, and (31)P NMR spectroscopy and X-ray crystallography, we suspect that this ATRA-active species is a RuxCly(PCy3)z complex. PMID:27186790

  2. Phosphidoboratabenzene-rhodium(i) complexes as precatalysts for the hydrogenation of alkenes at room temperature and atmospheric pressure.

    PubMed

    Perez, Viridiana; Audet, Pierre; Bi, Wenhua; Fontaine, Frédéric-Georges

    2016-02-01

    The di-tert-butylphosphido-boratabenzene ligand (DTBB) reacts with [(C2H4)2RhCl]2 yielding the dimeric species [(C2H4)Rh(DTBB)]2 (1). This species was fully characterized by multinuclear NMR and X-ray crystallography. Complex 1 readily dissociates ethylene in solution and upon exposure to 1 atm of H2 is capable of carrying out the hydrogenation of ethylene. The characterization of two Rh-H species by multinuclear NMR spectroscopy is provided. The reactivity of 1 towards the catalytic hydrogenation of alkenes and alkynes at room temperature and 1 atm of H2 is reported and compared to the activity of Wilkinson's catalyst under the same reaction conditions. PMID:26530277

  3. Amphiphilic Cellulose Ethers Designed for Amorphous Solid Dispersion via Olefin Cross-Metathesis.

    PubMed

    Dong, Yifan; Mosquera-Giraldo, Laura I; Taylor, Lynne S; Edgar, Kevin J

    2016-02-01

    The design of cellulose ether-based amphiphiles has been difficult and limited because of the harsh conditions typically required for appending ether moieties to cellulose. Olefin cross-metathesis recently has been shown to be a valuable approach for appending a variety of functional groups to cellulose ethers and esters, provided that an olefin handle for metathesis can be attached. This synthetic pathway gives access to these functional derivatives under very mild conditions and at high efficiency. Modification of ethyl cellulose by metathesis to prepare useful derivatives, for example, for solubility and bioavailability enhancement of drugs by amorphous solid dispersion (ASD), has been limited by the low DS(OH) of commercial ethyl cellulose derivatives. This is problematic because ethyl cellulose is otherwise a very attractive substrate for synthesis of amphiphilic derivatives by olefin metathesis. Herein we explore two methods for opening up this design space for ether-based amphiphiles, for example, permitting synthesis of more hydrophilic derivatives. One approach is to start with the more hydrophilic commercial methyl cellulose, which contains much higher DS(OH) and therefore is better suited for introduction of high DS of olefin metathesis "handles". In another approach, we explored a homogeneous one-pot synthesis methodology from cellulose, where controlled DS of ethyl groups was introduced at the same time as the ω-unsaturated alkyl groups, thereby permitting complete control of DS(OH), DS(Et), and ultimately DS of the functional group added by metathesis. We describe the functionalized derivatives available by these successful approaches. In addition, we explore new methods for reduction of the unsaturation in initial metathesis products to provide robust methods for enhancing product stability against further radical-catalyzed reactions. We demonstrate initial evidence that the products show strong promise as amphiphilic matrix polymers for amorphous

  4. The surface chemistry of iron Fischer-Tropsch catalysts

    SciTech Connect

    Dwyer, D.J.; Hardenburgh, J.H.

    1986-04-01

    The indirect conversion of coal to liquid hydrocarbons via steam gasification followed by synthesis gas (CO/H/sub 2/) chemistry has been the subject of intensive study for a number of decades. A key technological challenge facing researchers in this area is control over the product distribution during the hydrocarbon synthesis step. In the case of iron Fischer-Tropsch catalysts, it has been known that the addition of alkali to the metal catalyst has a significant impact on the product distribution. Iron catalysts treated with alkali produce less methane more alkenes and higher molecular weight products. In spite of numerous investigations, the details of this promotional effect are not understood on a molecular level. To explore the role of alkali in the surface chemistry of iron catalysts, the authors have carried out a combined surface science and catalytic kinetic study of a model iron catalyst with and without surface alkali.

  5. Fischer-Tropsch reaction studies with supported ruthenium catalysts

    SciTech Connect

    Everson, R.C.; Mulder, H. )

    1993-09-01

    An investigation was undertaken to examine the production of low molecular weight alkenes (C[sub 2][sup =] to C[sup =][sub 4]) and high molecular weight hydrocarbons (C[sub 5]+) from synthesis gas in a fixed bed reactor with supported ruthenium catalyst. The catalyst used consisted of 0.5% ruthenium on gamma-alumina with a 43% metal dispersion. An experimental reactor consisting of a single 12.5-mm-diameter stainless-steel tube with catalyst packings up to 1 m long, surrounded by an aluminium block with heating elements and an outer insulating ceramic block was used. The effect of temperature, synthesis gas composition (CO/H[sub 2]), weight hourly space velocity (WHSV), and bed length on carbon monoxide conversion and selectivity was examined and results are reported. The presence of secondary reactions consisting of hydrogenation and chain growth involving alkenes along the reactor bed was observed. These reactions favour the formation of alkanes and high molecular weight hydrocarbons. The alkene to alkane ratio in the product can be increased by restricting the hydrogenation reaction with the use of a synthesis gas mixture with a high carbon monoxide to hydrogen ratio.

  6. Organic and composite aerogels through ring opening metathesis polymerization (ROMP)

    NASA Astrophysics Data System (ADS)

    Mohite, Dhairyashil P.

    Aerogels are open-cell nanoporous materials, unique in terms of low density, low thermal conductivity, low dielectric constants and high acoustic attenuation. Those exceptional properties stem from their complex hierarchical solid framework (agglomerates of porous, fractal secondary nanoparticles), but they also come at a cost: low mechanical strength. This issue has been resolved by crosslinking silica aerogels with organic polymers. The crosslinking polymer has been assumed to form a conformal coating on the surface of the skeletal framework by covalent bridging elementary building blocks. However, "assuming" is not enough: for correlating nanostructure with bulk material properties, it is important to know the exact location of the polymer on the aerogel backbone. For that investigation, we synthesized a new norbornene derivative of triethoxysilane (Si-NAD) that can be attached to skeletal silica nanoparticles. Those norbornene-modified silica aerogels were crosslinked with polynorbornene by ring opening metathesis polymerization (ROMP). The detailed correlation between nanostructure and mechanical strength was probed with a wide array of characterization methods ranging from molecular to bulk through nano. Subsequently, it was reasoned that since the polymer dominates the exceptional mechanical properties of polymer crosslinked aerogels, purely organic aerogels with the same nanostructure and interparticle connectivity should behave similarly. That was explored and confirmed by: (a) synthesis of a difunctional nadimide monomer (bis-NAD), and preparation of robust polyimide aerogels by ROMP of its norbornene end-caps; and, (b) synthesis of dimensionally stable ROMP-derived polydicyclopentadiene aerogels by grafting the nanostructure with polymethylmethacrylate (PMMA) via free radical chemistry.

  7. Oxidation of gaseous and volatile hydrocarbons by selected alkene-utilizing bacteria. [Mycobacterium; Nocardia

    SciTech Connect

    van Ginkel, C.G.; Welten, H.G.J.; de Bont, J.A.M.

    1987-12-01

    Eleven strains of alkene-utilizing bacteria belonging to the genera Mycobacterium, Nocardia, and Xanthobacter were tested for their ability to grow with C/sub 1/ to C/sub 6/ alkanes, C/sub 2/ to C/sub 6/ alkenes, alkadienes, and monoterpenes furnished individually as sole sources of carbon and energy in a mineral salts medium. A limited number of alkenes and alkanes supported growth of the bacteria; some bacteria were unable to grow on any of the saturated hydrocarbons tested. Monoterpenes were frequently used as carbon and energy sources by alkene-utilizing bacteria belonging to the genera Mycobacterium and Nocardia. Washed cell suspensions of alkene-grown bacteria attack the whole range of alkenes tested, whereas only three strains were able to oxidize alkanes as well. The alkenes tested were oxidized either to water and carbon dioxide or to epoxyalkanes. Few epoxides accumulated in stoichiometric amounts from the corresponding alkenes, because most epoxides formed were further converted to other compounds like alkanediols.

  8. 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

  9. 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. PMID:27490333

  10. 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.

  11. 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

  12. Nobel Prize in Chemistry. Development of the Olefin Metathesis Method in Organic Synthesis

    NASA Astrophysics Data System (ADS)

    Casey, Charles P.

    2006-02-01

    The 2005 Nobel Prize in Chemistry was awarded to Yves Chauvin of the Institut Français du Pétrole, Robert H. Grubbs of CalTech, and Richard R. Schrock of MIT "for development of the metathesis method in organic synthesis". The discoveries of the laureates provided a chemical reaction now used daily in the chemical industry for the efficient and more environmentally friendly production of important pharmaceuticals, fuels, synthetic fibers, and many other products. This article tells the story of how olefin metathesis became a truly useful synthetic transformation and a triumph for mechanistic chemistry, and illustrates the importance of fundamental research. See JCE Featured Molecules .

  13. Active low-valent niobium catalysts from NbCl5 and hydrosilanes for selective intermolecular cycloadditions.

    PubMed

    Satoh, Yasushi; Obora, Yasushi

    2011-10-21

    An active niobium catalyst was developed via a simple and nontoxic reduction method from NbCl(5)/hydrosilane and utilized for the selective [2 + 2 + 2] cycloaddition reaction of terminal alkynes and alkenes/α,ω-dienes, to give 1,3-cyclohexadiene derivatives in high yields with excellent chemo- and regioselectivity. PMID:21919436

  14. Capsule-controlled selectivity of a rhodium hydroformylation catalyst

    NASA Astrophysics Data System (ADS)

    Bocokić, Vladica; Kalkan, Ayfer; Lutz, Martin; Spek, Anthony L.; Gryko, Daniel T.; Reek, Joost N. H.

    2013-10-01

    Chemical processes proceed much faster and more selectively in the presence of appropriate catalysts, and as such the field of catalysis is of key importance for the chemical industry, especially in light of sustainable chemistry. Enzymes, the natural catalysts, are generally orders of magnitude more selective than synthetic catalysts and a major difference is that they take advantage of well-defined cavities around the active site to steer the selectivity of a reaction via the second coordination sphere. Here we demonstrate that such a strategy also applies for a rhodium catalyst; when used in the hydroformylation of internal alkenes, the selectivity of the product formed is steered solely by changing the cavity surrounding the metal complex. Detailed studies reveal that the origin of the capsule-controlled selectivity is the capsule reorganization energy, that is, the high energy required to accommodate the hydride migration transition state, which leads to the minor product.

  15. Pressure-induced metathesis reaction to sequester Cs.

    PubMed

    Im, Junhyuck; Seoung, Donghoon; Lee, Seung Yeop; Blom, Douglas A; Vogt, Thomas; Kao, Chi-Chang; Lee, Yongjae

    2015-01-01

    We report here a pressure-driven metathesis reaction where Ag-exchanged natrolite (Ag16Al16Si24O80·16H2O, Ag-NAT) is pressurized in an aqueous CsI solution, resulting in the exchange of Ag(+) by Cs(+) in the natrolite framework forming Cs16Al16Si24O80·16H2O (Cs-NAT-I) and, above 0.5 GPa, its high-pressure polymorph (Cs-NAT-II). During the initial cation exchange, the precipitation of AgI occurs. Additional pressure and heat at 2 GPa and 160 °C transforms Cs-NAT-II to a pollucite-related, highly dense, and water-free triclinic phase with nominal composition CsAlSi2O6. At ambient temperature after pressure release, the Cs remains sequestered in a now monoclinic pollucite phase at close to 40 wt % and a favorably low Cs leaching rate under back-exchange conditions. This process thus efficiently combines the pressure-driven separation of Cs and I at ambient temperature with the subsequent sequestration of Cs under moderate pressures and temperatures in its preferred waste form suitable for long-term storage at ambient conditions. The zeolite pollucite CsAlSi2O6·H2O has been identified as a potential host material for nuclear waste remediation of anthropogenic (137)Cs due to its chemical and thermal stability, low leaching rate, and the large amount of Cs it can contain. The new water-free pollucite phase we characterize during our process will not display radiolysis of water during longterm storage while maintaining the Cs content and low leaching rate. PMID:25515673

  16. Reversible Alkene Insertion into the Pd–N Bond of Pd(II)-Sulfonamidates and Implications for Catalytic Amidation Reactions

    PubMed Central

    White, Paul B.; Stahl, Shannon S.

    2011-01-01

    Alkene insertion into Pd–N bonds is a key step in Pd-catalyzed oxidative amidation of alkenes. A series of well-defined Pd(II)-sulfonamidate complexes have been prepared and shown to react via insertion of a tethered alkene. The Pd–amidate and resulting Pd–alkyl species have been crystallographically characterized. The alkene insertion reaction is found to be reversible, but complete conversion to oxidative amination products is observed in the presence of O2. Electronic-effect studies reveal that alkene insertion into the Pd–N bond is favored kinetically and thermodynamically with electron-rich amidates. PMID:22007610

  17. Rh-Catalyzed Intermolecular Syn-Carboamination of Alkenes via a Transient Directing Group

    PubMed Central

    Piou, Tiffany; Rovis, Tomislav

    2015-01-01

    Alkenes are the most ubiquitous pro-chiral functional groups accessible to synthetic chemists. For this reason, difunctionalization reactions of alkenes are particularly important, as they can be used to access highly complex molecular architectures.1,2 Stereoselective oxidation reactions, including dihydroxylation, aminohydroxylation and halogenation reactions,3,4,5,6 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. In this manuscript, we describe the Rh(III)-catalyzed syn carboamination of alkenes initiated by a C–H activation event that uses enoxyphthalimides as the source of the carbon and the nitrogen functionalities. The reaction methodology allows for the stereospecific formation of one C–C and one C–N bond across an alkene in a fully intermolecular sense, which is unprecedented. The reaction design involves the in situ generation of a bidentate directing group and the use of a novel cyclopentadienyl ligand to control the reactivity of Rh(III). The results provide a new route to functionalized alkenes and are expected to lead to the more convergent and stereoselective assembly of amine-containing acyclic molecules. PMID:26503048

  18. 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. PMID:26503048

  19. Iron Fischer-Tropsch catalysis: Properties of an ultrafine iron oxide catalyst

    SciTech Connect

    Xu, Liguang; Bao, Shiqi; O'Brien, R.; Houpt, D.; Davis, B.H.

    1992-01-01

    A commercial Fe oxide with a particle size of 3 nm is now available. The FT requires considerable time on stream before steady state conditions are attained. Since it is desirable to obtain FT data for the smaller ultrafine Fe oxide catalysts at larger times on steam, data for operation up to 6 months were collected using slurry phase. Results show that the ultrafine Fe oxide maintain catalytic activity for a 150-day operating period. Addition of 0.5% K increased the activity; after 56 days, the activity had declined to and below that of unpromoted catalyst. Neither the unpromoted nor K-promoted catalyst exhibited good selectivity for alkenes.

  20. Omega-functionalized fatty acids, alcohols, and ethers via olefin metathesis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Methyl 17-hydroxy stearate was converted to methyl octadec-16-enoate using copper sulfate adsorbed on silica gel. This compound, possessing unsaturation at the opposite end of the chain from the carboxylate, served as a useful substrate for the olefin metathesis reaction. As a result, several fatt...

  1. Enantioselective Synthesis of Guaianolides in the Osmitopsin Family by Domino Metathesis.

    PubMed

    Barthel, André; Kaden, Felix; Jäger, Anne; Metz, Peter

    2016-07-01

    Relay metathesis enabled an improved access from (S)-citronellal to the marine trisnorguaiane (-)-clavukerin A. This hydroazulene was applied as an advantageously functionalized building block for the asymmetric synthesis of the sesquiterpene lactone osmitopsin and the proposed structure of 4,5-epoxyosmitopsin using a chemo-, regio-, and diastereoselective diepoxide opening as the key step. PMID:27333451

  2. “Click” and Olefin Metathesis Chemistry in Water at Room Temperature Enabled by Biodegradable Micelles

    PubMed Central

    Lipshutz, Bruce H.; Bošković, Zarko; Crowe, Christopher S.; Davis, Victoria K.; Whittemore, Hannah C.; Vosburg, David A.; Wenzel, Anna G.

    2013-01-01

    The two laboratory reactions focus on teaching several concepts associated with green chemistry. Each uses a commercial, nontoxic, and biodegradable surfactant, TPGS-750-M, to promote organic reactions within the lipophilic cores of nanoscale micelles in water. These experiments are based on work by K. Barry Sharpless (an azide–alkyne “click” reaction) and Robert Grubbs (an olefin cross-metathesis reaction); both are suitable for an undergraduate organic laboratory. The copper-catalyzed azide–alkyne [3+2] cycloaddition of benzyl azide and 4-tolylacetylene is very rapid: the triazole product is readily isolated by filtration and is characterized by thin-layer chromatography and melting point analysis. The ruthenium-catalyzed olefin cross-metathesis reaction of benzyl acrylate with 1-hexene is readily monitored by thin-layer chromatography and gas chromatography. The metathesis experiment comparatively evaluates the efficacy of a TPGS-750-M/water medium relative to a traditional reaction performed in dichloromethane (a common solvent used for olefin metathesis). PMID:24324282

  3. Synthesis of the Caeliferins, elicitors of plant immune responses: accessing Lipophilic natural products via cross metathesis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We report a cross metathesis- (CM-) based syn-thesis of the caeliferins, a family of sulfooxy fatty acids that elicit plant immune responses. Unexpectedly, detailed NMR-spectroscopic and mass spectrometric analyses of CM reaction mixtures revealed extensive isomerization and homologation of starting...

  4. The Acquisition of Consonant Feature Sequences: Harmony, Metathesis, and Deletion Patterns in Phonological Development

    ERIC Educational Resources Information Center

    Gerlach, Sharon Ruth

    2010-01-01

    This dissertation examines three processes affecting consonants in child speech: harmony (long-distance assimilation) involving major place features as in "coat" [kouk]; long-distance metathesis as in "cup" [p[wedge]k]; and initial consonant deletion as in "fish" [is]. These processes are unattested in adult phonology, leading to proposals for…

  5. Design and synthesis of novel bis-annulated caged polycycles via ring-closing metathesis: pushpakenediol

    PubMed Central

    Dipak, Mirtunjay Kumar

    2014-01-01

    Summary Intricate caged molecular frameworks are assembled by an atom economical process via a Diels–Alder (DA) reaction, a Claisen rearrangement, a ring-closing metathesis (RCM) and an alkenyl Grignard addition. The introduction of olefinic moieties in the pentacycloundecane (PCUD) framework at appropriate positions followed by RCM led to the formation of novel heptacyclic cage systems. PMID:25550729

  6. 2005 Nobel Prize in Chemistry: Development of the Olefin Metathesis Method in Organic Synthesis

    ERIC Educational Resources Information Center

    Casey, Charles P.

    2006-01-01

    The 2005 Nobel Prize in Chemistry was awarded "for the development of the metathesis method in organic synthesis". The discoveries of the laureates provided a chemical reaction used daily in the chemical industry for the efficient and more environmentally friendly production of important pharmaceuticals, fuels, synthetic fibers, and many other…

  7. Catalytic enantioselective synthesis of naturally occurring butenolides via hetero-allylic alkylation and ring closing metathesis.

    PubMed

    Mao, Bin; Geurts, Koen; Fañanás-Mastral, Martín; van Zijl, Anthoni W; Fletcher, Stephen P; Minnaard, Adriaan J; Feringa, Ben L

    2011-03-01

    An efficient catalytic asymmetric synthesis of chiral γ-butenolides was developed based on the hetero-allylic asymmetric alkylation (h-AAA) in combination with ring closing metathesis (RCM). The synthetic potential of the h-AAA-RCM protocol was illustrated with the facile synthesis of (-)-whiskey lactone, (-)-cognac lactone, (-)-nephrosteranic acid, and (-)-roccellaric acid. PMID:21268603

  8. First preparation of low band gap fulvene-modified polynorbornene via ring-opening metathesis polymerization.

    PubMed

    Godman, Nicholas P; Balaich, Gary J; Iacono, Scott T

    2016-04-18

    New polymers containing intact pendant-fulvene moieties have been successfully prepared from 1,3-phenyl-6-norbornenylfulvene via ring-opening metathesis polymerization (ROMP). The prepared polyfulvenes have unique electrochemical and photophysical properties which make them interesting candidates for light harvesting materials. PMID:26980553

  9. 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

  10. 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

  11. 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. PMID:24248518

  12. Slurry phase Fischer-Tropsch synthesis: Cobalt plus a water-gas shift catalyst. [Quarterly] report, April 1, 1990--June 30, 1990

    SciTech Connect

    Yates, I.C.; Satterfield, C.N.

    1990-12-31

    Experiments on cobalt-catalyzed reactions of light 1-alkenes added to synthesis gas were performed. Data have been collected at 220C, 0.45 to 1.48 MPa and a synthesis gas flow rate between 0.015 and 0.030 Nl/(gcat{center_dot}min) with H{sub 2}/CO of 1.45 to 2.25. Ethylene, propene, and butene were added to synthesis gas feed from 0.5 to 1.2 mole% of total feed. For each material balance in which 1-alkenes were added, a material balance was performed at similar process conditions without 1-alkenes added, as ``base case``. Material balances without added 1-alkenes were also repeated to verify of catalyst selectivity stability. 49 material balances were performed during a single run lasting over 2,500 hours-on-stream. The hydrocarbon data have been completely analyzed; data correlations are still being made. Since C{sub 3}/C{sub 1} ratios by ethene addition, C{sub 4}/C{sub 1} ratios by propene addition, and C{sub 5}/C{sub 1} ratios by 1-butene addition, it appears that 1-alkenes may incorporate into growing chains on the surface of the catalyst. Further evidence for incorporation can be seen by comparing selectivity to n-alcohol one carbon number higher than added 1-alkene. Yield of this n-alcohol increases when alkenes are present. Sensitivity of hydrocarbon distribution to process variables seems to be greater on Co than on Fe catalysts.

  13. Slurry phase Fischer-Tropsch synthesis: Cobalt plus a water-gas shift catalyst

    SciTech Connect

    Yates, I.C.; Satterfield, C.N.

    1988-01-01

    This report details experiments performed on three different copper-based catalysts: Cu/Cr[sub 2]O[sub 3], Cu/MnO/Cr[sub 2]O[sub 3] and Cu/ZnO/Al[sub 2]O[sub 3]. Of these three catalysts, the Cu/ZnO/Al[sub 2]O[sub 3] exhibits the greatest stability when slurried in octacosane. More than 1000 hours-on-stream indicate that the catalyst activity is not detrimentally affected by high pressure, high H[sub 2]/CO ratio, or the presence of alkenes. All of these are necessary stability characteristics for the water-gas shift catalyst, if it is to be used in combination with a cobalt Fischer-Tropsch catalyst. A review of documented reduction procedures for cobalt-based Fischer-Tropsch catalysts is presented.

  14. Shell Higher Olefins Process.

    ERIC Educational Resources Information Center

    Lutz, E. F.

    1986-01-01

    Shows how olefin isomerization and the exotic olefin metathesis reaction can be harnessed in industrial processes. Indicates that the Shell Higher Olefins Process makes use of organometallic catalysts to manufacture alpha-olefins and internal carbon-11 through carbon-14 alkenes in a flexible fashion that can be adjusted to market needs. (JN)

  15. 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

  16. Development of heterogeneous catalysts for hydroformylation of 1-hexene in supercritical carbon dioxide

    NASA Astrophysics Data System (ADS)

    Marteel, Anne Eugenie

    The hydroformylation of alkenes is a major commercial process used for the production of oxygenated organic compounds. When the hydroformylation reaction is performed using a homogeneous catalyst, an organic or aqueous solvent is employed and a significant effort must be expended to recover the catalyst so it can be recycled. The hydroformylation of long-chain alkenes using homogeneous catalysts in aqueous solution is compromised because of the low-solubility of C5 alkenes and above. Development of a selective heterogeneous catalyst would allow simplification of the process design in an integrated system that minimizes waste generation. Recent studies have shown that a supercritical fluid may be used as a solvent for hydroformylation reactions. The use of carbon dioxide as a reaction solvent offers optimal environmental performance because it is non-toxic, non-flammable and plentiful, and presents advantages for ease of product separation. In particular, we have considered the conversion of 1-hexene to heptanal using rhodium-phosphine catalysts tethered to supports insoluble in supercritical carbon dioxide to demonstrate the advantages and understand the limitations of a solid-catalyzed process. One of the limitations of supported catalysts is the inability to control product selectivity. To remedy this problem, we have developed tethered rhodium-phosphine catalysts with modified silica and controlled-pore size MCM-41 and MCM-20 supports that provide improved selectivity and conversion relative to their nonporous equivalents. Platinum and palladium catalysts analogous to those of rhodium were also investigated. The synthesis and characterization of the rhodium, platinum and palladium complexes and evaluation of their catalytic activity and selectivity for hydroformylation in supercritical carbon dioxide is described in this dissertation.

  17. Structure-activity relationships of ruthenium Fischer-Tropsch catalysts (metal particle size effects)

    SciTech Connect

    White, M.W. Jr.

    1989-01-01

    In the group VIII transition metal catalytic conversion of hydrogen/carbon monoxide mixtures to hydrocarbons, it is known that certain catalysts catalyze the production of a narrow boiling range (C{sub 6}-C{sub 12}) product which does not fit the traditional Anderson-Schulz-Flory (ASF) chain growth model. Among the proposed explanations for this selectivity is one based on control of hydrocarbon chain propagation by metal particle size. The focus of this work was to study the effect of metal particle size on catalytic activity for the F-T synthesis. The silica-supported and unsupported Ru catalysts catalyzed the production of a hydrocarbon product which followed the ASF chain growth model and which consisted primarily of n-aklanes and linear 1-alkenes. An equation was derived relating the weight fraction of alkenes and alkanes to the residence times of the alkenes in the reactor and this equation produced a reasonable fit to the experimental data. It was observed that hydrocarbon, CO{sub 2} and CH{sub 4} production increased with time apparently reaching steady state after {approximately}200H. It was also found that increasing reactant gas space velocities (SHSV's) increased the steady state turnover numbers for hydrocarbon, CO{sub 2} and CH{sub 4} production, while at the same time, the AFS probabilities of chain growth and alkene/alkane ratios remained effectively constant.

  18. Rapid ether and alcohol C-O bond hydrogenolysis catalyzed by tandem high-valent metal triflate + supported Pd catalysts.

    PubMed

    Li, Zhi; Assary, Rajeev S; Atesin, Abdurrahman C; Curtiss, Larry A; Marks, Tobin J

    2014-01-01

    The thermodynamically leveraged conversion of ethers and alcohols to saturated hydrocarbons is achieved efficiently with low loadings of homogeneous M(OTf)n + heterogeneous Pd tandem catalysts (M = transition metal; OTf = triflate; n = 4). For example, Hf(OTf)4 mediates rapid endothermic ether ⇌ alcohol and alcohol ⇌ alkene equilibria, while Pd/C catalyzes the subsequent, exothermic alkene hydrogenation. The relative C-O cleavage rates scale as 3° > 2° > 1°. The reaction scope extends to efficient conversion of biomass-derived ethers, such as THF derivatives, to the corresponding alkanes. PMID:24354599

  19. Oxydifluoromethylation of Alkenes by Photoredox Catalysis: Simple Synthesis of CF2H-Containing Alcohols.

    PubMed

    Arai, Yusuke; Tomita, Ren; Ando, Gaku; Koike, Takashi; Akita, Munetaka

    2016-01-22

    We have developed a novel and simple protocol for the direct incorporation of a difluoromethyl (CF2 H) group into alkenes by visible-light-driven photoredox catalysis. The use of fac-[Ir(ppy)3] (ppy=2-pyridylphenyl) photocatalyst and shelf-stable Hu's reagent, N-tosyl-S-difluoromethyl-S-phenylsulfoximine, as a CF2 H source is the key to success. The well-designed photoredox system achieves synthesis of not only β-CF2 H-substituted alcohols but also ethers and an ester from alkenes through solvolytic processes. The present method allows a single-step and regioselective formation of C(sp(3))-CF2 H and C(sp(3))-O bonds from C=C moiety in alkenes, such as hydroxydifluoromethylation, regardless of terminal or internal alkenes. Moreover, this methodology tolerates a variety of functional groups. PMID:26639021

  20. Mixed regiospecificity compromises alkene synthesis by a cytochrome P450 peroxygenase from Methylobacterium populi.

    PubMed

    Amaya, Jose A; Rutland, Cooper D; Makris, Thomas M

    2016-05-01

    Intensive interest has focused on enzymes that are capable of synthesizing hydrocarbons, alkenes and alkanes, for sustainable fuel production. A recently described cytochrome P450 (OleTJE) from the CYP152 family catalyzes an unusual carbon-carbon scission reaction, transforming Cn fatty acids to Cn-1 1-alkenes. Here, we show that a second CYP152, CYP-MP from Methylobacterium populi ATCC BAA 705, also catalyzes oxidative substrate decarboxylation. Alkene production is accompanied with the production of fatty alcohol products, underscoring the mechanistic similarity of the decarboxylation reaction with canonical P450 monooxygenation chemistry. The branchpoint of these two chemistries, and regiospecificity of oxidation products, is strongly chain length dependent, suggesting an importance of substrate coordination for regulating alkene production. PMID:26965726

  1. Oxydifluoromethylation of Alkenes by Photoredox Catalysis: Simple Synthesis of CF2H‐Containing Alcohols

    PubMed Central

    Arai, Yusuke; Tomita, Ren; Ando, Gaku

    2015-01-01

    Abstract We have developed a novel and simple protocol for the direct incorporation of a difluoromethyl (CF2H) group into alkenes by visible‐light‐driven photoredox catalysis. The use of fac‐[Ir(ppy)3] (ppy=2‐pyridylphenyl) photocatalyst and shelf‐stable Hu's reagent, N‐tosyl‐S‐difluoromethyl‐S‐phenylsulfoximine, as a CF2H source is the key to success. The well‐designed photoredox system achieves synthesis of not only β‐CF2H‐substituted alcohols but also ethers and an ester from alkenes through solvolytic processes. The present method allows a single‐step and regioselective formation of C(sp3)–CF2H and C(sp3)−O bonds from C=C moiety in alkenes, such as hydroxydifluoromethylation, regardless of terminal or internal alkenes. Moreover, this methodology tolerates a variety of functional groups. PMID:26639021

  2. Peroxodisulfate-mediated selenoamination of alkenes yielding amidoselenide-containing sulfamides and azoles.

    PubMed

    Sun, Kai; Wang, Xin; Lv, Yunhe; Li, Gang; Jiao, Hezhen; Dai, Changwei; Li, Yangyang; Zhang, Chong; Liu, Lin

    2016-06-28

    A new protocol for C-Se and C-N bond formation by the direct difunctionalization of alkenes is reported. The protocol is operationally simple, has a wide substrate scope, and uses readily available amino sources. This reaction represents a significant addition to the limited number of intermolecular selenide difunctionalization reactions of alkenes and would find practical application in the synthesis of nitrogen- and selenium-containing molecules. PMID:27312114

  3. 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.

  4. Iron-Catalyzed Regioselective Transfer Hydrogenative Couplings of Unactivated Aldehydes with Simple Alkenes.

    PubMed

    Zheng, Yan-Long; Liu, Yan-Yao; Wu, Yi-Mei; Wang, Yin-Xia; Lin, Yu-Tong; Ye, Mengchun

    2016-05-17

    An FeBr3 -catalyzed reductive coupling of various aldehydes with alkenes that proceeds through a direct hydride transfer pathway has been developed. With (i) PrOH as the hydrogen donor under mild conditions, previously challenging coupling reactions of unactivated alkyl and aryl aldehydes with simple alkenes, such as styrene derivatives and α-olefins, proceeded smoothly to furnish a diverse range of functionalized alcohols with complete linear regioselectivity. PMID:27072872

  5. 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

  6. Bimetallic Catalysts.

    ERIC Educational Resources Information Center

    Sinfelt, John H.

    1985-01-01

    Chemical reaction rates can be controlled by varying composition of miniscule clusters of metal atoms. These bimetallic catalysts have had major impact on petroleum refining, where work has involved heterogeneous catalysis (reacting molecules in a phase separate from catalyst.) Experimentation involving hydrocarbon reactions, catalytic…

  7. Oxyhydrochlorination catalyst

    DOEpatents

    Taylor, Charles E.; Noceti, Richard P.

    1992-01-01

    An improved catalyst and method for the oxyhydrochlorination of methane is disclosed. The catalyst includes a pyrogenic porous support on which is layered as active material, cobalt chloride in major proportion, and minor proportions of an alkali metal chloride and of a rare earth chloride. On contact of the catalyst with a gas flow of methane, HCl and oxygen, more than 60% of the methane is converted and of that converted more than 40% occurs as monochloromethane. Advantageously, the monochloromethane can be used to produce gasoline boiling range hydrocarbons with the recycle of HCl for further reaction. This catalyst is also of value for the production of formic acid as are analogous catalysts with lead, silver or nickel chlorides substituted for the cobalt chloride.

  8. Homogeneous and Supported Niobium Catalysts as Lewis Acid and Radical Catalysts

    SciTech Connect

    Wayne Tikkanen

    2006-12-31

    The synthesis of tetrachlorotetraphenylcyclopentadienyl group 5 metal complexes has been accomplished through two routes, one a salt metathesis with lithiumtetraphenylcyclopentadiende and the other, reaction with trimethyltintetraphenylcyclopentadiene. The reactants and products have been characterized by {sup 1}H and {sup 13}C({sup 1}H) NMR spectroscopy. The niobium complex promotes the silylcyanation of butyraldehyde. The grafting of metal complexes to silica gel surfaces has been accomplished using tetrakisdimethylamidozirconium as the metal precursor. The most homogeneous binding as determined by CP-MAS {sup 13}C NMR and infrared spectroscopy was obtained with drying at 500 C at 3 mtorr vacuum. The remaining amido groups can be replaced by reaction with alcohols to generate surface bound metal alkoxides. These bound catalysts promote silylcyanation of aryl aldehydes and can be reused three times with no loss of activity.

  9. Amplification of surface-initiated ring-opening metathesis polymerization of 5-(perfluoro-n-alkyl)norbornenes by macroinitiation.

    PubMed

    Escobar, Carlos A; Harl, Robert R; Maxwell, Kathryn E; Mahfuz, Nur N; Rogers, Bridget R; Jennings, G Kane

    2013-10-01

    This article reports the enhanced rate of the surface-initiated polymerization (SIP) of 5-(perfluoro-n-alkyl)norbornenes (NBFn) by combining two SIP techniques, namely surface-initiated atom-transfer polymerization (SI-ATRP) to grow a macroinitiator and surface-initiated ring-opening metathesis polymerization (SI-ROMP) to produce the final coating. This polymerization approach promotes the rapid growth of dense partially fluorinated coatings that are highly hydrophobic and oleophobic and yield thicknesses from 4-12 μm. Specifically, the growth rate and the limiting thickness of pNBFn with different side chain lengths (n = 4, 6, 8, and 10) at various monomer concentrations and temperatures are evaluated through two approaches: growing the polymer from an initiator-terminated monolayer (control) or from a modified poly(2-hydroxyethyl methacrylate) (PHEMA) macroinitiator. X-ray photoelectron spectroscopy (XPS) analysis shows that 38% of the hydroxyl termini in the macroinitiator react with a norbornenyl diacid chloride (NBDAC) molecule, and 7% of such anchored norbornenyl groups react with a catalyst molecule. The kinetic data have been modeled to determine the propagation velocity and the termination rate constant. The PHEMA macroinitiator provides thicker films and faster growth as compared to the monolayer, achieving a 12 μm thick coating of pNBF8 in 15 min. Increasing the monomer side chain length, n, from 4 to 10 improves the growth rate and the limiting polymer thickness. Performing the polymerization process at higher temperature increases the growth rate and the limiting thickness as evidenced by an increase in the film growth rate constant. Arrhenius plots show that the reactions involved in the macroinitiation process exhibit lower activation energies than those formed from a monolayer. Electrochemical impedance spectroscopy reveals that the films exhibit resistance against ion transport in excess of 1 × 10(10) Ω·cm(2). PMID:24024903

  10. Catalytic Scanning Probe Nanolithography (cSPL): Control of the AFM Parameters in Order to Achieve Sub-100-nm Spatially Resolved Epoxidation of Alkenes Grafted onto a Surface.

    PubMed

    Mesquita, Vincent; Botton, Julien; Valyaev, Dmitry A; François, Cyril; Patrone, Lionel; Balaban, Teodor Silviu; Abel, Mathieu; Parrain, Jean-Luc; Chuzel, Olivier; Clair, Sylvain

    2016-04-26

    Scanning probe lithography (SPL) appears to be a reliable alternative to the use of masks in traditional lithography techniques as it offers the possibility of directly producing specific chemical functionalities with nanoscale spatial control. We have recently extend the range of applications of catalytic SPL (cSPL) by introducing a homogeneous catalyst immobilized on the apex of a scanning probe. Here we investigate the importance of atomic force microscopy (AFM) physical parameters (applied force, writing speed, and interline distance) on the resultant chemical activity in this cSPL methodology through the direct topographic observation of nanostructured surfaces. Indeed, an alkene-terminated self-assembled monolayer (alkene-SAM) on a silicon wafer was locally epoxidized using a scanning probe tip with a covalently grafted manganese complex bearing the 1,4,7-triazacyclononane macrocycle as the ligand. In a post-transformation process, N-octylpiperazine was covalently grafted to the surface via a selective nucleophilic ring-opening reaction. With this procedure, we could write various patterns on the surface with high spatial control. The catalytic AFM probe thus appears to be very robust because a total area close to 500 μm(2) was patterned without any noticeable loss of catalytic activity. Finally, this methodology allowed us to reach a lower lateral line resolution down to 40 nm, thus being competitive and complementary to the other nanolithographical techniques for the nanostructuration of surfaces. PMID:27027411

  11. Genes Involved in Long-Chain Alkene Biosynthesis in Micrococcus luteus▿

    PubMed Central

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

    2010-01-01

    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 4 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 Escherichia coli strain resulted in production of long-chain alkenes, predominantly 27:3 and 29:3 (no. carbon atoms: no. C 000000000000 000000000000 000000000000 111111111111 000000000000 111111111111 000000000000 000000000000 000000000000 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-coenzyme A (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 [acyl carrier protein]) 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

  12. Polymerization catalyst

    SciTech Connect

    Graves, V.

    1987-05-12

    A process is described for polymerizing at least one alpha olefin under conditions characteristic of Ziegler polymerization wherein the polymerization is conducted in the presence of a catalyst system which comprises: a supported catalyst prepared under anhydrous conditions by the sequential steps of: preparing a slurry of inert particulate support material; adding to the slurry a solution of an organomagnesium compound; adding to the slurry and reacting a solution of a zirconium halide compound, hafnium compound or mixtures thereof; adding to the slurry and reacting a halogenator; adding to the slurry and reacting a tetravalent titanium halide compound; and recovering solid catalyst.

  13. Polymerization catalyst

    SciTech Connect

    Graves, V.

    1986-10-21

    A process is described for polymerizing at least one alpha-olefin under conditions characteristic of Ziegler polymerization wherein the polymerization is conducted in the presence of a catalyst comprising: a supported catalyst prepared under anhydrous conditions by the steps of: (1) sequentially; (a) preparing a slurry of inert particulate support material; (b) adding to the slurry a solution of an organomagnesium compound; (c) adding to the slurry and reacting a solution of zirconium compound; and (2) thereafter; (d) adding to the slurry and reacting a halogenator; (e) adding to the slurry and reacting a tetravalent titanium compound; (f) recovering solid catalyst; and an organoaluminum compound.

  14. 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. PMID:27026261

  15. Iron-mediated oxidative C-H coupling of arenes and alkenes directed by sulfur: an expedient route to dihydrobenzofurans.

    PubMed

    Cavanagh, Craig W; Aukland, Miles H; Laurent, Quentin; Hennessy, Alan; Procter, David J

    2016-06-21

    A novel route to medicinally-relevant dihydrobenzofurans utilises a sulfur-directed C-H ortho-coupling of arenes and unactivated terminal alkenes mediated by iron, and a palladium-catalysed deallylation/heterocyclisation sequence. The iron-mediated coupling affords linear products of alkene chloroarylation in good yield and with complete regioselectivity. The coupling likely proceeds by redox-activation of the arene partner by iron(iii) and alkene addition to the resultant radical cation. PMID:27198174

  16. Reaction Mechanism of the Hydrogermylation/Hydrostannylation of Unactivated Alkenes with Two-Coordinate E(II) Hydrides (E=Ge, Sn): A Theoretical Study.

    PubMed

    Zhao, Lili; Hermann, Markus; Jones, Cameron; Frenking, Gernot

    2016-08-01

    Quantum chemical calculations using density functional theory with the TPSS+D3(BJ) and M06-2X+D3(ABC) functionals have been carried out to understand the mechanisms of catalyst-free hydrogermylation/hydrostannylation reactions between the two-coordinate hydrido-tetrylenes :E(H)(L(+) ) (E=Ge or Sn, L(+) =N(Ar(+) )(SiiPr3 ); Ar(+) =C6 H2 {C(H)Ph2 }2 iPr-2,6,4) and a range of unactivated terminal (C2 H3 R, R=H, Ph, or tBu) and cyclic [(CH)2 (CH2 )2 (CH2 )n , n=1, 2, or 4] alkenes. The calculations suggest that the addition reactions of the germylenes and stannylenes to the cyclic and acyclic alkenes occur as one-step processes through formal [2+2] addition of the E-H fragment across the C-C π bond. The reactions have moderate barriers and are weakly exergonic. The steric bulk of the tetrylene amido groups has little influence on the activation barriers and on the reaction energies of the anti-Markovnikov pathway, but the Markovnikov addition is clearly disfavored by the size of the substituents. The addition of the tetrylenes to the cyclic alkenes is less exergonic than the addition to the terminal alkenes, which agrees with the experimentally observed reversibility of the former reactions. The hydrogermylation reactions have lower activation energies and are more exergonic than the stannylene addition. An energy decomposition analysis of the transition state for the hydrogermylation of cyclohexene shows that the reaction takes place with simultaneous formation of the Ge-C and (Ge)H-C' bonds. The dominant orbitals of the germylene are the σ-type lone pair MO of Ge, which serves as a donor orbital, and the vacant p(π) MO of Ge, which acts as acceptor orbital for the π* and π MOs of the olefin. Inspection of the transition states of some selected reactions suggests that the differences between the activation energies come from a delicate balance between the deformation energies of the interacting species and their interaction energies. PMID:27403941

  17. Cascade Metathesis Reactions for the Synthesis of Taxane and Isotaxane Derivatives.

    PubMed

    Ma, Cong; Letort, Aurélien; Aouzal, Rémi; Wilkes, Antonia; Maiti, Gourhari; Farrugia, Louis J; Ricard, Louis; Prunet, Joëlle

    2016-05-10

    Tricyclic isotaxane and taxane derivatives have been synthesized by a very efficient cascade ring-closing dienyne metathesis (RCDEYM) reaction, which formed the A and B rings in one operation. When the alkyne is present at C13 (with no neighboring gem-dimethyl group), the RCEDYM reaction leads to 14,15-isotaxanes 16 a,b and 18 b with the gem-dimethyl group on the A ring. If the alkyne is at the C11 position (and thus flanked by a gem-dimethyl group), RCEDYM reaction only proceeds in the presence of a trisubstituted olefin at C13, which disfavors the competing diene ring-closing metathesis reaction, to give the tricyclic core of Taxol 44. PMID:27062670

  18. Formal synthesis of optically active ingenol via ring-closing olefin metathesis.

    PubMed

    Watanabe, Kazushi; Suzuki, Yuto; Aoki, Kenta; Sakakura, Akira; Suenaga, Kiyotake; Kigoshi, Hideo

    2004-11-12

    The construction of strained carbon skeletons by ring-closing olefin metathesis (RCM) was investigated. With well-designed diene 4, RCM was found to be applicable to the formation of a highly strained inside-outside bicyclo[4.4.1]undecane skeleton of ingenol, a bioactive diterpenoid, and formal total synthesis of optically active ingenol (1) was achieved. The key features of this synthesis are construction of an A-ring by spirocyclization of the ketone with an allylic chloride unit, 26, and ring closure of a B-ring by olefin metathesis. Starting from Funk's keto ester 6, the key intermediate aldehyde 9 in Winkler's total synthesis was synthesized in eight steps in 12.5% overall yield. This strategy of direct cyclization of a strained inside-outside skeleton provided the first easy access to optically active ingenol. PMID:15527254

  19. 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.

  20. C-84 Selective Porphyrin Macrocycle with an Adaptable Cavity Constructed Through Alkyne Metathesis

    SciTech Connect

    Zhang, C. X.; Long, H.; Zhang, W.

    2012-06-21

    A bisporphyrin macrocycle was constructed from a porphyrin-based diyne monomer in one step through alkyne metathesis. The fullerene binding studies (C{sub 60}, C{sub 70} and C{sub 84}) showed the highest binding affinity of the macrocycle for C{sub 84}, which is in great contrast to its bisporphyrin four-armed cage analogue that showed the strongest binding with C{sub 70}.

  1. A General Approach to Sequence-Controlled Polymers Using Macrocyclic Ring Opening Metathesis Polymerization

    PubMed Central

    2015-01-01

    A new and general strategy for the synthesis of sequence-defined polymers is described that employs relay metathesis to promote the ring opening polymerization of unstrained macrocyclic structures. Central to this approach is the development of a small molecule “polymerization trigger” which when coupled with a diverse range of sequence-defined units allows for the controlled, directional synthesis of sequence controlled polymers. PMID:26053158

  2. Nitrene Metathesis and Catalytic Nitrene Transfer Promoted by Niobium Bis(imido) Complexes.

    PubMed

    Kriegel, Benjamin M; Bergman, Robert G; Arnold, John

    2016-01-13

    We report a metathesis reaction in which a nitrene fragment from an isocyanide ligand is exchanged with a nitrene fragment of an imido ligand in a series of niobium bis(imido) complexes. One of these bis(imido) complexes also promotes nitrene transfer to catalytically generate asymmetric dialkylcarbodiimides from azides and isocyanides in a process involving the Nb(V)/Nb(III) redox couple. PMID:26698833

  3. Iron Fischer-Tropsch catalysis: Properties of an ultrafine iron oxide catalyst. Quarterly progress report, July--September 1992

    SciTech Connect

    Xu, Liguang; Bao, Shiqi; O`Brien, R.; Houpt, D.; Davis, B.H.

    1992-12-31

    A commercial Fe oxide with a particle size of 3 nm is now available. The FT requires considerable time on stream before steady state conditions are attained. Since it is desirable to obtain FT data for the smaller ultrafine Fe oxide catalysts at larger times on steam, data for operation up to 6 months were collected using slurry phase. Results show that the ultrafine Fe oxide maintain catalytic activity for a 150-day operating period. Addition of 0.5% K increased the activity; after 56 days, the activity had declined to and below that of unpromoted catalyst. Neither the unpromoted nor K-promoted catalyst exhibited good selectivity for alkenes.

  4. Exploring the mechanism of Grignard metathesis polymerization of 3-alkylthiophenes.

    PubMed

    Bahri-Laleh, Naeimeh; Poater, Albert; Cavallo, Luigi; Mirmohammadi, Seyed Amin

    2014-10-28

    In this study we have investigated computationally the mechanism of polymerization of 2,5-dibromo 3-butylthiophene via the GRIM method, with the focus on the origin of the head to tail (HT) selectivity. To this end, first the Grignard reagent underwent oxidative addition to the monomer to afford the 2-bromo-5-chloromagnesio-3-butylthiophene (intermediate I1) or the 2-chloromagnesio 5-bromo-3-butylthiophene (intermediate I2) regioisomers. Then intermediates I1 and I2 were polymerized catalytically to a series of regiospecific poly-3-butylthiophenes using the commonly used Ni(dppp)Cl2 [dppp: 1,3-bis(diphenylphosphino) propane] and Pd(dppp)Cl2 catalysts. Due to the asymmetric nature of I1 and I2 that act as the active monomeric species, 6 coupling modes may occur. The whole energy profile of all modes has been studied by considering a three-stage mechanism, including coordination, transmetalation, and reductive elimination, to compare quantitatively the ability of so-called catalysts in selective coupling of desired isomers to produce regioregular poly-3-butylthiophene. Finally, to quantify the steric role of the dppp in regioselectivity, analysis of the buried volume in terms of steric maps was performed. PMID:25178627

  5. [Separation and purification of Al13 by chemical precipitation and metathesis].

    PubMed

    Li, Guo-Hong; Shi, Bao-You; Wang, Dong-Sheng; Cui, Ya-Li

    2007-02-01

    PACls with different concentrations were prepared by adding sodium carbonate powder into AlCl13 solution. Medium concentration and high Al13 content of PACl was chosen to carry out Al13 separation processes. The influences of SO4/Al molar ratio and the initial total Al concentration on the precipitation reactions of sulfate with different Al species were investigated. The factors influencing the metathesis reaction between solid Al13-SO4 and Ba(NO3)2 were evaluated. Results showed that high Al13 PACl could be obtained at the medium high concentration range of 0.4 - 0.6 mol/L, the optimum SO4/Al ratio was 0.6:1 for precipitation- separation of Al13, Al13 -SO4 precipitates were mostly consisted of tetrahedral crystals. During the metathesis reaction, Ba/SO4 molar ratio of 1:1 is the optimal value. Small range temperature variation and ultrasonic action had no marked influence on metathesis reaction rate and final Al13 concentration. Higher initial Ba(NO3)2 concentration could produce higher concentration Al13 accordingly. The purity of Al13 solution could be reached to 92.1% statistically. PMID:17489196

  6. Photo-oxidation catalysts

    DOEpatents

    Pitts, J. Roland; Liu, Ping; Smith, R. Davis

    2009-07-14

    Photo-oxidation catalysts and methods for cleaning a metal-based catalyst are disclosed. An exemplary catalyst system implementing a photo-oxidation catalyst may comprise a metal-based catalyst, and a photo-oxidation catalyst for cleaning the metal-based catalyst in the presence of light. The exposure to light enables the photo-oxidation catalyst to substantially oxidize absorbed contaminants and reduce accumulation of the contaminants on the metal-based catalyst. Applications are also disclosed.

  7. 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

  8. Oxidation catalysts comprising metal exchanged hexaaluminate wherein the metal is Sr, Pd, La, and/or Mn

    SciTech Connect

    Wickham, David; Cook, Ronald

    2008-10-28

    The present invention provides metal-exchanged hexaaluminate catalysts that exhibit good catalytic activity and/or stability at high temperatures for extended periods with retention of activity as combustion catalysts, and more generally as oxidation catalysts, that make them eminently suitable for use in methane combustion, particularly for use in natural gas fired gas turbines. The hexaaluminate catalysts of this invention are of particular interest for methane combustion processes for minimization of the generation of undesired levels (less than about 10 ppm) of NOx species. Metal exchanged hexaaluminate oxidation catalysts are also useful for oxidation of volatile organic compounds (VOC), particularly hydrocarbons. Metal exchanged hexaaluminate oxidation catalysts are further useful for partial oxidation, particularly at high temperatures, of reduced species, particularly hydrocarbons (alkanes and alkenes).

  9. Computational approaches to the determination of active site structures and reaction mechanisms in heterogeneous catalysts.

    PubMed

    Catlow, C R A; French, S A; Sokol, A A; Thomas, J M

    2005-04-15

    We apply quantum chemical methods to the study of active site structures and reaction mechanisms in mesoporous silica and metal oxide catalysts. Our approach is based on the use of both molecular cluster and embedded cluster (QM/MM) techniques, where the active site and molecular complex are described using density functional theory (DFT) and the embedding matrix simulated by shell model potentials. We consider three case studies: alkene epoxidation over the microporous TS-1 catalyst; methanol synthesis on ZnO and Cu/ZnO and C-H bond activation over Li-doped MgO. PMID:15901543

  10. Catalytic, asymmetric difluorination of alkenes to generate difluoromethylated stereocenters.

    PubMed

    Banik, Steven M; Medley, Jonathan William; Jacobsen, Eric N

    2016-07-01

    Difluoromethyl groups possess specific steric and electronic properties that invite their use as chemically inert surrogates of alcohols, thiols, and other polar functional groups important in a wide assortment of molecular recognition processes. We report here a method for the catalytic, asymmetric, migratory geminal difluorination of β-substituted styrenes to access a variety of products bearing difluoromethylated tertiary or quaternary stereocenters. The reaction uses commercially available reagents (m-chloroperbenzoic acid and hydrogen fluoride pyridine) and a simple chiral aryl iodide catalyst and is carried out readily on a gram scale. Substituent effects and temperature-dependent variations in enantioselectivity suggest that cation-π interactions play an important role in stereodifferentiation by the catalyst. PMID:27365443

  11. Rhodium catalysed hydroformylation of alkenes using highly fluorophilic phosphines.

    PubMed

    Adams, Dave J; Bennett, James A; Cole-Hamilton, David J; Hope, Eric G; Hopewell, Jonathan; Kight, Jo; Pogorzelec, Peter; Stuart, Alison M

    2005-12-21

    Highly fluorophilic phosphines incorporating at least one aromatic ring containing two directly attached perfluoroalkyl groups have been synthesised, their partition coefficients (organic phase : fluorous phase) measured and their electronic properties probed using (1)J(PtP) data for their trans-[PtCl(2)L(2)] complexes. These phosphines have been used as modifying ligands for the rhodium catalysed hydroformylation of 1-octene in perfluorocarbon solvents. Catalyst activity, regioselectivity and the levels of rhodium leaching to the product phase vary with the substitution patterns of the modifying ligands that do not correlate with the electronic properties or partition coefficients of these ligands, but can be interpreted in terms of differences in the resting states of the catalysts. PMID:16311639

  12. 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

  13. 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

  14. Chemoenzymatic Epoxidation of Alkenes and Reusability Study of the Phenylacetic Acid

    PubMed Central

    Abdulmalek, Emilia; Mizan, Hanis Nabillah; Abdul Rahman, Mohd. Basyaruddin; Basri, Mahiran; Salleh, Abu Bakar

    2014-01-01

    Here, we focused on a simple enzymatic epoxidation of alkenes using lipase and phenylacetic acid. The immobilised Candida antarctica lipase B, Novozym 435 was used to catalyse the formation of peroxy acid instantly from hydrogen peroxide (H2O2) and phenylacetic acid. The peroxy phenylacetic acid generated was then utilised directly for in situ oxidation of alkenes. A variety of alkenes were oxidised with this system, resulting in 75–99% yield of the respective epoxides. On the other hand, the phenylacetic acid was recovered from the reaction media and reused for more epoxidation. Interestingly, the waste phenylacetic acid had the ability to be reused for epoxidation of the 1-nonene to 1-nonene oxide, giving an excellent yield of 90%. PMID:24587751

  15. Subnanometer and nanometer catalysts, method for preparing size-selected catalysts

    DOEpatents

    Vajda, Stefan , Pellin, Michael J.; Elam, Jeffrey W.; Marshall, Christopher L.; Winans, Randall A.; Meiwes-Broer, Karl-Heinz

    2012-04-03

    Highly uniform cluster based nanocatalysts supported on technologically relevant supports were synthesized for reactions of top industrial relevance. The Pt-cluster based catalysts outperformed the very best reported ODHP catalyst in both activity (by up to two orders of magnitude higher turn-over frequencies) and in selectivity. The results clearly demonstrate that highly dispersed ultra-small Pt clusters precisely localized on high-surface area supports can lead to affordable new catalysts for highly efficient and economic propene production, including considerably simplified separation of the final product. The combined GISAXS-mass spectrometry provides an excellent tool to monitor the evolution of size and shape of nanocatalyst at action under realistic conditions. Also provided are sub-nanometer gold and sub-nanometer to few nm size-selected silver catalysts which possess size dependent tunable catalytic properties in the epoxidation of alkenes. Invented size-selected cluster deposition provides a unique tool to tune material properties by atom-by-atom fashion, which can be stabilized by protective overcoats.

  16. Subnanometer and nanometer catalysts, method for preparing size-selected catalysts

    DOEpatents

    Vajda, Stefan; Pellin, Michael J.; Elam, Jeffrey W.; Marshall, Christopher L.; Winans, Randall A.; Meiwes-Broer, Karl-Heinz

    2012-03-27

    Highly uniform cluster based nanocatalysts supported on technologically relevant supports were synthesized for reactions of top industrial relevance. The Pt-cluster based catalysts outperformed the very best reported ODHP catalyst in both activity (by up to two orders of magnitude higher turn-over frequencies) and in selectivity. The results clearly demonstrate that highly dispersed ultra-small Pt clusters precisely localized on high-surface area supports can lead to affordable new catalysts for highly efficient and economic propene production, including considerably simplified separation of the final product. The combined GISAXS-mass spectrometry provides an excellent tool to monitor the evolution of size and shape of nanocatalyst at action under realistic conditions. Also provided are sub-nanometer gold and sub-nanometer to few nm size-selected silver catalysts which possess size dependent tunable catalytic properties in the epoxidation of alkenes. Invented size-selected cluster deposition provides a unique tool to tune material properties by atom-by-atom fashion, which can be stabilized by protective overcoats.

  17. 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…

  18. Ammonium iodide-induced sulfonylation of alkenes with DMSO and water toward the synthesis of vinyl methyl sulfones.

    PubMed

    Gao, Xiaofang; Pan, Xiaojun; Gao, Jian; Huang, Huawen; Yuan, Gaoqing; Li, Yingwei

    2015-01-01

    A novel ammonium iodide-induced sulfonylation of alkenes with DMSO and water toward the synthesis of vinyl methyl sulfones is described. The process proceeded smoothly under metal-free conditions with high stereoselectivity and good functional group tolerance. The reaction mechanism was revealed to proceed through a domino reaction of oxidation and elimination after the radical addition to alkenes. PMID:25406694

  19. Phosphine-alkene ligand-mediated alkyl-alkyl and alkyl-halide elimination processes from palladium(II).

    PubMed

    Tuxworth, Luke; Baiget, Lise; Phanopoulos, Andreas; Metters, Owen J; Batsanov, Andrei S; Fox, Mark A; Howard, Judith A K; Dyer, Philip W

    2012-10-28

    N-Diphenylphosphino-7-aza-benzobicyclo[2.2.1]hept-2-ene (2) behaves as a chelating phosphine-alkene ligand for Pd(0) and Pd(II), promoting direct alkyl-alkyl and indirect alkyl-halide reductive elimination reactions due to the stabilisation of the resulting bis(phosphine-alkene)Pd(0) complex. PMID:22986447

  20. Development of a catalyst for conversion of syngas-derived materials to isobutylene. Technical progress report No. 6, July 1, 1992--September 30, 1992

    SciTech Connect

    Gajda, G.J.

    1993-09-10

    Goal is to develop a catalyst and technology that will produce iC{sub 4}{double_bond} directly from coal-derived syngas and that is capable of using a lower H{sub 2}/CO ratio (0.5 to 1.0). This report covers the testing of various zirconia (ZrO{sub 2}) based catalyst systems designed to examine effects of catalyst preparation and process variables, especially feed additives. Testing sol-gel ZrO{sub 2} catalysts calcined at 475 C instead of 500 C increases the isobutene yield. Supporting zirconia on high-surface-area sol-gel silica or silica-alumina results in low activity catalysts. Addition of ethylene, propylene, ethanol to feed produces hydrogenation, dimerization, and metathesis products, but little or no isobutene.

  1. A Bicyclo[4.2.0]octene-Derived Monomer Provides Completely Linear Alternating Copolymers via Alternating Ring-Opening Metathesis Polymerization (AROMP)

    PubMed Central

    2015-01-01

    Strained bicyclic carbomethoxy olefins were utilized as substrates in alternating ring-opening metathesis polymerization and found to provide low-dispersity polymers with novel backbones. The polymerization of methyl bicyclo[4.2.0]oct-7-ene-7-carboxylate with cyclohexene in the presence of the fast-initiating Grubbs catalyst (H2IMes)(3-Br-Pyr)2Cl2Ru=CHPh leads to a completely linear as well as alternating copolymer, as demonstrated by NMR spectroscopy, isotopic labeling, and gel permeation chromatography. In contrast, intramolecular chain-transfer reactions were observed with [5.2.0] and [3.2.0] bicyclic carbomethoxy olefins, although to a lesser extent than with the previously reported monocyclic cyclobutenecarboxylic ester monomers [SongA.; ParkerK. A.; SampsonN. S.J. Am. Chem. Soc.2009, 131, 344419275253]. Inclusion of cyclohexyl rings fused to the copolymer backbone minimizes intramolecular chain-transfer reactions and provides a framework for creating alternating functionality in a one-step polymerization. PMID:25328246

  2. Spontaneously Healable Thermoplastic Elastomers Achieved through One-Pot Living Ring-Opening Metathesis Copolymerization of Well-Designed Bulky Monomers.

    PubMed

    Yang, Ji-Xing; Long, Ying-Yun; Pan, Li; Men, Yong-Feng; Li, Yue-Sheng

    2016-05-18

    We report here a series of novel spontaneously healable thermoplastic elastomers (TPEs) with a combination of improved mechanical and good autonomic self-healing performances. Hard-soft diblock and hard-soft-hard triblock copolymers with poly[exo-1,4,4a,9,9a,10-hexahydro-9,10(1',2')-benzeno-l,4-methanoanthracene] (PHBM) as the hard block and secondary amide group containing norbornene derivative polymer as the soft block were synthesized via living ring-opening metathesis copolymerization by use of Grubbs third-generation catalyst through sequential monomer addition. The microstructure, mechanical, self-healing, and surface morphologies of the block copolymers were thoroughly studied. Both excellent mechanical performance and self-healing capability were achieved for the block copolymers because of the interplayed physical cross-link of hard block and dynamic interaction formed by soft block in the self-assembled network. Under an optimized hard block (PHBM) weight ratio of 5%, a significant recovery of tensile strength (up to 100%) and strain at break (ca. 85%) was achieved at ambient temperature without any treatment even after complete rupture. Moreover, the simple reaction operations and well-designed monomers offer versatility in tuning the architectures and properties of the resulting block copolymers. PMID:27136676

  3. Effect of potassium promotion on iron-based catalysts for Fischer-Tropsch synthesis

    SciTech Connect

    Raje, A.P.; O`Brien, R.J.; Davis, B.H.

    1998-11-15

    The effect of potassium on Fischer-Tropsch catalyst activity, kinetic parameters, and selectivity has been investigated for a precipitated iron catalyst that was employed with low H{sub 2}/CO ratio synthesis gas. A wide range of synthesis gas conversions have been obtained by varying space velocities over catalysts with various potassium loadings. Differing trends in catalyst activity with potassium loading were observed depending on the space velocity of synthesis gas conversion. As potassium loading increased, the catalyst activity either decreased (low conversion), passed through a maximum (intermediate conversion), or increased (high conversion). This is shown to be a result of the increasing dependency of the Fischer-Tropsch synthesis on the hydrogen formed by the water-gas shift reaction with increasing synthesis gas conversions. Both the rate constant and the adsorption parameter in a common two-parameter Fischer-Tropsch rate expression decreased with potassium loading; therefore, observed maxima in Fischer-Tropsch rate with potassium loading can be due to the opposing influences of these parameters. The effect of potassium on alkene selectivity was dependent on the number of carbon atoms of the hydrocarbons as well as the carbon monoxide conversion level. The extent of isomerization of 1-alkene product decreased with potassium loading, while the selectivity to methane decreased only slightly with increasing potassium content at CO conversions about 50% and higher.

  4. 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

  5. Cascade Photoredox/Iodide Catalysis: Access to Difluoro-γ-lactams via Aminodifluoroalkylation of Alkenes.

    PubMed

    Zhang, Muliang; Li, Weipeng; Duan, Yingqian; Xu, Pan; Zhang, Songlin; Zhu, Chengjian

    2016-07-01

    The novel cascade photoredox/iodide catalytic system enables the alkene to serve as a radical acceptor capable of achieving aminodifluoroalkylation of alkenes. Cheap iodide salts play a vital role in this reaction, which could tune carbocation reactivity through reversible C-I bond formation for controlling reaction selectivity, and a series of competitive reactions are completely eliminated in the presence of multiple reactivity pathways. The present dual catalytic protocol affords a very convenient method for direct synthesis of various difluoro-γ-lactams from simple and readily available starting materials under mild reaction conditions. PMID:27337532

  6. Cobalt-Catalyzed, Aminoquinoline-Directed Coupling of sp2 C–H Bonds with Alkenes

    PubMed Central

    2014-01-01

    A method for cobalt-catalyzed, aminoquinoline-directed ortho-functionalization of sp2 C–H bonds with alkenes has been developed. Reactions proceed at room temperature in trifluoroethanol solvent, use oxygen from air as an oxidant, and require Mn(OAc)3 as a cocatalyst. Benzoic, heteroaromatic, and acrylic acid aminoquinoline amides react with ethylene as well as mono- and disubstituted alkenes affording products in good yields. Excellent functional group tolerance is observed; halogen, nitro, ether, and unprotected alcohol functionalities are compatible with the reaction conditions. PMID:25146300

  7. Stereoselective Synthesis of Saturated Heterocycles via Pd-Catalyzed Alkene Carboetherification and Carboamination Reactions

    PubMed Central

    Wolfe, John P.

    2009-01-01

    The development of Pd-catalyzed carboetherification and carboamination reactions between aryl/alkenyl halides and alkenes bearing pendant heteroatoms is described. These transformations effect the stereoselective construction of useful heterocycles such as tetrahydrofurans, pyrrolidines, imidazolidin-2-ones, isoxazolidines, and piperazines. The scope, limitations, and applications of these reactions are presented, and current stereochemical models are described. The mechanism of product formation, which involves an unusual intramolecular syn-insertion of an alkene into a Pd-Heteroatom bond is also discussed in detail. PMID:19183704

  8. Nickel(0)-catalyzed intramolecular reductive coupling of alkenes and aldehydes or ketones with hydrosilanes.

    PubMed

    Hayashi, Yukari; Hoshimoto, Yoichi; Kumar, Ravindra; Ohashi, Masato; Ogoshi, Sensuke

    2016-05-01

    A nickel(0)-catalyzed reductive coupling of aldehydes and simple alkenes with hydrosilanes has been developed. A variety of silyl-protected 1-indanol derivatives were prepared in a highly diastereoselective manner (up to >99 : 1 dr) by employing a combination of nickel(0)/N-heterocyclic carbene and triethylsilane. The present system was also applied to a reductive coupling with ketones. Preliminary results of a nickel(0)-catalyzed asymmetric three-component coupling reaction of an aldehyde, an alkene, and triethylsilane are also shown. PMID:27077829

  9. Highly functionalized alkenes produced from base-free organocatalytic Wittig reactions: (E)-3-benzylidenepyrrolidine-2,5-dione, (E)-3-benzylidene-1-methylpyrrolidine-2,5-dione and (E)-3-benzylidene-1-tert-butylpyrrolidine-2,5-dione.

    PubMed

    Schirmer, Marie Luis; Spannenberg, Anke; Werner, Thomas

    2016-06-01

    The Wittig reaction is a fundamental transformation for the preparation of alkenes from carbonyl compounds and phosphonium ylides. The ylides are prepared prior to the olefination step from the respective phosphonium salts by deprotonation utilizing strong bases. A first free-base catalytic Wittig reaction for the preparation of highly functionalized alkenes was based on tributylphosphane as the catalyst. Subsequently we developed a system employing a phospholene oxide as a pre-catalyst and trimethoxysilane as reducing agent which operates under milder conditions. The title compounds, (E)-3-benzylidenepyrrolidine-2,5-dione, C11H9NO2, (I), the methylpyrrolidine derivative, C12H11NO2, (II), and the tert-butylpyrrolidine derivative, C15H17NO2, (III), have been synthesized by base-free catalytic Wittig reactions. In the crystal of (I), molecules are linked into centrosymmetric dimers via pairs of N-H...O hydrogen bonds. Furthermore, in the crystal structure of (III), there are two molecules in the asymmetric unit, whereas in (I) and (II), only one molecule is present. PMID:27256699

  10. Catalyst activator

    DOEpatents

    McAdon, Mark H.; Nickias, Peter N.; Marks, Tobin J.; Schwartz, David J.

    2001-01-01

    A catalyst activator particularly adapted for use in the activation of metal complexes of metals of Group 3-10 for polymerization of ethylenically unsaturated polymerizable monomers, especially olefins, comprising two Group 13 metal or metalloid atoms and a ligand structure including at least one bridging group connecting ligands on the two Group 13 metal or metalloid atoms.

  11. Effect of support on metathesis of n-decane: drastic improvement in alkane metathesis with WMe5 linked to silica-alumina.

    PubMed

    Samantaray, Manoja K; Dey, Raju; Abou-Hamad, Edy; Hamieh, Ali; Basset, Jean-Marie

    2015-04-13

    [WMe6 ] (1) supported on the surface of SiO2 -Al2 O3(500) (2) has been extensively characterized by solid-state NMR spectroscopy, elemental analysis, and gas quantification, which clearly reveal the formation of a mixture of monopodal and bipodal species with the migration of methyl from W to Al. The supported species SiO2 -Al2 O3(500) (2) transformed at 120 °C into two types of carbynic centers, one of which is cationic and the other neutral. These species are very efficient for the metathesis of n-decane. Comparison with already-synthesized neutral bipodal tungsten indicates that the high increase in activity is due to the cationic character of the grafted tungsten. PMID:25760771

  12. Sustainable solid catalyst alkylation of commercial olefins by regeneration with supercritical isobutane

    SciTech Connect

    Daniel M. Ginosar; David N. Thompson; Kyle C. Burch

    2005-12-01

    Supercritical isobutane regeneration of a USY zeolite alkylation catalyst was examined in a continuous, automated reaction / regeneration system. Two feeds were studied; a synthetic isobutane / 2-butene blend, and a commercial refinery isoparaffin / olefin blend. The refinery blend was minimally treated, containing a variety of light olefins, and contaminants, including butadiene, oxygenates and sulfur, which are well known to cause severe catalyst deactivation. Synthetic feed experiments showed that high levels of butene conversion was maintained for more than 200 hours time on stream, and that product quality and catalyst maintenance was relatively stable over the course of the experiment using a 3 hour reaction / 3 hour regeneration cycle. Catalyst activity maintenance was lower when the commercial feed was employed. High levels of alkene conversion were maintained for 78 hours and 192 hours using a 3 hour reaction / 3 hour regeneration cycle and a 2 hour reaction / 2 hour regeneration cycle, respectively.

  13. Low-Temperature Synthesis of Actinide Tetraborides by Solid-State Metathesis Reactions

    SciTech Connect

    Lupinetti, Anthony J.; Garcia, Eduardo; Abney, Kent D.

    2004-12-14

    The synthesis of actinide tetraborides including uranium tetraboride (UB,), plutonium tetraboride (PUB,) and thorium tetraboride (ThB{sub 4}) by a solid-state metathesis reaction are demonstrated. The present method significantly lowers the temperature required to {approx_equal}850 C. As an example, when UCl{sub 4}, is reacted with an excess of MgB{sub 2}, at 850 C, crystalline UB, is formed. Powder X-ray diffraction and ICP-AES data support the reduction of UCl{sub 3}, as the initial step in the reaction. The UB, product is purified by washing water and drying.

  14. Rapid Solid-State Metathesis Routes to Nanostructured Silicon-Germainum

    NASA Technical Reports Server (NTRS)

    Kaner, Richard B. (Inventor); Bux, Sabah K. (Inventor); Fleurial, Jean-Pierre (Inventor); Rodriguez, Marc (Inventor)

    2014-01-01

    Methods for producing nanostructured silicon and silicon-germanium via solid state metathesis (SSM). The method of forming nanostructured silicon comprises the steps of combining a stoichiometric mixture of silicon tetraiodide (SiI4) and an alkaline earth metal silicide into a homogeneous powder, and initating the reaction between the silicon tetraiodide (SiI4) with the alkaline earth metal silicide. The method of forming nanostructured silicon-germanium comprises the steps of combining a stoichiometric mixture of silicon tetraiodide (SiI4) and a germanium based precursor into a homogeneous powder, and initiating the reaction between the silicon tetraiodide (SiI4) with the germanium based precursors.

  15. Recent advances in metathesis-derived polymers containing transition metals in the side chain.

    PubMed

    Dragutan, Ileana; Dragutan, Valerian; Simionescu, Bogdan C; Demonceau, Albert; Fischer, Helmut

    2015-01-01

    This account critically surveys the field of side-chain transition metal-containing polymers as prepared by controlled living ring-opening metathesis polymerization (ROMP) of the respective metal-incorporating monomers. Ferrocene- and other metallocene-modified polymers, macromolecules including metal-carbonyl complexes, polymers tethering early or late transition metal complexes, etc. are herein discussed. Recent advances in the design and syntheses reported mainly during the last three years are highlighted, with special emphasis on new trends for superior applications of these hybrid materials. PMID:26877797

  16. Recent advances in metathesis-derived polymers containing transition metals in the side chain

    PubMed Central

    Demonceau, Albert; Fischer, Helmut

    2015-01-01

    Summary This account critically surveys the field of side-chain transition metal-containing polymers as prepared by controlled living ring-opening metathesis polymerization (ROMP) of the respective metal-incorporating monomers. Ferrocene- and other metallocene-modified polymers, macromolecules including metal-carbonyl complexes, polymers tethering early or late transition metal complexes, etc. are herein discussed. Recent advances in the design and syntheses reported mainly during the last three years are highlighted, with special emphasis on new trends for superior applications of these hybrid materials. PMID:26877797

  17. Synthesis of Cyclic Porphyrin Trimers through Alkyne Metathesis Cyclooligomerization and Their Host-Guest Binding Study.

    PubMed

    Yu, Chao; Long, Hai; Jin, Yinghua; Zhang, Wei

    2016-06-17

    Cyclic porphyrin trimers were synthesized through one-step cyclooligomerization via alkyne metathesis from diyne monomers. These macrocycles show interesting host-guest binding interactions with fullerenes, selectively binding C70 (6 × 10(3) M(-1)) over C60 and C84 (no binding observed). The fullerene-encapsulated host-guest complex can undergo guest or host exchange in the presence of another guest (2,4,6-tri(4-pyridyl)-1,3,5-triazine) or host (cage COP5) molecule with higher binding affinity. PMID:27267936

  18. Room Temperature Ionic Liquids as Green Solvent Alternatives in the Metathesis of Oleochemical Feedstocks.

    PubMed

    Thomas, Priya A; Marvey, Bassy B

    2016-01-01

    One of the most important areas of green chemistry is the application of environmentally friendly solvents in catalysis and synthesis. Conventional organic solvents pose a threat to the environment due to the volatility, highly flammability, toxicity and carcinogenic properties they exhibit. The recently emerged room temperature ionic liquids (RTILs) are promising green solvent alternatives to the volatile organic solvents due to their ease of reuse, non-volatility, thermal stability and ability to dissolve a variety of organic and organometallic compounds. This review explores the use of RTILs as green solvent media in olefin metathesis for applications in the oleochemical industry. PMID:26861282

  19. 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

  20. 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.

  1. Catalytic production of sulfur heterocycles (dihydrobenzodithiins): a new application of ligand-based alkene reactivity.

    PubMed

    Harrison, Daniel J; Fekl, Ulrich

    2009-12-28

    Activation of bis-o-phenylene tetrasulfide to render it a practical benzodithiete equivalent for [4+2] cycloadditions with alkenes has been achieved with catalytic amounts of Mo(tfd)(2)(bdt) (tfd = S(2)C(2)(CF(3))(2); bdt = S(2)C(6)H(4)). Substituted 2,3-dihydro-1,4-benzodithiins are produced. PMID:20024283

  2. 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.

  3. The reactions of ozone with alkenes: An important source of HOx in the boundary layer

    NASA Astrophysics Data System (ADS)

    Paulson, Suzanne E.; Orlando, John J.

    The reactions of ozone with alkenes have been shown recently to lead to the direct production of OH radicals. Organic peroxy radicals (RO2) probably accompany the production of OH. In this paper, we draw attention to the potential importance of these reactions in the primary production of HOx (HOx = OH, HO2 and RO2) radicals in various regions of the boundary layer. The reactions of ozone with anthropogenic alkenes are shown to be the most important source of HOx in many urban settings during the day and evening, and a significant source at night. The majority of HOx comes from trace quantities of alkenes with internal double bonds. Reaction of O3 with isoprene and terpenes can be an important source of HOx in forested regions; we show that these reactions are the dominant radical source in the late afternoon and into the night. This additional HOx source is expected to increase predicted OH concentrations compared to those calculated by models that do not include the O3-alkene source.

  4. Photochemical alkene formation in seawater from dissolved organic carbon: Results from laboratory experiments

    NASA Astrophysics Data System (ADS)

    Ratte, M.; Bujok, O.; Spitzy, A.; Rudolph, J.

    1998-03-01

    The production mechanism of light alkenes, alkanes, and isoprene was investigated in laboratory experiments by measuring their concentrations in natural seawater as a function of spectral range, exposure time and origin, and concentration of dissolved organic carbon (DOC). The production mechanism of alkanes and of isoprene could not be clarified. Ethene and propene are produced photochemically from DOC. The relevant spectral range is UV and short-wavelength visible light. Initial production rates (up to day 10 of exposure) were in the range of several pmol L-1 h-1 (mg DOC)-1; the corresponding mean quantum yields for the spectral range of 300-420 nm were about 10-8. Generally, the production rates and the quantum yields for ethene were about 2 times that of propene. The key factors in the total column integrated oceanic alkene production are the solar photon flux at sea surface, the penetration depth of the light into the ocean (especially the relation between different light absorbers, i.e., the extinction due to absorption of DOC), and the wavelength- and DOC-dependent quantum yields. As a result of the high variability of these parameters, actual local alkene production rates for a specific oceanic region may differ considerably from the globally averaged oceanic alkene production rates. The latter were estimated to be at most 5 Mt yr-1.

  5. Photoredox-Catalyzed Bromodifluoromethylation of Alkenes with (Difluoromethyl)triphenylphosphonium Bromide.

    PubMed

    Lin, Qing-Yu; Ran, Yang; Xu, Xiu-Hua; Qing, Feng-Ling

    2016-05-20

    Under visible-light photoredox conditions, difluoromethyltriphenylphosphonium bromide was used as the precursor of the CF2H radical for bromodifluoromethylation of alkenes. The presence of catalytic CuBr2 resulted in the selective formation of the bromodifluoromethylated products. PMID:27136958

  6. Uranyl photochemistry with alkenes: Distinguishing between H-atom abstraction and electron transfer

    SciTech Connect

    McCleskey, T.M.; Burns, C.J.; Tumas, W.

    1999-12-13

    Recent studies with the uranyl ion (UO{sub 2{sup 2+}}) have shown that it has the potential to photocatalytically oxidize organic substrates in the presence of air. The excited-state UO{sub 2}{sup 2+}* is a potent oxidant (E{degree} = 2.6 V), and is quenched by a variety of organic substrates. The resulting U(V) species can then be oxidized back to UO{sub 2}{sup 2+} in the presence of oxygen. Previous studies with alcohols have shown, through kinetic isotope effects, that the quenching of the uranyl excited state occurs by hydrogen atom abstraction to give UO{sub 2}H{sup +} and an organic radical. The mechanism of quenching with alkenes has not been definitely determined. Proposals for quenching mechanisms with alkenes have included exciplex formation, H-atom abstraction, and electron transfer. The authors report here on a series of quenching studies between uranyl and a variety of alkene substrates that unequivocally demonstrate quenching of the uranyl excited state with alkenes occurs by electron transfer.

  7. 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...

  8. 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...

  9. Substituent-enabled oxidative dehydrogenative cross-coupling of 1,4-naphthoquinones with alkenes.

    PubMed

    Zhang, Chi; Wang, Meining; Fan, Zhoulong; Sun, Li-Ping; Zhang, Ao

    2014-08-15

    A Rh-catalyzed oxidative dehydrogenative cross-coupling of 1,4-naphthquinones with alkenes was achieved by using a substituent-enabled C(sp(2))-H functionalization (SEF) strategy. The method shows high functional group tolerance, broad substrate scope, and great potential for further functional transformations. PMID:25075553

  10. 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...

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

    PubMed

    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

  12. Visible-light-induced photocatalytic azotrifluoromethylation of alkenes with aryldiazonium salts and sodium triflinate.

    PubMed

    Yu, Xing-Long; Chen, Jia-Rong; Chen, Dong-Zhen; Xiao, Wen-Jing

    2016-07-01

    The efficient visible light photocatalytic azotrifluoromethylation of alkenes with aryldiazonium salts and sodium triflinate is described, which gave the corresponding trifluoromethylated azo compounds in generally good yields. The trifluoromethylated azo products can be easily transformed into useful heterocycles and nitrogen-containing building blocks. PMID:27292589

  13. 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

  14. Lewis Acid-Promoted [2+2] Cycloadditions of Alkenes with Arylketenes

    PubMed Central

    Rigsbee, E. M.; Zhou, C.; Rasik, C. M.; Sptiz, A. Z.; Nichols, A. J.; Brown, M. K.

    2015-01-01

    A method for the [2+2] cycloaddition of arylketenes and alkenes is presented. The process involves the in situ generation of a ketene in the presence of a Lewis acid. The utility of products is demonstrated towards the synthesis of a common scaffold found in several natural product families. PMID:26419921

  15. 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

  16. Catalyst suppliers consolidate further, offer more catalysts

    SciTech Connect

    Rhodes, A.K.

    1995-10-02

    The list of suppliers of catalysts to the petroleum refining industry has decreased by five since Oil and Gas Journal`s survey of refining catalysts and catalytic additives was last published. Despite the consolidation, the list of catalyst designations has grown to about 950 in this latest survey, compared to 820 listed in 1993. The table divides the catalysts by use and gives data on their primary differentiating characteristics, feedstock, products, form, bulk density,catalyst support, active agents, availability, and manufactures.

  17. I. Direct observation of zirconocene-catalyzed alkene polymerization via NMR and the role of an aluminum alkyl during polymerization. II. Design and evaluation of an online nanoscience course for teachers

    NASA Astrophysics Data System (ADS)

    Tomasik, Janice Hall

    The plastics industry has been revolutionalized by development of group 4 metallocene polymerization catalysts. These catalysts have higher activities and stereoselectivities than traditional heterogeneous Ziegler-Natta polymerization catalysts, and produce polymers with narrower molecular weight distributions and with better control of the polymer stereochemistry. The reaction kinetics of catalytic alkene polymerizations are complicated and difficult to resolve macroscopically. To overcome these difficulties, research has used NMR spectroscopy to directly observe catalytic reaction intermediates; many advances in our understanding of the complex mechanisms behind these polymerization reactions have resulted. In this work, the direct observation of alkene insertion into zirconocene-polymeryls via NMR spectroscopy is presented. Alkenes studied are 3-methylpentene, styrene, and 1,4-pentadiene. Kinetic measurements are reported for the polymerization of 3-methylpentene by rac-(EBI)Zr(Me)(MeB(C6F 5)3) (EBI = C2H4(1-indenyl)2) and rac-(EBI)Zr(polyhexenyl)(MeB(C6F5) 3). Also presented are NMR spectroscopic characterizations of rac-(EBI)Zr(styrenyl)(MeB(C6F5)3) and rac-(EBI)Zr(1,4-pentadienyl)(MeB(C6F 5)3). In addition, NMR spectroscopy is used to directly monitor the behavior of an aluminum alkyl during the polymerization of 1-hexene by rac -(EBI)2Zr(Me)(MeB(C6F5)3). The rates of polymerization are not inhibited by Al(iBu) 2(BHT), Al(Me)(BHT)2, or Al(iBu)3 (BHT = 2,6-di- tert-butyl-4-methylphenyl). Detailed measurement of polymerization rate and catalyst speciation demonstrate that BHT modified aluminum alkyls protect active sites from decomposition in the presence of protic impurities such as methanol. Also presented in this work is the design and evaluation of an online course for teachers about nanoscience. Nanotechnology is an important emerging field that is estimated to need about 2 million workers worldwide by 2015. Therefore the educational system is being

  18. Hydrocracking catalyst

    SciTech Connect

    Hilfman, L.; O'Hara, M.

    1980-07-01

    A description is given of a process for the conversion of heavy hydrocarbon oil boiling above about 650/sup 0/F into lower boiling hydrocarbons, which comprises hydrocracking the heavy oil in admixture with hydrogen and in contact with a catalyst with comprising a ra re earth exchange metal component and a platinum group metal component supported on a mixture of ziegler alumina and a zeolite.

  19. Structure and Biochemical Properties of the Alkene Producing Cytochrome P450 OleTJE (CYP152L1) from the Jeotgalicoccus sp. 8456 Bacterium*

    PubMed Central

    Belcher, James; McLean, Kirsty J.; Matthews, Sarah; Woodward, Laura S.; Fisher, Karl; Rigby, Stephen E. J.; Nelson, David R.; Potts, Donna; Baynham, Michael T.; Parker, David A.; Leys, David; Munro, Andrew W.

    2014-01-01

    The production of hydrocarbons in nature has been documented for only a limited set of organisms, with many of the molecular components underpinning these processes only recently identified. There is an obvious scope for application of these catalysts and engineered variants thereof in the future production of biofuels. Here we present biochemical characterization and crystal structures of a cytochrome P450 fatty acid peroxygenase: the terminal alkene forming OleTJE (CYP152L1) from Jeotgalicoccus sp. 8456. OleTJE is stabilized at high ionic strength, but aggregation and precipitation of OleTJE in low salt buffer can be turned to advantage for purification, because resolubilized OleTJE is fully active and extensively dissociated from lipids. OleTJE binds avidly to a range of long chain fatty acids, and structures of both ligand-free and arachidic acid-bound OleTJE reveal that the P450 active site is preformed for fatty acid binding. OleTJE heme iron has an unusually positive redox potential (−103 mV versus normal hydrogen electrode), which is not significantly affected by substrate binding, despite extensive conversion of the heme iron to a high spin ferric state. Terminal alkenes are produced from a range of saturated fatty acids (C12–C20), and stopped-flow spectroscopy indicates a rapid reaction between peroxide and fatty acid-bound OleTJE (167 s−1 at 200 μm H2O2). Surprisingly, the active site is highly similar in structure to the related P450BSβ, which catalyzes hydroxylation of fatty acids as opposed to decarboxylation. Our data provide new insights into structural and mechanistic properties of a robust P450 with potential industrial applications. PMID:24443585

  20. Polymorph selectivity of superconducting CuSe₂ through kinetic control of solid-state metathesis.

    PubMed

    Martinolich, Andrew J; Kurzman, Joshua A; Neilson, James R

    2015-03-25

    Rational preparation of materials by design is a major goal of inorganic, solid-state, and materials chemists alike. Oftentimes, the use of nonmetallurgical reactions (e.g., chalcogenide fluxes, hydrothermal syntheses, and in this case solid-state metathesis) alters the thermodynamic driving force of the reaction and allows new, refractory, or otherwise energetically unfavorable materials to form under softer conditions. Taking this a step further, alteration of a metathesis reaction pathway can result in either the formation of the equilibrium marcasite polymorph (by stringent exclusion of air) or the kinetically controlled formation of the high-pressure pyrite polymorph of CuSe2 (by exposure to air). From analysis of the reaction coordinate with in situ synchrotron X-ray diffraction and pair distribution function analysis as well as differential scanning calorimetry, it is clear that the air-exposed reaction proceeds via slight, endothermic rearrangements of crystalline intermediates to form pyrite, which is attributed to partial solvation of the reaction from atmospheric humidity. In contrast, the air-free reaction proceeds via a significant exothermic process to form marcasite. Decoupling the formation of NaCl from the formation of CuSe2 enables kinetic control to be exercised over the resulting polymorph of these superconducting metal dichalcogenides. PMID:25746853

  1. Slurry phase Fischer-Tropsch synthesis: Cobalt plus a water-gas shift catalyst. [Quarterly] report, June 30, 1988--September 30, 1988

    SciTech Connect

    Yates, I.C.; Satterfield, C.N.

    1988-12-31

    This report details experiments performed on three different copper-based catalysts: Cu/Cr{sub 2}O{sub 3}, Cu/MnO/Cr{sub 2}O{sub 3} and Cu/ZnO/Al{sub 2}O{sub 3}. Of these three catalysts, the Cu/ZnO/Al{sub 2}O{sub 3} exhibits the greatest stability when slurried in octacosane. More than 1000 hours-on-stream indicate that the catalyst activity is not detrimentally affected by high pressure, high H{sub 2}/CO ratio, or the presence of alkenes. All of these are necessary stability characteristics for the water-gas shift catalyst, if it is to be used in combination with a cobalt Fischer-Tropsch catalyst. A review of documented reduction procedures for cobalt-based Fischer-Tropsch catalysts is presented.

  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. Absence of the Thorpe–Ingold Effect by gem-Diphenyl Groups in Ring-Closing Enyne Metathesis

    PubMed Central

    Kim, Yi Jin; Grimm, Jonathan B.; Lee, Daesung

    2007-01-01

    In tandem ring-closing metathesis of alkynyl silaketals containing two different tethered olefins, the gem-dimethyl group showed the expected Thorpe-Ingold effect, thereby giving good level of group selectivity. Unexpectedly, however, the corresponding gem-diphenyl group did not show any Thorpe-Ingold effect for the ring closure reaction. PMID:18046462

  4. A stereoselective synthesis of (+)-physoperuvine using a tandem aza-Claisen rearrangement and ring closing metathesis reaction.

    PubMed

    Zaed, Ahmed M; Swift, Michael D; Sutherland, Andrew

    2009-07-01

    A stereoselective synthesis of (+)-physoperuvine, a tropane alkaloid from Physalis peruviana Linne has been developed using a one-pot tandem aza-Claisen rearrangement and ring closing metathesis reaction to form the key amino-substituted cycloheptene ring. PMID:19532981

  5. Structure-property relationships in novel polymers and block copolymers from ring-opening metathesis polymerization

    NASA Astrophysics Data System (ADS)

    Bishop, John Paul

    2011-12-01

    The desire to tune macroscopic properties by controlling the underlying microscopic structure is a driving force in many different areas of scientific research, including polymer science. In living ring-opening metathesis polymerization (ROMP), the subject of this dissertation, there are a variety of different ways to alter the microscopic structure through synthesis. This is in part due to the presence of double bonds in the polymeric backbone, which can influence properties both through their isomeric structures (cis vs. trans) and through their removal by catalytic hydrogenation. Here, we demonstrate the ability to tune a variety of microstructural parameters of our ROMP polymers through synthesis, and investigate the resulting effects on macroscopic properties. ROMP and subsequent hydrogenation provide access to crystalline, glassy, and rubbery polymers, representing essentially the entire spectrum of polymer properties. These include hydrogenated polynorbornene (hPN), a highly crystalline polymer with Tm° = 156°C; hydrogenated poly(5-hexylnorbornene) (hPHN), a rubbery amorphous polymer with Tg = -22°C; and hydrogenated polymethyltetracyclododecene (hPMTD), a glassy polymer with Tg = 163°C. The microstructure of block copolymers of hPN, hPHN, and hPMTD can be controlled by varying block sequence, block lengths, and number of blocks. We used this control to design and synthesize thermoplastic elastomers (TPEs) containing both crystalline and glassy hard segments, with the aim of capturing the mechanical properties of conventional all-amorphous triblock TPEs, while forming the solid-state structure by crystallization from a single-phase melt. To accomplish this, we synthesized symmetric pentablock copolymers with the architecture crystalline-glassy-rubbery-glassy-crystalline. With this pentablock architecture and appropriate selection of block lengths, crystallization from a single-phase melt causes a layer rich in the glassy block to form around the

  6. Rheokinetic evaluation of self-healing agents polymerized by Grubbs catalyst embedded in various thermosetting systems

    NASA Astrophysics Data System (ADS)

    Liu, Xing; Sheng, Xia; Lee, Jong Keun; Kessler, Michael R.

    2007-07-01

    In self-healing polymers and composites, the activity of the embedded chemical catalyst within the thermosetting matrix is critical to healing efficiency. Rheological behavior of ring-opening metathesis polymerization (ROMP)-based healing agents, triggered by 1st or 2nd generation Grubbs catalysts that have been suspended in various thermosetting resins, was investigated using an oscillatory parallel plate rheometer. Gel times for various healing agents were determined from the crossover of storage and loss moduli vs. time curves to indicate the activity of the ROMP reaction. Gelation of healing agents initiated by 1st generation Grubbs catalyst occurred faster than those triggered by 2nd generation catalyst. It is suggested that the dissolution rate of the catalyst by the healing agent is an important factor in determining the overall ROMP reaction rate in situ. Optical and scanning electron microscopic observations showed that the finer, rod-like solid particles of the 1st generation catalyst were distributed more homogeneously throughout the cured matrix, which contributed to the faster reaction. Also discussed were effects of different healing agents and thermosetting matrix systems on the ROMP reaction. These results indicate that the self-healing methodology can be expanded to other high performance polymer matrices.

  7. [Catalyst research]. Final Report

    SciTech Connect

    Ian P Rothwell; David R McMillin

    2005-03-14

    Research results are the areas of catalyst precursor synthesis, catalyst fluxionality, catalyst stability, polymerization of {alpha}-olefins as well as the chemistry of Group IV and Group V metal centers with aryloxide and arylsulfide ligands.

  8. Nanoscale Control of Polymer Assembly on a Synthetic Catalyst-Bilayer System.

    PubMed

    Gorgoll, Ricardo M; Harano, Koji; Nakamura, Eiichi

    2016-08-01

    The use of the interior of self-assembled membrane as a template for polymer synthesis and assembly has long attracted the interest of chemists. However, it is difficult to utilize a lipid membrane as a chemical reactor for controlled assembly for polymers because lipid membrane is easily destabilized by loading of extraneous molecules. We found that a several-nanometer-thick bilayer vesicle made by self-assembly of an organic fullerene amphiphile doped with a metathesis catalyst serves as a nanosized chemical reactor in water, where a polymer is synthesized and assembled, depending on the affinity of the growing polymer to the organic groups on the amphiphile. This catalyst-bilayer system can thus control supramolecular assembly of the ester-functionalized polymer product into different nanoscale structures: a nanoparticle made of a single polymer chain and a nanocapsule made of several tens of polymer chains. PMID:27404736

  9. 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

  10. Syntheses of hydroxamic acid-containing bicyclic β-lactams via palladium-catalyzed oxidative amidation of alkenes.

    PubMed

    Jobbins, Maria O; Miller, Marvin J

    2014-02-21

    Palladium-catalyzed oxidative amidation has been used to synthesize hydroxamic acid-containing bicyclic β-lactam cores. Oxidative cleavage of the pendant alkene provides access to the carboxylic acid in one step. PMID:24483144

  11. Slurry phase Fischer-Tropsch synthesis: Cobalt plus a water-gas shift catalyst, January 1, 1990--March 30, 1990

    SciTech Connect

    Yates, I.C.; Satterfield, C.N.

    1990-01-01

    Experiments to study cobalt-catalyzed reactions of light 1-alkenes added to synthesis gas feed have been performed. Data have been collected at 220{degrees}C, 0.45 to 1.48 MPa and a synthesis gas flow rate between 0.015 and 0.030 Nl/(gcatmin) with H{sub 2}/CO of 1.45 to 2.25. C{sub 2}H{sub 4}, C{sub 3}H{sub 6}, and C{sub 4}H{sub 8} were added to the synthesis gas feed in concentrations ranging from 0.5 to 1.2 mole% of total feed. For each material balance in which 1-alkenes were added, a material balance was performed at similar process conditions without 1-alkenes added. This use of base case'' process conditions should make data analysis and interpretation easier. Material balances without 1-alkenes were also repeated to allow verification of catalyst selectivity stability. A total of 49 balances were performed during a single run which lasted over 2500 hours-on-stream. The hydrocarbon data have not yet been completed analyzed.

  12. Slurry phase Fischer-Tropsch synthesis: Cobalt plus a water-gas shift catalyst, January 1, 1990--March 30, 1990

    SciTech Connect

    Yates, I.C.; Satterfield, C.N.

    1990-12-31

    Experiments to study cobalt-catalyzed reactions of light 1-alkenes added to synthesis gas feed have been performed. Data have been collected at 220{degrees}C, 0.45 to 1.48 MPa and a synthesis gas flow rate between 0.015 and 0.030 Nl/(gcatmin) with H{sub 2}/CO of 1.45 to 2.25. C{sub 2}H{sub 4}, C{sub 3}H{sub 6}, and C{sub 4}H{sub 8} were added to the synthesis gas feed in concentrations ranging from 0.5 to 1.2 mole% of total feed. For each material balance in which 1-alkenes were added, a material balance was performed at similar process conditions without 1-alkenes added. This use of ``base case`` process conditions should make data analysis and interpretation easier. Material balances without 1-alkenes were also repeated to allow verification of catalyst selectivity stability. A total of 49 balances were performed during a single run which lasted over 2500 hours-on-stream. The hydrocarbon data have not yet been completed analyzed.

  13. Olefin cross metathesis based de novo synthesis of a partially protected L-amicetose and a fully protected L-cinerulose derivative

    PubMed Central

    Hauke, Sylvia

    2014-01-01

    Summary Cross metathesis of a lactate derived allylic alcohol and acrolein is the entry point to a de novo synthesis of 4-benzoate protected L-amicetose and a cinerulose derivative protected at C5 and C1. PMID:24991253

  14. An Electronic Rationale for Observed Initiation Rates in Ruthenium-Mediated Olefin Metathesis: Charge Donation in Phosphine And N-Heterocyclic Carbene Ligands

    SciTech Connect

    Getty, K.; Delgado-Jaime, M.U.; Kennepohl, P.

    2009-06-01

    Ru K-edge XAS data indicate that second generation ruthenium-based olefin metathesis precatalysts (L = N-heterocyclic carbene) possess a more electron-deficient metal center than in the corresponding first generation species (L = tricyclohexylphosphine). This surprising effect is also observed from DFT calculations and provides a simple rationale for the slow phosphine dissociation kinetics previously noted for second-generation metathesis precatalysts.

  15. Alkoxy Hydrosilanes As Surrogates of Gaseous Silanes for Hydrosilylation of Alkenes.

    PubMed

    Buslov, Ivan; Keller, Sébastien Carlos; Hu, Xile

    2016-04-15

    Me2SiH2, MeSiH3, and SiH4 are gaseous and flammable silanes that are inconvenient to use in chemical reactions. Catalytic amounts of a nickel pincer complex and NaO(t)Bu are reported to allow the synthesis of alkyl hydrosilanes from alkenes and alkoxy hydrosilanes, leading to the replacement of Me2SiH2, MeSiH3, and SiH4 by Me2(MeO)SiH, Me(EtO)2SiH, and (MeO)3SiH in hydrosilylation reactions of alkenes. The scope and mechanism of the reactions are also described. PMID:27045341

  16. Stabilized borata-alkene formation: structural features, reactions and the role of the counter cation.

    PubMed

    Kohrt, Sonja; Dachwitz, Steffen; Daniliuc, Constantin G; Kehr, Gerald; Erker, Gerhard

    2015-12-28

    Dimethylbenzofulvene adds Piers' borane [HB(C6F5)2] at the indene double bond to give a mixture of regioisomeric boranes 8a,b. Subsequent isomerization under equilibrium conditions gives the isopropyl substituted 1H and 3H borylindenes 10a,b. Their treatment with the bulky LiTMP base under frustrated Lewis pair conditions resulted in a clean deprotonation reaction to give the borata-alkene 14. Its X-ray crystal structure analysis indicated a pronounced B[double bond, length as m-dash]C double bond character and thus a borata-benzofulvene description. The borata-alkene underwent (probably stepwise) [4 + 2] cycloaddition reactions with chalcone derivatives and a formal [6 + 2] cycloaddition with phenylmethylketene. Many products and derivatives were characterized by X-ray diffraction. PMID:26584629

  17. STUDY OF SOLVENT AND CATALYST INTERACTIONS IN DIRECT COAL LIQUEFACTION

    SciTech Connect

    Michael T. Klein; William H. Calkins; Jasna Tomic

    2000-10-04

    To provide a better understanding of the roles of a solid catalyst and the solvent in Direct Coal Liquefaction, a small reactor was equipped with a porous-walled basket which was permeable to the solvent but was not permeable to the coal or solid catalyst. With this equipment and a high volatile bituminous coal it was found that direct contact between the catalyst in the basket and the coal outside the basket is not required for catalyzed coal liquefaction. The character of the solvent in this system makes a significant difference in the conversion of the coal, the better solvents being strong donor solvents. Because of the extensive use of thermogravimetric analysis in this laboratory, it was noted that the peak temperature for volatiles evolution from coal was a reliable measure of coal rank. Because of this observation, a variety of coals of a range of ranks was investigated. It was shown in this work that measuring the peak temperature for volatiles evolution was a quite precise indicator of rank and correlated closely with the rank value obtained by measuring vitrinite reflectance, a more difficult measurement to make. This prompted the desire to know the composition of the volatile material evolved as a function of coal rank. This was then measured by coupling a TGA to a mass spectrometer using laser activation and photoionization detection TG-PI-MS. The predominant species in volatiles of low rank coal turned out to be phenols with some alkenes. As the rank increases, the relative amounts of alkene and aromatic hydrocarbons increases and the oxygenated species decrease. It was shown that these volatiles were actually pyrolytic products and not volatilization products of the coal. Solvent extraction experiments coupled with Thermogravimetric-photoionization-mass spectrometry (TG-PI-MS) indicated that the low boiling and more extractable material are essentially similar in chemical types to the non-extractable portions but apparently higher molecular weight

  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. 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

  20. 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. PMID:24171583

  1. 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

  2. Studies on the formation of H 2O 2 in the ozonolysis of alkenes

    NASA Astrophysics Data System (ADS)

    Becker, K. H.; Bechara, J.; Brockmann, K. J.

    The formation of H 2O 2 in the reactions of ozone with alkenes, isoprene and some terpenes has been studied with tunable diode laser absorption spectroscopy. The measured yields of H 2O 2 were found to be considerably enhanced in the presence of water vapour. H 2O 2 is thought to be formed in the ozonolysis of the alkene with O 3 by direct reaction of an intermediate with water vapour. The yield of H 2O 2 relative to the reacted alkene in the ozonolysis of trans-2-butene in the presence of water vapour was also studied with long path FTIR spectroscopy. Irrespective of the analytical methods and reaction conditions applied, the H 2O 2 yields in the reaction of O 3 with the different alkenes in the presence of water vapour were found to be in the range of a few per cent or less. Under the assumption that the reactive species forming H 2O 2 in the ozonolysis is the Criegee biradical, the overall rate constants for the reactions of some biradicals with water vapour were measured relative to the rate constant of the biradical with SO 2. For the H 2COO biradical a rate constant of (5.8 ± 2.5) × 10 -17 cm 3 s -1 was determined and for the (CH 3) 2COO biradical (2.9 ± 1.5) × 10 -17 cm 3 s -1; in the latter case with the assumption that (CH 3) 2COO reacts with SO 2 as fast as CH 2COO.

  3. Base-Induced Radical Carboamination of Nonactivated Alkenes with Aryldiazonium Salts.

    PubMed

    Kindt, Stephanie; Wicht, Karina; Heinrich, Markus R

    2015-12-18

    A new transition-metal-free version of the Meerwein arylation has been developed. The key feature of this carboamination-type reaction is the slow base-controlled generation of aryl radicals from aryldiazonium tetrafluoroborates, so that a sufficient quantity of diazonium ions remains to enable efficient trapping of the alkyl radical adduct resulting from aryl radical addition to the alkene. Under strongly basic conditions, diazoanhydrides are likely to take over the role of the nitrogen-centered radical scavengers. PMID:26636470

  4. Copper-Catalyzed Amino Lactonization and Amino Oxygenation of Alkenes Using O-Benzoylhydroxylamines.

    PubMed

    Hemric, Brett N; Shen, Kun; Wang, Qiu

    2016-05-11

    A copper-catalyzed amino lactonization of unsaturated carboxylic acids has been achieved as well as the analogous intermolecular three-component amino oxygenation of olefins. The transformation features mild conditions and a remarkably broad substrate scope, offering a novel and efficient approach to construct a wide range of amino lactones as well as 1,2-amino alcohol derivatives. Mechanistic studies suggest that the reaction proceeds via a distinctive O-benzoylhydroxylamine-promoted electrophilic amination of alkenes. PMID:27114046

  5. Enantioselective CuH-Catalyzed Reductive Coupling of Aryl Alkenes and Activated Carboxylic Acids.

    PubMed

    Bandar, Jeffrey S; Ascic, Erhad; Buchwald, Stephen L

    2016-05-11

    A new method for the enantioselective reductive coupling of aryl alkenes with activated carboxylic acid derivatives via copper hydride catalysis is described. Dual catalytic cycles are proposed, with a relatively fast enantioselective hydroacylation cycle followed by a slower diastereoselective ketone reduction cycle. Symmetrical aryl carboxyclic anhydrides provide access to enantioenriched α-substituted ketones or alcohols with excellent stereoselectivity and functional group tolerance. PMID:27121395

  6. TfNHNHBoc as a Trifluoromethylating Agent for Vicinal Difunctionalization of Terminal Alkenes.

    PubMed

    Guo, Jing-Yu; Wu, Ruo-Xin; Jin, Ji-Kang; Tian, Shi-Kai

    2016-08-01

    An unprecedented application of trifluoromethanesulfonyl hydrazides as trifluoromethylating agents has been demonstrated in two vicinal difunctionalization reactions of terminal alkenes: the copper-catalyzed three-component vicinal chlorotrifluoromethylation of arylakenes with TfNHNHBoc and NaCl and the tandem trifluoromethylation/cyclization of N-arylacrylamides with TfNHNHBoc. The reactions proceeded in the presence of inexpensive oxidants under mild conditions and provided a range of structurally diverse trifluoromethyl-containing compounds with high regioselectivity. PMID:27414955

  7. An innovative catalyst system for slurry-phase Fischer-Tropsch synthesis: Cobalt plus a water-gas-shift catalyst

    SciTech Connect

    Satterfield, C.N.; Yates, I.C.; Chanenchuk, C.

    1991-07-01

    The feasibility of using a mechanical mixture of a Co/MgO/SiO{sub 2} Fischer-Tropsch catalyst and a Cu-ZnO/Al{sub 2}O{sub 3} water-gas-shift (WGS) catalyst for hydrocarbon synthesis in a slurry reactor has been established. Such a mixture can combine the superior product distribution from cobalt with the high activity for the WGS reaction characteristic of iron. Weight ratios of Co/MgO/SiO{sub 2} to Cu-ZnO/Al{sub 2}O{sub 3} of 0.27 and 0.51 for the two catalysts were studied at 240{degrees}C, 0.79 MPa, and in situ H{sub 2}/CO ratios between 0.8 and 3.0. Each catalyst mixture showed stable Fischer-Tropsch activity for about 400 hours-on-stream at a level comparable to the cobalt catalyst operating alone. The Cu-ZnO/Al{sub 2}O{sub 3} catalyst exhibited a very slow loss of activity under these conditions, but when operated alone it was stable in a slurry reactor at 200--220{degrees}C, 0.79--1.48 MPa, and H{sub 2}/CO in situ ratios between 1.0 and 2.0. The presence of the water-gas-shift catalyst did not affect the long-term stability of the primary Fischer-Tropsch selectivity, but did increase the extent of secondary reactions, such as l-alkene hydrogenation and isomerization.

  8. The Pressure Dependency of Stabilized Criegee Intermediate Yields of Selected Ozone-Alkene Reactions

    NASA Astrophysics Data System (ADS)

    Hakala, J. P.; Donahue, N. M.

    2014-12-01

    Stabilized Criegee Intermediates (SCI) play an important role as an oxidizing species in atmospheric reactions. The ozonolysis of alkenes in the atmosphere, i.e. the mechanism by which the SCIs are produced, is a major pathway to the formation of Secondary Organic Aerosols (SOA) in the atmosphere. Just how much SCIs contribute to the SOA formation is not well known and fundamental research in the kinetics of SCI formation need to be performed to shed light on this mystery. The alkene ozonolysis is highly exothermic reaction, so a third body is needed for stabilizing the SCI, thus making the SCI yield pressure dependent. We studied the production of SCIs at different pressures by studying their ability to oxidize sulfur dioxide in a pressure controlled flow reactor. We used a mixture of ultra-high purity nitrogen, oxygen, and a selective scavenger for hydroxyl radical (OH) as a carrier gas, and injected a mixture of nitrogen, sulfur dioxide and selected alkene to the center of the flow for ozonolysis to take place. With the OH radical scavenged, the SCI yield of the reaction was measured by measuring the amount of sulfuric acid formed in the reaction between SCI and sulfur dioxide with a Chemical Ionization Mass Spectrometer (CIMS). This work was supported by NASA/ROSES grant NNX12AE54G to CMU and Academy of Finland Center of Excellence project 1118615.

  9. 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

  10. Difunctionalization of Alkenes Using 1-Chloro-1,2-benziodoxol-3-(1H)-one.

    PubMed

    Egami, Hiromichi; Yoneda, Takahiro; Uku, Minako; Ide, Takafumi; Kawato, Yuji; Hamashima, Yoshitaka

    2016-05-20

    Difunctionalization of alkenes with 1-chloro-1,2-benziodoxol-3-(1H)-one (1) was investigated. Various additional nucleophiles were tested, and oxychlorination, dichlorination, azidochlorination, chlorothiocyanation, and iodoesterfication were demonstrated. The oxychlorination product was obtained efficiently when the reaction was operated in water. Dichlorination occurred in the presence of a Lewis basic promoter, such as 4-phenylpyridine N-oxide, as an additive. The reaction with in situ-generated azido anion afforded azidochlorinated compounds with a chlorine atom at the terminal position, while the reaction with trimethylsilyl isothiocyanate produced chlorothiocyanation adducts with a chlorine atom at the benzylic position. On the other hand, when 1 was treated with tetra-n-butylammonium iodide prior to the addition of alkenes, only iodoesterification occurred selectively. These mild reactions enable convenient site-selective difunctionalizations of substrates having two alkene moieties. NMR experiments suggested that the electrophilic reactive species in each reaction varied depending on the nature of the added nucleophile. PMID:27100051

  11. Ru Catalyzed Alkene-Alkyne Coupling. Total Synthesis of Amphidinolide P

    PubMed Central

    Trost, Barry M.; Papillon, Julien P. N.; Nussbaumer, Thomas

    2008-01-01

    A coordinatively unsaturated ruthenium complex catalyzed the formation of a carbon-carbon bond between two judiciously chosen alkene and alkyne partners in good yield, and in a chemo- and regioselective fashion, in spite of the significant degree of unsaturation of the substrates. The resulting 1,4-diene forms the backbone of the cytotoxic marine natural product amphidinolide P. The alkene partner was rapidly assembled from (R)-glycidyl tosylate, which served as a linchpin in a one-flask, sequential three-components coupling process using vinyllithium and a vinyl cyanocuprate. The synthesis of the alkyne partner made use of an unusual anti-selective addition under chelation control conditions of an allyltin reagent derived from tiglic acid. In addition, a remarkably E-selective E2 process using the azodicarboxylate-triphenylphosphine system is featured. Also featured is the first example of the use of a β-lactone as a thermodynamic spring to effect macrolactonization. The oxetanone ring was thus used as a productive protecting group that increased the overall efficiency of this total synthesis. This work was also an opportunity to further probe the scope of the ruthenium-catalyzed alkene-alkyne coupling, in particular using enynes, and studies using various functionalized substrates are described. PMID:16351124

  12. 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

  13. In Situ Formation of Pyridyl-Functionalized Poly(3-hexylthiophene)s via Quenching of the Grignard Metathesis Polymerization: Toward Ligands for Semiconductor Quantum Dots

    SciTech Connect

    Kochemba, William Michael; Pickel, Deanna L; Sumpter, Bobby G; Chen, Jihua; Kilbey, II, S Michael

    2012-01-01

    The synthesis of well-defined, end-functional poly(3-hexylthiophene)s (P3HTs) by in situ quenching of the Grignard metathesis (GRIM) polymerization is complicated by the extreme tendency to favor difunctional products in all but a few cases. A facile one-pot method for preparing 2-pyridyl and 3-pyridyl P3HTs with high abundance of monofunctional products is established via an examination of the kinetics of the end-functionalization quenching reaction with lithium chloride complexes of 2- and 3-pyridyl Grignard reagents. Density functional theory calculations guide the selection of pyridine as the end group, which provides the capacity to ligate cadmium selenide (CdSe) nanocrystals and arrests aggregation upon thermal annealing when dispersed in a P3HT matrix. The relative abundances of various end-functional products, as ascertained by high-resolution matrix assisted laser desorption ionization time-of-flight mass spectrometry, can be altered through the use of 1-pentene as an additive: GRIM polymerizations quenched with 3-pyridyl and 2-pyridyl Grignard reagents show 5% and 18% abundances of difunctional, pyridyl-capped P3HTs, respectively, when 1-pentene is present at 1000:1 relative to the nickel catalyst. This represents a significant improvement compared to quenching with aryl Grignard reagents, where difunctional products predominate. The ability to manipulate end group compositions coupled with the propensity of pyridyl-functionalized P3HTs to ligate semiconductor quantum dots (SQDs) opens new possibilities for tuning the morphology of conjugated polymer/SQD blends.

  14. Low-temperature synthesis of actinide tetraborides by solid-state metathesis reactions

    DOEpatents

    Lupinetti, Anthony J.; Garcia, Eduardo; Abney, Kent D.

    2004-12-14

    The synthesis of actinide tetraborides including uranium tetraboride (UB.sub.4), plutonium tetraboride (PuB.sub.4) and thorium tetraboride (ThB.sub.4) by a solid-state metathesis reaction are demonstrated. The present method significantly lowers the temperature required to .ltoreq.850.degree. C. As an example, when UCl.sub.4 is reacted with an excess of MgB.sub.2, at 850.degree. C., crystalline UB.sub.4 is formed. Powder X-ray diffraction and ICP-AES data support the reduction of UCl.sub.3 as the initial step in the reaction. The UB.sub.4 product is purified by washing water and drying.

  15. Molecular Motion of the Junction Points in Model Networks Prepared by Acyclic Triene Metathesis.

    PubMed

    da Silva, Lucas Caire; Bowers, Clifford R; Graf, Robert; Wagener, Kenneth B

    2016-03-01

    The junction dynamics in a selectively deuterated model polymer network containing junctions on every 21st chain carbon is studied by solid state (2) H echo NMR. Polymer networks are prepared via acyclic triene metathesis of deuteron-labeled symmetric trienes with deuteron probes precisely placed at the alpha carbon relative to the junction point. The effect of decreasing the cross-link density on the junction dynamics is studied by introduction of polybutadiene chains in-between junctions. The networks are characterized by swelling, gel content, and solid state (1) H MAS NMR. Line shape analysis of the (2) H quadrupolar echo spectra reveals that the degree of motion anisotropy and the distribution of motion correlation times depend on the cross-link density and structural heterogeneity of the polymer networks. A detailed model of the junction dynamics at different temperatures is proposed and explained in terms of the intermolecular cooperativity in densely-packed systems. PMID:26787457

  16. C18:1 Methyl Ester Metathesis in [bmim][X] Type Ionic Liquids

    PubMed Central

    Thomas, Priya A.; Marvey, Bassie B.

    2009-01-01

    The efficacy of [bmim][X] ionic liquids (ILs) (X = PF6−, BF4− and NTf2−) as reaction media for methyl oleate metathesis was compared with that of conventional organic solvents (PhCl, PhMe, DCM and DCE) using the well-defined first and second generation Grubbs precatalysts, RuCl2(PCy3)(L)(=CHPh) (L = PCy3 or H2IMes). Best catalytic performance, with excellent selectivity (>98%) at moderate reaction temperatures, was achieved in [bmim][X] ILs compared to conventional solvents. The effects of anion, reaction temperature, solvent polarity, solvent viscosity, and ligand-anion interaction on the reaction are also addressed. PMID:20087475

  17. Iterative Reductive Aromatization/Ring-Closing Metathesis Strategy toward the Synthesis of Strained Aromatic Belts.

    PubMed

    Golder, Matthew R; Colwell, Curtis E; Wong, Bryan M; Zakharov, Lev N; Zhen, Jingxin; Jasti, Ramesh

    2016-05-25

    The construction of all sp(2)-hybridized molecular belts has been an ongoing challenge in the chemistry community for decades. Despite numerous attempts, these double-stranded macrocycles remain outstanding synthetic challenges. Prior approaches have relied on late-state oxidations and/or acid-catalyzed processes that have been incapable of accessing the envisaged targets. Herein, we describe the development of an iterative reductive aromatization/ring-closing metathesis approach. Successful syntheses of nanohoop targets containing benzo[k]tetraphene and dibenzo[c,m]pentaphene moieties not only provide proof of principle that aromatic belts can be derived by this new strategy but also represent some of the largest aromatic belt fragments reported to date. PMID:27133789

  18. Synthesis of Carbazole Alkaloids by Ring-Closing Metathesis and Ring Rearrangement-Aromatization.

    PubMed

    Dhara, Kalyan; Mandal, Tirtha; Das, Joydeb; Dash, Jyotirmayee

    2015-12-21

    Aprocess for the assembly of carbazole alkaloids has been developed on the basis of ring-closing metathesis (RCM) and ringrearrangement-aromatization (RRA) as the key steps. This method is based on allyl Grignard addition to isatin derivatives to provide smooth access to 2,2-diallyl 3-oxindole derivatives through a 1,2-allyl shift. The diallyl derivatives were used as RCM precursors to afford a novel class of spirocyclopentene-3-oxindole derivatives, which underwent a novel RRA reaction to afford carbazole derivatives. The synthetic sequence to carbazoles was shortened by combining the RCM and RRA steps in an orthogonal tandem catalytic process. The utility of this methodology was further demonstrated by the straightforward synthesis of carbazole alkaloids, including amukonal derivative, girinimbilol, heptaphylline, and bis(2-hydroxy-3-methylcarbazole). PMID:26768698

  19. Ru-Catalyzed Isomerization Provides Access to Alternating Copolymers via Ring-Opening Metathesis Polymerization

    PubMed Central

    2016-01-01

    We describe an isomerization–alternating ROMP protocol that gives linear copolymers with rigorous sequence alternation. Bicyclo[4.2.0]oct-7-ene-7-carboxamides of primary amines are isomerized in the presence of (3-BrPyr)2Cl2(H2IMes)Ru=CHPh to the corresponding bicyclo[4.2.0]oct-1(8)-ene-8-carboxamides in which the olefinic bond is tetrasubstituted. The isomerized amides undergo alternating ring-opening metathesis polymerization with cyclohexene to provide soluble and linear copolymers with molecular weights up to ∼130 kDa. This process provides efficient entry to strictly alternating copolymers that can display diverse functional groups. PMID:26243969

  20. Photoluminescence study of Tb3+ doped CaCO3 synthesized by solid state metathesis

    NASA Astrophysics Data System (ADS)

    Muke, A. M.; Ugemuge, N. S.; Moharil, S. V.

    2016-05-01

    Conventional solid-state reaction or simple solution precipitation techniques suffer from several limitations, i.e. a high processing temperature, relatively high preparation cost and more time of preparation, highly complicated synthesis, in-stoichiometric compositions and poor crystallinity. Preparation of inorganic phosphors by microwave assisted Solid state metathesis is one of the superior methods of synthesis. Time duration required for synthesis by microwave assisted synthesis is relatively low. The required reaction temperature can be attempted using domestic microwave oven with consumption of relatively low energy. CaCO3 is one of the most abundant biological minerals in nature and has found many important applications in industry, such as pigments, paper makings, plastics, rubbers, and so on.