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Sample records for amine catalyzed silica

  1. Understanding amine catalyzed silica polymerization : diatoms as bioarchitects.

    SciTech Connect

    Spoerke, Erik David; Aubry, Sylvie; Lane, Pamela; Robinson, David B; Bauer, Christina A.; Zendejas, Frank; Tran, Huu; Lane, Todd W.; Simmons, Blake Alexander

    2007-10-01

    Current state-of-the-art biomimetic methodologies employed worldwide for the realization of self-assembled nanomaterials are adequate for certain unique applications, but a major breakthrough is needed if these nanomaterials are to obtain their true promise and potential. These routes typically utilize a 'top-down' approach in terms of controlling the nucleation, growth, and deposition of structured nanomaterials. Most of these techniques are inherently limited to primarily 2D and simple 3D structures, and are therefore limited in their ultimate functionality and field of use. Zeolites, one of the best-known and understood synthetic silica structures, typically possess highly ordered silica domains over very small length scales. The development of truly organized and hierarchical zeolites over several length scales remains an intense area of research world wide. Zeolites typically require high-temperature and complex synthesis routes that negatively impact certain economic parameters and, therefore, the ultimate utility of these materials. Nonetheless, zeolite usage is in the tons per year worldwide and is quickly becoming ubiquitous in its applications. In addition to these more mature aspects of current practices in materials science, one of the most promising fields of nanotechnology lies in the advent and control of biologically self-assembled materials, especially those involved with silica and other ceramics such as hydroxyapatite. Nature has derived, through billions of years of evolutionary steps, numerous methods by which fault-tolerant and mechanically robust structures can be created with exquisite control and precision at relatively low temperature ranges and pressures. Diatoms are one of the best known examples that exhibit this degree of structure and control known that is involved with the biomineralization of silica. Diatoms are eukaryotic algae that are ubiquitous in marine and freshwater environments. They are a dominant form of phytoplankton

  2. Amine catalyzed condensation of tetraethylorthosilicate

    NASA Technical Reports Server (NTRS)

    Jones, S.

    2001-01-01

    The catalysis of the condensation of hydrolyzed metal alkoxides by amines has been mentioned in the literature, but there has been no systematic study of their influence on the rate of the condensation reaction of the alkoxide and the microstructure of the resultant gel.

  3. Bulk Gold-Catalyzed Reactions of Isocyanides, Amines, and Amine N-Oxides

    SciTech Connect

    Klobukowski, Erik; Angelici, Robert; Woo, Keith L.

    2012-01-26

    Bulk gold powder (5–50 μm particles) catalyzes the reactions of isocyanides with amines and amine N-oxides to produce ureas. The reaction of n-butyl isocyanide (nBu–N≡C) with di-n-propylamine and N-methylmorpholine N-oxide in acetonitrile, which was studied in the greatest detail, produced 3-butyl-1,1-dipropylurea (O═C(NHnBu)(NnPr2)) in 99% yield at 60 °C within 2 h. Sterically and electronically different isocyanides, amines, and amine N-oxides react successfully under these conditions. Detailed studies support a two-step mechanism that involves a gold-catalyzed reaction of adsorbed isocyanide with the amine N-oxide to form an isocyanate (RN═C═O), which rapidly reacts with the amine to give the urea product. These investigations show that bulk gold, despite its reputation for poor catalytic activity, is capable of catalyzing these reactions.

  4. Acid-catalyzed dehydrogenation of amine-boranes

    DOEpatents

    Stephens, Frances Helen; Baker, Ralph Thomas

    2010-01-12

    A method of dehydrogenating an amine-borane using an acid-catalyzed reaction. The method generates hydrogen and produces a solid polymeric [R.sup.1R.sup.2B--NR.sup.3R.sup.4].sub.n product. The method of dehydrogenating amine-boranes may be used to generate H.sub.2 for portable power sources.

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

    PubMed Central

    Liwosz, Timothy W.; Chemler, Sherry R.

    2014-01-01

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

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

    PubMed

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

    2016-03-18

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

  7. Mesoporous Silica: A Suitable Adsorbent for Amines

    PubMed Central

    2009-01-01

    Mesoporous silica with KIT-6 structure was investigated as a preconcentrating material in chromatographic systems for ammonia and trimethylamine. Its adsorption capacity was compared to that of existing commercial materials, showing its increased adsorption power. In addition, KIT-6 mesoporous silica efficiently adsorbs both gases, while none of the employed commercial adsorbents did. This means that KIT-6 Mesoporous silica may be a good choice for integrated chromatography/gas sensing micro-devices. PMID:20628459

  8. Microwave assisted N-alkylation of amine functionalized crystal-like mesoporous phenylene-silica.

    PubMed

    Lourenço, Mirtha A O; Siegel, Renée; Mafra, Luís; Ferreira, Paula

    2013-04-28

    N-alkylation reaction of amine functionalized phenylene moieties in crystal-like mesoporous silica is successfully achieved with about 87% of conversion in two reaction cycles. A potassium iodide catalyzed method commonly used for the selective N-monoalkylation of aniline is adapted and optimized to the N-monoalkylation reactions of the amine functionalized periodic mesoporous phenylene-silica (NH2-PMO) under microwave irradiation with preservation of the ordered mesostructure and of the crystal-like molecular scale periodicity of the material. This functionalization opens an avenue for the preparation of new materials with different amino-alkyl groups specially designed for a desired application, namely on the adsorption or catalytic fields.

  9. Biaryl Phosphine Ligands in Palladium-Catalyzed Amination

    PubMed Central

    Surry, David S.

    2012-01-01

    Palladium-catalyzed amination of aryl halides has undergone rapid development in the last 12 years. This has been largely driven by implementation of new classes of ligands. Biaryl phosphines have proven to provide especially active catalysts in this context. This review discusses the applications that these catalysts have found in C-N cross-coupling in heterocycle synthesis, pharmaceuticals, materials science and natural product synthesis. PMID:18663711

  10. Iron-catalyzed aromatic amination for nonsymmetrical triarylamine synthesis.

    PubMed

    Hatakeyama, Takuji; Imayoshi, Ryuji; Yoshimoto, Yuya; Ghorai, Sujit K; Jin, Masayoshi; Takaya, Hikaru; Norisuye, Kazuhiro; Sohrin, Yoshiki; Nakamura, Masaharu

    2012-12-19

    Novel iron-catalyzed amination reactions of various aryl bromides have been developed for the synthesis of diaryl- and triarylamines. The key to the success of this protocol is the use of in situ generated magnesium amides in the presence of a lithium halide, which dramatically increases the product yield. The present method is simple and free of precious and expensive metals and ligands, thus providing a facile route to triarylamines, a recurrent core unit in organic electronic materials as well as pharmaceuticals.

  11. Lactoperoxidase-catalyzed activation of carcinogenic aromatic and heterocyclic amines.

    PubMed

    Gorlewska-Roberts, Katarzyna M; Teitel, Candee H; Lay, Jackson O; Roberts, Dean W; Kadlubar, Fred F

    2004-12-01

    Lactoperoxidase, an enzyme secreted from the human mammary gland, plays a host defensive role through antimicrobial activity. It has been implicated in mutagenic and carcinogenic activation in the human mammary gland. The potential role of heterocyclic and aromatic amines in the etiology of breast cancer led us to examination of the lactoperoxidase-catalyzed activation of the most commonly studied arylamine carcinogens: 2-amino-1-methyl-6-phenylimidazo[4,5-b]-pyridine (PhIP), benzidine, 4-aminobiphenyl (ABP), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx). In vitro activation was performed with lactoperoxidase (partially purified from bovine milk or human milk) in the presence of hydrogen peroxide and calf thymus DNA. Products formed during enzymatic activation were monitored by HPLC with ultraviolet and radiometric detection. Two of these products were characterized as hydrazo and azo derivatives by means of mass spectrometry. The DNA binding level of 3H- and 14C-radiolabeled amines after peroxidase-catalyzed activation was dependent on the hydrogen peroxide concentration, and the highest levels of carcinogen binding to DNA were observed at 100 microM H2O2. Carcinogen activation and the level of binding to DNA were in the order of benzidine > ABP > IQ > MeIQx > PhIP. One of the ABP adducts was identified, and the level at which it is formed was estimated to be six adducts/10(5) nucleotides. The susceptibility of aromatic and heterocyclic amines for lactoperoxidase-catalyzed activation and the binding levels of activated products to DNA suggest a potential role of lactoperoxidase-catalyzed activation of carcinogens in the etiology of breast cancer.

  12. Dirhodium-catalyzed C-H arene amination using hydroxylamines.

    PubMed

    Paudyal, Mahesh P; Adebesin, Adeniyi Michael; Burt, Scott R; Ess, Daniel H; Ma, Zhiwei; Kürti, László; Falck, John R

    2016-09-01

    Primary and N-alkyl arylamine motifs are key functional groups in pharmaceuticals, agrochemicals, and functional materials, as well as in bioactive natural products. However, there is a dearth of generally applicable methods for the direct replacement of aryl hydrogens with NH2/NH(alkyl) moieties. Here, we present a mild dirhodium-catalyzed C-H amination for conversion of structurally diverse monocyclic and fused aromatics to the corresponding primary and N-alkyl arylamines using NH2/NH(alkyl)-O-(sulfonyl)hydroxylamines as aminating agents; the relatively weak RSO2O-N bond functions as an internal oxidant. The methodology is operationally simple, scalable, and fast at or below ambient temperature, furnishing arylamines in moderate-to-good yields and with good regioselectivity. It can be readily extended to the synthesis of fused N-heterocycles. PMID:27609890

  13. Dirhodium Catalyzed C-H Arene Amination using Hydroxylamines

    PubMed Central

    Paudyal, Mahesh P.; Adebesin, Adeniyi Michael; Burt, Scott R.; Ess, Daniel H.; Ma, Zhiwei; Kürti, László; Falck, John R.

    2016-01-01

    Primary and N-alkyl arylamine motifs are key functional groups in pharmaceuticals, agrochemicals and functional materials as well as in bioactive natural products. However, there is a dearth of generally applicable methods for the direct replacement of aryl hydrogens with –NH2/-NH-alkyl moieties. Here, we present a mild dirhodium-catalyzed C-H amination for conversion of structurally diverse monocyclic and fused aromatics to the corresponding primary and N-alkyl arylamines using either NH2/NHalkyl-O-(sulfonyl)hydroxylamines as aminating agents; the relatively weak RSO2O-N bond functions as an internal oxidant. The methodology is operationally simple, scalable, and fast at or below ambient temperature, furnishing arylamines in moderate-to-good yields and with good regioselectivity. It can be readily extended to the synthesis of fused N-heterocycles. PMID:27609890

  14. Rhodium-Catalyzed Regiodivergent Hydrothiolation of Allyl Amines and Imines.

    PubMed

    Kennemur, Jennifer L; Kortman, Gregory D; Hull, Kami L

    2016-09-14

    The regiodivergent Rh-catalyzed hydrothiolation of allyl amines and imines is presented. Bidentate phosphine ligands with larger natural bite angles (βn ≥ 99°), for example, DPEphos, dpph, or L1, promote a Markovnikov-selective hydrothiolation in up to 88% yield and >20:1 regioselectivity. Conversely, when smaller bite angle ligands (βn ≤ 86°), for example, dppbz or dppp, are employed, the anti-Markovnikov product is formed in up to 74% yield and >20:1 regioselectivity. Initial mechanistic investigations are performed and are consistent with an oxidative addition/olefin insertion/reductive elimination mechanism for each regioisomeric pathway. We hypothesize that the change in regioselectivity is an effect of diverging coordination spheres to favor either Rh-S or Rh-H insertion to form the branched or linear isomer, respectively. PMID:27547858

  15. Molecular Dynamics Simulations of Aldol Condensation Catalyzed by Alkylamine-Functionalized Crystalline Silica Surfaces.

    PubMed

    Kim, Ki Chul; Moschetta, Eric G; Jones, Christopher W; Jang, Seung Soon

    2016-06-22

    Molecular dynamics simulations are performed to investigate the cooperatively catalyzed aldol condensation between acetone and 4-nitrobenzaldehyde on alkylamine (or alkylenamine)-grafted silica surfaces, focusing on the mechanism of the catalytic activation of the acetone and 4-nitrobenzaldehyde by the acidic surface silanols followed by the nucleophilic attack of the basic amine functional group toward the activated reactant. From the analysis of the correlations between the catalytically active acid-base sites and reactants, it is concluded that the catalytic cooperativity of the acid-base pair can be affected by two factors: (1) the competition between the silanol and the amine (or enamine) to form a hydrogen bond with a reactant and (2) the flexibility of the alkylamine (or alkylenamine) backbone. Increasing the flexibility of the alkylamine facilitates the nucleophilic attack of the amine on the reactants. From the molecular dynamics simulations, it is found that C3 propylamine and C4 butylamine linkers exhibit the highest probability of reaction, which is consistent with the experimental observation that the activity of the aldol reaction on mesoporous silica depends on the length of alkylamine grafted on the silica surface. This simulation work serves as a pioneering study demonstrating how the molecular simulation approach can be successfully employed to investigate the cooperative catalytic activity of such bifunctional acid-base catalysts.

  16. Palladium-catalyzed hydroaminocarbonylation of alkenes with amines: a strategy to overcome the basicity barrier imparted by aliphatic amines.

    PubMed

    Zhang, Guoying; Gao, Bao; Huang, Hanmin

    2015-06-22

    A novel and efficient palladium-catalyzed hydroaminocarbonylation of alkenes with aminals has been developed under mild reaction conditions, and allows the synthesis of a wide range of N-alkyl linear amides in good yields with high regioselectivity. On the basis of this method, a cooperative catalytic system operating by the synergistic combination of palladium, paraformaldehyde, and acid was established for promoting the hydroaminocarbonylation of alkenes with both aromatic and aliphatic amines, which do not react well under conventional palladium-catalyzed hydroaminocarbonylation.

  17. Synthesis of new N-analogous corollosporine derivatives with antibacterial activity by laccase-catalyzed amination.

    PubMed

    Mikolasch, Annett; Hessel, Susanne; Salazar, Manuela Gesell; Neumann, Helfried; Manda, Katrin; Gōrdes, Dirk; Schmidt, Enrico; Thurow, Kerstin; Hammer, Elke; Lindequist, Ulrike; Beller, Matthias; Schauer, Frieder

    2008-06-01

    Corollosporine isolated from the marine fungus Corollospora maritima and N-analogous corollosporines are antimicrobial substances. Owing to the basic structure of the N-analogous corollosporines, they have become an attractive target for laccase-catalyzed derivatisation. In this regard we report on the straightforward laccase-catalyzed amination of dihydroxylated arenes with N-analogous corollosporines. In biological assays the obtained amination products are more active than the parent compounds.

  18. Amine-bis(phenolate) Iron(III)-Catalyzed Formal Hydroamination of Olefins.

    PubMed

    Zhu, Kailong; Shaver, Michael P; Thomas, Stephen P

    2016-04-01

    A practical synthesis of highly functionalized amines by the formal hydroamination reaction of alkenes with nitroarenes catalyzed by an air stable amine-bis(phenolate) iron(III) complex is reported. The reaction uses an easily handled silane, low catalyst loadings, and mild reaction conditions. A wide range of substrates are transformed with synthetically useful yields (21 examples). PMID:26864731

  19. Boron-Catalyzed N-Alkylation of Amines using Carboxylic Acids.

    PubMed

    Fu, Ming-Chen; Shang, Rui; Cheng, Wan-Min; Fu, Yao

    2015-07-27

    A boron-based catalyst was found to catalyze the straightforward alkylation of amines with readily available carboxylic acids in the presence of silane as the reducing agent. Various types of primary and secondary amines can be smoothly alkylated with good selectivity and good functional-group compatibility. This metal-free amine alkylation was successfully applied to the synthesis of three commercial medicinal compounds, Butenafine, Cinacalcet. and Piribedil, in a one-pot manner without using any metal catalysts. PMID:26150397

  20. Boron-Catalyzed N-Alkylation of Amines using Carboxylic Acids.

    PubMed

    Fu, Ming-Chen; Shang, Rui; Cheng, Wan-Min; Fu, Yao

    2015-07-27

    A boron-based catalyst was found to catalyze the straightforward alkylation of amines with readily available carboxylic acids in the presence of silane as the reducing agent. Various types of primary and secondary amines can be smoothly alkylated with good selectivity and good functional-group compatibility. This metal-free amine alkylation was successfully applied to the synthesis of three commercial medicinal compounds, Butenafine, Cinacalcet. and Piribedil, in a one-pot manner without using any metal catalysts.

  1. Silanol-assisted carbinolamine formation in an amine-functionalized mesoporous silica surface: Theoretical investigation by fragmentation methods

    DOE PAGESBeta

    de Lima Batista, Ana P.; Zahariev, Federico; Slowing, Igor I.; Braga, Ataualpa A. C.; Ornellas, Fernando R.; Gordon, Mark S.

    2015-12-15

    The aldol reaction catalyzed by an amine-substituted mesoporous silica nanoparticle (amine-MSN) surface was investigated using a large molecular cluster model (Si392O958C6NH361) combined with the surface integrated molecular orbital/molecular mechanics (SIMOMM) and fragment molecular orbital (FMO) methods. Three distinct pathways for the carbinolamine formation, the first step of the amine-catalyzed aldol reaction, are proposed and investigated in order to elucidate the role of the silanol environment on the catalytic capability of the amine-MSN material. The computational study reveals that the most likely mechanism involves the silanol groups actively participating in the reaction, forming and breaking covalent bonds in the carbinolamine step.more » Furthermore, the active participation of MSN silanol groups in the reaction mechanism leads to a significant reduction in the overall energy barrier for the carbinolamine formation. In addition, a comparison between the findings using a minimal cluster model and the Si392O958C6NH361 cluster suggests that the use of larger models is important when heterogeneous catalysis problems are the target.« less

  2. Silanol-assisted carbinolamine formation in an amine-functionalized mesoporous silica surface: Theoretical investigation by fragmentation methods

    SciTech Connect

    de Lima Batista, Ana P.; Zahariev, Federico; Slowing, Igor I.; Braga, Ataualpa A. C.; Ornellas, Fernando R.; Gordon, Mark S.

    2015-12-15

    The aldol reaction catalyzed by an amine-substituted mesoporous silica nanoparticle (amine-MSN) surface was investigated using a large molecular cluster model (Si392O958C6NH361) combined with the surface integrated molecular orbital/molecular mechanics (SIMOMM) and fragment molecular orbital (FMO) methods. Three distinct pathways for the carbinolamine formation, the first step of the amine-catalyzed aldol reaction, are proposed and investigated in order to elucidate the role of the silanol environment on the catalytic capability of the amine-MSN material. The computational study reveals that the most likely mechanism involves the silanol groups actively participating in the reaction, forming and breaking covalent bonds in the carbinolamine step. Furthermore, the active participation of MSN silanol groups in the reaction mechanism leads to a significant reduction in the overall energy barrier for the carbinolamine formation. In addition, a comparison between the findings using a minimal cluster model and the Si392O958C6NH361 cluster suggests that the use of larger models is important when heterogeneous catalysis problems are the target.

  3. Iron-Catalyzed Oxyfunctionalization of Aliphatic Amines at Remote Benzylic C-H Sites.

    PubMed

    Mbofana, Curren T; Chong, Eugene; Lawniczak, James; Sanford, Melanie S

    2016-09-01

    We report the development of an iron-catalyzed method for the selective oxyfunctionalization of benzylic C(sp(3))-H bonds in aliphatic amine substrates. This transformation is selective for benzylic C-H bonds that are remote (i.e., at least three carbons) from the amine functional group. High site selectivity is achieved by in situ protonation of the amine with trifluoroacetic acid, which deactivates more traditionally reactive C-H sites that are α to nitrogen. The scope and synthetic utility of this method are demonstrated via the synthesis and derivatization of a variety of amine-containing, biologically active molecules. PMID:27529646

  4. Cobalt-Catalyzed N-Alkylation of Amines with Alcohols.

    PubMed

    Zhang, Guoqi; Yin, Zhiwei; Zheng, Shengping

    2016-01-15

    A well-defined nonprecious metal cobalt(II) catalyst based on a pincer PNP ligand has been employed for the efficient N-alkylation of both aromatic and aliphatic amines with alcohols. A subtle change of reaction conditions (simply adding 4 Å molecular sieves) was observed to readily switch the resulting products (amines vs imines) with high chemoselectivity. A range of alcohols and amines including both aromatic and aliphatic substrates were efficiently converted to secondary amines in good-to-excellent yields when 2 mol % cobalt catalyst was used. Additional experiments indicate that a hydrogen-borrowing mechanism is responsible for the tandem acceptorless dehydrogenation/condensation/hydrogenation process. PMID:26695594

  5. Copper(I)-catalyzed amination of aryl halides in liquid ammonia.

    PubMed

    Ji, Pengju; Atherton, John H; Page, Michael I

    2012-09-01

    The amination of aryl halides in liquid ammonia (LNH(3)) is catalyzed by a copper(I) salt/ascorbate system to yield primary aromatic amines in good to excellent yields. The low concentrations of catalyst required and the ease of product isolation suggest that this process has potential industrial applications. Commonly used ligands for analogous metal-catalyzed reactions are not effective. The rate of amination of iodobenzene in liquid ammonia is first order in copper(I) catalyst concentration. The small Hammett ρ = 0.49 for the amination of 4-substituted iodobenzenes in liquid ammonia at 25 °C indicates that the C-I bond is not significantly broken in the transition state structure and that there is a small generation of negative charge in the aryl ring, which is compatible with the oxidative addition of the copper ion being rate limiting. PMID:22849292

  6. Silver-catalyzed synthesis of amides from amines and aldehydes

    DOEpatents

    Madix, Robert J; Zhou, Ling; Xu, Bingjun; Friend, Cynthia M; Freyschlag, Cassandra G

    2014-11-18

    The invention provides a method for producing amides via the reaction of aldehydes and amines with oxygen adsorbed on a metallic silver or silver alloy catalyst. An exemplary reaction is shown in Scheme 1: (I), (II), (III). ##STR00001##

  7. Copper-catalyzed electrophilic amination of sodium sulfinates at room temperature.

    PubMed

    Zhu, Haibo; Shen, Yajing; Deng, Qinyue; Tu, Tao

    2015-11-28

    By using O-benzoyl hydroxylamines as amine sources, the first convenient copper-catalyzed electrophilic amination of sodium sulfinates has been realized. Even with 2 mol% catalyst loading, the protocol provided an efficient and straightforward synthesis of a broad range of functional sulfonamides under ambient reaction conditions without an additional base and ligand. Based on the control experiments, a plausible mechanism was proposed. PMID:26419424

  8. Magnetic Silica Supported Copper: A Modular Approach to Aqueous Ullmann-type Amination of Aryl Halides

    EPA Science Inventory

    One-pot synthesis of magnetic silica supported copper catalyst has been described via in situ generated magnetic silica (Fe3O4@SiO2); the catalyst can be used for the efficacious amination of aryl halides in aqueous medium under microwave irradiation.

  9. Platinum-Catalyzed, Terminal-Selective C(sp(3))-H Oxidation of Aliphatic Amines.

    PubMed

    Lee, Melissa; Sanford, Melanie S

    2015-10-14

    This Communication describes the terminal-selective, Pt-catalyzed C(sp(3))-H oxidation of aliphatic amines without the requirement for directing groups. CuCl2 is employed as a stoichiometric oxidant, and the reactions proceed in high yield at Pt loadings as low as 1 mol%. These transformations are conducted in the presence of sulfuric acid, which reacts with the amine substrates in situ to form ammonium salts. We propose that protonation of the amine serves at least three important roles: (i) it renders the substrates soluble in the aqueous reaction medium; (ii) it limits binding of the amine nitrogen to Pt or Cu; and (iii) it electronically deactivates the C-H bonds proximal to the nitrogen center. We demonstrate that this strategy is effective for the terminal-selective C(sp(3))-H oxidation of a variety of primary, secondary, and tertiary amines. PMID:26439251

  10. Copper-catalyzed N-arylation of amines with part-per-million catalyst loadings under air at room temperature.

    PubMed

    Xie, Ruilong; Fu, Hua; Ling, Yun

    2011-08-21

    An efficient copper-catalyzed method for N-arylation of amines has been developed with part-per-million catalyst loadings at room temperature under air. Reactions of substituted (E)-1-(2-halophenyl)alkanone oximes with aliphatic amines or aromatic amines provided the N-arylation products in good to excellent yields. PMID:21727962

  11. Cu²⁺ sequestration by amine-functionalized silica nanotubes.

    PubMed

    Ko, Young Gun; Lee, Hyun Jeong; Oh, Hyun Chul; Choi, Ung Su

    2013-09-15

    A novel method for Cu(2+) sequestration in Cu(2+) aqueous solution has been demonstrated using amine-functionalized double-walled silica nanotubes (DWSNTs). Herein, the precipitation method and the adsorption method are combined to remove Cu(2+) in the Cu(2+) aqueous solution. Primary (1°), secondary (2°), tertiary (3°), di-, tri-amines are immobilized on the surface of DWSNT as the adsorption site. The results show that the Cu(2+) adsorption amount on the amine-functionalized DWSNTs is in the following order: tri-amine>di-amine>1° amine>2° amine>3° amine. The complexed Cu(2+)s with the amine-functionalized DWSNTs become Cu(OH)2 crystals due to the reaction with OH(-)s dissociated from water. Thus, the amine-functionalized DWSNTs show the superior sequestration capacity of Cu(2+) in the Cu(2+) aqueous solution owing to the Cu(OH)2 crystals growth on them. FT-IR, FEG-SEM, HR-TEM, and XRD studies demonstrate the mechanism of the Cu(2+) adsorption and the Cu(OH)2 crystals growth. The crystallization-technique of the heavy metal ion on the amine-functionalized DWSNTs is also expected to have potential applications such as the facile synthesis of nano- and microparticles, and the metal catalyst supporter.

  12. Mechanism of Boron-Catalyzed N-Alkylation of Amines with Carboxylic Acids.

    PubMed

    Zhang, Qi; Fu, Ming-Chen; Yu, Hai-Zhu; Fu, Yao

    2016-08-01

    Mechanistic study has been carried out on the B(C6F5)3-catalyzed amine alkylation with carboxylic acid. The reaction includes acid-amine condensation and amide reduction steps. In condensation step, the catalyst-free mechanism is found to be more favorable than the B(C6F5)3-catalyzed mechanism, because the automatic formation of the stable B(C6F5)3-amine complex deactivates the catalyst in the latter case. Meanwhile, the catalyst-free condensation is constituted by nucleophilic attack and the indirect H2O-elimination (with acid acting as proton shuttle) steps. After that, the amide reduction undergoes a Lewis acid (B(C6F5)3)-catalyzed mechanism rather than a Brønsted acid (B(C6F5)3-coordinated HCOOH)-catalyzed one. The B(C6F5)3)-catalyzed reduction includes twice silyl-hydride transfer steps, while the first silyl transfer is the rate-determining step of the overall alkylation catalytic cycle. The above condensation-reduction mechanism is supported by control experiments (on both temperature and substrates). Meanwhile, the predicted chemoselectivity is consistent with the predominant formation of the alkylation product (over disilyl acetal product). PMID:27441997

  13. Amine modification of nonporous silica nanoparticles reduces inflammatory response following intratracheal instillation in murine lungs.

    PubMed

    Morris, Angie S; Adamcakova-Dodd, Andrea; Lehman, Sean E; Wongrakpanich, Amaraporn; Thorne, Peter S; Larsen, Sarah C; Salem, Aliasger K

    2016-01-22

    Amorphous silica nanoparticles (NPs) possess unique material properties that make them ideal for many different applications. However, the impact of these materials on human and environmental health needs to be established. We investigated nonporous silica NPs both bare and modified with amine functional groups (3-aminopropyltriethoxysilane (APTES)) in order to evaluate the effect of surface chemistry on biocompatibility. In vitro data showed there to be little to no cytotoxicity in a human lung cancer epithelial cell line (A549) for bare silica NPs and amine-functionalized NPs using doses based on both mass concentration (below 200μg/mL) and exposed total surface area (below 14m(2)/L). To assess lung inflammation, C57BL/6 mice were administered bare or amine-functionalized silica NPs via intra-tracheal instillation. Two doses (0.1 and 0.5mg NPs/mouse) were tested using the in vivo model. At the higher dose used, bare silica NPs elicited a significantly higher inflammatory response, as evidence by increased neutrophils and total protein in bronchoalveolar lavage (BAL) fluid compared to amine-functionalized NPs. From this study, we conclude that functionalization of nonporous silica NPs with APTES molecules reduces murine lung inflammation and improves the overall biocompatibility of the nanomaterial. PMID:26562768

  14. Alkaline-Earth-Catalyzed Dehydrocoupling of Amines and Boranes

    PubMed Central

    Liptrot, David J; Hill, Michael S; Mahon, Mary F; Wilson, Andrew S S

    2015-01-01

    Dehydrocoupling reactions between the boranes HBpin and 9-borabicyclo[3.3.1]nonane and a range of amines and anilines ensue under very mild reaction conditions in the presence of a simple β-diketiminato magnesium n-butyl precatalyst. The facility of the reactions is suggested to be a function of the Lewis acidity of the borane substrate, and is dictated by resultant pre-equilibria between, and the relative stability of, magnesium hydride and borohydride intermediates during the course of the catalysis. PMID:26360523

  15. Ruthenium-Catalyzed Methylation of Amines with Paraformaldehyde in Water under Mild Conditions.

    PubMed

    van der Waals, Dominic; Heim, Leo E; Gedig, Christian; Herbrik, Fabian; Vallazza, Simona; Prechtl, Martin H G

    2016-09-01

    Methylated amines are highly important for a variety of pharmaceutical and agrochemical applications. Existing routes for their formation result in the production of large amounts of waste or require high reaction temperatures, both of which impact the ecological and economical footprint of the methodologies. Herein, we report the ruthenium-catalyzed reductive methylation of a range of aliphatic amines, using paraformaldehyde as both substrate and hydrogen source, in combination with water. This reaction proceeds under mild aqueous reaction conditions. Additionally the use of a secondary phase for catalyst retention and recycling has been investigated with promising results.

  16. A Copper-Catalyzed Decarboxylative Amination/Hydroamination Sequence: Switchable Synthesis of Functionalized Indoles.

    PubMed

    Li, Tian-Ren; Cheng, Bei-Yi; Wang, Ya-Ni; Zhang, Mao-Mao; Lu, Liang-Qiu; Xiao, Wen-Jing

    2016-09-26

    A copper-catalyzed decarboxylative amination/hydroamination sequence of propargylic carbamates with various nucleophiles is described for the first time. It features an earth-abundant metal catalyst, mild reaction conditions, and high efficiency. Further treatments of the resultant key intermediates using an acid or a base in one pot enable the controllable and divergent synthesis of two types of functionalized indoles. Moreover, experiments to demonstrate the synthetic potential of this methodology are performed. PMID:27593696

  17. Mesoporous Silica-Supported Amidozirconium-Catalyzed Carbonyl Hydroboration

    DOE PAGESBeta

    Eedugurala, Naresh; Wang, Zhuoran; Chaudhary, Umesh; Nelson, Nicholas; Kandel, Kapil; Kobayashi, Takeshi; Slowing, Igor I.; Pruski, Marek; Sadow, Aaron D.

    2015-11-04

    The hydroboration of aldehydes and ketones using a silica-supported zirconium catalyst is reported. Reaction of Zr(NMe2)4 and mesoporous silica nanoparticles (MSN) provides the catalytic material Zr(NMe2)n@MSN. Exhaustive characterization of Zr(NMe2)n@MSN with solid-state (SS)NMR and infrared spectroscopy, as well as through reactivity studies, suggests its surface structure is primarily ≡SiOZr(NMe2)3. The presence of these nitrogen-containing zirconium sites is supported by 15N NMR spectroscopy, including natural abundance 15N NMR measurements using dynamic nuclear polarization (DNP) SSNMR. The Zr(NMe2)n@MSN material reacts with pinacolborane (HBpin) to provide Me2NBpin and the material ZrH/Bpin@MSN that is composed of interacting surface-bonded zirconium hydride and surface-bonded borane ≡SiOBpinmore » moieties in an approximately 1:1 ratio, as well as zirconium sites coordinated by dimethylamine. The ZrH/Bpin@MSN is characterized by 1H/2H and 11B SSNMR and infrared spectroscopy and through its reactivity with D2. The zirconium hydride material or the zirconium amide precursor Zr(NMe2)n@MSN catalyzes the selective hydroboration of aldehydes and ketones with HBpin in the presence of functional groups that are often reduced under hydroboration conditions or are sensitive to metal hydrides, including olefins, alkynes, nitro groups, halides, and ethers. Remarkably, this catalytic material may be recycled without loss of activity at least eight times, and air-exposed materials are catalytically active. These supported zirconium centers are robust catalytic sites for carbonyl reduction and that surface-supported, catalytically reactive zirconium hydride may be generated from zirconium-amide or zirconium alkoxide sites.« less

  18. Factors affecting the preparation and properties of electrodeposited silica thin films functionalized with amine or thiol groups.

    PubMed

    Sibottier, Emilie; Sayen, Stéphanie; Gaboriaud, Fabien; Walcarius, Alain

    2006-09-26

    Well-adherent sol-gel-derived silica films functionalized with amine or thiol groups have been electrogenerated on gold electrodes and both the deposition process and the film properties have been studied by various physicochemical techniques. Electrodeposition was achieved by combining the formation of a self-assembled "nanoglue" on the electrode surface, the sol-gel process, and the electrochemical manipulation of pH to catalyze polycondensation of the precursors. Gold electrodes pretreated with mercaptopropyltrimethoxysilane (MPTMS) were immersed in sol solutions containing the selected precursors (tetraethoxysilane, TEOS, in mixture with (3-aminopropyl)triethoxysilane, APTES, or MPTMS) where they underwent a cathodic electrolysis to generate the hydroxyl ions that are necessary to catalyze the formation of the organosilica films on the electrode surface. Special attention was given to analyze the effects of deposition time and applied potential and to compare APTES and MPTMS films. Characterization was made using quartz crystal microbalance, scanning electron microscopy, cyclic voltammetry, and atomic force microscopy (including in situ monitoring). The electrodeposition process was found to occur at two growing rates: a first slow stage giving rise to rather homogeneous, yet rough, films with thickness in the sub-mum range (increasing continuously when increasing the deposition time), which was followed by a faster gelification step resulting in much thicker (>1 microm) and rougher macroporous deposits. These two successive situations were observed independently on the applied potential except that more cathodic values led to narrower sub-microm ranges (as expected from the larger amounts of the electrogenerated hydroxyl catalyst). Thiol-functionalized silica films were deposited more rapidly than the amine ones and, for both of them, permeability to redox probe was found to decrease when increasing the film thickness because of higher resistance to mass

  19. Amine-functionalized magnetic mesoporous silica nanoparticles for DNA separation

    NASA Astrophysics Data System (ADS)

    Sheng, Wei; Wei, Wei; Li, Junjian; Qi, Xiaoliang; Zuo, Gancheng; Chen, Qi; Pan, Xihao; Dong, Wei

    2016-11-01

    We report a modified approach for the functionalized magnetic mesoporous silica nanoparticles (MMSN) using polymer microspheres incorporated with magnetic nanoparticles in the presence of cetyltrimethylammonium bromide (CTAB) and the core-shell magnetic silica nanoparticles (MSN). These particles were functionalized with amino groups via the addition of aminosilane directly to the particle sol. We then evaluate their DNA separation abilities and find the capacity of DNA binding significantly increased (210.22 μg/mg) compared with normal magnetic silica spheres (138.44 μg/mg) by using an ultraviolet and visible spectrophotometer (UV). The morphologies, magnetic properties, particle size, pore size, core-shell structure and Zeta potential are characterized by Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM), Transmission electron microscopy (TEM), Powder X-ray diffraction (XRD), and dynamic light scattering (DLS). This work demonstrates that our MMSN own an excellent potential application in bioseparation and drug delivery.

  20. Mesoporous Silica-Supported Amidozirconium-Catalyzed Carbonyl Hydroboration

    SciTech Connect

    Eedugurala, Naresh; Wang, Zhuoran; Chaudhary, Umesh; Nelson, Nicholas; Kandel, Kapil; Kobayashi, Takeshi; Slowing, Igor I.; Pruski, Marek; Sadow, Aaron D.

    2015-11-04

    The hydroboration of aldehydes and ketones using a silica-supported zirconium catalyst is reported. Reaction of Zr(NMe2)4 and mesoporous silica nanoparticles (MSN) provides the catalytic material Zr(NMe2)n@MSN. Exhaustive characterization of Zr(NMe2)n@MSN with solid-state (SS)NMR and infrared spectroscopy, as well as through reactivity studies, suggests its surface structure is primarily ≡SiOZr(NMe2)3. The presence of these nitrogen-containing zirconium sites is supported by 15N NMR spectroscopy, including natural abundance 15N NMR measurements using dynamic nuclear polarization (DNP) SSNMR. The Zr(NMe2)n@MSN material reacts with pinacolborane (HBpin) to provide Me2NBpin and the material ZrH/Bpin@MSN that is composed of interacting surface-bonded zirconium hydride and surface-bonded borane ≡SiOBpin moieties in an approximately 1:1 ratio, as well as zirconium sites coordinated by dimethylamine. The ZrH/Bpin@MSN is characterized by 1H/2H and 11B SSNMR and infrared spectroscopy and through its reactivity with D2. The zirconium hydride material or the zirconium amide precursor Zr(NMe2)n@MSN catalyzes the selective hydroboration of aldehydes and ketones with HBpin in the presence of functional groups that are often reduced under hydroboration conditions or are sensitive to metal hydrides, including olefins, alkynes, nitro groups, halides, and ethers. Remarkably, this catalytic material may be recycled without loss of activity at least eight times, and air-exposed materials are catalytically active. These supported zirconium centers are robust catalytic sites for carbonyl reduction and that surface-supported, catalytically reactive zirconium hydride may be generated from zirconium-amide or zirconium alkoxide sites.

  1. Palladium-Catalyzed Transannular C–H Functionalization of Alicyclic Amines

    PubMed Central

    Saper, Noam I.; Sanford, Melanie S.

    2016-01-01

    The discovery of pharmaceutical candidates is a resource-intensive enterprise that frequently requires the parallel synthesis of hundreds or even thousands of molecules. Carbon-hydrogen bonds are present in almost all pharmaceutical agents. As such, the development of selective, rapid, and efficient methods for converting carbon-hydrogen bonds into new chemical entities has the potential to dramatically streamline pharmaceutical development1,2,3,4. Saturated nitrogen-containing heterocycles (alicyclic amines) feature prominently in pharmaceuticals, including treatments for depression (paroxetine, amitifadine), diabetes (gliclazide), leukemia (alvocidib), schizophrenia (risperidone, belaperidone), and nicotine addiction (cytisine and varenicline)5. However, existing methods for the C–H functionalization of saturated nitrogen heterocycles, particularly at sites remote to nitrogen, remain extremely limited 6,7. Here we report a new approach to selectively manipulate the carbon–hydrogen bonds of alicyclic amines at sites remote to nitrogen. Our reaction leverages the boat conformation of the substrates to achieve the palladium-catalyzed amine-directed conversion of C–H bonds to C–C bonds on various alicyclic amine scaffolds. This approach is applied to the synthesis of novel derivatives of several bioactive molecules, including the top-selling smoking cessation drug varenicline (Chantix®). We anticipate that this method should prove broadly useful in medicinal chemistry. PMID:26886789

  2. Origins of the Stereoselectivity in a Thiourea-Primary Amine-Catalyzed Nazarov Cyclization.

    PubMed

    Asari, Austin H; Lam, Yu-hong; Tius, Marcus A; Houk, K N

    2015-10-14

    The origins of stereoselectivity of the Nazarov reactions of α-hydroxydivinylketones catalyzed by a vicinal thiourea-primary amine first reported by Tius have been explored with density functional theory. The electrocyclization transition structures in which the thiourea group of the catalyst donates two hydrogen bonds to the keto carbonyl group of the Nazarov reactant and the primary amine accepts a hydrogen bond from the hydroxyl group of the reactant have been modeled. The enantiomeric Nazarov transition structures, which are conventionally described by the absolute sense of conrotation of the dienone termini ("clockwise" or "counterclockwise") in the literature, are nonplanar and adopt helically chiral conformations. The interactions of these helical electrocyclization transition structures with the chiral catalyst are studied in detail. The organocatalyst is found to employ a combination of hydrogen bonding and steric effects to achieve helical recognition of the Nazarov transition state. PMID:26426475

  3. Copper(II) triflate catalyzed amination of 1,3-dicarbonyl compounds.

    PubMed

    Ton, Thi My Uyen; Himawan, Fanny; Chang, Joyce Wei Wei; Chan, Philip Wai Hong

    2012-09-17

    A method to prepare α,α-acyl amino acid derivatives efficiently by Cu(OTf)(2)+1,10-phenanthroline (1,10-phen)-catalyzed amination of 1,3-dicarbonyl compounds with PhI=NSO(2) Ar is described. The mechanism is thought to initially involve aziridination of the enolic form of the substrate, formed in situ through coordination to the Lewis acidic metal catalyst, by the putative copper-nitrene/imido species generated from the reaction of the metal catalyst with the iminoiodane source. Subsequent ring opening of the resultant aziridinol adduct under the Lewis acidic conditions then provided the α-aminated product. The utility of this method was exemplified by the enantioselective synthesis of a precursor of 3-styryl-2-benzoyl-L-alanine. PMID:22890890

  4. Kinetic mechanism and structural requirements of the amine-catalyzed decarboxylation of oxaloacetic acid.

    PubMed

    Thalji, Nabil K; Crowe, William E; Waldrop, Grover L

    2009-01-01

    The kinetic and chemical mechanism of amine-catalyzed decarboxylation of oxaloacetic acid at pH 8.0 has been reevaluated using a new and versatile assay. Amine-catalyzed decarboxylation of oxaloacetic acid proceeds via the formation of an imine intermediate, followed by decarboxylation of the intermediate and hydrolysis to yield pyruvate. The decrease in oxaloacetic acid was coupled to NADH formation by malate dehydrogenase, which allowed the rates of both initial carbinolamine formation (as part of the imination step) and decarboxylation to be determined. By comparing the rates observed for a variety of amines and, in particular, diamines, the structural and electronic requirements for diamine-catalyzed decarboxylation at pH 8.0 were identified. At pH 8.0, monoamines were found to be very poor catalysts, whereas some diamines, most notably ethylenediamine, were excellent catalysts. The results indicate that the second amino group of diamines enhances the rate of imine formation by acting as a proton shuttle during the carbinolamine formation step, which enables diamines to overcome high levels of solvation that would otherwise inhibit carbinolamine, and thus imine, formation. The presence of the second amino group may also enhance the rate of the carbinolamine dehydration step. In contrast to the findings of previous reports, the second amino group participates in the reaction by enhancing the rate of decarboxylation via hydrogen-bonding to the imine nitrogen to either stabilize the negative charge that develops on the imine during decarboxylation or preferentially stabilize the reactive imine over the unreactive enamine tautomer. These results provide insight into the precise catalytic mechanism of several enzymes whose reactions are known to proceed via an imine intermediate.

  5. Transglutaminase-catalyzed site-specific glycosidation of catalase with aminated dextran.

    PubMed

    Valdivia, Aymara; Villalonga, Reynaldo; Di Pierro, Prospero; Pérez, Yunel; Mariniello, Loredana; Gómez, Leissy; Porta, Raffaele

    2006-04-10

    An enzymatic approach, based on a transglutaminase-catalyzed coupling reaction, was investigated to modify bovine liver catalase with an end-group aminated dextran derivative. We demonstrated that catalase activity increased after enzymatic glycosidation and that the conjugate was 3.8-fold more stable to thermal inactivation at 55 degrees C and 2-fold more resistant to proteolytic degradation by trypsin. Moreover, the transglutaminase-mediated modification also improved the pharmacokinetics behavior of catalase, increasing 2.5-fold its plasma half-life time and reducing 3-fold the total clearance after its i.v. administration in rats. PMID:16446004

  6. A short scalable route to (-)-α-kainic acid using Pt-catalyzed direct allylic amination.

    PubMed

    Zhang, Ming; Watanabe, Kenji; Tsukamoto, Masafumi; Shibuya, Ryozo; Morimoto, Hiroyuki; Ohshima, Takashi

    2015-03-01

    An increased supply of scarce or inaccessible natural products is essential for the development of more sophisticated pharmaceutical agents and biological tools, and thus the development of atom-economical, step-economical and scalable processes to access these natural products is in high demand. Herein we report the development of a short, scalable total synthesis of (-)-α-kainic acid, a useful compound in neuropharmacology that is, however, limited in supply from natural resources. The synthesis features sequential platinum-catalyzed direct allylic aminations and thermal ene-cyclization, enabling the gram-scale synthesis of (-)-α-kainic acid in six steps and 34% overall yield. PMID:25604395

  7. Copper-Catalyzed Intramolecular Benzylic C-H Amination for the Synthesis of Isoindolinones.

    PubMed

    Yamamoto, Chiaki; Takamatsu, Kazutaka; Hirano, Koji; Miura, Masahiro

    2016-09-01

    A copper-catalyzed intramolecular amination occurs at the benzylic C-H of 2-methylbenzamides to deliver the corresponding isoindolinones of great interest in medicinal chemistry. The mild and abundant MnO2 works well as a terminal oxidant, and the reaction proceeds smoothly under potentially explosive organic peroxide-free conditions. Additionally, the directing-group-dependent divergent mechanisms are proposed: 8-aminoquinoline-containing benzamides include a Cu-mediated organometallic pathway whereas an aminyl radical-promoted Hofmann-Loffler-Freytag (HLF)-type mechanism can be operative in the case of N-naphthyl-substituted substrates. PMID:27504671

  8. AN EFFICIENT AND CHEMOSELECTIVE CBZ-PROTECTION OF AMINES USING SILICA-SULFURIC ACID AT ROOM TEMPERATURE

    EPA Science Inventory

    A simple, facile, and chemoselective N-benzyloxycarbonylation of amines using silica-sulfuric acid that proceeds under solvent-free conditions at room temperature has been achieved. These reactions are applicable to a wide variety of primary (aliphatic, cyclic) secondary amines, ...

  9. Liquid chromatography of hydrocarbonaeous quaternary amines on cyclodextrin bonded silica

    USGS Publications Warehouse

    Abidi, S.L.

    1986-01-01

    Mixtures of n-alkylbenzyldimethylammonium chloride (ABDAC) were resolved into homologous components by high-performance liquid chromatography (HPLC) with a cyclodextrin-bonded silica stationary phase. With a few exceptions, results from this study are similar to those obtained from traditional reversed-phase HPLC. It was found that the presence of electrolytes in aqueous mobile phases is not a critical factor in determining the success of HPLC separation. Under normal HPLC conditions, a mobile phase consisting of either methanol–water (50:50) or acetonitrile–water (30:70) was employed for obtaining adequate resolution of the quaternary ammonium mixtures. Although the percent organic modifier–water profiles were similar to those in previous studies with these compounds, resolution (R) and selectivity (α) parameters were found to be quite susceptible to changes in the mobile phase solvent composition. The retention behavior of the cationic analytes in the homologous series is consistent with the hydrophobic-interaction concept proposed for the retention mechanism via dominant inclusion complex formation. Several electrolytes were chosen for a study of the counter ion effect on the chromatographic characteristics of ABDAC components. Among the electrolytes examined, the perchlorate ion was found most likely to act as an ion-pairing counter ion for ammonium cations in the HPLC system studied. A correlation study established linear relationships between the chain length of ABDAC and the logarithmic capacity factor (k2). The analytical utility of the HPLC method was demonstrated by the analysis of various unknown mixtures.

  10. Rh(III)-Catalyzed C-H Bond Addition/Amine-Mediated Cyclization of Bis-Michael Acceptors.

    PubMed

    Potter, Tyler J; Ellman, Jonathan A

    2016-08-01

    A Rh(III)-catalyzed C-H bond addition/primary amine-promoted cyclization of bis-Michael acceptors is reported. The C-H bond addition step occurs with high chemoselectivity, and the subsequent intramolecular Michael addition, mediated by a primary amine catalyst, sets three contiguous stereocenters with high diastereoselectivity. A broad range of directing groups and both aromatic and alkenyl C-H bonds were shown to be effective in this transformation, affording functionalized piperidines, tetrahydropyrans, and cyclohexanes.

  11. A Practical and General Base-Catalyzed Carbonylation of Amines for the Synthesis of N-Formamides.

    PubMed

    Li, Wanfang; Wu, Xiao-Feng

    2015-10-12

    A highly practical and general base-catalyzed carbonylation of amines to the corresponding N-formamides has been realized. Cheap inorganic bases, including Group IA and IIA metal hydroxides, alkoxides, carbonates, and phosphates, were effective catalysts for the transformation. In the presence of 10-40 mol % of KOH or K2 CO3 , various amines were converted into the corresponding N-formamides in good-to-excellent yields using CO as the formylation reagents.

  12. Development of efficient amine-modified mesoporous silica SBA-15 for CO{sub 2} capture

    SciTech Connect

    Zhang, Xiaoyun; Qin, Hongyan; Zheng, Xiuxin; Wu, Wei

    2013-10-15

    Graphical abstract: - Highlights: • A secondary amine AN-TEPA is used to modify the SBA-15. • CO{sub 2} adsorption capacity (180.1 mg g{sup −1}-adsorbent for 70% amine loading) is high. • The sorbent exhibits a high stability after 12 cycling runs. • The modified SBA-15 achieves complete desorption at low temperature (100 °C). - Abstract: A novel CO{sub 2} sorbent was prepared by impregnating mesoporous silica, SBA-15, with acrylonitrile (AN)-modified tetraethylenepentamine (TEPA) in order to increase CO{sub 2} adsorption capacity and improve cycling stability. The mesoporous silica with pre- and post-surface modification was investigated by X-ray diffraction characterization (XRD), N{sub 2} adsorption–desorption test (N{sub 2}-BET), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The adsorption/desorption performance of S-TN (TN: AN modified TEPA) and S-TEPA was studied by dynamic adsorption. Test results showed that the solid base-impregnated SBA-15 demonstrated high CO{sub 2} adsorption capacity (180.1 mg g{sup −1}-adsorbent for 70% amine loading level). Compared to S-TEPA (24.1% decrease of initial capacity), S-TN with 50% amine loading exhibited improved cycling stability, 99.9% activity reserved (from initial 153.0 mg g{sup −1} to 151.3 mg g{sup −1}) after 12 cycles of adsorption/desorption at 100 °C. A mechanism of molecular structure of the loaded amine was attributed to the improved performance.

  13. Facile synthesis of unsymmetrical acridines and phenazines by a Rh(III)-catalyzed amination/cyclization/aromatization cascade.

    PubMed

    Lian, Yajing; Hummel, Joshua R; Bergman, Robert G; Ellman, Jonathan A

    2013-08-28

    We report formal [3 + 3] annulations of aromatic azides with aromatic imines and azobenzenes to give acridines and phenazines, respectively. These transformations proceed through a cascade process of Rh(III)-catalyzed amination followed by intramolecular electrophilic aromatic substitution and aromatization. Acridines can be directly prepared from aromatic aldehydes by in situ imine formation using catalytic benzylamine. PMID:23957711

  14. Facile Synthesis of Unsymmetrical Acridines and Phenazines by a Rhodium(III)-Catalyzed Amination, Cyclization and Aromatization Cascade

    PubMed Central

    Lian, Yajing; Hummel, Joshua R.; Bergman, Robert G.; Ellman, Jonathan A.

    2013-01-01

    New formal [3 + 3] annulations have been developed to obtain acridines and phenazines from aromatic azides and aromatic imines and azobenzenes, respectively. These transformations proceed through a cascade process of Rh(III)-catalyzed amination followed by intramolecular electrophilic aromatic substitution and aromatization. Acridines can be directly prepared from aromatic aldehydes by in situ imine formation using catalytic benzylamine. PMID:23957711

  15. Selective Formation of ortho-Aminobenzylamines by the Copper-Catalyzed Amination of Benzylamine Boronate Esters.

    PubMed

    McGarry, Kathryn A; Duenas, Alexi A; Clark, Timothy B

    2015-07-17

    The copper-catalyzed coupling between benzylamino boronate esters and aryl amines has been investigated. Formation of ortho-aminobenzylamines was achieved under oxidative conditions in the presence of copper(II) acetate. The major side product of the transformation is the homocoupling of the aryl boronate ester. The formation of the desired diamines was found to be improved in the absence of base, increasing selectivity over the homocoupled product. Both electron-donating and electron-withdrawing substituents are tolerated on both the boronate ester substrate and the aniline coupling partner under the reaction conditions. The presence of the adjacent benzylamine moiety appears to enhance the reactivity of the boronate ester and influence the resulting product distribution, likely by affecting the competing rates of transmetalation in the catalytic cycles. PMID:26067569

  16. Sensing Properties of GO and Amine-Silica Nanoparticles Functionalized QCM Sensors for Detection of Formaldehyde

    NASA Astrophysics Data System (ADS)

    Wang, Zhenqiang; Yang, Mingqing; He, Junhui

    2014-12-01

    In the current work, graphene oxides (GO) and Amine-Functionalized Silica Nanoparticles (NH2-SNs) were used as sensing layer on quart crystal microbalance (QCM) for detection of HCHO gas. The GO and NH2-SNs functionalized QCM resonators all had a significant response to HCHO gas. The sensitivity of GO functionalized QCM resonator is 0.04 Hz/(μgṡppm), which is four times as high as that of NH2-SNs functionalized QCM resonator (0.01 Hz/(μgṡppm)). The GO functionalized QCM resonators would be of benefit in area of environmental applications.

  17. Post-grafting amination of alkyl halide-functionalized silica for applications in catalysis, adsorption, and 15N NMR spectroscopy.

    PubMed

    Moschetta, Eric G; Sakwa-Novak, Miles A; Greenfield, Jake L; Jones, Christopher W

    2015-02-24

    An anhydrous synthesis of aminosilica materials from alkyl halide-functionalized mesoporous SBA-15 silica by post-grafting amination is introduced for applications in CO2 adsorption, cooperative catalysis, and (15)N solid-state NMR spectroscopy. The synthesis is demonstrated to convert terminal alkyl halide-functionalized silica materials containing Cl, Br, and I to primary alkylamines using anhydrous ammonia in a high-pressure reactor. The benefits of the post-grafting amination procedure include (i) use of anhydrous isotopically labeled ammonia, (15)NH3, to create aminosilica materials that can be investigated using (15)N solid-state NMR to elucidate potential intermediates and surface species in CO2 adsorption processes and catalysis, (ii) similar CO2 uptake in experiments extracting CO2 from dry simulated air experiments, and (iii) improved activity in acid-base bifunctional catalysis compared to traditional amine-grafted materials. The effects of the type of halide, the initial halide loading, and the total reaction time on the conversion of the halides to primary amines are explored. Physical and chemical characterizations of the materials show that the textural properties of the silica are unaffected by the reaction conditions and that quantitative conversion to primary amines is achieved even at short reaction times and high initial alkyl halide loadings. Additionally, preliminary (15)N solid-state NMR experiments indicate formation of nitrogen-containing species and demonstrate that the synthesis can be used to create materials useful for investigating surface species by NMR spectroscopy. The differences between the materials prepared via post-grafting amination vs traditional aminosilane grafting are attributed to the slightly increased spacing of the amines synthesized by amination because the alkylhalosilanes are initially better spaced on the silica surface after grafting, whereas the aminosilanes likely cluster to a greater extent when grafted on the

  18. Luminescent silica nanoparticles for sensing acetylcholinesterase-catalyzed hydrolysis of acetylcholine.

    PubMed

    Mukhametshina, Alsu R; Fedorenko, Svetlana V; Zueva, Irina V; Petrov, Konstantin A; Masson, Patrick; Nizameev, Irek R; Mustafina, Asiya R; Sinyashin, Oleg G

    2016-03-15

    This work highlights the H-function of Tb(III)-doped silica nanoparticles in aqueous solutions of acetic acid as a route to sense acetylcholinesterase-catalyzed hydrolysis of acetylcholine (ACh). The H-function results from H(+)-induced quenching of Tb(III)-centered luminescence due to protonation of Tb(III) complexes located close to silica/water interface. The H-function can be turned on/switched off by the concentration of complexes within core or nanoparticle shell zones, by the silica surface decoration and adsorption of both organic and inorganic cations on silica surface. Results indicate the optimal synthetic procedure for making nanoparticles capable of sensing acetic acid produced by enzymatic hydrolysis of acetylcholine. The H-function of nanoparticles was determined at various concentrations of ACh and AChE. The measurements show experimental conditions for fitting the H-function to Michaelis-Menten kinetics. Results confirm that reliable fluorescent monitoring AChE-catalyzed hydrolysis of ACh is possible through the H-function properties of Tb(III)-doped silica nanoparticles.

  19. Luminescent silica nanoparticles for sensing acetylcholinesterase-catalyzed hydrolysis of acetylcholine.

    PubMed

    Mukhametshina, Alsu R; Fedorenko, Svetlana V; Zueva, Irina V; Petrov, Konstantin A; Masson, Patrick; Nizameev, Irek R; Mustafina, Asiya R; Sinyashin, Oleg G

    2016-03-15

    This work highlights the H-function of Tb(III)-doped silica nanoparticles in aqueous solutions of acetic acid as a route to sense acetylcholinesterase-catalyzed hydrolysis of acetylcholine (ACh). The H-function results from H(+)-induced quenching of Tb(III)-centered luminescence due to protonation of Tb(III) complexes located close to silica/water interface. The H-function can be turned on/switched off by the concentration of complexes within core or nanoparticle shell zones, by the silica surface decoration and adsorption of both organic and inorganic cations on silica surface. Results indicate the optimal synthetic procedure for making nanoparticles capable of sensing acetic acid produced by enzymatic hydrolysis of acetylcholine. The H-function of nanoparticles was determined at various concentrations of ACh and AChE. The measurements show experimental conditions for fitting the H-function to Michaelis-Menten kinetics. Results confirm that reliable fluorescent monitoring AChE-catalyzed hydrolysis of ACh is possible through the H-function properties of Tb(III)-doped silica nanoparticles. PMID:26516688

  20. An Umpolung Strategy for the Synthesis of β-Aminoketones via Copper-Catalyzed Electrophilic Amination of Cyclopropanols.

    PubMed

    Ye, Zhishi; Dai, Mingji

    2015-05-01

    A novel copper-catalyzed electrophilic amination of cyclopropanols with O-benzoyl-N,N-dialkylhydroxylamines to synthesize various β-aminoketones via a sequence that includes C-C bond cleavage and Csp(3)-N bond formation is reported. The reaction conditions are mild and tolerate a wide range of functional groups including benzoate, tosylate, expoxide, and α,β-unsaturated carbonyls, which are incompatible in the traditional amine nucleophilic conjugate addition and the Mannich reaction conditions. Preliminary mechanistic studies and a proposed catalytic cycle of this umpolung β-aminoketone synthesis process have been described as well. PMID:25885943

  1. Palladium-Catalyzed Oxidative N-Dealkylation/Carbonylation of Tertiary Amines with Alkynes to α,β-Alkynylamides.

    PubMed

    Mane, Rajendra S; Bhanage, Bhalchandra M

    2016-06-17

    The first highly effective Pd/C-catalyzed oxidative N-dealkylation/carbonylation of various aliphatic as well as cyclic tertiary amines with alkynes has been described. The selective sp(3) C-N bond activation of tertiary amines at the less steric side using O2 as a sole oxidant and a plausible reaction pathway for the reaction are discussed. The general and operationally simple methodology provides an alternative for the synthesis of a wide range of alk-2-ynamide derivatives under mild conditions. The present protocol is ecofriendly and practical, and it shows significant recyclability. PMID:27182623

  2. An Umpolung Strategy for the Synthesis of β-Aminoketones via Copper-Catalyzed Electrophilic Amination of Cyclopropanols.

    PubMed

    Ye, Zhishi; Dai, Mingji

    2015-05-01

    A novel copper-catalyzed electrophilic amination of cyclopropanols with O-benzoyl-N,N-dialkylhydroxylamines to synthesize various β-aminoketones via a sequence that includes C-C bond cleavage and Csp(3)-N bond formation is reported. The reaction conditions are mild and tolerate a wide range of functional groups including benzoate, tosylate, expoxide, and α,β-unsaturated carbonyls, which are incompatible in the traditional amine nucleophilic conjugate addition and the Mannich reaction conditions. Preliminary mechanistic studies and a proposed catalytic cycle of this umpolung β-aminoketone synthesis process have been described as well.

  3. Chemical, Physical, and Mechanical Characterization of Isocyanate Cross-linked Amine-Modified Silica Aerogels

    NASA Technical Reports Server (NTRS)

    Katti, Atul; Shimpi, Nilesh; Roy, Samit; Lu, Hongbing; Fabrizio, Eve F.; Dass, Amala; Capadona, Lynn A.; Leventis, Nicholas

    2006-01-01

    We describe a new mechanically strong lightweight porous composite material obtained by encapsulating the skeletal framework of amine-modified silica aerogels with polyurea. The conformal polymer coating preserves the mesoporous structure of the underlying silica framework and the thermal conductivity remains low at 0.041 plus or minus 0.001 W m(sup -1 K(sup -1). The potential of the new cross-linked silica aerogels for load-carrying applications was determined through characterization of their mechanical behavior under compression, three-point bending, and dynamic mechanical analysis (DMA). A primary glass transition temperature of 130 C was identified through DMA. At room temperature, results indicate a hyperfoam behavior where in compression cross-linked aerogels are linearly elastic under small strains (less than 4%) and then exhibit yield behavior (until 40% strain), followed by densification and inelastic hardening. At room temperature the compressive Young's modulus and the Poisson's ratio were determined to be 129 plus or minus 8 MPa and 0.18, respectively, while the strain at ultimate failure is 77% and the average specific compressive stress at ultimate failure is 3.89 x 10(exp 5) N m kg(sup -1). The specific flexural strength is 2.16 x 10(exp 4) N m kg(sup -1). Effects on the compressive behavior of strain rate and low temperature were also evaluated.

  4. Sodium hydroxide catalyzed monodispersed high surface area silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Bhakta, Snehasis; Dixit, Chandra K.; Bist, Itti; Abdel Jalil, Karim; Suib, Steven L.; Rusling, James F.

    2016-07-01

    Understanding of the synthesis kinetics and our ability to modulate medium conditions allowed us to generate nanoparticles via an ultra-fast process. The synthesis medium is kept quite simple with tetraethyl orthosilicate (TEOS) as precursor and 50% ethanol and sodium hydroxide catalyst. Synthesis is performed under gentle conditions at 20 °C for 20 min Long synthesis time and catalyst-associated drawbacks are most crucial in silica nanoparticle synthesis. We have addressed both these bottlenecks by replacing the conventional Stober catalyst, ammonium hydroxide, with sodium hydroxide. We have reduced the overall synthesis time from 20 to 1/3 h, ∼60-fold decrease, and obtained highly monodispersed nanoparticles with 5-fold higher surface area than Stober particles. We have demonstrated that the developed NPs with ∼3-fold higher silane can be used as efficient probes for biosensor applications.

  5. One-step synthesis of amine-functionalized hollow mesoporous silica nanoparticles as efficient antibacterial and anticancer materials

    PubMed Central

    Hao, Nanjing; Jayawardana, Kalana W.; Chen, Xuan; De Zoysa, Thareendra

    2015-01-01

    In this study, amine-functionalized hollow mesoporous silica nanoparticles with an average diameter of ~100 nm and shell thickness of ~20 nm were prepared by an one-step process. This new nanoparticulate system exhibited excellent killing efficiency against mycobacterial (M. smegmatis strain mc2 651) and cancer cells (A549). PMID:25562524

  6. Scandium pentafluorobenzoate-catalyzed unexpected cascade reaction of 2-aminobenzaldehydes with primary amines: a process for the preparation of ring-fused aminals.

    PubMed

    Mao, Dan; Tang, Jun; Wang, Wenbo; Wu, Shengying; Liu, Xin; Yu, Jianjun; Wang, Limin

    2013-12-20

    An unexpected cascade reaction of 2-aminobenzaldehydes with arylamines catalyzed by scandium pentafluorobenzoate [Sc(Pfb)3] was reported as a facile strategy for the efficient synthesis of a novel class of polycyclic ring-fused aminals N-substituted-6,7,11b,13-tetrahydro-6,12-[1,2]benzenoquinazolino[3,4-a]quinazolin-13-amines 1. Under similar conditions, a series of the analogues of Tröger's base, 13-substituted-5,6,11,12-tetrahydro-6,12-epiminodibenzo[b,f][1,5]diazocines 2 were obtained when the arylamines were replaced by methanamines. A possible mechanism for the formation of 1 and 2 was proposed.

  7. Synthesis of Biaryl Ethers by the Copper-Catalyzed Chan-Evans-Lam Etherification from Benzylic Amine Boronate Esters.

    PubMed

    Marcum, Justin S; McGarry, Kathryn A; Ferber, Carl J; Clark, Timothy B

    2016-09-01

    The copper-catalyzed etherification of ortho-borylated benzylic amines with phenols has been achieved to provide biaryl ethers that are prevalent in biologically active compounds. A variety of substitution patterns on the aryl boronate ester and the phenol are tolerated under the reaction conditions, providing moderate to high yields. A competition reaction between phenol and aniline revealed condition-dependent selectivity in which the phenol could be highly favored over the aniline. PMID:27490146

  8. Copper‐Catalyzed Borylative Cross‐Coupling of Allenes and Imines: Selective Three‐Component Assembly of Branched Homoallyl Amines

    PubMed Central

    Rae, James; Yeung, Kay; McDouall, Joseph J. W.

    2015-01-01

    Abstract A copper‐catalyzed three‐component coupling of allenes, bis(pinacolato)diboron, and imines allows regio‐, chemo‐, and diastereoselective assembly of branched α,β‐substituted‐γ‐boryl homoallylic amines, that is, products bearing versatile amino, alkenyl, and borane functionality. Alternatively, convenient oxidative workup allows access to α‐substituted‐β‐amino ketones. A computational study has been used to probe the stereochemical course of the cross‐coupling. PMID:26632675

  9. Highly regio- and enantioselective synthesis of N-substituted 2-pyridones: iridium-catalyzed intermolecular asymmetric allylic amination.

    PubMed

    Zhang, Xiao; Yang, Ze-Peng; Huang, Lin; You, Shu-Li

    2015-02-01

    The first iridium-catalyzed intermolecular asymmetric allylic amination reaction with 2-hydroxypyridines has been developed, thus providing a highly efficient synthesis of enantioenriched N-substituted 2-pyridone derivatives from readily available starting materials. This protocol features a good tolerance of functional groups in both the allylic carbonates and 2-hydroxypyridines, thereby delivering multifunctionalized heterocyclic products with up to 98% yield and 99% ee. PMID:25504907

  10. Synthesis of chiral biphenol-based diphosphonite ligands and their application in palladium-catalyzed intermolecular asymmetric allylic amination reactions.

    PubMed

    Shi, Ce; Chien, Chih-Wei; Ojima, Iwao

    2011-02-01

    A library of new 2,2'-bis(diphenylphosphinoyloxy)-1,1'-binaphthyl (binapo)-type chiral diphosphonite ligands was designed and synthesized based on chiral 3,3',5,5',6,6'-hexasubstituted biphenols. These bop ligands have exhibited excellent efficiency in a palladium-catalyzed intermolecular allylic amination reaction, which provides a key intermediate for the total synthesis of Strychnos indole alkaloids with enantiopurities of up to 96% ee. PMID:21254441

  11. Effective and novel enantioselective preparation of pyranopyrazoles and pyranocoumarins that is catalyzed by a quinine-derived primary amine.

    PubMed

    Yang, Sai; Shen, Liu-lan; Kim, Yoon-Jung; Jeong, Jin-Hyun

    2016-01-14

    In this study, we executed an effective and novel enantioselective Michael/cyclodehydration sequential reaction between pyrazolin-5-one (or 4-hydroxy-2-pyrone) and chalcones that is catalyzed by a quinine-derived primary amine L7 in the presence of Boc-D-Phg-OH. Chiral pyranopyrazoles and pyranocoumarins were obtained in excellent enantioselectivities (up to 93%) with moderate yields and moderate enantioselectivities with high yields (up to 84%).

  12. Gold-Catalyzed Intermolecular Ynamide Amination-Initiated Aza-Nazarov Cyclization: Access to Functionalized 2-Aminopyrroles.

    PubMed

    Shu, Chao; Wang, Yong-Heng; Shen, Cang-Hai; Ruan, Peng-Peng; Lu, Xin; Ye, Long-Wu

    2016-07-01

    A novel gold-catalyzed intermolecular ynamide amination-initiated aza-Nazarov cyclization has been developed, allowing the facile and efficient synthesis of various 2-aminopyrroles in moderate to good yields. Furthermore, a mechanistic rationale for this tandem sequence, especially for the observed high regioselectivity, is also well supported by DFT (density functional theory) computations. The high flexibility, broad substrate scope, and mild nature of this reaction render it a viable alternative for the construction of 2-aminopyrroles. PMID:27331406

  13. Iridium-Catalyzed Allylic Amination Route to α-Aminoboronates: Illustration of the Decisive Role of Boron Substituents

    PubMed Central

    Touchet, Sabrina; Molander, Gary A.; Carboni, Bertrand; Bouillon, Alexandre

    2012-01-01

    The development of a new route to α-aminoboronates using an iridium-catalyzed allylic amination on boronated substrates is described. Unlike the boronate group, the trifluoroborato substituent was found to govern the regioselectivity exclusively in favor of branched products. The transformation of an allylic substitution product into an α-aminoboronic ester in an efficient way validated the implementation of this approach. PMID:22350584

  14. Divergent Coupling of Alcohols and Amines Catalyzed by Isoelectronic Hydride Mn(I) and Fe(II) PNP Pincer Complexes.

    PubMed

    Mastalir, Matthias; Glatz, Mathias; Gorgas, Nikolaus; Stöger, Berthold; Pittenauer, Ernst; Allmaier, Günter; Veiros, Luis F; Kirchner, Karl

    2016-08-22

    Herein, we describe an efficient coupling of alcohols and amines catalyzed by well-defined isoelectronic hydride Mn(I) and Fe(II) complexes, which are stabilized by a PNP ligand based on the 2,6-diaminopyridine scaffold. This reaction is an environmentally benign process implementing inexpensive, earth-abundant non-precious metal catalysts, and is based on the acceptorless alcohol dehydrogenation concept. A range of alcohols and amines including both aromatic and aliphatic substrates were efficiently converted in good to excellent isolated yields. Although in the case of Mn selectively imines were obtained, with Fe-exclusively monoalkylated amines were formed. These reactions proceed under base-free conditions and required the addition of molecular sieves. PMID:27377955

  15. Interfacial Modification of Silica Surfaces Through gamma-Isocyanatopropyl Triethoxy Silane-Amine Coupling Reactions

    SciTech Connect

    Vogel,B.; DeLongchamp, D.; Mahoney, C.; Lucas, L.; Fischer, D.; Lin, E.

    2008-01-01

    The development of robust, cost-effective methods to modify surfaces and interfaces without the specialized synthesis of unique coupling agents could provide readily accessible routes to optimize and tailor interfacial properties. We demonstrate that -isocyanatopropyl triethoxysilane (ISO) provides a convenient route to functionalize silica surfaces through coupling reactions with readily available reagents. ISO coupling agents layers (CALs) can be prepared from toluene with triethylamine (TEA), but the coupling reaction of an amine to the ISO CAL does not proceed. We use near edge X-ray absorption fine structure (NEXAFS), time-of-flight secondary ion mass spectrometry (TOF-SIMS) and sessile drop contact angle to demonstrate the isocyanate layer is not degraded under coupling conditions. Access to silanes with chemical functionality is possible with ISO by performing the coupling reaction in solution and then depositing the product onto the surface. Two model CAL surfaces are prepared to demonstrate the ease and robust nature of this procedure. The surfaces prepared using this method are the ISO reacted with octadecylamine to produce a hydrocarbon surface of similar quality to octadecyl trichlorosilane (OTS) CALs and with 9-aminofluorene (AFL), an aromatic amine functionality whose silane is otherwise unavailable commercially.

  16. Crosslinking Amine-Modified Silica Aerogels with Epoxies: Mechanically Strong Lightweight Porous Materials

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B.; Fabrizio, Eve F.; Ilhan, Faysal; Dass, Amala; Zhang, Guo-Hui; Vassilaras, Plousia; Johnston, J. Chris; Leventis, Nicholas

    2005-01-01

    The mesoporous surfaces of TMOS-derived silica aerogels have been modified with amines by co-polymerization of TMOS with APTES. The amine sites have become anchors for crosslinking the nanoparticles of the skeletal backbone of the aerogel by attachment of di-, tri and tetra-functional epoxies. The resulting conformal coatings increase the density of the native aerogels by a factor of 2-3 but the strength of the resulting materials may increase by more than two orders of magnitude. Processing variables such as amount of APTES used to make the gels, the epoxy type and concentration used for crosslinking, as well as the crosslinking temperature and time were varied according to a multivariable design-of-experiments (DOE) model. It was found that while elastic modulus follows a similar trend with density, maximum strength is attained neither at the maximum density nor at the highest concentration of -NH2 groups, suggesting surface saturation effects. Aerogels crosslinked with the tri-functional epoxide always show improved strength compared with aerogels crosslinked with the other two epoxides under identical conditions. Solid C-13 NMR studies show residual unreacted epoxides, which condense with ne another by heating crosslinked aerogels at 150 C.

  17. Cu(I)-catalyzed transannulation of N-heteroaryl aldehydes or ketones with alkylamines via C(sp3)-H amination.

    PubMed

    Li, Mingyang; Xie, Ying; Ye, Yong; Zou, Yong; Jiang, Huanfeng; Zeng, Wei

    2014-12-01

    A copper(I)-catalyzed direct transannulation of N-heteroaryl aldehydes or ketones with alkylamines via Csp(3)-H amination has been achieved using molecular oxygen as a sole oxidant. N-Heteroarenes are employed as the amine source. This transformation provides a rapid and concise access to multifunctional imidazo[1,5-a]pyridines.

  18. (E)-α,β-unsaturated amides from tertiary amines, olefins and CO via Pd/Cu-catalyzed aerobic oxidative N-dealkylation.

    PubMed

    Shi, Renyi; Zhang, Hua; Lu, Lijun; Gan, Pei; Sha, Yuchen; Zhang, Heng; Liu, Qiang; Beller, Matthias; Lei, Aiwen

    2015-02-21

    A novel Pd/Cu-catalyzed chemoselective aerobic oxidative N-dealkylation/carbonylation reaction has been developed. Tertiary amines are utilized as a "reservoir" of "active" secondary amines in this transformation, which inhibits the formation of undesired by-products and the deactivation of the catalysts. This protocol allows for an efficient and straightforward construction of synthetically useful and bioactive (E)-α,β-unsaturated amide derivatives from easily available tertiary amines, olefins and CO. PMID:25610923

  19. Functionalized Polysilsesquioxane-Based Hybrid Silica Solid Amine Sorbents for the Regenerative Removal of CO2 from Air.

    PubMed

    Abhilash, Kochukunju Adisser Saraladevi; Deepthi, Thomas; Sadhana, Retnakumari Amma; Benny, K George

    2015-08-19

    Functionalized polysilsesquioxane-based hybrid silica materials are presented as solid amine sorbents for direct CO2 capture from air. The sorbent was synthesized from amine and vinyl functionalized alkoxysilanes by a simple, energy efficient, and cost-effective co-condensation method. The material, containing bound amine functionalities, was found to have a selective CO2 capturing capacity of 1.68 mmol/g from atmospheric air with an adsorption half time of 50 min. This material also showed a maximum adsorption capacity of 2.28 mmol/g in pure CO2 and 1.92 mmol/g in 10% CO2. Desorption started at a temperature as low as 60 °C, and complete desorption occurred at 80 °C. The sorbent exhibited high recycling ability, and 100 cycles of adsorption/desorption were demonstrated in pure CO2 and 50 cycles in ambient air without any loss in efficiency.

  20. Copper-catalyzed N- and O-alkylation of amines and phenols using alkylborane reagents.

    PubMed

    Sueki, Shunsuke; Kuninobu, Yoichiro

    2013-04-01

    By the reaction of amines with alkylborane reagents in the presence of a catalytic amount of copper(II) acetate Cu(OAc)2 and di-tert-butyl peroxide, a cross-coupling reaction proceeded and alkylated amines were obtained in good to excellent yields. Phenols are also applicable for this reaction, and the corresponding alkyl aryl ethers were produced. PMID:23521042

  1. Unlocking ylide reactivity in the metal-catalyzed allylic substitution reaction: stereospecific construction of primary allylic amines with aza-ylides.

    PubMed

    Evans, P Andrew; Clizbe, Elizabeth A

    2009-07-01

    The transition metal catalyzed allylic amination represents a powerful and versatile cross-coupling for the asymmetric construction of stereogenic C-N bonds that are present in secondary metabolites and medicinally important agents. We have developed a regio- and enantiospecific rhodium-catalyzed allylic amination reaction using the aza-ylide derived from 1-aminopyridinium iodide. This investigation demonstrates the importance of the ylide-stabilizing group for obtaining the desired nucleophilicity and the ability to utilize the aza-ylide as a commercially available ammonia equivalent, which serves to illustrate the synthetic potential of this nucleophile for the preparation of primary amines. Overall, this work provides an opportunity to investigate the utility of this new class of nucleophiles in related metal-catalyzed reactions.

  2. Transition metal-catalyzed process for addition of amines to carbon-carbon double bonds

    DOEpatents

    Hartwig, John F.; Kawatsura, Motoi; Loeber, Oliver

    2002-01-01

    The present invention is directed to a process for addition of amines to carbon-carbon double bonds in a substrate, comprising: reacting an amine with a compound containing at least one carbon-carbon double bond in the presence a transition metal catalyst under reaction conditions effective to form a product having a covalent bond between the amine and a carbon atom of the former carbon-carbon double bond. The transition metal catalyst comprises a Group 8 metal and a ligand containing one or more 2-electron donor atoms. The present invention is also directed to enantioselective reactions of amine compounds with compounds containing carbon-carbon double bonds, and a calorimetric assay to evaluate potential catalysts in these reactions.

  3. Practical Synthesis of Amides via Copper/ABNO-Catalyzed Aerobic Oxidative Coupling of Alcohols and Amines.

    PubMed

    Zultanski, Susan L; Zhao, Jingyi; Stahl, Shannon S

    2016-05-25

    A modular Cu/ABNO catalyst system has been identified that enables efficient aerobic oxidative coupling of alcohols and amines to amides. All four permutations of benzylic/aliphatic alcohols and primary/secondary amines are viable in this reaction, enabling broad access to secondary and tertiary amides. The reactions exhibit excellent functional group compatibility and are complete within 30 min-3 h at rt. All components of the catalyst system are commercially available. PMID:27171973

  4. Palladium-Catalyzed Ortho-Selective C-H Oxidative Carbonylation of N-Substituted Anilines with CO and Primary Amines for the Synthesis of o-Aminobenzamides.

    PubMed

    Zhang, Xiaopeng; Dong, Shuxiang; Niu, Xueli; Li, Zhengwei; Fan, Xuesen; Zhang, Guisheng

    2016-09-16

    An efficient, one-pot strategy with high selectivity and high atom economy for the synthesis of o-aminobenzamides has been developed via palladium-catalyzed ortho-selective C-H oxidative carbonylation of N-substituted anilines with CO and primary amines. A wide range of N-substituted anilines and primary amines can be tolerated in this transformation to afford the corresponding o-aminobenzamides in moderate to excellent yields under mild conditions. PMID:27583815

  5. Synthesis of quinazolines and tetrahydroquinazolines: copper-catalyzed tandem reactions of 2-bromobenzyl bromides with aldehydes and aqueous ammonia or amines.

    PubMed

    Fan, Xuesen; Li, Bin; Guo, Shenghai; Wang, Yuanyuan; Zhang, Xinying

    2014-03-01

    An efficient synthesis of diversely substituted quinazolines and 1,2,3,4-tetrahydroquinazolines through copper-catalyzed tandem reactions of the readily available 2-bromobenzyl bromides, aldehydes, and aqueous ammonia or amines has been developed. By using ammonia and simple aliphatic amines as the nitrogen source, the present method provides a versatile and practical protocol for the synthesis of quinazolines and 1,2,3,4-tetrahydroquinazolines. PMID:24376138

  6. Effect of polyvinylpyrrolidone on mesoporous silica morphology and esterification of lauric acid with 1-butanol catalyzed by immobilized enzyme

    SciTech Connect

    Zhang, Jinyu; Zhou, Guowei Jiang, Bin; Zhao, Minnan; Zhang, Yan

    2014-05-01

    Mesoporous silica materials with a range of morphology evolution, i.e., from curved rod-shaped mesoporous silica to straight rod-shaped mesoporous silica, were successfully prepared using polyvinylpyrrolidone (PVP) and triblock copolymer as dual template. The effects of PVP molecular weight and concentration on mesoporous silica structure parameters were studied. Results showed that surface area and pore volume continuously decreased with increased PVP molecular weight. Mesoporous silica prepared with PVP K30 also possessed larger pore diameter, interplanar spacing (d{sub 100}), and cell parameter (a{sub 0}) than that prepared with PVP K15 and PVP K90. In addition, with increased PVP concentration, d{sub 100} and a{sub 0} continuously decreased. The mechanism of morphology evolution caused by the change in PVP concentration was investigated. The conversion rate of lauric acid with 1-butanol catalyzed by immobilized Porcine pancreatic lipase (PPL) was also evaluated. Results showed that PPL immobilized on amino-functionalized straight rod-shaped mesoporous silica maintained 50% of its esterification conversion rate even after five cycles of use with a maximum conversion rate was about 90.15%. - Graphical abstract: Curved rod-shaped mesoporous silica can be obtained at low and the highest PVP concentration, while straight rod-shaped mesoporous silica can be obtained at higher PVP concentration. - Highlights: • Mesoporous silica with morphology evolution from CRMS to SRMS were prepared. • Effects of PVP molecular weight and concentration on silica morphology were studied. • A possible mechanism for the formation of morphology evolution SiO{sub 2} was proposed. • Esterification of lauric acid with 1-butanol catalyzed by immobilized PPL.

  7. Cu/Nitroxyl Catalyzed Aerobic Oxidation of Primary Amines into Nitriles at Room Temperature.

    PubMed

    Kim, Jinho; Stahl, Shannon S

    2013-07-01

    An efficient catalytic method has been developed for aerobic oxidation of primary amines to the corresponding nitriles. The reactions proceed at room temperature and employ a catalyst consisting of (4,4'- (t) Bu2bpy)CuI/ABNO (ABNO = 9-azabicyclo[3.3.1]nonan-3-one N-oxyl). The reactions exhibit excellent functional group compatibility and substrate scope, and are effective with benzylic, allylic and aliphatic amines. Preliminary mechanistic studies suggest that aerobic oxidation of the Cu catalyst is the turnover-limiting step of the reaction. PMID:24015373

  8. Direct asymmetric dearomatization of 2-naphthols by scandium-catalyzed electrophilic amination.

    PubMed

    Nan, Jiang; Liu, Jingjing; Zheng, Huayu; Zuo, Zhijun; Hou, Lei; Hu, Huaiming; Wang, Yaoyu; Luan, Xinjun

    2015-02-16

    Catalytic asymmetric aminative dearomatization of 1-substituted 2-naphthols was successfully implemented with electrophilic azodicarboxylates under the catalysis of chiral Sc(III)/pybox complexes. This intermolecular reaction represents a hitherto unknown enantioselective C-N bond-forming process through direct dearomatization of phenolic compounds to generate chiral nitrogen-containing quaternary carbon stereocenters.

  9. Copper-catalyzed aliphatic C-H amination with an amidine moiety.

    PubMed

    Chen, Hui; Sanjaya, Stephen; Wang, Yi-Feng; Chiba, Shunsuke

    2013-01-01

    A method for amination of aliphatic C-H bonds of N-alkylamidines is described that utilizes Cu(OAc)(2) as the catalyst in the presence of PhI(OAc)(2) and K(3)PO(4). The resulting products, dihydroimidazoles and tetrahydropyrimidines, could be converted into the corresponding diamines by hydride reduction. PMID:23252919

  10. Pyridine synthesis by reactions of allyl amines and alkynes proceeding through a Cu(OAc)2 oxidation and Rh(III)-catalyzed N-annulation sequence.

    PubMed

    Kim, Dong-Su; Park, Jung-Woo; Jun, Chul-Ho

    2012-11-28

    A new methodology has been developed for the synthesis of pyridines from allyl amines and alkynes, which involves sequential Cu(II)-promoted dehydrogenation of the allylamine and Rh(III)-catalyzed N-annulation of the resulting α,β-unsaturated imine and alkyne. PMID:23069867

  11. Pd/C-catalyzed synthesis of oxamates by oxidative cross double carbonylation of amines and alcohols under co-catalyst, base, dehydrating agent, and ligand-free conditions.

    PubMed

    Gadge, Sandip T; Bhanage, Bhalchandra M

    2013-07-01

    This work reports a mild, efficient, and ligand-free Pd/C-catalyzed protocol for the oxidative cross double carbonylation of amines and alcohols. Notably, the reaction does not requires any base, co-catalyst, dehydrating agent, or ligand. Pd/C solves the problem of catalyst recovery, and the catalyst was recycled up to six times. PMID:23734639

  12. Energy-efficient green catalysis: supported gold nanoparticle-catalyzed aminolysis of esters with inert tertiary amines by C-O and C-N bond activations.

    PubMed

    Bao, Yong-Sheng; Baiyin, Menghe; Agula, Bao; Jia, Meilin; Zhaorigetu, Bao

    2014-07-18

    Catalyzed by supported gold nanoparticles, an aminolysis reaction between various aryl esters and inert tertiary amines by C-O and C-N bond activations has been developed for the selective synthesis of tertiary amides. Comparison studies indicated that the gold nanoparticles could perform energy-efficient green catalysis at room temperature, whereas Pd(OAc)2 could not.

  13. Squaramide-tertiary amine catalyzed asymmetric cascade sulfa-Michael/Michael addition via dynamic kinetic resolution: access to highly functionalized chromans with three contiguous stereocenters.

    PubMed

    Yang, Wen; Yang, Yi; Du, Da-Ming

    2013-03-15

    An efficient asymmetric cascade sulfa-Michael/Michael addition reaction catalyzed by a chiral bifunctional squaramide-tertiary amine catalyst has been developed. This organocatalytic cascade reaction provides easy access to highly functionalized chromans with three contiguous stereocenters, including one quaternary center. In addition, a novel cascade sulfa Michael/retro-sulfa-Michael/sulfa-Michael/Michael reaction process, involving dynamic kinetic resolution, is described.

  14. Enantioselective Amine-Catalyzed [4 + 2] Annulations of Allene Ketones and 2,3-Dioxopyrrolidine Derivatives: Synthesis of 4H-Pyran Derivatives.

    PubMed

    Zhang, Shuang; Luo, Yong-Chun; Hu, Xiu-Qin; Wang, Zhu-Yin; Liang, Yong-Min; Xu, Peng-Fei

    2015-07-17

    An efficient cinchona alkaloid-derived amine catalyzed asymmetric [4 + 2] cycloaddition is successfully developed. 4H-Pyran fused pyrrolin-2-one products are readily obtained in moderate to high yields with good enantioselectivites by employing allene ketones and 2,3-dioxopyrrolidine derivatives as substrates.

  15. Copper-Catalyzed Oxidative C-H Amination of Tetrahydrofuran with Indole/Carbazole Derivatives.

    PubMed

    Yang, Qingjing; Choy, Pui Ying; Fu, Wai Chung; Fan, Baomin; Kwong, Fuk Yee

    2015-11-01

    A simple α-C-H amination of cyclic ether with indole/carbazole derivatives has been accomplished by employing copper(II) chloride/bipy as the catalyst system. In the presence of the di-tert-butyl peroxide oxidant, cyclic ethers such as tetrahydrofuran, 1,4-dioxane, and tetrahydropyran successfully undergo C-H/N-H cross dehydrogenative coupling (CDC) with various carbazole or indole derivatives in good-to-excellent yields. PMID:26485515

  16. An Inner-Sphere Mechanism for Molecular Oxygen Reduction Catalyzed by Copper Amine Oxidases

    PubMed Central

    Mukherjee, Arnab; Smirnov, Valeriy V.; Lanci, Michael P.; Brown, Doreen E.; Shepard, Eric M.; Dooley, David M.; Roth, Justine P.

    2008-01-01

    Copper and topaquinone (TPQ) containing amine oxidases utilize O2 for the metabolism of biogenic amines while concomitantly generating H2O2 for use by the cell. The mechanism of O2 reduction has been the subject of long-standing debate due to the obscuring influence of a proton-coupled electron transfer between the tyrosine-derived TPQ and copper, a rapidly established equilibrium precluding assignment of the enzyme in its reactive form. Here we show that substrate-reduced pea seedling amine oxidase (PSAO) exists predominantly in the CuI, TPQ semiquinone state. A new mechanistic proposal for O2 reduction is advanced on the basis of thermodynamic considerations together with kinetic studies (at varying pH, temperature and viscosity), the identification of steady-state intermediates and the analysis of competitive oxygen kinetic isotope effects: 18O KIEs, [kcat/KM(16,16O2)]/[kcat/KM(16,18O2)]. The 18O KIE = 1.0136 ± 0.0013 at pH 7.2 is independent of temperature from 5 to 47°C and insignificantly changed to 1.0122 ± 0.0020 upon raising the pH to 9, thus indicating the absence of kinetic complexity. Using density functional methods, the effect is found to be precisely in the range expected for reversible O2 binding to CuI to afford a superoxide, [CuII(η1-O2)−I]+, intermediate. Electron transfer from the TPQ semiquinone follows in the first irreversible step to form a peroxide, CuII(η1-O2)−II, intermediate driving the reduction of O2. The similar 18O KIEs reported for copper amine oxidases from other sources raise the possibility that all enzymes react by related inner-sphere mechanisms although additional experiments are needed to test this proposal. PMID:18582059

  17. Rhodium-catalyzed anti-Markovnikov addition of secondary amines to arylacetylenes at room temperature.

    PubMed

    Sakai, Kazunori; Kochi, Takuya; Kakiuchi, Fumitoshi

    2011-08-01

    An efficient method for synthesis of E-enamines by the anti-Markovnikov addition of secondary amines to terminal alkynes is described. The reaction of a variety of aryl- and heteroarylacetylenes proceeded at room temperature using a combination of a 8-quinolinolato rhodium complex and P(p-MeOC(6)H(4))(3) as a catalyst. The products were obtained as enamines by simple bulb-to-bulb distillation. PMID:21699251

  18. Heterogeneously porous γ-MnO₂-catalyzed direct oxidative amination of benzoxazole through C-H activation in the presence of O₂.

    PubMed

    Pal, Provas; Giri, Arnab Kanti; Singh, Harshvardhan; Ghosh, Subhash Chandra; Panda, Asit Baran

    2014-09-01

    Oxidative amination of azoles through catalytic C-H bond activation is a very important reaction due to the presence of 2-aminoazoles in several biologically active compounds. However, most of the reported methods are performed under homogeneous reaction conditions using excess reagents and additives. Herein, we report the heterogeneous, porous γ-MnO2-catalyzed direct amination of benzoxazole with wide range of primary and secondary amines. The amination was carried under mild reaction conditions and using molecular oxygen as a green oxidant, without any additives. The catalyst can easily be separated by filtration and reused several times without a significant loss of its catalytic performance. Of note, the reaction tolerates a functional group such as alcohol, thus indicating the broad applicability of this reaction.

  19. Amine-catalyzed direct aldol reactions of hydroxy- and dihydroxyacetone: biomimetic synthesis of carbohydrates.

    PubMed

    Popik, Oskar; Pasternak-Suder, Monika; Leśniak, Katarzyna; Jawiczuk, Magdalena; Górecki, Marcin; Frelek, Jadwiga; Mlynarski, Jacek

    2014-06-20

    This article presents comprehensive studies on the application of primary, secondary, and tertiary amines as efficient organocatalysts for the de novo synthesis of ketoses and deoxyketoses. Mimicking the actions of aldolase enzymes, the synthesis of selected carbohydrates was accomplished in aqueous media by using proline- and serine-based organocatalysts. The presented methodology also provides direct access to unnatural L-carbohydrates from the (S)-glyceraldehyde precursor. Determination of the absolute configuration of all obtained sugars was feasible using a methodology consisting of concerted ECD and VCD spectroscopy.

  20. Mechanistic Insights into the Palladium-Catalyzed Aziridination of Aliphatic Amines by C-H Activation.

    PubMed

    Smalley, Adam P; Gaunt, Matthew J

    2015-08-26

    Detailed kinetic studies and computational investigations have been performed to elucidate the mechanism of a palladium-catalyzed C-H activation aziridination. A theoretical rate law has been derived that matches with experimental observations and has led to an improvement in the reaction conditions. Acetic acid was found to be beneficial in controlling the formation of an off-cycle intermediate, allowing a decrease in catalyst loading and improved yields. Density functional theory (DFT) studies were performed to examine the selectivities observed in the reaction. Evidence for electronic-controlled regioselectivity for the cyclopalladation step was obtained by a distortion-interaction analysis, whereas the aziridination product was justified through dissociation of acetic acid from the palladium(IV) intermediate preceding the product-forming reductive elimination step. The understanding of this reaction mechanism under the synthesis conditions should provide valuable assistance in the comprehension and design of palladium-catalyzed reactions on similar systems. PMID:26247373

  1. Iridium Catalyzed Dehydrogenation of Substituted Amine Boranes: Kinetics, Thermodynamics and Implications for Hydrogen Storage.

    SciTech Connect

    Dietrich, Brandon L.; Goldberg, Karen I.; Heinekey, D. M.; Autrey, Thomas; Linehan, John C.

    2008-10-06

    Dehydrogenation of ammonia borane (AB) and methylamine-borane (MeAB) is catalyzed efficiently by the iridium pincer complex (η3-1,3-(OPtBu2)2C6H3)Ir(H)2 (1). With MeAB and with MeAB/AB mixtures, rapid release of one equivalent of H2 is observed to yield soluble oligomeric products at rates similar to those previously reported for the dehydrogenation of AB catalyzed by 1. The rapid dehydrogenation reaction has allowed the experimental determination of the reaction enthalpy (ΔH) for the dehydrogenation of AB, MeAB, and AB/MeAB mixtures by calorimetry. The reactions are significantly more exothermic than suggested by some computational studies. This work was supported by the U.S. Department of Energy (DOE) as part of the Center of Excellence for Chemical Hydrogen Storage. PNNL is operated by Battelle for DOE.

  2. Mechanistic Insights into the Palladium-Catalyzed Aziridination of Aliphatic Amines by C-H Activation.

    PubMed

    Smalley, Adam P; Gaunt, Matthew J

    2015-08-26

    Detailed kinetic studies and computational investigations have been performed to elucidate the mechanism of a palladium-catalyzed C-H activation aziridination. A theoretical rate law has been derived that matches with experimental observations and has led to an improvement in the reaction conditions. Acetic acid was found to be beneficial in controlling the formation of an off-cycle intermediate, allowing a decrease in catalyst loading and improved yields. Density functional theory (DFT) studies were performed to examine the selectivities observed in the reaction. Evidence for electronic-controlled regioselectivity for the cyclopalladation step was obtained by a distortion-interaction analysis, whereas the aziridination product was justified through dissociation of acetic acid from the palladium(IV) intermediate preceding the product-forming reductive elimination step. The understanding of this reaction mechanism under the synthesis conditions should provide valuable assistance in the comprehension and design of palladium-catalyzed reactions on similar systems.

  3. Ligand-Free Pd-Catalyzed Double Carbonylation of Aryl Iodides with Amines to α-Ketoamides under Atmospheric Pressure of Carbon Monoxide and at Room Temperature.

    PubMed

    Du, Hongyan; Ruan, Qing; Qi, Minghao; Han, Wei

    2015-08-01

    A general Pd-catalyzed double carbonylation of aryl iodides with secondary or primary amines to produce α-ketoamides at atmospheric CO pressure has been developed. This transformation proceeds successfully even at room temperature and in the absence of any ligand and additive. A wide range of aryl iodides and amines can be coupled to the desired α-ketoamides in high yields with excellent chemoselectivities. Importantly, the current methodology has been demonstrated to be applied in the synthesis of bioactive molecules and chiral α-ketoamides.

  4. Effect of polyvinylpyrrolidone on mesoporous silica morphology and esterification of lauric acid with 1-butanol catalyzed by immobilized enzyme

    NASA Astrophysics Data System (ADS)

    Zhang, Jinyu; Zhou, Guowei; Jiang, Bin; Zhao, Minnan; Zhang, Yan

    2014-05-01

    Mesoporous silica materials with a range of morphology evolution, i.e., from curved rod-shaped mesoporous silica to straight rod-shaped mesoporous silica, were successfully prepared using polyvinylpyrrolidone (PVP) and triblock copolymer as dual template. The effects of PVP molecular weight and concentration on mesoporous silica structure parameters were studied. Results showed that surface area and pore volume continuously decreased with increased PVP molecular weight. Mesoporous silica prepared with PVP K30 also possessed larger pore diameter, interplanar spacing (d100), and cell parameter (a0) than that prepared with PVP K15 and PVP K90. In addition, with increased PVP concentration, d100 and a0 continuously decreased. The mechanism of morphology evolution caused by the change in PVP concentration was investigated. The conversion rate of lauric acid with 1-butanol catalyzed by immobilized Porcine pancreatic lipase (PPL) was also evaluated. Results showed that PPL immobilized on amino-functionalized straight rod-shaped mesoporous silica maintained 50% of its esterification conversion rate even after five cycles of use with a maximum conversion rate was about 90.15%.

  5. Improved Synthesis of 5-Substituted 1H-Tetrazoles via the [3+2] Cycloaddition of Nitriles and Sodium Azide Catalyzed by Silica Sulfuric Acid

    PubMed Central

    Du, Zhenting; Si, Changmei; Li, Youqiang; Wang, Yin; Lu, Jing

    2012-01-01

    A silica supported sulfuric acid catalyzed [3+2] cycloaddition of nitriles and sodium azide to form 5-substituted 1H-tetrazoles is described. The protocol can provide a series of 5-substituted 1H-tetrazoles using silica sulfuric acid from nitriles and sodium azide in DMF in 72%–95% yield. PMID:22606004

  6. Gravimetric analysis of the adsorption and desorption of CO2 on amine-functionalized mesoporous silica mounted on a microcantilever array.

    PubMed

    Lee, Dongkyu; Jin, Yusung; Jung, Namchul; Lee, Jaehyuk; Lee, Jinwoo; Jeong, Yong Shik; Jeon, Sangmin

    2011-07-01

    The kinetics of CO(2) adsorption and desorption over amine-functionalized mesoporous silica were investigated using silicon microcantilever arrays. Three types of mesoporous silica with different pore sizes were synthesized and functionalized with a variety of amine molecules. After depositing the silica sorbents onto the free end of each cantilever in an array, mass changes due to the adsorption and desorption of CO(2) were determined in situ with picogram sensitivity by measuring variations in the cantilever frequencies. The adsorption and desorption kinetics were found to be diffusion-controlled, and the kinetics were accelerated by increasing the temperature and pore size. The activation energies for adsorption and desorption of CO(2) were determined from Arrhenius plots.

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

    PubMed Central

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

    2011-01-01

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

  8. Cyclic stability testing of aminated-silica solid sorbent for post-combustion CO2 capture.

    PubMed

    Fisher, James C; Gray, McMahan

    2015-02-01

    The National Energy Technology Laboratory (NETL) is examining the use of solid sorbents for CO2 removal from coal-fired power plant flue gas streams. An aminated sorbent (previously reported by the NETL) is tested for stability by cyclic exposure to simulated flue gas and subsequent regeneration for 100 cycles. Each cycle was quantified using a traced gas in the simulated flue gas monitored by a mass spectrometer, which allowed for rapid determination of the capacity.

  9. Cyclic stability testing of aminated-silica solid sorbent for post-combustion CO2 capture.

    PubMed

    Fisher, James C; Gray, McMahan

    2015-02-01

    The National Energy Technology Laboratory (NETL) is examining the use of solid sorbents for CO2 removal from coal-fired power plant flue gas streams. An aminated sorbent (previously reported by the NETL) is tested for stability by cyclic exposure to simulated flue gas and subsequent regeneration for 100 cycles. Each cycle was quantified using a traced gas in the simulated flue gas monitored by a mass spectrometer, which allowed for rapid determination of the capacity. PMID:25510438

  10. Bulk gold catalyzed oxidation reactions of amines and isocyanides and iron porphyrin catalyzed N-H and O-H bond insertion/cyclization reactions of diamines and aminoalcohols

    SciTech Connect

    Klobukowski, Erik

    2011-01-01

    This work involves two projects. The first project entails the study of bulk gold as a catalyst in oxidation reactions of isocyanides and amines. The main goal of this project was to study the activation and reactions of molecules at metal surfaces in order to assess how organometallic principles for homogeneous processes apply to heterogeneous catalysis. Since previous work had used oxygen as an oxidant in bulk gold catalyzed reactions, the generality of gold catalysis with other oxidants was examined. Amine N-oxides were chosen for study, due to their properties and use in the oxidation of carbonyl ligands in organometallic complexes. When amine N-oxides were used as an oxidant in the reaction of isocyanides with amines, the system was able to produce ureas from a variety of isocyanides, amines, and amine N-oxides. In addition, the rate was found to generally increase as the amine N-oxide concentration increased, and decrease with increased concentrations of the amine. Mechanistic studies revealed that the reaction likely involves transfer of an oxygen atom from the amine N-oxide to the adsorbed isocyanide to generate an isocyanate intermediate. Subsequent nucleophilic attack by the amine yields the urea. This is in contrast to the bulk gold-catalyzed reaction mechanism of isocyanides with amines and oxygen. Formation of urea in this case was proposed to proceed through a diaminocarbene intermediate. Moreover, formation of the proposed isocyanate intermediate is consistent with the reactions of metal carbonyl ligands, which are isoelectronic to isocyanides. Nucleophilic attack at coordinated CO by amine N-oxides produces CO{sub 2} and is analogous to the production of an isocyanate in this gold system. When the bulk gold-catalyzed oxidative dehydrogenation of amines was examined with amine N-oxides, the same products were afforded as when O{sub 2} was used as the oxidant. When the two types of oxidants were directly compared using the same reaction system and

  11. Mechanistic studies of hydrogen evolution in aqueous solution catalyzed by a tertpyridine-amine cobalt complex

    DOE PAGESBeta

    Lewandowska-Andralojc, Anna; Baine, Teera; Zhao, Xuan; Muckerman, James T.; Fujita, Etsuko; Poyansky, Dmitry E.

    2015-04-22

    The ability of cobalt-based transition metal complexes to catalyze electrochemical proton reduction to produce molecular hydrogen has resulted in a large number of mechanistic studies involving various cobalt complexes. In addition, while the basic mechanism of proton reduction promoted by cobalt species is well understood, the reactivity of certain reaction intermediates, such as CoI and CoIII–H, is still relatively unknown owing to their transient nature, especially in aqueous media. In this work we investigate the properties of intermediates produced during catalytic proton reduction in aqueous solutions promoted by the [(DPA-Bpy)Co(OH₂)]n+ (DPA-Bpy = N,N-bis(2-pyridinylmethyl)-2,20-bipyridine-6-methanamine) complex ([Co(L)(OH₂)]n+ where L is the pentadentatemore » DPA-Bpy ligand or [Co(OH₂)]n+ as a shorthand). Experimental results based on transient pulse radiolysis and laser flash photolysis methods, together with electrochemical studies and supported by DFT calculations indicate that, while the water ligand is strongly coordinated to the metal center in the oxidation state 3+, one-electron reduction of the complex to form a CoII species results in weakening the Co–O bond. The further reduction to a CoI species leads to the loss of the aqua ligand and the formation of [CoI–VS)]⁺ (VS = vacant site). Interestingly, DFT calculations also predict the existence of a [CoI(κ⁴-L)(OH₂)]⁺ species at least transiently, and its formation is consistent with the experimental Pourbaix diagram. Both electrochemical and kinetics results indicate that the CoI species must undergo some structural change prior to accepting the proton, and this transformation represents the rate-determining step (RDS) in the overall formation of [CoIII–H]⁺. We propose that this RDS may originate from the slow removal of a solvent ligand in the intermediate [CoI(κ⁴-L)(OH₂)]⁺ in addition to the significant structural reorganization of the metal complex and

  12. Mechanistic studies of hydrogen evolution in aqueous solution catalyzed by a tertpyridine-amine cobalt complex

    SciTech Connect

    Lewandowska-Andralojc, Anna; Baine, Teera; Zhao, Xuan; Muckerman, James T.; Fujita, Etsuko; Poyansky, Dmitry E.

    2015-04-22

    The ability of cobalt-based transition metal complexes to catalyze electrochemical proton reduction to produce molecular hydrogen has resulted in a large number of mechanistic studies involving various cobalt complexes. In addition, while the basic mechanism of proton reduction promoted by cobalt species is well understood, the reactivity of certain reaction intermediates, such as CoI and CoIII–H, is still relatively unknown owing to their transient nature, especially in aqueous media. In this work we investigate the properties of intermediates produced during catalytic proton reduction in aqueous solutions promoted by the [(DPA-Bpy)Co(OH₂)]n+ (DPA-Bpy = N,N-bis(2-pyridinylmethyl)-2,20-bipyridine-6-methanamine) complex ([Co(L)(OH₂)]n+ where L is the pentadentate DPA-Bpy ligand or [Co(OH₂)]n+ as a shorthand). Experimental results based on transient pulse radiolysis and laser flash photolysis methods, together with electrochemical studies and supported by DFT calculations indicate that, while the water ligand is strongly coordinated to the metal center in the oxidation state 3+, one-electron reduction of the complex to form a CoII species results in weakening the Co–O bond. The further reduction to a CoI species leads to the loss of the aqua ligand and the formation of [CoI–VS)]⁺ (VS = vacant site). Interestingly, DFT calculations also predict the existence of a [CoI(κ⁴-L)(OH₂)]⁺ species at least transiently, and its formation is consistent with the experimental Pourbaix diagram. Both electrochemical and kinetics results indicate that the CoI species must undergo some structural change prior to accepting the proton, and this transformation represents the rate-determining step (RDS) in the overall formation of [CoIII–H]⁺. We propose that this RDS may originate from the slow removal of a solvent ligand in the

  13. A Convenient and Efficient Protocol for the Synthesis of HBIW Catalyzed by Silica Nanoparticles under Ultrasound Irradiation

    NASA Astrophysics Data System (ADS)

    Arabian, Ramak; Ramazani, Ali; Mohtat, Bita; Azizkhani, Vahid; Joo, Sang Woo; Rouhani, Morteza

    2014-10-01

    2,4,6,8,10,12-Hexabenzyl-2,4,6,8,10,12-hexaazatetracyclo[5.5.0.05,9.03,11]dodecane (hexabenzylhexaazaisowurtzitane, HBIW) has been synthesized by the reaction of benzylamine and glyoxal (40% aqueous solution) in acetonitrile as a solvent catalyzed by silica nanoparticles (SiO2 NPs, ca. 42 nm) under ultrasound irradiation. The effects of solvent, catalyst, and ultrasonic power are discussed. With optimized reaction conditions, HBIW was synthesized under the influence of ultrasound irradiation. Compared with conventional methods, the remarkable advantages of this method are the simple experimental procedure, shorter reaction time, and high product yield.

  14. Equilibrium and kinetics analysis of carbon dioxide capture using immobilized amine on a mesoporous silica

    SciTech Connect

    Monazam, E., Shadle, L., Pennline, H., Miller, D., Fauth, D., Hoffman, J., Gray, M.

    2012-01-01

    The equilibrium and conversion-time data on the absorption of carbon dioxide (CO{sub 2}) with amine-based solid sorbent were analyzed over the range of 303–373 K. Data on CO{sub 2} loading on amine based solid sorbent at these temperatures and CO{sub 2} partial pressure between 10 and 760 mm Hg obtained from volumetric adsorption apparatus were fitted to a simple equilibrium model to generate the different parameters (including equilibrium constant) in the model. Using these constants, a correlation was obtained to define equilibrium constant and maximum CO{sub 2} loading as a function of temperature. In this study, a shrinking core model (SCM) was applied to elucidate the relative importance of pore diffusion and surface chemical reaction in controlling the rate of reaction. Application of SCM to the data suggested a surface reaction-controlled mechanism for the temperature of up to 40°C and pore-diffusion mechanism at higher temperature.

  15. Dehydrogenation of amine-borane Me2NH·BH3 catalyzed by a lanthanum-hydride complex.

    PubMed

    Cui, Peng; Spaniol, Thomas P; Maron, Laurent; Okuda, Jun

    2013-09-27

    The rare-earth-metal-hydride complexes [{(1,7-Me2TACD)LnH}4] (Ln=La 1 a, Y 1 b; (1,7-Me2TACD)H2 =1,7-dimethyl-1,4,7,10-tetraazacyclododecane, 1,7-Me2[12]aneN4) were synthesized by hydrogenolysis of [{(1,7-Me2TACD)Ln(η(3)-C3H5)}2] with 1 bar H2. The tetrameric structures were confirmed by (1)H NMR spectroscopy and single-crystal X-ray diffraction of compound 1 a. Both complexes catalyze the dehydrogenation of secondary amine-borane Me2NH·BH3 to afford the cyclic dimer (Me2NBH2)2 and (Me2N)2BH under mild conditions. Whilst the complete conversion of Me2NH·BH3 was observed within 2 h with lanthanum-hydride 1 a, the yttrium homologue 1 b required 48 h to reach 95% conversion. Further reactions of compound 1 a with Me2NH·BH3 in various stoichiometric ratios gave a series of intermediate products, [{(1,7-Me2TACD)LaH}4](Me2NBH2)2 (2 a), [(1,7-Me2TACDH)La(Me2NBH3)2] (3 a), [(1,7-Me2TACD)(Me2NBH2)La(Me2NBH3)] (4 a), and [(1,7-Me2TACD)(Me2NBH2)2La(Me2NBH3)] (5 a). Complexes 2 a, 3 a, and 5 a were isolated and characterized by multinuclear NMR spectroscopy and single-crystal X-ray diffraction studies. These intermediates revealed the activation and coordination modes of "Me2NH·BH3 " fragments that were trapped within the coordination sphere of a rare-earth-metal center. PMID:23946160

  16. Transition-metal-catalyzed C-N bond forming reactions using organic azides as the nitrogen source: a journey for the mild and versatile C-H amination.

    PubMed

    Shin, Kwangmin; Kim, Hyunwoo; Chang, Sukbok

    2015-04-21

    Owing to the prevalence of nitrogen-containing compounds in functional materials, natural products and important pharmaceutical agents, chemists have actively searched for the development of efficient and selective methodologies allowing for the facile construction of carbon-nitrogen bonds. While metal-catalyzed C-N cross-coupling reactions have been established as one of the most general protocols for C-N bond formation, these methods require starting materials equipped with functional groups such as (hetero)aryl halides or their equivalents, thus generating stoichiometric amounts of halide salts as byproducts. To address this aspect, a transition-metal-catalyzed direct C-H amination approach has emerged as a step- and atom-economical alternative to the conventional C-N cross-coupling reactions. However, despite the significant recent advances in metal-mediated direct C-H amination reactions, most available procedures need harsh conditions requiring stoichiometric external oxidants. In this context, we were curious to see whether a transition-metal-catalyzed mild C-H amination protocol could be achieved using organic azides as the amino source. We envisaged that a dual role of organic azides as an environmentally benign amino source and also as an internal oxidant via N-N2 bond cleavage would be key to develop efficient C-H amination reactions employing azides. An additional advantage of this approach was anticipated: that a sole byproduct is molecular nitrogen (N2) under the perspective catalytic conditions. This Account mainly describes our research efforts on the development of rhodium- and iridium-catalyzed direct C-H amination reactions with organic azides. Under our initially optimized Rh(III)-catalyzed amination conditions, not only sulfonyl azides but also aryl- and alkyl azides could be utilized as facile amino sources in reaction with various types of C(sp(2))-H bonds bearing such directing groups as pyridine, amide, or ketoxime. More recently, a new

  17. Effect of amine counterion type on the retention of basic compounds on octadecyl silane bonded silica-based and polybutadiene-coated zirconia phases.

    PubMed

    Yang, Xiqin; Dai, Jun; Carr, Peter W

    2003-07-01

    In a previous paper, we compared the mixed-mode retention characteristics of cationic solutes on octadecyl silane-bonded silica (ODS) and polybutadiene-coated zirconia (PBD-ZrO2) phases. It is well recognized that both reversed-phase and ion-exchange interactions contribute to the retention of cations on ODS phases. The reversed-phase interaction results from the bonded hydrocarbon chain; the ion-exchange interaction originates in the ionized residual silanol groups. These two types of interactions also exist on the PBD-ZrO2 phase. The polybutadiene contributes to the reversed-phase interaction and the ionized zirconol, but primarily, the adsorbed Lewis base anions, such as phosphate or fluoride, contribute to the ion-exchange interaction. We have shown that on ODS phases, reversed-phase interactions are much more important, whereas the opposite is true of PBD-ZrO2 phases. In this work, we investigate the effect of several amine mobile phase counterions on the retention of cationic solutes on ODS and PBD-ZrO2 phases. The effects of the chain length and the type of amine (1 degree, 2 degrees, 3 degrees) counterion on the retention of basic compounds were studied. In contrast to older studies of type A silica-based phases, the results show that the chain length and type of the amine blocker do not have a large effect on the retention of basic compounds with the newer type B silica-based materials. However, on the PBD-ZrO2 phase, very striking differences in retention were observed with different amine counterions. We show that the molecular geometry of the amine counterion has a significant effect on the retention of basic solutes on the PBD-ZrO2 phase. PMID:12964764

  18. The interaction of diamines and polyamines with the peroxidase-catalyzed metabolism of aromatic amines: a potential mechanism for the modulation of aniline toxicity.

    PubMed

    Michail, Karim; Aljuhani, Naif; Siraki, Arno G

    2013-03-01

    Synthetic and biological amines such as ethylenediamine (EDA), spermine, and spermidine have not been previously investigated in free-radical biochemical systems involving aniline-based drugs or xenobiotics. We aimed to study the influence of polyamines in the modulation of aromatic amine radical metabolites in peroxidase-mediated free radical reactions. The aniline compounds tested caused a relatively low oxidation rate of glutathione in the presence of horseradish peroxidase (HRP), and H2O2; however, they demonstrated marked oxygen consumption when a polyamine molecule was present. Next, we characterized the free-radical products generated by these reactions using spin-trapping and electron paramagnetic resonance (EPR) spectrometry. Primary and secondary but not tertiary polyamines dose-dependently enhanced the N-centered radicals of different aniline compounds catalyzed by either HRP or myeloperoxidase, which we believe occurred via charge transfer intermediates and subsequent stabilization of aniline-derived radical species as suggested by isotopically labeled aniline. Aniline/peroxidase reaction product(s) were monitored at 435 nm by kinetic spectrophotometry in the presence and absence of a polyamine additive. Using gas chromatography-mass spectrometry, the dimerziation product of aniline, azobenzene, was significantly amplified when EDA was present. In conclusion, di- and poly-amines are capable of enhancing the formation of aromatic-amine-derived free radicals, a fact that is expected to have toxicological consequences.

  19. Palladium-catalyzed C–N and C–O bond formation of N-substituted 4-bromo-7-azaindoles with amides, amines, amino acid esters and phenols

    PubMed Central

    Surasani, Rajendra; Rao, A V Dhanunjaya; Chandrasekhar, K B

    2012-01-01

    Summary Simple and efficient procedures for palladium-catalyzed cross-coupling reactions of N-substituted 4-bromo-7-azaindole (1H-pyrrole[2,3-b]pyridine), with amides, amines, amino acid esters and phenols through C–N and C–O bond formation have been developed. The C–N cross-coupling reaction of amides, amines and amino acid esters takes place rapidly by using the combination of Xantphos, Cs2CO3, dioxane and palladium catalyst precursors Pd(OAc)2/Pd2(dba)3. The combination of Pd(OAc)2, Xantphos, K2CO3 and dioxane was found to be crucial for the C–O cross-coupling reaction. This is the first report on coupling of amides, amino acid esters and phenols with N-protected 4-bromo-7-azaindole derivatives. PMID:23209536

  20. Adsorption of pesticidal compounds bearing a single carboxyl functional group and biogenic amines by humic fraction-immobilized silica gel.

    PubMed

    Chen, Cheng-Sheng; Chen, Shushi

    2013-04-17

    Fractions collected from humic acids under acidic and basic conditions were immobilized on silica gel and used as adsorbents for a variety of agricultural pesticide compounds bearing a single carboxyl functional group and biogenic amines in acetonitrile. Among these compounds examined under the same conditions, the percentage of adsorption varies considerably from 0 to almost 100%. The percentage is found to be highly related to the structure of the analyte and the type of functional group attached to it. The adsorption, better performed on adsorbent immobilized with the fraction collected under acidic conditions, is believed to result from the reversible interaction between the functional moieties of the analyte and humic acids (e.g., amino or carboxyl group of analyte vs carboxyl group of humic acids, etc.) as no adsorption is observed under the same conditions for analytes that are derivatives of alcohol, amide, and ester. Given the nature of the analyte, the time needed to reach the maximum percent of adsorption decreases as the amount of adsorbent is increased. Also, the longer the time that has elapsed, the higher the percentage of analyte adsorbed, thus indicating that the adsorption process is surface-oriented. Factors such as the acidic or basic origin of the additive in the liquid phase of the matrix also affect the percentage of analyte adsorbed. PMID:23521499

  1. Alpha-hydroxyalkyl heterocycles via chiral allylic boronates: Pd-catalyzed borylation leading to a formal enantioselective isomerization of allylic ether and amine.

    PubMed

    Lessard, Stéphanie; Peng, Feng; Hall, Dennis G

    2009-07-22

    An efficient catalytic enantioselective preparation of synthetically useful pyranyl and piperidinyl allylic boronates was achieved via a palladium-catalyzed borylation/isomerization reaction on the corresponding alkenyl triflates. The influence of the base and solvent was found to be crucial on the regio- and enantioselectivity of this reaction. The overall borylation process constitutes a successful example of formal asymmetric isomerization of allylic ether/amine. The resulting allylic boronate reagents add to various aldehydes in a one-pot process to give synthetically useful alpha-hydroxyalkyl derivatives in high stereoselectivity. PMID:19552416

  2. Copper-Catalyzed Aza-Michael Addition of Aromatic Amines or Aromatic Aza-Heterocycles to α,β-Unsaturated Olefins.

    PubMed

    Kim, Seongcheol; Kang, Seongil; Kim, Gihyeon; Lee, Yunmi

    2016-05-20

    A highly efficient and mild Cu-catalyzed conjugate addition reaction of aromatic amines and aromatic aza-heterocycles to α,β-unsaturated olefins is described. The transformation is promoted by 3-7 mol % of a Cu complex generated in situ from a mixture of inexpensive CuCl, a readily available phosphine or imidazolium salt, and KOt-Bu at ambient temperature. A wide range of β-amino sulfone, β-amino nitrile, and β-amino carbonyl compounds is efficiently and selectively synthesized in high yields (62-99%). PMID:27080327

  3. Multicomponent Synthesis of Uracil Analogues Promoted by Pd-Catalyzed Carbonylation of α-Chloroketones in the Presence of Isocyanates and Amines.

    PubMed

    Perrone, Serena; Capua, Martina; Salomone, Antonio; Troisi, Luigino

    2015-08-21

    A short and efficient one-pot synthesis of uracil derivatives with a high structural variability is described. The process is a multicomponent reaction based on a palladium-catalyzed carbonylation of α-chloroketones in the presence of primary amines and isocyanates. In most cases, when the formation of unsymmetrical N,N'-disubstituted uracil derivatives can occur, the methodology demonstrates to be highly regioselective. A mechanistic hypothesis involving β-dicarbonyl palladium intermediates and urea derivatives, generated in situ, has been discussed.

  4. Platinum-Catalyzed Friedel-Crafts-Type C-H Coupling-Allylic Amination Cascade to Synthesize 3,4-Fused Tricyclic Indoles.

    PubMed

    Suzuki, Yuta; Tanaka, Yuito; Nakano, Shun-ichi; Dodo, Kosuke; Yoda, Natsumi; Shinohara, Ken-Ichi; Kita, Kazuko; Kaneda, Atsushi; Sodeoka, Mikiko; Hamada, Yasumasa; Nemoto, Tetsuhiro

    2016-03-18

    A novel platinum-catalyzed cascade cyclization reaction was developed by intramolecular Friedel-Crafts-type C-H coupling of aniline derivatives with a propargyl carbonate unit-allylic amination sequence. Treatment of various propargyl carbonates tethered to meta-aniline derivatives with a Pt(dba)3/DPEphos catalyst system afforded the corresponding 3,4-fused tricyclic 3-alkylidene indolines in 42-99% yield, which were transformed into 3,4-fused indole derivatives by reaction with trifluoroacetic acid. The reaction products exhibited antiproliferative activities against cancer cells, but not normal cells, revealing the potential usefulness of this reaction for medicinal chemistry. PMID:26833557

  5. Amine-Impregnated Mesoporous Silica Nanotube as an Emerging Nanocomposite for CO2 Capture.

    PubMed

    Niu, Mengya; Yang, Huaming; Zhang, Xiangchao; Wang, Yutang; Tang, Aidong

    2016-07-13

    Pristine halloysite nanotubes (HNTs) were pretreated to produce mesoporous silica nanotubes (MSiNTs), which was further impregnated with polyethenimine (PEI) to prepare an emerging nanocomposite MSiNTs/PEI (MP) for CO2 capture. Thermogravimetric analysis (TGA) was employed to analyze the influences of PEI loading amount and adsorption temperature on CO2 adsorption capacity of the nanocomposite. The Brunauer-Emmett-Teller (BET) surface area (SBET) of MSiNTs was six times higher than that of HNTs, and the corresponding pore volume was more than two times higher than that of HNTs. The well dispersion of PEI within the nanotubes of MSiNTs benefits more CO2 gas adsorption, and the adsorption capacity of the nanocomposite could reach 2.75 mmol/g at 85 °C for 2 h. The CO2 adsorption on the nanocomposite was demonstrated to occur via a two-stage process: initially, a sharp linear weight increase at the beginning, and then a relatively slow adsorption step. The adsorption capacity could reach as high as 70% within 2 min. Also, the nanocomposite exhibited good stability on CO2 adsorption/desorption performance, indicating that the as-prepared emerging nanocomposite show an interesting application potential in the field of CO2 capture. PMID:27315143

  6. Acid synthesis of luminescent amine-functionalized or erbium-doped silica spheres for biological applications.

    PubMed

    Enrichi, Francesco; Trave, Enrico; Bersani, Marco

    2008-03-01

    In this work we discuss and investigate the morphological and optical properties of luminescent silica spheres which can have interesting applications in bioimaging and biosensing. The spheres are synthesized following an acid route by the hydrolysis and condensation of tetraethylortosilicate (TEOS) and can be functionalized by incorporation of aminopropyl-triethoxysilane (APTES) during the synthesis, inducing a significant luminescence that can be attributed to a recombination mechanism from localized organic defects related to -NH(2) groups. It is shown that the acid synthesis route produces very regular spherical particles, but their diameter vary in the range of 200-4,000 nm. The luminescence properties have been investigated and optimized by variation of the annealing temperature for the functionalized spheres, obtaining the most efficient PL emission after a thermal treatment of 1 h at 600 degrees C in air. Moreover, the possibility to introduce rare earths like erbium in the spheres was also studied and the corresponding Er(3) luminescence emission at 1.53 microm is reported in terms of intensity and lifetime, pointing out that erbium can be easily and efficiently incorporated during the acid synthesis giving high PL intensity with a good lifetime of 3.9 ms.

  7. Copper-catalyzed oxidative amidation of aldehydes with amine salts: synthesis of primary, secondary, and tertiary amides.

    PubMed

    Ghosh, Subhash Chandra; Ngiam, Joyce S Y; Seayad, Abdul M; Tuan, Dang Thanh; Chai, Christina L L; Chen, Anqi

    2012-09-21

    A practical method for the amidation of aldehydes with economic ammonium chloride or amine hydrochloride salts has been developed for the synthesis of a wide variety of amides by using inexpensive copper sulfate or copper(I) oxide as a catalyst and aqueous tert-butyl hydroperoxide as an oxidant. This amidation reaction is operationally straightforward and provides primary, secondary, and tertiary amides in good to excellent yields for most cases utilizing inexpensive and readily available reagents under mild conditions. In situ formation of amine salts from free amines extends the substrate scope of the reaction. Chiral amides are also synthesized from their corresponding chiral amines without detectable racemization. The practicality of this amide formation reaction has been demonstrated in an efficient synthesis of the antiarrhythmic drug N-acetylprocainamide. PMID:22894712

  8. Vanadium-catalyzed oxidative Strecker reaction: α-C-H cyanation of para-methoxyphenyl (PMP)-protected primary amines.

    PubMed

    Zhu, Chen; Xia, Ji-Bao; Chen, Chuo

    2014-01-01

    We describe an oxidative Strecker reaction that allows for direct cyanation of para-methoxyphenyl (PMP)-protected primary amines. A vanadium(V) complex was used as the catalyst and TBHP as the oxidant. The cyanation occurs at the α-C position bearing either an alkyl or an aromatic group. This method provides a direct access to α-aminonitrile from amines with one-carbon extension.

  9. Copper catalyzed oxidative ortho-C-H benzoxylation of 2-phenylpyridines with benzyl alcohols and benzyl amines as benzoxylation sources.

    PubMed

    Khemnar, Ashok B; Bhanage, Bhalchandra M

    2014-12-21

    A simple and efficient protocol for the oxidative ortho benzoxylation of 2-phenylpyridines with benzyl alcohols and benzyl amines via C-H bond activation has been developed. The present protocol uses benzyl alcohol and benzyl amine as inexpensive and easily available starting materials to afford benzoxylation products in moderate to good yields in the presence of the Cu/TBHP catalytic system. PMID:25341003

  10. Copper(II)-catalyzed oxidative N-nitrosation of secondary and tertiary amines with nitromethane under an oxygen atmosphere.

    PubMed

    Sakai, Norio; Sasaki, Minoru; Ogiwara, Yohei

    2015-07-25

    The combination of a catalytic amount of Cu(OTf)2 and less than a stoichiometric amount of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) under an O2 atmosphere effectively promoted the N-nitrosation of both secondary aromatic/aliphatic amines and tertiary aromatic amines with nitromethane (CH3NO2) leading to the preparation of N-nitrosamine derivatives.

  11. Vanadium-catalyzed oxidative Strecker reaction: α-C–H cyanation of para-methoxyphenyl (PMP)-protected primary amines

    PubMed Central

    Zhu, Chen; Xia, Ji-Bao; Chen, Chuo

    2013-01-01

    We describe an oxidative Strecker reaction that allows for direct cyanation of para-methoxyphenyl (PMP)-protected primary amines. A vanadium(V) complex was used as the catalyst and TBHP as the oxidant. The cyanation occurs at the α-C position bearing either an alkyl or an aromatic group. This method provides a direct access to α-aminonitrile from amines with one-carbon extension. PMID:24415804

  12. Is Pd(II)-promoted σ-bond metathesis mechanism operative for the Pd-PEPPSI complex-catalyzed amination of chlorobenzene with aniline? Experiment and theory.

    PubMed

    Wang, Feiqun; Zhu, Lei; Zhou, Yunfei; Bao, Xiaoguang; Schaefer, Henry F

    2015-03-01

    Reduction of the Pd-PEPPSI precatalyst to a Pd(0) species is generally thought to be essential to drive Buchwald-Hartwig amination reactions through the well-documented Pd(0)/Pd(II) catalytic cycle and little attention has been paid to other possible mechanisms. Considered here is the Pd-PEPPSI-catalyzed aryl amination of chlorobenzene with aniline. A neat reaction system was used in new experiments, from which the potentially reductive roles of the solvent and labile ligand of the PEPPSI complex in leading to Pd(0) species are ruled out. Computational results demonstrate that anilido-containing Pd(II) intermediates involving σ-bond metathesis in pathways leading to the diphenylamine product have relatively low barriers. Such pathways are more favorable energetically than the corresponding reductive elimination reactions resulting in Pd(0) species and other putative routes, such as the Pd(II)/Pd(IV) mechanism, single electron transfer mechanism, and halide atom transfer mechanism. In some special cases, if reactants/additives are inadequate to reduce a Pd(II) precatalyst, a Pd(II)-involved σ-bond metathesis mechanism might be feasible to drive the Buchwald-Hartwig amination reactions. PMID:25640144

  13. Enhanced CO2 adsorption over polymeric amines supported on heteroatom-incorporated SBA-15 silica: impact of heteroatom type and loading on sorbent structure and adsorption performance.

    PubMed

    Kuwahara, Yasutaka; Kang, Dun-Yen; Copeland, John R; Bollini, Praveen; Sievers, Carsten; Kamegawa, Takashi; Yamashita, Hiromi; Jones, Christopher W

    2012-12-21

    Silica supported amine materials are promising compositions that can be used to effectively remove CO(2) from large stationary sources, such as flue gas generated from coal-fired power plants (ca. 10 % CO(2)) and potentially from ambient air (ca. 400 ppm CO(2)). The CO(2) adsorption characteristics of prototypical poly(ethyleneimine)-silica composite adsorbents can be significantly enhanced by altering the acid/base properties of the silica support by heteroatom incorporation into the silica matrix. In this study, an array of poly(ethyleneimine)-impregnated mesoporous silica SBA-15 materials containing heteroatoms (Al, Ti, Zr, and Ce) in their silica matrices are prepared and examined in adsorption experiments under conditions simulating flue gas (10 % CO(2) in Ar) and ambient air (400 ppm CO(2) in Ar) to assess the effects of heteroatom incorporation on the CO(2) adsorption properties. The structure of the composite adsorbents, including local information concerning the state of the incorporated heteroatoms and the overall surface properties of the silicate supports, are investigated in detail to draw a relationship between the adsorbent structure and CO(2) adsorption/desorption performance. The CO(2) adsorption/desorption kinetics are assessed by thermogravimetric analysis and in situ FT-IR measurements. These combined results, coupled with data on adsorbent regenerability, demonstrate a stabilizing effect of the heteroatoms on the poly(ethyleneimine), enhancing adsorbent capacity, adsorption kinetics, regenerability, and stability of the supported aminopolymers over continued cycling. It is suggested that the CO(2) adsorption performance of silica-aminopolymer composites may be further enhanced in the future by more precisely tuning the acid/base properties of the support. PMID:23165918

  14. A Highly Efficient Gold-Catalyzed Photoredox α-C(sp(3))-H Alkynylation of Tertiary Aliphatic Amines with Sunlight.

    PubMed

    Xie, Jin; Shi, Shuai; Zhang, Tuo; Mehrkens, Nina; Rudolph, Matthias; Hashmi, A Stephen K

    2015-05-11

    A new α-C(sp(3))H alkynylation of unactivated tertiary aliphatic amines with 1-iodoalkynes as radical alkynylating reagents in the presence of [Au2(μ-dppm)2](2+) in sunlight provides propargylic amines. Based on mechanistic studies, a C-C coupling of an α-aminoalkyl radical and an alkynyl radical is proposed for the C(sp(3))-C(sp) bond formation. The mild, convenient, efficient, and highly selective C(sp(3))-H alkynylation reaction shows excellent regioselectivity and good functional-group compatibility. A scale-up to gram quantities is possible with sunlight used as a clean and sustainable energy source.

  15. Organoselenium-catalyzed, hydroxy-controlled regio- and stereoselective amination of terminal alkenes: efficient synthesis of 3-amino allylic alcohols.

    PubMed

    Deng, Zhimin; Wei, Jialiang; Liao, Lihao; Huang, Haiyan; Zhao, Xiaodan

    2015-04-17

    An efficient route to prepare 3-amino allylic alcohols in excellent regio- and stereoselectivity in the presence of bases by orangoselenium catalysis has been developed. In the absence of bases α,β-unsaturated aldehydes were formed in up to 97% yield. Control experiments reveal that the hydroxy group is crucial for the direct amination. PMID:25849818

  16. Soluble B-N polymers: poly(alpha-olefin) analogs via metal complex-catalyzed amine borane dehydrogenation

    SciTech Connect

    Pons, Vincent; Baker, R Tom

    2008-01-01

    Over the last few decades, catalytic dehydrocoupling has evolved from a mechanistically interesting chemical transformation to a practical route to inorganic polymers that have shown utility as new materials and processable ceramic precursors. In attempting to make new B-P and B-N inorganic polymers, Manners et al studied the heteronuclear dehydrocoupling of phosphine boranes and amine boranes. While the former gave high polymers such as (PhHP-BH2), evaluation of a variety of catalysts with primary and secondary amine boranes or even ammonia borane lead only to B-N cyclic oligomers. However, using an iridium phosphinito pincer complex originally employed by Goldberg and Heinekey6 for dehydrogenation of ammonia borane (AB, H3N-BH3), M3.nners now reports formation of soluble aminoborane polymers and copolymers derived from primary amine boranes (Scheme 1) With this report, an analogy is made between primary amine boranes and {alpha}-olefins. The prospects of tuning metal complex catalysts for control of B-N polymer microstructure are exciting for synthesis of new B-N materials. In addition, variation of the N substituent offers promise for processable precllISors to carbon-free B-N ceramics.

  17. Enantioselective Synthesis of 3a-Amino-Pyrroloindolines by Copper-Catalyzed Direct Asymmetric Dearomative Amination of Tryptamines.

    PubMed

    Liu, Chuan; Yi, Ji-Cheng; Zheng, Zhong-Bo; Tang, Yong; Dai, Li-Xin; You, Shu-Li

    2016-01-11

    A direct asymmetric dearomative amination of tryptamines with O-(2,4-dinitrophenyl)hydroxylamine (DPH) was achieved using CuBr-bisoxazoline complex as a catalyst, affording 3a-amino-pyrroloindolines in good to excellent enantioselectivity under mild reaction conditions. Furthermore, the synthetic value of this method was demonstrated in the total synthesis of (-)-psychotriasine in a highly concise manner. PMID:26603145

  18. Bifunctional heterogeneous catalysis of silica-alumina-supported tertiary amines with controlled acid-base interactions for efficient 1,4-addition reactions.

    PubMed

    Motokura, Ken; Tanaka, Satoka; Tada, Mizuki; Iwasawa, Yasuhiro

    2009-10-19

    We report the first tunable bifunctional surface of silica-alumina-supported tertiary amines (SA-NEt(2)) active for catalytic 1,4-addition reactions of nitroalkanes and thiols to electron-deficient alkenes. The 1,4-addition reaction of nitroalkanes to electron-deficient alkenes is one of the most useful carbon-carbon bond-forming reactions and applicable toward a wide range of organic syntheses. The reaction between nitroethane and methyl vinyl ketone scarcely proceeded with either SA or homogeneous amines, and a mixture of SA and amines showed very low catalytic activity. In addition, undesirable side reactions occurred in the case of a strong base like sodium ethoxide employed as a catalytic reagent. Only the present SA-supported amine (SA-NEt(2)) catalyst enabled selective formation of a double-alkylated product without promotions of side reactions such as an intramolecular cyclization reaction. The heterogeneous SA-NEt(2) catalyst was easily recovered from the reaction mixture by simple filtration and reusable with retention of its catalytic activity and selectivity. Furthermore, the SA-NEt(2) catalyst system was applicable to the addition reaction of other nitroalkanes and thiols to various electron-deficient alkenes. The solid-state magic-angle spinning (MAS) NMR spectroscopic analyses, including variable-contact-time (13)C cross-polarization (CP)/MAS NMR spectroscopy, revealed that acid-base interactions between surface acid sites and immobilized amines can be controlled by pretreatment of SA at different temperatures. The catalytic activities for these addition reactions were strongly affected by the surface acid-base interactions.

  19. Amine-free reversible hydrogen storage in formate salts catalyzed by ruthenium pincer complex without pH control or solvent change.

    PubMed

    Kothandaraman, Jotheeswari; Czaun, Miklos; Goeppert, Alain; Haiges, Ralf; Jones, John-Paul; May, Robert B; Prakash, G K Surya; Olah, George A

    2015-04-24

    Due to the intermittent nature of most renewable energy sources, such as solar and wind, energy storage is increasingly required. Since electricity is difficult to store, hydrogen obtained by electrochemical water splitting has been proposed as an energy carrier. However, the handling and transportation of hydrogen in large quantities is in itself a challenge. We therefore present here a method for hydrogen storage based on a CO2 (HCO3 (-) )/H2 and formate equilibrium. This amine-free and efficient reversible system (>90 % yield in both directions) is catalyzed by well-defined and commercially available Ru pincer complexes. The formate dehydrogenation was triggered by simple pressure swing without requiring external pH control or the change of either the solvent or the catalyst. Up to six hydrogenation-dehydrogenation cycles were performed and the catalyst performance remained steady with high selectivity (CO free H2 /CO2 mixture was produced). PMID:25824142

  20. Amine-free reversible hydrogen storage in formate salts catalyzed by ruthenium pincer complex without pH control or solvent change.

    PubMed

    Kothandaraman, Jotheeswari; Czaun, Miklos; Goeppert, Alain; Haiges, Ralf; Jones, John-Paul; May, Robert B; Prakash, G K Surya; Olah, George A

    2015-04-24

    Due to the intermittent nature of most renewable energy sources, such as solar and wind, energy storage is increasingly required. Since electricity is difficult to store, hydrogen obtained by electrochemical water splitting has been proposed as an energy carrier. However, the handling and transportation of hydrogen in large quantities is in itself a challenge. We therefore present here a method for hydrogen storage based on a CO2 (HCO3 (-) )/H2 and formate equilibrium. This amine-free and efficient reversible system (>90 % yield in both directions) is catalyzed by well-defined and commercially available Ru pincer complexes. The formate dehydrogenation was triggered by simple pressure swing without requiring external pH control or the change of either the solvent or the catalyst. Up to six hydrogenation-dehydrogenation cycles were performed and the catalyst performance remained steady with high selectivity (CO free H2 /CO2 mixture was produced).

  1. Ruthenium-Catalyzed Oxidative Coupling of Primary Amines with Internal Alkynes through C-H Bond Activation: Scope and Mechanistic Studies.

    PubMed

    Ruiz, Sara; Villuendas, Pedro; Ortuño, Manuel A; Lledós, Agustí; Urriolabeitia, Esteban P

    2015-06-01

    The oxidative coupling of primary amines with internal alkynes catalyzed by Ru complexes is presented as a general atom-economy methodology with a broad scope of applications in the synthesis of N-heterocycles. Reactions proceed through regioselective C-H bond activation in 15 minutes under microwave irradiation or in 24 hours with conventional heating. The synthesis of 2,3,5-substituted pyridines, benzo[h]isoquinolines, benzo[g]isoquinolines, 8,9-dihydro-benzo[de]quinoline, 5,6,7,8-tetrahydroisoquinolines, pyrido[3,4g]isoquinolines, and pyrido[4,3g]isoquinolines is achievable depending on the starting primary amine used. DFT calculations on a benzylamine substrate support a reaction mechanism that consists of acetate-assisted C-H bond activation, migratory-insertion, and C-N bond formation steps that involve 28-30 kcal mol(-1) . The computational study is extended to additional substrates, namely, 1-naphthylmethyl-, 2-methylallyl-, and 2-thiophenemethylamines.

  2. Ruthenium-Catalyzed Oxidative Coupling of Primary Amines with Internal Alkynes through C-H Bond Activation: Scope and Mechanistic Studies.

    PubMed

    Ruiz, Sara; Villuendas, Pedro; Ortuño, Manuel A; Lledós, Agustí; Urriolabeitia, Esteban P

    2015-06-01

    The oxidative coupling of primary amines with internal alkynes catalyzed by Ru complexes is presented as a general atom-economy methodology with a broad scope of applications in the synthesis of N-heterocycles. Reactions proceed through regioselective C-H bond activation in 15 minutes under microwave irradiation or in 24 hours with conventional heating. The synthesis of 2,3,5-substituted pyridines, benzo[h]isoquinolines, benzo[g]isoquinolines, 8,9-dihydro-benzo[de]quinoline, 5,6,7,8-tetrahydroisoquinolines, pyrido[3,4g]isoquinolines, and pyrido[4,3g]isoquinolines is achievable depending on the starting primary amine used. DFT calculations on a benzylamine substrate support a reaction mechanism that consists of acetate-assisted C-H bond activation, migratory-insertion, and C-N bond formation steps that involve 28-30 kcal mol(-1) . The computational study is extended to additional substrates, namely, 1-naphthylmethyl-, 2-methylallyl-, and 2-thiophenemethylamines. PMID:25916684

  3. Sustainable Pathways to Pyrroles through Iron-Catalyzed N-Heterocyclization from Unsaturated Diols and Primary Amines.

    PubMed

    Yan, Tao; Barta, Katalin

    2016-09-01

    Pyrroles are prominent scaffolds in pharmaceutically active compounds and play an important role in medicinal chemistry. Therefore, the development of new, atom-economic, and sustainable catalytic strategies to obtain these moieties is highly desired. Direct catalytic pathways that utilize readily available alcohol substrates have been recently established; however, these approaches rely on the use of noble metals such as ruthenium or iridium. Here, we report on the direct synthesis of pyrroles using a catalyst based on the earth-abundant and inexpensive iron. The method uses 2-butyne-1,4-diol or 2-butene-1,4-diol that can be directly coupled with anilines, benzyl amines, and aliphatic amines to obtain a variety of N-substituted pyrroles in moderate-to-excellent isolated yields.

  4. Sustainable Pathways to Pyrroles through Iron-Catalyzed N-Heterocyclization from Unsaturated Diols and Primary Amines.

    PubMed

    Yan, Tao; Barta, Katalin

    2016-09-01

    Pyrroles are prominent scaffolds in pharmaceutically active compounds and play an important role in medicinal chemistry. Therefore, the development of new, atom-economic, and sustainable catalytic strategies to obtain these moieties is highly desired. Direct catalytic pathways that utilize readily available alcohol substrates have been recently established; however, these approaches rely on the use of noble metals such as ruthenium or iridium. Here, we report on the direct synthesis of pyrroles using a catalyst based on the earth-abundant and inexpensive iron. The method uses 2-butyne-1,4-diol or 2-butene-1,4-diol that can be directly coupled with anilines, benzyl amines, and aliphatic amines to obtain a variety of N-substituted pyrroles in moderate-to-excellent isolated yields. PMID:27493031

  5. Selective iridium-catalyzed alkylation of (hetero)aromatic amines and diamines with alcohols under mild reaction conditions.

    PubMed

    Blank, Benoît; Michlik, Stefan; Kempe, Rhett

    2009-01-01

    A P,N-ligand-coordinated iridium complex has been employed as an efficient catalyst for the selective monoalkylation of (hetero)aromatic amines with alcohols. A significant improvement of this alkylation method has been achieved, such that it can be performed at a temperature of 70 degrees C and with catalyst loadings as low as 0.1 mol % Ir, while still affording excellent yields of secondary amines. Furthermore, the high selectivity of this catalyst for the monoalkylation of aromatic amino functions has been successfully exploited for the alkylation of diamines in both symmetric and nonsymmetric fashions, providing a novel and very efficient synthetic tool for the preparation of N,N'-dialkylated aromatic diamines.

  6. Interplay between hydrido/dihydrogen and amine/amido ligands in ruthenium-catalyzed transfer hydrogenation of ketones.

    PubMed

    Picot, Alexandre; Dyer, Hellen; Buchard, Antoine; Auffrant, Audrey; Vendier, Laure; Le Floch, Pascal; Sabo-Etienne, Sylviane

    2010-02-15

    This work describes the synthesis of three key intermediates of Noyori-type catalytic systems that are active precatalysts for the transfer hydrogenation of acetophenone. Isolation of the cationic chloro(dihydrogen) complex [RuCl(H(2))(H(2)NNPP)(PCy(3))][BArf(4)] provides a facile synthetic route to the corresponding cationic and neutral hydrido complexes, and the series highlights the links between hydride/dihydrogen and amine/amido ligands in neutral and cationic species. PMID:20095639

  7. Amination of aryl halides with aqueous ammonia catalyzed by green recyclable poly(4-vinylpyridine)-supported copper iodide nanoparticles catalyst.

    PubMed

    Albadi, Jalal; Shiran, Jafar Abbasi; Mansournezhad, Azam

    2014-01-01

    In this research efficient procedure for the amination of aryl halides with aqueous ammonia in the presence of poly(4-vinylpyridine)-supported copper iodide nanoparticles catalyst is reported. A wide range of aryl halides including aryl iodides and aryl bromides are converted into the corresponding aniline derivatives. The experimental procedure with poly(4-vinylpyridine)-supported copper iodide nanoparticles catalyst is quite straightforward and it is recycled up to 3 consecutive runs by simple filtration. PMID:25551733

  8. Rhodium(II)-catalyzed alkyne amination of homopropargylic sulfamate esters: stereoselective synthesis of functionalized norcaradienes by arene cyclopropanation.

    PubMed

    Brawn, Ryan A; Zhu, Kaicheng; Panek, James S

    2014-01-01

    A rhodium(II) catalyzed nitrene-alkyne cycloaddition of stereochemically well-defined homopropargylic ethers is followed by arene cyclopropanation to afford unique tetracyclic norcaradiene products bearing a cyclic sulfamate. Products from the arene cyclopropanation (Buchner reaction) can be converted to fused cycloheptatrienes via a ring enlarging electrocyclization after nucleophilic ring opening of the cyclic sulfamate ester.

  9. Palladium-catalyzed one-pot three- or four-component coupling of aryl iodides, alkynes, and amines through C-N bond cleavage: efficient synthesis of indole derivatives.

    PubMed

    Hao, Wei; Geng, Weizhi; Zhang, Wen-Xiong; Xi, Zhenfeng

    2014-02-24

    An efficient synthesis of N-substituted indole derivatives was realized by combining the Pd-catalyzed one-pot multicomponent coupling approach with cleavage of the C(sp(3))-N bonds. Three or four components of aryl iodides, alkynes, and amines were involved in this coupling process. The cyclopentadiene-phosphine ligand showed high efficiency. A variety of aryl iodides, including cyclic and acyclic tertiary amino aryl iodides, and substituted 1-bromo-2-iodobenzene derivatives could be used. Both symmetric and unsymmetric alkynes substituted with alkyl, aryl, or trimethylsilyl groups could be applied. Cyclic secondary amines such as piperidine, morpholine, 4-methylpiperidine, 1-methylpiperazine, 2-methylpiperidine, and acyclic amines including secondary and primary amines all showed good reactivity. Further application of the resulting indole derivatives was demonstrated by the synthesis of benzosilolo[2,3-b]indole.

  10. Enantioselective Nucleophilic β-Carbon-Atom Amination of Enals: Carbene-Catalyzed Formal [3+2] Reactions.

    PubMed

    Wu, Xingxing; Liu, Bin; Zhang, Yuexia; Jeret, Martin; Wang, Honglin; Zheng, Pengcheng; Yang, Song; Song, Bao-An; Chi, Yonggui Robin

    2016-09-26

    An enantioselective β-carbon amination for enals is disclosed. The nitrogen atom from a protected hydrazine with suitable electronic properties readily behaves as a nucleophile. Addition of the nitrogen nucleophile to a catalytically generated N-heterocyclic-carbene-bound α,β-unsaturated acyl azolium intermediate constructs a new carbon-nitrogen bond asymmetrically. The pyrazolidinone products from our catalytic reactions are common scaffolds in bioactive molecules, and can be easily transformed into useful compounds such as β(3) -amino-acid derivatives. PMID:27596365

  11. Generation of reactive species and fate of thiols during peroxidase-catalyzed metabolic activation of aromatic amines and phenols

    SciTech Connect

    Ross, D.; Moldeus, P.

    1985-12-01

    The horseradish peroxidase (HRP)-catalyzed oxidation of p-phenetidine and acetaminophen was investigated. Studies using the spin probe 2-ethyl-1-hydroxy-2,5,5-trimethyl-3-oxazolidine (OXANOH) suggested these oxidations involve the generation of substrate-derived free radicals. This was confirmed by using glutathione (GSH) in these incubations in the presence of the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), DMPO-glutathionyl radical adducts were observed using EPR spectroscopy during HRP-catalyzed oxidation of both p-phenetidine and acetaminophen. Investigations of oxygen uptake and oxidized glutathione (GSSG) formation during HRP-catalyzed oxidations of p-phenetidine and acetaminophen suggested that further reactions of the glutathionyl radical involve glutathione peroxysulfenyl radical and glutathione sulfenyl hydroperoxide production. Quinonoid products of the peroxidatic oxidations of p-phenetidine and acetaminophen, and their interaction with GSH via both conjugation and redox mechanisms are described. The relevance of these reactions of GSH with reactive species as detoxification mechanisms is discussed. 29 references.

  12. CYP-450 isoenzymes catalyze the generation of hazardous aromatic amines after reaction with the azo dye Sudan III.

    PubMed

    Zanoni, Thalita Boldrin; Lizier, Thiago M; Assis, Marilda das Dores; Zanoni, Maria Valnice B; de Oliveira, Danielle Palma

    2013-07-01

    This work describes the mutagenic response of Sudan III, an adulterant food dye, using Salmonella typhimurium assay and the generation of hazardous aromatic amines after different oxidation methods of this azo dye. For that, we used metabolic activation by S9, catalytic oxidation by ironporphyrin and electrochemistry oxidation in order to simulate endogenous oxidation conditions. The oxidation reactions promoted discoloration from 65% to 95% of Sudan III at 1 × 10(-4)molL(-1) and generation of 7.6 × 10(-7)molL(-1) to 0.31 × 10(-4)molL(-1) of aniline, o-anisidine, 2-methoxi-5-methylaniline, 4-aminobiphenyl, 4,4'-oxydianiline; 4,4'-diaminodiphenylmethane and 2,6-dimethylaniline. The results were confirmed by LC-MS-MS experiments. We also correlate the mutagenic effects of Sudan III using S. typhimurium with the strain TA1535 in the presence of exogenous metabolic activation (S9) with the metabolization products of this compound. Our findings clearly indicate that aromatic amines are formed due to oxidative reactions that can be promoted by hepatic cells, after the ingestion of Sudan III. Considering that, the use of azo compounds as food dyestuffs should be carefully controlled. PMID:23562707

  13. Tandem hydrogenation and condensation of fluorinated α,β-unsaturated ketones with primary amines, catalyzed by nickel.

    PubMed

    Castellanos-Blanco, Nahury; Flores-Alamo, Marcos; García, Juventino J

    2015-09-21

    A simple homogeneous catalytic system based on nickel phosphine complexes has been developed for the transfer hydrogenation and condensation of α,β-unsaturated ketones to yield saturated ones and saturated imines using primary amines as hydrogen donors. Thus, a wide range of fluorinated 1,5-diaryl-1,4-pentadiene-3-ones were allowed to react with substituted benzylamines in the presence of [(dippe)Ni(μ-H)]2 (dippe = 1,2-bis-(diisopropylphosphino)-ethane) using ethanol as a solvent at 180 °C to give the corresponding saturated carbonyl compounds; here hydrogenation of the C[double bond, length as m-dash]C bond was preferred over the C[double bond, length as m-dash]O bond. Under the same reaction conditions but using an excess of benzylamine, a tandem process is then favoured, starting also with the reduction of the C[double bond, length as m-dash]C bond followed by a nucleophilic addition of the primary amine to yield valuable saturated imines with good to excellent yields (62%-91%). PMID:26250992

  14. Electrochemical Oxidation of H₂ Catalyzed by Ruthenium Hydride Complexes Bearing P₂N₂ Ligands With Pendant Amines as Proton Relays

    SciTech Connect

    Liu, Tianbiao L.; Rakowski DuBois, Mary; DuBois, Daniel L.; Bullock, R. Morris

    2014-01-01

    Two Ru hydride complexes (Cp*Ru(PPh₂NBn₂)H, (1-H) and Cp*Ru(PtBu₂NBn₂)H, (2-H) supported by cyclic PR₂NR'₂ ligands (Cp* = n⁵-C₅Me₅; 1,5-diaza-3,7-diphosphacyclooctane, where R = Ph or tBu and R' = Bn) have been synthesized and fully characterized. Both complexes are demonstrated to be electrocatalysts for oxidation of H₂ (1 atm, 22 °C) in the presence of external base, DBU (1,8-diazabicyclo[5.4.0]undec-7-ene). The turnover frequency of 2-H is 1.2 s-1, with an overpotential at Ecat/2 of 0.45 V, while catalysis by 1-H has a turnover frequency of 0.6 s-1 and an overpotential of 0.6 V at Ecat/2. Addition of H₂O facilitates oxidation of H₂ by 2-H and increases its turnover frequency to 1.9 s-1 while , H₂O slows down the catalysis by 1-H. The different effects of H₂O for 1-H and 2-H are ascribed to different binding affinities of H₂O to the Ru center of the corresponding unsaturated species, [Cp*Ru(PPh₂NBn₂)]+ and [Cp*Ru(PPh₂NBn₂)]+. In addition, studies of Cp*Ru(dmpm)H (where dmpm = bis(dimethylphosphino)methane), a control complex lacking pendent amines in its diphosphine ligand, confirms the critical roles of the pendent amines of P₂N₂ ligands for oxidation of H₂. We thank the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences, for supporting initial parts of the work. Current work is supported by the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  15. Pd-catalyzed amination in the synthesis of a new family of macropolycyclic compounds comprising diazacrown ether moieties.

    PubMed

    Yakushev, Alexei A; Chernichenko, Nataliya M; Anokhin, Maxim V; Averin, Alexei D; Buryak, Alexei K; Denat, Franck; Beletskaya, Irina P

    2014-01-01

    N,N'-bis(bromobenzyl) and N,N'-bis(halopyridinyl) derivatives of diaza-12-crown-4, diaza-15-crown-5 and diaza-18-crown-6 ethers were synthesized in high yields. The Pd-catalyzed macrocyclization reactions of these compounds were carried out using a variety of polyamines and oxadiamines were carried out to give novel macrobicyclic and macrotricyclic compounds of the cryptand type. The dependence of the yields of macropolycycles on the nature of the starting diazacrown derivatives and polyamines was established. Generally N,N'-bis(3-bromobenzyl)-substituted diazacrown ethers and oxadiamines provided better yields of the target products. The highest yield of the macrobicyclic products reached 57%. PMID:24434669

  16. A Bis(silylene)-Substituted ortho-Carborane as a Superior Ligand in the Nickel-Catalyzed Amination of Arenes.

    PubMed

    Zhou, Yu-Peng; Raoufmoghaddam, Saeed; Szilvási, Tibor; Driess, Matthias

    2016-10-01

    The synthesis and structure of the first 1,2-bis(NHSi)-substituted ortho-carborane [(LSi:)C]2 B10 H10 (termed SiCCSi) is reported (NHSi=N-heterocyclic silylene; L=PhC(NtBu)2 ). Its suitability to serve as a reliable bis(silylene) chelating ligand for transition metals is demonstrated by the formation of [SiCCSi]NiBr2 and [SiCCSi]Ni(CO)2 complexes. The CO stretching vibration modes of the latter indicate that the Si(II) atoms in the SiCCSi ligand are even stronger σ donors than the P(III) atoms in phosphines and C(II) atoms in N-heterocyclic carbene (NHC) ligands. Moreover, the strong donor character of the [SiCCSi] ligand enables [SiCCSi]NiBr2 to act as an outstanding precatalyst (0.5 mol % loading) in the catalytic aminations of arenes, surpassing the activity of previously known molecular Ni-based precatalysts (1-10 mol %). PMID:27628158

  17. Structural changes of silica mesocellular foam supported amine-functionalized CO2 adsorbents upon exposure to steam.

    PubMed

    Li, Wen; Bollini, Praveen; Didas, Stephanie A; Choi, Sunho; Drese, Jeffrey H; Jones, Christopher W

    2010-11-01

    Three classes of amine-functionalized mesocellular foam (MCF) materials are prepared and evaluated as CO(2) adsorbents. The stability of the adsorbents under steam/air and steam/nitrogen conditions is investigated using a Parr autoclave reactor to simulate, in an accelerated manner, the exposure that such adsorbents will see under steam stripping regeneration conditions at various temperatures. The CO(2) capacity and organic content of all adsorbents decrease after steam treatment under both steam/air and steam/nitrogen conditions, primarily due to structural collapse of the MCF framework, but with additional contributions likely associated with amine degradation during treatment under harsh conditions. Treatment with steam/air is found to have stronger effect on the CO(2) capacity of the adsorbents compared to steam/nitrogen.

  18. Amine-Catalyzed Highly Regioselective and Stereoselective C(sp(2) )-C(sp(2) ) Cross-Coupling of Naphthols with trans-α,β-Unsaturated Aldehydes.

    PubMed

    Hu, Yang; Ma, Yueyue; Sun, Rengwei; Yu, Xinhong; Xie, Hexin; Wang, Wei

    2015-09-01

    A metal-free C(sp(2) )-C(sp(2) ) cross-coupling approach to highly congested (E)-α-naphtholylenals from simple naphthols and enals is described. The mild reaction conditions with pyridine hydrobromideperbromide (PHBP) as the bromination reagent in the presence of piperidine or diphenylprolinol trimethylsilyl (TMS) ether as promoters enable the process in good yields and with high chemoselectivity, regioselectivity, and stereoselectivity. The process involves an unprecedented pathway of in situ regioselective 4-bromination of 1-naphthols and the subsequent unusual aromatic nucleophilic substitution of the resulting 4-bromo-1-naphthols with the α-C(sp(2) ) of enals through a Michael-type Friedel-Crafts alkylation-dearomatization followed by a cyclopropanation ring-opening cascade process. The noteworthy features of this strategy are highlighted by the highly efficient creation of a C(sp(2) )-C(sp(2) ) bond from readily available unfunctionalized naphthols and enals catalyzed by non-metal, readily available cyclic secondary amines under mild reaction conditions. PMID:26096893

  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. Multifunctional mesoporous silica catalyst

    DOEpatents

    Lin, Victor Shang-Yi; Tsai, Chih-Hsiang; Chen, Hung-Ting; Pruski, Marek; Kobayashi, Takeshi

    2015-03-31

    The present invention provides bifunctional silica mesoporous materials, including mesoporous silica nanoparticles ("MSN"), having pores modified with diarylammonium triflate and perfluoroaryl moieties, that are useful for the acid-catalyzed esterification of organic acids with organic alcohols.

  1. Fluorescence and Textural Characterization of Ortho-Amine Tetraphenylporphyrin Covalently Bonded to Organo-Modified Silica Xerogels.

    PubMed

    García-Sánchez, M A; Serratos, I N; Sosa, R; Rojas-González, F; Tello-Solís, S R; Tapia-Esquivel, T; González-García, F; Esparza-Schulz, J M; Huerta-Figueroa, D E

    2016-09-01

    Most of the studies performed with porphyrins involve these species functionalized with peripheral substituents lying on the same macrocyclic molecular plane. The main objective of this work deals with the successful preservation and optimization of the fluorescence of a uncommonly used porphyrin species, i.e. tetrakis-(ortho-amino-phenyl)-porphyrin; a molecule with substituents localized not only at one but at both sides of its molecular plane. In cases like this, it must be stressed that fluorescence can only be partially preserved; nevertheless, intense fluorescence can still be reached by following a twofold functionalization strategy involving: (i) the bonding of substituted macrocycles to the pore walls of (ii) organo-modified silica monoliths synthesized by the sol-gel method. The analysis of both absorption and emission UV spectra evidenced a radiation energy transfer taking place between the porphyrin and the host silica matrix. Our results showed that the adequate displaying of the optical properties of macrocyclic species trapped in SiO2 xerogels depend on the polarity existing inside the pores, a property which can be tuned up through the adequate selection of organic groups used to modify the surface of the pore cavities. Additionally, the pore widths attained in the final xerogels can vary depending on the identity of the organic groups attached to the network. All these facts finally demonstrated that, even if using inefficient surface functionalization species, such as ortho-substituted tetraphenylporphyrins, it is still possible to modulate the pore shape, pore size, and physicochemical environment created around the trapped macrocycles. The most important aspect related to this research deals with the fact that the developed methodology offers a real possibility of controlling both the textural and morphological characteristics of a new kind of hybrid porous materials and to optimize the physicochemical properties of diverse active molecules

  2. Fluorescence and Textural Characterization of Ortho-Amine Tetraphenylporphyrin Covalently Bonded to Organo-Modified Silica Xerogels.

    PubMed

    García-Sánchez, M A; Serratos, I N; Sosa, R; Rojas-González, F; Tello-Solís, S R; Tapia-Esquivel, T; González-García, F; Esparza-Schulz, J M; Huerta-Figueroa, D E

    2016-09-01

    Most of the studies performed with porphyrins involve these species functionalized with peripheral substituents lying on the same macrocyclic molecular plane. The main objective of this work deals with the successful preservation and optimization of the fluorescence of a uncommonly used porphyrin species, i.e. tetrakis-(ortho-amino-phenyl)-porphyrin; a molecule with substituents localized not only at one but at both sides of its molecular plane. In cases like this, it must be stressed that fluorescence can only be partially preserved; nevertheless, intense fluorescence can still be reached by following a twofold functionalization strategy involving: (i) the bonding of substituted macrocycles to the pore walls of (ii) organo-modified silica monoliths synthesized by the sol-gel method. The analysis of both absorption and emission UV spectra evidenced a radiation energy transfer taking place between the porphyrin and the host silica matrix. Our results showed that the adequate displaying of the optical properties of macrocyclic species trapped in SiO2 xerogels depend on the polarity existing inside the pores, a property which can be tuned up through the adequate selection of organic groups used to modify the surface of the pore cavities. Additionally, the pore widths attained in the final xerogels can vary depending on the identity of the organic groups attached to the network. All these facts finally demonstrated that, even if using inefficient surface functionalization species, such as ortho-substituted tetraphenylporphyrins, it is still possible to modulate the pore shape, pore size, and physicochemical environment created around the trapped macrocycles. The most important aspect related to this research deals with the fact that the developed methodology offers a real possibility of controlling both the textural and morphological characteristics of a new kind of hybrid porous materials and to optimize the physicochemical properties of diverse active molecules

  3. Pd/C-Catalyzed Aminocarbonylation of Aryl Iodides via Oxidative C-N Bond Activation of Tertiary Amines to Tertiary Amides.

    PubMed

    Mane, Rajendra S; Bhanage, Bhalchandra M

    2016-02-01

    This work reports oxidative N-dealkylation/carbonylation of tertiary amines to tertiary amides by using molecular oxygen as a sole oxidant using a Pd/C catalyst. This protocol is free from ligands, additives, bases, and cocatalysts. Different tertiary amines as well as aryl iodides have been examined for this transformation, providing desired products in good to excellent yield. PMID:26756705

  4. Sodium hydroxide catalyzed N-alkylation of (hetero) aromatic primary amines and N1,C5-dialkylation of 4-phenyl-2-aminothiazoles with benzyl alcohols.

    PubMed

    Donthiri, Ramachandra Reddy; Pappula, Venkatanarayana; Mohan, Darapaneni Chandra; Gaywala, Hiren H; Adimurthy, Subbarayappa

    2013-07-01

    In the presence of a catalytic amount of NaOH, the selective N-alkylation of various heteroaromatic primary amines is reported. With 1 equiv of NaOH, N1,C5-dialkylation of 4-phenyl-2-aminothiazoles has been investigated. Reaction of in situ generated aldehyde with amine yields the N-alkylated and N1,C5-dialkylated products through hydride ion transformation from alcohol.

  5. [Rh(III)(Cp*)]-catalyzed ortho-selective direct C(sp(2))-H bond amidation/amination of benzoic acids by N-chlorocarbamates and N-chloromorpholines. A versatile synthesis of functionalized anthranilic acids.

    PubMed

    Ng, Fo-Ning; Zhou, Zhongyuan; Yu, Wing-Yiu

    2014-04-01

    A Rh(III) -catalyzed direct ortho-CH amidation/amination of benzoic acids with N-chlorocarbamates/N-chloromorpholines was achieved, giving anthranilic acids in up to 85 % yields with excellent ortho-selectivity and functional-group tolerance. Successful benzoic acid aminations were achieved with carbamates bearing various amide groups including NHCO2 Me, NHCbz, and NHTroc (Cbz=carbobenzyloxy; Troc=trichloroethylchloroformate), as well as secondary amines, such as morpholines, piperizines, and piperidines, furnishing highly functionalized anthranilic acids. A stoichiometric reaction of a cyclometallated rhodium(III) complex of benzo[h]quinoline with a silver salt of N-chlorocarbamate afforded an amido-rhodium(III) complex, which was isolated and structurally characterized by X-ray crystallography. This finding confirmed that the CN bond formation results from the cross-coupling of N-chlorocarbamate with the aryl-rhodium(III) complex. Yet, the mechanistic details regarding the CN bond formation remain unclear; pathways involving 1,2-aryl migration and rhodium(V)- nitrene are plausible. PMID:24596116

  6. Cyclooctane metathesis catalyzed by silica-supported tungsten pentamethyl [(≡SiO)W(Me)5]: distribution of macrocyclic alkanes.

    PubMed

    Riache, Nassima; Callens, Emmanuel; Samantaray, Manoja K; Kharbatia, Najeh M; Atiqullah, Muhammad; Basset, Jean-Marie

    2014-11-10

    Metathesis of cyclic alkanes catalyzed by the new surface complex [(≡SiO)W(Me)5] affords a wide distribution of cyclic and macrocyclic alkanes. The major products with the formula C(n)H(2n) are the result of either a ring contraction or ring expansion of cyclooctane leading to lower unsubstituted cyclic alkanes (5≤n≤7) and to an unprecedented distribution of unsubstituted macrocyclic alkanes (12≤n≤40), respectively, identified by GC/MS and by NMR spectroscopies.

  7. Catalyzed oxidative degradation of methyl orange over Au catalyst prepared by ionic liquid-polymer modified silica

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Guo, J. S.

    2015-07-01

    A new type of hybrid material was prepared by grafting an ionic liquid monomer, 1-(p-vinylbenzyl)-3-methylimidazolium chloride, on the surface of the porous silica which was synthesized via sodium silicate hydrolysis. The as-synthesized products were characterized by scanning electron microscope, nitrogen physisorption experiment, thermogravimetric analysis and Fourier transform infrared spectra. A catalyst with Au was prepared using the hybrid material as carrier. The experimental results show that the catalyst exhibits a better catalytic effect of hydrogen peroxide on the degradation of methyl orange. The reason may be that the metal component of the catalyst facilitated the dissociation of hydrogen peroxide to produce abundant highly active free radicals which can rapidly ruin the structure of methyl orange molecules in water. Finally, a probable catalytic degradation mechanism based on diffusion was discussed.

  8. Influence of surface composition on hydrogen peroxide decomposition catalyzed by Co(II) aminopyridine-supported compounds on amorphous silica gel.

    PubMed

    de Farias, Robson F; Gonçalves, Afonso S; Airoldi, Claudio

    2002-03-01

    Cobalt compounds supported on 2-, 3-, and 4-aminopyridine-modified silica surfaces, named Sil2Co, Sil3Co, and Sil4Co, respectively, were used to catalyze the decomposition of hydrogen peroxide on ethanolic solutions at 293, 298, and 303 K. The calculated k values (x10(-4) s(-1)) for Sil2Co, Sil3Co, and Sil4Co are 0.65, 1.24, and 4.78 (293 K); 1.23, 1.87, and 6.33 (298 K); and 1.80, 2.80, and 10.30 (303 K), respectively. All obtained results evidence that such decomposition is a first-order reaction. Zinc-, nickel-, and copper-supported compounds were also tested, but exhibited a very low catalytic activity. By using the k values at 298 and 303 K, and employing the equation ln (k1/k2) = E(a)/R(1/T2-1/T1), the activation energy values for the considered reaction were Sil2Co = 57.20, Sil3Co = 60.60, and Sil4Co = 73.10 kJ mol(-1), respectively. The low values calculated for E(a) are in agreement with a free-radical mechanism.

  9. Atom transfer radical addition (ATRA) catalyzed by copper complexes with tris[2-(dimethylamino)ethyl]amine (Me6TREN) ligand in the presence of free-radical diazo initiator AIBN.

    PubMed

    Eckenhoff, William T; Pintauer, Tomislav

    2011-05-14

    In this article, we focus on the evaluation of tris[2-(dimethylamino)ethyl]amine (Me(6)TREN) ligand in copper catalyzed ATRA in the presence of free-radical diazo initiator AIBN (2,2'-azobis(2-methylpropionitrile)). The addition of carbon tetrachloride to 1-hexene, 1-octene and cis-cyclooctene proceeded efficiently to yield 89, 85 and 85% of monoadduct, respectively, using the catalyst to alkene ratio of 1 : 2500. For alkenes that readily undergo free radical polymerization, such as methyl acrylate, catalyst loadings as high as 0.4 mol-% were required. Furthermore, modest yields of the monoadduct were obtained with less active alkyl halides (chloroform and bromoform) using 250 : 1 and 500 : 1 ratios of alkene to copper(II). Interestingly, the addition of carbon tetrachloride to cis-cyclooctene produced only 1-chloro-4-(trichloromethyl)-cyclooctene, while carbon tetrabromide yielded 1,2 and 1,4-regioisomers in 75 : 25 ratio. The activity of [Cu(II)(Me(6)TREN)X][X] (X = Br(-) and Cl(-)) complexes in ATRA in the presence of AIBN was additionally probed by adding excess free ligand, source of halide anions and triphenylphosphine. The results indicated that disproportionation is a likely cause for lower activity of Me(6)TREN as compared to TPMA (tris(2-pyridylmethyl)amine).

  10. Cuprous Oxide Catalyzed Oxidative C-C Bond Cleavage for C-N Bond Formation: Synthesis of Cyclic Imides from Ketones and Amines.

    PubMed

    Wang, Min; Lu, Jianmin; Ma, Jiping; Zhang, Zhe; Wang, Feng

    2015-11-16

    Selective oxidative cleavage of a C-C bond offers a straightforward method to functionalize organic skeletons. Reported herein is the oxidative C-C bond cleavage of ketone for C-N bond formation over a cuprous oxide catalyst with molecular oxygen as the oxidant. A wide range of ketones and amines are converted into cyclic imides with moderate to excellent yields. In-depth studies show that both α-C-H and β-C-H bonds adjacent to the carbonyl groups are indispensable for the C-C bond cleavage. DFT calculations indicate the reaction is initiated with the oxidation of the α-C-H bond. Amines lower the activation energy of the C-C bond cleavage, and thus promote the reaction. New insight into the C-C bond cleavage mechanism is presented. PMID:26494312

  11. Palladium-Catalyzed C-H Arylation of α,β-Unsaturated Imines: Catalyst-Controlled Synthesis of Enamine and Allylic Amine Derivatives.

    PubMed

    Li, Minyan; González-Esguevillas, María; Berritt, Simon; Yang, Xiaodong; Bellomo, Ana; Walsh, Patrick J

    2016-02-18

    A unique chemo- and regioselective α- and γ-arylation of palladium azapentadienyl intermediates is presented. Two distinct catalysts and sets of conditions successfully controlled the regioselectivity of the arylation. These methods provide the first umpolung C-H functionalization of azapentadienyl palladium intermediates and enable the divergent synthesis of allylic amine and enamine derivatives, which are of significant interest in the pharmaceutical industry. PMID:26846375

  12. Towards the design of organocatalysts for nerve agents remediation: The case of the active hydrolysis of DCNP (a Tabun mimic) catalyzed by simple amine-containing derivatives.

    PubMed

    Barba-Bon, Andrea; Martínez-Máñez, Ramón; Sancenón, Félix; Costero, Ana M; Gil, Salvador; Pérez-Pla, Francisco; Llopis, Elisa

    2015-11-15

    We report herein a study of the hydrolysis of Tabun mimic DCNP in the presence of different amines, aminoalcohols and glycols as potential suitable organocatalysts for DCNP degradation. Experiments were performed in CD3CN in the presence of 5% D2O, which is a suitable solvent mixture to follow the DCNP hydrolysis. These studies allowed the definition of different DCNP depletion paths, resulting in the formation of diethylphosphoric acid, tetraethylpyrophosphate and phosphoramide species as final products. Without organocatalysts, DCNP hydrolysis occurred mainly via an autocatalysis path. Addition of tertiary amines in sub-stoichiometric amounts largely enhanced DCNP depletion whereas non-tertiary polyamines reacted even faster. Glycols induced very slight increment in the DCNP hydrolysis, whereas DCNP hydrolysis increased sharply in the presence of certain aminoalcohols especially, 2-(2-aminoethylamino)ethanol. For the latter compound, DCNP depletion occurred ca. 80-fold faster than in the absence of organocatalysts. The kinetic studies revealed that DCNP hydrolysis in the presence of 2-(2-aminoethylamino)ethanol occurred via a catalytic process, in which the aminoalcohol was involved. DCNP hydrolysis generally depended strongly on the structure of the amine, and it was found that the presence of the OHCH2CH2N moiety in the organocatalyst structure seems important to induce a fast degradation of DCNP.

  13. Towards the design of organocatalysts for nerve agents remediation: The case of the active hydrolysis of DCNP (a Tabun mimic) catalyzed by simple amine-containing derivatives.

    PubMed

    Barba-Bon, Andrea; Martínez-Máñez, Ramón; Sancenón, Félix; Costero, Ana M; Gil, Salvador; Pérez-Pla, Francisco; Llopis, Elisa

    2015-11-15

    We report herein a study of the hydrolysis of Tabun mimic DCNP in the presence of different amines, aminoalcohols and glycols as potential suitable organocatalysts for DCNP degradation. Experiments were performed in CD3CN in the presence of 5% D2O, which is a suitable solvent mixture to follow the DCNP hydrolysis. These studies allowed the definition of different DCNP depletion paths, resulting in the formation of diethylphosphoric acid, tetraethylpyrophosphate and phosphoramide species as final products. Without organocatalysts, DCNP hydrolysis occurred mainly via an autocatalysis path. Addition of tertiary amines in sub-stoichiometric amounts largely enhanced DCNP depletion whereas non-tertiary polyamines reacted even faster. Glycols induced very slight increment in the DCNP hydrolysis, whereas DCNP hydrolysis increased sharply in the presence of certain aminoalcohols especially, 2-(2-aminoethylamino)ethanol. For the latter compound, DCNP depletion occurred ca. 80-fold faster than in the absence of organocatalysts. The kinetic studies revealed that DCNP hydrolysis in the presence of 2-(2-aminoethylamino)ethanol occurred via a catalytic process, in which the aminoalcohol was involved. DCNP hydrolysis generally depended strongly on the structure of the amine, and it was found that the presence of the OHCH2CH2N moiety in the organocatalyst structure seems important to induce a fast degradation of DCNP. PMID:26005922

  14. Copper-TEMPO-catalyzed synthesis of α-ketoamides via tandem sp(3)C-H aerobic oxidation and amination of phenethyl alcohol derivatives.

    PubMed

    Liu, Chengkou; Yang, Zhao; Guo, Shiyu; Zeng, Yu; Zhu, Ning; Li, Xin; Fang, Zheng; Guo, Kai

    2016-09-28

    An efficient copper-TEMPO-catalyzed one-pot synthesis of α-ketoamides from phenethyl alcohol derivatives was developed firstly. Moreover, molecular oxygen in open air was employed as the oxidant with a broad substrate scope, which makes this methodology more practical. Based on some control experiments, a plausible mechanism was proposed. PMID:27548362

  15. Bi(OTf)3-Catalyzed One-Step Catalytic Synthesis of N-Boc or N-Cbz Protected α-Branched Amines.

    PubMed

    Jaratjaroonphong, Jaray; Tuengpanya, Surisa; Ruengsangtongkul, Sureeporn

    2015-01-01

    In this paper, N-Boc and N-Cbz protected α-branched amines are synthesized directly from commercially available aromatic/heteroaromatic compounds, aldehydes, and tert-butyl or benzyl carbamate bearing a variety of substituents. Bismuth(III) triflate is found to be a highly effective catalyst for this one-pot, three-component coupling reaction. In addition, the use of mild reaction conditions, low catalytic loading, easy removal of the N-protective group, and one-step synthesis under "open-flask" are advantages of the present procedure. PMID:25479369

  16. Amine Directed Pd(II)-Catalyzed C-H Activation-Intramolecular Amination of N-Het(aryl)/Acyl Enaminonitriles and Enaminones: An Approach towards Multisubstituted Indoles and Heterofused Pyrroles.

    PubMed

    Yugandar, Somaraju; Konda, Saidulu; Ila, Hiriyakkanavar

    2016-03-01

    An efficient route to multisubstituted indoles has been developed through intramolecular oxidative C-H activation-amination of readily available 2-(het)aryl-3-(het)aryl/alkyl-3-(het)aryl/acylaminoacrylonitrile/enaminone precursors in the presence of either palladium acetate/cupric acetate catalytic system under oxygen atmosphere or palladium acetate/silver carbonate in the presence of pivalic acid as additive. The method is compatible with a diverse range of substituents on the aryl ring as well as at the 2- and 3-positions of the indole ring. The versatility of this method was further demonstrated by elaborating it for the synthesis of heterofused pyrroles such as thieno[2,3-b]pyrroles, thieno[3,2-b]pyrroles, pyrrolo[2,3-b]indoles, and pyrrolo[2,3-b]pyridines in good yields. Probable mechanisms for the formation of these indoles have been suggested. PMID:26842134

  17. Cobalt-catalyzed oxidative isocyanide insertion to amine-based bisnucleophiles: diverse synthesis of substituted 2-aminobenzimidazoles, 2-aminobenzothiazoles, and 2-aminobenzoxazoles.

    PubMed

    Zhu, Tong-Hao; Wang, Shun-Yi; Wang, Gao-Nan; Ji, Shun-Jun

    2013-05-01

    Cobalt catalysis: Synthesis of substituted 2-aminobenzimidazoles, 2-aminobenzothiazoles, and 2-aminobenzoxazoles was achieved by using cobalt(II) acetate catalyzed isocyanide insertion to o-diaminobenzene, 2-aminobenzenethiol, and 2-aminophenol derivatives in 1,4-dioxane (see scheme). It was found that the reaction proceeded efficiently to give the desired products in up to 95 % isolated yields by C-N and C-S (O, N) formation in a single step.

  18. Insights into dehydrogenative coupling of alcohols and amines catalyzed by a (PNN)-Ru(II) hydride complex: unusual metal-ligand cooperation.

    PubMed

    Zeng, Guixiang; Li, Shuhua

    2011-11-01

    Density functional theory calculations were performed to elucidate the mechanism of dehydrogenative coupling of primary alcohols and amines mediated by a PNN-Ru(II) hydride complex (PNN = (2-(di-tert-butylphosphinomethyl)-6-(diethylaminomethyl)pyridine)). A plausible reaction pathway was proposed which contains three stages: (1) The alcohol dehydrogenation reaction to generate the aldehyde and H(2); (2) The aldehyde-amine condensation reaction to form the hemiaminal intermediate; (3) The dehydrogenation process of the hemiaminal intermediate to yield the final amide product with the liberation of H(2). The first and third stages occur via a similar pathway: (a) Proton transfer from the substrate to the PNN ligand; (b) Intramolecular rearrangement of the deprotonated substrate to form an anagostic complex; (c) Hydride transfer from the deprotonated substrate to the Ru center to yield the trans-dihydride intermediate and the aldehyde (or amide); (d) Benzylic proton migration from the PNN ligand to the metal center forming a dihydrogen complex and subsequent H(2) liberation to regenerate the catalyst. In all these steps, the metal-ligand cooperation plays an essential role. In proton transfer steps (a) and (d), the metal-ligand cooperation is achieved through the aromatization/dearomatization processes of the PNN ligand. While in steps (b) and (c), their collaboration are demonstrated by the formation of an anagostic interaction between Ru and the C-H bond and two ionic hydrogen bonds supported by the PNN ligand. PMID:21942421

  19. Palladium-Catalyzed Coupling of Functionalized Primary and Secondary Amines with Aryl and Heteroaryl Halides: Two Ligands Suffice in Most Cases†

    PubMed Central

    Maiti, Debabrata; Fors, Brett P.; Henderson, Jaclyn L.; Nakamura, Yoshinori; Buchwald, Stephen L.

    2012-01-01

    We report our studies on the use of two catalyst systems, based on the ligands BrettPhos (1) and RuPhos (2), which provide the widest scope for Pd-catalyzed C–N cross-coupling reactions to date. Often low catalyst loadings and short reaction times can be used with functionalized aryl and heteroaryl coupling partners. The reactions are highly robust and can be set up and performed without the use of a glovebox. These catalysts should find wide application in the synthesis of complex molecules including pharmaceuticals, natural products and functional materials. PMID:22384311

  20. Ruthenium-catalyzed alkylation of indoles with tertiary amines by oxidation of a sp3 C-H bond and Lewis acid catalysis.

    PubMed

    Wang, Ming-Zhong; Zhou, Cong-Ying; Wong, Man-Kin; Che, Chi-Ming

    2010-05-17

    Ruthenium porphyrins (particularly [Ru(2,6-Cl(2)tpp)CO]; tpp=tetraphenylporphinato) and RuCl(3) can act as oxidation and/or Lewis acid catalysts for direct C-3 alkylation of indoles, giving the desired products in high yields (up to 82% based on 60-95% substrate conversions). These ruthenium compounds catalyze oxidative coupling reactions of a wide variety of anilines and indoles bearing electron-withdrawing or electron-donating substituents with high regioselectivity when using tBuOOH as an oxidant, resulting in the alkylation of N-arylindoles to 3-{[(N-aryl-N-alkyl)amino]methyl}indoles (yield: up to 82%, conversion: up to 95%) and the alkylation of N-alkyl or N-H indoles to 3-[p-(dialkylamino)benzyl]indoles (yield: up to 73%, conversion: up to 92%). A tentative reaction mechanism involving two pathways is proposed: an iminium ion intermediate may be generated by oxidation of an sp(3) C-H bond of the alkylated aniline by an oxoruthenium species; this iminium ion could then either be trapped by an N-arylindole (pathway A) or converted to formaldehyde, allowing a subsequent three-component coupling reaction of the in situ generated formaldehyde with an N-alkylindole and an aniline in the presence of a Lewis acid catalyst (pathway B). The results of deuterium-labeling experiments are consistent with the alkylation of N-alkylindoles via pathway B. The relative reaction rates of [Ru(2,6-Cl(2)tpp)CO]-catalyzed oxidative coupling reactions of 4-X-substituted N,N-dimethylanilines with N-phenylindole (using tBuOOH as oxidant), determined through competition experiments, correlate linearly with the substituent constants sigma (R(2)=0.989), giving a rho value of -1.09. This rho value and the magnitudes of the intra- and intermolecular deuterium isotope effects (k(H)/k(D)) suggest that electron transfer most likely occurs during the initial stage of the oxidation of 4-X-substituted N,N-dimethylanilines. Ruthenium-catalyzed three-component reaction of N-alkyl/N-H indoles

  1. Oxidant-free conversion of primary amines to nitriles.

    PubMed

    Tseng, Kuei-Nin T; Rizzi, Andrew M; Szymczak, Nathaniel K

    2013-11-01

    An amide-derived NNN-Ru(II) hydride complex catalyzes oxidant-free, acceptorless, and chemoselective dehydrogenation of primary and secondary amines to the corresponding nitriles and imines with liberation of dihydrogen. The catalyst system tolerates oxidizable functionality and is selective for the dehydrogenation of primary amines (-CH2NH2) in the presence of amines without α-CH hydrogens. PMID:24144014

  2. Gold(I)-Catalyzed N-Desulfonylative Amination versus N-to-O 1,5-Sulfonyl Migration: A Versatile Approach to 1-Azabicycloalkanes.

    PubMed

    Miaskiewicz, Solène; Gaillard, Boris; Kern, Nicolas; Weibel, Jean-Marc; Pale, Patrick; Blanc, Aurélien

    2016-07-25

    Valuable 1-azabicycloalkane derivatives have been synthesized through a novel gold(I)-catalyzed desulfonylative cyclization strategy. An ammoniumation reaction of ynones substituted at the 1-position with an N-sulfonyl azacycle took place in the presence of a gold cation by intramolecular cyclization of the disubstituted sulfonamide moiety onto the triple bond. Depending on the size of the heterocyclic ring and substitution of the substrates, two unprecedented forms of nucleophilic attack on the sulfonyl group were exploited, that is, a N-desulfonylation in the presence of an external protic O nucleophile (37-87 %, 10 examples) and a unique N-to-O 1,5-sulfonyl migration (60-98 %, 9 examples). PMID:27309374

  3. Mesoporous Silica with Site-Isolated Amine and Phosphotungstic Acid Groups: A Solid Catalyst with Tunable Antagonistic Functions for One-Pot Tandem Reactions

    SciTech Connect

    Shiju N. R.; Syed K.; Alberts A.; Brown D. and Rothenberg G.

    2011-09-15

    A bifunctional solid catalyst is prepared by combining acid and base functions on mesoporous silica supports. The co-existence of these functions is shown by a two-step reaction sequence in one pot. Excellent product yields, which cannot be obtained by separated acid and base functions in one pot, show the validity of our concept.

  4. Synthesis of antireflective silica coatings through the synergy of polypeptide layer-by-layer assemblies and biomineralization

    NASA Astrophysics Data System (ADS)

    Lee, Yung-Lun; Lin, Ting-Xuan; Hsu, Feng-Ming; Jan, Jeng-Shiung

    2016-01-01

    We report a versatile approach to synthesize silica coatings with antireflective (AR) characteristics through the combination of a layer-by-layer (LbL) assembly technique and biomineralization. LbL assembled decanoyl-modified poly(l-lysine)/poly(l-glutamic acid) (PLL-g-Dec/PLGA) multilayer films were used as templates for silica mineralization, followed by calcination. The specific deposition of silica onto the LbL polypeptide assemblies through amine-catalyzed polycondensation resulted in silica coatings that exhibited the transcription of the nano-/microstructured polypeptide films and their film thickness and porosity can be tuned by varying the number of bilayers, degree of substitution, and PLL molecular weight. AR silica coatings exhibiting more than 6% increase in transmittance in the near UV/visible spectral range can be obtained at an optimized refractive index, thickness, and surface roughness. The abrasion test showed that the silica coatings exhibited sufficient structural durability due to continuous silica nanostructures and low surface roughness. This study demonstrated that nanostructured thin films can be synthesized for AR coatings using the synergy between the LbL assembly technique and biomineralization.We report a versatile approach to synthesize silica coatings with antireflective (AR) characteristics through the combination of a layer-by-layer (LbL) assembly technique and biomineralization. LbL assembled decanoyl-modified poly(l-lysine)/poly(l-glutamic acid) (PLL-g-Dec/PLGA) multilayer films were used as templates for silica mineralization, followed by calcination. The specific deposition of silica onto the LbL polypeptide assemblies through amine-catalyzed polycondensation resulted in silica coatings that exhibited the transcription of the nano-/microstructured polypeptide films and their film thickness and porosity can be tuned by varying the number of bilayers, degree of substitution, and PLL molecular weight. AR silica coatings exhibiting

  5. [Stardust Amines

    NASA Technical Reports Server (NTRS)

    Dworkin, Jason P.

    2008-01-01

    We investigated the abundances of amino acids and amines, as well as their enantiomeric composition in water extracts of comet Wild 2 exposed aerogel and aluminum foils returned by Stardust using liquid chromatography with UV fluorescence detection and time of flight-mass spectrometry (LC-FD/ToF-MS). A suite of amino acids and amines including glycine, L-alanine, methylamine (MA), and ethylamine (EA) were identified in the Stardust bulk aerogel. With the exception of MA and EA, all other primary amines detected in comet-exposed aerogels were also present in the aerogel witness tile that was not exposed to Wild 2, suggesting that most amines are terrestrial in origin. The enhanced abundances of MA, EA, and possibly glycine in comet-exposed aerogel compared to controls, coupled with MA to EA ratios (approx.1 to 2) that are distinct from preflight aerogels (approx.7 to lo), suggest that these amines were captured from Wild 2. The presence of cometary amines in Stardust material supports the hypothesis that comets were an important source of prebiotic organics on the early Earth. To better understand their origin, a systematic study of all these species with C, N, and H compound specific isotopic analysis (CSIA) via gas chromatography quadrupole mass spectrometry in with parallel with combustion isotope ratio mass spectrometry (GC-QMS/IRMS) is being conducted. We will discuss our latest C-CSIA measurements and what they indicate about the origin of the amino acids extracted from Stardust samples.

  6. Amine-Promoted Organosilicate Hydrolysis Mechanism at Near-Neutral pH

    NASA Astrophysics Data System (ADS)

    Delak, K. M.; Sahai, N.

    2006-12-01

    Proteins bearing polylysine moeities and histidine and serine amino-aicd residues, isolated from diatoms and sponges, are known to promote biological nanoporous silica formation [1, 2]. Using 29Si NMR, we have shown quantitatively that monoamines and small polyamines can chemically accelerate the hydrolysis and condensation rates of organosilicate starting materials, in biomimetic silica synthesis pathways, at circum- neutral pHs and room temperature [3, 4]. The present study is focused on understanding the mechanistic role of these amines in catalyzing the hydrolysis step that precedes condensation [5]. We conducted 29Si NMR experimental studies over a range of temperature and pHs for the hydrolysis rates of trimethylethoxysilane (TMES), a model compound with only one hydrolyzable bond. Experimental results were combined with quantum mechanical hybrid Density Functional Theory calculations of putative intermediate and transition state structures for TMES and tetramethylorthosilicate (TMOS) which has four hydrolyzable bonds. Comparison of calculated energies with experimentally-determined activation energies indicated that amines promote TMES hydrolysis mainly due to the amine's acidity at neutral pH. The proton released by the amine is transferred to the organosilicate, producing a protonated, ethoxy leaving group that can be displaced by water in an SN2 reaction. For TMOS, the activation energy of proton-transfer coupled with SN2 substitution is comparable to that for Corriu's nucleophile-activated nucleophilic displacement mechanism [6], such that the mechanism of amine-catalyzed hydrolysis is mostly dependent on the ambient pH conditions as well as the type of amine. The molecular mechanisms of hydrolysis and aggregation are reflected, ultimately, on the larger scale in the silica morphology where amines promoting faster hydrolysis result in glassy products compared to slower hydrolyzing amines forming particulate silica [7, 8]. REFERENCES [1] Kroger N

  7. Solid-phase extraction of copper(II) in water and food samples using silica gel modified with bis(3-aminopropyl)amine and determination by flame atomic absorption spectrometry.

    PubMed

    Cagirdi, Duygu; Altundag, Hüseyin; Imamoglu, Mustafa; Tuzen, Mustafa

    2014-01-01

    A simple and selective separation and preconcentration method was developed for the determination of Cu(ll) ions. This method is based on adsorption of Cu(ll) ions from aqueous solution on a bis(3-aminopropyl)amine modified silica gel column and flame atomic absorption spectrometric determination after desorption. Various analytical parameters such as pH, type of eluent solution and its volume, flow rate of sample and eluent, and sample volume were optimized. Effects of some cation, anion, and transition metal ions on the recoveries of Cu(ll) ions were also investigated. Cu(ll) ions were quantitatively recovered at pH 6; 5.0 mL of 2 M HCI was used as the eluent. The preconcentration factor was found to be 150. The LOD was 0.12 microg/L for Cu(ll). The accuracy of the method was confirmed by analysis of Tea Leaves (INCT-TL-1) and Fish Protein (DORM-3) certified reference materials. The optimized method was applied to various water and food samples for the determination of Cu(ll). PMID:25145149

  8. Formal Direct Cross-Coupling of Phenols with Amines.

    PubMed

    Chen, Zhengwang; Zeng, Huiying; Girard, Simon A; Wang, Feng; Chen, Ning; Li, Chao-Jun

    2015-11-23

    The transition-metal-catalyzed amination of aryl halides has been the most powerful method for the formation of aryl amines over the past decades. Phenols are regarded as ideal alternatives to aryl halides as coupling partners in cross-couplings. An efficient palladium-catalyzed formal cross-coupling of phenols with various amines and anilines has now been developed. A variety of substituted phenols were compatible with the standard reaction conditions. Secondary and tertiary aryl amines could thus be synthesized in moderate to excellent yields. PMID:26531683

  9. Rh-catalyzed borylation of N-adjacent C(sp3)-H bonds with a silica-supported triarylphosphine ligand.

    PubMed

    Kawamorita, Soichiro; Miyazaki, Tatsuya; Iwai, Tomohiro; Ohmiya, Hirohisa; Sawamura, Masaya

    2012-08-01

    Direct C(sp(3))-H borylation of amides, ureas, and 2-aminopyridine derivatives at the position α to the N atom, which gives the corresponding α-aminoalkylboronates, has been achieved with a heterogeneous catalyst system consisting of [Rh(OMe)(cod)]2 and a silica-supported triarylphosphine ligand (Silica-TRIP) that features an immobilized triptycene-type cage structure with a bridgehead P atom. The reaction occurs not only at terminal C-H bonds but also at internal secondary C-H bonds under mild reaction conditions (25-100 °C, 0.1-0.5 mol % Rh). PMID:22816772

  10. Role of amine structure on carbon dioxide adsorption from ultradilute gas streams such as ambient air.

    PubMed

    Didas, Stephanie A; Kulkarni, Ambarish R; Sholl, David S; Jones, Christopher W

    2012-10-01

    A fundamental study on the adsorption properties of primary, secondary, and tertiary amine materials is used to evaluate what amine type(s) are best suited for ultradilute CO(2) capture applications. A series of comparable materials comprised of primary, secondary, or tertiary amines ligated to a mesoporous silica support via a propyl linker are used to systematically assess the role of amine type. Both CO(2) and water adsorption isotherms are presented for these materials in the range relevant to CO(2) capture from ambient air and it is demonstrated that primary amines are the best candidates for CO(2) capture from air. Primary amines possess both the highest amine efficiency for CO(2) adsorption as well as enhanced water affinity compared to other amine types or the bare silica support. The results suggest that the rational design of amine adsorbents for the extraction of CO(2) from ambient air should focus on adsorbents rich in primary amines.

  11. Quinoline-2-carboimine copper complex immobilized on amine functionalized silica coated magnetite nanoparticles: a novel and magnetically retrievable catalyst for the synthesis of carbamates via C-H activation of formamides.

    PubMed

    Sharma, R K; Dutta, Sriparna; Sharma, Shivani

    2015-01-21

    In the present study, we report the synthesis of a highly efficient and magnetically retrievable catalytic system (Cu-2QC@Am-SiO2@Fe3O4) through the covalent immobilization of quinoline-2-carboxaldehyde (2QC) on an amine functionalized silica coated ferrite nanosupport followed by metallation with copper acetate. The structure of the organic-inorganic hybrid nanomaterial has been confirmed using various physicochemical techniques such as Powder X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-Ray Spectroscopy (EDS), Energy Dispersive X-Ray Fluorescence Spectroscopy (ED-XRF), Atomic Absorption Spectroscopy (AAS), Inductively Coupled Plasma Spectroscopy (ICP) and Vibrating Sample Magnetometry (VSM). The resulting nanocatalyst exhibits a remarkable catalytic efficacy in the synthesis of industrially and pharmaceutically significant carbamates via the C-H activation of formamides under solvent free conditions. The most important attribute of the present methodology is that the catalyst can be recovered simply through an external magnetic force and reused several times without any significant deterioration in its activity. Furthermore, the heterogeneity test has been carried out in order to ensure the intrinsic stability of the nanostructured catalyst. The activity of the Cu-2QC@Am-SiO2@Fe3O4 nanocatalyst has been found to be far more superior in comparison with the literature precedents in terms of the product yield, cost and reusability of the catalyst. Besides, ambient reaction conditions, simple workup procedure, wide substrate scope and cost effectiveness are some of the other outstanding features of this protocol that make it economical and sustainable. PMID:25417959

  12. Quinoline-2-carboimine copper complex immobilized on amine functionalized silica coated magnetite nanoparticles: a novel and magnetically retrievable catalyst for the synthesis of carbamates via C-H activation of formamides.

    PubMed

    Sharma, R K; Dutta, Sriparna; Sharma, Shivani

    2015-01-21

    In the present study, we report the synthesis of a highly efficient and magnetically retrievable catalytic system (Cu-2QC@Am-SiO2@Fe3O4) through the covalent immobilization of quinoline-2-carboxaldehyde (2QC) on an amine functionalized silica coated ferrite nanosupport followed by metallation with copper acetate. The structure of the organic-inorganic hybrid nanomaterial has been confirmed using various physicochemical techniques such as Powder X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-Ray Spectroscopy (EDS), Energy Dispersive X-Ray Fluorescence Spectroscopy (ED-XRF), Atomic Absorption Spectroscopy (AAS), Inductively Coupled Plasma Spectroscopy (ICP) and Vibrating Sample Magnetometry (VSM). The resulting nanocatalyst exhibits a remarkable catalytic efficacy in the synthesis of industrially and pharmaceutically significant carbamates via the C-H activation of formamides under solvent free conditions. The most important attribute of the present methodology is that the catalyst can be recovered simply through an external magnetic force and reused several times without any significant deterioration in its activity. Furthermore, the heterogeneity test has been carried out in order to ensure the intrinsic stability of the nanostructured catalyst. The activity of the Cu-2QC@Am-SiO2@Fe3O4 nanocatalyst has been found to be far more superior in comparison with the literature precedents in terms of the product yield, cost and reusability of the catalyst. Besides, ambient reaction conditions, simple workup procedure, wide substrate scope and cost effectiveness are some of the other outstanding features of this protocol that make it economical and sustainable.

  13. Three-component synthesis of polysubstituted pyrroles from α-diazoketones, nitroalkenes, and amines.

    PubMed

    Hong, Deng; Zhu, Yuanxun; Li, Yao; Lin, Xufeng; Lu, Ping; Wang, Yanguang

    2011-09-01

    Polysubstituted pyrroles are regiospecifically synthesized via the copper-catalyzed three-component reaction of α-diazoketones, nitroalkenes, and amines under aerobic conditions. The cascade process involves an N-H insertion of carbene, a copper-catalyzed oxidative dehydrogenation of amine, and a [3 + 2] cycloaddition of azomethine ylide. PMID:21830767

  14. Copper-catalyzed three- five- or seven-component coupling reactions: the selective synthesis of cyanomethylamines, N,N-bis(cyanomethyl)amines and N,N'-bis(cyanomethyl)methylenediamines based on a Strecker-type synthesis.

    PubMed

    Sakai, Norio; Takahashi, Nobuaki; Inoda, Daiki; Ikeda, Reiko; Konakahara, Takeo

    2013-10-10

    We have demonstrated that a cooperative catalytic system comprised of CuCl and Cu(OTf)(2) could be used to effectively catalyse the three-, five- and seven-component coupling reactions of aliphatic or aromatic amines, formaldehyde, and trimethylsilyl cyanide (TMSCN), and selectively produce in good yields the corresponding cyanomethylamines, N,N-bis(cyanomethyl)amines and N,N'-bis(cyanomethyl)methylenediamines.

  15. Phenylethynyl amine

    NASA Technical Reports Server (NTRS)

    Hergenrother, Paul M. (Inventor); Bryant, Robert G. (Inventor); Jensen, Brian J. (Inventor); Havens, Stephen J. (Inventor)

    1997-01-01

    Four phenylethynyl amine compounds--3 and 4-aminophenoxy-4'-phenylethynylbenzophenone, and 3 and 4-amino-4'-phenylethynylbenzophenone--were readily prepared and were used to endcap imide oligomers. Phenylethynyl-terminated amide acid oligomers and phenylethynyl-terminated imide oligomers with various molecular weights and compositions were prepared and characterized. These oligomers were cured at 300.degree. C. to 400.degree. C. to provide crosslinked polyimides with excellent solvent resistance, high strength and modulus and good high temperature properties. Adhesive panels, composites, films and moldings from these phenylethynyl terminated imide oligomers gave excellent mechanical performance.

  16. Gadolinium-doped silica nanoparticles encapsulating indocyanine green for near infrared and magnetic resonance imaging.

    PubMed

    Sharma, Parvesh; Bengtsson, Niclas E; Walter, Glenn A; Sohn, Han-Byul; Zhou, Guangyin; Iwakuma, Nobutaka; Zeng, Huadong; Grobmyer, Stephen R; Scott, Edward W; Moudgil, Brij M

    2012-09-24

    Clinical applications of the indocyanine green (ICG) dye, the only near infrared (NIR) imaging dye approved by the Food and Drug Administration (FDA) in the USA, are limited due to rapid protein binding, fast clearance, and instability in physiologically relevant conditions. Encapsulating ICG in silica particles can enhance its photostability, minimize photobleaching, increase the signal-to-noise (S/N) ratio and enable in vivo studies. Furthermore, a combined magnetic resonance (MR) and NIR imaging particulate can integrate the advantage of high-resolution 3D anatomical imaging with high-sensitivity deep-tissue in-vivo fluorescent imaging. In this report, a novel synthesis technique that can achieve these goals is presented. A reverse-microemulsion-based synthesis protocol is employed to produce 25 nm ICG-doped silica nanoparticles (NPs). The encapsulation of ICG is achieved by manipulating coulombic attractions with bivalent ions and aminated silanes and carrying out silica synthesis in salt-catalyzed, mildly basic pH conditions using dioctyl sulfosuccinate (AOT)/heptane/water microemulsion system. Furthermore, paramagnetic properties are imparted by chelating paramagnetic Gd to the ICG-doped silica NPs. Aqueous ICG-dye-doped silica NPs show increased photostability (over a week) and minimal photobleaching as compared to the dye alone. The MR and optical imaging capabilities of these particles are demonstrated through phantom, in vitro and in vivo experiments. The described particles have the potential to act as theranostic agents by combining photodynamic therapy through the absorption of NIR irradiated light.

  17. The sugar model: catalysis by amines and amino acid products

    NASA Technical Reports Server (NTRS)

    Weber, A. L.

    2001-01-01

    Ammonia and amines (including amino acids) were shown to catalyze the formation of sugars from formaldehyde and glycolaldehyde, and the subsequent conversion of sugars to carbonylcontaining products under the conditions studied (pH 5.5 and 50 degrees C). Sterically unhindered primary amines were better catalysts than ammonia, secondary amines, and sterically hindered primary amines (i.e. alpha-aminoisobutyric acid). Reactions catalyzed by primary amines initially consumed formaldehyde and glycolaldehyde about 15-20 times faster than an uncatalyzed control reaction. The amine-catalyzed reactions yielded aldotriose (glyceraldehyde), ketotriose (dihydroxyacetone), aldotetroses (erythrose and threose), ketotetrose (erythrulose), pyruvaldehyde, acetaldehyde, glyoxal, pyruvate, glyoxylate, and several unindentified carbonyl products. The concentrations of the carbonyl products, except pyruvate and ketotetrose, initially increased and then declined during the reaction, indicating their ultimate conversion to other products (like larger sugars or pyruvate). The uncatalyzed control reaction yielded no pyruvate or glyoxylate, and only trace amounts of pyruvaldehyde, acetaldehyde and glyoxal. In the presence of 15 mM catalytic primary amine, such as alanine, the rates of triose and pyruvaldehyde of synthesis were about 15-times and 1200-times faster, respectively, than the uncatalyzed reaction. Since previous studies established that alanine is synthesized from glycolaldehyde and formaldehyde via pyruvaldehyde as its direct precursor, the demonstration that the alanine catalyzes the conversion of glycolaldehyde and formaldehyde to pyruvaldehyde indicates that this synthetic pathway is capable of autocatalysis. The relevance of this synthetic process, named the Sugar Model, to the origin of life is discussed.

  18. Exploring Silica Chemistry at Biological Interfaces: Kinetic and Thermodynamic Drivers of Surface Nucleation

    NASA Astrophysics Data System (ADS)

    Wallace, A. F.; Dove, P. M.

    2006-12-01

    Biochemical investigations have begun to yield information about structural and chemical properties of organic macromolecules involved in biosilicification processes. However, the mechanisms by which these molecules mediate biosilica formation remain unclear. The formation of mineralized structures in organisms is rooted in processes taking place at the nanoscale, and therefore, molecular level investigative probes are required. Insights into how mineral formation occurs within living organisms can be gained by conducting experimental studies with simple model systems that emulate key features of biological systems. Our approach utilizes a novel AFM-based approach to measure the dependence of amorphous silica nucleation kinetics on the chemical and structural nature of the underlying substrate. Model biological surfaces terminated with carboxyl, hydroxyl, and amine moieties were generated through the spontaneous adsorption of {ω}-alkanethiol self-assembled monolayers onto ultra-flat (111) surfaces of gold. Silica nucleation experiments used supersaturated solutions of silicic acid that were produced by the acid catalyzed hydrolysis of tetramethyl orthosilicate. Measurements of surface nucleation rate were conducted under conditions that simulate current views of conditions within silica deposition vesicles of major diatom species, (e.g. ambient temperature, pH = 5.0, NaCl = 0.1 mol/kg). Aqueous silicate levels were varied to examine dependencies on saturation state. Analysis of the kinetic data within the framework of nucleation theory quantifies the height of the kinetic barrier to silica formation, and the net energy of silica-substrate solution interfaces. By conducting experiments for COOH, NH3+, and OH-functionalized substrates, we determine the kinetic and thermodynamic controls of functional chemistry on heterogeneous nucleation of amorphous silica. The findings are providing new insights into how biochemical interfaces mediate the onset of silica formation.

  19. Photocatalytic splitting of CS2 to S8 and a carbon-sulfur polymer catalyzed by a bimetallic ruthenium(II) compound with a tertiary amine binding site: toward photocatalytic splitting of CO2?

    PubMed

    Livanov, Konstantin; Madhu, Vedichi; Balaraman, Ekambaram; Shimon, Linda J W; Diskin-Posner, Yael; Neumann, Ronny

    2011-11-21

    The catalytic photocleavage of CS(2) to S(8) and a (C(x)S(y))(n) polymer with visible light using a dinuclear ruthenium(II) compound with a bipyridine units for photoactivity and a vicinal tertiary amine binding site for CS(2) activation was studied. The catalyst was characterized by X-ray diffraction, (1)H NMR, and (13)C NMR, ESI-MS and elemental analysis. CS(2) photocleavage was significant (240 turnovers, 20 h) to yield isolable S(8) and a (C(x)S(y))(n) polymer. A mononuclear catalyst or one without an amine binding site showed significantly less activity. XPS of the (C(x)S(y))(n) polymer showed a carbon/sulfur ratio ∼1.5-1.6 indicating that in part both C-S bonds of CS(2) had been cleaved. Catalyst was also included within the polymer. The absence of peaks in the (1)H NMR verified the (C(x)S(y))(n) nature of the polymer, while (13)C NMR and IR indicated that the polymer had multiple types of C-S and C-C bonds.

  20. Dual C–H Functionalization of N-Aryl Amines: Synthesis of Polycyclic Amines via an Oxidative Povarov Approach

    PubMed Central

    2015-01-01

    Iminium ions generated in situ via copper(I) bromide catalyzed oxidation of N-aryl amines readily undergo [4 + 2] cycloadditions with a range of dienophiles. This method involves the functionalization of both a C(sp3)–H and a C(sp2)–H bond and enables the rapid construction of polycyclic amines under relatively mild conditions. PMID:24786302

  1. Polymer-silica hybrids for separation of CO2 and catalysis of organic reactions

    NASA Astrophysics Data System (ADS)

    Silva Mojica, Ernesto

    Porous materials comprising polymeric and inorganic segments have attracted interest from the scientific community due to their unique properties and functionalities. The physical and chemical characteristics of these materials can be effectively exploited for adsorption applications. This dissertation covers the experimental techniques for fabrication of poly(vinyl alcohol) (PVA) and silica (SiO2) porous supports, and their functionalization with polyamines for developing adsorbents with potential applications in separation of CO2 and catalysis of organic reactions. The supports were synthesized by processes involving (i) covalent cross-linking of PVA, (ii) hydrolysis and poly-condensation of silica precursors (i,e,. sol-gel synthesis), and formation of porous structures via (iii) direct templating and (iv) phase inversion techniques. Their physical structure was controlled by the proper combination of the preparation procedures, which resulted in micro-structured porous materials in the form of micro-particles, membranes, and pellets. Their adsorption characteristics were tailored by functionalization with polyethyleneimine (PEI), and their physicochemical properties were characterized by vibrational spectroscopy (FTIR, UV-vis), microscopy (SEM), calorimetry (TGA, DSC), and adsorption techniques (BET, step-switch adsorption). Spectroscopic investigations of the interfacial cross-linking reactions of PEI and PVA with glutaraldehyde (GA) revealed that PEI catalyzes the cross-linking reactions of PVA in absence of external acid catalysts. In-situ IR spectroscopy coupled with a focal plane array (FPA) image detector allowed the characterization of a gradient interface on a PEI/PVA composite membrane and the investigation of the cross-linking reactions as a function of time and position. The results served as a basis to postulate possible intermediates, and propose the reaction mechanisms. The formulation of amine-functionalized CO2 capture sorbents was based on the

  2. Synthesis of IAN-type N,N-Ligands via Dynamic Kinetic Asymmetric Buchwald-Hartwig Amination.

    PubMed

    Ramírez-López, Pedro; Ros, Abel; Romero-Arenas, Antonio; Iglesias-Sigüenza, Javier; Fernández, Rosario; Lassaletta, José M

    2016-09-21

    The Pd(0)-catalyzed coupling of racemic heterobiaryl bromides, triflates, or nonaflates with aryl/alkyl primary amines using QUINAP as the ligand provides the corresponding axially chiral heterobiaryl amines with excellent yields and enantioselectivities. Reactivity and structural studies of neutral and cationic oxidative addition intermediates support a dynamic kinetic asymmetric amination mechanism based on the labilization of the stereogenic axis in the latter and suggest that coordination of the amine to the Pd center is the stereodetermining step. PMID:27595166

  3. Tandem bis-aza-Michael addition reaction of amines in aqueous medium promoted by polystyrenesulfonic Acid

    EPA Science Inventory

    An efficient and environmentally benign tandem bis-aza-Michael addition of amines catalyzed by polystyrene sulfonic acid (PSSA) is described. This operationally simple high yielding microwave assisted synthetic protocol proceeded in water in the absence of any organic solvent.

  4. Catalytic Asymmetric Hydroamination of Unactivated Internal Olefins to Aliphatic Amines

    PubMed Central

    Yang, Yang; Shi, Shi-Liang; Niu, Dawen; Liu, Peng; Buchwald, Stephen L.

    2015-01-01

    Catalytic assembly of enantiopure aliphatic amines from abundant and readily available precursors has long been recognized as a paramount challenge in synthetic chemistry. Herein, we describe a mild and general copper-catalyzed hydroamination that effectively converts unactivated internal olefins, an important yet unexploited class of abundant feedstock chemicals, into highly enantioenriched α-branched amines (≥ 96% enantiomeric excess) featuring two minimally differentiated aliphatic substituents. This method provides a powerful means to access a broad range of advanced, highly functionalized enantioenriched amines of interest in pharmaceutical research and other areas. PMID:26138973

  5. A Metal and Base-Free Chemoselective Primary Amination of Boronic Acids Using Cyanamidyl/Arylcyanamidyl Radical as Aminating Species: Synthesis and Mechanistic Studies by Density Functional Theory.

    PubMed

    Chatterjee, Nachiketa; Arfeen, Minhajul; Bharatam, Prasad V; Goswami, Avijit

    2016-06-17

    An efficient, metal and base-free, chemoselective synthesis of aryl-, heteroaryl-, and alkyl primary amines from the corresponding boronic acids has been achieved at ambient temperature mediated by [bis(trifluoroacetoxy)iodo]benzene (PIFA) and N-bromosuccinimide (NBS) using cyanamidyl/arylcyanamidyl radicals as the aminating species. The primary amine compounds were initially obtained as their corresponding ammonium trifluoroacetate salts which, on treatment with aq NaOH, provide the free amines. Finally, the primary amines were isolated through column chromatography over silica-gel using hexane-EtOAc solvent system as the eluent. The reactions are sufficiently fast, completing within 1 h. Quantum chemical calculations in combination with experimental observations validate that the ipso amination of substituted boronic acids involves the formation of cyanamidyl/arylcyanamidyl radical, followed by regiospecific interaction of its nitrile-N center with boron atom of the boronic acids, leading to chemoselective primary amination.

  6. Enantioselective Synthesis of Homoallylic Amines through Reactions of (Pinacolato)allylborons with Aryl-, Heteroaryl-, Alkyl- or Alkene-Substituted Aldimines Catalyzed by Chiral C1-Symmetric NHC–Cu Complexes

    PubMed Central

    Vieira, Erika M.; Snapper, Marc L.; Hoveyda, Amir H.

    2011-01-01

    A catalytic method for enantioselective synthesis of homoallylamides through Cu-catalyzed reactions of stable and easily accessible (pinacolato)allylborons with aryl-, heteroaryl-,alkyl- or alkenyl-substituted N-phosphinoylimines is disclosed. Transformations are promoted by 1–5 mol % of readily accessible NHC–Cu complexes, derived from C1-symmetric imidazolinium salts, which can be prepared in multi-gram quantities in four steps from commercially available materials. Allyl additions deliver the desired products in up to quantitative yield and 98.5:1.5 enantiomeric ratio and are amenable to gram-scale operations. A mechanistic model accounting for the observed selectivity levels and trends is proposed. PMID:21341657

  7. One-pot Sequential Reactions Featuring a Copper-catalyzed Amination Leading to Pyrido[2',1':2,3]imidazo[4,5-c]quinolines and Dihydropyrido[2',1':2,3]imidazo[4,5-c]quinolines.

    PubMed

    Fan, Xue-Sen; Zhang, Ju; Li, Bin; Zhang, Xin-Ying

    2015-06-01

    Tetracyclic skeletons combining an imidazo[1,2-a]pyridine moiety with a quinoline framework such as pyrido[2',1':2,3]imidazo[4,5-b]quinoline are stimulating increasing interests since they are close isosteres of a series of powerful antiproliferative compounds. In this paper, we report a novel methodology for the synthesis of pyrido[2',1':2,3]imidazo[4,5-c]quinolines through one-pot sequential reactions of commercially available or readily obtainable 2-aminopyridines, 2-bromophenacyl bromides, aqueous ammonia, and aldehydes. Moreover, dihydropyrido[2',1':2,3]imidazo[4,5-c]quinolines could also be obtained in a similar manner by using various ketones as the substrates in place of aldehydes. Notably, the whole procedure combines condensation/amination/cyclization reactions in one pot to give complex compounds in a simple and practical manner. Compared with literature methods, the synthetic strategy reported herein has the advantages of readily available starting materials, structural diversity of products, good functional group tolerance, and obviation of step-by-step operations. PMID:25865134

  8. One-pot Sequential Reactions Featuring a Copper-catalyzed Amination Leading to Pyrido[2',1':2,3]imidazo[4,5-c]quinolines and Dihydropyrido[2',1':2,3]imidazo[4,5-c]quinolines.

    PubMed

    Fan, Xue-Sen; Zhang, Ju; Li, Bin; Zhang, Xin-Ying

    2015-06-01

    Tetracyclic skeletons combining an imidazo[1,2-a]pyridine moiety with a quinoline framework such as pyrido[2',1':2,3]imidazo[4,5-b]quinoline are stimulating increasing interests since they are close isosteres of a series of powerful antiproliferative compounds. In this paper, we report a novel methodology for the synthesis of pyrido[2',1':2,3]imidazo[4,5-c]quinolines through one-pot sequential reactions of commercially available or readily obtainable 2-aminopyridines, 2-bromophenacyl bromides, aqueous ammonia, and aldehydes. Moreover, dihydropyrido[2',1':2,3]imidazo[4,5-c]quinolines could also be obtained in a similar manner by using various ketones as the substrates in place of aldehydes. Notably, the whole procedure combines condensation/amination/cyclization reactions in one pot to give complex compounds in a simple and practical manner. Compared with literature methods, the synthetic strategy reported herein has the advantages of readily available starting materials, structural diversity of products, good functional group tolerance, and obviation of step-by-step operations.

  9. Click N-benzyl iminodiacetic acid: novel silica-based tridentate zwitterionic stationary phase for hydrophilic interaction liquid chromatography.

    PubMed

    Yin, Wei; Chai, Huihui; Liu, Renhua; Chu, Changhu; Palasota, John A; Cai, Xiaohui

    2015-01-01

    Iminodiacetic acid (IDA) is dicarboxylic acid amine, which may produce stronger interaction with polar or charged compounds than bidentate α,β-amino acid. In this article, a novel type of tridentate zwitterionic HILIC stationary phase was prepared by covalently bonding N-benzyl IDA on silica gel via copper(I) catalyzed Huisgen azide-alkyne 1,3-dipolar cycloaddition (CuAAC). The structure of this stationary phase and all related intermediates was confirmed by NMR, FT-IR, MS spectrum and elemental analysis. The new stationary phase showed good HILIC characteristics and high column efficiency (the theoretical plate number is up to 44000 plates m(-1) in the case of guanosine) in the application of separation of polar compounds, including organic acids, organic bases, as well as highly polar and hydrophilic compounds, such as cephalosporins and carbapenems. Most of them displayed good peak shape and selectivity. PMID:25476290

  10. Amine salts of nitroazoles

    DOEpatents

    Kienyin Lee; Stinecipher, M.M.

    1993-10-26

    Compositions of matter, a method of providing chemical energy by burning said compositions, and methods of making said compositions are described. These compositions are amine salts of nitroazoles. 1 figure.

  11. Utilization of rice husk ash as silica source for the synthesis of mesoporous silicas and their application to CO2 adsorption through TREN/TEPA grafting.

    PubMed

    Bhagiyalakshmi, Margandan; Yun, Lee Ji; Anuradha, Ramani; Jang, Hyun Tae

    2010-03-15

    Mesoporous MCM-41, MCM-48 and SBA-15 were synthesized using Rice husk ash (RHA) as the silica source and their defective Si-OH sites were functionalized by 3-chloropropyltrimethoxysilane (CPTMS) which was subsequently grafted with amine compounds, Tris(2-aminoethyl)amine (TREN) and Tetraethylenepentamine (TEPA). X-ray powder diffraction (XRD) and BET results of the parent mesoporous silica suggested their closeness of structural properties to those obtained from conventional silica sources. CO(2) adsorption of branched amine TREN and straight chain amine TEPA at 25, 50 and 75 degrees C was obtained by Thermogravimetric Analyser (TGA) at atmospheric pressure. TREN grafted mesoporous silica showed 7% of CO(2) adsorption while TEPA grafted mesoporous silicas showed less CO(2) adsorption, which is due to the presence of isolated amine groups in TREN. TREN grafted mesoporous silicas were also observed to be selective towards CO(2), thermally stable and recyclable. The order of CO(2) adsorption with respect to amount of amine grafting was observed to be MCM-48/TREN>MCM-41/TREN>SBA-15/TREN.

  12. Native silica nanoparticles are powerful membrane disruptors.

    PubMed

    Alkhammash, Hend I; Li, Nan; Berthier, Rémy; de Planque, Maurits R R

    2015-06-28

    Silica nanoparticles are under development for intracellular drug delivery applications but can also have cytotoxic effects including cell membrane damage. In this study, we investigated the interactions of silica nanospheres of different size, surface chemistry and biocoating with membranes of phosphatidylcholine lipids. In liposome leakage assays many, but not all, of these nanoparticles induced dose-dependent dye leakage, indicative of membrane perturbation. It was found that 200 and 500 nm native-silica, aminated and carboxylated nanospheres induce near-total dye release from zwitterionic phosphatidylcholine liposomes at a particle/liposome ratio of ∼1, regardless of their surface chemistry, which we interpret as particle-supported bilayer formation following a global rearrangement of the vesicular membrane. In contrast, 50 nm diameter native-silica nanospheres did not induce total dye leakage below a particle/liposome ratio of ∼8, whereas amination or carboxylation, respectively, strongly reduced or prevented dye release. We postulate that for the smaller nanospheres, strong silica-bilayer interactions are manifested as bilayer engulfment of membrane-adsorbed particles, with localized lipid depletion eventually leading to collapse of the vesicular membrane. Protein coating of the particles considerably reduced dye leakage and lipid bilayer coating prevented dye release all together, while the inclusion of 33% anionic lipids in the liposomes reduced dye leakage for both native-silica and aminated surfaces. These results, which are compared with the effect of polystyrene nanoparticles and other engineered nanomaterials on lipid bilayers, and which are discussed in relation to nanosilica-induced cell membrane damage and cytotoxicity, indicate that a native-silica nanoparticle surface chemistry is a particularly strong membrane interaction motif.

  13. Surface treatment of silica nanoparticles for stable and charge-controlled colloidal silica

    PubMed Central

    Kim, Kyoung-Min; Kim, Hye Min; Lee, Won-Jae; Lee, Chang-Woo; Kim, Tae-il; Lee, Jong-Kwon; Jeong, Jayoung; Paek, Seung-Min; Oh, Jae-Min

    2014-01-01

    An attempt was made to control the surface charge of colloidal silica nanoparticles with 20 nm and 100 nm diameters. Untreated silica nanoparticles were determined to be highly negatively charged and have stable hydrodynamic sizes in a wide pH range. To change the surface to a positively charged form, various coating agents, such as amine containing molecules, multivalent metal cation, or amino acids, were used to treat the colloidal silica nanoparticles. Molecules with chelating amine sites were determined to have high affinity with the silica surface to make agglomerations or gel-like networks. Amino acid coatings resulted in relatively stable silica colloids with a modified surface charge. Three amino acid moiety coatings (L-serine, L-histidine, and L-arginine) exhibited surface charge modifying efficacy of L-histidine > L-arginine > L-serine and hydrodynamic size preservation efficacy of L-serine > L-arginine > L-histidine. The time dependent change in L-arginine coated colloidal silica was investigated by measuring the pattern of the backscattered light in a Turbiscan™. The results indicated that both the 20 nm and 100 nm L-arginine coated silica samples were fairly stable in terms of colloidal homogeneity, showing only slight coalescence and sedimentation. PMID:25565824

  14. Method for inhibiting silica precipitation and scaling in geothermal flow systems

    DOEpatents

    Harrar, J.E.; Lorensen, L.E.; Locke, F.E.

    1980-06-13

    A method for inhibiting silica scaling and precipitation in geothermal flow systems by on-line injection of low concentrations of cationic nitrogen-containing compounds, particularly polymeric imines, polymeric amines, and quaternary ammonium compounds is described.

  15. Method for inhibiting silica precipitation and scaling in geothermal flow systems

    DOEpatents

    Harrar, Jackson E.; Lorensen, Lyman E.; Locke, Frank E.

    1982-01-01

    A method for inhibiting silica scaling and precipitation in geothermal flow systems by on-line injection of low concentrations of cationic nitrogen-containing compounds, particularly polymeric imines, polymeric amines, and quaternary ammonium compounds.

  16. Amine-Catalyzed Isomerization of Diethylmaleate to Diethylfumarate.

    ERIC Educational Resources Information Center

    Glover, Irving T.; And Others

    1978-01-01

    This reaction is used in an introductory organic chemistry course to illustrate principles of gas-liquid chromatography, geometrical isomerism, homogeneous catalysis, and activation energy determinations. (BB)

  17. Aromatic amines and cancer.

    PubMed

    Vineis, P; Pirastu, R

    1997-05-01

    Epidemiological evidence on the relation between aromatic amines and cancer risk is reviewed. In particular, cancer risk in humans resulting from exposure to aromatic amines from occupational sources and tobacco smoking is assessed with reference to ecologic, cohort, and case-control studies. Seven arylamines have been classified by the International Agency for Research on Cancer: benzidine-based dyes and MOCA (4,4'-methylene bis 2-choloroaniline) were considered 'probably' carcinogenic, Group 2A, because of a high level of evidence in experimental animals; two occupational chemicals (2-naphthylamine and benzidine), one drug (Chlornaphazine), and two manufacturing processes (manufacture of auramine and magenta) were included in Group 1 on the basis of 'sufficient' evidence of carcinogenicity in humans. Occupational exposures to aromatic amines explain up to 25 percent of bladder cancers in some areas of Western countries; these estimates might be higher in limited areas of developing countries. Aromatic amines contaminate the ambient air as a component of environmental tobacco smoke. There is increasing evidence that the excess of bladder cancer in smokers is attributable to aromatic amines rather than to other contaminants of tobacco smoke such as polycyclic aromatic hydrocarbons (PAH). A modulating role in the risk of bladder cancer associated with exposure to aromatic amines is played by metabolic polymorphisms, such as the N-acetyltransferase genotype, raising important social and ethical issues. The consistent observation of a difference between men and women in bladder cancer risk, after allowing for known risk factors, suggests consideration of gender-related biological determinants for future investigation.

  18. Azide Tripodal Dendrons from Behera's Amine and Their Clicked Dendrimers.

    PubMed

    Barmare, Farhana; Abadjian, Marie-Caline Z; Wiener, Erik C; Grotjahn, Douglas B

    2016-08-01

    Diazo transfer reactions on Behera's amine and its next-generation analogue formed G0 and G1 azide dendrons bearing three and nine tert-butyl-protected esters, respectively. The utility of the new dendrons was demonstrated by copper-catalyzed azide-alkyne cycloaddition, with 1,3,5-triethynylbenzene, forming two novel dendrimers in a convergent manner. Acid-mediated dendrimer deprotection was successful, and the resulting carboxy-terminated dendrimers were analyzed by NMR and DOSY experiments. PMID:27454340

  19. Oxidative Dehydrogenative Couplings of Pyrazol-5-amines Selectively Forming Azopyrroles

    PubMed Central

    2015-01-01

    New oxidative dehydrogenative couplings of pyrazol-5-amines for the selective synthesis of azopyrrole derivatives have been described. The former reaction simultaneously installs C–I and N–N bonds through iodination and oxidation, whereas the latter involved a copper-catalyzed oxidative coupling process. The resulting iodo-substituted azopyrroles were employed by treatment with various terminal alkynes through Sonogashira cross-coupling leading to new azo compounds. PMID:24731223

  20. DFT Study of Pd(0)-Promoted Intermolecular C-H Amination with O-Benzoyl Hydroxylamines.

    PubMed

    Zhou, Yunfei; Bao, Xiaoguang

    2016-09-16

    Computational studies were carried out to explore the mechanism of Pd-catalyzed intermolecular C-H amination with O-benzoyl hydroxylamines in which both Pd(0) and Pd(II) catalysts are effective. For the Pd(0)-catalyzed reaction, the generally assumed Pd(0)/Pd(II) catalytic cycle might not be feasible. Instead, Pd(0), being essentially a catalyst precursor, could be oxidized to Pd(II), and the C-H amination proceeds through the Pd(II)/Pd(IV) catalytic cycle. PMID:27573977

  1. High capacity immobilized amine sorbents

    DOEpatents

    Gray, McMahan L.; Champagne, Kenneth J.; Soong, Yee; Filburn, Thomas

    2007-10-30

    A method is provided for making low-cost CO.sub.2 sorbents that can be used in large-scale gas-solid processes. The improved method entails treating an amine to increase the number of secondary amine groups and impregnating the amine in a porous solid support. The method increases the CO.sub.2 capture capacity and decreases the cost of utilizing an amine-enriched solid sorbent in CO.sub.2 capture systems.

  2. Synthesis of sub-nanometer gold particles on modified silica.

    PubMed

    Beloqui Redondo, A; Ranocchiari, M; van Bokhoven, J A

    2016-02-21

    The deposition of gold on silica tends to give large particles when using conventional techniques. We report the preparation of 0.8 ± 0.2 nm particles on a modified SBA-15 support. The method involves the functionalization of silica with amine groups and deposition of gold at basic pH. These catalysts are highly active and selective in the dehydrogenation of formic acid. PMID:26754911

  3. Enantioselective separation of racemic secondary amines on a chiral crown ether-based liquid chromatography stationary phase.

    PubMed

    Steffeck, Robert J; Zelechonok, Yury; Gahm, Kyung H

    2002-02-22

    The first general enantioselective separation of racemic secondary amines on a crown ether-based liquid chromatography chiral stationary phase (CSP) is presented. The CSP is based on (+)- or (-)-(18-crown-6)-2,3,11,12-tetracarboxylic acid covalently bonded to silica gel. A mobile phase containing methanol, acetonitrile, triethylamine and acetic acid was employed in these separations of secondary amines with crown ether CSPs. The separation mechanism is believed to be the secondary amine forming a complex which includes crown ether coordination and electrostatic interaction of the positively charged amine with a carboxylate anion of the immobilized crown ether.

  4. Photocatalyzed multiple additions of amines to {alpha}, {beta}-unsaturated esters and nitriles

    SciTech Connect

    Das, S.; Kumar, J.S.D.; Thomas, K.G.; Shivaramayya, K.; George, M.V. |

    1994-02-11

    Photoelectron-transfer-catalyzed intermolecular carbon-carbon bond formation of primary, secondary, and tertiary amines with {alpha}, {beta}-unsaturated esters and nitriles using photosensitizers such as anthraquinone, acridone, and dicyanoanthracene has been investigated. The addition of {alpha}-aminoalkyl radicals, generated via photoelectron-transfer processes, to olefinic substrates and the subsequent 1,5-hydrogen abstraction reactions of the amine-olefin adduct radicals lead to a number of interesting multiple-olefin-added products. The adducts of the primary and secondary amines with {alpha}, {beta}-unsaturated esters undergo further cyclizations to give spiro and cyclic lactams, respectively.

  5. ORGANIC CHEMISTRY. Catalytic asymmetric hydroamination of unactivated internal olefins to aliphatic amines.

    PubMed

    Yang, Yang; Shi, Shi-Liang; Niu, Dawen; Liu, Peng; Buchwald, Stephen L

    2015-07-01

    Catalytic assembly of enantiopure aliphatic amines from abundant and readily available precursors has long been recognized as a paramount challenge in synthetic chemistry. Here, we describe a mild and general copper-catalyzed hydroamination that effectively converts unactivated internal olefins—an important yet unexploited class of abundant feedstock chemicals—into highly enantioenriched α-branched amines (≥96% enantiomeric excess) featuring two minimally differentiated aliphatic substituents. This method provides a powerful means to access a broad range of advanced, highly functionalized enantioenriched amines of interest in pharmaceutical research and other areas.

  6. Factors influencing phase-disengagement rates in solvent-extraction systems employing tertiary amine extractants

    SciTech Connect

    Moyer, B.A.; McDowell, W.J.

    1981-01-01

    The primary purpose of the present investigation was to examine the effects of amine size and structure on phase disengagement. Nine commercial tertiary amines were tested together with four laboratory-quality amines for uranium extraction and both organic-continuous (OC) and aqueous-continuous (AC) phase disengagement under Amex-type conditions. Synthetic acid sulfate solutions with and without added colloidal silica and actual ore leach solutions were used as the aqueous phases. Phase disengagement results were correlated with amine size and branching and solution wetting behavior on a silicate (glass) surface. The results suggest that the performance of some Amex systems may be improved by using branched chain tertiary amine extractants of higher molecular weight than are now normally used.

  7. Degradation and transformation of atrazine under catalyzed ozonation process with TiO2 as catalyst.

    PubMed

    Yang, Yixin; Cao, Hongbin; Peng, Pai; Bo, Hongmiao

    2014-08-30

    Degradation of atrazine by heterogeneously catalyzed ozonation was carried out with TiO2 in the form of rutile as the catalyst. Some experimental factors such as catalyst dose, ozone dose and initial concentration of atrazine were investigated for their influence on catalyzed ozonation process. Although atrazine was effectively removed from aqueous solution by catalyzed ozonation process, the mineralization degree only reached 56% at the experimental conditions. Five transformation products were identified by GC/MS analysis. The degradation of atrazine involved de-alkylation, de-chlorination and de-amination. Diaminotriazine and 5-azauracil were the de-chlorinated and de-aminated products, respectively. The evolution of concentration of transformation products during catalyzed ozonation process was compared with uncatalyzed ozonation to show the degradation pathway. Toxicity tests based on the inhibition of the luminescence emitted by Vibrio fisheri indicated the detoxification of atrazine by catalyzed ozonation. PMID:25106044

  8. Degradation and transformation of atrazine under catalyzed ozonation process with TiO2 as catalyst.

    PubMed

    Yang, Yixin; Cao, Hongbin; Peng, Pai; Bo, Hongmiao

    2014-08-30

    Degradation of atrazine by heterogeneously catalyzed ozonation was carried out with TiO2 in the form of rutile as the catalyst. Some experimental factors such as catalyst dose, ozone dose and initial concentration of atrazine were investigated for their influence on catalyzed ozonation process. Although atrazine was effectively removed from aqueous solution by catalyzed ozonation process, the mineralization degree only reached 56% at the experimental conditions. Five transformation products were identified by GC/MS analysis. The degradation of atrazine involved de-alkylation, de-chlorination and de-amination. Diaminotriazine and 5-azauracil were the de-chlorinated and de-aminated products, respectively. The evolution of concentration of transformation products during catalyzed ozonation process was compared with uncatalyzed ozonation to show the degradation pathway. Toxicity tests based on the inhibition of the luminescence emitted by Vibrio fisheri indicated the detoxification of atrazine by catalyzed ozonation.

  9. Ceria-Vanadia/Silica-Catalyzed Cascade for C-C and C-O Bond Activation: Green One-Pot Synthesis of 2-Amino-3-cyano-4H-pyrans.

    PubMed

    Maddila, Surya Narayana; Maddila, Suresh; van Zyl, Werner E; Jonnalagadda, Sreekantha B

    2016-02-01

    We designed a ceria-vanadia/silica (Ce-V/SiO2) heterogeneous catalyst and used it for the green and efficient synthesis of 2-amino-3-cyano-4H-pyran derivatives. The green reaction was a multicomponent one-pot condensation of 5,5-dimethylcyclohexane-1,3-dione, aromatic aldehyde, and malononitrile in an eco-compatible solvent (ethanol). The catalyst was synthesized and fully characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area analysis. The reported procedure offers a number of advantages including decreased reaction times, mild conditions, high yields, operational simplicity, and environmentally benign and simple work-up procedures. Furthermore, the catalyst is economical, fully recyclable, and reusable for over five runs while preserving its high activity. The synthesized 2-amino-3-cyano-4H-pyran products can later be used for pharmaceutical purposes. PMID:27308209

  10. Ceria-Vanadia/Silica-Catalyzed Cascade for C-C and C-O Bond Activation: Green One-Pot Synthesis of 2-Amino-3-cyano-4H-pyrans.

    PubMed

    Maddila, Surya Narayana; Maddila, Suresh; van Zyl, Werner E; Jonnalagadda, Sreekantha B

    2016-02-01

    We designed a ceria-vanadia/silica (Ce-V/SiO2) heterogeneous catalyst and used it for the green and efficient synthesis of 2-amino-3-cyano-4H-pyran derivatives. The green reaction was a multicomponent one-pot condensation of 5,5-dimethylcyclohexane-1,3-dione, aromatic aldehyde, and malononitrile in an eco-compatible solvent (ethanol). The catalyst was synthesized and fully characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area analysis. The reported procedure offers a number of advantages including decreased reaction times, mild conditions, high yields, operational simplicity, and environmentally benign and simple work-up procedures. Furthermore, the catalyst is economical, fully recyclable, and reusable for over five runs while preserving its high activity. The synthesized 2-amino-3-cyano-4H-pyran products can later be used for pharmaceutical purposes.

  11. From Racemic Alcohols to Enantiopure Amines: Ru-Catalyzed Diastereoselective Amination

    PubMed Central

    2015-01-01

    A commercially available ruthenium(II) PNP-type pincer catalyst (Ru-Macho) promotes the formation of α-chiral tert-butanesulfinylamines from racemic secondary alcohols and Ellman’s chiral tert-butanesulfinamide via a hydrogen borrowing strategy. The formation of α-chiral tert-butanesulfinylamines occurs in yields ranging from 31% to 89% with most examples giving >95:5 dr. PMID:25170560

  12. From racemic alcohols to enantiopure amines: Ru-catalyzed diastereoselective amination.

    PubMed

    Oldenhuis, Nathan J; Dong, Vy M; Guan, Zhibin

    2014-09-10

    A commercially available ruthenium(II) PNP-type pincer catalyst (Ru-Macho) promotes the formation of α-chiral tert-butanesulfinylamines from racemic secondary alcohols and Ellman's chiral tert-butanesulfinamide via a hydrogen borrowing strategy. The formation of α-chiral tert-butanesulfinylamines occurs in yields ranging from 31% to 89% with most examples giving >95:5 dr. PMID:25170560

  13. Metabolism of aromatic amines by prostaglandin H synthase.

    PubMed Central

    Boyd, J A; Eling, T E

    1985-01-01

    The metabolism of aromatic amines by the peroxidase activity of prostaglandin H synthase (PHS) has been studied in this laboratory by use of two model compounds, the carcinogenic primary amine 2-aminofluorene (2-AF) and the substituted amine aminopyrine (AP). 2-AF is oxidized by PHS to 2, 2-azobisfluorene, 2-aminodifluorenylamine, 2-nitrofluorene, polymeric material, and products covalently bound to macromolecules. In the presence of phenolic compounds, 2-AF oxidation results in the formation of amine/phenol adducts. The data are consistent with a one-electron mechanism of 2-AF oxidation by PHS; furthermore, an N-hydroxy intermediate is not involved in 2-AF metabolism by PHS. PHS also catalyzes the binding of 2-AF to DNA in vitro. Unique 2-AF/DNA adducts were isolated and are distinct from the N-(deoxyguanosin-8-yl)-2-AF adduct formed from the reaction of N-hydroxy-2-AF with DNA. These new adducts represent a marker unique to peroxidative activation of 2-AF. AP is oxidized by the peroxidase activity of PHS to the cation radical, with one molecule of hydroperoxy fatty acid reduced for every two molecules of AP free radical formed. The decay of the AP radical follows second order kinetics, supporting the proposed mechanism in which the AP radical disproportionates to an iminium cation, followed by hydrolysis of this species to the demethylated amine and formaldehyde. In the presence of glutathione, the cation radical is reduced to the parent amine, resulting in the formation of the glutathione thiyl radical. It thus appears that both primary and substituted aromatic amines may undergo one-electron oxidation by PHS. PMID:3938394

  14. Metabolism of aromatic amines by prostaglandin H synthase

    SciTech Connect

    Boyd, J.A.; Eling, T.E.

    1985-12-01

    The metabolism of aromatic amines by the peroxidase activity of prostaglandin H synthase (PHS) has been studied in this laboratory by use of two model compounds, the carcinogenic primary amine 2-aminofluorene (2-AF) and the substituted amine aminopyrine (AP). 2-AF is oxidized by PHS to 2, 2-azobisfluorene, 2-aminodifluorenylamine, 2-nitrofluorene, polymeric material, and products covalently bound to macromolecules. In the presence of phenolic compounds, 2-AF oxidation results in the formation of amine-phenol adducts. The data are consistent with a one-electron mechanism of 2-AF oxidation by PHS; furthermore, an N-hydroxy intermediate is not involved in 2-AF metabolism by PHS. PHS also catalyzes the binding of 2-AF to DNA in vitro. Unique 2-AF/DNA adducts were isolated and are distinct from the N-(deoxyguanosin-8-yl)-2-AF adduct formed from the reaction of N-hydroxy-2-AF with DNA. These new adducts represent a marker unique to peroxidative activation of 2-AF. AP is oxidized by the peroxidase activity of PHS to the cation radical, with one molecule of hydroperoxy fatty acid reduced for every two molecules of AP free radical formed. The decay of the AP radical follows second order kinetics, supporting the proposed mechanism in which the AP radical disproportionates to an iminium cation, followed by hydrolysis of this species to the demethylated amine and formaldehyde. In the presence of glutathione, the cation radical is reduced to the parent amine, resulting in the formation of the glutathione thiyl radical. It thus appears that both primary and substituted aromatic amines may undergo one-electron oxidation by PHS. 19 references.

  15. Asymmetric petasis reactions catalyzed by chiral biphenols.

    PubMed

    Lou, Sha; Schaus, Scott E

    2008-06-01

    Chiral biphenols catalyze the enantioselective Petasis reaction of alkenyl boronates, secondary amines, and ethyl glyoxylate. The reaction requires the use of 15 mol % of (S)-VAPOL as the catalyst, alkenyl boronates as nucleophiles, ethyl glyoxylate as the aldehyde component, and 3 A molecular sieves as an additive. The chiral alpha-amino ester products are obtained in good yields (71-92%) and high enantiomeric ratios (89:11-98:2). Mechanistic investigations indicate single ligand exchange of acyclic boronate with VAPOL and tetracoordinate boronate intermediates. PMID:18459782

  16. Amine terminated bisaspartimide polymer

    NASA Technical Reports Server (NTRS)

    Kumar, D. (Inventor); Fohlen, G. M. (Inventor); Parker, J. A. (Inventor)

    1986-01-01

    Novel amine terminated bisaspartimides are prepared by a Michael-type reaction of an aromatic bismalteimide and an aromatic diamine in an aprotic solvent. These bisaspartimides are thermally polymerized to yield tough, resinous polymers cross-lined through -NH- groups. Such polymers are useful in applications requiring materials with resistance to change at elevated temperatures, e.g., as lightweight laminates with graphite cloth, molding material prepregs, adhesives and insulating material.

  17. The interaction of encapsulated pharmaceutical drugs with a silica matrix.

    PubMed

    Morais, Everton C; Correa, Gabriel G; Brambilla, Rodrigo; Radtke, Claudio; Baibich, Ione Maluf; dos Santos, João Henrique Z

    2013-03-01

    A series of seven drugs, namely, fluoxetine, gentamicin, lidocaine, morphine, nifedipine, paracetamol and tetracycline, were encapsulated. The encapsulated systems were characterized using a series of complementary techniques: Fourier-transform infrared spectroscopy (FT-IR), diffusive reflectance spectroscopy in the UV-vis region (DRS) and X-ray photoelectron spectroscopy (XPS). According to the DRS spectra, most of the encapsulated systems showed a band shift of the maximum absorption when compared with the corresponding bare pharmaceutical. Additionally, after encapsulation, the drugs exhibited infrared band shifts toward higher wavenumbers, which in turn provided insight into potential sites for interaction with the silica framework. The amine group showed a band shift in the spectra of almost all the drugs (except nifedipine and tetracycline). This finding indicates the possibility of a hydrogen bonding interaction between the drug and the silica via electron donation from the amine group to the silica framework. XPS confirmed this interaction between the pharmaceuticals and the silica through the amine group. A correlation was observed between the textural characteristics of the solids and the spectroscopic data, suggesting that the amine groups from the pharmaceuticals were more perturbed upon encapsulation. PMID:23261562

  18. Metal-silica sol-gel materials

    NASA Technical Reports Server (NTRS)

    Stiegman, Albert E. (Inventor)

    2002-01-01

    The present invention relates to a single phase metal-silica sol-gel glass formed by the co-condensation of a transition metal with silicon atoms where the metal atoms are uniformly distributed within the sol-gel glass as individual metal centers. Any transition metal may be used in the sol-gel glasses. The present invention also relates to sensor materials where the sensor material is formed using the single phase metal-silica sol-gel glasses. The sensor materials may be in the form of a thin film or may be attached to an optical fiber. The present invention also relates to a method of sensing chemicals using the chemical sensors by monitoring the chromatic change of the metal-silica sol-gel glass when the chemical binds to the sensor. The present invention also relates to oxidation catalysts where a metal-silica sol-gel glass catalyzes the reaction. The present invention also relates to a method of performing oxidation reactions using the metal-silica sol-gel glasses. The present invention also relates to organopolymer metal-silica sol-gel composites where the pores of the metal-silica sol-gel glasses are filled with an organic polymer polymerized by the sol-gel glass.

  19. Synthesis of substituted quinolines via allylic amination and intramolecular Heck-coupling.

    PubMed

    Murru, Siva; McGough, Brandon; Srivastava, Radhey S

    2014-12-01

    A new catalytic approach for the synthesis of substituted quinolines via C-N and C-C bond formation using 2-haloaryl hydroxylamines and allylic C-H substrates is described. Fe-catalyzed allylic C-H amination followed by Pd-catalyzed intramolecular Heck-coupling and aerobic dehydrogenation deliver the valuable quinoline and naphthyridine heterocycles in good to excellent overall yields. In this process, Pd(OAc)2 plays a dual role in catalyzing Heck coupling as well as aerobic dehydrogenation of dihydroquinolines. PMID:25247637

  20. Rational ligand design for the arylation of hindered primary amines guided by reaction progress kinetic analysis.

    PubMed

    Ruiz-Castillo, Paula; Blackmond, Donna G; Buchwald, Stephen L

    2015-03-01

    We report the Pd-catalyzed arylation of very hindered α,α,α-trisubstituted primary amines. Kinetics-based mechanistic analysis and rational design have led to the development of two biarylphosphine ligands that allow the transformation to proceed with excellent efficiency. The process was effective in coupling a wide range of functionalized aryl and heteroaryl halides under mild conditions.

  1. Insights into the oxidative dehydrogenation of amines with nanoparticulate iridium oxide.

    PubMed

    Hammond, Ceri; Schümperli, Martin T; Hermans, Ive

    2013-09-23

    The aerobic oxidation of amines offers a promising route towards many versatile chemical compounds. Within this contribution, we extend our previous investigations of iridium oxide-catalyzed alcohol oxidation to amine substrates. In addition to demonstrating the versatility of this catalyst, particular attention is focused on the mechanisms of the reaction. Herein, we demonstrate that although amines are oxidized slower than the corresponding alcohols, the catalyst has a preference for amine substrates, and oxidizes various amines at turnover frequencies greater than other systems found in the open literature. Furthermore, the competition between double amine dehydrogenation, to yield the corresponding nitrile, and amine-imine coupling, to yield the corresponding coupled imine, has been found to arise from a competitive reaction pathway, and stems from an effect of substrate-to-metal ratio. Finally, the mechanism responsible for the formation of N-benzylidene-1-phenylmethanamine was examined, and attributed to the coupling of free benzyl amine substrate and benzaldehyde, formed in situ through hydrolysis of the primary reaction product, benzyl imine. PMID:23939827

  2. Silica reusable surface insulation

    NASA Technical Reports Server (NTRS)

    Goldstein, H. E.; Smith, M.; Leiser, D. B. (Inventor)

    1976-01-01

    A reusable silica surface insulation material is provided by bonding amorphous silica fibers with colloidal silica at an elevated temperature. The surface insulation is ordinarily manufactured in the form of blocks (i.e., tiles).

  3. New porous polycaprolactone-silica composites for bone regeneration.

    PubMed

    Plazas Bonilla, Clara E; Trujillo, Sara; Demirdögen, Bermali; Perilla, Jairo E; Murat Elcin, Y; Gómez Ribelles, José L

    2014-07-01

    Polycaprolactone porous membranes were obtained by freeze extraction of dioxane from polycaprolactone-dioxane solid solutions. Porosities as high as 90% with interconnected structures were obtained by this technique. A silica phase was synthesized inside the pores of the polymer membrane by sol-gel reaction using tetraethylorthosilicate (TEOS) as a silica precursor and catalyzed in acidic and basic conditions. Two different morphologies of the inorganic phase were obtained depending on the type of catalyst. In acid catalyzed sol-gel reaction, a homogeneous layer of silica was deposited on the pores, and discrete microspheres were synthesized on the pore walls when a basic catalyst was used. The morphology of the inorganic phase influenced the mechanical and thermal behavior, as well as the hydrophilic character of the composites. Bioactivity of the porous materials was tested in vitro by measuring the deposition of hydroxyapatite on the surfaces of the porous composite membranes. Polycaprolactone/silica composites revealed a superior bioactivity performance compared with that of the pure polymer; evidenced by the characteristic cauliflower structures on the material surface, increase in weight and Ca/P ratio of the hydroxyapatite layer. Also, the acid catalyzed composites presented better bioactivity than the base catalyzed composites, evidencing the importance in the morphology of the silica phase.

  4. Aminosilane-grafted polymer/silica hollow fiber adsorbents for CO₂ capture from flue gas.

    PubMed

    Rezaei, Fateme; Lively, Ryan P; Labreche, Ying; Chen, Grace; Fan, Yanfang; Koros, William J; Jones, Christopher W

    2013-05-01

    Amine/silica/polymer composite hollow fiber adsorbents are produced using a novel reactive post-spinning infusion technique, and the obtained fibers are shown to capture CO2 from simulated flue gas. The post-spinning infusion technique allows for functionalization of polymer/silica hollow fibers with different types of amines during the solvent exchange step after fiber spinning. The post-spinning infusion of 3-aminopropyltrimethoxysilane (APS) into mesoporous silica/cellulose acetate hollow fibers is demonstrated here, and the materials are compared with hollow fibers infused with poly(ethyleneimine) (PEI). This approach results in silica/polymer composite fibers with good amine distribution and accessibility, as well as adequate porosity retained within the fibers to facilitate rapid mass transfer and adsorption kinetics. The CO2 adsorption capacities for the APS-infused hollow fibers are shown to be comparable to those of amine powders with similar amine loadings. In contrast, fibers that are spun with presynthesized, amine-loaded mesoporous silica powders show negligible CO2 uptake and low amine loadings because of loss of amines from the silica materials during the fiber spinning process. Aminosilica powders are shown to be more hydrophilic than the corresponding amine containing composite hollow fibers, the bare polymer as well as silica support. Both the PEI-infused and APS-infused fibers demonstrate reduced CO2 adsorption upon elevating the temperature from 35 to 80 °C, in accordance with thermodynamics, whereas PEI-infused powders show increased CO2 uptake over that temperature range because of competing diffusional and thermodynamic effects. The CO2 adsorption kinetics as probed via TGA show that the APS-infused hollow fiber adsorbents have more rapid uptake kinetics than their aminosilica powder analogues. The adsorption performance of the functionalized hollow fibers is also assessed in CO2 breakthrough experiments. The breakthrough results show a

  5. Biogenic amines in natural ciders.

    PubMed

    Garai, G; Dueñas, M T; Irastorza, A; Martín-Alvarez, P J; Moreno-Arribas, M V

    2006-12-01

    Biogenic amines play an important physiological role in mammals, and high amounts of some exogenous amines in human diet may contribute to a wide variety of toxic effects. These amines are commonly found in many foodstuffs, particularly in fermented products such as cheese, meat products, beer, wine, and ciders. Here, the level of biogenic amines in some natural ciders was examined. Twenty-four samples of cider purchased from commercial sources were analyzed by reverse-phase high-performance liquid chromatography and fluorescence detection after precolumn derivatization with o-phthaldialdehyde. Amine levels were variable, ranging from not detected to 23 mg/liter. The average level of total biogenic amines in ciders was 5.94 +/- 8.42 mg/liter. Putrescine, histamine, and tyramine were the prevailing amines being present in 50.0, 37.5, and 33.3% of the ciders studied; very small amounts of ethylamine and phenylethylamine were observed in only one sample. Other cider parameters were analyzed to determine whether they affect the biogenic amine content in ciders, and the results were evaluated by applying cluster analysis and principal component analysis. Ciders that showed lower glycerol contents and higher amounts of 1,3-propanediol had much higher levels of histamine, tyramine, and putrescine, suggesting a high activity of lactic acid bacteria during cider making and thus the need for effective control of lactic acid bacteria. PMID:17186671

  6. Alumina-entrapped Ag catalyzed nitro compounds coupled with alcohols using borrowing hydrogen methodology.

    PubMed

    Liu, Huihui; Chuah, Gaik Khuan; Jaenicke, Stephan

    2015-06-14

    Supported silver catalysts were reported for the first time to be able to catalyze the coupling reaction between nitroarenes and alcohols via the borrowing hydrogen scheme. The recyclable, non-leaching catalyst is synthesized by the entrapment method, which allows entrapping of silver nanoparticles in an alumina matrix. Alcohols, acting as the reducing agents for nitro-groups, alkylated the resultant amines smoothly over these silver catalysts giving a yield of >98% towards the N-substituted amines. In this process, multiple steps were realized in one-pot over a single catalyst with very high efficiency. It offers another clean and economic way to achieve amination of alcohols. PMID:25989446

  7. 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

  8. Intramolecular C(sp(3))H amination of arylsulfonyl azides with engineered and artificial myoglobin-based catalysts.

    PubMed

    Bordeaux, Melanie; Singh, Ritesh; Fasan, Rudi

    2014-10-15

    The direct conversion of aliphatic CH bonds into CN bonds provides an attractive approach to the introduction of nitrogen-containing functionalities in organic molecules. Following the recent discovery that cytochrome P450 enzymes can catalyze the cyclization of arylsulfonyl azide compounds via an intramolecular C(sp(3))H amination reaction, we have explored here the CH amination reactivity of other hemoproteins. Various heme-containing proteins, and in particular myoglobin and horseradish peroxidase, were found to be capable of catalyzing this transformation. Based on this finding, a series of engineered and artificial myoglobin variants containing active site mutations and non-native Mn- and Co-protoporphyrin IX cofactors, respectively, were prepared to investigate the effect of these structural changes on the catalytic activity and selectivity of these catalysts. Our studies showed that metallo-substituted myoglobins constitute viable CH amination catalysts, revealing a distinctive reactivity trend as compared to synthetic metalloporphyrin counterparts. On the other hand, amino acid substitutions at the level of the heme pocket were found to be beneficial toward improving the stereo- and enantioselectivity of these Mb-catalyzed reactions. Mechanistic studies involving kinetic isotope effect experiments indicate that CH bond cleavage is implicated in the rate-limiting step of myoglobin-catalyzed amination of arylsulfonyl azides. Altogether, these studies indicate that myoglobin constitutes a promising scaffold for the design and development of CH amination catalysts. PMID:24890656

  9. Direct amine-functionalisation of γ-Fe2O3 nanoparticles.

    PubMed

    Rocher, V; Manerova, J; Kinnear, M; Evans, D J; Francesconi, M G

    2014-02-21

    A novel and simple preparation of amine-modified γ-Fe2O3 nanoparticles is described. The presence of amine groups on the surface, instead of hydroxyl groups, will allow conjugation of biologically active molecules to the iron oxide nanoparticles without the need for a size increasing silica shell. Furthermore, the outer amine-layer increases the temperature of the γ-Fe2O3 to α-Fe2O3 structural transition in a similar way to previously reported cationic substitutions. This may suggest the formation of an oxide-nitride outer layer. Re-dispersion of the amine-modified γ-Fe2O3 nanoparticles led to the preparation of stable ferrofluids. PMID:24347049

  10. Co(II) PCP Pincer Complexes as Catalysts for the Alkylation of Aromatic Amines with Primary Alcohols.

    PubMed

    Mastalir, Matthias; Tomsu, Gerald; Pittenauer, Ernst; Allmaier, Günter; Kirchner, Karl

    2016-07-15

    Efficient alkylations of amines by alcohols catalyzed by well-defined Co(II) complexes are described that are stabilized by a PCP ligand (N,N'-bis(diisopropylphosphino)-N,N'-dimethyl-1,3-diaminobenzene) based on the 1,3-diaminobenzene scaffold. This reaction is an environmentally benign process implementing inexpensive, earth-abundant nonprecious metal catalysts and is based on the acceptorless alcohol dehydrogenation concept. A range of primary alcohols and aromatic amines were efficiently converted into mono-N-alkylated amines in good to excellent isolated yields. PMID:27356282

  11. Silica and titanium dioxide nanoparticles cause pregnancy complications in mice

    NASA Astrophysics Data System (ADS)

    Yamashita, Kohei; Yoshioka, Yasuo; Higashisaka, Kazuma; Mimura, Kazuya; Morishita, Yuki; Nozaki, Masatoshi; Yoshida, Tokuyuki; Ogura, Toshinobu; Nabeshi, Hiromi; Nagano, Kazuya; Abe, Yasuhiro; Kamada, Haruhiko; Monobe, Youko; Imazawa, Takayoshi; Aoshima, Hisae; Shishido, Kiyoshi; Kawai, Yuichi; Mayumi, Tadanori; Tsunoda, Shin-Ichi; Itoh, Norio; Yoshikawa, Tomoaki; Yanagihara, Itaru; Saito, Shigeru; Tsutsumi, Yasuo

    2011-05-01

    The increasing use of nanomaterials has raised concerns about their potential risks to human health. Recent studies have shown that nanoparticles can cross the placenta barrier in pregnant mice and cause neurotoxicity in their offspring, but a more detailed understanding of the effects of nanoparticles on pregnant animals remains elusive. Here, we show that silica and titanium dioxide nanoparticles with diameters of 70 nm and 35 nm, respectively, can cause pregnancy complications when injected intravenously into pregnant mice. The silica and titanium dioxide nanoparticles were found in the placenta, fetal liver and fetal brain. Mice treated with these nanoparticles had smaller uteri and smaller fetuses than untreated controls. Fullerene molecules and larger (300 and 1,000 nm) silica particles did not induce these complications. These detrimental effects are linked to structural and functional abnormalities in the placenta on the maternal side, and are abolished when the surfaces of the silica nanoparticles are modified with carboxyl and amine groups.

  12. Access to 4-alkylaminopyridazine derivatives via nitrogen-assisted regioselective Pd-catalyzed reactions.

    PubMed

    Blaise, Emilie; Kümmerle, Arthur E; Hammoud, Hassan; de Araújo-Júnior, João Xavier; Bihel, Frédéric; Bourguignon, Jean-Jacques; Schmitt, Martine

    2014-11-01

    3-Substituted, 6-substituted, and unsymmetrical 3,6-disubstituted 4-alkylaminopyridazines were prepared from a sequence of three chemo- and regioselective reactions combining amination and palladium-catalyzed cross-coupling reactions, such as reductive dehalogenation and Suzuki-Miyaura reactions. Extension of the methodology to Sonogashira reaction yielded a novel class of 3-substituted pyrrolopyridazines. PMID:25310174

  13. Biphenol-based phosphoramidite ligands for the enantioselective copper-catalyzed conjugate addition of diethylzinc.

    PubMed

    Alexakis, Alexandre; Polet, Damien; Rosset, Stéphane; March, Sébastien

    2004-08-20

    Phosphoramidite ligands, based on ortho-substituted biphenols and a chiral amine, induce high enantioselectivities (ee's up to 99%) in the copper-catalyzed conjugate addition of dialkylzinc reagents to a variety of Michael acceptors. Particularly, the best reported ee's were obtained for acyclic nitroolefins. PMID:15307737

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

    PubMed

    Masruri; Willis, Anthony C; McLeod, Malcolm D

    2012-10-01

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

  15. Copper-catalyzed diastereo- and enantioselective desymmetrization of cyclopropenes: synthesis of cyclopropylboronates.

    PubMed

    Parra, Alejandro; Amenós, Laura; Guisán-Ceinos, Manuel; López, Aurora; García Ruano, José Luis; Tortosa, Mariola

    2014-11-12

    A novel Cu-catalyzed diastereo- and enantioselective desymmetrization of cyclopropenes to afford nonracemic cyclopropylboronates is described. Trapping the cyclopropylcopper intermediate with electrophilic amines allows for the synthesis of cyclopropylaminoboronic esters and demonstrates the potential of the approach for the synthesis of functionalized cyclopropanes. PMID:25340304

  16. Gold(III)-catalyzed three-component coupling reaction (TCC) selective toward furans.

    PubMed

    Li, Jian; Liu, Li; Ding, Dong; Sun, Jiangtao; Ji, Yangxuan; Dong, Jialing

    2013-06-01

    An efficient three-component coupling reaction toward a variety of furan derivatives has been developed. This cascade transformation proceeds via the gold-catalyzed coupling reaction of phenylglyoxal derivatives, secondary amines, and terminal alkynes, under the reaction conditions, that undergoes cyclization into the furan core.

  17. A highly efficient bismuth salts-catalyzed route for the synthesis of α-aminophosphonates.

    PubMed

    Banik, Antara; Batta, Sahil; Bandyopadhyay, Debasish; Banik, Bimal K

    2010-11-01

    A convenient synthesis of different types of α-amino phosphonates via one-pot solvent-free three component reactions of aldehydes, amines and phosphites catalyzed by bismuth salts has been investigated. Bismuth triflate is found to be the most effective catalyst for this reaction. PMID:21076387

  18. Copper-catalyzed aminooxygenation of styrenes with N-fluorobenzenesulfonimide and N-hydroxyphthalimide derivatives

    PubMed Central

    Li, Yan; Zhou, Xue; Zheng, Guangfan

    2015-01-01

    Summary A copper-catalyzed aminooxygenation reaction of styrenes with N-fluorobenzenesulfonimide and N-hydroxyphthalimide derivatives has been developed. The aminooxygenation product could be converted into the corresponding alcohol or free amine through the cleavage of the N–O or C–N bond of the N-hydroxyphthalimide moiety. PMID:26877794

  19. Allylic C-H amination for the preparation of syn-1,3-amino alcohol motifs.

    PubMed

    Rice, Grant T; White, M Christina

    2009-08-26

    A highly selective and general Pd/sulfoxide-catalyzed allylic C-H amination reaction en route to syn-1,3-amino alcohol motifs is reported. Key to achieving this reactivity under mild conditions is the use of electron-deficient N-nosyl carbamate nucleophiles that are thought to promote functionalization by furnishing higher concentrations of anionic species in situ. The reaction is shown to be orthogonal to classical C-C bond-forming/-reduction sequences as well as nitrene-based C-H amination methods.

  20. Muon Catalyzed Fusion

    NASA Technical Reports Server (NTRS)

    Armour, Edward A.G.

    2007-01-01

    Muon catalyzed fusion is a process in which a negatively charged muon combines with two nuclei of isotopes of hydrogen, e.g, a proton and a deuteron or a deuteron and a triton, to form a muonic molecular ion in which the binding is so tight that nuclear fusion occurs. The muon is normally released after fusion has taken place and so can catalyze further fusions. As the muon has a mean lifetime of 2.2 microseconds, this is the maximum period over which a muon can participate in this process. This article gives an outline of the history of muon catalyzed fusion from 1947, when it was first realised that such a process might occur, to the present day. It includes a description of the contribution that Drachrnan has made to the theory of muon catalyzed fusion and the influence this has had on the author's research.

  1. Enantioselective Generation of Adjacent Stereocenters in a Copper-Catalyzed Three-Component Coupling of Imines, Allenes, and Diboranes.

    PubMed

    Yeung, Kay; Ruscoe, Rebecca E; Rae, James; Pulis, Alexander P; Procter, David J

    2016-09-19

    A highly enantio- and diastereoselective copper-catalyzed three-component coupling affords the first general synthesis of homoallylic amines bearing adjacent stereocenters from achiral starting materials. The method utilizes a commercially available NHC ligand and copper source, operates at ambient temperature, couples readily available simple imines, allenes, and diboranes, and yields high-value homoallylic amines that exhibit versatile amino, alkenyl, and boryl units. PMID:27539673

  2. Amine-Amine Exchange in Aminium-Methanesulfonate Aerosols

    SciTech Connect

    Dawson, Matthew L.; Varner, Mychel E.; Perraud, Veronique M.; Ezell, Michael J.; Wilson, Jacqueline M.; Zelenyuk, Alla; Gerber, Robert B.; Finlayson-Pitts, Barbara J.

    2014-12-18

    Aerosol particles are ubiquitous in the atmosphere and have been shown to impact the Earth’s climate, reduce visibility, and adversely affect human health. Modeling the evolution of aerosol systems requires an understanding of the species and mechanisms involved in particle growth, including the complex interactions between particle- and gas-phase species. Here we report studies of displacement of amines (methylamine, dimethylamine or trimethylamine) in methanesulfonate salt particles by exposure to a different gas-phase amine, using a single particle mass spectrometer, SPLAT II. The variation of the displacement with the nature of the amine suggests that behavior is dependent on water in or on the particles. Small clusters of methanesulfonic acid with amines are used as a model in quantum chemical calculations to identify key structural elements that are expected to influence water uptake, and hence the efficiency of displacement by gas-phase molecules in the aminium salts. Such molecular-level understanding of the processes affecting the ability of gas-phase amines to displace particle-phase aminium species is important for modeling the growth of particles and their impacts in the atmosphere.

  3. Physiological and pathological implications of semicarbazide-sensitive amine oxidase.

    PubMed

    Yu, Peter H; Wright, Shannon; Fan, Ellen H; Lun, Zhao-Rong; Gubisne-Harberle, Diana

    2003-04-11

    Semicarbazide-sensitive amine oxidase (SSAO) catalyzes the deamination of primary amines. Such deamination has been shown capable of regulating glucose transport in adipose cells. It has been independently discovered that the primary structure of vascular adhesion protein-1 (VAP-1) is identical to SSAO. VAP-1 regulates leukocyte migration and is related to inflammation. Increased serum SSAO activities have been found in patients with diabetic mellitus, vascular disorders and Alzheimer's disease. The SSAO-catalyzed deamination of endogenous substrates, that is, methylamine and aminoacetone, led to production of toxic formaldehyde and methylglyoxal, hydrogen peroxide and ammonia, respectively. These highly reactive aldehydes have been shown to initiate protein cross-linkage, exacerbate advanced glycation of proteins and cause endothelial injury. Hydrogen peroxide contributes to oxidative stress. 14C-methylamine is converted to 14C-formaldehyde, which then forms labeled long-lasting protein adduct in rodents. Chronic methylamine treatment increased the excretion of malondialdehyde and microalbuminuria, and enhanced the formation of fatty streaks in C57BL/6 mice fed with an atherogenic diet. Treatment with selective SSAO inhibitor reduces atherogenesis in KKAy diabetic mice fed with high-cholesterol diet. Aminoguanidine, which blocks advanced glycation and reduces nephropathy in animals, is in fact more potent at inhibiting SSAO than its effect on glycation. It suggests that SSAO is involved in vascular disorders under certain pathological conditions. Although SSAO has been known for several decades, its physiological and pathological implications are just beginning to be recognized.

  4. What Is Crystalline Silica?

    MedlinePlus

    ... silica, and requires a repirator protection program until engineering controls are implemented. Additionally, OSHA has a National ... silica materials with safer substitutes, whenever possible. ■ Provide engineering or administrative controls, where feasible, such as local ...

  5. Bacterial degradation of monocyclic aromatic amines

    PubMed Central

    Arora, Pankaj K.

    2015-01-01

    Aromatic amines are an important group of industrial chemicals, which are widely used for manufacturing of dyes, pesticides, drugs, pigments, and other industrial products. These compounds have been considered highly toxic to human beings due to their carcinogenic nature. Three groups of aromatic amines have been recognized: monocyclic, polycyclic, and heterocyclic aromatic amines. Bacterial degradation of several monocyclic aromatic amines has been studied in a variety of bacteria, which utilizes monocyclic aromatic amines as their sole source of carbon and energy. Several degradation pathways have been proposed and the related enzymes and genes have also been characterized. Many reviews have been reviewed toxicity of monocyclic aromatic amines; however, there is lack of review on biodegradation of monocyclic aromatic amines. The aim of this review is to summarize bacterial degradation of monocyclic aromatic amines. This review will increase our current understanding of biochemical and molecular basis of bacterial degradation of monocyclic aromatic amines. PMID:26347719

  6. Silica extraction from geothermal water

    DOEpatents

    Bourcier, William L; Bruton, Carol J

    2014-09-23

    A method of producing silica from geothermal fluid containing low concentration of the silica of less than 275 ppm includes the steps of treating the geothermal fluid containing the silica by reverse osmosis treatment thereby producing a concentrated fluid containing the silica, seasoning the concentrated fluid thereby producing a slurry having precipitated colloids containing the silica, and separating the silica from the slurry.

  7. Amine Swingbed Payload Project Management

    NASA Technical Reports Server (NTRS)

    Hayley, Elizabeth; Curley, Su; Walsh, Mary

    2011-01-01

    The International Space Station (ISS) has been designed as a laboratory for demonstrating technologies in a microgravity environment, benefitting exploration programs by reducing the overall risk of implementing such technologies in new spacecraft. At the beginning of fiscal year 2010, the ISS program manager requested that the amine-based, pressure-swing carbon dioxide and humidity absorption technology (designed by Hamilton Sundstrand, baselined for the ORION Multi-Purpose Crew Vehicle, and tested at the Johnson Space Center in relevant environments, including with humans, since 2005) be developed into a payload for ISS Utilization. In addition to evaluating the amine technology in a flight environment before the first launch of the ORION vehicle, the ISS program wanted to determine the capability of the amine technology to remove carbon dioxide from the ISS cabin environment at the metabolic rate of the full 6-person crew. Because the amine technology vents the absorbed carbon dioxide and water vapor to space vacuum (open loop), additional hardware needed to be developed to minimize the amount of air and water resources lost overboard. Additionally, the payload system would be launched on two separate Space Shuttle flights, with the heart of the payload the swingbed unit itself launching a full year before the remainder of the payload. This paper discusses the project management and challenges of developing the amine swingbed payload in order to accomplish the technology objectives of both the open-loop ORION application as well as the closed-loop ISS application.

  8. Amine Swingbed Payload Project Management

    NASA Technical Reports Server (NTRS)

    Walsch, Mary; Curley, Su

    2013-01-01

    The International Space Station (ISS) has been designed as a laboratory for demonstrating technologies in a microgravity environment, benefitting exploration programs by reducing the overall risk of implementing such technologies in new spacecraft. At the beginning of fiscal year 2010, the ISS program manager requested that the amine-based, pressure-swing carbon dioxide and humidity absorption technology (designed by Hamilton Sundstrand, baselined for the Orion Multi-Purpose Crew Vehicle, and tested at the Johnson Space Center in relevant environments, including with humans, since 2005) be developed into a payload for ISS Utilization. In addition to evaluating the amine technology in a flight environment before the first launch of the Orion vehicle, the ISS program wanted to determine the capability of the amine technology to remove carbon dioxide from the ISS cabin environment at the metabolic rate of the full 6 ]person crew. Because the amine technology vents the absorbed carbon dioxide and water vapor to space vacuum (open loop), additional hardware needed to be developed to minimize the amount of air and water resources lost overboard. Additionally, the payload system would be launched on two separate Space Shuttle flights, with the heart of the payload-the swingbed unit itself-launching a full year before the remainder of the payload. This paper discusses the project management and challenges of developing the amine swingbed payload in order to accomplish the technology objectives of both the open -loop Orion application as well as the closed-loop ISS application.

  9. Mechanistic study of the radical SAM-dependent amine dehydrogenation reactions.

    PubMed

    Ji, Xinjian; Liu, Wan-Qiu; Yuan, Shuguang; Yin, Yue; Ding, Wei; Zhang, Qi

    2016-08-18

    The radical SAM enzyme NosL catalyzes the conversion of l-Trp to 3-methyl-2-indolic acid, and this reaction is initiated by the 5'-deoxyadenosyl (dAdo) radical-mediated hydrogen abstraction from the l-Trp amino group. We demonstrate here that when d-Trp was used in the NosL reaction, hydrogen abstraction occurs promiscuously at both the amino group and Cα of d-Trp. These results inspired us to establish the detailed mechanism of l-Trp amine dehydrogenation catalyzed by a NosL mutant, and to engineer a novel radical SAM-dependent l-Tyr amine dehydrogenase from the thiamine biosynthesis enzyme ThiH. PMID:27492649

  10. Paramagnetic titanium(III) and zirconium(III) metallocene complexes as precatalysts for the dehydrocoupling/dehydrogenation of amine-boranes.

    PubMed

    Helten, Holger; Dutta, Barnali; Vance, James R; Sloan, Matthew E; Haddow, Mairi F; Sproules, Stephen; Collison, David; Whittell, George R; Lloyd-Jones, Guy C; Manners, Ian

    2013-01-01

    Complexes of Group 4 metallocenes in the +3 oxidation state and amidoborane or phosphidoborane function as efficient precatalysts for the dehydrocoupling/dehydrogenation of amine-boranes, such as Me(2) NH⋅BH(3). Such Ti(III) -amidoborane complexes are generated in [Cp(2)Ti]-catalyzed amine-borane dehydrocoupling reactions, for which diamagnetic M(II) and M(IV) species have been previously postulated as precatalysts and intermediates. PMID:23197391

  11. In situ synthesis of polysulfides covalently bonded to silica.

    PubMed

    Ossenkamp, Gabriel C; Kemmitt, Tim; Johnston, Jim H

    2002-05-15

    Silanol groups, triple bond SiOH, on the surface of silica were esterified with unsaturated alcohols and long-chain alcohols bearing thiol groups. The modified silicas obtained were used as substrates for a vulcanization-analogous reaction with sulfur catalyzed by zinc dimethyldithiocarbamate. Surface-esterified thiols could be smoothly converted to bridged polysulfides bonded to the silica surface, whereas the use of surface-esterified unsaturated alcohols led to removal of the surface-esterified alcohol from the silica surface. The materials were characterized by solid-state NMR and thermal and microanalytical analysis. The linking of surface-esterified alkenols and thiols by sulfide bridges was investigated by a numerical model for a flat surface. This showed that for a typical density of 3-4 micromol/m(2) surface groups, a statistical maximum of 70-75% of groups could be linked by S(n) bridges (n=2-4). PMID:16290622

  12. Enzyme-controlled nitrogen-atom transfer enables regiodivergent C-H amination.

    PubMed

    Hyster, Todd K; Farwell, Christopher C; Buller, Andrew R; McIntosh, John A; Arnold, Frances H

    2014-11-01

    We recently demonstrated that variants of cytochrome P450BM3 (CYP102A1) catalyze the insertion of nitrogen species into benzylic C-H bonds to form new C-N bonds. An outstanding challenge in the field of C-H amination is catalyst-controlled regioselectivity. Here, we report two engineered variants of P450BM3 that provide divergent regioselectivity for C-H amination-one favoring amination of benzylic C-H bonds and the other favoring homo-benzylic C-H bonds. The two variants provide nearly identical kinetic isotope effect values (2.8-3.0), suggesting that C-H abstraction is rate-limiting. The 2.66-Å crystal structure of the most active enzyme suggests that the engineered active site can preorganize the substrate for reactivity. We hypothesize that the enzyme controls regioselectivity through localization of a single C-H bond close to the iron nitrenoid.

  13. Sodium Perborate Oxidation of an Aromatic Amine

    ERIC Educational Resources Information Center

    Juestis, Laurence

    1977-01-01

    Describes an experiment involving the oxidation of aromatic primary amines to the corresponding azo compound; suggests procedures for studying factors that influence the yield of such a reaction, including the choice of solvent and the oxidant-amine ratio. (MLH)

  14. Polymorphisms for aromatic amine metabolism in humans: relevance for human carcinogenesis.

    PubMed Central

    Kadlubar, F F; Butler, M A; Kaderlik, K R; Chou, H C; Lang, N P

    1992-01-01

    The metabolic pathways associated with carcinogenic aromatic amines in humans provide an excellent example of polymorphisms that appear to be relevant to human carcinogenesis. In this regard, the N-acetylation of arylamines and the O-acetylation of their N-hydroxy metabolites are catalyzed preferentially by a genetically polymorphic acetyltransferase, high activity of which has been correlated with decreased risk for urinary bladder cancer and increased susceptibility to colorectal cancer. Cytochrome P450IA2, the principal liver enzyme involved in aromatic amine N-oxidation, exhibits a wide interindividual variation that appears trimodal in several populations and is clearly inducible by cigarette smoking and probably other host factors as well. UDP-Glucuronosyltransferases, which catalyze the N-glucuronidation of N-hydroxyarylamines and are likely to be responsible for their transport to the colon, show widely varied but unimodal distributions in humans. In contrast, human liver sulfotransferase activity for N-hydroxyarylamines, which would be expected to decrease their transport through the circulation, is catalyzed by a polymorphic enzyme(s) that is expressed at higher levels in blacks, as compared to whites, and could contribute to their relatively lower incidence of urinary bladder cancer. Peroxidative activation of aromatic amines can also occur, especially from prostaglandin H synthase in the urinary bladder and myeloperoxidase in the lungs of cigarette smokers, and both show considerable individual variability, apparently due to the extent of tissue inflammation.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1486865

  15. Reductive trapping of substrate to bovine plasma amine oxidase

    SciTech Connect

    Hartmann, C.; Klinman, J.P.

    1987-01-25

    Plasma amine oxidases catalyze the oxidative deamination of amines to aldehydes, followed by a 2e- reduction of O/sub 2/ to H/sub 2/O/sub 2/. Pyrroloquinoline quinone (PQQ), previously believed to be restricted to prokaryotes, has recently been proposed to be the cofactor undergoing reduction in the first half-reaction of bovine plasma amine oxidase (Ameyama, M., Hayashi, U., Matsushita, K., Shinagawa, E., and Adachi, O. (1984) Agric. Biol. Chem. 48, 561-565; Lobenstein-Verbeek, C. L., Jongejan, J. A., Frank, J., and Duine, J. A. (1984) FEBS Lett. 170, 305-309). This result is unexpected, since model studies with PQQ implicate Schiff's base formation between a reactive carbonyl and substrates, whereas experiments with bovine plasma amine oxidase have failed to provide evidence for a carbonyl cofactor. We have, therefore, re-examined putative adducts between substrate and enzyme-bound cofactor, employing a combination of (/sup 14/C)benzylamine and (/sup 3/H)NaCNBH/sub 3/. The use of the relatively weak reductant, NaCNBH/sub 3/, affords Schiff's base specificity and permits the study of enzyme below pH 7.0. As we show, enzyme can only be inactivated by NaCNBH/sub 3/ in the presence of substrate, leading to the incorporation of 1 mol of (/sup 14/C)benzylamine/mol of enzyme subunit at complete inactivation. By contrast, we are unable to detect any labeling with (/sup 3/H)NaCNBH/sub 3/, analogous to an earlier study with (/sup 3/H)NaCNBH/sub 4/ (Suva, R. H., and Abeles, R. H. (1978) Biochemistry 17, 3538-3545). We conclude, first, that our inability to obtain adducts containing both carbon 14 and tritium rules out the reductive trapping either of amine substrate with pyridoxal phosphate or of aldehyde product with a lysyl side chain and, second, that the observed pattern of labeling is fully consistent with the presence of PQQ at the active site of bovine plasma amine oxidase.

  16. Atmospheric amines - Part I. A review

    NASA Astrophysics Data System (ADS)

    Ge, Xinlei; Wexler, Anthony S.; Clegg, Simon L.

    2011-01-01

    Amines are emitted by a wide range of sources and are ubiquitous atmospheric organic bases. Approximately 150 amines and about 30 amino acids have been identified in the atmosphere. We review the present knowledge of atmospherically relevant amines with respect to their sources, fluxes, and dynamics including gas-phase reactions, gas-to-particle conversion and deposition. The health effects of aliphatic and aromatic amines are briefly summarized as well as the atmospheric occurrence and reactivity of amino acids and urea.

  17. Mechanism of isomerization of 11-cis-retinal in lipid dispersions by aromatic amines

    SciTech Connect

    Fulton, B.S.; Rando, R.R.

    1987-01-13

    It has previously been shown that retinotoxic, primary aromatic amines catalyze the isomerization of 11-cis-retinal to its all-trans congener after Schiff base formation. This process led to the short-circuiting of the visual cycle and the observed retinotoxicity when it occurred in vivo. The catalysis was also observed to occur in vitro in phosphatidylcholine-based vesicles but not in hydrocarbon solutions. The rate of isomerization of an aromatic amine Schiff base of 11-cis-retinal in the phospholipid vesicles was typically 10/sup 3/-fold more rapid than in hydrocarbon solutions. In this article, the mechanistic basis of this apparently membrane-specific catalysis is described. It was found that the rate enhancement effect observed was independent of the lipid used. Moreover, a bilayer structure was not important because rate enhancements were also observed in micelles. The rapid isomerization rates observed in lipid dispersions appear not be free radical initiated because free radical quenching agents, such as ..cap alpha..-tocopherol and BETA-carotene, had little effect on the isomerization rates. It was further found that aliphatic amines, such as n-dodecylamine, could be substituted for the aromatic amines in phospholipid. Finally, and most importantly, it was found that the isomerization of the aromatic amine retinal Schiff bases in phospholipid vesicles was acid-catalyzed. It is concluded that the rate enhancements observed for the isomerization of 11-cis-retinal aromatic amine Schiff bases in lipid dispersions over that in hydrocarbon solvents are due to the occurrence of acid-base catalysis in the former.

  18. Silica Synthesis by Sponges: Unanticipated Molecular Mechanism

    NASA Astrophysics Data System (ADS)

    Morse, D. E.; Weaver, J. C.

    2001-12-01

    Oceanic diatoms, sponges and other organisms synthesize gigatons per year of silica from silicic acid, ultimately obtained from the weathering of rock. This biogenic silica exhibits a remarkable diversity of structures, many of which reveal a precision of nanoarchitectural control that exceeds the capabilities of human engineering. In contrast to the conditions of anthropogenic and industrial manufacture, the biological synthesis of silica occurs under mild physiological conditions of low temperatures and pressures and near-neutral pH. In addition to the differentiation between biological and abiotic processes governing silica formation, the biomolecular mechanisms controlling synthesis of these materials may offer insights for the development of new, environmentally benign routes for synthesis of nanostructurally controlled silicas and high-performance polysiloxane composites. We found that the needle-like silica spicules made by the marine sponge, Tethya aurantia, each contain an occluded axial filament of protein composed predominantly of repeating assemblies of three similar subunits we named "silicateins." To our surprise, analysis of the purified protein subunits and the cloned silicatein DNAs revealed that the silicateins are highly homologous to a family of hydrolytic enzymes. As predicted from this finding, we discovered that the silicatein filaments are more than simple, passive templates; they actively catalyze and spatially direct polycondensation to form silica, (as well as the phenyl- and methyl-silsesquioxane) from the corresponding silicon alkoxides at neutral pH and low temperature. Catalytic activity also is exhibited by the silicatein subunits obtained by disaggregation of the protein filaments and those produced from recombinant DNA templates cloned in bacteria. This catalytic activity accelerates the rate-limiting hydrolysis of the silicon alkoxide precursors. Genetic engineering, used to produce variants of the silicatein molecule with

  19. Quinone-Catalyzed Selective Oxidation of Organic Molecules.

    PubMed

    Wendlandt, Alison E; Stahl, Shannon S

    2015-12-01

    Quinones are common stoichiometric reagents in organic chemistry. Para-quinones with high reduction potentials, such as DDQ and chloranil, are widely used and typically promote hydride abstraction. In recent years, many catalytic applications of these methods have been achieved by using transition metals, electrochemistry, or O2 to regenerate the oxidized quinone in situ. Complementary studies have led to the development of a different class of quinones that resemble the ortho-quinone cofactors in copper amine oxidases and mediate the efficient and selective aerobic and/or electrochemical dehydrogenation of amines. The latter reactions typically proceed by electrophilic transamination and/or addition-elimination reaction mechanisms, rather than hydride abstraction pathways. The collective observations show that the quinone structure has a significant influence on the reaction mechanism and has important implications for the development of new quinone reagents and quinone-catalyzed transformations. PMID:26530485

  20. Silica nanoparticles grown and stabilized in organic nonalcoholic media.

    PubMed

    El Hawi, Nancy; Nayral, Céline; Delpech, Fabien; Coppel, Yannick; Cornejo, Alfonso; Castel, Annie; Chaudret, Bruno

    2009-07-01

    This work features an alternative approach to the well-documented preparation of silica nanoparticles in protic media. We present here the one-pot synthesis of silica nanoparticles of adjustable size (between 18 and 174 nm), prepared and stabilized in organic nonalcoholic solvents. This novel route is based on hydrolysis and condensation of tetraethoxysilane, using water as reactant and different primary amines (butylamine, octylamine, dodecylamine, hexadecylamine) as catalysts in tetrahydrofuran or dimethoxyethane. The growth rate can be finely adjusted, and the first stages of the formation are observed by transmission electronic microscopy, revealing a silicated network in which the silica particles are formed and then released in solution. The amine plays not only a catalyst role but is also implied, as well as the solvent, in the stabilization process and the size control of the particles. A detailed NMR study demonstrates a core-shell structure in which the silica core is surrounded by a layer of alkylammonium ions together with solvent. PMID:19496545

  1. Hydroxycruciforms: amine-responsive fluorophores.

    PubMed

    McGrier, Psaras L; Solntsev, Kyril M; Miao, Shaobin; Tolbert, Laren M; Miranda, Oscar R; Rotello, Vincent M; Bunz, Uwe H F

    2008-01-01

    The synthesis of three hydroxy-substituted cruciforms (XF, 1,4-bis(4'-hydroxystyryl)-2,5-bis(4''-methoxyphenylethynyl)benzene, 1,4-bis(4'-methoxystyryl)-2,5-bis(4''-hydroxyphenylethynyl)benzene, and 1,4-bis(4'-hydroxystyryl)-2,5-bis(4''-hydroxyphenylethynyl)benzene) starts with a Horner reaction followed by a Sonogashira coupling and subsequent deprotection. The three herein described XFs contain either two or four free phenolic hydroxyl groups. All three XFs were subjected to photometric UV/Vis titrations in a methanol/water mixture. The respective pK(a) values were obtained by data deconvolution. As the three XFs display a significant change in emission color upon photoinduced deprotonation, the XFs were taken up in different solvents and exposed to twelve amines. The amine-dependent change in emissivity of the tetrahydroxy XF is sufficiently distinct in the eight solvents that all of the inspected amines are discerned by a linear discriminant analysis. The tetrahydroxy XF in different solvents forms a sensor array, the response of which is based on the excited-state proton transfer (ESPT) to amines and mediated by the choice of the battery of solvents that are utilized.

  2. Catalyzed sodium chlorate candles

    NASA Technical Reports Server (NTRS)

    Malich, C. W.; Wydeven, T.

    1972-01-01

    The catalytic effect of cobalt powder on chlorate decomposition has been confirmed. Catalysis is enhanced by oxidation of the metal during burning. Catalysts other than cobalt compounds should also be effective; the complete elimination of fuel has shown that the oxidation of cobalt during decomposition is not a vital factor in the improved performance of catalyzed candles.

  3. Silica-Ceria Hybrid Nanostructures

    SciTech Connect

    Munusamy, Prabhakaran; Sanghavi, Shail P.; Nachimuthu, Ponnusamy; Baer, Donald R.; Thevuthasan, Suntharampillai

    2012-04-25

    A new hybrid material system that consists of ceria attached silica nanoparticles has been developed. Because of the versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and antioxidant properties of ceria nanoparticles, this material system is ideally suited for biomedical applications. The silica particles of size ~50nm were synthesized by the Stöber synthesis method and ceria nanoparticles of size ~2-3nm was attached to the silica surface using a hetrocoagulation method. The presence of silanol groups on the surface of silica particles mediated homogenous nucleation of ceria which were attached to silica surface by Si-O-Ce bonding. The formations of silica-ceria hybrid nanostructures were characterized by X-photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM). The HRTEM image confirms the formation of individual crystallites of ceria nanoparticles attached to the silica surface. The XPS analysis indicates that ceria nanoparticles are chemically bonded to surface of silica and possess mixture of +3 and +4 chemical states.

  4. Pt-Catalyzed Synthesis of Functionalized Symmetrical and Unsymmetrical Disilazanes.

    PubMed

    Kuciński, Krzysztof; Szudkowska-Frątczak, Justyna; Hreczycho, Grzegorz

    2016-09-01

    In nearly every total synthesis, silylating agents are employed in synthetic steps to protect sensitive functional groups. A Pt-catalyzed hydrosilylation of various unsaturated substrates to prepare novel symmetrical and unsymmetrical disilazanes is described. The developed synthetic methodology is widely applicable and tolerates all manner of functional groups (e.g., amines, ethers, esters, halogens, silanes, etc.). To demonstrate the value of the described method, mono-substituted 1,1,3,3-tetramethyldisilazanes were further selectively converted to completely new unsymmetrical derivatives. PMID:27414042

  5. Urea- and Thiourea-Catalyzed Aminolysis of Carbonates.

    PubMed

    Blain, Marine; Yau, Honman; Jean-Gérard, Ludivine; Auvergne, Rémi; Benazet, Dominique; Schreiner, Peter R; Caillol, Sylvain; Andrioletti, Bruno

    2016-08-23

    The aminolysis of (poly)carbonates by (poly)amines provides access to non-isocyanate polyurethanes (NIPUs) that are toxic-reagent-free analogues of polyurethanes (PUs). Owing to their low reactivity, the ring opening of cyclic carbonates requires the use of a catalyst. Herein, we report that the more available and cheaper ureas could advantageously be used for catalyzing the formation of NIPUs at the expense of the thiourea analogues. In addition, we demonstrate a medium-range pKa of the (thio)urea and an unqeual substitution pattern is critical for controlling the efficiency of the carbonate opening. PMID:27467779

  6. Synthesis of Dihydrobenzofurans via Palladium-Catalyzed Heteroannulations

    SciTech Connect

    Roman Vladimirovich Rozhkov

    2004-12-19

    Palladium-catalyzed heteroannulation of 1,3-dienes with 3-iodo-2-alkenols, and 2-iodo-2-alkenols, as well as their amino analogs, affords the corresponding cyclic ethers and amines respectively. The presence of a {beta}-hydrogen in the vinylic halide results in {beta}-hydride elimination giving the corresponding alkyne. The presence of a bulky group in the {alpha}-position of the vinylic halide results in failure or reduced amounts of annulation products. A chloride source, pyridine base and electron-rich phosphine are essential for this reaction.

  7. New modes for the osmium-catalyzed oxidative cyclization.

    PubMed

    Donohoe, Timothy J; Lindsay-Scott, Peter J; Parker, Jeremy S; Callens, Cedric K A

    2010-03-01

    The osmium-catalyzed oxidative cyclization of amino alcohol initiators formally derived from 1,4-dienes is an effective method for the construction of pyrrolidines, utilizing a novel reoxidant (4-nitropyridine N-oxide = NPNO). The cyclization of enantiopure syn- and anti-amino alcohols gives rise to enantiopure cis- and trans-2,5-disubstituted pyrrolidines, respectively. Moreover, the cyclization of bis-homoallylic amines bearing an exocyclic chelating group is shown to be a complementary method for trans-pyrrolidine formation.

  8. Copper-catalyzed stereoselective aminoboration of bicyclic alkenes.

    PubMed

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

    2015-01-01

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

  9. Copper-catalyzed stereoselective aminoboration of bicyclic alkenes.

    PubMed

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

    2015-01-01

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

  10. Lipase-catalyzed aza-Michael reaction on acrylate derivatives.

    PubMed

    Steunenberg, Peter; Sijm, Maarten; Zuilhof, Han; Sanders, Johan P M; Scott, Elinor L; Franssen, Maurice C R

    2013-04-19

    A methodology has been developed for an efficient and selective lipase-catalyzed aza-Michael reaction of various amines (primary and secondary) with a series of acrylates and alkylacrylates. Reaction parameters were tuned, and under the optimal conditions it was found that Pseudomonas stutzeri lipase and Chromobacterium viscosum lipase showed the highest selectivity for the aza-Michael addition to substituted alkyl acrylates. For the first time also, some CLEAs were examined that showed a comparable or higher selectivity and yield than the free enzymes and other formulations.

  11. Interactions of silica surfaces

    SciTech Connect

    Vigil, G.; Xu, Z.; Steinberg, S.; Israelachvili, J. . Dept. of Chemical and Nuclear Engineering and Materials Dept.)

    1994-07-01

    Adhesion, friction, and colloidal forces in air and aqueous salt solutions have been measured between various silica surfaces prepared by depositing amorphous but highly smooth silica films on mica. The results show four interesting and interrelated phenomena: (i) the adhesion of silica surfaces in air increases slowly with contact time, especially in humid air where the contacting surfaces become separated by an [approximately]20-[angstrom]-thick layer of hydrated silica or silica gel; (ii) the friction of two silica surfaces exhibits large sticking or stiction spikes, whose magnitude increases in the presence of water and when the surfaces are kept in contact longer before sliding; (iii) the non-DLVO repulsion commonly seen at short range (<40 A) between silica surfaces immersed in aqueous solutions is monotonically repulsive, with no oscillatory component, and is quite unlike theoretical expectations and previous measurements of forces due to solvent structure; (iv) dynamic contact angle measurements reveal time-dependent effects which cannot be due to a fixed surface chemical heterogeneity or roughness. The results indicate that silica surfaces undergo slow structural and chemical changes during interactions with water and with each other. More specifically, the authors propose that the unusual interfacial and colloidal properties of silica are due, not to hydration effects, but to the presence of an [approximately]10-[angstrom]-thick gel-like layer of protruding silanol and silicilic acid groups that grow on the surfaces in the presence of water. These protruding groups react chemically (sinter) with similar groups located on an opposing surface and give rise to the unusual time-dependent adhesion, friction, and non-DLVO forces observed. The proposed mechanism in terms of a surface layer of silica gel is consistent with the known surface chemistry of silica and accounts for the results reported and for other unusual surface and colloidal properties of silica.

  12. Silica, silicosis, and cancer

    SciTech Connect

    Goldsmith, D.F.; Winn, D.M.; Shy, C.M.

    1986-01-01

    These proceedings collect papers on occupational exposure. Topics include: measurement of silica dust, mortality in granite workers, effects of quartz in coal mine dust, pneumoconiosis, and lung cancer.

  13. Car Parrinello molecular dynamics simulation of base-catalyzed amide hydrolysis in aqueous solution

    NASA Astrophysics Data System (ADS)

    Zahn, Dirk

    2004-01-01

    The base catalyzed hydrolysis of N-methylacetamide is elucidated by means of Car-Parrinello simulation. The process is investigated in aqueous solution, including a quantum treatment of all electronic degrees of freedom. The rate-determining step is the attack of a hydroxide ion on the amide carbon atom. This is followed by protonation of the nitrogen atom. The final dissociation may occur via two different pathways: (i) dissociation into an amine and a carboxylic acid and (ii) oxygen deprotonation and dissociation into an amine and a carboxyl anion. The later pathway was found to be strongly favored.

  14. Facile Access to Ring-Fused Aminals via Direct α-Amination of Secondary Amines with ortho-Aminobenzaldehydes. Synthesis of Vasicine, Deoxyvasicine, Deoxyvasicinone, Mackinazolinone and Ruteacarpine

    PubMed Central

    Richers, Matthew T.; Deb, Indubhusan; Platonova, Alena Yu.; Zhang, Chen

    2013-01-01

    Secondary amines undergo redox-neutral reactions with aminobenzaldehydes under conventional and microwave heating to furnish polycyclic aminals via amine α-amination/N-alkylation. This unique α-functionalization reaction proceeds without the involvement of transition metals or other additives. The resulting aminal products are precursors for various quinazolinone alkaloids and their analogues. PMID:24052668

  15. O-Acetyl Oximes as Transformable Directing Groups for Pd-Catalyzed C–H Bond Functionalization

    PubMed Central

    Neufeldt, Sharon R.; Sanford, Melanie S.

    2010-01-01

    O-Acetyl oximes serve as effective directing groups for Pd-catalyzed sp2 and sp3 C–H functionalization reactions. The C–H functionalization products can be subsequently transformed into ortho- or β-functionalized ketones, alcohols, amines, and heterocycles. PMID:20041702

  16. Tritium catalyzed deuterium tokamaks

    SciTech Connect

    Greenspan, E.; Miley, G.H.; Jung, J.; Gilligan, J.

    1984-04-01

    A preliminary assessment of the promise of the Tritium Catalyzed Deuterium (TCD) tokamak power reactors relative to that of deuterium-tritium (D-T) and catalyzed deuterium (Cat-D) tokamaks is undertaken. The TCD mode of operation is arrived at by converting the /sup 3/He from the D(D,n)/sup 3/He reaction into tritium, by neutron capture in the blanket; the tritium thus produced is fed into the plasma. There are three main parts to the assessment: blanket study, reactor design and economic analysis and an assessment of the prospects for improvements in the performance of TCD reactors (and in the promise of the TCD mode of operation, in general).

  17. Asymmetric synthesis of 2,3-dihydropyrroles by ring-opening/cyclization of cyclopropyl ketones using primary amines.

    PubMed

    Xia, Yong; Liu, Xiaohua; Zheng, Haifeng; Lin, Lili; Feng, Xiaoming

    2015-01-01

    The asymmetric ring-opening/cyclization of cyclopropyl ketones with primary amine nucleophiles was catalyzed by a chiral N,N'-dioxide/scandium(III) complex through a kinetic resolution process. A broad range of cyclopropyl ketones and primary amines are suitable substrates of this reaction. The corresponding products were afforded in excellent enantioselectivities and yields (up to 97 % ee and 98 % yield) under mild reaction conditions. This method provides a promising access to chiral 2,3-dihydropyrroles as well as an effective procedure for the kinetic resolution of 2-substituted cyclopropyl ketones.

  18. Enzyme-Inspired Axially Chiral Pyridoxamines Armed with a Cooperative Lateral Amine Chain for Enantioselective Biomimetic Transamination.

    PubMed

    Liu, Yong Ethan; Lu, Zhaole; Li, Bo; Tian, Jiaxin; Liu, Feng; Zhao, Junyu; Hou, Chengkang; Li, Yingkun; Niu, Lili; Zhao, Baoguo

    2016-08-31

    Enzymatic transamination is catalyzed by pyridoxal/pyridoxamine, and it involves remarkable cooperative catalysis of a Lys residue in the transaminase. Inspired by transaminases, we developed a class of axially chiral pyridoxamines 11 bearing a lateral amine arm. The pyridoxamines exhibited high catalytic activity and excellent enantioselectivity in asymmetric transamination of α-keto acids, to give various α-amino acids in 67-99% yields with 83-94% ee's. The lateral amine arm likely participates in cooperative catalysis as the Lys residue does in biological transamination and has an important impact on the transamination in terms of activity and enantioselectivity. PMID:27515275

  19. Catalytic C(sp(3) )-H Arylation of Free Primary Amines with an exo Directing Group Generated In Situ.

    PubMed

    Xu, Yan; Young, Michael C; Wang, Chengpeng; Magness, David M; Dong, Guangbin

    2016-07-25

    Herein, we report the palladium-catalyzed direct arylation of unactivated aliphatic C-H bonds in free primary amines. This method takes advantage of an exo-imine-type directing group (DG) that can be generated and removed in situ. A range of unprotected aliphatic amines are suitable substrates, undergoing site-selective arylation at the γ-position. Methyl as well as cyclic and acyclic methylene groups can be activated. Furthermore, when aniline-derived substrates were used, preliminary success with δ-C-H arylation was achieved. The feasibility of using the DG component in a catalytic fashion was also demonstrated. PMID:27276342

  20. Silica, Silicosis, and Autoimmunity

    PubMed Central

    Pollard, Kenneth Michael

    2016-01-01

    Inhalation of dust containing crystalline silica is associated with a number of acute and chronic diseases including systemic autoimmune diseases. Evidence for the link with autoimmune disease comes from epidemiological studies linking occupational exposure to crystalline silica dust with the systemic autoimmune diseases systemic lupus erythematosus, systemic sclerosis, and rheumatoid arthritis. Although little is known regarding the mechanism by which silica exposure leads to systemic autoimmune disease, there is a voluminous literature on silica exposure and silicosis that may help identify immune processes that precede development of autoimmunity. The pathophysiology of silicosis consists of deposition of silica particles in the alveoli of the lung. Ingestion of these particles by macrophages initiates an inflammatory response, which stimulates fibroblasts to proliferate and produce collagen. Silica particles are encased by collagen leading to fibrosis and the nodular lesions characteristic of the disease. The steps in the development of silicosis, including acute and chronic inflammation and fibrosis, have different molecular and cellular requirements, suggesting that silica-induced inflammation and fibrosis may be mechanistically separate. Significantly, it is unclear whether silica-induced inflammation and fibrosis contribute similarly to the development of autoimmunity. Nonetheless, the findings from human and animal model studies are consistent with an autoimmune pathogenesis that begins with activation of the innate immune system leading to proinflammatory cytokine production, pulmonary inflammation leading to activation of adaptive immunity, breaking of tolerance, and autoantibodies and tissue damage. The variable frequency of these immunological features following silica exposure suggests substantial genetic involvement and gene/environment interaction in silica-induced autoimmunity. However, numerous questions remain unanswered. PMID:27014276

  1. Insights into caerulomycin A biosynthesis: a two-component monooxygenase CrmH-catalyzed oxime formation.

    PubMed

    Zhu, Yiguang; Zhang, Qingbo; Li, Sumei; Lin, Qinheng; Fu, Peng; Zhang, Guangtao; Zhang, Haibo; Shi, Rong; Zhu, Weiming; Zhang, Changsheng

    2013-12-18

    The immunosuppressive agent caerulomycin A features a unique 2,2'-bipyridine core structure and an unusual oxime functionality. Genetic and biochemical evidence confirms that the oxime formation in caerulomycin A biosynthesis is catalyzed by CrmH, a flavin-dependent two-component monooxygenase that is compatible with multiple flavin reductases, from a primary amine via a N-hydroxylamine intermediate. Structure homologue-guided site-directed mutagenesis studies identify four amino acid residues that are essential for CrmH catalysis. This study provides the first biochemical evidence of a two-component monooxygenase that catalyzes oxime formation.

  2. Direct formation of S-nitroso silica nanoparticles from a single silica source.

    PubMed

    Chou, Hung-Chang; Chiu, Shih-Jiuan; Liu, Ying-Ling; Hu, Teh-Min

    2014-01-28

    Nitric oxide (NO) is a ubiquitous molecule in the body. Because of its multiple pathophysiologic roles, the potential for treating various diseases by the exogenous administration of NO has been under intensive investigation. However, the unstable, radical nature of NO poses a major challenge to the effective delivery of NO. Previously, silica nanoparticles synthesized by the traditional method have been developed into NO-carrying systems. In the present study, for the first time NO-carrying silica nanoparticles were prepared from a single silica precursor using a simple nanoprecipitation method. (3-Mercaptopropyl)-trimethoxysilane (MPTMS) was used as the sole silane source, which was subjected to acid-catalyzed S-nitrosation and condensation reactions in a one-pot organic phase. S-Nitroso silica nanoparticles (SNO-SiNPs) were then produced by injecting a smaller quantity of the organic phase into a larger amount of water without surfactants. Various preparation parameters were tested to obtain optimized conditions. Moreover, a phase diagram demonstrating the ouzo effect was constructed. The prepared SNO-SiNPs were spherical particles with a tunable size in the range of 100-400 nm. The nanoparticles in aqueous dispersions exhibited high colloid stability, possibly resulting from highly negatively charged surfaces. The result of solid-state (29)Si NMR shows the predominance of T(2) and T(3) silicon structures, suggesting that nanoparticles were formed from polycondensed silica species. In conclusion, NO-loaded silica nanoparticles have been directly prepared from a single silane precursor using a surfactant-free, low-energy, one-step nanoprecipitation approach. The method precludes the need for the initial formation of bare particles and subsequent functionalization steps. PMID:24410024

  3. Mild Metal-Free Hydrosilylation of Secondary Amides to Amines.

    PubMed

    Huang, Pei-Qiang; Lang, Qi-Wei; Wang, Yan-Rong

    2016-05-20

    The combination of amide activation by Tf2O with B(C6F5)3-catalyzed hydrosilylation with TMDS constitutes a method for the one-pot reduction of secondary amides to amines under mild conditions. The method displays a broad applicability for the reduction of many types of substrates, and shows good compatibility and excellent chemoselectivity for many sensitive functional groups. Reductions of a multifunctionalized α,β-unsaturated amide obtained from another synthetic methodology, and a C-H functionalization product produced the corresponding amines in good to excellent yield. Chemoselective reduction of enantiomeric pure (ee >99%) tetrahydro-5-oxo-2-furaneamides yielded 5-(aminomethyl)dihydrofuran-2(3H)-ones in a racemization-free manner. The latter were converted in one pot to N-protected 5-hydroxypiperidin-2-ones, which are building blocks for the synthesis of many natural products. Further elaboration of an intermediate led to a concise four-step synthesis of (-)-epi-pseudoconhydrine. PMID:27100232

  4. Biogenic amines in seafood: a review.

    PubMed

    Biji, K B; Ravishankar, C N; Venkateswarlu, R; Mohan, C O; Gopal, T K Srinivasa

    2016-05-01

    The biogenic amines are low molecular weight organic bases present normally in the body with biological activity influencing important physiological functions. The physiological functions of these molecules are achieved by very low concentrations in the tissues. However, significantly high amounts of biogenic amines are produced during processing and storage of seafood as a result of microbial contamination and inadequate storage conditions. Microorganisms having decarboxylase enzyme activity convert amino acids to their respective biogenic amines. Biogenic amines in seafood have been implicated as a major causative agent of food borne illness, where intoxication results from the ingestion of foods containing higher amount of biogenic amines. Hence its identification, quantitation and awareness of this food borne toxin are important in relation to food safety and spoilage. The aim of this paper is to review the basic concepts of seafood quality and safety in relation to biogenic amines along with its control measures and future areas for research. PMID:27407186

  5. Supported polytertiary amines: highly efficient and selective SO2 adsorbents.

    PubMed

    Tailor, Ritesh; Abboud, Mohamed; Sayari, Abdelhamid

    2014-01-01

    Tertiary amine containing poly(propyleneimine) second (G2) and third (G3) generation dendrimers as well as polyethyleneimine (PEI) were developed for the selective removal of SO2. N-Alkylation of primary and secondary amines into tertiary amines was confirmed by FTIR and NMR analysis. Such modified polyamines were impregnated on two nanoporous supports, namely, SBA-15PL silica with platelet morphology and ethanol-extracted pore-expanded MCM-41 (PME) composite. In the presence of 0.1% SO2/N2 at 23 °C, the uptake of modified PEI, G2, and G3 supported on SBA-15PL was 2.07, 2.35, and 1.71 mmol/g, respectively; corresponding to SO2/N ratios of 0.22, 0.4, and 0.3. Under the same conditions, the SO2 adsorption capacity of PME-supported modified PEI and G3 was significantly higher, reaching 4.68 and 4.34 mmol/g, corresponding to SO2/N ratios of 0.41 and 0.82, respectively. The working SO2 adsorption capacity decreased with increasing temperature, reflecting the exothermic nature of the process. The adsorption capacity of these materials was enhanced dramatically in the presence of humidity in the gas mixture. FTIR data before SO2 adsorption and after adsorption and regeneration did not indicate any change in the materials. Nonetheless, the SO2 working capacity decreased in consecutive adsorption/regeneration cycles due to evaporation of impregnated polyamines, rather than actual deactivation. FTIR and (13)C and (15)N CP-MAS NMR of fresh and SO2 adsorbed modified G3 on PME confirmed the formation of a complexation adduct.

  6. Supported polytertiary amines: highly efficient and selective SO2 adsorbents.

    PubMed

    Tailor, Ritesh; Abboud, Mohamed; Sayari, Abdelhamid

    2014-01-01

    Tertiary amine containing poly(propyleneimine) second (G2) and third (G3) generation dendrimers as well as polyethyleneimine (PEI) were developed for the selective removal of SO2. N-Alkylation of primary and secondary amines into tertiary amines was confirmed by FTIR and NMR analysis. Such modified polyamines were impregnated on two nanoporous supports, namely, SBA-15PL silica with platelet morphology and ethanol-extracted pore-expanded MCM-41 (PME) composite. In the presence of 0.1% SO2/N2 at 23 °C, the uptake of modified PEI, G2, and G3 supported on SBA-15PL was 2.07, 2.35, and 1.71 mmol/g, respectively; corresponding to SO2/N ratios of 0.22, 0.4, and 0.3. Under the same conditions, the SO2 adsorption capacity of PME-supported modified PEI and G3 was significantly higher, reaching 4.68 and 4.34 mmol/g, corresponding to SO2/N ratios of 0.41 and 0.82, respectively. The working SO2 adsorption capacity decreased with increasing temperature, reflecting the exothermic nature of the process. The adsorption capacity of these materials was enhanced dramatically in the presence of humidity in the gas mixture. FTIR data before SO2 adsorption and after adsorption and regeneration did not indicate any change in the materials. Nonetheless, the SO2 working capacity decreased in consecutive adsorption/regeneration cycles due to evaporation of impregnated polyamines, rather than actual deactivation. FTIR and (13)C and (15)N CP-MAS NMR of fresh and SO2 adsorbed modified G3 on PME confirmed the formation of a complexation adduct. PMID:24437448

  7. High Resolution, Single-Step Patterning of Silica Aerogels

    NASA Technical Reports Server (NTRS)

    Bertino, M. F.; Hund, J. F.; Sosa, J.; Zhang, G.; Sotiriou-Leventis, C.; Leventis, N.; Tokuhiro, A. T.; Terry, J.

    2003-01-01

    Three-dimensional metallic structures are fabricated with high spatial resolution in silica aerogels. In our method, silica hydrogels are prepared with a standard base-catalyzed route, and exchanged with an aqueous solution typically containing Ag' ions (1 M) and 2-propanol (0.2 M). The metal ions are reduced photolytically with a table-top ultraviolet lamp, or radiolytically, with a focused X-ray beam. We fabricated dots and lines as small as 30 x 70 km, protruding for several mm into the bulk of the materials. The hydrogels are eventually supercritically dried to yield aerogels, without any measurable change in the shape and spatial resolution of the lithographed structures. Transmission electron microscopy shows that illuminated regions are composed of Ag clusters with a size of several pm, separated by thin layers of silica.

  8. Controlled release of chlorhexidine from amorphous microporous silica.

    PubMed

    Verraedt, E; Pendela, M; Adams, E; Hoogmartens, J; Martens, J A

    2010-02-25

    A new system for the controlled release of the antiseptic chlorhexidine is presented. Amorphous microporous silica (AMS) excipient material was synthesized via an acid catalyzed sol-gel method and shaped as powder or coating. Chlorhexidine diacetate was introduced into the pores of the AMS silica via the incipient wetness impregnation method. This silica reservoir maintained a slow release of chlorhexidine over more than 7days. Chlorhexidine release was controlled by configurational diffusion in the AMS pores having free diameters of less than 1nm. The release of chlorhexidine was fine tuned by adapting particle size and pore diameter. Controlled release of chlorhexidine from an AMS coating on silicon wafer was demonstrated. PMID:19804804

  9. Catalyzed Ceramic Burner Material

    SciTech Connect

    Barnes, Amy S., Dr.

    2012-06-29

    Catalyzed combustion offers the advantages of increased fuel efficiency, decreased emissions (both NOx and CO), and an expanded operating range. These performance improvements are related to the ability of the catalyst to stabilize a flame at or within the burner media and to combust fuel at much lower temperatures. This technology has a diverse set of applications in industrial and commercial heating, including boilers for the paper, food and chemical industries. However, wide spread adoption of catalyzed combustion has been limited by the high cost of precious metals needed for the catalyst materials. The primary objective of this project was the development of an innovative catalyzed burner media for commercial and small industrial boiler applications that drastically reduce the unit cost of the catalyzed media without sacrificing the benefits associated with catalyzed combustion. The scope of this program was to identify both the optimum substrate material as well as the best performing catalyst construction to meet or exceed industry standards for durability, cost, energy efficiency, and emissions. It was anticipated that commercial implementation of this technology would result in significant energy savings and reduced emissions. Based on demonstrated achievements, there is a potential to reduce NOx emissions by 40,000 TPY and natural gas consumption by 8.9 TBtu in industries that heavily utilize natural gas for process heating. These industries include food manufacturing, polymer processing, and pulp and paper manufacturing. Initial evaluation of commercial solutions and upcoming EPA regulations suggests that small to midsized boilers in industrial and commercial markets could possibly see the greatest benefit from this technology. While out of scope for the current program, an extension of this technology could also be applied to catalytic oxidation for volatile organic compounds (VOCs). Considerable progress has been made over the course of the grant

  10. Immobilization and stabilization of cephalosporin C acylase on aminated support by crosslinking with glutaraldehyde and further modifying with aminated macromolecules.

    PubMed

    He, Hua; Wei, Yanmei; Luo, Hui; Li, Xi; Wang, Xiaona; Liang, Chen; Chang, Yanhong; Yu, Huimin; Shen, Zhongyao

    2015-01-01

    In this work, cephalosporin C acylase (CA), a heterodimeric enzyme of industrial potential in direct hydrolysis of cephalosporin C (CPC) to 7-aminocephalosporanic acid (7-ACA), was covalently immobilized on the aminated support LX1000-HA (HA) with two different protocols. The stability of CA adsorbed onto the HA support followed by crosslinking with glutaraldehyde (HA-CA-glut) was better than that of the CA covalently immobilized on the glutaraldehyde preactivated HA support (HA-glut-CA). The thermostabilization factors (compared with the free enzyme) of these two immobilized enzymes were 11.2-fold and 2.2-fold, respectively. In order to improve the stability of HA-CA-glut, a novel strategy based on postimmobilization modifying with aminated molecules was developed to take advantage of the glutaraldehyde moieties left on the enzyme and support. The macromolecules, such as polyethyleneimine (PEI) and chitosan, had larger effects than small molecules on the thermal stability of the immobilized enzyme perhaps due to crosslinking of the enzymes and support with each other. The quaternary structure of the CA could be much stabilized by this novel approach including physical adsorption on aminated support, glutaraldehyde treatment, and macromolecule modification. The HA-CA-glut-PEI20000 (the HA-CA-glut postmodified with PEI Mw = 20,000) had a thermostabilization factor of 20-fold, and its substrate affinity (Km = 14.3 mM) was better than that of HA-CA-glut (Km = 33.4 mM). The half-life of the immobilized enzymes HA-CA-glut-PEI20000 under the CPC-catalyzing conditions could reach 28 cycles, a higher value than that of HA-CA-glut (21 cycles).

  11. 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

  12. Palladium-catalyzed synthesis of N-arylated carbazoles using anilines and cyclic diaryliodonium salts

    PubMed Central

    Riedmüller, Stefan

    2013-01-01

    Summary The direct synthesis of N-arylated carbazoles through a palladium-catalyzed amination of cyclic iodonium salts with anilines is described. In particular, electron-poor aniline derivatives reacted smoothly with only 5 mol % of Pd(OAc)2 as catalyst to give the desired products in up to 71% yield. Furthermore, the reactivity of cyclic iodonium salts is compared with the reactivity of the corresponding cyclic bromonium analogues. PMID:23843915

  13. Synthesis of Cyclic Peptidomimetics via a Pd-Catalyzed Macroamination Reaction.

    PubMed

    Hopkins, Brett A; Smith, Graham F; Sciammetta, Nunzio

    2016-08-19

    A new method to access cyclic peptidomimetics via a Pd-catalyzed macroamination reaction is presented. Natural amino acid amines are revealed as proficient coupling partners in these transformations. With a commercially available CPhos G3 catalyst system and substrates bearing diverse amino acid and aryl halide backbones, the unique head to side-chain (or side-chain mimic) macrocycles are afforded with ring sizes from 11 to 23 members in yields up to 84%. PMID:27508926

  14. 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.

  15. Copper-catalyzed oxidative Heck reactions between alkyltrifluoroborates and vinyl arenes.

    PubMed

    Liwosz, Timothy W; Chemler, Sherry R

    2013-06-21

    We report herein that potassium alkyltrifluoroborates can be utilized in oxidative Heck-type reactions with vinyl arenes. The reaction is catalyzed by a Cu(OTf)2/1,10-phenanthroline with MnO2 as the stoichiometric oxidant. In addition to the alkyl Heck, amination, esterification, and dimerization reactions of alkyltrifluoroborates are demonstrated under analogous reaction conditions. Evidence for an alkyl radical intermediate is presented. PMID:23734764

  16. Silica Embedded Metal Hydrides

    SciTech Connect

    Heung, L.K.; Wicks, G.G.

    1998-08-01

    A method to produce silica embedded metal hydride was developed. The product is a composite in which metal hydride particles are embedded in a matrix of silica. The silica matrix is highly porous. Hydrogen gas can easily reach the embedded metal hydride particles. The pores are small so that the metal hydride particles cannot leave the matrix. The porous matrix also protects the metal hydride particles from larger and reactive molecules such as oxygen, since the larger gas molecules cannot pass through the small pores easily. Tests show that granules of this composite can absorb hydrogen readily and withstand many cycles without making fines.

  17. Iodine-catalyzed aminosulfonation of hydrocarbons by imidoiodinanes. A synthetic and mechanistic investigation.

    PubMed

    Lamar, Angus A; Nicholas, Kenneth M

    2010-11-19

    The amino-functionalization of a range of benzylic and some aliphatic saturated and unsaturated hydrocarbons by reaction with imido-iodinanes (PhI═NSO2Ar) is catalyzed by I2 under operationally simple and mild conditions. The first examples of 1,2-functionalization of unactivated C-H bonds using imido-iodinanes as aminating agents are reported. Mechanistic investigations, including Hammett analysis, kinetic isotope effects, a cyclopropane clock experiment, and stereoselectivity tests, are indicative of a stepwise pathway in C-N bond formation. Investigation into the nature of the active aminating species has led to the isolation of a novel aminating agent formulated as (ArSO2N)(x)I(y) (x = 1, y = 2; or x = 3, y = 4). PMID:20977281

  18. Formation of hollow silica nanospheres by reverse microemulsion

    NASA Astrophysics Data System (ADS)

    Lin, Cheng-Han; Chang, Jen-Hsuan; Yeh, Yi-Qi; Wu, Si-Han; Liu, Yi-Hsin; Mou, Chung-Yuan

    2015-05-01

    Uniform hollow silica nanospheres (HSNs) synthesized with reverse microemulsion have great application potential as nanoreactors because enzymes or nanocatalysts can be easily encapsulated de novo in synthesis. Water-in-oil (w/o) reverse microemulsions comprising the polymeric surfactant polyoxyethylene (5) isooctylphenyl ether (Igepal CA-520), ammonia and water in a continuous oil phase (alkanes) coalesce into size-tunable silica nanoparticles via diffusion aggregation after the introduction of silica precursors. Here, we elucidate in detail the growth mechanism for silica nanoparticles via nucleation of ammonium-catalyzed silica oligomers from tetraethylorthosilicate (TEOS) and nanoporous aminopropyltrimethoxy silane (APTS) in the reverse microemulsion system. The formation pathway was studied in situ with small-angle X-ray scattering (SAXS). We find a four-stage process showing a sigmoidal growth behavior in time with a crossover from the induction period, early nucleation stage, coalescence growth and a final slowing down of growth. Various characterizations (TEM, N2 isotherm, dynamic light scattering, zeta potential, NMR, elemental analysis) reveal the diameters, scattering length density (SLD), mesoporosity, surface potentials and chemical compositions of the HSNs. Oil phases of alkanes with different alkyl chains are systematically employed to tune the sizes of HSNs by varying oil molar volumes, co-solvent amounts or surfactant mixture ratios. Silica condensation is incomplete in the core region, with the silica source of TEOS and APTS leading to the hollow silica nanosphere after etching with warm water.Uniform hollow silica nanospheres (HSNs) synthesized with reverse microemulsion have great application potential as nanoreactors because enzymes or nanocatalysts can be easily encapsulated de novo in synthesis. Water-in-oil (w/o) reverse microemulsions comprising the polymeric surfactant polyoxyethylene (5) isooctylphenyl ether (Igepal CA-520), ammonia and

  19. Surface arming magnetic nanoparticles with amine N-halamines as recyclable antibacterial agents: Construction and evaluation.

    PubMed

    Yao, Quanfu; Gao, Yangyang; Gao, Tianyi; Zhang, Yanling; Harnoode, Chokto; Dong, Alideertu; Liu, Ying; Xiao, Linghan

    2016-08-01

    Magnetic recyclable antibacterial nanomaterials, i.e., magnetic amine N-halamine nanoparticles (Fe3O4@SiO2/CTMP NPs), were constructed by arming magnetic silica nanoparticles (Fe3O4@SiO2 NPs) with amine N-halamine (CTMP). Magnetic iron oxide nanoparticles were encapsulated into silica layers followed by anchoring antibacterial amine N-halamines to give magnetic/antibacterial bi-functional agents with core-shell structure. Since the presence of Fe3O4 NPs in core, the products offer super-paramagnetic behavior, which made them separable magnetically after the antibacterial behavior. Their sterilizing effect on bacterial strain was evaluated using Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) as model bacteria via the plate counting technique, zone of inhibition study, and time kill assay. Antibacterial mechanism study illustrated that the products integrate both the contact mechanism and the release mechanism for attacking bacteria. The significant effect of oxidative chlorine content and concentration of the products on antibiotic action were confirmed. Thanks to the magnetic property, the potential recyclability of the products was achieved. Most significantly, the products retain effective antibacterial action even after five cycles. These findings revealed that the products Fe3O4@SiO2/CTMP NPs have promising applications in the antibacterial fields. PMID:27108209

  20. Supermicroporous alumina-silica zinc oxides

    SciTech Connect

    Shpeizer, Boris G; Bakhmutov, Vladimir I; Clearfield, Abraham

    2008-09-29

    A new family of porous mixed oxides with pores largely in the 8-20 {angstrom} range have been prepared. TEOS acts as a solvent and as a source of silica to which aluminum butoxide and transition metal acetates are added. Neutral amines are added as templates and to effect hydrolysis. This paper describes the ZnO-Al{sub 2}O{sub 5}-SiO{sub 2} system but similar results have been obtained with other transition metal oxides. An interesting feature of the technique is that the larger the amine template the greater is the surface area of the mixed oxide with only a slight increase in the average pore diameter. Both NMR and atomic pair distribution functional methods have been used to prove the homogeneity of the mixed oxide products. This preparative method complements our earlier report in Chemical Communications on mixed oxides prepared with ZrO{sub 2} and TiO{sub 2} incorporating transition metal oxides.

  1. Hordeum vulgare Seedlings Amine Oxidase

    PubMed Central

    Cogoni, Antonina; Piras, Carla; Farci, Raffaele; Melis, Antonello; Floris, Giovanni

    1990-01-01

    Although no amine oxidase could be detected in crude extracts, the enzyme has been purified to apparent homogeneity from Hordeum vulgare seedlings using ammonium sulfate precipitation and chromatography on DEAE cellulose, Hydroxylapatite, and Sephadex G200 columns. Gel filtration experiments indicate a molecular weight of about 150,000. The pH optimum of the enzyme was found to be 7.5 in potassium phosphate buffer. The spectrum of ultraviolet and visible regions were similar to Cuamine oxidase from Leguminosae. PMID:16667542

  2. Electrochemical Sensors: Functionalized Silica

    SciTech Connect

    Fryxell, Glen E.; Lin, Yuehe; Yantasee, Wassana

    2009-03-24

    This chapter summarizes recent devellopment of electrochemical sensors based on functionlized mesoporous silica materials. The nanomatrials based sensors have been developed for sensitive and selective enrironmental detection of toxic heavy metal and uranium ions.

  3. Silicification and biosilicification: The role of macromolecules in bioinspired silica synthesis

    NASA Astrophysics Data System (ADS)

    Patwardhan, Siddharth Vijay

    Diatoms, sponges and grasses are all known to produce ornate biogenic silica structures under ambient conditions. Some aspects of the molecular mechanism controlling biosilicification have recently been elucidated. The entrapment of the catalyzing/templating/scaffolding biomacromolecules enables them to be recovered by selective dissolution of biosilica. The proteins extracted from the diatom Cylindrotheca fusiformis (silaffins) and the sponge Tethya aurantia (silicateins) have been shown to precipitate silica from silica precursors in vitro. The identification of synthetic macromolecules that can act as catalysts/templates/scaffolds for silica formation gives exciting possibilities for bioinspired silica synthesis. Herein, the role of various synthetic (bio)macromolecules in silicification is studied. Attempts have also been made to understand the mechanism(s) governing (bio)macromolecule mediated (bio)silicification. Furthermore, the results and the understanding gained from various synthetic systems are used to demonstrate the potential of such bioinspired routes to develop new materials.

  4. High residue contents indebted by platinum and silica synergistic action during the pyrolysis of silicone formulations.

    PubMed

    Delebecq, Etienne; Hamdani-Devarennes, Siska; Raeke, Julia; Lopez Cuesta, José-Marie; Ganachaud, François

    2011-03-01

    The synergistic role of platinum and silica as a way to increase the final residue of pyrolized silicone was investigated and explained, giving new interpretations. Conditions were first set to study the thermal degradation of silicones in the presence of platinum based on the simplest silicone/silica/platinum formulation. Numerous parameters, e.g., platinum and silica content or silica surface modifications, were varied to track their influences on the final residues. A thorough DSC study, together with SEM/EDX and Pyrolysis/GC-MS analyses, led us to propose a three-stage process. The key parameter governing thermal stability and final content of the residue is the conjugated actions of immobilizing/cross-linking PDMS chains. Silica particles tether silicone chains through physical interactions, i.e., hydrogen bonding, facilitating a platinum radically catalyzed cross-linking reaction. Practical implications and possible improvements on LSR formulations are finally given.

  5. Crystalline Silica Primer

    USGS Publications Warehouse

    ,

    1992-01-01

    substance and will present a nontechnical overview of the techniques used to measure crystalline silica. Because this primer is meant to be a starting point for anyone interested in learning more about crystalline silica, a list of selected readings and other resources is included. The detailed glossary, which defines many terms that are beyond the scope of this publication, is designed to help the reader move from this presentation to a more technical one, the inevitable next step.

  6. The mechanism of carbon dioxide catalysis in the hydrogen peroxide N-oxidation of amines.

    PubMed

    Balagam, Bharathi; Richardson, David E

    2008-02-01

    The reactivity of the peroxymonocarbonate ion, HCO4- (an active oxidant derived from the equilibrium reaction of hydrogen peroxide and bicarbonate), has been investigated in the oxidation of aliphatic amines. Tertiary aliphatic amines are oxidized to the corresponding N-oxides in high yields, while secondary amines give corresponding nitrones. A closely related mechanism for the H2O2 oxidation of tertiary amines catalyzed by CO2 (under 1 atm) and H2O2 at 25 degrees C is proposed. The rate laws for the oxidation of N-methylmorpholine (1) to N-methylmorpholine N-oxide and N,N-dimethylbenzylamine (2) to N,N-dimethylbenzylamine N-oxide have been obtained. The second-order rate constants for the oxidation by HCO4- are k1 .016 M(-1) s(-1) for 1 in water and k1=0.042 M(-1) s(-1) for 2 in water/acetone (5:1). The second-order rate constants for tertiary amine oxidations by HCO4- are over 400-fold greater than those for H2O2 alone. Activation parameters for oxidation of 1 by HCO4- in water are reported (DeltaH=36+/-2 kJ mol(-1) and DeltaS=-154+/-7 J mol(-1) K(-1)). The BAP (NH4HCO3-activated peroxide) or CO2/H2O2 oxidation reagents are simple and economical methods for the preparation of tertiary amine N-oxides. The reactions proceed to completion, do not require extraction, and afford the pure N-oxides in excellent yields in aqueous media.

  7. Probing Intramolecular versus Intermolecular CO2 Adsorption on Amine-Grafted SBA-15.

    PubMed

    Yoo, Chun-Jae; Lee, Li-Chen; Jones, Christopher W

    2015-12-15

    A mesoporous silica SBA-15 is modified with an array of amine-containing organosilanes including (i) propylamine, SiCH2CH2CH2NH2 (MONO), (ii) propylethylenediamine, SiCH2CH2CH2NHCH2CH2NH2 (DI), (iii) propyldiethylenetriamine, SiCH2CH2CH2NHCH2CH2NHCH2CH2NH2 (TRI), and (iv) propyltriethylenetetramine, SiCH2CH2CH2NHCH2CH2N(CH2CH2NH2)2 (TREN) and the low loading silane adsorbents (∼0.45 mmol silane/g) are evaluated for their CO2 adsorption properties, with a focus on gaining insight into the propensity for intramolecular vs intermolecular CO2 adsorption. Adsorption isotherms at low CO2 coverages are measured while simultaneously recording the heat evolved via a Tian-Calvet calorimeter. The results are compared on a silane molecule efficiency basis (mol CO2 adsorbed/mol silane) to assess the potential for intramolecular CO2 adsorption, employing two amine groups in a single silane molecule. As the number of amines in the silane molecule increases (MONO < DI < TREN ∼ TRI), the silane molecule efficiency is enhanced owing to the ability to intramolecularly capture CO2. Analysis of the CO2 uptake for samples with the surface silanols removed by capping demonstrates that cooperative uptake due to amine-CO2-silanol interactions is also possible over these adsorbents and is the primary mode of sorption for the MONO material at the studied low silane loading. As the propensity for intramolecular CO2 capture increases due to the presence of multiple amines in a single silane molecule (MONO < DI < TREN ∼ TRI), the measured heat of adsorption also increases. This study of various amine-containing silanes at low coverage is the first to provide significant, direct evidence for intramolecular CO2 capture in a single silane molecule. Furthermore, it provides evidence for the relative heats of adsorption for physisorption on a silanol laden surface (ca. 37 kJ/mol), a silanol-capped surface (ca. 25 kJ/mol), via amine-CO2-silanol interactions (ca. 46 kJ/mol), and via amine-CO2

  8. Silica, hybrid silica, hydride silica and non-silica stationary phases for liquid chromatography.

    PubMed

    Borges, Endler M

    2015-04-01

    Free silanols on the surface of silica are the "villains", which are responsible for detrimental interactions of those compounds and the stationary phase (i.e., bad peak shape, low efficiency) as well as low thermal and chemical stability. For these reasons, we began this review describing new silica and hybrid silica stationary phases, which have reduced and/or shielded silanols. At present, in liquid chromatography for the majority of analyses, reversed-phase liquid chromatography is the separation mode of choice. However, the needs for increased selectivity and increased retention of hydrophilic bases have substantially increased the interest in hydrophilic interaction chromatography (HILIC). Therefore, stationary phases and this mode of separation are discussed. Then, non-silica stationary phases (i.e., zirconium oxide, titanium oxide, alumina and porous graphitized carbon), which afford increased thermal and chemical stability and also selectivity different from those obtained with silica and hybrid silica, are discussed. In addition, the use of these materials in HILIC is also reviewed.

  9. Facile fabrication of organic-inorganic hybrid beads by aminated alginate enabled gelation and biomimetic mineralization.

    PubMed

    Li, Jian; Wu, Hong; Liang, Yanpeng; Jiang, Zhongyi; Jiang, Yanjun; Zhang, Lei

    2013-01-01

    Inspired by biomineralization, design and preparation of biomimetic organic-inorganic composites have become a hot issue and a research frontier in many areas, including enzyme engineering. In this research, a unique and facile method for fabricating organic-inorganic hybrid beads is proposed. Modified alginate with a dual function of gelation and mineralization was synthesized for fabrication of hybrid carriers for enzyme immobilization. With the aid of EDC/NHS conjugation chemistry, the amine groups from diethylene triamine were grafted onto alginate in a controllable way. The resultant aminated alginate served manifold functions: forming a hydrogel via Ca(2+)-cross-linking, inducing the biomimetic silicification and manipulating the distribution of silica nanoparticles. Owing to the compact polymer network structure and the homogeneous silica nanoparticle dispersion, the as-prepared NH2-alginate/silica hybrid beads displayed superior swelling resistance and mechanical stability to pure alginate beads. The hybrid beads were subsequently utilized for encapsulation of yeast alcohol dehydrogenase (YADH). It was found that the thermal stability, pH tolerance and storage stability of the immobilized enzyme were all improved without significantly lowering the catalytic activity.

  10. Chemoselective amination of propargylic C(sp³)-H bonds by cobalt(II)-based metalloradical catalysis.

    PubMed

    Lu, Hongjian; Li, Chaoqun; Jiang, Huiling; Lizardi, Christopher L; Zhang, X Peter

    2014-07-01

    Highly chemoselective intramolecular amination of propargylic C(sp(3))-H bonds has been demonstrated for N-bishomopropargylic sulfamoyl azides through cobalt(II)-based metalloradical catalysis. Supported by D(2h)-symmetric amidoporphyrin ligand 3,5-Di(t)Bu-IbuPhyrin, the cobalt(II)-catalyzed C-H amination proceeds effectively under neutral and nonoxidative conditions without the need of any additives, and generates N2 as the only byproduct. The metalloradical amination is suitable for both secondary and tertiary propargylic C-H substrates with an unusually high degree of functional-group tolerance, thus providing a direct method for high-yielding synthesis of functionalized propargylamine derivatives.

  11. Speaking Personally--with Amin Qazi

    ERIC Educational Resources Information Center

    Ragan, Lawrence

    2016-01-01

    This article provides an interview with Amin Quazi, the founding chief executive officer of Unizin, a university-owned consortium focused on the emerging digital teaching and learning ecosystem. Amin has a bachelor's degree in chemical engineering from The University of Iowa and a master's degree in business administration from the Carlson School…

  12. Multifunctional antireflection coatings based on novel hollow silica-silica nanocomposites.

    PubMed

    Zhang, Xianpeng; Lan, Pinjun; Lu, Yuehui; Li, Jia; Xu, Hua; Zhang, Jing; Lee, YoungPak; Rhee, Joo Yull; Choy, Kwang-Leong; Song, Weijie

    2014-02-12

    Antireflection (AR) coatings that exhibit multifunctional characteristics, including high transparency, robust resistance to moisture, high hardness, and antifogging properties, were developed based on hollow silica-silica nanocomposites. These novel nanocomposite coatings with a closed-pore structure, consisting of hollow silica nanospheres (HSNs) infiltrated with an acid-catalyzed silica sol (ACSS), were fabricated using a low-cost sol-gel dip-coating method. The refractive index of the nanocomposite coatings was tailored by controlling the amount of ACSS infiltrated into the HSNs during synthesis. Photovoltaic transmittance (TPV) values of 96.86-97.34% were obtained over a broad range of wavelengths, from 300 to 1200 nm; these values were close to the theoretical limit for a lossy single-layered AR coating (97.72%). The nanocomposite coatings displayed a stable TPV, with degradation values of less than 4% and 0.1% after highly accelerated temperature and humidity stress tests, and abrasion tests, respectively. In addition, the nanocomposite coatings had a hardness of approximately 1.6 GPa, while the porous silica coatings with an open-pore structure showed more severe degradation and had a lower hardness. The void fraction and surface roughness of the nanocomposite coatings could be controlled, which gave rise to near-superhydrophilic and antifogging characteristics. The promising results obtained in this study suggest that the nanocomposite coatings have the potential to be of benefit for the design, fabrication, and development of multifunctional AR coatings with both omnidirectional broadband transmission and long-term durability that are required for demanding outdoor applications in energy harvesting and optical instrumentation in extreme climates or humid conditions.

  13. Amine Measurements in Boreal Forest Air

    NASA Astrophysics Data System (ADS)

    Hemmilä, Marja; Hellén, Heidi; Makkonen, Ulla; Hakola, Hannele

    2015-04-01

    Amines are reactive, volatile bases in the air with a general formula of RNH2, R2NH or R3N. Especially small amines can stabilize sulphuric acid clusters and hence affect nucleation. Amines react rapidly with hydroxyl radical (OH˙) thus affecting oxidative capacity of the atmosphere. The amine concentrations are higher in forest air than in urban air (Hellén et al., 2014), but the sources are not known. In order to get more information concerning amine sources, we conducted a measurement campaign in a boreal forest. At SMEAR II station at Hyytiälä, Southern Finland (61°510'N, 24°170'E, 180 m a.s.l.) The measurements cover seven months, from June to December 2014. For sampling and measuring we used MARGA (The instrument for Measuring AeRosols and Gases in Ambient air) which is an on-line ion chromatograph (IC) connected to a sampling system. The IC component of the MARGA system was coupled to an electrospray ionization quadrupole mass spectrometer (MS) to improve sensitivity of amine measurements. This new set-up enabled amine concentration measurements in ambient air both in aerosol and gas phases with a time resolution of only 1 hour. With MARGA-MS we analysed 7 different amines: monomethylamine (MMA), dimethylamine (DMA), trimethylamine (TMA), ethylamine (EA), diethylamine (DEA), propylamine (PA) and butylamine (BA). In preliminary data-analysis we found out, that in June and July most of the measured amines were in gas phase, and particle phase amine concentrations were mostly under detection limits (<1.7 pptv). In June the gaseous amine concentrations were higher than in July. The measured concentrations of gaseous amines followed temperature variation, which could indicate that amines are produced and emitted from the environment or re-emitted from the surfaces as temperature rises after deposition during night-time. All measured amines had similar diurnal variation with maxima during afternoon and minima during night. Results from other months will also

  14. 15N NMR investigation of the covalent binding of reduced TNT amines to soil humic acid, model compounds, and lignocellulose

    USGS Publications Warehouse

    Thorn, K.A.; Kennedy, K.R.

    2002-01-01

    The five major reductive degradation products of TNT-4ADNT (4-amino-2,6-dinitrotoluene), 2ADNT (2-amino-4,6-dinitrotoluene), 2,4DANT (2,4-diamino-6-nitrotoluene), 2,6DANT (2,6-diamino-4-nitrotoluene), and TAT (2,4,6-triaminotoluene)-labeled with 15N in the amine positions, were reacted with the IHSS soil humic acid and analyzed by 15N NMR spectrometry. In the absence of catalysts, all five amines underwent nucleophilic addition reactions with quinone and other carbonyl groups in the soil humic acid to form both heterocyclic and nonheterocyclic condensation products. Imine formation via 1,2-addition of the amines to quinone groups in the soil humic acid was significant with the diamines and TAT but not the monoamines. Horseradish peroxidase (HRP) catalyzed an increase in the incorporation of all five amines into the humic acid. In the case of the diamines and TAT, HRP also shifted the binding away from heterocyclic condensation product toward imine formation. A comparison of quantitative liquid phase with solid-state CP/MAS 15N NMR indicated that the CP experiment underestimated imine and heterocyclic nitrogens in humic acid, even with contact times optimal for observation of these nitrogens. Covalent binding of the mono- and diamines to 4-methylcatechol, the HRP catalyzed condensation of 4ADNT and 2,4DANT to coniferyl alcohol, and the binding of 2,4DANT to lignocellulose with and without birnessite were also examined.

  15. Hydroxide-catalyzed bonding

    NASA Technical Reports Server (NTRS)

    Gwo, Dz-Hung (Inventor)

    2003-01-01

    A method of bonding substrates by hydroxide-catalyzed hydration/dehydration involves applying a bonding material to at least one surface to be bonded, and placing the at least one surface sufficiently close to another surface such that a bonding interface is formed between them. A bonding material of the invention comprises a source of hydroxide ions, and may optionally include a silicate component, a particulate filling material, and a property-modifying component. Bonding methods of the invention reliably and reproducibly provide bonds which are strong and precise, and which may be tailored according to a wide range of possible applications. Possible applications for bonding materials of the invention include: forming composite materials, coating substrates, forming laminate structures, assembly of precision optical components, and preparing objects of defined geometry and composition. Bonding materials and methods of preparing the same are also disclosed.

  16. Preparation of monodispersed vinylpyridine-divinylbenzene porous copolymer resins and their application to high-performance liquid chromatographic separation of aromatic amines.

    PubMed

    Kitahara, Kei-Ichi; Okuya, Shuji; Yoshihama, Isao; Hanada, Takako; Nagashima, Kunio; Arai, Sadao

    2009-10-30

    For the separation of aromatic amines, two types of monodispersed porous polymer resins were prepared by the copolymerization of 2-vinylpyridine and 4-vinylpyridine with divinylbenzene in the presence of template silica gel particles (particle size 5 microm), followed by dissolution of the template silica gel in an alkaline solution. The transmission electron micrographs and the scanning electron micrograph revealed that these templated polymer resins have a spherical morphology with a good monodispersity and porous structure. Using these monodispersed polymer resins, the high-performance liquid chromatographic separation of aromatic amines in the mobile phases of pHs 2.0, 2.9, 4.1, 7.2 and 11.7 were carried out. The 2-vinylpyridine-divinylbenzene copolymer resins showed slightly stronger retentions for aromatic amines than the 4-vinylpyridine-divinylbenzene copolymer resins. Under acidic conditions (around pH 2.0), aniline and the toluidines showed no retention on these copolymer resins due to the repulsion between the cationic forms of these amines and pyridinium cations in the stationary phase, whereas less basic aromatic amines or non-basic acetanilide showed slight retentions. Above pH 4.1, the separation of aromatic amines with these polymer resins showed a typical reversed-phase mode separation. Therefore, the separation patterns of aromatic amines are effectively tunable by changing the pH value of the mobile phases. A good separation of eight aromatic amines was achieved at pH 2.9 using the 2-vinylpyridine-divinylbenzene copolymer resins. PMID:19442983

  17. Mutants of 4-oxalocrotonate tautomerase catalyze the decarboxylation of oxaloacetate through an imine mechanism.

    PubMed

    Brik, Ashraf; D'Souza, Lawrence J; Keinan, Ehud; Grynszpan, Flavio; Dawson, Philip E

    2002-09-01

    A designed single amino acid substitution can alter the catalytic activity and mechanism of 4-oxalocrotonate tautomerase (4-OT). While the wild-type enzyme catalyzes only the tautomerization of oxalocrotonate, the Pro1Ala mutant (P1A) catalyzes two reactions--the original tautomerization reaction and the decarboxylation of oxaloacetate. Although the N-terminal amine group of P1A is involved in both reactions, our results support a nucleophilic mechanism for the decarboxylase activity, in contrast to the general acid/base mechanism that has been previously established for the tautomerase activity. These findings demonstrate that a single catalytic group in a 4-OT mutant can catalyze two reactions by two different mechanisms.

  18. Kinetics of silica polymerization

    SciTech Connect

    Weres, O.; Yee, A.; Tsao, L.

    1980-05-01

    The polymerization of silicic acid in geothermal brine-like aqueous solutions to produce amorphous silica in colloidal form has been studied experimentally and theoretically. A large amount of high quality experimental data has been generated over the temperature rang 23 to 100{sup 0}C. Wide ranges of dissolved silica concentration, pH, and sodium chloride concentration were covered. The catalytic effects of fluoride and the reaction inhibiting effects of aluminum and boron were studied also. Two basic processes have been separately studied: the formation of new colloidal particles by the homogeneous nucleation process and the deposition of dissolved silica on pre-existing colloidal particles. A rigorous theory of the formation of colloidal particles of amorphous silica by homogeneous nucleation was developed. This theory employs the Lothe-Pound formalism, and is embodied in the computer code SILNUC which quantitatively models the homogeneous nucleation and growth of colloidal silica particles in more than enough detail for practical application. The theory and code were extensively used in planning the experimental work and analyzing the data produced. The code is now complete and running in its final form. It is capable of reproducing most of the experimental results to within experimental error. It is also capable of extrapolation to experimentally inaccessible conditions, i.e., high temperatures, rapidly varying temperature and pH, etc.

  19. Quantifying amine permeation sources with acid neutralization: calibrations and amines measured in coastal and continental atmospheres

    NASA Astrophysics Data System (ADS)

    Freshour, N. A.; Carlson, K. K.; Melka, Y. A.; Hinz, S.; Panta, B.; Hanson, D. R.

    2014-04-01

    An acid titration method for quantifying amine permeation rates was used to calibrate an Ambient pressure Proton transfer Mass Spectrometer (AmPMS) that monitors ambient amine compounds. The method involves capturing amines entrained in a N2 flow by bubbling it through an acidified solution (~ 10-5 M HCl), and the amines are quantified via changes in solution pH with time. Home-made permeation tubes had permeation rates (typically tens of pmol s-1) that depended on the type of amine and tubing and on temperature. Calibrations of AmPMS yielded sensitivities for ammonia, methyl amine, dimethyl amine, and trimethyl amine that are close to the sensitivity assuming a gas-kinetic, ion-molecule rate coefficient. The permeation tubes were also designed to deliver a reproducible amount of amine to a flow reactor where nucleation with sulfuric acid was studied. The high proton affinity compound dimethyl sulfoxide (DMSO), linked to oceanic environments, was also studied and AmPMS is highly sensitive to it. AmPMS was deployed recently in two field campaigns and mixing ratios are reported for ammonia, alkyl amines, and DMSO and correlations between these species and with particle formation events are discussed.

  20. Investigation into the role of silica in lithium polysulfide adsorption for lithium sulfur battery

    SciTech Connect

    Kim, Miso; Kang, Sung-Hwan; Manuel, James; Zhao, Xiaohui; Cho, Kwon Koo; Ahn, Jou Hyeon

    2015-09-15

    Highlights: • Amine functionalized silica nanoparticles (AFSN) were prepared. • Polysulfide adsorption studies were carried out with silica nanoparticles and AFSN. • Sulfur cathodes were prepared with SN and AFSN for Li–S batteries. • AFSN showed excellent polysulfide adsorption. - Abstract: A new type of sulfur electrodes with the ability for polysulfide adsorption was prepared by incorporating silica nanoparticles (SN) or amine functionalized silica nanoparticles (AFSN). AFSN was synthesized by a simple and cost-effective method. The functionalization and surface morphology of silica were confirmed with Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM), respectively. Polysulfide adsorption studies were carried out using UV–vis spectrometer, which confirmed the excellent adsorption of polysulfides by AFSN. Interaction of polysulfides with SN or AFSN was studied using FTIR and FT-Raman spectroscopy. The effective polysulfide adsorption by SN and AFSN leads to good and stable cycle performance of lithium sulfur cells. The results show that the incorporation of SN or AFSN with sulfur is a promising method to prepare cathode material for lithium sulfur batteries.

  1. Simultaneous structure-activity studies and arming of natural products by C–H amination reveal cellular targets of eupalmerin acetate

    PubMed Central

    Li, Jing; Cisar, Justin S.; Zhou, Congying; Vera, Brunilda; Williams, Howard; Rodríguez, Abimael D.; Cravatt, Benjamin F.; Romo, Daniel

    2014-01-01

    To fully exploit the inherent and enduring potential of natural products for fundamental cell biology and drug lead discovery, synthetic methods for functionalizing unique sites are highly desirable. Here we describe a strategy for the derivatization of natural products at ‘unfunctionalized’ positions via Rh(II)-catalyzed amination enabling simultaneous structure-activity relationship (SAR) studies and arming (alkynylation) of natural products. Employing Du Bois C–H amination, allylic and benzylic C–H bonds underwent amination and olefins underwent aziridination. With tertiary amine-containing natural products, amidines were produced via C–H amination/oxidation and unusual N-aminations provided hydrazine sulfamate inner salts. The alkynylated derivatives are readied for subsequent conjugation to access cellular probes for mechanism of action studies. Both chemo- and site-selectivity was studied by application to a diverse set of natural products including the marine-derived anticancer diterpene, eupalmerin acetate (EPA). Quantitative proteome profiling with an alkynyl EPA derivative obtained by site-selective, allylic C–H amination led to identification of several protein targets in HL-60 cells, including several known to be associated with cancer proliferation, suggestive of a polypharmacological mode of action for EPA. PMID:23695633

  2. C3 vanadium(V) amine triphenolate complexes: vanadium haloperoxidase structural and functional models.

    PubMed

    Mba, Miriam; Pontini, Marta; Lovat, Silvia; Zonta, Cristiano; Bernardinelli, Gerald; Kündig, Peter E; Licini, Giulia

    2008-10-01

    The C 3 vanadium(V) amine triphenolate complex 1f has been characterized as a structural and functional model of vanadium haloperoxidases. The complex catalyzes efficiently sulfoxidations at room temperature using hydrogen peroxide as the terminal oxidant, yielding the corresponding sulfoxides in quantitative yields and high selectivities (catalyst loading down to 0.01%, TONs up to 9900, and TOFs up to 8000 h (-1)) as well as bromination of 1,3,5-trimethoxybenzene (catalyst loading down to 0.05%, TONs up to 1260, and TOFs up to 220 h (-1)).

  3. Practical Iron- and Cobalt-Catalyzed Cross-Coupling Reactions between N-Heterocyclic Halides and Aryl or Heteroaryl Magnesium Reagents.

    PubMed

    Kuzmina, Olesya M; Steib, Andreas K; Fernandez, Sarah; Boudot, Willy; Markiewicz, John T; Knochel, Paul

    2015-05-26

    The reaction scope of iron- and cobalt-catalyzed cross-coupling reactions in the presence of isoquinoline (quinoline) in the solvent mixture tBuOMe/THF has been further investigated. Various 2-halogenated pyridine, pyrimidine, and triazine derivatives were arylated under these mild conditions in excellent yields. The presence of isoquinoline allows us to perform Fe-catalyzed cross-coupling reactions between 6-chloroquinoline and aryl magnesium reagents. Furthermore, it was found that the use of 10% N,N-dimethylquinoline-8-amine increases the yields of some Co-catalyzed cross-coupling reactions with chloropyridines bearing electron-withdrawing substituents. PMID:25899175

  4. Silica in alkaline brines

    USGS Publications Warehouse

    Jones, B.F.; Rettig, S.L.; Eugster, H.P.

    1967-01-01

    Analysis of sodium carbonate-bicarbonate brines from closed basins in volcanic terranes of Oregon and Kenya reveals silica contents of up to 2700 parts per million at pH's higher than 10. These high concentrations of SiO 2 can be attributed to reaction of waters with silicates, and subsequent evaporative concentration accompanied by a rise in pH. Supersaturation with respect to amorphous silica may occur and persist for brines that are out of contact with silicate muds and undersaturated with respect to trona; correlation of SiO2 with concentration of Na and total CO2 support this interpretation. Addition of moredilute waters to alkaline brines may lower the pH and cause inorganic precipitation of substantial amounts of silica.

  5. Cooperative Co(III)/Cu(II)-Catalyzed C-N/N-N Coupling of Imidates with Anthranils: Access to 1H-Indazoles via C-H Activation.

    PubMed

    Li, Lei; Wang, He; Yu, Songjie; Yang, Xifa; Li, Xingwei

    2016-08-01

    Cooperative cobalt- and copper-catalyzed C-H activation of imidate esters and oxidative coupling with anthranils allowed efficient synthesis of 1H-indazoles in the absence of metal oxidants. The anthranil acts as a convenient aminating reagent as well as an organic oxidant in this transformation. The copper catalyst likely functions at the stage of N-N formation. PMID:27415586

  6. Efficient Cu(OTf)2-catalyzed synthesis of novel and diverse 2,3-dihydroquinazolin-4(1H)-ones.

    PubMed

    Zhu, Xiaoyan; Kang, So Rang; Xia, Likai; Lee, Jihye; Basavegowda, Nagaraj; Lee, Yong Rok

    2015-02-01

    An efficient one-pot synthesis of various 2,3-dihydroquinazolin-4(1H)-one derivatives was accomplished using Cu(OTf)2-catalyzed multi-component reactions between isatoic anhydride, ketones, and amines. The method has several significant advantages; mild reaction conditions, easy handling, and efficiency of catalyst. PMID:25403260

  7. Consecutive condensation, C-N and N-N bond formations: a copper- catalyzed one-pot three-component synthesis of 2H-indazole.

    PubMed

    Kumar, Manian Rajesh; Park, Ahbyeol; Park, Namjin; Lee, Sunwoo

    2011-07-01

    2H-Indazoles are synthesized using copper-catalyzed, one-pot, three-component reactions of 2-bromobenzaldehydes, primary amines, and sodium azide. A copper catalyst plays the key role in the formation of C-N and N-N bonds. This method has a broad substrate scope with a high tolerance for a variety of functional groups. PMID:21644532

  8. Amine-Oxide Hybrid Materials for CO2 Capture from Ambient Air.

    PubMed

    Didas, Stephanie A; Choi, Sunho; Chaikittisilp, Watcharop; Jones, Christopher W

    2015-10-20

    Oxide supports functionalized with amine moieties have been used for decades as catalysts and chromatographic media. Owing to the recognized impact of atmospheric CO2 on global climate change, the study of the use of amine-oxide hybrid materials as CO2 sorbents has exploded in the past decade. While the majority of the work has concerned separation of CO2 from dilute mixtures such as flue gas from coal-fired power plants, it has been recognized by us and others that such supported amine materials are also perhaps uniquely suited to extract CO2 from ultradilute gas mixtures, such as ambient air. As unique, low temperature chemisorbents, they can operate under ambient conditions, spontaneously extracting CO2 from ambient air, while being regenerated under mild conditions using heat or the combination of heat and vacuum. This Account describes the evolution of our activities on the design of amine-functionalized silica materials for catalysis to the design, characterization, and utilization of these materials in CO2 separations. New materials developed in our laboratory, such as hyperbranched aminosilica materials, and previously known amine-oxide hybrid compositions, have been extensively studied for CO2 extraction from simulated ambient air (400 ppm of CO2). The role of amine type and structure (molecular, polymeric), support type and structure, the stability of the various compositions under simulated operating conditions, and the nature of the adsorbed CO2 have been investigated in detail. The requirements for an effective, practical air capture process have been outlined and the ability of amine-oxide hybrid materials to meet these needs has been discussed. Ultimately, the practicality of such a "direct air capture" process is predicated not only on the physicochemical properties of the sorbent, but also how the sorbent operates in a practical process that offers a scalable gas-solid contacting strategy. In this regard, the utility of low pressure drop monolith

  9. Amine-Oxide Hybrid Materials for CO2 Capture from Ambient Air.

    PubMed

    Didas, Stephanie A; Choi, Sunho; Chaikittisilp, Watcharop; Jones, Christopher W

    2015-10-20

    Oxide supports functionalized with amine moieties have been used for decades as catalysts and chromatographic media. Owing to the recognized impact of atmospheric CO2 on global climate change, the study of the use of amine-oxide hybrid materials as CO2 sorbents has exploded in the past decade. While the majority of the work has concerned separation of CO2 from dilute mixtures such as flue gas from coal-fired power plants, it has been recognized by us and others that such supported amine materials are also perhaps uniquely suited to extract CO2 from ultradilute gas mixtures, such as ambient air. As unique, low temperature chemisorbents, they can operate under ambient conditions, spontaneously extracting CO2 from ambient air, while being regenerated under mild conditions using heat or the combination of heat and vacuum. This Account describes the evolution of our activities on the design of amine-functionalized silica materials for catalysis to the design, characterization, and utilization of these materials in CO2 separations. New materials developed in our laboratory, such as hyperbranched aminosilica materials, and previously known amine-oxide hybrid compositions, have been extensively studied for CO2 extraction from simulated ambient air (400 ppm of CO2). The role of amine type and structure (molecular, polymeric), support type and structure, the stability of the various compositions under simulated operating conditions, and the nature of the adsorbed CO2 have been investigated in detail. The requirements for an effective, practical air capture process have been outlined and the ability of amine-oxide hybrid materials to meet these needs has been discussed. Ultimately, the practicality of such a "direct air capture" process is predicated not only on the physicochemical properties of the sorbent, but also how the sorbent operates in a practical process that offers a scalable gas-solid contacting strategy. In this regard, the utility of low pressure drop monolith

  10. Synthetic Studies on Tricyclic Diterpenoids: Direct Allylic Amination Reaction of Isopimaric Acid Derivatives.

    PubMed

    Timoshenko, Mariya A; Kharitonov, Yurii V; Shakirov, Makhmut M; Bagryanskaya, Irina Yu; Shults, Elvira E

    2016-02-01

    A selective synthesis of 7- or 14-nitrogen containing tricyclic diterpenoids was completed according to a strategy in which the key step was the catalyzed direct allylic amination of methyl 14α-hydroxy-15,16-dihydroisopimarate with a wide variety of nitrogenated nucleophiles. It was revealed that the selectivity of the reaction depends on the nature of nucleophile. The catalyzed reaction of the mentioned diterpenoid allylic alcohol with 3-nitroaniline, 3-(trifluoromethyl)aniline, and 4-(trifluoromethyl)aniline yield the subsequent 7α-, 7β- and 14αnitrogen-containing diterpenoids. The reaction with 2-nitroaniline, 4-nitro-2-chloroaniline, 4-methoxy-2-nitroaniline, phenylsulfamide, or tert-butyl carbamate proceeds with the formation of 7α-nitrogen-substituted diterpenoids as the main products. PMID:27308214

  11. Silica Precipitation and Lithium Sorption

    SciTech Connect

    Jay Renew

    2015-09-20

    This file contains silica precipitation and lithium sorption data from the project. The silica removal data is corrected from the previous submission. The previous submission did not take into account the limit of detection of the ICP-MS procedure.

  12. Controllable synthesis of hollow mesoporous silica spheres and application as support of nano-gold

    SciTech Connect

    Wang, Tao; Ma, Weihua Shangguan, Junnan; Jiang, Wei; Zhong, Qin

    2014-07-01

    Hollow silica spheres with mesoporous structure were synthesized by sol–gel/emulsion method. In the process, the surfactant, cetyltrimethylammonium bromide (CTAB) was used to stabilize the oil droplet and also used as structure direct agent. The diameter of the hollow silica spheres, ranging from 895 nm to 157 nm, can be controlled by changing the ratio of ethanol to water and the concentration of the surfactant as well. The shell thickness of the spheres decreased when the ratio of ethanol to water decreased. The proposed mechanism of the formation of silica spheres could elucidate the experimental results well. Furthermore, the resultant hollow mesoporous silica spheres were then employed as support of nano-gold which was used to catalyze the isomerization reaction of propylene oxide to produce allyl alcohol. - Graphical abstract: It is the schematic mechanism for the formation of hollow mesoporous silica spheres. - Highlights: • The formation mechanism of the hollow spheres is proposed. • The isomerization of propylene oxide can be catalyzed by the nano-gold/SiO{sub 2}. • The hollow silica spheres can be prepared controllably.

  13. Application of Silica-Supported Alkylating Reagents in a One-Pot, Sequential Protocol to Diverse Benzoxathiazepine 1,1-Dioxides.

    PubMed

    Faisal, Saqib; Maity, Pradip K; Zang, Qin; Samarakoon, Thiwanka B; Sourk, Robert L; Hanson, Paul R

    2016-07-11

    Applications of silica-ROMP reagents in a one-pot, sequential protocol have been developed for the synthesis of a variety of diverse benzoxathiazepine 1,1-dioxides. This protocol includes sulfonylation, intramolecular SNAr, alkylation with silica-supported oligomeric benzyl (Si-OBPn) and triazole (Si-OTPn) phosphates, and intermolecular SNAr addition with a number of secondary amines in one-pot to afford a variety of unique benzoxathiazepine 1,1-dioxides sultams in good to excellent yields.

  14. Epoxy Grout With Silica Thickener

    NASA Technical Reports Server (NTRS)

    Mcclung, C. E.

    1984-01-01

    Grout cures quickly, even in presence of hydraulic oil. Grout is mixture of aggregate particles, finely-divided silica, epoxy resin, and triethylenetetramine curing agent, with mixture containing about 85 percent silica and aggregate particle sand 15 percent resin and curing agent. Silica is thickening agent and keeps grout from sagging.

  15. Reductions with lithium in low molecular weight amines and ethylenediamine

    PubMed

    Garst; Dolby; Esfandiari; Fedoruk; Chamberlain; Avey

    2000-10-20

    Reductions of several types of compounds with lithium and ethylenediamine using low molecular weight amines as solvent are described. In all cases 1 mol of ethylenediamine or N, N'-dimethylethylenediamine per gram-atom of lithium was used. In some cases it was beneficial to add an alcohol as a proton donor. These reaction conditions were applied to the debenzylation of N-benzylamide and lactams which are refractory to hydrogenolysis with hydrogen and a catalyst. N-Benzylpilolactam 2, synthesized from pilocarpine hydrochloride in refluxing benzylamine, was debenzylated in good yield using 10 gram-atoms of lithium per mole (10 Li/mol) of 2 in n-propylamine. The debenzylation of N-benzyl-N-methyldecanoic acid amide, 4 (6 Li/mol), in t-butylamine/N, N'-dimethylethylenediamine gave N-methyldecanoic acid amide 6 in 70% yield. Alternatively, reduction of 4 (7 Li/mol) in t-butanol/n-propylamine/ethylenediamine gave n-decanal 12 in 36% yield. Using the same conditions, thioanisole, 1-adamantane-p-toluenesulfonamide, and 1-adamantane methyl p-toluenesulfonate were reduced with 3, 7, and 7.2 Li/mol of compound to give thiophenol (74%), adamantamine (91%), and 1-adamantane methanol (75%), respectively. In this solvent system naphthalene and 3-methyl-2-cyclohexene-1-one were reduced to isotetralin (74%) and 3-methyl cyclohexanone (quantitative) with 5 and 2.2 Li/mol of starting compound, respectively. Oximes and O-methyloximes were reduced to their corresponding amines using 5 and 8 Li/mol of compound, respectively. Anisole was also reduced to 1-methoxy-1,4-cyclohexadiene with 2.5 Li/mol of anisole. Undecanenitrile was reduced to undecylamine with 8.6 Li/mol. Additionally, a base-catalyzed formation of imidazolines from a nitrile and ethylenediamine was also explored.

  16. Khalil Amine on Lithium-air Batteries

    SciTech Connect

    Khalil Amine

    2009-09-14

    Khalil Amine, materials scientist at Argonne National Laboratory, speaks on the new technology Lithium-air batteries, which could potentially increase energy density by 5-10 times over lithium-ion batteries.

  17. Khalil Amine on Lithium-air Batteries

    ScienceCinema

    Khalil Amine

    2016-07-12

    Khalil Amine, materials scientist at Argonne National Laboratory, speaks on the new technology Lithium-air batteries, which could potentially increase energy density by 5-10 times over lithium-ion batteries.

  18. Sediment-Associated Reactions of Aromatic Amines

    EPA Science Inventory

    Sorption of aromatic amines to sediments and soils can occur by both reversible physical processes and irreversible chemical processes. To elucidate the significance of these sorption pathways, the sorption kinetics of aniline and pyridine were studied in resaturated pond sedimen...

  19. Amines as occupational hazards for visual disturbance

    PubMed Central

    JANG, Jae-Kil

    2015-01-01

    Various amines, such as triethylamine and N,N-dimethylethylamine, have been reported to cause glaucopsia in workers employed in epoxy, foundry, and polyurethane foam industries. This symptom has been related to corneal edema and vesicular collection of fluid within the corneal subepithelial cells. Exposure to amine vapors for 30 min to several hours leads to blurring of vision, a blue-grey appearance of objects, and halos around lights, that are probably reversible. Concentration-effect relationships have been established. The visual disturbance is considered a nuisance, as it could cause onsite accidents, impair work efficiency, and create difficulties in driving back home. Occupational exposure limits have been established for some amines, but there is shortage of criteria. Volatility factors, such as vapor pressure, should be considered in industrial settings to prevent human ocular risks, while trying to reduce levels of hazardous amines in the atmosphere. PMID:26538000

  20. Solubility of nitrous oxide in amine solutions

    SciTech Connect

    Bensetiti, Z.; Iliuta, I.; Larachi, F.; Grandjean, B.P.A.

    1999-01-01

    The solubility of nitrous oxide (N{sub 2}O) in 13 amine solvents and solutions was correlated to amine mole fractions and temperature using feedforward neural networks. This general correlation, using a massive database, predicted N{sub 2}O solubility at temperatures between 283 and 398 K in pure solvents [H{sub 2}O, monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA), and 2-amino-2-methyl-1-propanolamine (AMP)], in binary aqueous amine solutions [H{sub 2}O/MEA, H{sub 2}O/DEA, H{sub 2}O/MDEA, and H{sub 2}O/AMP], and in ternary aqueous amine blends [AMP/MDEA/H{sub 2}O, AMP/DEA/H{sub 2}O, DEA/MDEA/H{sub 2}O, MDEA/MEA/H{sub 2}O, and AMP/MEA/H{sub 2}O]. Combined with the N{sub 2}O analogy, this present improved correlation can be advantageously implemented in amine plant design software and procedures for the prediction of CO{sub 2} solubility in amine blend solutions over wide temperature and concentration ranges.

  1. Borinic Acid Catalyzed Stereo- and Regioselective Couplings of Glycosyl Methanesulfonates.

    PubMed

    D'Angelo, Kyan A; Taylor, Mark S

    2016-08-31

    In the presence of a diarylborinic acid catalyst, glycosyl methanesulfonates engage in regio- and stereoselective couplings with partially protected pyranoside and furanoside acceptors. The methanesulfonate donors are prepared in situ from glycosyl hemiacetals, and are coupled under mild, operationally simple conditions (amine base, organoboron catalyst, room temperature). The borinic acid catalyst not only influences site-selectivity via activation of 1,2- or 1,3-diol motifs, but also has a pronounced effect on the stereochemical outcome: 1,2-trans-linked disaccharides are obtained selectively in the absence of neighboring group participation. Reaction progress kinetic analysis was used to obtain insight into the mechanism of glycosylation, both in the presence of catalyst and in its absence, while rates of interconversion of methanesulfonate anomers were determined by NMR exchange spectroscopy (EXSY). Together, the results suggest that although the uncatalyzed and catalyzed reactions give rise to opposite stereochemical outcomes, both proceed by associative mechanisms. PMID:27533523

  2. Transition Metals Catalyzed Element-Cyano Bonds Activations

    PubMed Central

    Wang, Rui; Falck, John R.

    2014-01-01

    Cyano group as a versatile functionalized intermediate has been explored for several decades, as it readily transfers to many useful functionalization groups such as amine, amide, acid, etc., which make it possess high popularization and use value in organic synthesis. Reactions involved with element-cyano bond cleavage can provide not only a new cyano group but also a freshly functionalized skeleton in one-pot, consequently making it of high importance. The highlights reviewed herein include H-CN, Si-CN, C-CN, B-CN, Sn-CN, Ge-CN, S-CN, Halo-CN, N-CN, and O-CN bonds cleavages and will summarize progress in such an important research area. This review article will focus on transition metal catalyzed reactions involving element-cyano bond activation. PMID:25558119

  3. Sc(OTf)3-catalyzed bicyclization of o-alkynylanilines with aldehydes: ring-fused 1,2-dihydroquinolines.

    PubMed

    Zhu, Can; Ma, Shengming

    2014-12-01

    A Sc(OTf)3 -catalyzed cascade Prins-type cyclization reaction of o-alkynylanilines, bearing a hydroxy or amine functionality, with aldehydes affords 1,2-dihydroquinoline derivatives having an extra fused ring efficiently under mild reaction conditions. It is interesting to observe the reversed reactivity in the highly selective formation of 1,2-dihydroquinoline derivatives instead of the formation of the usually favored indole derivatives.

  4. Novel visible-light-driven photocatalyst. Poly(p-phenylene)-catalyzed photoreductions of water, carbonyl compounds, and olefins

    SciTech Connect

    Shibata, Takuya; Kabumoto, Akira; Shiragami, Tsutomu; Ishitani, Osamu; Pac, Chyongjin; Yanagida, Shozo )

    1990-03-08

    The insoluble yellow powder of poly(p-phenylene) (PPP) prepared by nickel-catalyzed polycondensation of the Grignard reagent from 1,4-dibromobenzene shows photocatalytic activity under visible light toward water, carbonyl compounds, and olefins. Water is photoreduced to H{sub 2} in the presence of amines as sacrificial electron donors. The H{sub 2} evolution is enhanced 3-20 times by noble-metal deposition, in which Ru deposition is the most effective.

  5. Palladium-Catalyzed Carbonylation of β-Arylethylamide Directed by Oxalyl Amide in the Presence of Carbon Monoxide.

    PubMed

    Zhang, Li; Wang, Chao; Han, Jian; Huang, Zhi-Bin; Zhao, Yingsheng

    2016-06-17

    Pd-catalyzed regioselective coupling of β-C(sp(2))-H bonds in aromatic amines protected by oxalyl amide with carbon monoxide is reported. The reaction could tolerate various functional groups and could afford good to excellent yields of the corresponding 3,4-dihydroisoquinolinone derivatives. Remarkably, it could also tolerate β-arylethylamino acid and thiopheneethylamine derivatives, thus showing their potential for producing several important units for bioactive compound synthesis. PMID:27213988

  6. Copper-Catalyzed Enantioselective Addition of Styrene-Derived Nucleophiles to Imines Enabled by Ligand-Controlled Chemoselective Hydrocupration.

    PubMed

    Yang, Yang; Perry, Ian B; Buchwald, Stephen L

    2016-08-10

    The copper-catalyzed intermolecular enantioselective addition of styrenes to imines has been achieved under mild conditions at ambient temperature. This process features the use of styrenes as latent carbanion equivalents via the intermediacy of catalytically generated benzylcopper derivatives, providing an effective means for accessing highly enantiomerically enriched amines bearing contiguous stereocenters. Mechanistic studies shed light on the origin of the preferential styrene hydrocupration in the presence of an imine with the Ph-BPE-derived copper catalyst. PMID:27454393

  7. Accurate determination of aldehydes in amine catalysts or amines by 2,4-dinitrophenylhydrazine derivatization.

    PubMed

    Barman, Bhajendra N

    2014-01-31

    Carbonyl compounds, specifically aldehydes, present in amine catalysts or amines are determined by reversed-phase liquid chromatography using ultraviolet detection of their corresponding 2,4-dinitrophenylhydrazones. The primary focus has been to establish optimum conditions for determining aldehydes accurately because these add exposure concerns when the amine catalysts are used to manufacture polyurethane products. Concentrations of aldehydes determined by this method are found to vary with the pH of the aqueous amine solution and the derivatization time, the latter being problematic when the derivatization reaction proceeds slowly and not to completion in neutral and basic media. Accurate determination of aldehydes in amines through derivatization can be carried out at an effective solution pH of about 2 and with derivatization time of 20min. Hydrochloric acid has been used for neutralization of an amine. For complete derivatization, it is essential to protonate all nitrogen atoms in the amine. An approach for the determination of an adequate amount of acid needed for complete derivatization has been described. Several 0.2M buffer solutions varying in pH from 4 to 8 have also been used to make amine solutions for carrying out derivatization of aldehydes. These solutions have effective pHs of 10 or higher and provide much lower aldehyde concentrations compared to their true values. Mechanisms for the formation of 2,4-dinitrophenylhydrazones in both acidic and basic media are discussed. PMID:24411140

  8. Synthesis of Bis(hydroxylmethylfurfuryl)amine Monomers from 5-Hydroxymethylfurfural.

    PubMed

    Xu, Zhanwei; Yan, Peifang; Liu, Kairui; Wan, Lu; Xu, Wenjuan; Li, Huixiang; Liu, Xiumei; Zhang, Z Conrad

    2016-06-01

    We report the synthesis of bis(hydroxylmethylfurfuryl)amine (BHMFA) from 5-hydroxymethylfurfural (5-HMF) by reacting 5-HMF with primary amines in the presence of homogeneous Ru(II) catalysts having sterically strained ligands. BHMFA is a group of furan-based monomers that offer great potential to form functional biopolymers with tunable properties. A range of primary amines, such as aliphatic and benzyl amines, are readily converted with 5-HMF to form the corresponding BHMFA in good yields. The reaction proceeds through reductive amination of 5-HMF with primary amine to form secondary amine, followed by reductive amination of 5-HMF with in situ generated secondary amine to produce BHMFA. PMID:27151257

  9. TMEDA in iron-catalyzed Kumada coupling: amine adduct versus homoleptic "ate" complex formation.

    PubMed

    Bedford, Robin B; Brenner, Peter B; Carter, Emma; Cogswell, Paul M; Haddow, Mairi F; Harvey, Jeremy N; Murphy, Damien M; Nunn, Joshua; Woodall, Christopher H

    2014-02-10

    The reactions of iron chlorides with mesityl Grignard reagents and tetramethylethylenediamine (TMEDA) under catalytically relevant conditions tend to yield the homoleptic "ate" complex [Fe(mes)3 ](-) (mes=mesityl) rather than adducts of the diamine, and it is this ate complex that accounts for the catalytic activity. Both [Fe(mes)3 ](-) and the related complex [Fe(Bn)3 ](-) (Bn=benzyl) react faster with representative electrophiles than the equivalent neutral [FeR2 (TMEDA)] complexes. Fe(I) species are observed under catalytically relevant conditions with both benzyl and smaller aryl Grignard reagents. The X-ray structures of [Fe(Bn)3 ](-) and [Fe(Bn)4 ](-) were determined; [Fe(Bn)4 ](-) is the first homoleptic σ-hydrocarbyl Fe(III) complex that has been structurally characterized. PMID:24505000

  10. Viscoelasticity of silica gels

    SciTech Connect

    Scherer, G.W.

    1995-12-01

    The response of silica gels to mechanical loads depends on the properties of the solid phase and the permeability of the network. Understanding this behavior is essential for modeling of stresses developed during drying or heating of gels. The permeability and the mechanical properties are readily determined from a simple beam-bending experiment, by measuring the load relaxation that occurs at constant deflection. Load decay results from movement of the liquid within the network; in addition, there may be viscoelastic relaxation of the network itself. Silica gel is viscoelastic in chemically aggressive media, but in inert liquids (such as ethanol or acetone) it is elastic. Experiments show that the viscoelastic relaxation time decreases as the concentration and pH of the water in the pore liquid increase. During drying, the permeability decreases and the viscosity increases, both exhibiting a power-law dependence on density of the gel network.

  11. Linking CO2 Sorption Performance to Polymer Morphology in Aminopolymer/Silica Composites through Neutron Scattering.

    PubMed

    Holewinski, Adam; Sakwa-Novak, Miles A; Jones, Christopher W

    2015-09-16

    Composites of poly(ethylenimine) (PEI) and mesoporous silica are effective, reversible adsorbents for CO2, both from flue gas and in direct air-capture applications. The morphology of the PEI within the silica can strongly impact the overall carbon capture efficiency and rate of saturation. Here, we directly probe the spatial distribution of the supported polymer through small-angle neutron scattering (SANS). Combined with textural characterization from physisorption analysis, the data indicate that PEI first forms a thin conformal coating on the pore walls, but all additional polymer aggregates into plug(s) that grow along the pore axis. This model is consistent with observed trends in amine-efficiency (CO2/N binding ratio) and pore size distributions, and points to a trade-off between achieving high chemical accessibility of the amine binding sites, which are inaccessible when they strongly interact with the silica, and high accessibility for mass transport, which can be hampered by diffusion through PEI plugs. We illustrate this design principle by demonstrating higher CO2 capacity and uptake rate for PEI supported in a hydrophobically modified silica, which exhibits repulsive interactions with the PEI, freeing up binding sites.

  12. Primary, secondary, and tertiary amines for CO2 capture: designing for mesoporous CO2 adsorbents.

    PubMed

    Ko, Young Gun; Shin, Seung Su; Choi, Ung Su

    2011-09-15

    CO(2) emissions, from fossil-fuel-burning power plants, the breathing, etc., influence the global worming on large scale and the man's work efficiency on small scale. The reversible capture of CO(2) is a prominent feature of CO(2) organic-inorganic hybrid adsorbent to sequester CO(2). Herein, (3-aminopropyl) trimethoxysilane (APTMS), [3-(methylamino)propyl] trimethoxysilane (MAPTMS), and [3-(diethylamino) propyl] trimethoxysilane (DEAPTMS) are immobilized on highly ordered mesoporous silicas (SBA-15) to catch CO(2) as primary, secondary, and tertiary aminosilica adsorbents. X-ray photoelectron spectroscopy was used to analyze the immobilized APTMS, MAPTMS, and DEAPTMS on the SBA-15. We report an interesting discovery that the CO(2) adsorption and desorption on the adsorbent depend on the amine type of the aminosilica adsorbent. The adsorbed CO(2) was easily desorbed from the adsorbent with the low energy consumption in the order of tertiary, secondary, and primary amino-adsorbents while the adsorption amount and the bonding-affinity increased in the reverse order. The effectiveness of amino-functionalized (1(o), 2(o), and 3(o) amines) SBA-15s as a CO(2) capturing agent was investigated in terms of adsorption capacity, adsorption-desorption kinetics, and thermodynamics. This work demonstrates apt amine types to catch CO(2) and regenerate the adsorbent, which may open new avenues to designing "CO(2) basket". PMID:21708387

  13. Nickel-Catalyzed Reductive Couplings.

    PubMed

    Wang, Xuan; Dai, Yijing; Gong, Hegui

    2016-08-01

    The Ni-catalyzed reductive coupling of alkyl/aryl with other electrophiles has evolved to be an important protocol for the construction of C-C bonds. This chapter first emphasizes the recent progress on the Ni-catalyzed alkylation, arylation/vinylation, and acylation of alkyl electrophiles. A brief overview of CO2 fixation is also addressed. The chemoselectivity between the electrophiles and the reactivity of the alkyl substrates will be detailed on the basis of different Ni-catalyzed conditions and mechanistic perspective. The asymmetric formation of C(sp(3))-C(sp(2)) bonds arising from activated alkyl halides is next depicted followed by allylic carbonylation. Finally, the coupling of aryl halides with other C(sp(2))-electrophiles is detailed at the end of this chapter. PMID:27573395

  14. CCN activity of aliphatic amine secondary aerosol

    NASA Astrophysics Data System (ADS)

    Tang, X.; Price, D.; Praske, E.; Vu, D.; Purvis-Roberts, K.; Silva, P. J.; Cocker, D. R., III; Asa-Awuku, A.

    2014-01-01

    Aliphatic amines can form secondary aerosol via oxidation with atmospheric radicals (e.g. hydroxyl radical and nitrate radical). The particle composition can contain both secondary organic aerosol (SOA) and inorganic salts. The fraction of organic to inorganic materials in the particulate phase influences aerosol hygroscopicity and cloud condensation nuclei (CCN) activity. SOA formed from trimethylamine (TMA) and butylamine (BA) reactions with hydroxyl radical (OH) is composed of organic material of low hygroscopicity (single hygroscopicity parameter, κ ≤ 0.25). Secondary aerosol formed from the tertiary aliphatic amine (TMA) with N2O5 (source of nitrate radical, NO3), contains less volatile compounds than the primary aliphatic amine (BA) aerosol. TMA + N2O5 form semi-volatile organics in low RH conditions that have κ ~ 0.20, indicative of slightly soluble organic material. As RH increases, several inorganic amine salts are formed as a result of acid-base reactions. The CCN activity of the humid TMA-N2O5 aerosol obeys Zdanovskii, Stokes, and Robinson (ZSR) ideal mixing rules. Higher CCN activity (κ > 0.3) was also observed for humid BA+N2O5 aerosols compared with dry aerosol (κ ~ 0.2), as a result of the formation of inorganic salts such as NH4NO3 and butylamine nitrate (C4H11N · HNO3). Compared with TMA, BA+N2O5 reactions produce more volatile aerosols. The BA+N2O5 aerosol products under humid experiments were found to be very sensitive to the temperature within the stream-wise continuous flow thermal gradient CCN counter. The CCN counter, when set above a 21 °C temperature difference, evaporates BA+N2O5 aerosol formed at RH ≥ 30%; κ ranges from 0.4 to 0.7 and is dependent on the instrument supersaturation (ss) settings. The aerosol behaves non-ideally, hence simple ZSR rules cannot be applied to the CCN results from the primary aliphatic amine system. Overall, aliphatic amine aerosol systems κ ranges from 0.2 < κ < 0.7. This work indicates that

  15. The mechanism of borane-amine dehydrocoupling with bifunctional ruthenium catalysts.

    PubMed

    Marziale, Alexander N; Friedrich, Anja; Klopsch, Isabel; Drees, Markus; Celinski, Vinicius R; Schmedt auf der Günne, Jörn; Schneider, Sven

    2013-09-11

    Borane-amine adducts have received considerable attention, both as vectors for chemical hydrogen storage and as precursors for the synthesis of inorganic materials. Transition metal-catalyzed ammonia-borane (H3N-BH3, AB) dehydrocoupling offers, in principle, the possibility of large gravimetric hydrogen release at high rates and the formation of B-N polymers with well-defined microstructure. Several different homogeneous catalysts were reported in the literature. The current mechanistic picture implies that the release of aminoborane (e.g., Ni carbenes and Shvo's catalyst) results in formation of borazine and 2 equiv of H2, while 1 equiv of H2 and polyaminoborane are obtained with catalysts that also couple the dehydroproducts (e.g., Ir and Rh diphosphine and pincer catalysts). However, in comparison with the rapidly growing number of catalysts, the amount of experimental studies that deal with mechanistic details is still limited. Here, we present a comprehensive experimental and theoretical study about the mechanism of AB dehydrocoupling to polyaminoborane with ruthenium amine/amido catalysts, which exhibit particularly high activity. On the basis of kinetics, trapping experiments, polymer characterization by (11)B MQMAS solid-state NMR, spectroscopic experiments with model substrates, and density functional theory (DFT) calculations, we propose for the amine catalyst [Ru(H)2PMe3{HN(CH2CH2PtBu2)2}] two mechanistically connected catalytic cycles that account for both metal-mediated substrate dehydrogenation to aminoborane and catalyzed polymer enchainment by formal aminoborane insertion into a H-NH2BH3 bond. Kinetic results and polymer characterization also indicate that amido catalyst [Ru(H)PMe3{N(CH2CH2PtBu2)2}] does not undergo the same mechanism as was previously proposed in a theoretical study. PMID:23930890

  16. Content of biogenic amines in table olives.

    PubMed

    García-García, P; Brenes-Balbuena, M; Hornero-Méndez, D; García-Borrego, A; Garrido-Fernández, A

    2000-01-01

    Content of biogenic amines in flesh and brines of table olives was determined by high-pressure liquid chromatography analysis of their benzoyl derivatives. No biogenic amines were found in the flesh of fresh fruits at any stage of ripeness. Contents of biogenic amines in Spanish-style green or stored olives increased throughout the brining period but were always higher in the former. Putrescine was the amine found in the highest concentration. Small quantities of cadaverine were found in the samples taken after 3 months of brining. This compound and histamine, tyramine, and tryptamine were also found in samples taken after 12 months. Gordal cultivar showed the highest contents, followed by Manzanilla and Hojiblanca. No relationship was found between contents of biogenic amines and lactic acid production or table olive spoilages, although zapatera olives had considerably higher amounts than those brines that had undergone a normal process. Concentrations in directly brined olives were markedly lower than contents in Spanish-style olives. With respect to partition between flesh and brine, there was equilibrium between both media in the case of Spanish-style olives, whereas the contents in directly brined olives were higher in flesh than brine. PMID:10643779

  17. Conversion of aminodeoxychorismate synthase into anthranilate synthase with Janus mutations: mechanism of pyruvate elimination catalyzed by chorismate enzymes.

    PubMed

    Culbertson, Justin E; Chung, Dong hee; Ziebart, Kristin T; Espiritu, Eduardo; Toney, Michael D

    2015-04-14

    The central importance of chorismate enzymes in bacteria, fungi, parasites, and plants combined with their absence in mammals makes them attractive targets for antimicrobials and herbicides. Two of these enzymes, anthranilate synthase (AS) and aminodeoxychorismate synthase (ADCS), are structurally and mechanistically similar. The first catalytic step, amination at C2, is common between them, but AS additionally catalyzes pyruvate elimination, aromatizing the aminated intermediate to anthranilate. Despite prior attempts, the conversion of a pyruvate elimination-deficient enzyme into an elimination-proficient one has not been reported. Janus, a bioinformatics method for predicting mutations required to functionally interconvert homologous enzymes, was employed to predict mutations to convert ADCS into AS. A genetic selection on a library of Janus-predicted mutations was performed. Complementation of an AS-deficient strain of Escherichia coli grown on minimal medium led to several ADCS mutants that allow growth in 6 days compared to 2 days for wild-type AS. The purified mutant enzymes catalyze the conversion of chorismate to anthranilate at rates that are ∼50% of the rate of wild-type ADCS-catalyzed conversion of chorismate to aminodeoxychorismate. The residues mutated do not contact the substrate. Molecular dynamics studies suggest that pyruvate elimination is controlled by the conformation of the C2-aminated intermediate. Enzymes that catalyze elimination favor the equatorial conformation, which presents the C2-H to a conserved active site lysine (Lys424) for deprotonation and maximizes stereoelectronic activation. Acid/base catalysis of pyruvate elimination was confirmed in AS and salicylate synthase by showing incorporation of a solvent-derived proton into the pyruvate methyl group and by solvent kinetic isotope effects on pyruvate elimination catalyzed by AS. PMID:25710100

  18. 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.

  19. 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

  20. Novel palladium complex-catalyzed reaction of magnesium amides with allylic electrophiles

    SciTech Connect

    Dzhemilev, U.M.; Ibragimov, A.G.; Minsker, D.L.; Muslukhov, R.R.

    1987-08-20

    In order to develop an efficient method for the synthesis of higher order unsaturated tertiary amines, and also to explore a new method for the formation of C-N bonds, they have investigated the transition metal complex-catalyzed reaction of magnesium amides with electrophiles; the electrophiles selected for study included allyl ethers and esters, as well as sulfones, sulfides and quaternized allylamines. The effects of the nature and structure of the catalyst components, as well as of the reaction conditions, on product yield were examined in the case of the reaction of diethyl (bromomagnesium)amine with diallyl ether, and revealed that the highest yield of diethylallyl-amine (I) was achieved using Pd(acac)/sub 2/ (3-5 mole %) and Ph/sub 3/P (1:2) as catalyst in THF solution at 50/sup 0/C for 5 h. Other transition metal (Ni, Fe, Zr, Ti, Cu) compounds were also examined as catalysts, but the yield of (I) did not exceed 15% with these compounds. Bimetallic catalysts based on Zr (Cp/sub 2/ZrCl, Py/sub 2/ZrCl/sub 6/, (RO)/sub 4/Zr) and Ni (Ni(acac)/sub 2/ and NiCl/sub 2/) were successful in forming (I) from diethyl (bromomagnesium)amine and diallyl ether in 60% yield.

  1. Surface Patterning of Silica Nanostructures Using Bio-Inspired Templates and Directed Synthesis

    SciTech Connect

    Coffman, Elizabeth A; Melechko, Anatoli Vasilievich; Allison, David P; Simpson, Michael L; Doktycz, Mitchel John

    2004-01-01

    Natural systems excel in directing the synthesis of inorganic materials for various functional purposes. One of the best-studied systems is silica synthesis, as occurs in diatoms and marine sponges. Various biological and synthetic polymers have been shown to template and catalyze silica formation from silicic acid precursors. Here, we describe the use of poly-l-lysine to promote the synthesis of silica in neutral, aqueous solution and when immobilized onto a silicon support structure under similar conditions. Either reagent jetting or conventional photolithography techniques can be used to pattern the templating polymer. Spots created by reagent jetting led to the creation of silica structures in the shape of a ring that may be a result of the spotting process. Photolithographically defined poly-l-lysine spots led to thin laminate structures after exposure to a dilute aqueous silicic acid solution. The laminate structures were nanostructured and highly interconnected. Photolithographic patterning of (3-aminopropyl)trimethoxysilane, a reagent that mimics the lysine functional group, led to similar silica coatings even though low-molecular-weight materials do not rapidly promote silica synthesis in solution. This result highlights the importance of functional-group arrangement for templating and promoting the synthesis of inorganic materials. The described surface-patterning techniques offer a route to integrate conventional silicon-patterning technologies with biologically based material synthesis. Such combined fabrication techniques enable controlled assembly over multiple length scales and an approach to understanding interfacial silica synthesis, as occurs in natural systems.

  2. 21 CFR 182.1711 - Silica aerogel.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Silica aerogel. 182.1711 Section 182.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  3. 21 CFR 582.1711 - Silica aerogel.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  4. 21 CFR 182.1711 - Silica aerogel.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Silica aerogel. 182.1711 Section 182.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  5. 21 CFR 582.1711 - Silica aerogel.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  6. 21 CFR 582.1711 - Silica aerogel.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  7. 21 CFR 182.1711 - Silica aerogel.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Silica aerogel. 182.1711 Section 182.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  8. 21 CFR 582.1711 - Silica aerogel.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  9. 21 CFR 182.1711 - Silica aerogel.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Silica aerogel. 182.1711 Section 182.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  10. 21 CFR 182.1711 - Silica aerogel.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Silica aerogel. 182.1711 Section 182.1711 Food and... GENERALLY RECOGNIZED AS SAFE Multiple Purpose GRAS Food Substances § 182.1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of...

  11. 21 CFR 582.1711 - Silica aerogel.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  12. Di-Isocyanate Crosslinked Aerogels with 1, 6-Bis (Trimethoxysilyl) Hexane Incorporated in Silica Backbone

    NASA Technical Reports Server (NTRS)

    Vivod, Stephanie L.; Meador, Mary Ann B.; Nguyen, Baochau N.; Quade, Derek; Randall, Jason; Perry, Renee

    2008-01-01

    Silica aerogels are desirable materials for many applications that take advantage of their light weight and low thermal conductivity. Addition of a conformal polymer coating which bonds with the amine decorated surface of the silica network improves the strength of the aerogels by as much as 200 times. Even with vast improvement in strength they still tend to undergo brittle failure due to the rigid silica backbone. We hope to increase the flexibility and elastic recovery of the silica based aerogel by altering the silica back-bone by incorporation of more flexible hexane links. To this end, we investigated the use of 1,6-bis(trimethoxysilyl)hexane (BTMSH), a polysilsesquioxane precursor3, as an additional co-reactant to prepare silica gels which were subsequently cross-linked with di-isocyanate. Previously, this approach of adding flexibility by BTMSH incorporation was demonstrated with styrene cross-linked aerogels. In our study, we varied silane concentration, mol % of silicon from BTMSH and di-isocyanate concentration by weight percent to attempt to optimize both the flexibility and the strength of the aerogels.

  13. Surface properties and water treatment capacity of surface engineered silica coated with 3-(2-aminoethyl) aminopropyltrimethoxysilane

    NASA Astrophysics Data System (ADS)

    Majewski, Peter; Keegan, Alexandra

    2012-01-01

    This study's focus was on the water-based, one-pot preparation and characterisation of silica particles coated with 3-(2-aminoethyl)aminopropyltrimethoxysilane (Diamo) and the efficiency of the material in removing the pathogens Escherichia coli, Pseudomonas aeruginosa, Mycobacterium immunogenum, Vibrio cholerae, poliovirus, and Cryptosporidium parvum. The water-based processing resulted in Diamo coated silica particles with significantly increased positive surface charge as determined by zeta potential measurements. In addition, X-ray photoelectron spectrometry of pure and Diamo coated silica confirmed the presence of Diamo on the surface of the particles. Thermogravimetric measurements and chemical analysis of the silica indicated a surface concentration of amine groups of about 1 mmol/gsilica. Water treatment tests with the pathogens showed that a dose of about 10 g appeared to be sufficient to remove pathogens from pure water samples which were spiked with pathogen concentrations between about 102 and 104 cfu/mL.

  14. Multistep divergent synthesis of benzimidazole linked benzoxazole/benzothiazole via copper catalyzed domino annulation.

    PubMed

    Liao, Jen-Yu; Selvaraju, Manikandan; Chen, Chih-Hau; Sun, Chung-Ming

    2013-04-21

    An efficient, facile synthesis of structurally diverse benzimidazole integrated benzoxazole and benzothiazoles has been developed. In a multi-step synthetic sequence, 4-fluoro-3-nitrobenzoic acid was converted into benzimidazole bis-heterocycles, via the intermediacy of benzimidazole linked ortho-chloro amines. The amphiphilic reactivity of this intermediate was designed to achieve the title compounds by the reaction of various acid chlorides and isothiocyanates in a single step through the in situ formation of ortho-chloro anilides and thioureas under microwave irradiation. A versatile one pot domino annulation reaction was developed to involve the reaction of benzimidazole linked ortho-chloro amines with acid chlorides and isothiocyanates. The initial acylation and urea formation followed by copper catalyzed intramolecular C-O and C-S cross coupling reactions furnished the angularly oriented bis-heterocycles which bear a close resemblance to the streptomyces antibiotic UK-1.

  15. Enhanced catalytic degradation process of o-nitrochlorobenzene by palladium-catalyzed fe0 particles.

    PubMed

    Xu, Xin-hua; Zhou, Hong-yi; Zhou, Mi; Wang, Da-hui

    2005-01-01

    Over Pd/Fe bimetallic catalyst, o-nitrochlorobenzene (o-NCB), at a concentration of 20 mg/L in aqueous solutions, is rapidly converted to o-chloroaniline (o-CAN) first, and then quickly dechlorinated to aniline(AN) and Cl-, without other intermediate reaction products. The aminated and dechlorinated reactions are believed to take place on the surface site of the Pd/Fe. The o-NCB removal efficiency and the next dechlorination rate increase with an increase of bulk loading of palladium and catalysts addition due to the increase of both the surface loading of palladium and the total surface area. These results indicate that reduction, amination and dechlorination of o-NCB by palladium-catalyzed Fe0 particles, can be designed for remediation of contaminated groundwater.

  16. Nanoporous silica membranes fabricated using multiwalled carbon nanotubes.

    PubMed

    Kim, Hun-Sik; Kwon, Ha Il; Yun, Young Soo; Bak, Hyeonseong; Yoon, Jin-San; Jin, Hyoung-Joon

    2011-05-01

    Nanoporous silica membranes were fabricated using 3-aminopropyltriethoxysilane (APS) and acyl chloride-functionalized multiwalled carbon nanotubes (MWCNTs). The amine groups of silane reacted with the functional groups (e.g., acid chloride) that were attached to the sidewall of the MWCNTs. The APS that was grafted to the sidewall of the MWCNTs was polymerized in order to coat the MWCNTs wall through heating. The thickness of the silica layer on the surface of the MWCNTs was controlled by adjusting the growth time of the SiO2 layer. Approximately 20 nm-sized pores were formed through the removal of the MWCNTs using a simple thermal process, but some traces of the MWCNTs still remained. The porous properties of the nanoporous silica membrane were analyzed from the nitrogen adsorption-desorption isotherms that were obtained using a surface area and porosimetry analyzer. The structure and composition of the silane-modified MWCNTs were characterized using scanning electron microscopy, energy dispersive spectroscopy and transmission electron microscopy. PMID:21780471

  17. Amine permeation sources characterized with acid neutralization and sensitivities of an amine mass spectrometer

    NASA Astrophysics Data System (ADS)

    Freshour, N. A.; Carlson, K. K.; Melka, Y. A.; Hinz, S.; Panta, B.; Hanson, D. R.

    2014-10-01

    An acid titration method for quantifying amine permeation rates was used to calibrate an Ambient pressure Proton transfer Mass Spectrometer (AmPMS) that monitors ambient amine compounds. The method involves capturing amines entrained in a N2 flow by bubbling it through an acidified solution (~10-5 M HCl), and the amines are quantified via changes in solution pH with time. Home-made permeation tubes had permeation rates (typically tens of pmol s-1) that depended on the type of amine and tubing and on temperature. Calibrations of AmPMS yielded sensitivities for ammonia, methylamine, dimethylamine, and trimethylamine that are close to the sensitivity assuming a gas-kinetic, ion-molecule rate coefficient. The permeation tubes were also designed to deliver a reproducible amount of amine to a flow reactor where nucleation with sulfuric acid was studied. The high proton affinity compound dimethyl sulfoxide (DMSO), linked to oceanic environments, was also studied and AmPMS is highly sensitive to it. AmPMS was deployed recently in two field campaigns and, using these sensitivities, mixing ratios for ammonia and the alkyl amines are derived from the signals. Correlations between these species and with particle formation events are discussed.

  18. The world ocean silica cycle.

    PubMed

    Tréguer, Paul J; De La Rocha, Christina L

    2013-01-01

    Over the past few decades, we have realized that the silica cycle is strongly intertwined with other major biogeochemical cycles, like those of carbon and nitrogen, and as such is intimately related to marine primary production, the efficiency of carbon export to the deep sea, and the inventory of carbon dioxide in the atmosphere. For nearly 20 years, the marine silica budget compiled by Tréguer et al. (1995) , with its exploration of reservoirs, processes, sources, and sinks in the silica cycle, has provided context and information fundamental to study of the silica cycle. Today, the budget needs revisiting to incorporate advances that have notably changed estimates of river and groundwater inputs to the ocean of dissolved silicon and easily dissolvable amorphous silica, inputs from the dissolution of terrestrial lithogenic silica in ocean margin sediments, reverse weathering removal fluxes, and outputs of biogenic silica (especially on ocean margins and in the form of nondiatomaceous biogenic silica). The resulting budget recognizes significantly higher input and output fluxes and notes that the recycling of silicon occurs mostly at the sediment-water interface and not during the sinking of silica particles through deep waters.

  19. Amine Gradient Stationary Phases on In-House Built Monolithic Columns for Liquid Chromatography.

    PubMed

    Dewoolkar, Veeren C; Jeong, Lena N; Cook, Daniel W; Ashraf, Kayesh M; Rutan, Sarah C; Collinson, Maryanne M

    2016-06-01

    Stationary phase gradients on monolithic silica columns have been successfully and reproducibly prepared and characterized with comparisons made to uniformly modified stationary phases. Stationary phase gradients hold great potential for use in liquid chromatography (LC), both in terms of simplifying analysis as well as providing novel selectivity. In this work, we demonstrate the creation of a continuous stationary phase gradient on in-house synthesized monolithic columns by infusing an aminoalkoxysilane solution through the silica monoliths via controlled rate infusion. The presence of amine and its distribution along the length of gradient and uniformly modified columns were assessed via X-ray photoelectron spectroscopy (XPS). XPS showed a clear gradient in surface coverage along the length of the column for the gradient stationary phases while a near uniform distribution on the uniformly modified stationary phases. To demonstrate the application of these gradient stationary phases, the separations of both nucleobases and weak acids/weak bases on these gradient stationary phases have been compared to uniformly modified and unmodified silica columns. Of particular note, the retention characteristics of 11 gradient columns, 5 uniformly modified columns, and 5 unmodified columns have been tested to establish the reproducibility of the synthetic procedures. Standard deviations of the retention factors were in the range from 0.06 to 0.5, depending on the analyte species. We show that selectivity is achieved with the stationary phase gradients that are significantly different from either uniformly modified amine or unmodified columns. These results indicate the significant promise of this strategy for creating novel stationary phases for LC. PMID:27203513

  20. Base metal dehydrogenation of amine-boranes

    DOEpatents

    Blacquiere, Johanna Marie; Keaton, Richard Jeffrey; Baker, Ralph Thomas

    2009-06-09

    A method of dehydrogenating an amine-borane having the formula R.sup.1H.sub.2N--BH.sub.2R.sup.2 using base metal catalyst. The method generates hydrogen and produces at least one of a [R.sup.1HN--BHR.sup.2].sub.m oligomer and a [R.sup.1N--BR.sup.2].sub.n oligomer. The method of dehydrogenating amine-boranes may be used to generate H.sub.2 for portable power sources, such as, but not limited to, fuel cells.

  1. A new amine catalyst for polyurethanes

    SciTech Connect

    Ziv, M.H.; Mascioli, R.L.

    1982-05-01

    This article reports on a new amine catalyst for polyurethanes, the X-8154, which is a delayed action polyurethane catalyst. Experimental results indicated that unlike conventional amine catalysts, the X-8154's unique property of delayed initiation followed by rapid complete cure provides excellent processing and high quality parts. Good flow ability of the components in the production of rigid foams yields uniformity of properties necessary for a high quality product. X-8154, by virtue of its ability to delay reactivity, should find broad use in rigid foams, both in appliance and structural applications.

  2. Silanediol-Catalyzed Chromenone Functionalization.

    PubMed

    Hardman-Baldwin, Andrea M; Visco, Michael D; Wieting, Joshua M; Stern, Charlotte; Kondo, Shin-Ichi; Mattson, Anita E

    2016-08-01

    Promising levels of enantiocontrol are observed in the silanediol-catalyzed addition of silyl ketene acetals to benzopyrylium triflates. This rare example of enantioselective, intermolecular chromenone functionalization with carbonyl-containing nucleophiles has potential applications in the synthesis of bioactive chromanones and tetrahydroxanthones. PMID:27453257

  3. Iodine-Catalyzed Polysaccharide Esterification

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A review is provided of the recent reports to use iodine-catalyzed esterification reaction to produce esters from polysaccharides. The process entails reaction of the polysaccharide with an acid anhydride in the presence of a catalytic level of iodine, and in the absence of additional solvents. T...

  4. Pd-catalyzed steroid reactions.

    PubMed

    Czajkowska-Szczykowska, Dorota; Morzycki, Jacek W; Wojtkielewicz, Agnieszka

    2015-05-01

    We review the most important achievements of the last decade in the field of steroid synthesis in the presence of palladium catalysts. Various palladium-catalyzed cross-coupling reactions, including Heck, Suzuki, Stille, Sonogashira, Negishi and others, are exemplified with steroid transformations.

  5. DIRECT SYNTHESIS OF TERTIARY AMINES IN WATER USING MICROWAVES

    EPA Science Inventory

    A direct synthesis of tertiary amines is presented that proceeds expeditiously via N-alkylation of amines using alkyl halides in alkaline aqueous medium. This environmentally benign reaction is accelerated upon exposure to microwave irradiation resulting in shortened reaction tim...

  6. SEDIMENT-ASSOCIATED REACTIONS OF AROMATIC AMINES. 2. QSAR DEVELOPMENT

    EPA Science Inventory

    The fate of aromatic amines in soils and sediments is dominated by irreversible binding through nucleophilic addition and oxidative radical coupling. Despite the common occurrence of the aromatic amine functional group in organic chemicals, the molecular properties useful for pr...

  7. Base-Controlled Cu-Catalyzed Tandem Cyclization/Alkynylation for the Synthesis of Indolizines.

    PubMed

    Oh, Kyung Hwan; Kim, Seong Min; Park, Sun Young; Park, Jin Kyoon

    2016-05-01

    A base-controlled Cu-catalyzed tandem cyclization/alkynylation of propargylic amines provides rapid access to functionalized indolizine derivatives under mild reaction conditions. The reaction first proceeded via a 5-endo-dig aminocupration, followed by a coupling between the copper-bound intermediate and alkynyl bromide, to afford the products in good to excellent yields. The successful tandem reaction is attributed to the unique property of the bases, DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) and MTBD (7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene used). PMID:27097044

  8. Asymmetric copper-catalyzed C-N cross-couplings induced by visible light.

    PubMed

    Kainz, Quirin M; Matier, Carson D; Bartoszewicz, Agnieszka; Zultanski, Susan L; Peters, Jonas C; Fu, Gregory C

    2016-02-12

    Despite a well-developed and growing body of work in copper catalysis, the potential of copper to serve as a photocatalyst remains underexplored. Here we describe a photoinduced copper-catalyzed method for coupling readily available racemic tertiary alkyl chloride electrophiles with amines to generate fully substituted stereocenters with high enantioselectivity. The reaction proceeds at -40°C under excitation by a blue light-emitting diode and benefits from the use of a single, Earth-abundant transition metal acting as both the photocatalyst and the source of asymmetric induction. An enantioconvergent mechanism transforms the racemic starting material into a single product enantiomer. PMID:26912852

  9. Enantioselective Rh(I)-Catalyzed Addition of Arylboronic Acids to Cyclic Ketimines.

    PubMed

    Kong, Jongrock; McLaughlin, Mark; Belyk, Kevin; Mondschein, Ryan

    2015-11-20

    A method for the enantioselective synthesis of chiral α-tertiary amines via Rh-catalyzed 1,2-addition of arylboronic acids to cyclic ketimines is described. The products are efficiently accessed in good yields and excellent enantioselectivities using a commercially available chiral ligand. The reaction scope includes vinyl, aryl, and heteroarylboronic acids with yields ranging from 40% to 99% and enantiomeric excesses from 88% to 99%. Conversion of an addition product into an α,α-diaryl-substituted amino acid is also demonstrated.

  10. Palladium(II)-Catalyzed Enantioselective Synthesis of α-(Trifluoromethyl)arylmethylamines.

    PubMed

    Johnson, Thomas; Luo, Bo; Lautens, Mark

    2016-06-17

    We describe a method for the synthesis of α-(trifluoromethyl)arylmethylamines that consists of the palladium(II)-catalyzed addition of arylboroxines to imines derived from trifluoroacetaldehyde. Palladium acetate is used as a catalyst with electron-neutral or electron-rich arylboroxines, and it was found that addition of an ammonium or silver salt was crucial to promote the reaction of electron-poor boroxines. With (S)-t-Bu-PyOX as the chiral ligand, this method delivers a variety of α-trifluoromethylated amines in 57-91% yield and with greater than 92% ee in most cases. PMID:27246788

  11. Practical synthesis of pyrazoles via a copper-catalyzed relay oxidation strategy.

    PubMed

    Tang, Xiaodong; Huang, Liangbin; Yang, Jidan; Xu, Yanli; Wu, Wanqing; Jiang, Huanfeng

    2014-12-01

    Various 1,3- and 1,3,4-substituted pyrazoles are smoothly formed via copper-catalyzed cascade reactions of oxime acetates, amines and aldehydes. This relay oxidative process involves copper-promoted N-O bond cleavage and C-C/C-N/N-N bond formations to furnish pyrazolines, and sequential Cu-O2 system-involved oxidative dehydrogenation of pyrazolines to afford pyrazoles. This transformation provides a novel and versatile approach for the synthesis of pyrazoles, with an inexpensive copper catalyst and green oxidants. It is atom- and step-economical, and possesses a good functional group tolerance, as well as operational simplicity. PMID:25319768

  12. Cinchona Urea-Catalyzed Asymmetric Sulfa-Michael Reactions: The Brønsted Acid-Hydrogen Bonding Model.

    PubMed

    Grayson, Matthew N; Houk, K N

    2016-07-27

    The cinchona alkaloid-derived urea-catalyzed asymmetric conjugate addition of aromatic thiols to cycloalkenones was studied using density functional theory (DFT). Deprotonation of the thiol gives a protonated amine that activates the electrophile by Brønsted acid catalysis, while the urea group binds the nucleophilic thiolate by hydrogen bonding. These results demonstrate the generality of the Brønsted acid-hydrogen bonding transition state (TS) model for cinchona alkaloid catalysis that we recently showed to be favored over Wynberg's widely accepted ion pair-hydrogen bonding model and represent the first detailed mechanistic study of a cinchona urea-catalyzed reaction. The conformation of the catalyst methoxy group has a strong effect on the TS, an effect overlooked in previous mechanistic studies of reactions catalyzed by cinchona alkaloids.

  13. Isocyanate Cross-Linked Silica: Structurally Strong Aerogels

    NASA Technical Reports Server (NTRS)

    Leventis, Nicholas; Sotiriou-Leventis, Chariklia; Zhang, Guo-Hui; Rawashdeh, Abdel-Monem M.

    2002-01-01

    Molecular-level synergism between the silica nanoparticles of pre-formed monoliths and molecular cross-linkers inverts the relative host-guest roles in glass-polymer composites, leading to new strong low-density materials. Attempts to load gels with variable amounts of polyurethane precursors such as di-ISO and diol end-capped polybutylene adipate followed by heat treatment, washing, and supercritical drying led to opaque materials, somewhat stronger than silica but still quite brittle and much inferior to the materials described above. Direct mixing of a diisocyanate and an alcohol-free sol has been attempted recently by Yim et al. Reportedly, that procedure leads to week-long gelation times and requires an at least equally long aging period. In our attempt to add various amounts of di-ISO in a base-catalyzed sol in PC, we also noticed a week-long gelation time. The resulting aerogels were translucent but no less brittle than native silica. According to more recent studies, if propylene carbonate is replaced with acetone, it leads not only to shorter processing times, but also to much stronger gels that can tolerate loads in excess of 40 kg in the arrangement presented. We attribute that behavior to the lower viscosity of acetone, that allows faster diffusion of the di-ISO solution within the pores before di-ISO has time to react with the surface of silica. Further studies are underway to vary the chemical identity of the diisocyanate, as well as the composition and density of silica.

  14. Autoinduced catalysis and inverse equilibrium isotope effect in the frustrated Lewis pair catalyzed hydrogenation of imines.

    PubMed

    Tussing, Sebastian; Greb, Lutz; Tamke, Sergej; Schirmer, Birgitta; Muhle-Goll, Claudia; Luy, Burkhard; Paradies, Jan

    2015-05-26

    The frustrated Lewis pair (FLP)-catalyzed hydrogenation and deuteration of N-benzylidene-tert-butylamine (2) was kinetically investigated by using the three boranes B(C6F5)3 (1), B(2,4,6-F3-C6H2)3 (4), and B(2,6-F2-C6H3)3 (5) and the free activation energies for the H2 activation by FLP were determined. Reactions catalyzed by the weaker Lewis acids 4 and 5 displayed autoinductive catalysis arising from a higher free activation energy (2 kcal mol(-1)) for the H2 activation by the imine compared to the amine. Surprisingly, the imine reduction using D2 proceeded with higher rates. This phenomenon is unprecedented for FLP and resulted from a primary inverse equilibrium isotope effect. PMID:25877865

  15. Helical-Peptide-Catalyzed Enantioselective Michael Addition Reactions and Their Mechanistic Insights.

    PubMed

    Ueda, Atsushi; Umeno, Tomohiro; Doi, Mitsunobu; Akagawa, Kengo; Kudo, Kazuaki; Tanaka, Masakazu

    2016-08-01

    Helical peptide foldamer catalyzed Michael addition reactions of nitroalkane or dialkyl malonate to α,β-unsaturated ketones are reported along with the mechanistic considerations of the enantio-induction. A wide variety of α,β-unsaturated ketones, including β-aryl, β-alkyl enones, and cyclic enones, were found to be catalyzed by the helical peptide to give Michael adducts with high enantioselectivities (up to 99%). On the basis of X-ray crystallographic analysis and depsipeptide study, the amide protons, N(2)-H and N(3)-H, at the N terminus in the α-helical peptide catalyst were crucial for activating Michael donors, while the N-terminal primary amine activated Michael acceptors through the formation of iminium ion intermediates.

  16. Autoinduced catalysis and inverse equilibrium isotope effect in the frustrated Lewis pair catalyzed hydrogenation of imines.

    PubMed

    Tussing, Sebastian; Greb, Lutz; Tamke, Sergej; Schirmer, Birgitta; Muhle-Goll, Claudia; Luy, Burkhard; Paradies, Jan

    2015-05-26

    The frustrated Lewis pair (FLP)-catalyzed hydrogenation and deuteration of N-benzylidene-tert-butylamine (2) was kinetically investigated by using the three boranes B(C6F5)3 (1), B(2,4,6-F3-C6H2)3 (4), and B(2,6-F2-C6H3)3 (5) and the free activation energies for the H2 activation by FLP were determined. Reactions catalyzed by the weaker Lewis acids 4 and 5 displayed autoinductive catalysis arising from a higher free activation energy (2 kcal mol(-1)) for the H2 activation by the imine compared to the amine. Surprisingly, the imine reduction using D2 proceeded with higher rates. This phenomenon is unprecedented for FLP and resulted from a primary inverse equilibrium isotope effect.

  17. 40 CFR 721.639 - Amine aldehyde condensate.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Amine aldehyde condensate. 721.639... Substances § 721.639 Amine aldehyde condensate. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an amine aldehyde condensate (PMN...

  18. 40 CFR 721.639 - Amine aldehyde condensate.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Amine aldehyde condensate. 721.639... Substances § 721.639 Amine aldehyde condensate. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an amine aldehyde condensate (PMN...

  19. 40 CFR 721.639 - Amine aldehyde condensate.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Amine aldehyde condensate. 721.639... Substances § 721.639 Amine aldehyde condensate. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an amine aldehyde condensate (PMN...

  20. Solvent-Free Reductive Amination: An Organic Chemistry Experiment

    ERIC Educational Resources Information Center

    Goldstein, Steven W.; Cross, Amely V.

    2015-01-01

    The reductive amination reaction between an amine and an aldehyde or ketone is an important method to add an additional alkyl group to an amine nitrogen. In this experiment, students react a selection of benzylamines with aldehydes to form the corresponding imines. These imines are reduced with a mixture of "p"-toluenesulfonic acid…

  1. 40 CFR 721.647 - Alkoxylated alkyl amine (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Alkoxylated alkyl amine (generic). 721... Substances § 721.647 Alkoxylated alkyl amine (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an alkoxylated alkyl amine...

  2. 40 CFR 721.647 - Alkoxylated alkyl amine (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Alkoxylated alkyl amine (generic). 721... Substances § 721.647 Alkoxylated alkyl amine (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an alkoxylated alkyl amine...

  3. 40 CFR 721.10701 - Polyfluorinated alkyl amine (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Polyfluorinated alkyl amine (generic... Specific Chemical Substances § 721.10701 Polyfluorinated alkyl amine (generic). (a) Chemical substance and... polyfluorinated alkyl amine (PMN P-11-532) is subject to reporting under this section for the significant new...

  4. 40 CFR 721.647 - Alkoxylated alkyl amine (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkoxylated alkyl amine (generic). 721... Substances § 721.647 Alkoxylated alkyl amine (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an alkoxylated alkyl amine...

  5. 40 CFR 721.647 - Alkoxylated alkyl amine (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Alkoxylated alkyl amine (generic). 721... Substances § 721.647 Alkoxylated alkyl amine (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an alkoxylated alkyl amine...

  6. 40 CFR 721.647 - Alkoxylated alkyl amine (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Alkoxylated alkyl amine (generic). 721... Substances § 721.647 Alkoxylated alkyl amine (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an alkoxylated alkyl amine...

  7. 40 CFR 721.638 - Silyl amine, potassium salt (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Silyl amine, potassium salt (generic... Substances § 721.638 Silyl amine, potassium salt (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as silyl amine, potassium...

  8. 40 CFR 721.10046 - Polyaromatic amine phosphate (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Polyaromatic amine phosphate (generic... Specific Chemical Substances § 721.10046 Polyaromatic amine phosphate (generic). (a) Chemical substance and... amine phosphate (PMN P-02-747) is subject to reporting under this section for the significant new...

  9. 40 CFR 721.10046 - Polyaromatic amine phosphate (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Polyaromatic amine phosphate (generic... Specific Chemical Substances § 721.10046 Polyaromatic amine phosphate (generic). (a) Chemical substance and... amine phosphate (PMN P-02-747) is subject to reporting under this section for the significant new...

  10. 40 CFR 721.643 - Ethoxylated alcohol, phosphated, amine salt.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Ethoxylated alcohol, phosphated, amine... Specific Chemical Substances § 721.643 Ethoxylated alcohol, phosphated, amine salt. (a) Chemical substance... alcohol, phosphated, amine salt (PMN P-96-1478) is subject to reporting under this section for...

  11. 40 CFR 721.643 - Ethoxylated alcohol, phosphated, amine salt.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Ethoxylated alcohol, phosphated, amine... Specific Chemical Substances § 721.643 Ethoxylated alcohol, phosphated, amine salt. (a) Chemical substance... alcohol, phosphated, amine salt (PMN P-96-1478) is subject to reporting under this section for...

  12. 40 CFR 721.643 - Ethoxylated alcohol, phosphated, amine salt.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Ethoxylated alcohol, phosphated, amine... Specific Chemical Substances § 721.643 Ethoxylated alcohol, phosphated, amine salt. (a) Chemical substance... alcohol, phosphated, amine salt (PMN P-96-1478) is subject to reporting under this section for...

  13. 40 CFR 721.643 - Ethoxylated alcohol, phosphated, amine salt.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Ethoxylated alcohol, phosphated, amine... Specific Chemical Substances § 721.643 Ethoxylated alcohol, phosphated, amine salt. (a) Chemical substance... alcohol, phosphated, amine salt (PMN P-96-1478) is subject to reporting under this section for...

  14. 40 CFR 721.643 - Ethoxylated alcohol, phosphated, amine salt.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Ethoxylated alcohol, phosphated, amine... Specific Chemical Substances § 721.643 Ethoxylated alcohol, phosphated, amine salt. (a) Chemical substance... alcohol, phosphated, amine salt (PMN P-96-1478) is subject to reporting under this section for...

  15. 40 CFR 721.7286 - Amines, N-tallowalkyltripropylenetetra-, citrates.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Amines, N-tallowalkyltripropylenetetra... Specific Chemical Substances § 721.7286 Amines, N-tallowalkyltripropylenetetra-, citrates. (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified as amines,...

  16. 40 CFR 721.7286 - Amines, N-tallowalkyltripropylenetetra-, citrates.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Amines, N-tallowalkyltripropylenetetra... Specific Chemical Substances § 721.7286 Amines, N-tallowalkyltripropylenetetra-, citrates. (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified as amines,...

  17. 40 CFR 721.7285 - Amines, N-cocoalkyltrimethylenedi-, citrates.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Amines, N-cocoalkyltrimethylenedi... Specific Chemical Substances § 721.7285 Amines, N-cocoalkyltrimethylenedi-, citrates. (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified as amines,...

  18. 40 CFR 721.7285 - Amines, N-cocoalkyltrimethylenedi-, citrates.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Amines, N-cocoalkyltrimethylenedi... Specific Chemical Substances § 721.7285 Amines, N-cocoalkyltrimethylenedi-, citrates. (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified as amines,...

  19. 40 CFR 721.10069 - Ether amine phosphonate (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Ether amine phosphonate (generic). 721... Substances § 721.10069 Ether amine phosphonate (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as ether amine phosphonate (PMN...

  20. 40 CFR 721.10069 - Ether amine phosphonate (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Ether amine phosphonate (generic). 721... Substances § 721.10069 Ether amine phosphonate (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as ether amine phosphonate (PMN...

  1. Solid amine compounds as sorbents for carbon dioxide: A concept

    NASA Technical Reports Server (NTRS)

    Sutton, J. G.; Heimlich, P. F.; Tepper, E. H.

    1972-01-01

    Solid amine compounds were examined as possible absorbents for removal of carbon dioxide in life support systems of type which may be employed in high altitude aircraft, spacecraft, or submarines. Many solid amine compounds release absorbed carbon dioxide when heated in vacuum, therefore, when properly packaged spent amine compounds can be readily regenerated and put back into service.

  2. 40 CFR 721.750 - Aromatic amine compound.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Aromatic amine compound. 721.750... Substances § 721.750 Aromatic amine compound. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance aromatic amine compound (PMN P-86-334) is subject to reporting...

  3. 40 CFR 721.1625 - Alkylbenzene sulfonate, amine salt.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Alkylbenzene sulfonate, amine salt... Substances § 721.1625 Alkylbenzene sulfonate, amine salt. Link to an amendment published at 79 FR 34636, June... substance identified generically as alkylbenzene sulfonate, amine salt (PMN P-90-456) is subject...

  4. 40 CFR 721.6140 - Dialkyldithiophosphoric acid, aliphatic amine salt.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ..., aliphatic amine salt. 721.6140 Section 721.6140 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.6140 Dialkyldithiophosphoric acid, aliphatic amine salt. (a) Chemical... as a dialkyldithiophosphoric acid, aliphatic amine salt (P-90-1839) is subject to reporting...

  5. 40 CFR 721.640 - Amine substituted metal salts.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Amine substituted metal salts. 721.640... Substances § 721.640 Amine substituted metal salts. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substances identified generically as amine substituted metal...

  6. 40 CFR 721.640 - Amine substituted metal salts.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Amine substituted metal salts. 721.640... Substances § 721.640 Amine substituted metal salts. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substances identified generically as amine substituted metal...

  7. 40 CFR 721.638 - Silyl amine, potassium salt (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Silyl amine, potassium salt (generic... Substances § 721.638 Silyl amine, potassium salt (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as silyl amine, potassium...

  8. 40 CFR 721.9490 - Coco alklydimethyl amine salts (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Coco alklydimethyl amine salts... Specific Chemical Substances § 721.9490 Coco alklydimethyl amine salts (generic). (a) Chemical substances... coco alkyldimethyl amine salts (PMNs P-98-412/414/415/416/417) are subject to reporting under...

  9. 40 CFR 721.6140 - Dialkyldithiophosphoric acid, aliphatic amine salt.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ..., aliphatic amine salt. 721.6140 Section 721.6140 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.6140 Dialkyldithiophosphoric acid, aliphatic amine salt. (a) Chemical... as a dialkyldithiophosphoric acid, aliphatic amine salt (P-90-1839) is subject to reporting...

  10. 40 CFR 721.640 - Amine substituted metal salts.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Amine substituted metal salts. 721.640... Substances § 721.640 Amine substituted metal salts. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substances identified generically as amine substituted metal...

  11. 40 CFR 721.638 - Silyl amine, potassium salt (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Silyl amine, potassium salt (generic... Substances § 721.638 Silyl amine, potassium salt (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as silyl amine, potassium...

  12. 40 CFR 721.640 - Amine substituted metal salts.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Amine substituted metal salts. 721.640... Substances § 721.640 Amine substituted metal salts. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substances identified generically as amine substituted metal...

  13. 40 CFR 721.10569 - Tricyclic quaternary amine salt (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Tricyclic quaternary amine salt... Specific Chemical Substances § 721.10569 Tricyclic quaternary amine salt (generic). (a) Chemical substance... tricyclic quaternary amine salt (PMN P-08-471) is subject to reporting under this section for...

  14. 40 CFR 721.9490 - Coco alklydimethyl amine salts (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Coco alklydimethyl amine salts... Specific Chemical Substances § 721.9490 Coco alklydimethyl amine salts (generic). (a) Chemical substances... coco alkyldimethyl amine salts (PMNs P-98-412/414/415/416/417) are subject to reporting under...

  15. 40 CFR 721.10569 - Tricyclic quaternary amine salt (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Tricyclic quaternary amine salt... Specific Chemical Substances § 721.10569 Tricyclic quaternary amine salt (generic). (a) Chemical substance... tricyclic quaternary amine salt (PMN P-08-471) is subject to reporting under this section for...

  16. 40 CFR 721.640 - Amine substituted metal salts.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Amine substituted metal salts. 721.640... Substances § 721.640 Amine substituted metal salts. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substances identified generically as amine substituted metal...

  17. 40 CFR 721.6140 - Dialkyldithiophosphoric acid, aliphatic amine salt.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ..., aliphatic amine salt. 721.6140 Section 721.6140 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.6140 Dialkyldithiophosphoric acid, aliphatic amine salt. (a) Chemical... as a dialkyldithiophosphoric acid, aliphatic amine salt (P-90-1839) is subject to reporting...

  18. 40 CFR 721.6140 - Dialkyldithiophosphoric acid, aliphatic amine salt.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ..., aliphatic amine salt. 721.6140 Section 721.6140 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.6140 Dialkyldithiophosphoric acid, aliphatic amine salt. (a) Chemical... as a dialkyldithiophosphoric acid, aliphatic amine salt (P-90-1839) is subject to reporting...

  19. 40 CFR 721.6140 - Dialkyldithiophosphoric acid, aliphatic amine salt.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ..., aliphatic amine salt. 721.6140 Section 721.6140 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.6140 Dialkyldithiophosphoric acid, aliphatic amine salt. (a) Chemical... as a dialkyldithiophosphoric acid, aliphatic amine salt (P-90-1839) is subject to reporting...

  20. 40 CFR 721.638 - Silyl amine, potassium salt (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Silyl amine, potassium salt (generic... Substances § 721.638 Silyl amine, potassium salt (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as silyl amine, potassium...

  1. 40 CFR 721.9490 - Coco alklydimethyl amine salts (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Coco alklydimethyl amine salts... Specific Chemical Substances § 721.9490 Coco alklydimethyl amine salts (generic). (a) Chemical substances... coco alkyldimethyl amine salts (PMNs P-98-412/414/415/416/417) are subject to reporting under...

  2. 40 CFR 721.9490 - Coco alklydimethyl amine salts (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Coco alklydimethyl amine salts... Specific Chemical Substances § 721.9490 Coco alklydimethyl amine salts (generic). (a) Chemical substances... coco alkyldimethyl amine salts (PMNs P-98-412/414/415/416/417) are subject to reporting under...

  3. 40 CFR 721.638 - Silyl amine, potassium salt (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Silyl amine, potassium salt (generic... Substances § 721.638 Silyl amine, potassium salt (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as silyl amine, potassium...

  4. 40 CFR 721.9490 - Coco alklydimethyl amine salts (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Coco alklydimethyl amine salts... Specific Chemical Substances § 721.9490 Coco alklydimethyl amine salts (generic). (a) Chemical substances... coco alkyldimethyl amine salts (PMNs P-98-412/414/415/416/417) are subject to reporting under...

  5. Sulfonyl Azides as Precursors in Ligand-Free Palladium-Catalyzed Synthesis of Sulfonyl Carbamates and Sulfonyl Ureas and Synthesis of Sulfonamides.

    PubMed

    Chow, Shiao Y; Stevens, Marc Y; Odell, Luke R

    2016-04-01

    An efficient synthesis of sulfonyl carbamates and sulfonyl ureas from sulfonyl azides employing a palladium-catalyzed carbonylation protocol has been developed. Using a two-chamber system, sulfonyl azides, PdCl2, and CO gas, released ex situ from Mo(CO)6, were assembled to generate sulfonyl isocyanates in situ, and alcohols and aryl amines were exploited as nucleophiles to afford a broad range of sulfonyl carbamates and sulfonyl ureas. A protocol for the direct formation of substituted sulfonamides from sulfonyl azides and amines via nucleophilic substitution was also developed. PMID:26967791

  6. Application of a Palladium-Catalyzed C-H Functionalization/Indolization Method to Syntheses of cis-Trikentrin A and Herbindole B.

    PubMed

    Leal, Raul A; Bischof, Caroline; Lee, Youjin V; Sawano, Shota; McAtee, Christopher C; Latimer, Luke N; Russ, Zachary N; Dueber, John E; Yu, Jin-Quan; Sarpong, Richmond

    2016-09-19

    We describe herein formal syntheses of the indole alkaloids cis-trikentrin A and herbindole B from a common meso-hydroquinone intermediate prepared by a ruthenium-catalyzed [2+2+1+1] cycloaddition that has not been used previously in natural product synthesis. Key steps include a sterically demanding Buchwald-Hartwig amination as well as a unique C(sp(3) )-H amination/indole formation. Studies toward a selective desymmetrization of the meso-hydroquinone are also reported. PMID:27570932

  7. Metal-mediated oxidative amination of hydrocarbons

    SciTech Connect

    Harlan, E.W.; Blanco, F.B.; Cho, T.

    1993-12-31

    Two routes to high-valent imidometal species capable of transferring the nitrene functionality into hydrocarbon substrates have been examined. Transfer of the NH group from 1-aminopyridinium iodide to certain olefins in the presence of base and FeCl(TPP) forms the corresponding aziridine. This systems also aminates ethylbenzene. The three component systems RNH{sub 2}/PhI(OAc){sub 2}/MnCl(TPP) (R=Me,C{sub 6}H{sub 11}, Bu) aminate cyclohexane, ethylbenzene and several olefins. The system with R-Bu yields a high-valent Mn intermediate, tentatively identified as Mn(NBu)(TPP)Cl, which decomposes to Mn(III) over several hours in solution. In this system evidence for a metal-independent for a metal-independent amination pathway has also be obtained. For R=Me, C{sub 6}H{sub 11}, a novel C-N bond cleavage process, resulting in the known complex MnN(TPP), apparently competes with substrate amination. The results are consistent with stabilization of reactive Mn(NR)(TPP)Cl either via transfer of NR or formal elimination of RC.

  8. Atmospheric reactivity studies of aliphatic amines

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ambient studies of particulate matter have shown that alkyl amines are often present in particles in areas impacted by agricultural emissions. These locations include California’s Central Valley and Inland Empire and Utah’s Cache Valley. These compounds are not typically observed in airsheds that so...

  9. Extraction of carboxylic acids by amine extractants

    SciTech Connect

    Tamada, Janet Ayako; King, C.J.

    1989-01-01

    This work examines the chemistry of solvent extraction by long-chain amines for recovery of carboxylic acids from dilute aqueous solution. Long-chain amines act as complexing agents with the acid, which facilitates distribution of the acid into the organic phase. The complexation is reversible, allowing for recovery of the acid from the organic phase and regeneration of the extractant. Batch extraction experiments were performed to study the complexation of acetic, lactic, succinic, malonic, fumaric, and maleic acids with Alamine 336, an aliphatic, tertiary amine extractant, dissolved in various diluents. Results were interpreted by a ''chemical'' model, in which stoichiometric ratios of acid and amine molecules are assumed to form complexes in the solvent phase. From fitting of the extraction data, the stoichiometry of complexes formed and the corresponding equilibrium constants were obtained. The results of the model were combined with infrared spectroscopic experiments and results of past studies to analyze the chemical interactions that are responsible for extraction behavior. The information from the equilibrium studies was used to develop guidelines for large-scale staged extraction and regeneration schemes. A novel scheme, in which the diluent composition is shifted between extraction and regeneration, was developed which could achieve both high solute recovery and high product concentration. 169 refs., 57 figs., 15 tabs.

  10. The Synthesis of Methyl Salicylate: Amine Diazotization.

    ERIC Educational Resources Information Center

    Zanger, Murray; McKee, James R.

    1988-01-01

    Notes that this experiment takes safety and noncarcinogenic reactants into account. Demonstrates the use of diazonium salts for the replacement of an aromatic amine group by a phenolic hydroxyl. Involves two pleasant-smelling organic compounds, methyl anthranilate (grape) and methyl salicylate (oil of wintergreen). (MVL)

  11. Silica Fillers for elastomer Reinforement

    SciTech Connect

    Kohls, D.J.; Schaefer, D.W.

    2012-09-10

    This article summarizes recent work on the structure of precipitated silica used in the reinforcement of elastomers. Silica has a unique morphology, consisting of multiple structural levels that can be controlled through processing. The ability to control and characterize the multiple structures of precipitated silica is an example of morphological engineering for reinforcement applications. In this summary of some recent research efforts using precipitated silica, small-angle scattering techniques are described and their usefulness for determining the morphology of silica in terms of primary particles, aggregates, and agglomerates are discussed. The structure of several different precipitated silica powders is shown as well as the mechanical properties of elastomers reinforced with these silica particles. The study of the mechanical properties of filled elastomer systems is a challenging and exciting topic for both fundamental science and industrial application. It is known that the addition of hard particulates to a soft elastomer matrix results in properties that do not follow a straightforward rule of mixtures. Research efforts in this area have shown that the properties of filled elastomers are influenced by the nature of both the filler and the matrix, as well as the interactions between them. Several articles have reviewed the influence of fillers like silica and carbon black on the reinforcement of elastomers. In general, the structure-property relationships developed for filled elastomers have evolved into the following major areas: Filler structure, hydrodynamic reinforcement, and interactions between fillers and elastomers.

  12. Interfacial engineering for silica nanocapsules.

    PubMed

    Wibowo, David; Hui, Yue; Middelberg, Anton P J; Zhao, Chun-Xia

    2016-10-01

    Silica nanocapsules have attracted significant interest due to their core-shell hierarchical structure. The core domain allows the encapsulation of various functional components such as drugs, fluorescent and magnetic nanoparticles for applications in drug delivery, imaging and sensing, and the silica shell with its unique properties including biocompatibility, chemical and physical stability, and surface-chemistry tailorability provides a protection layer for the encapsulated cargo. Therefore, significant effort has been directed to synthesize silica nanocapsules with engineered properties, including size, composition and surface functionality, for various applications. This review provides a comprehensive overview of emerging methods for the manufacture of silica nanocapsules, with a special emphasis on different interfacial engineering strategies. The review starts with an introduction of various manufacturing approaches of silica nanocapsules highlighting surface engineering of the core template nanomaterials (solid nanoparticles, liquid droplets, and gas bubbles) using chemicals or biomolecules which are able to direct nucleation and growth of silica at the boundary of two-phase interfaces (solid-liquid, liquid-liquid, and gas-liquid). Next, surface functionalization of silica nanocapsules is presented. Furthermore, strategies and challenges of encapsulating active molecules (pre-loading and post-loading approaches) in these capsular systems are critically discussed. Finally, applications of silica nanocapsules in controlled release, imaging, and theranostics are reviewed. PMID:27522646

  13. Double emulsions and colloidosomes-in-colloidosomes using silica-based Pickering emulsifiers.

    PubMed

    Williams, Mark; Armes, Steven P; Verstraete, Pierre; Smets, Johan

    2014-03-18

    Poly(ethylene imine) (PEI) has been adsorbed onto the surface of fumed silica particles at pH 10 in order to produce an effective "hybrid" Pickering emulsifier. Systematically increasing the PEI/silica mass ratio at a fixed silica concentration of 1.0% w/w modifies the silica particle surface and hence allows the formation of oil-in-water (o/w) Pickering emulsions prepared via homogenization of an aldehyde-rich multi-component fragrance oil (at 12,000 rpm for 2 min at 20 °C). Further increasing the PEI/silica mass ratio leads to phase inversion, producing water-in-oil (w/o) Pickering emulsions. Thus this approach allows formation of stable water-in-oil-in-water (w/o/w) double emulsions using two batches of hydrophilic and hydrophobic PEI/silica hybrid particles that differ only in their PEI/silica mass ratios prior to homogenization. Stable w/o/w double emulsions can be prepared with oil volume fractions ranging from 5 to 42%. Moreover, controlling the volume fraction of the w/o Pickering emulsion homogenized in the presence of an aqueous dispersion of the hydrophilic PEI/silica particles allows the mean diameter of the resulting oil droplets to be conveniently controlled between 20 and 160 μm. Fluorescence microscopy studies confirm that controlling the mean diameter of these oil droplets allows encapsulation of either single or multiple droplets within them. Although these double emulsions do not require cross-linking at either interface to withstand an alcohol challenge, epoxy-amine cross-linking between the physically-adsorbed PEI chains and either an oil-soluble or a water-soluble bisepoxy-based polymeric cross-linker can be achieved to produce novel colloidosomes-in-colloidosomes, which may offer payload retention benefits over conventional colloidosomes.

  14. New insights into the molecular-level control of silica mineralization by diatoms

    NASA Astrophysics Data System (ADS)

    Wallace, A. F.; Dove, P. M.

    2007-12-01

    microscopy with elements of modern materials chemistry, to directly measure the rate of amorphous silica nucleation on COOH, NH3+, and COOH / NH3+-terminated surfaces under controlled solution conditions. Our results provide new insights into the molecular-level control of silica mineralization in diatoms. We show that differences between substrate-specific nucleation rates are controlled largely by kinetic factors rather than thermodynamic drivers, and that amine-terminated surfaces are not capable of triggering the onset of silica deposition without the synergistic activity of neighboring negatively charged species on the surface or in solution (e.g. carboxyl or phosphoryl groups). In light of this result we conclude that sites on the organic matrix that have phosphate and amine moieties in close proximity serve not only as contact points between the constituent macromolecules in the matrix, but also as initial sites of silica deposition.

  15. "Gray Areas": Silica gels, amorphous silica and cryptocrystalline silica on fault surfaces

    NASA Astrophysics Data System (ADS)

    Rowe, C. D.; Kirkpatrick, J. D.; White, J. C.; Faber, C.; Caine, J. S.

    2012-12-01

    Silica gels, in the form of their solid-phase equivalents, are widely found in brittle fault zones and are commonly associated with mineral deposits. High- to moderate-velocity rotary friction experiments have produced silica gels on sliding surfaces coeval with dramatic slip weakening. In light of the latter, silica gel formation has been proposed as a potential mechanism of slip weakening during earthquakes in the shallow crust. However, low velocity sliding experiments have also produced significant amounts of amorphous material distributed throughout slipping layers, and dramatic weakening is not observed. Comparison of the products of laboratory experiments to geological examples is complicated by the diagenesis and lithification of silica gels. They may form hydrous and amorphous solids, hydrous crystalline solids, or dehydrate to quartz. In addition, the abundance and style of occurrence of these products in faults suggest that there are multiple origins for silica gels in faults. We review the mechanisms by which silica gels may form in fault zones and describe the solidification, crystallization and dehydration evolution of the silica. Analytical transmission electron microscope (TEM) observations of slip-surface silica deposits from the Corona Fault, San Francisco, the Dixie Valley Fault, Nevada, and the Olive Fault, Namibia typify the nano- to micro-structural evolution of the fault surface silica layers. We suggest criteria for identifying these materials in natural fault rocks. Some of these gels may form by comminution and hydrolization of silica-rich wall rocks, as has been observed in high-velocity experiments (Corona Fault). Others may form by depressurization and boiling of aqueous fluids, probably during fault valving (Olive Fault). Silica saturated hydrothermal fluids released during faulting may contribute in some cases (Dixie Valley Fault). Regardless of the mechanism of gel formation, the dramatic rheological weakening observed in friction

  16. Assessing Site-Isolation of Amine Groups on Aminopropyl-Functionalized SBA-15 Materials via Spectroscopic and Reactivity Probes

    SciTech Connect

    Hicks, Jason C; Dabestani, Reza T; Buchanan III, A C; Jones, Christopher W

    2008-01-01

    The average degree of separation and the accessibility of aminopropyl groups on SBA-15 silica materials prepared using different silane grafting approaches are compared. Three specific synthetic approaches are used: (1) the traditional grafting of 3-aminopropyltrimethoxysilane in toluene, (2) a protection/deprotection method using benzyl- or trityl-spacer groups, and (3) a cooperative dilution method where 3-aminopropyltrimethoxysilane and methyltrimethoxysilane are co-condensed on the silica surface as a silane mixture. The site-isolation and accessibility of the amine groups are probed via three methods: (a) evaluation of pyrene groups adsorbed onto the solids using fluorescence spectroscopy, (b) the reactions of chlorodimethyl(2,3,4,5-tetramethyl-2,4-cyclopentadien-1-yl)silane (Cp'Si(Me){sub 2}Cl) and chloro(cyclopenta-2,4-dienyl)dimethylsilane (CpSi(Me){sub 2}Cl) with the tethered amine sites, and (c) comparison of the reactivity of zirconium constrained-geometry-inspired catalysts (CGCs) prepared using the Cp'Si(Me){sub 2}-modified aminosilicas in the catalytic polymerization of ethylene to produce poly(ethylene). The spectroscopic probe of site-isolation suggests that both the protection/deprotection method and the cooperative dilution method yield similarly isolated amine sites that are markedly more isolated than sites on traditional aminosilica. In contrast, both reactivity probes show that the protection/deprotection strategy leads to more uniformly accessible amine groups. It is proposed that the reactivity probes are more sensitive tests for accessibility and site-isolation in this case.

  17. Hydroxyatrazine N-Ethylaminohydrolase (AtzB): an Amidohydrolase Superfamily Enzyme Catalyzing Deamination and Dechlorination▿

    PubMed Central

    Seffernick, Jennifer L.; Aleem, Asma; Osborne, Jeffrey P.; Johnson, Gilbert; Sadowsky, Michael J.; Wackett, Lawrence P.

    2007-01-01

    Hydroxyatrazine [2-(N-ethylamino)-4-hydroxy-6-(N-isopropylamino)-1,3,5-triazine] N-ethylaminohydrolase (AtzB) is the sole enzyme known to catalyze the hydrolytic conversion of hydroxyatrazine to N-isopropylammelide. AtzB, therefore, serves as the point of intersection of multiple s-triazine biodegradative pathways and is completely essential for microbial growth on s-triazine herbicides. Here, atzB was cloned from Pseudomonas sp. strain ADP and its product was purified to homogeneity and characterized. AtzB was found to be dimeric, with subunit and holoenzyme molecular masses of 52 kDa and 105 kDa, respectively. The kcat and Km of AtzB with hydroxyatrazine as a substrate were 3 s−1 and 20 μM, respectively. Purified AtzB had a 1:1 zinc-to-subunit stoichiometry. Sequence analysis revealed that AtzB contained the conserved mononuclear amidohydrolase superfamily active-site residues His74, His76, His245, Glu248, His280, and Asp331. An intensive in vitro investigation into the substrate specificity of AtzB revealed that 20 of the 51 compounds tested were substrates for AtzB; this allowed for the identification of specific substrate structural features required for catalysis. Substrates required a monohydroxylated s-triazine ring with a minimum of one primary or secondary amine substituent and either a chloride or amine leaving group. AtzB catalyzed both deamination and dechlorination reactions with rates within a range of one order of magnitude. This differs from AtzA and TrzN, which do not catalyze deamination reactions, and AtzC, which is not known to catalyze dechlorination reactions. PMID:17660279

  18. Gold-Catalyzed Synthesis of Heterocycles

    NASA Astrophysics Data System (ADS)

    Arcadi, Antonio

    2014-04-01

    The following sections are included: * Introduction * Synthesis of Heterocycles via Gold-Catalyzed Heteroatom Addition to Unsaturated C-C Bonds * Synthesis of Heterocyclic Derivatives through Gold-Catalyzed Cyclization of Polyunsaturated Compounds * Synthesis of Heterocyclic Compounds via α-Oxo Gold Carbenoid * Synthesis of Heterocyclic Derivatives through Gold-Catalyzed Cycloaddition Reactions * Synthesis of Heterocyclic Derivatives through Gold-Catalyzed Activation of Carbonyl Groups and Alcohols * Synthesis of Heterocyclic Compounds through Gold-Mediated C-H Bond Functionalization * Gold-Catalyzed Domino Cyclization/Oxidative Coupling Reactions * Conclusions * References

  19. Copper-catalyzed azide alkyne cycloaddition polymer networks

    NASA Astrophysics Data System (ADS)

    Alzahrani, Abeer Ahmed

    The click reaction concept, introduced in 2001, has since spurred the rapid development and reexamination of efficient, high yield reactions which proceed rapidly under mild conditions. Prior to the discovery of facile copper catalysis in 2002, the thermally activated azide-alkyne or Huisgen cycloaddition reaction was largely ignored following its discovery in large part due to its slow kinetics, requirement for elevated temperature and limited selectivity. Now, arguably, the most prolific and capable of the click reactions, the copper-catalyzed azide alkyne cycloaddition (CuAAC) reaction is extremely efficient and affords exquisite control of the reaction. The orthogonally and chemoselectivity of this reaction enable its wide utility across varied scientific fields. Despite numerous inherent advantages and widespread use for small molecule synthesis and solution-based polymer chemistry, it has only recently and rarely been utilized to form polymer networks. This work focuses on the synthesis, mechanisms, and unique attributes of the CuAAC reaction for the fabrication of functional polymer networks. The photo-reduction of a series of copper(II)/amine complexes via ligand metal charge transfer was examined to determine their relative efficiency and selectivity in catalyzing the CuAAC reaction. The aliphatic amine ligands were used as an electron transfer species to reduce Cu(II) upon irradiation with 365 nm light while also functioning as an accelerating agent and as protecting ligands for the Cu(I) that was formed. Among the aliphatic amines studied, tertiary amines such as triethylamine (TEA), tetramethyldiamine (TMDA), N,N,N',N",N"-pentamethyldiethylenetriamine (PMDTA), and hexamethylenetetramine (HMTETA) were found to be the most effective. The reaction kinetics were accelerated by increasing the PMDETA : Cu(II) ratio with a ratio of ligand to Cu(II) of 4:1 yielding the maximum conversion in the shortest time. The sequential and orthogonal nature of the photo

  20. Investigations Concerning the Syntheses of TADDOL-Derived Secondary Amines and Their Use To Access Novel Chiral Organocatalysts.

    PubMed

    Gratzer, Katharina; Waser, Mario

    2012-12-01

    A structurally carefully diversified library of novel TADDOL-derived chiral secondary amines was synthesized and investigated for their applicability to obtain new organocatalysts like chiral Lewis bases and chiral phase-transfer catalysts. The scope and limitations of the developed syntheses routes to access these catalysts as well their catalytic performance in different benchmark reactions were systematically investigated. The most powerful of the catalysts prepared was found to be highly useful for the phase-transfer catalyzed α-alkylation of glycine Schiff base (high yields and up to 93% ee). PMID:25339781

  1. Use of a New Spirophosphine to Achieve Catalytic Enantioselective [4+1] Annulations of Amines with Allenes to Generate Dihydropyrroles

    PubMed Central

    Kramer, Søren; Fu, Gregory C.

    2015-01-01

    Due in part to the common occurrence of five-membered nitrogen heterocycles in bioactive molecules, the discovery of methods for the enantioselective synthesis of such structures is a useful endeavor. Building on a single example by Tong of a phosphine-catalyzed [4+1] annulation of an amine with an allene that furnished an achiral dihydropyrrole in 22% yield, we have developed, with the aid of a new chiral spirophosphine catalyst, a method with increased utility, specifically, improved yield, enhanced scope (the use of γ-substituted allenes), and good ee. The enantioenriched dihydropyrrole products can be transformed into other interesting families of compounds with very good stereoselectivity. PMID:25780940

  2. Silaffins in Silica Biomineralization and Biomimetic Silica Precipitation

    PubMed Central

    Lechner, Carolin C.; Becker, Christian F. W.

    2015-01-01

    Biomineralization processes leading to complex solid structures of inorganic material in biological systems are constantly gaining attention in biotechnology and biomedical research. An outstanding example for biomineral morphogenesis is the formation of highly elaborate, nano-patterned silica shells by diatoms. Among the organic macromolecules that have been closely linked to the tightly controlled precipitation of silica in diatoms, silaffins play an extraordinary role. These peptides typically occur as complex posttranslationally modified variants and are directly involved in the silica deposition process in diatoms. However, even in vitro silaffin-based peptides alone, with and without posttranslational modifications, can efficiently mediate biomimetic silica precipitation leading to silica material with different properties as well as with encapsulated cargo molecules of a large size range. In this review, the biomineralization process of silica in diatoms is summarized with a specific focus on silaffins and their in vitro silica precipitation properties. Applications in the area of bio- and nanotechnology as well as in diagnostics and therapy are discussed. PMID:26295401

  3. Catalyzed oxidation for nanowire growth

    NASA Astrophysics Data System (ADS)

    Tai, Kaiping; Sun, Ke; Huang, Bo; Dillon, Shen J.

    2014-04-01

    A simple, low-cost and scalable route to substrate-supported nanowire growth is reported based on catalyzed oxidation. The process shares common features with popular catalyzed nanowire growth techniques such as vapor-liquid-solid (VLS), vapor-solid-solid (VSS), or vapor-quasi-solid (VQS) that use catalyst nanoparticles to direct the deposition of reactants from the vapor phase. Catalyzed oxidation for nanowire growth (CONG) utilizes catalyzed anion (e.g. O2) reduction from the vapor phase and metal (e.g. Fe) oxidation from the substrate to produce oxide nanowires (e.g. Fe3O4). The approach represents a new class of nanowire growth methodology that may be applied to a broad range of systems. CONG does not require expensive chemical vapor deposition or physical vapor deposition equipment and can be implemented at intermediate temperatures (400-600 °C) in a standard laboratory furnace. This work also demonstrates a passive approach to catalyst deposition that allows the process to be implemented simply with no lithography or physical vapor deposition steps. This effort validates the general approach by synthesizing MnO, Fe3O4, WO3, MgO, TiO2, ZnO, ReO3, and NiO nanowires via CONG. The process produces single crystalline nanowires that can be grown to high aspect ratio and as high-density nanowire forests. Applications of the as-grown Fe3O4 and ReO3 nanowires for lithium ion battery systems are demonstrated to display high areal energy density and power.

  4. Catalyzed oxidation for nanowire growth.

    PubMed

    Tai, Kaiping; Sun, Ke; Huang, Bo; Dillon, Shen J

    2014-04-11

    A simple, low-cost and scalable route to substrate-supported nanowire growth is reported based on catalyzed oxidation. The process shares common features with popular catalyzed nanowire growth techniques such as vapor-liquid-solid (VLS), vapor-solid-solid (VSS), or vapor-quasi-solid (VQS) that use catalyst nanoparticles to direct the deposition of reactants from the vapor phase. Catalyzed oxidation for nanowire growth (CONG) utilizes catalyzed anion (e.g. O2) reduction from the vapor phase and metal (e.g. Fe) oxidation from the substrate to produce oxide nanowires (e.g. Fe3O4). The approach represents a new class of nanowire growth methodology that may be applied to a broad range of systems. CONG does not require expensive chemical vapor deposition or physical vapor deposition equipment and can be implemented at intermediate temperatures (400-600 °C) in a standard laboratory furnace. This work also demonstrates a passive approach to catalyst deposition that allows the process to be implemented simply with no lithography or physical vapor deposition steps. This effort validates the general approach by synthesizing MnO, Fe3O4, WO3, MgO, TiO2, ZnO, ReO3, and NiO nanowires via CONG. The process produces single crystalline nanowires that can be grown to high aspect ratio and as high-density nanowire forests. Applications of the as-grown Fe3O4 and ReO3 nanowires for lithium ion battery systems are demonstrated to display high areal energy density and power.

  5. Improvement of thermal stability of polypropylene using DOPO-immobilized silica nanoparticles

    PubMed Central

    Dong, Quanxiao; Ding, Yanfen; Wen, Bin; Wang, Feng; Dong, Huicong; Zhang, Shimin

    2014-01-01

    After the surface silylation with 3-methacryloxypropyltrimethoxysilane, silica nanoparticles were further modified by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). The immobilization of DOPO on silica nanoparticles was confirmed by Fourier transform infrared spectroscopy, UV–visible spectroscopy, magic angle spinning nuclear magnetic resonance, and thermogravimetric analysis. By incorporating the DOPO-immobilized silica nanoparticles (5 wt%) into polypropylene matrix, the thermal oxidative stability exhibited an improvement of 62 °C for the half weight loss temperature, while that was only 26 °C increment with incorporation of virgin silica nanoparticles (5 wt%). Apparent activation energies of the polymer nanocomposites were estimated via Flynn–Wall–Ozawa method. It was found that the incorporation of DOPO-immobilized silica nanoparticles improved activation energies of the degradation reaction. Based on the results, it was speculated that DOPO-immobilized silica nanoparticles could inhibit the degradation of polypropylene and catalyze the formation of carbonaceous char on the surface. Thus, thermal stability was significantly improved. PMID:24729654

  6. Synthesis of quinoxalines or quinolin-8-amines from N-propargyl aniline derivatives employing tin and indium chlorides.

    PubMed

    Aichhorn, Stefan; Himmelsbach, Markus; Schöfberger, Wolfgang

    2015-09-28

    Pyrazino compounds such as quinoxalines are 1,4-diazines with widespread occurrence in nature. Quinolin-8-amines are isomerically related and valuable scaffolds in organic synthesis. Herein, we present intramolecular main group metal Lewis acid catalyzed formal hydroamination as well as hydroarylation methodology using mono-propargylated aromatic ortho-diamines. The annulations can be conducted utilizing equal aerobic conditions with either stannic chloride or indium(iii) chloride and represent primary examples for main group metal catalyzed 6-exo-dig and 6-endo-dig, respectively, cyclizations in such settings. Both types of reactions can also be utilized in a one-pot manner starting from ortho-nitro N-propargyl anilines using stoichiometric amounts SnCl2·2H2O or In powder. Mechanistic considerations are presented regarding the substituent-depending regioselectivity.

  7. The influence of applied silica nanoparticles on a bio-renewable castor oil based polyurethane nanocomposite and its physicochemical properties.

    PubMed

    Seeni Meera, Kamal Mohamed; Murali Sankar, Rajavelu; Paul, Jaya; Jaisankar, Sellamuthu N; Mandal, Asit Baran

    2014-05-28

    Novel bio-renewable castor oil based polyurethane (PU)-silica nanocomposite films were prepared using castor oil, 1,6-hexamethylene diisocyanate and dibutyltin dilaurate in tetrahydrofuran at room temperature. ATR-FTIR spectra confirm the formation of polyurethane and the presence of silica nanoparticles in the polyurethane matrix. The increase of Si nanoparticle content shifts the peak position of N-H and C[double bond, length as m-dash]O (both hydrogen and non-hydrogen bonded) groups present in the polyurethane structure. Furthermore, Raman spectra confirmed the urethane-amide interaction present in the polyurethane-silica nanocomposites. (29)Si CP/MAS NMR spectra evidence the formation and the presence of completely condensed SiO2 species in the polyurethane nanocomposite films. The incorporation of silica nanoparticles increases the thermal stability of the above-mentioned polyurethane films, which can be seen from the increase in activation energy (Ea) values of the degradation process. The Ea values at two stages (Tmax1 and Tmax2) of the degradation process are 133, 139 and 157, 166 kJ mol(-1) for PU control and PU-5AMS (5 wt% amine modified silica nanoparticles), respectively. DSC results prove the interfacial interaction present between silica nanoparticles and the polyurethane hard segment, which decreases the melting temperature. Optical transmittance of the polyurethane films decreased with increasing silica content due to the scattering at the interfaces between the silica nanoparticles and polyurethane. It is interesting to note that the presence of silica nanoparticles gives reinforcement to polyurethane film, thereby increasing the storage modulus up to 24% for PU-5AMS. FE-SEM and HR-TEM images confirm the presence of silica nanoparticles in the polyurethane matrix.

  8. Quaternary amines as nitrosamine precursors: a role for consumer products?

    PubMed

    Kemper, Jerome M; Walse, Spencer S; Mitch, William A

    2010-02-15

    Nitrosamine formation has been associated with wastewater-impacted waters, but specific precursors within wastewater effluents have not been identified. Experiments indicated that nitrosamines form in low yields from quaternary amines, and that the nitrosamines form from the quaternary amines themselves, not just lower order amine impurities. Polymeric and benzylated quaternary amines were more potent precursors than monomeric quaternary alkylamines. Pretreatment of quaternary amines with ozone or free chlorine, which deactivate lower order amine impurities, did not significantly reduce nitrosamine formation. The nitrosamine formation pathway is unclear but experiments indicated that transformation of quaternary amines to lower order amine precursors via Hofmann elimination was not involved. Experiments suggest that the pathway may involve quaternary amine degradation by amidogen or chloramino radicals formed from chloramines. Quaternary amines are significant constituents of consumer products, including shampoos, detergents, and fabric softeners. Although quaternary amines may be removed by sedimentation during wastewater treatment, their importance should be evaluated on a case-by-case basis. The high loadings from consumer products may enable the portion not removed to serve as precursors. PMID:20085252

  9. Hierarchical meso-macroporous silica grafted with glyoxyl groups: opportunities for covalent immobilization of enzymes.

    PubMed

    Bernal, Claudia; Urrutia, Paulina; Illanes, Andrés; Wilson, Lorena

    2013-06-25

    Hierarchical meso-macroporous silica (average mesopore diameter 20 nm) was synthesized and chemically modified to be used as a support for the immobilization of lipases from Candida antarctica B and Alcaligenes sp. and β-galactosidases from Bacillus circulans and Aspergillus oryzae. Catalytic activities and thermal stabilities of enzymes immobilized by multipoint covalent attachment in silica derivatized with glyoxyl groups were compared with those immobilized in glyoxyl-agarose, assessing biocatalyst performance under non-reactive conditions in aqueous medium. In the case of A. oryzae β-galactosidase and Alcaligenes sp. lipase, an additional step of amination was needed to improve immobilization yield. Specific activities of lipases immobilized in glyoxyl-silica were high (232 and 62 IU per gram, for C. antarctica B and Alcaligenes sp. respectively); thermal stabilities were higher than those immobilized in glyoxyl-agarose. Although in the case of β-galactosidases from B. circulans and A. oryzae, the specific activities (250 and 310 IU per gram, respectively) were lower than the ones obtained with glyoxyl-agarose, expressed activities were similar to values previously reported. Thermal stabilities of both β-galactosidases immobilized in glyoxyl-silica were higher than when glyoxyl-agarose was used as support. Results indicate that hierarchical meso-macroporous silica is a versatile support for the production of robust biocatalysts.

  10. Bifunctional small molecules are biomimetic catalysts for silica synthesis at neutral pH.

    PubMed

    Roth, Kristian M; Zhou, Yan; Yang, Wenjun; Morse, Daniel E

    2005-01-12

    Silicatein is an enzyme isolated from the biosilica produced by the marine demosponge, Tethya aurantia. Once isolated from the sponge, silicatein can be used in vitro to catalyze the hydrolysis and direct polycondensation of a wide variety of alkoxide, ionic, and organometallic precursors to the corresponding chalcogens at standard temperature and pressure and neutral pH. On the basis of these results, an array of small molecules that mimic the unique physiochemical environment found in the enzyme active site was investigated for catalytic activity in the formation of silica from silicon alkoxides at neutral pH. The most successful of these biomimetic catalysts (cysteamine) was used to encapsulate firefly luciferase, green and blue fluorescent proteins (GFP, BFP), and Escherichia coli cells expressing GFP in silica matrixes. The benign conditions required for the catalysis of synthesis of these silica composites does not impair the activities of the encapsulated enzyme, fluorescent proteins, or live cells as shown by fluorescence measurements. In conjunction with microcontact printing, this biomimetically catalyzed encapsulation method has been used to produce patterned functional arrays of silica nanoparticulate composite materials.

  11. Recent developments in silica sol-gel anti-reflection (AR) coatings

    SciTech Connect

    Sermon, P.A.; Vong, M.S.W.; Bazin, N.; Badheka, R.; Spriggs, D.

    1995-12-31

    Silica sol-gel anti-reflective (AR) coatings have been investigated with particular reference to their laser induced damage threshold (LIDT) when subjected to irradiation from a Nd pulse laser at 1,064nm. Coatings (whose thickness was optimized for minimum reflection at 1,064nm) were deposited by spinning silica sols (average particle size 15nm) produced formed by the base (ammonium hydroxide) catalyzed hydrolysis/condensation of TEOS in ethanol. Addition of polyethylene glycols (PEGs) increased the size of the colloidal silica particles and also induced some particle aggregation in the sol, unlike a similar chain length diol. Increases in the LIDT of the coatings possibly depend upon the impurity levels, the wettability of the substrate and the presence of PEG. LIDT improvements may be obtained by control of substrate and coating surface wettability, hydrophilicity and surface chemistry.

  12. Metabolism and Biomarkers of Heterocyclic Aromatic Amines in Molecular Epidemiology Studies: Lessons Learned from Aromatic Amines

    PubMed Central

    2011-01-01

    Aromatic amines and heterocyclic aromatic amines (HAAs) are structurally related classes of carcinogens that are formed during the combustion of tobacco or during the high-temperature cooking of meats. Both classes of procarcinogens undergo metabolic activation by N-hydroxylation of the exocyclic amine group, to produce a common proposed intermediate, the arylnitrenium ion, which is the critical metabolite implicated in toxicity and DNA damage. However, the biochemistry and chemical properties of these compounds are distinct and different biomarkers of aromatic amines and HAAs have been developed for human biomonitoring studies. Hemoglobin adducts have been extensively used as biomarkers to monitor occupational and environmental exposures to a number of aromatic amines; however, HAAs do not form hemoglobin adducts at appreciable levels and other biomarkers have been sought. A number of epidemiologic studies that have investigated dietary consumption of well-done meat in relation to various tumor sites reported a positive association between cancer risk and well-done meat consumption, although some studies have shown no associations between well-done meat and cancer risk. A major limiting factor in most epidemiological studies is the uncertainty in quantitative estimates of chronic exposure to HAAs and, thus, the association of HAAs formed in cooked meat and cancer risk has been difficult to establish. There is a critical need to establish long-term biomarkers of HAAs that can be implemented in molecular epidemioIogy studies. In this review article, we highlight and contrast the biochemistry of several prototypical carcinogenic aromatic amines and HAAs to which humans are chronically exposed. The biochemical properties and the impact of polymorphisms of the major xenobiotic-metabolizing enzymes on the biological effects of these chemicals are examined. Lastly, the analytical approaches that have been successfully employed to biomonitor aromatic amines and HAAs, and

  13. Silica Polyamine Composites: New Supramolecular Materials for Cation and Anion Recovery and Remediation

    SciTech Connect

    Hughes, Mark; Miranda, Paul; Nielsen, Daniel J.; Rosenberg, Edward; Gobetto, Roberto; Viale, Alessandra; Burton, Sarah D.

    2006-03-01

    The surface coverage of amorphous silica gels used in the synthesis of silica polyamine composites has been investigated by 29Si NMR. By diluting the polyamine anchor silane, chloropropyl trichlorosilane, with methyl trichlorosilane it was found that surface coverage could be markedly improved for a range of amine polymers after grafting to the silica surface. The commensurate decrease in the number of anchor points and increase in the number of free amines results in an increase in metal capacity and/or an improvement in capture kinetics. Solid state CPMAS-13C NMR has been employed to investigate the structure and metal ion binding of a series of these composite materials. It is reported that the highly branched polymer, poly(ethyleneimine) (PEI) exhibits much broader 13C NMR resonances than the linear polymers poly(allylamine) (PAA) and poly(vinylamine) (PVA). These results are understood in terms of the low energy conformations calculated from molecular modeling studies. Three new applications of the technology are also presented: (1) separation of lanthanides as a group from ferric ion and all other divalent ions; (2) a multi step process for recovering and concentrating the valuable metals in acid mine drainage; (3) a process for removing low level arsenic and selenium in the presence of sulfate using immobilized cations on the composite materials.

  14. Layer-by-Layer Templated Assembly of Silica at the Nanoscale

    SciTech Connect

    Hinestrosa Salazar, Juan P; Sutton, Jonathan; Allison, David P; Doktycz, Mitchel John; Messman, Jamie M; Retterer, Scott T

    2013-01-01

    Bioinspired bottom-up assembly and layer-by-layer (LbL) construction of inorganic materials from lithographically defined organic templates enables the fabrication of nanostructured systems under mild temperature and pH conditions. Such processes open the door to low-impact manufacturing and facile recycling of hybrid materials for energy, biology, and information technologies. Here, templated LbL assembly of silica was achieved using a combination of electron beam lithography, chemical lift-off, and aqueous solution chemistry. Nanopatterns of lines, honeycomb-lattices, and dot arrays were defined in polymer resist using electron beam lithography. Following development, exposed areas of silicon were functionalized with a vapor deposited amine-silane monolayer. Silicic acid solutions of varying pH and salt content were reacted with the patterned organic amine-functional templates. Vapor treatment and solution reaction could be repeated, allowing LbL deposition. Conditions for the silicic acid deposition had a strong effect on thickness of each layer, and the morphology of the amorphous silica formed. Defects in the arrays of silica nanostructures were minor and do not affect the overall organization of the layers. The bioinspired method described here facilitates the bottom-up assembly of inorganic nanostructures defined in three dimensions and provides a path, via LbL processing, for the construction of layered hybrid materials under mild conditions.

  15. Development of a general non-noble metal catalyst for the benign amination of alcohols with amines and ammonia.

    PubMed

    Cui, Xinjiang; Dai, Xingchao; Deng, Youquan; Shi, Feng

    2013-03-11

    The N-alkylation of amines or ammonia with alcohols is a valuable route for the synthesis of N-alkyl amines. However, as a potentially clean and economic choice for N-alkyl amine synthesis, non-noble metal catalysts with high activity and good selectivity are rarely reported. Normally, they are severely limited due to low activity and poor generality. Herein, a simple NiCuFeOx catalyst was designed and prepared for the N-alkylation of ammonia or amines with alcohol or primary amines. N-alkyl amines with various structures were successfully synthesized in moderate to excellent yields in the absence of organic ligands and bases. Typically, primary amines could be efficiently transformed into secondary amines and N-heterocyclic compounds, and secondary amines could be N-alkylated to synthesize tertiary amines. Note that primary and secondary amines could be produced through a one-pot reaction of ammonia and alcohols. In addition to excellent catalytic performance, the catalyst itself possesses outstanding superiority, that is, it is air and moisture stable. Moreover, the magnetic property of this catalyst makes it easily separable from the reaction mixture and it could be recovered and reused for several runs without obvious deactivation.

  16. Silica/Polymer and Silica/Polymer/Fiber Composite Aerogels

    NASA Technical Reports Server (NTRS)

    Ou, Danny; Stepanian, Christopher J.; Hu, Xiangjun

    2010-01-01

    Aerogels that consist, variously, of neat silica/polymer alloys and silica/polymer alloy matrices reinforced with fibers have been developed as materials for flexible thermal-insulation blankets. In comparison with prior aerogel blankets, these aerogel blankets are more durable and less dusty. These blankets are also better able to resist and recover from compression . an important advantage in that maintenance of thickness is essential to maintenance of high thermal-insulation performance. These blankets are especially suitable as core materials for vacuum- insulated panels and vacuum-insulated boxes of advanced, nearly seamless design. (Inasmuch as heat leakage at seams is much greater than heat leakage elsewhere through such structures, advanced designs for high insulation performance should provide for minimization of the sizes and numbers of seams.) A silica/polymer aerogel of the present type could be characterized, somewhat more precisely, as consisting of multiply bonded, linear polymer reinforcements within a silica aerogel matrix. Thus far, several different polymethacrylates (PMAs) have been incorporated into aerogel networks to increase resistance to crushing and to improve other mechanical properties while minimally affecting thermal conductivity and density. The polymethacrylate phases are strongly linked into the silica aerogel networks in these materials. Unlike in other organic/inorganic blended aerogels, the inorganic and organic phases are chemically bonded to each other, by both covalent and hydrogen bonds. In the process for making a silica/polymer alloy aerogel, the covalent bonds are introduced by prepolymerization of the methacrylate monomer with trimethoxysilylpropylmethacrylate, which serves as a phase cross-linker in that it contains both organic and inorganic monomer functional groups and hence acts as a connector between the organic and inorganic phases. Hydrogen bonds are formed between the silanol groups of the inorganic phase and the

  17. Nanoparticle strategies for cancer therapeutics: Nucleic acids, polyamines, bovine serum amine oxidase and iron oxide nanoparticles (Review).

    PubMed

    Agostinelli, Enzo; Vianello, Fabio; Magliulo, Giuseppe; Thomas, Thresia; Thomas, T J

    2015-01-01

    Nanotechnology for cancer gene therapy is an emerging field. Nucleic acids, polyamine analogues and cytotoxic products of polyamine oxidation, generated in situ by an enzyme-catalyzed reaction, can be developed for nanotechnology-based cancer therapeutics with reduced systemic toxicity and improved therapeutic efficacy. Nucleic acid-based gene therapy approaches depend on the compaction of DNA/RNA to nanoparticles and polyamine analogues are excellent agents for the condensation of nucleic acids to nanoparticles. Polyamines and amine oxidases are found in higher levels in tumours compared to that of normal tissues. Therefore, the metabolism of polyamines spermidine and spermine, and their diamine precursor, putrescine, can be targets for antineoplastic therapy since these naturally occurring alkylamines are essential for normal mammalian cell growth. Intracellular polyamine concentrations are maintained at a cell type-specific set point through the coordinated and highly regulated interplay between biosynthesis, transport, and catabolism. In particular, polyamine catabolism involves copper-containing amine oxidases. Several studies showed an important role of these enzymes in developmental and disease-related processes in animals through the control of polyamine homeostasis in response to normal cellular signals, drug treatment, and environmental and/or cellular stress. The production of toxic aldehydes and reactive oxygen species (ROS), H2O2 in particular, by these oxidases suggests a mechanism by which amine oxidases can be exploited as antineoplastic drug targets. The combination of bovine serum amine oxidase (BSAO) and polyamines prevents tumour growth, particularly well if the enzyme has been conjugated with a biocompatible hydrogel polymer. The findings described herein suggest that enzymatically formed cytotoxic agents activate stress signal transduction pathways, leading to apoptotic cell death. Consequently, superparamagnetic nanoparticles or other

  18. Physico chemical properties of aminated tamarind xyloglucan.

    PubMed

    Simi, Chandroth Kalyad; Abraham, Tholath Emilia

    2010-12-01

    Tamarind xyloglucan (XG) has been functionalized with amino group, which forms irreversible hydrogels with blue fluorescence characteristics. Aminated xyloglucan (XG-NH2) at very low concentration (0.2%, w/v) in aqueous medium, forms self assembled spherical nano-particles of 60 nm size, where as at 7% (w/v), it formed a strong hydrogel. The bonding of amino group to the XG polymers was confirmed by FTIR spectra. The XG-NH2 has same solubility as XG. The XG showed a broad melting point around 78°C whereas XG-NH2 was at 115°C. In addition, aminated xyloglucan (XG-NH2) exhibited good thermal properties. The XG-NH2 shows better antimicrobial activity in comparison to chitosan. This modified xyloglucan has potential applications in the medical and biotronics field because it possesses biocompatibility, strong hydrogel behavior with very useful blue fluorescence.

  19. Catalytic dehydrogenation of amine borane complexes

    NASA Technical Reports Server (NTRS)

    Mohajeri, Nahid (Inventor); Tabatabaie-Raissi, Ali (Inventor)

    2007-01-01

    A method of generating hydrogen includes the steps of providing an amine borane (AB) complex, at least one hydrogen generation catalyst, and a solvent, and mixing these components. Hydrogen is generated. The hydrogen produced is high purity hydrogen suitable for PEM fuel cells. A hydrolytic in-situ hydrogen generator includes a first compartment that contains an amine borane (AB) complex, a second container including at least one hydrogen generation catalyst, wherein the first or second compartment includes water or other hydroxyl group containing solvent. A connecting network permits mixing contents in the first compartment with contents in the second compartment, wherein high purity hydrogen is generated upon mixing. At least one flow controller is provided for controlling a flow rate of the catalyst or AB complex.

  20. Catalytic dehydrogenation of amine borane complexes

    NASA Technical Reports Server (NTRS)

    Mohajeri, Nahid (Inventor); Tabatabaie-Raissi, Ali (Inventor); Bokerman, Gary (Inventor)

    2009-01-01

    A method of generating hydrogen includes the steps of providing an amine borane (AB) complex, at least one hydrogen generation catalyst, and a solvent, and mixing these components Hydrogen is generated. The hydrogen produced is high purity hydrogen suitable for PEM fuel cells. A hydrolytic in-situ hydrogen generator includes a first compartment that contains an amine borane (AB) complex, a second container including at least one hydrogen generation catalyst, wherein the first or second compartment includes water or other hydroxyl group containing solvent. A connecting network permits mixing contents in the first compartment with contents in the second compartment, wherein high purity hydrogen is generated upon mixing. At least one flow controller is provided for controlling a flow rate of the catalyst or AB complex.