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Sample records for alkene metathesis catalysts

  1. Alkene metathesis: the search for better catalysts.

    PubMed

    Deshmukh, Prashant H; Blechert, Siegfried

    2007-06-28

    Alkene metathesis catalyst development has made significant progress over recent years. Research in metathesis catalyst design has endeavoured to tackle three key issues: those of (i) catalyst efficiency and activity, (ii) substrate scope and selectivity--particularly stereoselective metathesis reactions--and (iii) the minimization of metal impurities and catalyst recycling. This article describes a brief history of metathesis catalyst development, followed by a survey of more recent research, with a particular emphasis on ruthenium catalysts.

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

    DOEpatents

    Schrodi, Yann

    2016-02-09

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

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

    DOEpatents

    Schrodi, Yann

    2013-07-09

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

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

    DOEpatents

    Schrodi, Yann

    2015-09-22

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

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

    DOEpatents

    Schrodi, Yann [Agoura Hills, CA

    2011-11-29

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

  6. Increased functionality of methyl oleate using alkene metathesis

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  7. Mesoporous Molecular Sieves Based Catalysts for Olefin Metathesis and Metathesis Polymerization

    NASA Astrophysics Data System (ADS)

    Balcar, Hynek; Čejka, Jiří

    Heterogeneous catalysts for olefin metathesis using different types of (i) siliceous mesoporous molecular sieves, and (ii) organized mesoporous alumina as supports are reported. The catalysts were prepared either by spreading of transition metal oxidic phase on the support surface or by immobilizing transition metal compounds (mostly organometallic) on the support. The activity of these catalysts in various types of metathesis reactions (i.e. alkene and diene metathesis, metathesis of unsaturated esters and ethers, RCM, ROMP and metathesis polymerization of alkynes) was described. The main advantages of these catalysts consist generally in their high activity and selectivity, easy separation of catalysts from reaction products and the preparation of products free of catalyst residue. The examples of pore size influence on the selectivity in metathesis reactions are also given.

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

    NASA Astrophysics Data System (ADS)

    Malacea, Raluca; Dixneuf, Pierre H.

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

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

    PubMed Central

    Lafaye, Kevin; Bosset, Cyril; Nicolas, Lionel

    2015-01-01

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

  10. Alkene Metalates as Hydrogenation Catalysts.

    PubMed

    Büschelberger, Philipp; Gärtner, Dominik; Reyes-Rodriguez, Efrain; Kreyenschmidt, Friedrich; Koszinowski, Konrad; Jacobi von Wangelin, Axel; Wolf, Robert

    2017-03-02

    First-row transition-metal complexes hold great potential as catalysts for hydrogenations and related reductive reactions. Homo- and heteroleptic arene/alkene metalates(1-) (M=Co, Fe) are a structurally distinct catalyst class with good activities in hydrogenations of alkenes and alkynes. The first syntheses of the heteroleptic cobaltates [K([18]crown-6)][Co(η(4) -cod)(η(2) -styrene)2 ] (5) and [K([18]crown-6)][Co(η(4) -dct)(η(4) -cod)] (6), and the homoleptic complex [K(thf)2 ][Co(η(4) -dct)2 ] (7; dct=dibenzo[a,e]cyclooctatetraene, cod=1,5-cyclooctadiene), are reported. For comparison, two cyclopentadienylferrates(1-) were synthesized according to literature procedures. The isolated and fully characterized monoanionic complexes were competent precatalysts in alkene hydrogenations under mild conditions (2 bar H2 , r.t., THF). Mechanistic studies by NMR spectroscopy, ESI mass spectrometry, and poisoning experiments documented the operation of a homogeneous mechanism, which was initiated by facile redox-neutral π-ligand exchange with the substrates followed by H2 activation. The substrate scope of the investigated precatalysts was also extended to polar substrates (ketones and imines).

  11. Cis-Selective Ring-Opening Metathesis Polymerization with Ruthenium Catalysts

    PubMed Central

    Keitz, Benjamin K.; Fedorov, Alexey; Grubbs, Robert H.

    2012-01-01

    Using a C-H activated, ruthenium-based metathesis catalyst, the cis selective ROMP of several monocyclic alkenes, as well as norbornene and oxanorbornene-type monomers is reported. The cis content of the isolated polymers depended heavily on monomer structure and temperature. By lowering the temperature, cis content as high as 96% could be obtained. PMID:22239675

  12. Molybdenum chloride catalysts for Z-selective olefin metathesis reactions

    NASA Astrophysics Data System (ADS)

    Koh, Ming Joo; Nguyen, Thach T.; Lam, Jonathan K.; Torker, Sebastian; Hyvl, Jakub; Schrock, Richard R.; Hoveyda, Amir H.

    2017-01-01

    The development of catalyst-controlled stereoselective olefin metathesis processes has been a pivotal recent advance in chemistry. The incorporation of appropriate ligands within complexes based on molybdenum, tungsten and ruthenium has led to reactivity and selectivity levels that were previously inaccessible. Here we show that molybdenum monoaryloxide chloride complexes furnish higher-energy (Z) isomers of trifluoromethyl-substituted alkenes through cross-metathesis reactions with the commercially available, inexpensive and typically inert Z-1,1,1,4,4,4-hexafluoro-2-butene. Furthermore, otherwise inefficient and non-stereoselective transformations with Z-1,2-dichloroethene and 1,2-dibromoethene can be effected with substantially improved efficiency and Z selectivity. The use of such molybdenum monoaryloxide chloride complexes enables the synthesis of representative biologically active molecules and trifluoromethyl analogues of medicinally relevant compounds. The origins of the activity and selectivity levels observed, which contradict previously proposed principles, are elucidated with the aid of density functional theory calculations.

  13. Thermally Stable, Latent Olefin Metathesis Catalysts

    PubMed Central

    Thomas, Renee M.; Fedorov, Alexey; Keitz, Benjamin K.

    2011-01-01

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

  14. Cross metathesis with hydroxamate and benzamide BOC-protected alkenes to access HDAC inhibitors and their biological evaluation highlighted intrinsic activity of BOC-protected dihydroxamates.

    PubMed

    Zwick, Vincent; Nurisso, Alessandra; Simões-Pires, Claudia; Bouchet, Samuel; Martinet, Nadine; Lehotzky, Attila; Ovadi, Judit; Cuendet, Muriel; Blanquart, Christophe; Bertrand, Philippe

    2016-01-01

    Conditions for the metathesis of alkenes in the convergent synthesis of HDAC inhibitors have been improved by continuous catalyst flow injection in the reaction media. Intermediate and target compounds obtained were tested for their ability to induce HDAC inhibition and tubulin acetylation, revealing the key role of the tert-butyloxycarbonyl (BOC) group for more HDAC6 selectivity. Molecular modelling added rationale for this BOC effect.

  15. General catalyst control of the monoisomerization of 1-alkenes to trans-2-alkenes.

    PubMed

    Larsen, Casey R; Erdogan, Gulin; Grotjahn, Douglas B

    2014-01-29

    After searching for the proper catalyst, the dual challenges of controlling the position of the double bond, and cis/trans-selectivity in isomerization of terminal alkenes to their 2-isomers are finally met in a general sense by mixtures of (C5Me5)Ru complexes 1 and 3 featuring a bifunctional phosphine. Typically, catalyst loadings of 1 mol % of 1 and 3 can be employed for the production of (E)-2-alkenes at 40-70 °C. Catalyst comprising 1 and 3 avoids more than any other known example the thermodynamic equilibration of alkene isomers, as the trans-2-alkenes of both nonfunctionalized and functionalized alkenes are generated.

  16. Tandem Ring-Opening-Ring-Closing Metathesis for Functional Metathesis Catalysts.

    PubMed

    Nagarkar, Amit A; Yasir, Mohammad; Crochet, Aurelien; Fromm, Katharina M; Kilbinger, Andreas F M

    2016-09-26

    Use of a tandem ring-opening-ring-closing metathesis (RORCM) strategy for the synthesis of functional metathesis catalysts is reported. Ring opening of 7-substituted norbornenes and subsequent ring-closing metathesis forming a thermodynamically stable 6-membered ring lead to a very efficient synthesis of new catalysts from commercially available Grubbs' catalysts. Hydroxy functionalized Grubbs' first- as well as third-generation catalysts have been synthesized. Mechanistic studies have been performed to elucidate the order of attack of the olefinic bonds. This strategy was also used to synthesize the ruthenium methylidene complex.

  17. Relay cross metathesis reactions of vinylphosphonates.

    PubMed

    Malla, Raj K; Ridenour, Jeremy N; Spilling, Christopher D

    2014-01-01

    Dimethyl (β-substituted) vinylphosphonates do not readily undergo cross metathesis reactions with Grubbs catalyst and terminal alkenes. However, the corresponding mono- or diallyl vinylphosphonate esters undergo facile cross metathesis reactions. The improved reactivity is attributed to a relay step in the cross metathesis reaction mechanism.

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

    PubMed Central

    2016-01-01

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

  19. Nonproductive events in ring-closing metathesis using ruthenium catalysts.

    PubMed

    Stewart, Ian C; Keitz, Benjamin K; Kuhn, Kevin M; Thomas, Renee M; Grubbs, Robert H

    2010-06-30

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

  20. Building Indenylidene-Ruthenium Catalysts for Metathesis Transformations

    NASA Astrophysics Data System (ADS)

    Clavier, Hervé; Nolan, Steven P.

    Ruthenium-mediated olefin metathesis has emerged as an indispensable tool in organic synthesis for the formation carbon-carbon double bonds, attested by the large number of applications for natural product synthesis. Among the numerous catalysts developed to mediate olefin metathesis transformations, ruthenium-indenylidene complexes are robust and powerful pre-catalysts. The discovery of this catalyst category was slightly muddled due to a first mis-assignment of the compound structure. This report provides an overview of the synthetic routes for the construction of the indenylidene pattern in ruthenium complexes. The parameters relating to the indenylidene moiety construction will be discussed as well as the mechanism of this formation

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

    PubMed

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

    2016-01-14

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

  2. Ru-Based Z-Selective Metathesis Catalysts with Modified Cyclometalated Carbene Ligands†

    PubMed Central

    Bronner, Sarah M.; Herbert, Myles B.; Patel, Paresma R.; Marx, Vanessa M.; Grubbs, Robert H.

    2014-01-01

    A series of cyclometalated Z-selective ruthenium olefin metathesis catalysts with alterations to the N-heterocyclic carbene (NHC) ligand were prepared. X-Ray crystal structures of several new catalysts were obtained, elucidating the structural features of this class of cyclometalated complexes. The metathesis activity of each stable complex was evaluated, and one catalyst, bearing geminal dimethyl backbone substitution, was found to be comparable to our best Z-selective metathesis catalyst to date. PMID:25346842

  3. Glycosyl-Templated Chiral Helix Stapling of Ethynylpyridine Oligomers by Alkene Metathesis between Inter-Pitch Side Chains.

    PubMed

    Abe, Hajime; Kayamori, Fumihiro; Inouye, Masahiko

    2015-06-22

    Ethynylpyridine polymers and oligomers consisting of 4-substituted pyridine rings linked by acetylene bonds at the 2- and 6-positions have been investigated. Ethynylpyridine oligomers covalently linked with a glycosyl chiral template form chiral helical complexes by intramolecular hydrogen bonding, in which the chirality of the template is translated to the helix. With a view to fixation of the chiral architecture, D/L-galactosyl- and D/L-mannosyl-linked ethynylpyridine oligomers have been developed with 4-(3-butenyloxy)pyridine units having alkene side chains. The helical structures are successfully stapled by alkene metathesis of the side chains. Subsequent removal of the chiral templates by acidolysis produces template-free stapled oligomers. The chiral, template-free, stapled oligomers show chiral helicity, which is resistant to polar solvents and heating.

  4. Catalyst system for the polymerization of alkenes to polyolefins

    DOEpatents

    Miller, Stephen A.; Bercaw, John E.

    2002-01-01

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

  5. Catalyst system for the polymerization of alkenes to polyolefins

    DOEpatents

    Miller, Stephen A.; Bercaw, John E.

    2004-02-17

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

  6. Highly active and efficient catalysts for alkoxycarbonylation of alkenes

    NASA Astrophysics Data System (ADS)

    Dong, Kaiwu; Fang, Xianjie; Gülak, Samet; Franke, Robert; Spannenberg, Anke; Neumann, Helfried; Jackstell, Ralf; Beller, Matthias

    2017-01-01

    Carbonylation reactions of alkenes constitute the most important industrial processes in homogeneous catalysis. Despite the tremendous progress in this transformation, the development of advanced catalyst systems to improve their activity and widen the range of feedstocks continues to be essential for new practical applications. Herein a palladium catalyst based on 1,2-bis((tert-butyl(pyridin-2-yl)phosphanyl)methyl)benzene L3 (pytbpx) is rationally designed and synthesized. Application of this system allows a general alkoxycarbonylation of sterically hindered and demanding olefins including all kinds of tetra-, tri- and 1,1-disubstituted alkenes as well as natural products and pharmaceuticals to the desired esters in excellent yield. Industrially relevant bulk ethylene is functionalized with high activity (TON: >1,425,000 TOF: 44,000 h-1 for initial 18 h) and selectivity (>99%). Given its generality and efficiency, we expect this catalytic system to immediately impact both the chemical industry and research laboratories by providing a practical synthetic tool for the transformation of nearly any alkene into a versatile ester product.

  7. Highly active and efficient catalysts for alkoxycarbonylation of alkenes

    PubMed Central

    Dong, Kaiwu; Fang, Xianjie; Gülak, Samet; Franke, Robert; Spannenberg, Anke; Neumann, Helfried; Jackstell, Ralf; Beller, Matthias

    2017-01-01

    Carbonylation reactions of alkenes constitute the most important industrial processes in homogeneous catalysis. Despite the tremendous progress in this transformation, the development of advanced catalyst systems to improve their activity and widen the range of feedstocks continues to be essential for new practical applications. Herein a palladium catalyst based on 1,2-bis((tert-butyl(pyridin-2-yl)phosphanyl)methyl)benzene L3 (pytbpx) is rationally designed and synthesized. Application of this system allows a general alkoxycarbonylation of sterically hindered and demanding olefins including all kinds of tetra-, tri- and 1,1-disubstituted alkenes as well as natural products and pharmaceuticals to the desired esters in excellent yield. Industrially relevant bulk ethylene is functionalized with high activity (TON: >1,425,000; TOF: 44,000 h−1 for initial 18 h) and selectivity (>99%). Given its generality and efficiency, we expect this catalytic system to immediately impact both the chemical industry and research laboratories by providing a practical synthetic tool for the transformation of nearly any alkene into a versatile ester product. PMID:28120947

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

    PubMed Central

    Martin, David; Marx, Vanessa M.

    2016-01-01

    A ruthenium complex bearing an “anti-Bredt” N-heterocyclic carbene was synthesized, characterized and evaluated as a catalyst for olefin metathesis. Good conversions were observed at room temperature for the formation of di- and tri-substituted olefins by ring-closing metathesis. It also allowed for the ring-opening metathesis polymerization of cyclooctadiene, as well as for the cross-metathesis of cis-1,4-diacetoxy-2-butene with allyl-benzene, with enhanced Z/E kinetic selectivity over classical NHC-based catalysts. PMID:27594819

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

    SciTech Connect

    Grubbs, Robert H

    2013-04-05

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

  10. Biopolymer-supported ionic-liquid-phase ruthenium catalysts for olefin metathesis.

    PubMed

    Clousier, Nathalie; Filippi, Alexandra; Borré, Etienne; Guibal, Eric; Crévisy, Christophe; Caijo, Fréderic; Mauduit, Marc; Dez, Isabelle; Gaumont, Annie-Claude

    2014-04-01

    Original ruthenium supported ionic liquid phase (SILP) catalysts based on alginates as supports were developed for olefin metathesis reactions. The marine biopolymer, which fulfills most of the requisite properties for a support such as widespread abundance, insolubility in the majority of organic solvents, a high affinity for ionic liquids, high chemical stability, biodegradability, low cost, and easy processing, was impregnated by [bmim][PF6 ] containing an ionically tagged ruthenium catalyst. These biosourced catalysts show promising performances in ring-closing metathesis (RCM) and cross-metathesis (CM) reactions, with a high level of recyclability and reusability combined with a good reactivity.

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

    PubMed Central

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

    2014-01-01

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

  12. Olefin Metathesis in Homogeneous Aqueous Media Catalyzed by Conventional Ruthenium Catalysts

    PubMed Central

    Binder, Joseph B.; Blank, Jacqueline J.; Raines, Ronald T.

    2008-01-01

    Olefin metathesis in aqueous solvents is sought for applications in green chemistry and with the hydrophilic substrates of chemical biology, such as proteins and polysaccharides. Most demonstrations of metathesis in water, however, utilize exotic complexes. We have examined the performance of conventional catalysts in homogeneous water–organic mixtures, finding that the second-generation Hoveyda–Grubbs catalyst has extraordinary efficiency in aqueous dimethoxyethane and aqueous acetone. High (71–95%) conversions are achieved for ring-closing and cross metathesis of a variety of substrates in these solvent systems. PMID:17949009

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

    NASA Astrophysics Data System (ADS)

    Balof, Shawna Lynn

    2011-12-01

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

  14. Bond Energies in Models of the Schrock Metathesis Catalyst

    SciTech Connect

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

    2011-06-23

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

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

    ERIC Educational Resources Information Center

    Greco, George E.

    2007-01-01

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

  16. Linker-free, silica-bound olefin-metathesis catalysts: applications in heterogeneous catalysis.

    PubMed

    Cabrera, José; Padilla, Robin; Bru, Miriam; Lindner, Ronald; Kageyama, Takeharu; Wilckens, Kristina; Balof, Shawna L; Schanz, Hans-Jörg; Dehn, Richard; Teles, J Henrique; Deuerlein, Stephan; Müller, Kevin; Rominger, Frank; Limbach, Michael

    2012-11-12

    A set of heterogenized olefin-metathesis catalysts, which consisted of Ru complexes with the H(2)ITap ligand (1,3-bis(2',6'-dimethyl-4'dimethyl aminophenyl)-4,5-dihydroimidazol-2-ylidene) that had been adsorbed onto a silica support, has been prepared. These complexes showed strong binding to the solid support without the need for tethering groups on the complex or functionalized silica. The catalysts were tested in the ring-opening-ring-closing-metathesis (RO-RCM) of cyclooctene (COE) and the self-metathesis of methyl oleate under continuous-flow conditions. The best complexes showed a TON>4000, which surpasses the previously reported materials that were either based on the Grubbs-Hoveyda II complex on silica or on the classical heterogeneous Re(2)O(7)/B(2)O(3) catalyst.

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

    EPA Science Inventory

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

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

    EPA Science Inventory

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

  19. Metathesis transformations of natural products: cross-metathesis of natural rubber and mandarin oil by Ru-alkylidene catalysts.

    PubMed

    Martínez, Araceli; Gutiérrez, Selena; Tlenkopatchev, Mikhail A

    2012-05-18

    This study reports on the degradation of natural rubber (NR) via crossmetathesis with mandarin oil and d-limonene, an abundant compound in essential oils; that were used as chain transfer agents (CTAs) and green solvents. Reactions were performed in the presence of the ruthenium-alkylidene catalysts (PCy₃)₂(Cl)₂Ru=CHPh (I) and (1,3-dimesityl-4,5-dihydroimidazol-2-ylidene) (PCy₃)Cl₂Ru=CHPh (II), respectively. Catalyst II bears an N-heterocyclic carbene ligand (NHC) bounded to the ruthenium atom, which has a strong basic character; therefore it is more active toward trisubstituted olefins in comparison with catalyst I. In both cases, isolated monoterpene-terminated isoprene oligomers were obtained as products of the cross-metathesis degradation of NR. In the presence of catalyst II molecular weight values around M(n) × 10² and yields of 80% were obtained; whereas with catalyst I, the molecular weights of products were about M(n) × 10⁴ with yields ranging 70 to 74%. The composition and yield of NR degradation products were determined by GC/MS (EI) analysis and it was found that the oligomers obtained have primarily one vinyl group and one terpene-monocyclic group at the chain end, with isoprene units A(m) = 2, 3 y 4.

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

    PubMed Central

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

    2015-01-01

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

  1. Tandem hydroformylation/hydrogenation of alkenes to normal alcohols using Rh/Ru dual catalyst or Ru single component catalyst.

    PubMed

    Takahashi, Kohei; Yamashita, Makoto; Nozaki, Kyoko

    2012-11-14

    The catalyst system for tandem hydroformylation/hydrogenation of terminal alkenes to the corresponding homologated normal alcohol was developed. The reaction mechanism for the Rh/Ru dual catalyst was investigated by real-time IR monitoring experiments and (31)P NMR spectroscopy, which proved the mutual orthogonality of Rh-catalyzed hydroformylation and Ru-catalyzed hydrogenation. Detailed investigation about Ru-catalyzed hydrogenation of undecanal under H(2)/CO pressure clarified different kinetics from the hydrogenation under H(2) and gave a clue to design more active hydrogenation catalysts under H(2)/CO atmosphere. The solely Ru-catalyzed normal selective hydroformylation/hydrogenation is also reported.

  2. A simple and effective catalytic system for epoxidation of aliphatic terminal alkenes with manganese(II) as the catalyst.

    PubMed

    Ho, Kam-Piu; Wong, Wing-Leung; Lam, Kin-Ming; Lai, Cheuk-Piu; Chan, Tak Hang; Wong, Kwok-Yin

    2008-01-01

    A simple catalytic system that uses commercially available manganese(II) perchlorate as the catalyst and peracetic acid as the oxidant is found to be very effective in the epoxidation of aliphatic terminal alkenes with high product selectivity at ambient temperature. Many terminal alkenes are epoxidised efficiently on a gram scale in less than an hour to give excellent yields of isolated product (>90 %) of epoxides in high purity. Kinetic studies with some C9-alkenes show that the catalytic system is more efficient in epoxidising terminal alkenes than internal alkenes, which is contrary to most commonly known epoxidation systems. The reaction rate for epoxidation decreases in the order: 1-nonene>cis-3-nonene>trans-3-nonene. ESI-MS and EPR spectroscopic studies suggest that the active form of the catalyst is a high-valent oligonuclear manganese species, which probably functions as the oxygen atom-transfer agent in the epoxidation reaction.

  3. Efficient and selective formation of macrocyclic disubstituted Z alkenes by ring-closing metathesis (RCM) reactions catalyzed by Mo- or W-based monoaryloxide pyrrolide (MAP) complexes: applications to total syntheses of epilachnene, yuzu lactone, ambrettolide, epothilone C, and nakadomarin A.

    PubMed

    Wang, Chenbo; Yu, Miao; Kyle, Andrew F; Jakubec, Pavol; Dixon, Darren J; Schrock, Richard R; Hoveyda, Amir H

    2013-02-18

    The first broadly applicable set of protocols for efficient Z-selective formation of macrocyclic disubstituted alkenes through catalytic ring-closing metathesis (RCM) is described. Cyclizations are performed with 1.2-7.5 mol% of a Mo- or W-based monoaryloxide pyrrolide (MAP) complex at 22 °C and proceed to complete conversion typically within two hours. Utility is demonstrated by synthesis of representative macrocyclic alkenes, such as natural products yuzu lactone (13-membered ring: 73% Z) epilachnene (15-membered ring: 91% Z), ambrettolide (17-membered ring: 91% Z), an advanced precursor to epothilones C and A (16-membered ring: up to 97% Z), and nakadomarin A (15-membered ring: up to 97% Z). We show that catalytic Z-selective cyclizations can be performed efficiently on gram-scale with complex molecule starting materials and catalysts that can be handled in air. We elucidate several critical principles of the catalytic protocol: 1) The complementary nature of the Mo catalysts, which deliver high activity but can be more prone towards engendering post-RCM stereoisomerization, versus W variants, which furnish lower activity but are less inclined to cause loss of kinetic Z selectivity. 2) Reaction time is critical to retaining kinetic Z selectivity not only with MAP species but with the widely used Mo bis(hexafluoro-tert-butoxide) complex as well. 3) Polycyclic structures can be accessed without significant isomerization at the existing Z alkenes within the molecule.

  4. Theory-assisted development of a robust and Z-selective olefin metathesis catalyst.

    PubMed

    Occhipinti, Giovanni; Koudriavtsev, Vitali; Törnroos, Karl W; Jensen, Vidar R

    2014-08-07

    DFT calculations have predicted a new, highly Z-selective ruthenium-based olefin metathesis catalyst that is considerably more robust than the recently reported (SIMes)(Cl)(RS)RuCH(o-OiPrC6H4) (3a, SIMes = 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene, R = 2,4,6-triphenylbenzene) [J. Am. Chem. Soc., 2013, 135, 3331]. Replacing the chloride of 3a by an isocyanate ligand to give 5a was predicted to increase the stability of the complex considerably, at the same time moderately improving the Z-selectivity. Compound 5a is easily prepared in a two-step synthesis starting from the Hoveyda-Grubbs second-generation catalyst 3. In agreement with the calculations, the isocyanate-substituted 5a appears to be somewhat more Z-selective than the chloride analogue 3a. More importantly, 5a can be used in air, with unpurified and non-degassed substrates and solvents, and in the presence of acids. These are traits that are unprecedented among highly Z-selective olefin metathesis catalysts and also very promising with respect to applications of the new catalyst.

  5. Origins of initiation rate differences in ruthenium olefin metathesis catalysts containing chelating benzylidenes.

    PubMed

    Engle, Keary M; Lu, Gang; Luo, Shao-Xiong; Henling, Lawrence M; Takase, Michael K; Liu, Peng; Houk, K N; Grubbs, Robert H

    2015-05-06

    A series of second-generation ruthenium olefin metathesis catalysts was investigated using a combination of reaction kinetics, X-ray crystallography, NMR spectroscopy, and DFT calculations in order to determine the relationship between the structure of the chelating o-alkoxybenzylidene and the observed initiation rate. Included in this series were previously reported catalysts containing a variety of benzylidene modifications as well as four new catalysts containing cyclopropoxy, neopentyloxy, 1-adamantyloxy, and 2-adamantyloxy groups. The initiation rates of this series of catalysts were determined using a UV/vis assay. All four new catalysts were observed to be faster-initiating than the corresponding isopropoxy control, and the 2-adamantyloxy catalyst was found to be among the fastest-initiating Hoveyda-type catalysts reported to date. Analysis of the X-ray crystal structures and computed energy-minimized structures of these catalysts revealed no correlation between the Ru-O bond length and Ru-O bond strength. On the other hand, the initiation rate was found to correlate strongly with the computed Ru-O bond strength. This latter finding enables both the rationalization and prediction of catalyst initiation through the calculation of a single thermodynamic parameter in which no assumptions about the mechanism of the initiation step are made.

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

    PubMed

    Yao, Qingwei; Zhang, Yiliang

    2004-01-14

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

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

    PubMed Central

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

    2016-01-01

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

  8. Efficient and Selective Formation of Macrocyclic Disubstituted Z Alkenes by Ring-Closing Metathesis (RCM) Reactions Catalyzed by Mo- or W-Based Monoaryloxide Pyrrolide (MAP) Complexes. Applications to Total Syntheses of Epilachnene, Yuzu Lactone, Ambrettolide, Epothilone C and Nakadomarin A

    PubMed Central

    Wang, Chenbo; Yu, Miao; Kyle, Andrew F.; Jakubec, Jakubec; Dixon, Darren J.; Schrock, Richard R.; Hoveyda, Amir H.

    2014-01-01

    The first broadly applicable set of protocols for efficient and highly Z-selective formation of macrocyclic disubstituted alkenes through catalytic ring-closing metathesis (RCM) is described. Cyclizations are performed in the presence of 1.2–7.5 mol % of a Mo- or W-based mono-aryloxide pyrrolide (MAP) complex at 22 °C and typically proceed to complete conversion within two hours. The utility of the catalytic strategy is demonstrated by stereoselective synthesis of representative macrocyclic alkenes, including natural products yuzu lactone (13-membered ring: 73% Z) epilachnene (15-membered ring: 91% Z), ambrettolide (17-membered ring: 91% Z), an advanced precursor to epothilones C and A (16-membered ring: up to 97% Z) and nakadomarin A (polycyclic 15-membered ring: up to 97% Z). We demonstrate the complementary nature of the Mo-based catalysts, which deliver high activity but can be more prone to causing post-RCM stereoisomerization, versus W-based variants, which furnish lower activity but are less inclined towards causing loss of kinetic Z selectivity; a number of catalytic Z-selective cases are provided to elucidate which catalyst class is best suited for which substrate and particular type of alkene RCM process. Mechanistic models that rationalize the origin and the trends in Z selectivity as a function of alterations in the catalyst structure (i.e., Mo vs W and different imido and aryloxide or alkoxide ligands) are provided; we show that reaction time can be critical in retaining the Z selectivity attained not only with MAP complexes but with the original Mo-based bis-alkoxides as well. The W-based catalysts are sufficiently stable to be manipulated in air even with humidity levels of up to 80%; the catalytic Z-selective cyclizations can be performed on gram scale with complex molecule starting materials. PMID:23345004

  9. In situ generated bulky palladium hydride complexes as catalysts for the efficient isomerization of olefins. Selective transformation of terminal alkenes to 2-alkenes.

    PubMed

    Gauthier, Delphine; Lindhardt, Anders T; Olsen, Esben P K; Overgaard, Jacob; Skrydstrup, Troels

    2010-06-16

    Application of an in situ generated bulky palladium(II) hydride catalyst obtained from a 1:1:1 mixture of Pd(dba)(2), P(tBu)(3), and isobutyryl chloride provides an efficient protocol for the isomerization and migration of a variety of olefins. In addition to the isomerization of (Z)- to (E)-olefins, the conjugative migration of allylbenzenes, allyl ethers, and amines was effectively achieved in near-quantitative yields and with excellent functional group tolerance. Catalyst loadings in the range of 0.5-1.0 mol % were typically applied, but even loadings as low as 0.25 mol % could be achieved when the reactions were performed under neat conditions. More interestingly, the investigated catalyst proved to be selective for converting terminal alkenes to 2-alkenes. This one-carbon migration process for monosubstituted olefins provides an alternative catalyst, which bridges the gap between the allylation and propenylation/vinylation protocols. Several substrates, including homoallylic alcohols and amines, were selectively transformed into their corresponding 2-alkenes, and examples using enantiomerically enriched substrates provided products without epimerization at the allylic stereogenic carbon centers. Finally, some mechanistic investigations were undertaken to understand the nature of the active in situ generated Pd-H catalyst. These studies revealed that the catalytic system is highly dependent on the large steric demand of the P(tBu)(3) ligand. The use of an alternative ligand, cataCXium PinCy, also proved effective for generating an active catalyst, and it was demonstrated in some cases to display better selectivity for the one-carbon shifts of terminal olefins. A possible intermediate involved in the preparation of the active catalyst was characterized by its single-crystal X-ray structure, which revealed a monomeric tricoordinated palladium(II) acyl complex, bearing a chloride ligand.

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

    PubMed

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

    2016-08-16

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

  11. PS-BEMP as a basic catalyst for the phospha-Michael addition to electron-poor alkenes.

    PubMed

    Strappaveccia, Giacomo; Bianchi, Luca; Ziarelli, Simone; Santoro, Stefano; Lanari, Daniela; Pizzo, Ferdinando; Vaccaro, Luigi

    2016-04-14

    PS-BEMP was used as a heterogeneous catalyst for the phospha-Michael addition of phosphorus nucleophiles to a variety of electron-poor alkenes. The addition reactions were generally performed with equimolar amounts of reagents under solvent free conditions. The protocol proved to be very efficient for the addition to aromatic, non-aromatic and cyclic ketones, giving good yields (78-85%) in all cases. The protocol was also extended with good results to α,β-unsaturated esters and nitriles. This demonstrates that PS-BEMP is a good catalyst for the phospha-Michael addition to electron-poor alkenes.

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

    DOEpatents

    Guan, Zhibin; Lu, Yixuan

    2015-09-15

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

  13. Ligand Exchange-Mediated Activation and Stabilization of a Re-Based Olefin Metathesis Catalyst by Chlorinated Alumina.

    PubMed

    Gallo, Alessandro; Fong, Anthony; Szeto, Kai C; Rieb, Julia; Delevoye, Laurent; Gauvin, Régis M; Taoufik, Mostafa; Peters, Baron; Scott, Susannah L

    2016-10-05

    Extensive chlorination of γ-Al2O3 results in the formation of highly Lewis acidic surface domains depleted in surface hydroxyl groups. Adsorption of methyltrioxorhenium (MTO) onto these chlorinated domains serves to activate it as a low temperature, heterogeneous olefin metathesis catalyst and confers both high activity and high stability. Characterization of the catalyst reveals that the immobilized MTO undergoes partial ligand exchange with the surface, whereby some Re sites acquire a chloride ligand from the modified alumina while donating an oxo ligand to the support. More specifically, Re LIII-edge EXAFS and DFT calculations support facile ligand exchange between MTO and Cl-Al2O3 to generate [CH3ReO2Cl(+)] fragments that interact with a bridging oxygen of the support via a Lewis acid-base interaction. According to IR and solid-state NMR, the methyl group remains intact, and does not evolve spontaneously to a stable methylene tautomer. Nevertheless, the chloride-promoted metathesis catalyst is far more active and productive than MTO/γ-Al2O3, easily achieving a TON of 100 000 for propene metathesis in a flow reactor at 10 °C (compared to TON < 5000 for the nonchlorinated catalyst). Increased activity is a consequence of both a larger fraction of active sites and a higher intrinsic activity for the new sites. Increased stability is tentatively attributed to a stronger interaction between MTO and chlorinated surface regions, as well as extensive depletion of the Brønsted acidic surface hydroxyl population. The reformulated catalyst represents a major advance for Re-based metathesis catalysts, whose widespread use has thus far been severely hampered by their instability.

  14. A Well-Defined, Silica-Supported Tungsten Imido Alkylidene OlefinMetathesis Catalyst

    SciTech Connect

    Rhers, Bochra; Salameh, Alain; Baudouin, Anne; Quadrelli, ElsjeA.; Taoufik, Mostafa; Coperet, Christophe; Lefebvre, Frederic; Basset,Jean-Marie; Solans-Monfort, Xavier; Eisenstein, Odile; Lukens, Wayne W.; Lopez, Lordes.P.H.; Sinha, Amritanshu; Schrock, Richard R.

    2006-06-13

    The reaction of [W(=NAr)(=CHtBu)(CH2tBu)2](1; Ar =2,6-iPrC6H3) with a silica partially dehydroxylated at 700oC, SiO2-(700),gives syn-[(_SiO)W(=NAr)(=CHtBu)(CH2tBu)](2) as a major surface species,which was fully characterized by mass balance analysis, IR, NMR, EXAFS,and DFT periodic calculations. Similarly, complex 1 reacts with[(c-C5H9)7Si7O12SiOH]to give [(SiO)W(=NAr)(=CHtBu)(CH2tBu)](2m), whichshows similar spectroscopic properties. Surface complex 2 is a highlyactive propene metathesis catalyst, which can achieve a TON of 16000within 100 h, with only a slow deactivation.

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

    PubMed Central

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

    2012-01-01

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

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

    PubMed

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

    2013-03-07

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

  17. Magnetic Fe@g-C3N4: A Photoactive Catalyst for the Hydrogenation of Alkenes and Alkynes

    EPA Science Inventory

    A photoactive catalyst, Fe@g-C3N4, has been developed for the hydrogenation of alkenes and alkynes using hydrazine hydrate as a source of hydrogen. The magnetically separable Fe@g-C3N4 eliminates the use of high pressure hydrogenation and the reaction can be accomplished using vi...

  18. Rationalizing current strategies to protect N-heterocyclic carbene-based ruthenium catalysts active in olefin metathesis from C-H (de)activation.

    PubMed

    Poater, Albert; Bahri-Laleh, Naeimeh; Cavallo, Luigi

    2011-06-21

    Defending second generation Ru-catalysts in olefin metathesis from C-H (de)activation reactions requires precise catalyst design strategies. Computer simulations are used here to rationalize precisely the role of the currently used catalyst structural modifications, and the way these modifications cooperate.

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

    PubMed Central

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

    2008-01-01

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

  20. Organometallic chemistry: A new metathesis

    NASA Astrophysics Data System (ADS)

    Hennessy, Elisabeth T.; Jacobsen, Eric N.

    2016-08-01

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

  1. Magnetic Fe@g??C3N4: A Photoactive Catalyst for the Hydrogenation of Alkenes and Alkynes

    EPA Pesticide Factsheets

    A photoactive catalyst, Fe@g-C3N4, has been developed for the hydrogenation of alkenes and alkynes using hydrazine hydrate as a source of hydrogen. The magnetically separable Fe@g-C3N4 eliminates the use of high pressure hydrogenation, and the reaction can be accomplished using visible light without the need for external sources of energy.This dataset is associated with the following publication:Baig, N., S. Verma, R. Varma , and M. Nadagouda. Magnetic Fe@g-C3N4: A Photoactive Catalyst for the Hydrogenation of Alkenes and Alkynes. ACS Sustainable Chemistry & Engineering. American Chemical Society, Washington, DC, USA, 4(3): 1661-1664, (2016).

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  3. Expanding the scope of metathesis: a survey of polyfunctional, single-site supported tungsten systems for hydrocarbon valorization.

    PubMed

    Popoff, Nicolas; Mazoyer, Etienne; Pelletier, Jérémie; Gauvin, Régis M; Taoufik, Mostafa

    2013-12-07

    Olefin metathesis is increasingly incorporated in polyfunctional industrial processes. The classical WO3/SiO2 olefin metathesis catalyst is combined to other catalysts in order to afford higher added-value chemicals. However, the combination of several reactions, not only in a single reactor, but also stemming from a single, multifunctional surface species is a desirable improvement regarding process issues. Well-defined surface organometallic tungsten species can be designed to implement targeted functionalities (carbene, hydride, alkyl, …). By tuning the metal's coordination sphere, it is possible to combine metathesis with several reactions, such as (de)hydrogenation, dimerization or isomerization. Novel, unconventional reactions for the production and upgrading of alkanes and alkenes have thus been uncovered. The reactivity of this library of supported catalysts is discussed based on the type of mediated transformations: monofunctional (alkene and alkyne metathesis), bifunctional (1-butene or 2-butenes to propylene), trifunctional (ethylene to propylene, alkane metathesis, …). Mechanistic considerations will be discussed to put these results in a wider perspective for future developments.

  4. Methods for suppressing isomerization of olefin metathesis products

    DOEpatents

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

    2015-09-22

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

  5. Methods for suppressing isomerization of olefin metathesis products

    DOEpatents

    Firth, Bruce E.; Kirk, Sharon E.

    2015-10-27

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

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

    PubMed

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

    2015-09-14

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

  7. In situ forming hydrogels via catalyst-free and bioorthogonal "tetrazole-alkene" photo-click chemistry.

    PubMed

    Fan, Yaping; Deng, Chao; Cheng, Ru; Meng, Fenghua; Zhong, Zhiyuan

    2013-08-12

    In situ forming hydrogels were developed from 4-arm poly(ethylene glycol)-methacrylate (PEG-4-MA) and -tetrazole (PEG-4-Tet) derivatives through catalyst-free and bioorthogonal "tetrazole-alkene" photo-click chemistry. PEG-4-MA and PEG-4-Tet (Mn = 10 kg/mol) were soluble at 37 °C in phosphate buffer (PB, pH 7.4, 10 mM) at total polymer concentrations ranging from 20 to 60 wt % but formed fluorescent hydrogels upon 365 nm UV irradiation at an intensity of 20.6, 30.7, or 60 mW/cm(2). The gelation times ranged from ca. 50 s to 5 min, and storage moduli varied from 0.65 to 25.2 kPa depending on polymer concentrations and degrees of Tet substitution in PEG-4-Tet conjugates. The cell experiments via an indirect contact assay demonstrated that these "tetrazole-alkene" photo-click PEG hydrogels were noncytotoxic. The high specificity of photo-click reaction renders thus obtained PEG hydrogels particularly interesting for controlled protein release. Notably, in vitro release studies showed that cytochrome c (CC), γ-globulins (Ig), and recombinant human interleukin-2 (rhIL-2) all were released from PEG hydrogels in a sustained and quantitative manner over a period of 14-20 days. Importantly, released CC and rhIL-2 exhibited comparable biological activities to native CC and rhIL-2, respectively. These results confirm that "tetrazole-alkene" photo-click reaction is highly compatible with these loaded proteins. This photo-controlled, specific, efficient, and catalyst-free click chemistry provides a new and versatile strategy to in situ forming hydrogels that hold tremendous potentials for protein delivery and tissue engineering.

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

    PubMed Central

    Chemler, Sherry R.

    2010-01-01

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

  9. Construction of a visible light-driven hydrocarboxylation cycle of alkenes by the combined use of Rh(i) and photoredox catalysts.

    PubMed

    Murata, Kei; Numasawa, Nobutsugu; Shimomaki, Katsuya; Takaya, Jun; Iwasawa, Nobuharu

    2017-03-09

    A visible light driven catalytic cycle for hydrocarboxylation of alkenes with CO2 was established using a combination of a Rh(i) complex as a carboxylation catalyst and [Ru(bpy)3](2+) (bpy = 2,2'- bipyridyl) as a photoredox catalyst. Two key steps, the generation of Rh(i) hydride species and nucleophilic addition of π-benzyl Rh(i) species to CO2, were found to be mediated by light.

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

    NASA Astrophysics Data System (ADS)

    Kuznetsov, N. Yu; Bubnov, Yu N.

    2015-07-01

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

  11. Olefin metathesis in air

    PubMed Central

    Piola, Lorenzo; Nahra, Fady

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    SciTech Connect

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

    1992-12-30

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

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

    ERIC Educational Resources Information Center

    Seen, Andrew J.

    2004-01-01

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

  15. Ring-expanding olefin metathesis: a route to highly active unsymmetrical macrocyclic oligomeric co-salen catalysts for the hydrolytic kinetic resolution of epoxides.

    PubMed

    Zheng, Xiaolai; Jones, Christopher W; Weck, Marcus

    2007-02-07

    In the presence of the third generation Grubbs catalyst, the ring-expanding olefin metathesis of a monocyclooct-4-en-1-yl functionalized salen ligand and the corresponding Co(II)(salen) complex at low monomer concentrations results in the exclusive formation of macrocyclic oligomeric structures with the salen moieties being attached in an unsymmetrical, flexible, pendent manner. The TOF-MALDI mass spectrometry reveals that the resulting macrocyclic oligomers consist predominantly of dimeric to tetrameric species, with detectable traces of higher homologues up to a decamer. Upon activation under aerobic and acidic conditions, these Co(salen) macrocycles exhibit extremely high reactivities and selectivities in the hydrolytic kinetic resolution (HKR) of a variety of racemic terminal epoxides under neat conditions with very low catalyst loadings. The excellent catalytic properties can be explained in terms of the new catalyst's appealing structural features, namely, the flexible oligomer backbone, the unsymmetrical pendent immobilization motif of the catalytic sites, and the high local concentration of Co(salen) species resulting from the macrocyclic framework. This ring-expanding olefin metathesis is suggested to be a simple way to prepare tethered metal complexes that are endowed with key features--(i) a high local concentration of metal complexes and (ii) a flexible, single point of attachment to the support--that facilitate rapid and efficient catalysis when a bimetallic transition state is required.

  16. Methods of making organic compounds by metathesis

    DOEpatents

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

    2015-09-01

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

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

    ERIC Educational Resources Information Center

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

    2013-01-01

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

  18. Niobium-silica catalysts for the selective epoxidation of cyclic alkenes: the generation of the active site by grafting niobocene dichloride.

    PubMed

    Tiozzo, Cristina; Bisio, Chiara; Carniato, Fabio; Gallo, Alessandro; Scott, Susannah L; Psaro, Rinaldo; Guidotti, Matteo

    2013-08-28

    Niobium-containing silica materials obtained by deposition via liquid-phase grafting or dry impregnation of niobocene(iv) dichloride are active and selective catalysts in the epoxidation of alkenes in the presence of aqueous hydrogen peroxide. The generation of the catalytically-active Nb species was followed step-by-step, and investigated using a combined DR-UV-Vis, NIR, Raman, XRD, XANES and EXAFS analyses. At the end of the grafting procedure, the nature of the surface active species can be described as an oxo-Nb(v) site, tripodally grafted onto the silica surface in close proximity to other Nb(v) centres. The liquid-phase methodology provides a better dispersion of the metal sites onto the siliceous support than the dry-impregnation approach. The niobium-silica catalysts were then tested in the epoxidation of cyclohexene and 1-methylcyclohexene, as model substrates.

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

    PubMed

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

    2016-06-13

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

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

    PubMed

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

    2010-08-04

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

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

    PubMed

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

    2015-07-21

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

  2. An S(N)Ar approach to sterically hindered ortho-alkoxybenzaldehydes for the synthesis of olefin metathesis catalysts.

    PubMed

    Engle, Keary M; Luo, Shao-Xiong; Grubbs, Robert H

    2015-04-17

    A three-step procedure has been developed for preparing ortho-alkoxybenzaldehydes from ortho-fluorobenzaldehydes that tolerates the use of sterically hindered sodium alkoxide nucleophiles. The protocol is modular and operationally convenient. The ortho-alkoxybenzaldehyde products can be converted in one additional step to ortho-alkoxystyrenes by a Wittig reaction. These styrenes are precursors to the chelating benzylidene moiety in a proposed series of novel ruthenium complexes for use in olefin metathesis. Chelation with three representative styrenes has been demonstrated.

  3. Metathesis depolymerizable surfactants

    DOEpatents

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

    2008-04-15

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

  4. Enantioselective Olefin Metathesis with Cyclometalated Ruthenium Complexes

    PubMed Central

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

    Zhang, Teng; Manna, Kuntal; Lin, Wenbin

    2016-03-09

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

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

    SciTech Connect

    Zhang, Teng; Manna, Kuntal; Lin, Wenbin

    2016-05-06

    New and active earth-abundant metal catalysts are critically needed to replace precious metal-based catalysts for sustainable production of commodity and fine chemicals. We report here the design of highly robust, active, and reusable cobalt-bipyridine- and cobalt-phenanthroline-based metal–organic framework (MOF) catalysts for alkene hydrogenation and hydroboration, aldehyde/ketone hydroboration, and arene C–H borylation. In alkene hydrogenation, the MOF catalysts tolerated a variety of functional groups and displayed unprecedentedly high turnover numbers of ~2.5 × 106 and turnover frequencies of ~1.1 × 105 h–1. Structural, computational, and spectroscopic studies show that site isolation of the highly reactive (bpy)Co(THF)2 species in the MOFs prevents intermolecular deactivation and stabilizes solution-inaccessible catalysts for broad-scope organic transformations. Computational, spectroscopic, and kinetic evidence further support a hitherto unknown (bpy•–)CoI(THF)2 ground state that coordinates to alkene and dihydrogen and then undergoing σ-complex-assisted metathesis to form (bpy)Co(alkyl)(H). Reductive elimination of alkane followed by alkene binding completes the catalytic cycle. MOFs thus provide a novel platform for discovering new base-metal molecular catalysts and exhibit enormous potential in sustainable chemical catalysis.

  8. Ultrasonically improved semi-hydrogenation of alkynes to (Z-)alkenes over novel lead-free Pd/Boehmite catalysts.

    PubMed

    Wu, Zhilin; Cravotto, Giancarlo; Gaudino, Emanuela Calcio; Giacomino, Agnese; Medlock, Jonathan; Bonrath, Werner

    2017-03-01

    This paper reports the application of ultrasound in the semi-hydrogenation of alkynes over two novel Pd/Boehmite catalysts. The semi-hydrogenations of phenylacetylene, diphenylacetylene and 2-butyne-1,4-diol have either been investigated in an ultrasonic bath under atmospheric hydrogen pressure, or in an ultrasonic horn reactor under 0.1-0.5MPa hydrogen pressure. Alkyne hydrogenation was suppressed by sonication under atmospheric hydrogen pressure, but promoted by sonication under 0.1MPa of hydrogen pressure. Sonication increased selectivity towards the semi-hydrogenated products in both cases. Catalyst loading, hydrogen pressure, temperature and the presence of quinoline, all impacted on hydrogenation rate, activity and selectivity to semi-hydrogenated products. Palladium leaching from the catalyst was evaluated in ethanol and hexane both under plain stirring and sonication.

  9. An efficient carbonyl-alkene metathesis of bicyclic oxetanes: photoinduced electron transfer reduction of the Paternò-Büchi adducts from 2,3-dihydrofuran and aromatic aldehydes.

    PubMed

    Pérez-Ruiz, Raúl; Miranda, Miguel A; Alle, Ronald; Meerholz, Klaus; Griesbeck, Axel G

    2006-01-01

    The bicyclic oxetanes and resulting from photocycloaddition of aromatic aldehydes to 2,3-dihydrofuran, were efficiently cleaved by means of electron-transfer reduction, photoinduced by the electronically excited reductants 1-methoxynaphthalene (MN) and 2,7-dimethoxynaphthalene (DMN) in acetonitrile. The fluorescence quenching rates of DMN/MN by and were determined by static methods, the triplet quenching rates were determined by means of laser flash photolysis (LFP). The product analysis established a "photo-photo metathesis" where both cycloaddition and cycloreversion processes are induced by photochemical processes.

  10. Enantioselective synthesis of 5-epi-citreoviral using ruthenium-catalyzed asymmetric ring-closing metathesis.

    PubMed

    Funk, Timothy W

    2009-11-05

    Chiral ruthenium olefin metathesis catalysts can perform asymmetric ring-closing reactions in > or = 90% ee with low catalyst loadings. To illustrate the practicality of these reactions and the products they form, an enantioselective total synthesis of 5-epi-citreoviral was completed by using an asymmetric ring-closing olefin metathesis reaction as a key step early in the synthesis. All of the stereocenters in the final compound were set by using the chiral center generated by asymmetric olefin metathesis.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

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

    PubMed

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

    2016-08-30

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

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

    SciTech Connect

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

    2016-08-30

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

  14. Alkyne metathesis on the rise.

    PubMed

    Fürstner, Alois

    2013-03-04

    The early years of alkyne metathesis were marked by a somewhat ironic state of affairs: the proposed mechanism was swiftly validated and more than one effective catalyst became available shortly after the discovery of this transformation; surprisingly, however, the impact on synthesis remained very limited for a long period of time. Recent advances, however, suggest that this situation is about to change: the remarkable activity, functional-group tolerance, and reliability of the latest generation of catalysts open the door for highly advanced applications. The resulting (cyclo)alkynes are amenable to numerous postmetathetic transformations, which diversify the product portfolio and bring many different structural motifs into reach. Since the catalysts have also evolved from the glovebox to the benchtop, there should be little barrier left for a wider use of this reaction in organic synthesis.

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

    EPA Science Inventory

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

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

    SciTech Connect

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

    2011-12-31

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

  17. Cationic ruthenium alkylidene catalysts bearing phosphine ligands.

    PubMed

    Endo, Koji; Grubbs, Robert H

    2016-02-28

    The discovery of highly active catalysts and the success of ionic liquid immobilized systems have accelerated attention to a new class of cationic metathesis catalysts. We herein report the facile syntheses of cationic ruthenium catalysts bearing bulky phosphine ligands. Simple ligand exchange using silver(i) salts of non-coordinating or weakly coordinating anions provided either PPh3 or chelating Ph2P(CH2)nPPh2 (n = 2 or 3) ligated cationic catalysts. The structures of these newly reported catalysts feature unique geometries caused by ligation of the bulky phosphine ligands. Their activities and selectivities in standard metathesis reactions were also investigated. These cationic ruthenium alkylidene catalysts reported here showed moderate activity and very similar stereoselectivity when compared to the second generation ruthenium dichloride catalyst in ring-closing metathesis, cross metathesis, and ring-opening metathesis polymerization assays.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  19. Towards highly active Pd/CeO2 for alkene hydrogenation by tuning Pd dispersion and surface properties of the catalysts.

    PubMed

    Zhang, Sai; Li, Jing; Xia, Zhaoming; Wu, Chao; Zhang, Zhiyun; Ma, Yuanyuan; Qu, Yongquan

    2017-03-02

    Extensive applications of noble metals as heterogeneous catalysts are limited by their global reserve scarcity and exorbitant price. Identifying the intrinsic active nature of a catalyst benefits the designing of catalysts with trace amounts of noble metals; these catalysts display better or comparable overall catalytic efficiency than their heavily loaded counterparts. Herein, systematic studies on Pd dispersion and surface properties of a series of Pd/CeO2 catalysts for styrene hydrogenation showed that high Pd dispersion and surface abundant defects of the catalysts are essential to realize superior activity. Highly dispersed subnanometric Pd clusters on porous nanorods of ceria with a large surface Ce(3+) fraction of 27.4%, high Pd dispersion of 73.6%, and low Pd loading of 0.081 wt% delivered a very large turnover frequency of 103 233 h(-1) based on each exposed Pd atom for styrene hydrogenation at 1.0 MPa H2 and 30 °C. Experimental data, kinetic analysis, and density functional theory calculations revealed that the highly dispersed Pd shows a low affinity for styrene and provides more exposed Pd sites for hydrogen activation. The surface abundant defects (oxygen vacancy) of Pd/CeO2 catalysts can enrich the electron density of Pd, improve its capability for H2 dissociation and lower the affinity of styrene for Pd.

  20. From a decomposition product to an efficient and versatile catalyst: the [Ru(η5-indenyl)(PPh3)2Cl] story.

    PubMed

    Manzini, Simone; Fernández-Salas, José A; Nolan, Steven P

    2014-10-21

    One of the most important challenges in catalyst design is the synthesis of stable promoters without compromising their activity. For this reason, it is important to understand the factors leading to decomposition of such catalysts, especially if side-products negatively affect the activity and selectivity of the starting complex. In this context, the understanding of termination and decomposition processes in olefin metathesis is receiving significant attention from the scientific community. For example, the decomposition of ruthenium olefin metathesis precatalysts in alcohol solutions can occur during either the catalyst synthesis or the metathesis process, and such decomposition has been found to be common for Grubbs-type precatalysts. These decomposition products are usually hydridocarbonyl complexes, which are well-known to be active in several transformations such as hydrogenation, terminal alkene isomerization, and C-H activation chemistry. The reactivity of these side products can be unwanted, and it is therefore important to understand how to avoid them and maybe also important to keep an open mind and think of ways to use these in other catalytic reactions. A showcase of these decomposition studies is reported in this Account. These reports analyze the stability of ruthenium phenylindenylidene complexes, highly active olefin metathesis precatalysts, in basic alcohol solutions. Several different decomposition processes can occur under these conditions depending on the starting complex and the alcohol used. These indenylidene-bearing metathesis complexes display a completely different behavior compared with that of other metathesis precatalysts and show an alternative competitive alcoholysis pathway, where rather than forming the expected hydrido carbonyl complexes, the indenylidene fragment is transformed into a η(1)-indenyl, which then rearranges to its η(5)-indenyl form. In particular, [RuCl(η(5)-(3-phenylindenylidene)(PPh3)2] has been found to be

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

    PubMed Central

    2015-01-01

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

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

    PubMed Central

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

    2011-01-01

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

  3. Mechanistic insights into the role of PC- and PCP-type palladium catalysts in asymmetric hydrophosphination of activated alkenes incorporating potential coordinating heteroatoms.

    PubMed

    Yang, Xiang-Yuan; Jia, Yu-Xiang; Tay, Wee Shan; Li, Yongxin; Pullarkat, Sumod A; Leung, Pak-Hing

    2016-09-14

    The impact of the structural attributes of chiral PC- and PCP-palladium catalysts was investigated in the asymmetric hydrophosphination of various heterocycle-functionalized enone substrates. Due to the architecture of the catalysts, they are confronted with potential catalyst deactivation arising from the coordination of the electron-rich heteroatoms (P, O, N and S) to the metal center. A systematic variation of the location and identity of the heteroatoms demonstrated the impact of structural modifications on the substrates, which have a significant influence on both yields (16-99%) and enantioselectivities (0-99%). A detailed discussion on the distinct catalytic mechanisms (intra- vs. inter-molecular addition) provides important information to explain the results obtained.

  4. Synthesis-Structure–Function Relationships of Silica-Supported Niobium(V) Catalysts for Alkene Epoxidation with H 2 O 2

    SciTech Connect

    Thornburg, Nicholas E.; Nauert, Scott L.; Thompson, Anthony B.; Notestein, Justin M.

    2016-08-12

    Many industrially significant selective oxidation reactions are catalyzed by supported and bulk transition metal oxides. Catalysts for the synthesis of oxygenates, and especially for epoxidation, have predominantly focused on TiOx supported on or co-condensed with SiO2, whereas much of the rest of Groups 4 and 5 have been less studied. We have recently demonstrated through periodic trends using a uniform molecular precursor that niobium(V)-silica catalysts reveal the highest activity and selectivity for efficient utilization of H2O2 for epoxidation across all of Groups 4 and 5. In this work, we graft a wide range of Nb(V) precursors, spanning surface densities of 0.07–1.6 Nb groups nm–2 on mesoporous silica, and we characterize these materials with UV–visible spectroscopy and Nb K-edge XANES. Further, we apply in situ chemical titration with phenylphosphonic acid (PPA) in the epoxidation of cis-cyclooctene by H2O2 to probe the numbers and nature of the active sites across this series and in a set of related Ti-, Zr-, Hf-, and Ta-SiO2 catalysts. By this method, the fraction of kinetically relevant NbOx species ranges from ~15% to ~65%, which correlates with spectroscopic evaluation of the NbOx sites. This titration leads to a single value for the average turnover frequency, on a per active site basis rather than a per Nb atom basis, of 1.4 ± 0.52 min–1 across the 21 materials in the series. These quantitative maps of structural properties and kinetic consequences link key catalyst descriptors of supported Nb-SiO2 to enable rational design for next-generation oxidation catalysts.

  5. The first alkene-platinum-silyl complexes: lifting the hydrosilation mechanism shroud with long-lived precatalytic intermediates and true pt catalysts.

    PubMed

    Roy, Aroop K; Taylor, Richard B

    2002-08-14

    The synthesis, characterization, and exploratory chemistry of two classes of alkene-platinum-silyl complexes, which have been postulated as hydrosilation intermediates, are described in this report. The unique dimeric complexes 1, [R(3)Si(mu-Cl)(eta(2)-COD)Pt](2) [R(3)Si = Et(3)Si, MeCl(2)Si, Me(2)ClSi, "(EtO)(3)Si", PhMe(2)Si, and (Me(3)SiO)Me(2)Si; COD = cycloocta-1,5-diene], and the bis-silyl complexes 2, (eta(4)-COD)Pt(SiR(3))(2) (R(3)Si = Cl(3)Si, MeCl(2)Si, Me(2)ClSi, and PhMe(2)Si), are formed from the sequential reaction of 2 and 4 equiv of the corresponding hydrosilanes, respectively, with Pt(COD)Cl(2) in the presence of a small excess of COD. Complexes 1 are stable for many days in solution at room temperature but decompose via slow elimination of chlorosilane. Some of the bis-silyl compounds 2 are stable for extended periods under inert atmosphere and especially below 0 degrees C, either in the solid state or in solution (in the presence of a small excess of free COD). Complexes 2 display catalytic activity as discrete, molecular, and mononuclear species for hydrosilation and isomerization reactions. Compound 2c (R(3)Si = MeCl(2)Si) was fully characterized via multinuclear NMR spectroscopy and X-ray crystal structure analysis. The facile H-transfer rather than Si-transfer to bound COD provides experimental support for the sequence of insertive steps in the Chalk-Harrod catalytic cycle, at least for Pt-catalyzed hydrosilation.

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

    PubMed Central

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

    2015-01-01

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

  7. Alkene epoxidations catalysed by Mo(VI) supported on imidazole-containing polymers I. Synthesis, characterisation, and activity of catalysts in the epoxidation of cyclohexene

    SciTech Connect

    Miller, M.M.; Sherrington, D.C.

    1995-04-01

    Polystyrene resins functionalised with hydroxylpropyl aminomethyl pyridine, pyridyl imidazole, and carboxybenzimidazole, polyglycidyl methacrylate resins functionalised with aminomethyl pyridine and pyridyl imidazole, and polybenzimidazole resin have all been loaded with Mo(VI). The resulting polymer metal complexes have been activated by treatment with t-butylhydroperoxide, then used as catalysts in the liquid-phase epoxidation of cyclohexene using t-butylhydroperoxide. Polymers containing the imidazole group were particularly active, and unlike the other species did not require preactivation to induce high activity. The complexes formed with the imidazole-containing polymers appear to be monometallic species, whereas the other polymer ligands yield oxybridged bimetallic species. This accounts for the major difference in activity recorded. Possible structures for the catalysts are proposed based on information in the literature. 30 refs., 10 figs., 6 tabs.

  8. Refining of plant oils to chemicals by olefin metathesis.

    PubMed

    Chikkali, Samir; Mecking, Stefan

    2012-06-11

    Plant oils are attractive substrates for the chemical industry. Their scope for the production of chemicals can be expanded by sophisticated catalytic conversions. Olefin metathesis is an example, which also illustrates generic issues of "biorefining" to chemicals. Utilization on a large scale requires high catalyst activities, which influences the choice of the metathesis reaction. The mixture of different fatty acids composing a technical-grade plant oil substrate gives rise to a range of products. This decisively determines possible process schemes, and potentially provides novel chemicals and intermediates not employed to date.

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

    PubMed

    Masruri; Willis, Anthony C; McLeod, Malcolm D

    2012-10-05

    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.

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

    PubMed

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

    2016-07-28

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

  11. Gold-catalyzed three-component coupling: oxidative oxyarylation of alkenes.

    PubMed

    Melhado, Asa D; Brenzovich, William E; Lackner, Aaron D; Toste, F Dean

    2010-07-07

    The three-component coupling of terminal alkenes with arylboronic acids and oxygen nucleophiles is described. The reaction employs a binuclear gold(I) bromide as a catalyst and Selectfluor reagent as the stoichiometric oxidant. Alcohols, carboxylic acids, and water can be employed as oxygen nucleophiles, thus providing an efficient entry into beta-aryl ethers, esters, and alcohols from alkenes.

  12. Probing the Mechanism of the Double C—H (De)Activation Route of a Ru-Based Olefin Metathesis Catalyst

    NASA Astrophysics Data System (ADS)

    Poater, Albert; Cavallo, Luigi

    A theoretical study of a double C—H activation mechanism that deactivates a family of second generation Ru-based catalysts is presented. DFT calculations are used to rationalize the complex mechanistic pathway from the starting precatalyst to the experimentally characterized decomposition products. In particular, we show that all the intermediates proposed by Grubbs and coworkers are indeed possible intermediates in the deactivation pathway, although the sequence of steps is somewhat different

  13. Homobimetallic Ruthenium-N-Heterocyclic Carbene Complexes For Olefin Metathesis

    NASA Astrophysics Data System (ADS)

    Sauvage, Xavier; Demonceau, Albert; Delaude, Lionel

    In this chapter, the synthesis and catalytic activity towards olefin metathesis of homobimetallic ruthenium (Ru)-alkylidene, -cyclodiene or -arene complexes bearing phosphine or N-heterocyclic carbene (NHC) ligands are reviewed. Emphasis is placed on the last category of bimetallic compounds. Three representatives of this new type of molecular scaffold were investigated. Thus, [(p-cymene)Ru(m-Cl)3RuCl (h2-C2H4)(L)] complexes with L = PCy3 (15a), IMes (16a), or IMesCl2 (16b) were prepared. They served as catalyst precursors for cross-metathesis (CM) of various styrene derivatives. These experiments revealed the outstanding aptitude of complex 16a (and to a lesser extent of 16b) to catalyze olefin metathesis reactions. Contrary to monometallic Ru-arene complexes of the [RuCl2(p-cymene)(L)] type, the new homobimetallic species did not require the addition of a diazo compound nor visible light illumination to initiate the ring-opening metathesis of norbornene or cyclooctene. When diethyl 2,2-diallylmalonate and N,N-diallyltosylamide were exposed to 16a,b, a mixture of cycloisomerization and ring-closing metathesis (RCM) products was obtained in a nonselective way. Addition of phenylacetylene enhanced the metathetical activity while completely repressing the cycloisomerization process.

  14. Aromatizing olefin metathesis by ligand isolation inside a metal-organic framework.

    PubMed

    Vermeulen, Nicolaas A; Karagiaridi, Olga; Sarjeant, Amy A; Stern, Charlotte L; Hupp, Joseph T; Farha, Omar K; Stoddart, J Fraser

    2013-10-09

    The aromatizing ring-closing metathesis has been shown to take place inside an extended porous framework. Employing a combination of solvent-assisted linker exchange and postsynthesis modification using olefin metathesis, the noninterpenetrated SALEM-14 was formed and converted catalytically into PAH-MOF-1 with polycyclic aromatic hydrocarbon (PAH) pillars. The metal-organic framework in SALEM-14 prevents "intermolecular" olefin metathesis from occurring between the pillars in the presence of the first generation Hoveyda-Grubbs catalyst, while favoring the production of a PAH, which can be released from the framework under acidic conditions in dimethylsulfoxide.

  15. Controlled Ring-Opening Metathesis Polymerization by Molybdenum and Tungsten Alkylidene Complexes

    DTIC Science & Technology

    1988-07-29

    weights and low polydispersities (as low as 1.03) consistent with a living catalyst system employing 50, 100, 200, and 400 eq of monomer. The reactions are...secondary metathesis of polymer chains Bulky alkoxide ligands Wittig-like reaction Ring-opening metathesis polymerization (ROMP) Feast monomer Cyclic...olefins Retro Diels-Alder reaction Norbornene (NBE) Low temperature column chromatography Endo-,endo-5,6-dicarbomethoxynorbornene Discrete, soluble

  16. Enhanced Olefin Cross Metathesis Reactions: The Copper Iodide Effect

    PubMed Central

    Voigtritter, Karl; Ghorai, Subir

    2011-01-01

    Copper iodide has been shown to be an effective co-catalyst for the olefin cross metathesis reaction. In particular, it has both a catalyst stabilizing effect due to iodide ion, as well as copper(I)-based phosphine-scavenging properties that apply to use of the Grubbs-2 catalyst. A variety of Michael acceptors and olefinic partners can be cross-coupled under mild conditions in refluxing diethyl ether that avoid chlorinated solvents. This effect has also been applied to chemistry in water at room temperature using the new surfactant TPGS-750-M. PMID:21528868

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

    PubMed Central

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

    2011-01-01

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

  18. Prosodically Driven Metathesis in Mutsun

    ERIC Educational Resources Information Center

    Butler, Lynnika

    2013-01-01

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

  19. Tandem enyne metathesis-Diels-Alder reaction for construction of natural product frameworks.

    PubMed

    Rosillo, Marta; Domínguez, Gema; Casarrubios, Luis; Amador, Ulises; Pérez-Castells, Javier

    2004-03-19

    Enynes connected through aromatic rings are used as substrates for metathesis reactions. The reactivity of three ruthenium carbene complexes is compared. The resulting 1,3-dienes are suitable precursors of polycyclic structures via a Diels-Alder process. Some domino RCM-Diels-Alder reactions are performed, suggesting a possible beneficial effect of the ruthenium catalyst in the cycloaddition process. Other examples require Lewis acid cocatalyst. When applied to aromatic ynamines or enamines, a new synthesis of vinylindoles is achieved. Monitorization of several metathesis reactions with NMR shows the different behavior for ruthenium catalysts. New carbenic species are detected in some reactions with an important dependence on the solvent used.

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

    PubMed Central

    Marvey, Bassie B.

    2008-01-01

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

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

    PubMed

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

    2014-07-21

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

  2. Highly Z-Selective Metathesis Homocoupling of Terminal Olefins

    PubMed Central

    Jiang, Annie J.; Zhao, Yu; Schrock, Richard R.; Hoveyda, Amir H.

    2009-01-01

    Mo and W MonoAryloxide-Pyrrolide (MAP) olefin metathesis catalysts can couple terminal olefins to give as high as >98% Z-products in moderate to high yields with as little as 0.2% catalyst. Results are reported for 1-hexene, 1-octene, allylbenzene, allyltrimethylsilane, methyl-10-undecenoate, methyl-9-decenoate, allylB(pinacolate), allylOBenzyl, allylNHTosyl, and allylNHPh. It is proposed that high Z-selectivity is achieved because a large aryloxide only allows metallacyclobutanes to form that contain adjacent cis substituents and because isomerization of Z-product to E-product can be slow in that same steric environment. PMID:19919135

  3. Arylation and vinylation of alkenes based on unusual sequential semipinacol rearrangement/Grob fragmentation of allylic alcohols.

    PubMed

    Yuan, Dao-Yi; Tu, Yong-Qiang; Fan, Chun-An

    2008-10-03

    Alkenes can be stereoselectively arylated and vinylated without transition-metal catalyst under mild conditions through an interesting NBS-promoted semipinacol rearrangement and a subsequent unusual NaOH-mediated Grob fragmentation.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  5. Epoxidation catalyst and process

    DOEpatents

    Linic, Suljo; Christopher, Phillip

    2010-10-26

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

  6. Kinetically E-selective macrocyclic ring-closing metathesis.

    PubMed

    Shen, Xiao; Nguyen, Thach T; Koh, Ming Joo; Xu, Dongmin; Speed, Alexander W H; Schrock, Richard R; Hoveyda, Amir H

    2017-01-19

    Macrocyclic compounds are central to the development of new drugs, but preparing them can be challenging because of the energy barrier that must be surmounted in order to bring together and fuse the two ends of an acyclic precursor such as an alkene (also known as an olefin). To this end, the catalytic process known as ring-closing metathesis (RCM) has allowed access to countless biologically active macrocyclic organic molecules, even for large-scale production. Stereoselectivity is often critical in such cases: the potency of a macrocyclic compound can depend on the stereochemistry of its alkene; alternatively, one isomer of the compound can be subjected to stereoselective modification (such as dihydroxylation). Kinetically controlled Z-selective RCM reactions have been reported, but the only available metathesis approach for accessing macrocyclic E-olefins entails selective removal of the Z-component of a stereoisomeric mixture by ethenolysis, sacrificing substantial quantities of material if E/Z ratios are near unity. Use of ethylene can also cause adventitious olefin isomerization-a particularly serious problem when the E-alkene is energetically less favoured. Here, we show that dienes containing an E-alkenyl-B(pinacolato) group, widely used in catalytic cross-coupling, possess the requisite electronic and steric attributes to allow them to be converted stereoselectively to E-macrocyclic alkenes. The reaction is promoted by a molybdenum monoaryloxide pyrrolide complex and affords products at a yield of up to 73 per cent and an E/Z ratio greater than 98/2. We highlight the utility of the approach by preparing recifeiolide (a 12-membered-ring antibiotic) and pacritinib (an 18-membered-ring enzyme inhibitor), the Z-isomer of which is less potent than the E-isomer. Notably, the 18-membered-ring moiety of pacritinib-a potent anti-cancer agent that is in advanced clinical trials for treating lymphoma and myelofibrosis-was prepared by RCM carried out at a substrate

  7. Kinetically E-selective macrocyclic ring-closing metathesis

    NASA Astrophysics Data System (ADS)

    Shen, Xiao; Nguyen, Thach T.; Koh, Ming Joo; Xu, Dongmin; Speed, Alexander W. H.; Schrock, Richard R.; Hoveyda, Amir H.

    2017-01-01

    Macrocyclic compounds are central to the development of new drugs, but preparing them can be challenging because of the energy barrier that must be surmounted in order to bring together and fuse the two ends of an acyclic precursor such as an alkene (also known as an olefin). To this end, the catalytic process known as ring-closing metathesis (RCM) has allowed access to countless biologically active macrocyclic organic molecules, even for large-scale production. Stereoselectivity is often critical in such cases: the potency of a macrocyclic compound can depend on the stereochemistry of its alkene; alternatively, one isomer of the compound can be subjected to stereoselective modification (such as dihydroxylation). Kinetically controlled Z-selective RCM reactions have been reported, but the only available metathesis approach for accessing macrocyclic E-olefins entails selective removal of the Z-component of a stereoisomeric mixture by ethenolysis, sacrificing substantial quantities of material if E/Z ratios are near unity. Use of ethylene can also cause adventitious olefin isomerization—a particularly serious problem when the E-alkene is energetically less favoured. Here, we show that dienes containing an E-alkenyl–B(pinacolato) group, widely used in catalytic cross-coupling, possess the requisite electronic and steric attributes to allow them to be converted stereoselectively to E-macrocyclic alkenes. The reaction is promoted by a molybdenum monoaryloxide pyrrolide complex and affords products at a yield of up to 73 per cent and an E/Z ratio greater than 98/2. We highlight the utility of the approach by preparing recifeiolide (a 12-membered-ring antibiotic) and pacritinib (an 18-membered-ring enzyme inhibitor), the Z-isomer of which is less potent than the E-isomer. Notably, the 18-membered-ring moiety of pacritinib—a potent anti-cancer agent that is in advanced clinical trials for treating lymphoma and myelofibrosis—was prepared by RCM carried out at a

  8. Photocatalytic Dehydrogenative Cross-Coupling of Alkenes with Alcohols or Azoles without External Oxidant.

    PubMed

    Yi, Hong; Niu, Linbin; Song, Chunlan; Li, Yiying; Dou, Bowen; Singh, Atul K; Lei, Aiwen

    2017-01-19

    Direct cross-coupling between alkenes/R-H or alkenes/RXH is a dream reaction, especially without external oxidants. Inputting energy by photocatalysis and employing a cobalt catalyst as a two-electron acceptor, a direct C-H/X-H cross-coupling with H2 evolution has been achieved for C-O and C-N bond formation. A new radical alkenylation using alkene as the redox compound is presented. A wide range of aliphatic alcohols-even long chain alcohols-are tolerated well in this system, providing a new route to multi-substituted enol ether derivatives using simple alkenes. Additionally, this protocol can also be used for N-vinylazole synthesis. Mechanistic insights reveal that the cobalt catalyst oxidizes the photocatalyst to revive the photocatalytic cycle.

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-03-04

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

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

    DOEpatents

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

    2010-10-12

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

  12. Synthesis of interlocked molecules by olefin metathesis

    NASA Astrophysics Data System (ADS)

    Clark, Paul Gregory

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

  13. Ligand development in the Ni-catalyzed hydrocyanation of alkenes.

    PubMed

    Bini, Laura; Müller, Christian; Vogt, Dieter

    2010-11-28

    The addition of HCN to alkenes is a very useful reaction for the synthesis of functional organic substrates. Industrially the nickel-catalyzed hydrocyanation has gained considerable importance mainly because of the production of adiponitrile in the DuPont process. In this process the hydrocyanation of butadiene is carried out using aryl phosphite-modified nickel catalyst. Since the performance of organo-transition metal complexes is largely determined by the ligand environment of the metal, fundamental understanding and ligand development is of pivotal importance for any progress. This feature article gives an account of the development and application of different mono- and bidentate phosphorus-based ligands in the Ni-catalyzed hydrocyanation reaction of alkenes. Special attention will be paid to the development of insight and understanding of the ligand structural and electronic properties towards the improvement of the catalyst performance in terms of stability, activity, and selectivity.

  14. Microanalysis of Alkenes by Ozonolysis

    ERIC Educational Resources Information Center

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

    1975-01-01

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

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

    DOEpatents

    Angelici, R.J.; Gao, H.

    1998-08-04

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

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

    DOEpatents

    Angelici, Robert J.; Gao, Hanrong

    1998-08-04

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

  17. Lewis basicity modulation of N-heterocycles: a key for successful cross-metathesis.

    PubMed

    Lafaye, Kevin; Nicolas, Lionel; Guérinot, Amandine; Reymond, Sébastien; Cossy, Janine

    2014-10-03

    Cross-metathesis involving N-heteroaromatic olefinic derivatives is disclosed. The introduction of an appropriate substituent on the heteroaromatic ring decreases the Lewis basicity of the nitrogen atom, thus preventing the deactivation of the ruthenium-centered catalyst. The reaction is quite general in terms of both N-heterocycles and olefinic partners.

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

    ERIC Educational Resources Information Center

    Schepmann, Hala G.; Mynderse, Michelle

    2010-01-01

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

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

    PubMed

    Mattis, Clayton E; Mootoo, David R

    2016-06-24

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

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

    PubMed

    Mattis, Clayton E; Mootoo, David R

    2016-04-29

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

  1. Single-Site Cobalt Catalysts at New Zr 82 -O) 82 -OH) 4 Metal-Organic Framework Nodes for Highly Active Hydrogenation of Alkenes, Imines, Carbonyls, and Heterocycles

    SciTech Connect

    Ji, Pengfei; Manna, Kuntal; Lin, Zekai; Urban, Ania; Greene, Francis X.; Lan, Guangxu; Lin, Wenbin

    2016-09-21

    We report here the synthesis of robust and porous metal–organic frameworks (MOFs), M-MTBC (M = Zr or Hf), constructed from the tetrahedral linker methane-tetrakis(p-biphenylcarboxylate) (MTBC) and two types of secondary building units (SBUs): cubic M82-O)82-OH)4 and octahedral M6(μ3-O)43-OH)4. While the M6-SBU is isostructural with the 12-connected octahedral SBUs of UiO-type MOFs, the M8-SBU is composed of eight MIV ions in a cubic fashion linked by eight μ2-oxo and four μ2-OH groups. The metalation of Zr-MTBC SBUs with CoCl2, followed by treatment with NaBEt3H, afforded highly active and reusable solid Zr-MTBC-CoH catalysts for the hydrogenation of alkenes, imines, carbonyls, and heterocycles. Zr-MTBC-CoH was impressively tolerant of a range of functional groups and displayed high activity in the hydrogenation of tri- and tetra-substituted alkenes with TON > 8000 for the hydrogenation of 2,3-dimethyl-2-butene. Our structural and spectroscopic studies show that site isolation of and open environments around the cobalt-hydride catalytic species at Zr8-SBUs are responsible for high catalytic activity in the hydrogenation of a wide range of challenging substrates. MOFs thus provide a novel platform for discovering and studying new single-site base-metal solid catalysts with enormous potential for sustainable chemical synthesis.

  2. Zirconium-Catalyzed Asymmetric Carboalumination of Unactivated Terminal Alkenes.

    PubMed

    Xu, Shiqing; Negishi, Ei-Ichi

    2016-10-18

    Carbometalation of alkenes with stereocontrol offers an important opportunity for asymmetric C-C bond formation. However, the scope of catalytic stereoselective carbometalation of alkenes had until recently been limited to electronically biased alkenes or those with the presence of directing groups or other auxiliary functionalities to overcome the challenge associated with regio- and stereoselectivity. Catalytic asymmetric carbometalation of unactivated alkenes on the other hand remained as a formidable challenge. To address this long-standing problem, we sought to develop Zr-catalyzed asymmetric carboalumination of alkenes (namely, ZACA reaction) encouraged by our discovery of Zr-catalyzed alkyne carboalumination in 1978. Zr-catalyzed methylalumination of alkynes (ZMA) shows high regioselectivity and nearly perfect stereoselectivity. Its mechanistic studies have revealed that the ZMA reaction involves acyclic carbometalation with "superacidic" bimetallic reagents generated by interaction between two Lewis acids, i.e., alkylalanes and 16-electron zirconocene derivatives through dynamic polarization and ate complexation, affectionately termed as the "two-is-better-than-one" principle. With the encouraging results of Zr-catalyzed carboalumination of alkynes in hand, we sought to develop its alkene version for discovering a catalytic asymmetric C-C bond-forming reaction by using alkylalanes and suitable chiral zirconocene derivatives, which would generate "superacidic" bimetallic species to promote the desired carbometalation of alkenes. However, this proved to be quite challenging. Three major competing side reactions occur, i.e., (i) β-H transfer hydrometalation, (ii) bimetallic cyclic carbometalation, and (iii) Ziegler-Natta polymerization. The ZACA reaction was finally discovered by employing Erker's (-)-(NMI)2ZrCl2 as the catalyst and chlorinated hydrocarbon as solvent to suppress the undesired side reactions mentioned above. The ZACA reaction has evolved as a

  3. Cross metathesis for the synthesis of novel C-sialosides.

    PubMed

    Meinke, Sebastian; Thiem, Joachim

    2008-07-21

    Cross metathesis of both anomers of C-allyl sialoside (3alpha/3beta) with styrene catalyzed by the second generation Grubbs or Hoveyda-Grubbs catalysts gave the corresponding aryl derivatives (4alpha/4beta) in virtually quantitative yields. The products were hydrogenated to model compounds 5alpha/5beta. Similarly, reaction of the alpha-anomer 3alpha with galactose derivative 8 gave the olefin-linked disaccharide mimetic 9. Following hydrogenation and deprotection, the ethylene-bridged Neu5Acalpha(2-->6)Gal analogue 11 could be obtained.

  4. Well-defined silica-supported zirconium-imido complexes mediated heterogeneous imine metathesis.

    PubMed

    Hamzaoui, Bilel; Pelletier, Jérémie D A; Abou-Hamad, Edy; Basset, Jean-Marie

    2016-03-28

    Upon prolonged thermal exposure under vacuum, a well-defined single-site surface species [([triple bond, length as m-dash]Si-O-)Zr(NEt2)3] () evolves into an ethylimido complex [([triple bond, length as m-dash]Si-O-)Zr([double bond, length as m-dash]NEt)NEt2] (). Reactions of with an imine substrate result in imido/imine ([double bond, length as m-dash]NRi, R: Et, Ph) exchange (metathesis) with the formation of [([triple bond, length as m-dash]Si-O-)Zr([double bond, length as m-dash]NPh)NEt2] (). Compounds and effectively catalyze imine/imine cross-metathesis and are thus considered as the first heterogeneous catalysts active for imine metathesis.

  5. The arene–alkene photocycloaddition

    PubMed Central

    Streit, Ursula

    2011-01-01

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

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

    SciTech Connect

    Zhu, Weiming.

    1991-01-01

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

  7. Novel chiral (salen)Mn(III) complexes containing a calix[4]arene unit in 1,3-alternate conformation as catalysts for enantioselective epoxidation reactions of (Z)-aryl alkenes.

    PubMed

    Bonaccorso, Carmela; Brancatelli, Giovanna; Ballistreri, Francesco P; Geremia, Silvano; Pappalardo, Andrea; Tomaselli, Gaetano A; Toscano, Rosa M; Sciotto, Domenico

    2014-02-07

    Two new chiral calix[4]arene-salen ligands 1a,b, based on calix[4]arene platforms in 1,3-alternate conformation, have been prepared by a new general synthetic pathway. Their Mn(III) complexes, 3a,b have shown fairly good efficiency in the asymmetric epoxidation of styrene and substituted styrenes, whereas excellent catalytic activity and selectivity were observed with rigid bicyclic alkenes, namely 1,2-dihydro-naphthalene and substituted 2,2'-dimethyl-chromene. The higher catalytic properties of 3a may be ascribed to the more rigid and inherently chiral structure as proved by molecular modelling, NMR spectroscopy and X-ray data of the similarly structured UO2 complexes 2a,b.

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

    PubMed

    Chirik, Paul J

    2015-06-16

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

  9. Microwave-Assisted Olefin Metathesis

    NASA Astrophysics Data System (ADS)

    Nicks, François; Borguet, Yannick; Sauvage, Xavier; Bicchielli, Dario; Delfosse, Sébastien; Delaude, Lionel; Demonceau, Albert

    Since the first reports on the use of microwave irradiation to accelerate organic chemical transformations, a plethora of papers have been published in this field. In most examples, microwave heating has been shown to dramatically reduce reaction times, increase product yields, and enhance product purity by reducing unwanted side reactions compared to conventional heating methods. The present contribution aims at illustrating the advantages of this technology in olefin metathesis and, when data are available, at comparing microwave-heated and conventionally heated experiments

  10. Catalytic σ-Bond Metathesis

    NASA Astrophysics Data System (ADS)

    Reznichenko, Alexander L.; Hultzsch, Kai C.

    This account summarizes information on recently reported applications of organo-rare-earth metal complexes in various catalytic transformations of small molecules. The σ-bond metathesis at d0rare-earth metal centers plays a pivotal role in carbon-carbon and carbon-heteroatom bond forming processes. Relevant mechanistic details are discussed and the focus of the review lies in practical applications of organo-rare-earth metal complexes.

  11. Polymer enzyme conjugates as chiral ligands for sharpless dihydroxylation of alkenes in organic solvents.

    PubMed

    Konieczny, Stefan; Leurs, Melanie; Tiller, Joerg C

    2015-01-02

    Conjugates of enzymes and poly(2-methyloxazoline) were used as organosoluble amphiphilic polymer nanocontainers for dissolving osmate, thereby converting the enzymes into organosoluble artificial metalloenzymes. These were shown to catalyze the dihydroxylation of different alkenes with high enantioselectivity. The highest selectivities, found for osmate complexed with laccase polymer-enzyme conjugates (PECs), even exceed those of classical Sharpless catalysts.

  12. Palladium-catalyzed highly regioselective hydroaminocarbonylation of aromatic alkenes to branched amides.

    PubMed

    Zhu, Jinping; Gao, Bao; Huang, Hanmin

    2017-03-22

    Pd(t-Bu3P)2 has been successfully identified as an efficient catalyst for the hydroaminocarbonylation of aromatic alkenes to branched amides under relatively mild reaction conditions. With hydroxylamine hydrochloride as an additive, both aliphatic and aromatic amines could be used as coupling partners for the present reaction, leading to production of branched amides in high yields with excellent regioselectivities.

  13. Highly selective bis(imino)pyridine iron-catalyzed alkene hydroboration.

    PubMed

    Obligacion, Jennifer V; Chirik, Paul J

    2013-06-07

    Bis(imino)pyridine iron dinitrogen complexes have been shown to promote the anti-Markovnikov catalytic hydroboration of terminal, internal, and geminal alkenes with high activity and selectivity. The isolated iron dinitrogen compounds offer distinct advantages in substrate scope and overall performance over known precious metal catalysts and previously reported in situ generated iron species.

  14. 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.

  15. Catalytic living ring-opening metathesis polymerization

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  16. Synthesis of Catenane Structures via Ring-Closing Metathesis.

    PubMed

    Weck, Marcus; Mohr, Bernhard; Sauvage, Jean-Pierre; Grubbs, Robert H.

    1999-07-23

    This study presents a detailed description of a synthetic strategy to obtain catenane architectures through ring-closing metathesis. The approach is based on phenanthroline-based ligands containing terminal olefinic units that were designed to coordinate in a tetrahedral arrangement around a copper atom. Treatment of the assembled copper complexes with ruthenium catalyst 1 resulted in [2]catenates in high yields of 88-92%. Demetalation produced the corresponding [2]catenand in nearly quantitative yields. Hydrogenation of the catenates with Crabtree's catalyst and subsequent demetalation yielded fully saturated catenands. The presently described procedure makes [2]catenanes very accessible since the synthetic route consists of six steps (Schemes 2 and 4) from commercially available 1,10-phenanthroline, the overall yield being 51%.

  17. Rhodium-catalyzed enantioselective cyclopropanation of electron deficient alkenes

    PubMed Central

    Wang, Hengbin; Guptill, David M.; Alvarez, Adrian Varela

    2013-01-01

    The rhodium-catalyzed reaction of electron-deficient alkenes with substituted aryldiazoacetates and vinyldiazoacetates results in highly stereoselective cyclopropanations. With adamantylglycine derived catalyst Rh2(S-TCPTAD)4, high asymmetric induction (up to 98% ee) can be obtained with a range of substrates. Computational studies suggest that the reaction is facilitated by weak interaction between the carbenoid and the substrate carbonyl but subsequently proceeds via different pathways depending on the nature of the carbonyl.. Acrylates and acrylamides result in the formation of cyclopropanation products while the use of unsaturated aldehydes and ketones results in the formation of epoxides. PMID:24049630

  18. Catalytic hydration of terminal alkenes to primary alcohols.

    PubMed

    Jensen, C M; Trogler, W C

    1986-09-05

    Direct catalytic hydration of terminal alkenes to primary alcohols would be an inexpensive route to industrially useful alcohols and a convenient synthetic route for the synthesis of terminal alcohols in general. The reaction between trans- PtHCl(PMe(3))(2) (where Me = CH(3)) and sodium hydroxide in a one-to-one mixture of water and 1-hexene yields a species that, at 60 degrees C and in the presence of the phasetransfer catalyst benzyltriethylammonium chloride, catalyzes selective hydration of 1-hexene to n-hexanol at a rate of 6.9 +/- 0.2 turnovers per hour. Hydration of 1-dodecene to n-dodecanol occurs at a rate of 8.3 +/- 0.4 turnovers per hour at 100 degrees C. Deuterium labeling experiments with trans-PtDCl(PMe(3))(2) show that hydration involves reductive elimination of a C-H bond. At low hydroxide concentrations (<8 equivalents), hydration of the water-soluble olefin 3-butene-1-ol to 1,4-butanediol exhibited a first-order dependence on hydroxide concentration for loss of catalytic activity. This suggests that hydroxide attacks the coordinated alkene slowly. At high hydroxide concentrations, the rate of catalysis was hydroxide-independent and first order in alkene. Substitution of coordinated water (k(1) = 9.3 +/- 0.5 x 10(-3) liters per mol per second) appears to be limitng under these conditions.

  19. Homogeneous Pd-catalyzed transformation of terminal alkenes into primary allylic alcohols and derivatives.

    PubMed

    Tomita, Ren; Mantani, Kohei; Hamasaki, Akiyuki; Ishida, Tamao; Tokunaga, Makoto

    2014-08-04

    Synthesis of primary alcohols from terminal alkenes is an important process in both bulk and fine chemical syntheses. Herein, a homogeneous Pd-complex-catalyzed transformation of terminal alkenes into primary allylic alcohols, by using 5 mol % [Pd(PPh3)4] as a catalyst, and H2O, CO2, and quinone derivatives as reagents, is reported. When alcohols were used instead of H2O, allylic ethers were obtained. A proposed mechanism includes the addition of oxygen nucleophiles at the less-hindered terminal position of π-allyl Pd intermediates.

  20. A mild oxidative aryl radical addition into alkenes by aerobic oxidation of arylhydrazines.

    PubMed

    Taniguchi, Tsuyoshi; Zaimoku, Hisaaki; Ishibashi, Hiroyuki

    2011-04-04

    A mild and practical oxyarylation of alkenes by oxidative radical addition has been developed by using aerobic oxidation of hydrazine compounds. The use of a catalytic amount of potassium ferrocyanide trihydrate (K(4)[Fe(CN)(6)]⋅3H(2)O) and water accelerated this radical reaction to give peroxides or alcohols from simple alkenes in good yields. The environmentally friendly and economical radical reactions were achieved at room temperature in the presence of iron catalyst, oxygen gas, and water. A method involving aniline as a radical precursor is also described.

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

    PubMed

    Kawamura, Shintaro; Sodeoka, Mikiko

    2016-07-18

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

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

    PubMed

    Margrey, Kaila A; Nicewicz, David A

    2016-09-20

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

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

    EPA Science Inventory

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

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

    PubMed

    Yao, Q

    2001-06-28

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

  5. Synthesis by Ring-Closing Metathesis and Cytotoxic Evaluation of Novel Thienylmacrolactones

    PubMed Central

    Krauss, Jürgen; Köbler, Daniela; Miller, Verena; Bracher, Franz

    2012-01-01

    This paper describes the synthesis and biological evaluation of macrolactones containing a thienyl substituent as simple analogues of epothilones. The compounds were prepared in a brief and efficient manner from thiophene-2-carbaldehyde using a ring-closing metathesis with Grubbs I or Grubbs II catalyst as the key step. The target lactones showed only insignificant cytotoxicity, while an intermediate simple thienyl carbinol showed very promising cytotoxicity. PMID:22396902

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

    DOEpatents

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

    2014-12-16

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

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

    DOEpatents

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

    2014-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Zhu, Jie S.; Shon, Young-Seok

    2015-10-01

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

  9. Organometallic polymerization catalysts

    SciTech Connect

    Waymouth, R.M.

    1993-12-31

    Well-defined transition metal catalysts have resulted in exciting new opportunities in polymer synthesis. The stereochemistry of vinyl polymers can be rationally controlled with choice of the appropriate catalysts. Studies with optically active catalyst precursors have revealed considerable information on the absolute stereochemistry of olefin polymerization and have led to the synthesis of novel chiral polyolefins. The development of homogeneous olefin metathesis catalysts has also led to a variety of well-defined new polymer structures with controlled molecular weight and molecular weight distribution. Recent advances in understanding the mechanisms and stereochemistry of homogeneous transition metal catalyzed polymerization will be discussed. The ability to control polymer structure through catalyst design presents exciting opportunities in the synthesis of {open_quotes}tailor-made{close_quotes} macromolecules.

  10. A design-of-experiments approach for the optimization and understanding of the cross-metathesis reaction of methyl ricinoleate with methyl acrylate.

    PubMed

    Ho, Thao T T; Jacobs, Tina; Meier, Michael A R

    2009-01-01

    A design-of-experiments approach for the investigation of the cross-metathesis of methyl ricinoleate with methyl acrylate is described. Two second-generation metathesis initiators were studied using different reaction conditions, revealing optimal reaction conditions for each catalyst. Interestingly, the two catalysts showed completely different temperature response profiles. As a result of these investigations, suitable reaction conditions for the sustainable production of two value-added chemical intermediates were derived. Moreover, the design-of-experiments approach provided valuable information for a thorough understanding of catalytic reactions that would be more difficult to obtain by classic approaches.

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

    PubMed Central

    Mutti, Francesco G.

    2012-01-01

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

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

    SciTech Connect

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

    2014-12-17

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

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

    DOE PAGES

    Marx, Vanessa M.; Sullivan, Alexandra H.; Melaimi, Mohand; ...

    2014-12-17

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

  14. Remote functionalization through alkene isomerization

    NASA Astrophysics Data System (ADS)

    Vasseur, Alexandre; Bruffaerts, Jeffrey; Marek, Ilan

    2016-03-01

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

  15. Remote functionalization through alkene isomerization.

    PubMed

    Vasseur, Alexandre; Bruffaerts, Jeffrey; Marek, Ilan

    2016-03-01

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

  16. Electrochemical intramolecular aminooxygenation of unactivated alkenes.

    PubMed

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

    2014-09-26

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

  17. Carbonylations of alkenes with CO surrogates.

    PubMed

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

    2014-06-16

    Alkene carbonylation reactions are important for the production of value-added bulk and fine chemicals. Nowadays, all industrial carbonylation processes make use of highly toxic and flammable carbon monoxide. In fact, these properties impede the wider use of carbonylation reactions in industry and academia. Hence, performing carbonylations without the use of CO is highly desired and will contribute to the further advancement of sustainable chemistry. Although the use of carbon monoxide surrogates in alkene carbonylation reactions has been reported intermittently in the last 30 years, only recently has this area attracted significant interest. This Minireview summarizes carbonylation reactions of alkenes using different carbon monoxide surrogates.

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

    PubMed

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

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

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

  20. Copper-Catalyzed Three-Component Annulations of Alkenes, Nitrosoarenes, and N-Hydroxyallylamines To Form Fused Oxazinane/Isoxazolidine Heterocycles.

    PubMed

    Kawade, Rahul Kisan; Liu, Rai-Shung

    2017-02-13

    One-pot cascade annulations among nitrosoarenes, alkenes, and N-hydroxyallylamines have been achieved with CuCl/O2 catalysts, forming fused oxazinane/isoxazolidine heterocycles with excellent diastereoselectivity (d.r. >20:1). To enhance the synthetic utility, we developed a successive cleavage of the two N-O bonds of the resulting heterocycles. A mechanism involving dipolar [3+2] cycloadditions of nitrone intermediates with their tethered alkenes is postulated for formation of these heterocycles.

  1. Epoxidation of alkenes and oxidation of alcohols with hydrogen peroxide catalyzed by a manganese(V) nitrido complex.

    PubMed

    Kwong, Hoi-Ki; Lo, Po-Kam; Lau, Kai-Chung; Lau, Tai-Chu

    2011-04-14

    The manganese(V) nitrido complex (PPh(4))(2)[Mn(N)(CN)(4)] is an active catalyst for alkene epoxidation and alcohol oxidation using H(2)O(2) as an oxidant. The catalytic oxidation is greatly enhanced by the addition of just one equivalent of acetic acid. The oxidation of ethene by this system has been studied computationally by the DFT method.

  2. Enantioselective C-H bond addition of pyridines to alkenes catalyzed by chiral half-sandwich rare-earth complexes.

    PubMed

    Song, Guoyong; O, Wylie W N; Hou, Zhaomin

    2014-09-03

    Cationic half-sandwich scandium alkyl complexes bearing monocyclopentadienyl ligands embedded in chiral binaphthyl backbones act as excellent catalysts for the enantioselective C-H bond addition of pyridines to various 1-alkenes, leading to formation of a variety of enantioenriched alkylated pyridine derivatives in high yields and excellent enantioselectivity (up to 98:2 er).

  3. Asymmetric cyclopropanation of alkenes catalyzed by a rhodium {open_quotes}chiral fortress{close_quotes} porphyrin

    SciTech Connect

    O`Malley, S.; Kodadek, T.

    1992-06-01

    The authors investigated the use of chiral rhodium porphyrin catalysts for the production of predominantly syn isomers in the cyclopropanation of alkenes. The reactions display good diastereoselectivity on some cases, but only modest enantioselectivities are observed. 15 refs., 3 figs., 1 tab.

  4. Selective partial hydrogenation of alkynes to (Z)-alkenes with ionic liquid-doped nickel nanocatalysts at near ambient conditions.

    PubMed

    Konnerth, Hannelore; Prechtl, Martin H G

    2016-07-12

    A selective hydrogenation method for forming (Z)-alkenes from alkynes has been developed using a catalyst system of cheap Ni-NPs in a nitrile functionalised imidazolium based ionic liquid (IL) operating under very mild reaction conditions of 30-50 °C and 1-4 bar H2 pressure.

  5. Tandem Z-selective cross metathesis – dihydroxylation for the synthesis of anti-1,2-diols**

    PubMed Central

    Dornan, Peter K.; Wickens, Zachary K.

    2015-01-01

    A stereoselective synthesis of anti-1,2-diols has been developed using a multitasking Ru-catalyst in an assisted tandem catalysis protocol. A cyclometalated ruthenium complex catalyzes first a Z-selective cross metathesis of two terminal olefins followed by a stereospecific dihydroxylation. Both steps are catalyzed by Ru, as the Ru-complex is converted to a dihydroxylation catalyst upon addition of NaIO4. A variety of olefins are transformed into valuable highly functionalized and stereodefined molecules. Mechanistic experiments are performed to probe the nature of the oxidation step and catalyst inhibition pathways. These experiments point the way to more broadly applicable tandem catalytic transformations. PMID:25914354

  6. Preparation of cadmium selenide-polyolefin composites from functional phosphine oxides and ruthenium-based metathesis.

    PubMed

    Skaff, Habib; Ilker, M Firat; Coughlin, E Bryan; Emrick, Todd

    2002-05-22

    Cadmium selenide nanoparticles, prepared by known methods, were stabilized with functional phosphine oxide 1, then used to support the polymerization of cyclic olefins radially outward from the surface by ruthenium-catalyzed ring-opening metathesis polymerization (ROMP). The conversion of compound 1 into the new metathesis catalyst 3 by carbene exchange and the subsequent polymerization of cyclic olefins were observed spectroscopically by (1)H NMR to afford for example CdSe-polycyclooctene composite 6. Transmission electron micrographs on thin films of these composites showed good nanoparticle dispersion. This is in stark contrast to the substantial nanoparticle aggregation observed when similar polymerizations were performed in the presence of conventional TOPO-covered nanoparticles. The methods reported here to prepare composite product 6 are applicable to other cyclic olefins, and suggest that this chemistry will be useful for incorporating CdSe nanoparticles into a wide variety of polymer matrices.

  7. Alkene anti-Dihydroxylation with Malonoyl Peroxides.

    PubMed

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

    2015-10-16

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed Central

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

    2013-01-01

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

  11. High selectivity production of propylene from 2-butene: non-degenerate pathways to convert symmetric olefins via olefin metathesis.

    PubMed

    Mazoyer, Etienne; Szeto, Kai C; Basset, Jean-Marie; Nicholas, Christopher P; Taoufik, Mostafa

    2012-04-14

    The first example of propylene production from 2-butene in promising yield is described by reacting trans-2-butene over tungsten hydrides precursor W-H/Al(2)O(3) at 150 °C and different pressures in a continuous flow reactor. The tungsten carbene-hydride active site operates as a "bi-functional catalyst" through the disfavoured 2-butene isomerisation on W-hydride and 2-butenes/1-butene cross-metathesis on W-carbene.

  12. Directed evolution of artificial metalloenzymes for in vivo metathesis.

    PubMed

    Jeschek, Markus; Reuter, Raphael; Heinisch, Tillmann; Trindler, Christian; Klehr, Juliane; Panke, Sven; Ward, Thomas R

    2016-09-29

    The field of biocatalysis has advanced from harnessing natural enzymes to using directed evolution to obtain new biocatalysts with tailor-made functions. Several tools have recently been developed to expand the natural enzymatic repertoire with abiotic reactions. For example, artificial metalloenzymes, which combine the versatile reaction scope of transition metals with the beneficial catalytic features of enzymes, offer an attractive means to engineer new reactions. Three complementary strategies exist: repurposing natural metalloenzymes for abiotic transformations; in silico metalloenzyme (re-)design; and incorporation of abiotic cofactors into proteins. The third strategy offers the opportunity to design a wide variety of artificial metalloenzymes for non-natural reactions. However, many metal cofactors are inhibited by cellular components and therefore require purification of the scaffold protein. This limits the throughput of genetic optimization schemes applied to artificial metalloenzymes and their applicability in vivo to expand natural metabolism. Here we report the compartmentalization and in vivo evolution of an artificial metalloenzyme for olefin metathesis, which represents an archetypal organometallic reaction without equivalent in nature. Building on previous work on an artificial metallohydrolase, we exploit the periplasm of Escherichia coli as a reaction compartment for the 'metathase' because it offers an auspicious environment for artificial metalloenzymes, mainly owing to low concentrations of inhibitors such as glutathione, which has recently been identified as a major inhibitor. This strategy facilitated the assembly of a functional metathase in vivo and its directed evolution with substantially increased throughput compared to conventional approaches that rely on purified protein variants. The evolved metathase compares favourably with commercial catalysts, shows activity for different metathesis substrates and can be further evolved in

  13. Directed evolution of artificial metalloenzymes for in vivo metathesis

    NASA Astrophysics Data System (ADS)

    Jeschek, Markus; Reuter, Raphael; Heinisch, Tillmann; Trindler, Christian; Klehr, Juliane; Panke, Sven; Ward, Thomas R.

    2016-09-01

    The field of biocatalysis has advanced from harnessing natural enzymes to using directed evolution to obtain new biocatalysts with tailor-made functions. Several tools have recently been developed to expand the natural enzymatic repertoire with abiotic reactions. For example, artificial metalloenzymes, which combine the versatile reaction scope of transition metals with the beneficial catalytic features of enzymes, offer an attractive means to engineer new reactions. Three complementary strategies exist: repurposing natural metalloenzymes for abiotic transformations; in silico metalloenzyme (re-)design; and incorporation of abiotic cofactors into proteins. The third strategy offers the opportunity to design a wide variety of artificial metalloenzymes for non-natural reactions. However, many metal cofactors are inhibited by cellular components and therefore require purification of the scaffold protein. This limits the throughput of genetic optimization schemes applied to artificial metalloenzymes and their applicability in vivo to expand natural metabolism. Here we report the compartmentalization and in vivo evolution of an artificial metalloenzyme for olefin metathesis, which represents an archetypal organometallic reaction without equivalent in nature. Building on previous work on an artificial metallohydrolase, we exploit the periplasm of Escherichia coli as a reaction compartment for the ‘metathase’ because it offers an auspicious environment for artificial metalloenzymes, mainly owing to low concentrations of inhibitors such as glutathione, which has recently been identified as a major inhibitor. This strategy facilitated the assembly of a functional metathase in vivo and its directed evolution with substantially increased throughput compared to conventional approaches that rely on purified protein variants. The evolved metathase compares favourably with commercial catalysts, shows activity for different metathesis substrates and can be further evolved in

  14. Efficient addition of alcohols, amines and phenol to unactivated alkenes by Au(III) or Pd(II) stabilized by CuCl2.

    PubMed

    Zhang, Xin; Corma, Avelino

    2008-01-21

    The nucleophilic addition of alcohols, amines and phenol to unactivated alkenes catalyzed by cationic gold and palladium becomes limited due to the fast reduction into metallic gold under reaction conditions. The presence of CuCl2 retards the reduction of Au(III) and Pd", strongly increasing the turnover number of gold and palladium catalysts. It is shown that new Au(III)-CuCl2 and Pd(II)-CuCl2 catalysts are active and selective for the nucleophilic addition of alcohols, amines and phenol to unactivated alkenes.

  15. Stereoselective Access to Z- and E-Macrocycles by Ruthenium- Catalyzed Z-Selective Ring-Closing Metathesis and Ethenolysis

    PubMed Central

    Marx, Vanessa M.; Herbert, Myles B.; Keitz, Benjamin K.; Grubbs, Robert H.

    2013-01-01

    The first report of Z-selective macrocyclizations using a ruthenium-based metathesis catalyst is described. Selectivity for Z-macrocycles is consistently high for a diverse set of substrates with a variety of functional groups and ring sizes. The same catalyst was also employed for the Z-selective ethenolysis of a mixture of E and Z macrocycles, providing the pure E-isomer. Notably, only an atmospheric pressure of ethylene was required. These methodologies were successfully applied to the construction of several olfactory macrocycles, as well as the formal total synthesis of the cytotoxic alkaloid motuporamine C. PMID:23244210

  16. Hydroxyl-directed stereoselective diboration of alkenes.

    PubMed

    Blaisdell, Thomas P; Caya, Thomas C; Zhang, Liang; Sanz-Marco, Amparo; Morken, James P

    2014-07-02

    An alkoxide-catalyzed directed diboration of alkenyl alcohols is described. This reaction occurs in a stereoselective fashion and is demonstrated with cyclic and acyclic homoallylic and bishomoallylic alcohol substrates. After oxidation, the reaction generates 1,2-diols such that the process represents a method for the stereoselective directed dihydroxylation of alkenes.

  17. Alkene epoxidation employing metal nitro complexes

    DOEpatents

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

    1982-07-15

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

  18. Catalytic intermolecular alkene oxyamination with nitrenes.

    PubMed

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

    2014-07-14

    The Rh(II)-catalyzed intermolecular addition of nitrenes to aromatic and aliphatic alkenes provides vicinal amino alcohols with yields of up to 95 % and complete regioselectivity. This 1,2-oxyamination reaction involves the formation of an aziridine intermediate that undergoes in situ ring opening. The latter is induced by the Rh-bound nitrene that behaves as a Lewis acid.

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

    PubMed

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

    2013-12-16

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

  20. Copper(I)-induced amplification of a [2]catenane in a virtual dynamic library of macrocyclic alkenes.

    PubMed

    Berrocal, José Augusto; Nieuwenhuizen, Marko M L; Mandolini, Luigi; Meijer, E W; Di Stefano, Stefano

    2014-08-28

    Olefin cross-metathesis of diluted dichloromethane solutions (≤0.15 M) of the 28-membered macrocyclic alkene C1, featuring a 1,10-phenanthroline moiety in the backbone, as well as of catenand 1, composed of two identical interlocked C1 units, generates families of noninterlocked oligomers Ci. The composition of the libraries is strongly dependent on the monomer concentration, but independent of whether C1 or 1 is used as feedstock, as expected for truly equilibrated systems. Accordingly, the limiting value 0.022 M approached by the equilibrium concentration of C1 when the total monomer concentration approaches the critical value, as predicted by the Jacobson-Stockmayer theory, provides a reliable estimate of the thermodynamically effective molarity. Catenand 1 behaves as a virtual component of the dynamic libraries, in that there is no detectable trace of its presence in the equilibrated mixtures, but becomes the major component - in the form of its copper(I) complex - when olefin cross-metathesis is carried out in the presence of a copper(I) salt.

  1. Controllable stereoselective synthesis of trisubstituted alkenes by a catalytic three-component reaction of terminal alkynes, benzylic alcohols, and simple arenes.

    PubMed

    Li, Hai-Hua; Jin, Yin-Huan; Wang, Jie-Qi; Tian, Shi-Kai

    2009-08-21

    The acid-catalyzed three-component reaction of terminal alkynes, benzylic alcohols, and simple arenes provides convenient and atom-economic access to an array of both Z- and E-isomers of trisubstituted alkenes with excellent stereoselectivity by switching reaction temperature and acidic catalysts.

  2. Metathesis of fatty acid ester derivatives in 1,1-dialkyl and 1,2,3-trialkyl imidazolium type ionic liquids.

    PubMed

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

    2011-01-01

    The self-metathesis of methyl oleate and methyl ricinoleate was carried out in the presence of ruthenium alkylidene catalysts 1-4 in [bmim] and [bdmim][X] type ionic liquids (RTILs) (X = PF(6) (-), BF(4) (-) and NTf(2) (-)) using the gas chromatographic technique. Best catalytic performance was obtained in [bdmim][X] type ionic liquids when compared with [bmim][X] type ionic liquids. Catalyst recycling studies were also carried out in the room temperature ionic liquids (RTILs) with catalysts 1-4 in order to explore their possible industrial application.

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

    PubMed Central

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

    2011-01-01

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

  4. Stereoselective synthesis of macrocyclic peptides via a dual olefin metathesis and ethenolysis approach.

    PubMed

    Mangold, Shane L; Grubbs, Robert H

    2015-08-01

    Macrocyclic compounds occupy an important chemical space between small molecules and biologics and are prevalent in many natural products and pharmaceuticals. The growing interest in macrocycles has been fueled, in part, by the design of novel synthetic methods to these compounds. One appealing strategy is ring-closing metathesis (RCM) that seeks to construct macrocycles from acyclic diene precursors using defined transition-metal alkylidene catalysts. Despite its broad utility, RCM generally gives rise to a mixture of E- and Z-olefin isomers that can hinder efforts for the large-scale production and isolation of such complex molecules. To address this issue, we aimed to develop methods that can selectively enrich macrocycles in E- or Z-olefin isomers using an RCM/ethenolysis strategy. The utility of this methodology was demonstrated in the stereoselective formation of macrocyclic peptides, a class of compounds that have gained prominence as therapeutics in drug discovery. Herein, we report an assessment of various factors that promote catalyst-directed RCM and ethenolysis on a variety of peptide substrates by varying the olefin type, peptide sequence, and placement of the olefin in macrocycle formation. These methods allow for control over olefin geometry in peptides, facilitating their isolation and characterization. The studies outlined in this report seek to expand the scope of stereoselective olefin metathesis in general RCM.

  5. Remarkably Efficient Microvawe-Assisted Cross-Metathesis of Lipids in Solvent Free Conditions.

    PubMed

    Ullah, Aman; Arshad, Muhammad

    2017-02-28

    Catalytic transformation of renewable feed stocks into fine chemicals is in high demands and olefin metathesis is one of the sophisticated tools for biomass conversion. Nevertheless, the large scale viability of such processes depends on the conversion efficiency, energy efficiency, catalytic activity, selective conversion into desired products and environmental footprint of the process. Thus, conversions of renewables using simple, swift, and efficient methods are desirable. A microwave-assisted ethenolysis and alkenolysis (using 1-5 hexadiene) of canola oil and methyl esters derived from canola oil (COME) and waste/recycled cooking oil (WOME) was carried out using ruthenium based catalytic systems. A systematic study using 1st and 2nd generation Grubbs (G1, G2) and Hoveyda-Grubbs (HG1 & HG2) catalysts was carried out. Among all ruthenium catalysts, HG2 was found to be highly active in the range of 0.002-0.1 mol% loadings. The conversions proved to be highly efficient with outstanding values of turnover numbers (TONs) and turnover frequencies (TOFs). The TONs for ethenolysis of COME (~1.5 million), direct ethenolysis of canola oil (~0.6 million), more than 1 million for WOME and above 1.6 million for cross metathesis of 1,5-hexadiene with COME were achieved. The ethenolysis of commercial methyl oleate was also performed leading to TONs ~1.2 million and TOFs 20,300 s-1 under microwave conditions.

  6. Stereoselective synthesis of macrocyclic peptides via a dual olefin metathesis and ethenolysis approach

    PubMed Central

    Mangold, Shane L.

    2015-01-01

    Macrocyclic compounds occupy an important chemical space between small molecules and biologics and are prevalent in many natural products and pharmaceuticals. The growing interest in macrocycles has been fueled, in part, by the design of novel synthetic methods to these compounds. One appealing strategy is ring-closing metathesis (RCM) that seeks to construct macrocycles from acyclic diene precursors using defined transition-metal alkylidene catalysts. Despite its broad utility, RCM generally gives rise to a mixture of E- and Z-olefin isomers that can hinder efforts for the large-scale production and isolation of such complex molecules. To address this issue, we aimed to develop methods that can selectively enrich macrocycles in E- or Z-olefin isomers using an RCM/ethenolysis strategy. The utility of this methodology was demonstrated in the stereoselective formation of macrocyclic peptides, a class of compounds that have gained prominence as therapeutics in drug discovery. Herein, we report an assessment of various factors that promote catalyst-directed RCM and ethenolysis on a variety of peptide substrates by varying the olefin type, peptide sequence, and placement of the olefin in macrocycle formation. These methods allow for control over olefin geometry in peptides, facilitating their isolation and characterization. The studies outlined in this report seek to expand the scope of stereoselective olefin metathesis in general RCM. PMID:26509000

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

    PubMed

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

    2015-12-18

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

  8. Organic chemistry: No double bond left behind

    NASA Astrophysics Data System (ADS)

    Sarlah, David

    2016-03-01

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

  9. Methods for direct alkene diamination, new & old

    PubMed Central

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

    2012-01-01

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

  10. Heterocycle synthesis by copper facilitated addition of heteroatoms to alkenes, alkynes and arenes.

    PubMed

    Chemler, Sherry R; Fuller, Peter H

    2007-07-01

    The de novo synthesis of small organic heterocyclic molecules has benefited from recent protocols for copper-facilitated additions of heteroatoms to alkenes, alkynes and arenes. This tutorial review summarizes a number of these recent contributions. Copper salts can facilitate bond formations due to their ability to serve as Lewis acids, oxidizing agents and transition metal catalysts. The current understanding of the mechanisms of these reactions is presented. This review should be of interest to chemists involved in the synthesis of heterocycles and those investigating transition metal facilitated reactions.

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

    PubMed

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

    2016-07-06

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

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

    PubMed

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

    2014-01-16

    Terminal, monosubstituted alkenes are ideal prospective starting materials for organic synthesis because they are manufactured on very large scales and can be functionalized via a broad range of chemical transformations. Alkenes also have the attractive feature of being stable in the presence of many acids, bases, oxidants and reductants. In spite of these attributes, relatively few catalytic enantioselective transformations have been developed that transform aliphatic α-olefins into chiral products with an enantiomeric excess greater then 90 per cent. With the exception of site-controlled isotactic polymerization of α-olefins, none of these catalytic enantioselective processes results in chain-extending carbon-carbon bond formation to the terminal carbon. Here we describe a strategy that directly addresses this gap in synthetic methodology, and present a single-flask, catalytic enantioselective conversion of terminal alkenes into a number of chiral products. These reactions are facilitated by a neighbouring functional group that accelerates palladium-catalysed cross-coupling of 1,2-bis(boronates) relative to non-functionalized alkyl boronate analogues. In tandem with enantioselective diboration, this reactivity feature transforms alkene starting materials into a diverse array of chiral products. We note that the tandem diboration/cross-coupling reaction generally provides products in high yield and high selectivity (>95:5 enantiomer ratio), uses low loadings (1-2 mol per cent) of commercially available catalysts and reagents, offers an expansive substrate scope, and can address a broad range of alcohol and amine synthesis targets, many of which cannot be easily addressed with current technology.

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    Terminal, monosubstituted alkenes are ideal prospective starting materials for organic synthesis because they are manufactured on very large scales and can be functionalized via a broad range of chemical transformations. Alkenes also have the attractive feature of being stable in the presence of many acids, bases, oxidants and reductants. In spite of these attributes, relatively few catalytic enantioselective transformations have been developed that transform aliphatic α-olefins into chiral products with an enantiomeric excess greater then 90 per cent. With the exception of site-controlled isotactic polymerization of α-olefins, none of these catalytic enantioselective processes results in chain-extending carbon-carbon bond formation to the terminal carbon. Here we describe a strategy that directly addresses this gap in synthetic methodology, and present a single-flask, catalytic enantioselective conversion of terminal alkenes into a number of chiral products. These reactions are facilitated by a neighbouring functional group that accelerates palladium-catalysed cross-coupling of 1,2-bis(boronates) relative to non-functionalized alkyl boronate analogues. In tandem with enantioselective diboration, this reactivity feature transforms alkene starting materials into a diverse array of chiral products. We note that the tandem diboration/cross-coupling reaction generally provides products in high yield and high selectivity (>95:5 enantiomer ratio), uses low loadings (1-2 mol per cent) of commercially available catalysts and reagents, offers an expansive substrate scope, and can address a broad range of alcohol and amine synthesis targets, many of which cannot be easily addressed with current technology.

  14. Kinetics of the polymerization of alkenes on zeolites

    NASA Astrophysics Data System (ADS)

    Alberty, Robert A.

    1987-09-01

    The polymerization of alkenes at temperatures in the neighborhood of 600 K on a zeolite catalyst can be described in terms of a mechanism with bimolecular polymerization reactions and cracking reactions of isomer groups. The rate equations for the formation of isomer groups up to C13H26 have been integrated using the fourth-order Runge-Kutta method for polymerizations at constant temperature and pressure. In the absence of data on rate constants, calculations have been made on the basis of the assumption that all the bimolecular rate constants are equal or all the cracking constants are equal. In each case the rate constants for the reverse reactions have been calculated using the equilibrium constants for the steps in the mechanism. Under some circumstances the plots of weight fractions of isomer groups vs time have nearly the same shape for the two assumptions. However, it is possible to distinguish between the two assumptions by using experiments at sufficiently high pressures. The calculations show that it is of interest to examine the compositions arising from different starting materials, even though the equilibrium composition depends only upon temperature and pressure.

  15. Magnetic and dendritic catalysts.

    PubMed

    Wang, Dong; Deraedt, Christophe; Ruiz, Jaime; Astruc, Didier

    2015-07-21

    The recovery and reuse of catalysts is a major challenge in the development of sustainable chemical processes. Two methods at the frontier between homogeneous and heterogeneous catalysis have recently emerged for addressing this problem: loading the catalyst onto a dendrimer or onto a magnetic nanoparticle. In this Account, we describe representative examples of these two methods, primarily from our research group, and compare them. We then describe new chemistry that combines the benefits of these two methods of catalysis. Classic dendritic catalysis has involved either attaching the catalyst covalently at the branch termini or within the dendrimer core. We have used chelating pyridyltriazole ligands to insolubilize catalysts at the termini of dendrimers, providing an efficient, recyclable heterogeneous catalysts. With the addition of dendritic unimolecular micelles olefin metathesis reactions catalyzed by commercial Grubbs-type ruthenium-benzylidene complexes in water required unusually low amounts of catalyst. When such dendritic micelles include intradendritic ligands, both the micellar effect and ligand acceleration promote faster catalysis in water. With these types of catalysts, we could carry out azide alkyne cycloaddition ("click") chemistry with only ppm amounts of CuSO4·5H2O and sodium ascorbate under ambient conditions. Alternatively we can attach catalysts to the surface of superparamagnetic iron oxide nanoparticles (SPIONs), essentially magnetite (Fe3O4) or maghemite (γ-Fe2O3), offering the opportunity to recover the catalysts using magnets. Taking advantage of the merits of both of these strategies, we and others have developed a new generation of recyclable catalysts: dendritic magnetically recoverable catalysts. In particular, some of our catalysts with a γ-Fe2O3@SiO2 core and 1,2,3-triazole tethers and loaded with Pd nanoparticles generate strong positive dendritic effects with respect to ligand loading, catalyst loading, catalytic activity and

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

    DOEpatents

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

    2012-11-27

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

  17. Mechanistic insight into the photoredox catalysis of anti-Markovnikov alkene hydrofunctionalization reactions

    DOE PAGES

    Romero, Nathan A.; Nicewicz, David A.

    2014-11-12

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

  18. Mechanistic insight into the photoredox catalysis of anti-Markovnikov alkene hydrofunctionalization reactions

    SciTech Connect

    Romero, Nathan A.; Nicewicz, David A.

    2014-11-12

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

  19. Rhodium-catalyzed formation of stereocontrolled trisubstituted alkenes from Baylis-Hillman adducts.

    PubMed

    Gendrineau, Thomas; Demoulin, Nicolas; Navarre, Laure; Genet, Jean-Pierre; Darses, Sylvain

    2009-01-01

    Efficient and general conditions for the formation of stereodefined trisubstituted alkenes by using the rhodium-catalyzed reaction of unactivated Baylis-Hillman adducts with either organoboronic acids or potassium trifluoro(organo)borates are reported (see scheme).We report here efficient and general conditions for the formation of stereodefined trisubstituted alkenes using the rhodium-catalyzed reaction of unactivated Baylis-Hillman adducts with either organoboronic acids and potassium trifluoro(organo)borates. The use of the [{Rh(cod)OH}(2)] precursor gave very fast coupling reactions under low catalyst loading, very mild reaction conditions (from room temperature up to 50 degrees C) and without the need of additional phosphane ligands. Based on the new reaction conditions, the reaction, originally limited to Baylis-Hillman adducts derived from esters, could be extended to a large variety of Baylis-Hillman adducts, bearing either keto, cyano or amido functionalities. Moreover, the reaction of Baylis-Hillman adducts bearing esters functionality was improved and could be conducted at lower temperature using lower catalyst loading.

  20. Elucidation of the resting state of a rhodium NNN-pincer hydrogenation catalyst that features a remarkably upfield hydride (1)H NMR chemical shift.

    PubMed

    Hänninen, Mikko M; Zamora, Matthew T; MacNeil, Connor S; Knott, Jackson P; Hayes, Paul G

    2016-01-11

    Rhodium(I) alkene complexes of an NNN-pincer ligand catalyze the hydrogenation of alkenes, including ethylene. The terminal or resting state of the catalyst, which exhibits an unprecedentedly upfield Rh-hydride (1)H NMR chemical shift, has been isolated and a synthetic cycle for regenerating the catalytically active species has been established.

  1. Sequential aza-Baylis-Hillman/ring closing metathesis/aromatization as a novel route for the synthesis of substituted pyrroles.

    PubMed

    Declerck, Valérie; Ribière, Patrice; Martinez, Jean; Lamaty, Frédéric

    2004-11-26

    A new route to diverse 2-substituted-3-methoxycarbonyl pyrroles has been developed. Diverse SES protected alpha-methylene beta-aminoesters were obtained by a 3-component aza-Baylis-Hillman reaction. Diversity arose from the aryl aldehydes which can be used in this reaction. N-Alkylation with allyl bromide under mild conditions provided the corresponding dienes. These substituted dienes were cyclized by ring closing metathesis at room temperature or under microwave-activation with Grubbs-type II catalyst to yield SES-protected pyrroline intermediates. The final pyrroles were obtained by base-promoted dehydrodesulfinylation/aromatization. The scope of each of these reactions was explored.

  2. One-pot cross-enyne metathesis (CEYM)-Diels-Alder reaction of gem-difluoropropargylic alkynes.

    PubMed

    Fustero, Santos; Bello, Paula; Miró, Javier; Sánchez-Roselló, María; Haufe, Günter; Del Pozo, Carlos

    2013-01-01

    Propargylic difluorides 1 were used as starting substrates in a combination of cross-enyne metathesis and Diels-Alder reactions. Thus, the reaction of 1 with ethylene in the presence of 2(nd) generation Hoveyda-Grubbs catalyst generates a diene moiety which in situ reacts with a wide variety of dienophiles giving rise to a small family of new fluorinated carbo- and heterocyclic derivatives in moderate to good yields. This is a complementary protocol to the one previously described by our research group, which involved the use of 1,7-octadiene as an internal source of ethylene.

  3. Engineering the metathesis and oxidation-reduction reaction in solid state at room temperature for nanosynthesis

    PubMed Central

    Hu, Pengfei; Cao, Yali; Jia, Dianzeng; Li, Qiang; Liu, Ruili

    2014-01-01

    It is a long-standing goal to explore convenient synthesis methodology for functional materials. Recently, several multiple-step approaches have been designed for photocatalysts AgnX@Ag (X = Cl−, PO43−, etc.), mainly containing the ion-exchange (metathesis) reaction followed by photoreduction in solution. But they were obsessed by complicated process, the uncontrollability of composition and larger sizes of Ag particles. Here we show a general solid-state route for the synthesis of AgnX@Ag catalysts with hierarchical structures. Due to strong surface plasmon resonance of silver nanoparticles with broad shape and size, the AgnX@Ag showed high photocatalytic activity in visible region. Especially, the composition of AgnX@Ag composites could be accurately controlled by regulating the feed ratio of (NH2OH)2·H2SO4 to anions, by which the performance were easily optimized. Results demonstrate that the metathesis and oxidation-reduction reactions can be performed in solid state at room temperature for nanosynthesis, greatly reducing the time/energy consumption and pollution. PMID:24614918

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

    PubMed Central

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  6. An investigation of wall effects in microwave-assisted ring-closing metathesis and cyclotrimerization reactions.

    PubMed

    Dallinger, Doris; Irfan, Muhammed; Suljanovic, Amra; Kappe, C Oliver

    2010-08-06

    Challenging Ru-catalyzed ring-closing metathesis transformations leading to eight-membered-ring systems and Ni- or Co-catalyzed [2+2+2] cyclotrimerizations were evaluated at elevated temperatures applying microwave dielectric heating or conventional thermal heating in order to investigate the role of wall effects. All reactions were conducted in a dedicated reactor setup that allowed accurate internal reaction temperature measurements using fiber-optic probes for both types of heating modes. For ring-closing metathesis best results were achieved using an open vessel-gas sparging protocol in 1,2-dichloroethane at reflux temperature (83 degrees C), while cyclotrimerizations were performed under sealed vessel conditions in toluene between 80 and 160 degrees C. For all studied transformations the results achieved in a single-mode microwave reactor could be reproduced by conventional heating in an oil bath by carefully matching the temperature profiles as close as possible during the entire heating and cooling cycle. In contrast to previous literature reports, no evidence that direct in-core microwave heating can increase catalyst lifetime by minimization or elimination of wall effects was obtained. At the same time, no indication for the involvement of nonthermal microwave effects in these homogeneous transition metal-catalyzed transformations was seen.

  7. Pt nanoparticles immobilized in mesostructured silica: a non-leaching catalyst for 1-octene hydrosilylation.

    PubMed

    Galeandro-Diamant, Thomas; Sayah, Reine; Zanota, Marie-Line; Marrot, Sébastien; Veyre, Laurent; Thieuleux, Chloé; Meille, Valérie

    2017-02-23

    A catalyst containing small (ca. 2.5 nm) and crystalline Pt nanoparticles embedded into the walls of a mesostructured silica framework was found to be highly active in alkene hydrosilylation reaching TONs of ca. 10(5). More importantly, no Pt leaching was detected. This result is remarkable because Pt leaching is a recurrent problem in alkene hydrosilylation, which often prevents heterogeneous catalysts from being used industrially. This result is in contrast to the significant Pt leaching observed for other Pt/SiO2 catalysts.

  8. A Procedure Identifying a Polyacetylene Initiator of Olefin Metathesis. The Reactivities of Metal-Carbenes Toward Alkenes and Alkynes.

    DTIC Science & Technology

    2014-09-26

    Reproduction in whole or in part is permitted for any purpose of the United States Government This document has been approved for public release and...979, 17, 421. (c) Percec, V.; Rinaldi, P. L. Polym. Bull . (Berlin) 1983, 9, 548; (d) Percec, V. ibid. 1983, 10, 1. (24) Masuda, T.; Takahashi, T...Yamamoto, K.; Higashimura, T. J. Polym. Sci.. Polym. Chem. Ed. 1982, 20, 2603. (25) Percec, V.; Rinaldi, P. L., Polym. Bull . (Berlin) 1983, 9, 582. (26

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

    PubMed

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

    2016-10-01

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

  10. Synthesis of ω-Oxo Amino Acids and trans-5-Substituted Proline Derivatives Using Cross-Metathesis of Unsaturated Amino Acids.

    PubMed

    Salih, Nabaz; Adams, Harry; Jackson, Richard F W

    2016-09-16

    A range of 7-oxo, 8-oxo, and 9-oxo amino acids, analogues of 8-oxo-2-aminodecanoic acid, one of the key components of the cyclic tetrapeptide apicidin, have been prepared by a three-step process involving copper-catalyzed allylation of serine-, aspartic acid-, and glutamic acid-derived organozinc reagents, followed by cross-metathesis of the resulting terminal alkenes with unsaturated ketones and hydrogenation. The intermediate 7-oxo-5-enones underwent a highly diastereoselective (dr ≥96:4) acid-catalyzed aza-Michael reaction to give trans-2,5-disubstituted pyrrolidines, 5-substituted proline derivatives. The aza-Michael reaction was first observed when the starting enones were allowed to stand in solution in deuterochloroform but can be efficiently promoted by catalytic amounts of dry HCl.

  11. Enantioselective copper-catalyzed carboetherification of unactivated alkenes.

    PubMed

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

    2014-06-16

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

  12. Nickel-Catalyzed Allylic Substitution of Simple Alkenes

    PubMed Central

    Matsubara, Ryosuke; Jamison, Timothy F.

    2011-01-01

    This report describes a nickel-catalyzed allylic substitution process of simple alkenes whereby an important structural motif, a 1,4-diene, was prepared. A key for this success is the use of an appropriate Ni-phosphine complex and a stoichiometric amount of silyl triflate. Reactions of 1-alkyl-substituted alkenes consistently provided 1,1-disubstituted alkenes with high selectivity. Insight into the reaction mechanism as well as miscellaneous application of the developed catalytic process is also documented. PMID:21387565

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

    SciTech Connect

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

    2008-01-01

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

  14. Acyclic diene metathesis with a monomer from renewable resources: control of molecular weight and one-step preparation of block copolymers.

    PubMed

    Rybak, Anastasiya; Meier, Michael A R

    2008-01-01

    The preparation of a long-chain aliphatic alpha,omega-diene from plant oil derivatives and its subsequent polymerization through acyclic diene metathesis (ADMET) is described. The ADMET bulk polymerization of the thus-obtained monomer, undecyl undecenoate, was investigated and optimized by applying ruthenium-based metathesis catalysts from Grubbs and Hoveyda-Grubbs, leading to high-molecular-weight polyesters. Moreover, by applying different amounts of methyl 10-undecenoate as a chain stopper in this ADMET step growth polymerization, the molecular weight of the resulting polyester could be tuned in a range from approximately 10 to 45 kDa. Finally, the application of a poly(ethylene glycol) methyl ether acrylate as the chain stopper led to the preparation of ABA triblock copolymers in a one-step, one-pot procedure.

  15. Rhodium-Catalyzed Dehydrogenative Borylation of Cyclic Alkenes

    PubMed Central

    Kondoh, Azusa; Jamison, Timothy F.

    2010-01-01

    A rhodium-catalyzed dehydrogenative borylation of cyclic alkenes is described. This reaction provides direct access to cyclic 1-alkenylboronic acid pinacol esters, useful intermediates in organic synthesis. Suzuki-Miyaura cross-coupling applications are also presented. PMID:20107646

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

    ERIC Educational Resources Information Center

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

    2005-01-01

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

  17. Enantio- and Regioselective CuH-Catalyzed Hydroamination of Alkenes

    PubMed Central

    Zhu, Shaolin; Niljianskul, Nootaree; Buchwald, Stephen L.

    2013-01-01

    A highly enantio- and regioselective copper-catalyzed hydroamination reaction of alkenes has been developed using diethoxy(methyl)silane (DEMS) and esters of hydroxylamines. The process tolerates a wide variety of substituted styrenes, including trans-, cis-, and β,β-disubstituted styrenes to yield α–branched amines. In addition, aliphatic alkenes coupled to generate exclusively the anti-Markovnikov hydroamination products. PMID:24106781

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

    PubMed

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

    2012-12-21

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

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

    NASA Astrophysics Data System (ADS)

    Mauldin, Timothy C.

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

  20. The "catalytic nitrosyl effect": NO bending boosting the efficiency of rhenium based alkene hydrogenations.

    PubMed

    Jiang, Yanfeng; Schirmer, Birgitta; Blacque, Olivier; Fox, Thomas; Grimme, Stefan; Berke, Heinz

    2013-03-13

    Diiodo Re(I) complexes [ReI2(NO)(PR3)2(L)] (3, L = H2O; 4 , L = H2; R = iPr a, Cy b) were prepared and found to exhibit in the presence of "hydrosilane/B(C6F5)3" co-catalytic systems excellent activities and longevities in the hydrogenation of terminal and internal alkenes. Comprehensive mechanistic studies showed an inverse kinetic isotope effect, fast H2/D2 scrambling and slow alkene isomerizations pointing to an Osborn type hydrogenation cycle with rate determining reductive elimination of the alkane. In the catalysts' activation stage phosphonium borates [R3PH][HB(C6F5)3] (6, R = iPr a, Cy b) are formed. VT (29)Si- and (15)N NMR experiments, and dispersion corrected DFT calculations verified the following facts: (1) Coordination of the silylium cation to the ONO atom facilitates nitrosyl bending; (2) The bent nitrosyl promotes the heterolytic cleavage of the H-H bond and protonation of a phosphine ligand; (3) H2 adds in a bifunctional manner across the Re-N bond. Nitrosyl bending and phosphine loss help to create two vacant sites, thus triggering the high hydrogenation activities of the formed "superelectrophilic" rhenium centers.

  1. An Umpolung Approach to Alkene Carboamination: Palladium Catalyzed 1,2-Amino-Acylation, -Carboxylation, -Arylation, -Vinylation, and -Alkynylation.

    PubMed

    Faulkner, Adele; Scott, James S; Bower, John F

    2015-06-10

    Conventional approaches to Pd-catalyzed alkene 1,2-carboamination rely upon the combination of a nucleophilic nitrogen-based component and an internal C-based or external oxidant. In this study, we outline an umpolung approach, which is triggered by oxidative initiation at an electrophilic N-based component and employs "standard" organometallic nucleophiles to introduce the new carbon-based fragment. Specifically, oxidative addition of a Pd(0)-catalyst into the N-O bond of O-pentafluorobenzoyl oxime esters generates imino-Pd(II) intermediates, which undergo 5-exo cyclization with sterically diverse alkenes. The resultant alkyl-Pd(II) intermediates are intercepted by organometallic nucleophiles or alcohols, under carbonylative or noncarbonylative conditions, to provide 1,2-carboamination products. This approach provides, for the first time, a unified strategy for achieving alkene 1,2-amino-acylation, -carboxylation, -arylation, -vinylation, and -alkynylation. For carbonylative processes, orchestrated protodecarboxylation of the pentafluorobenzoate leaving group underpins reaction efficiency. This process is likely a key feature in related Narasaka-Heck cyclizations and accounts for the efficacy of O-pentafluorobenzoyl oxime esters in aza-Heck reactions of this type.

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

    PubMed

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

    2015-06-24

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

  3. Ruthenium-catalyzed oxidation of alkenes, alkynes, and alcohols to organic acids with aqueous hydrogen peroxide.

    PubMed

    Che, Chi-Ming; Yip, Wing-Ping; Yu, Wing-Yiu

    2006-09-18

    A protocol that adopts aqueous hydrogen peroxide as a terminal oxidant and [(Me3tacn)(CF3CO2)2Ru(III)(OH2)]CF3CO2 (1; Me3tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane) as a catalyst for oxidation of alkenes, alkynes, and alcohols to organic acids in over 80% yield is presented. For the oxidation of cyclohexene to adipic acid, the loading of 1 can be lowered to 0.1 mol %. On the one-mole scale, the oxidation of cyclohexene, cyclooctene, and 1-octanol with 1 mol % of 1 produced adipic acid (124 g, 85% yield), suberic acid (158 g, 91% yield), and 1-octanoic acid (129 g, 90% yield), respectively. The oxidative C=C bond-cleavage reaction proceeded through the formation of cis- and trans-diol intermediates, which were further oxidized to carboxylic acids via C-C bond cleavage.

  4. Gold(I)-Catalyzed Intramolecular Hydroamination of Unactivated Terminal and Internal Alkenes with 2-Pyridones.

    PubMed

    Timmerman, Jacob C; Laulhé, Sébastien; Widenhoefer, Ross A

    2017-03-17

    The cationic gold phosphine complex [(P1)Au(NCMe)](+)SbF6(-) [P1 = P(t-Bu)2o-biphenyl; 2] catalyzes the intramolecular hydroamination of 6-alkenyl-2-pyridones to form 1,6-carboannulated 2-pyridones in high yield. The hydroamination of 6-(γ-alkenyl)-2-pyridones was effective for monosubstituted and 1,1- and 1,2-disubstituted aliphatic alkenes, and the method was likewise effective for the hydroamination of 6-(δ-alkenyl)-2-pyridones. Spectroscopic analysis of mixtures of 6-(3-butenyl)-2-pyridone, (P1)AuCl, and AgSbF6 established the N-bound 2-hydroxypyridine complex [(P1)Au(NC6H3-2-OH-6-CH2CH2CH═CH2)](+) SbF6(-) as the catalyst resting state.

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

    PubMed Central

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

    2015-01-01

    Hydrotrifluoromethylation, vinylic trifluoromethylation, and iodotrifluoromethylation of simple alkenes have been achieved by using Togni reagent in the absence of any transition metal catalyst. These reactions were readily controllable by selection of appropriate salts and solvents. The addition of K2CO3 afforded the hydrotrifluoromethylation product, with DMF acting not only as a solvent, but also as the hydrogen source. In contrast, the use of tetra-n-butylammonium iodide (TBAI) in 1,4-dioxane resulted in vinylic trifluoromethylation, while the use of KI afforded the iodotrifluoromethylation product. The vinylic trifluoromethylation product was obtained by treatment of the iodotrifluoromethylation product with ammonium 2-iodobenzoate, indicating that it was formed through an elimination reaction of the in-situ-generated iodotrifluoromethylation product, and the solubility of the resulting 2-iodobenzoate salt plays a key role in the product switching. A radical-clock experiment showed that these reactions proceed via radical intermediates. PMID:25960034

  6. Rhodium-phosphoramidite catalyzed alkene hydroacylation: mechanism and octaketide natural product synthesis.

    PubMed

    von Delius, Max; Le, Christine M; Dong, Vy M

    2012-09-12

    We describe a method that allows salicylaldehyde derivatives to be coupled with a wide range of unactivated alkenes at catalyst loadings as low as 2 mol %. A chiral phosphoramidite ligand and the precise stoichiometry of heterogeneous base are key for high catalytic activity and linear regioselectivity. This protocol was applied in the atom- and step-economical synthesis of eight biologically active octaketide natural products, including anticancer drug candidate cytosporone B. Mechanistic studies provide insight on parameters affecting decarbonylation, a side reaction that limits the turnover number for catalytic hydroacylation. Deuterium labeling studies show that branched hydride insertion is fully reversible, whereas linear hydride insertion is largely irreversible and turnover-limiting. We propose that ligand (R(a),R,R)-SIPHOS-PE effectively suppresses decarbonylation, and helps favor a turnover-limiting insertion, by lowering the barrier for reductive elimination in the linear-selective pathway. Together, these factors enable high reactivity and regioselectivity.

  7. Heteroatom-free arene-cobalt and arene-iron catalysts for hydrogenations.

    PubMed

    Gärtner, Dominik; Welther, Alice; Rad, Babak Rezaei; Wolf, Robert; Jacobi von Wangelin, Axel

    2014-04-01

    75 years after the discovery of hydroformylation, cobalt catalysts are now undergoing a renaissance in hydrogenation reactions. We have evaluated arene metalates in which the low-valent metal species is--conceptually different from heteroatom-based ligands--stabilized by π coordination to hydrocarbons. Potassium bis(anthracene)cobaltate 1 and -ferrate 2 can be viewed as synthetic precursors of quasi-"naked" anionic metal species; their aggregation is effectively impeded by (labile) coordination to the various π acceptors present in the hydrogenation reactions of unsaturated molecules (alkenes, arenes, carbonyl compounds). Kinetic studies, NMR spectroscopy, and poisoning studies of alkene hydrogenations support the formation of a homogeneous catalyst derived from 1 which is stabilized by the coordination of alkenes. This catalyst concept complements the use of complexes with heteroatom donor ligands for reductive processes.

  8. Enantioselective Pd(II)-catalyzed aerobic oxidative amidation of alkenes and insights into the role of electronic asymmetry in pyridine-oxazoline ligands.

    PubMed

    McDonald, Richard I; White, Paul B; Weinstein, Adam B; Tam, Chun Pong; Stahl, Shannon S

    2011-06-03

    Enantioselective intramolecular oxidative amidation of alkenes has been achieved using a (pyrox)Pd(II)(TFA)(2) catalyst (pyrox = pyridine-oxazoline, TFA = trifluoroacetate) and O(2) as the sole stoichiometric oxidant. The reactions proceed at room temperature in good-to-excellent yields (58-98%) and with high enantioselectivity (ee = 92-98%). Catalyst-controlled stereoselective cyclization reactions are demonstrated for a number of chiral substrates. DFT calculations suggest that the electronic asymmetry of the pyrox ligand synergizes with steric asymmetry to control the stereochemical outcome of the key amidopalladation step.

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2012-11-21

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

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

    PubMed

    Sugimoto, Hideki; Ashikari, Kenji; Itoh, Shinobu

    2013-09-01

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

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

    PubMed

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

    2016-06-01

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

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

    PubMed

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

    2015-09-01

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

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

    PubMed Central

    2015-01-01

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

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

    PubMed

    Yao, Qingwei

    2002-02-07

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

  16. Conversion of allylic alcohols to stereodefined trisubstituted alkenes: a complementary process to the Claisen rearrangement.

    PubMed

    Belardi, Justin K; Micalizio, Glenn C

    2008-12-17

    A stereoselective method for the conversion of allylic alcohols to (Z)-trisubstituted alkenes is presented. Overall, the reaction sequence described is stereochemically complementary to related Claisen rearrangement reactions--processes that typically deliver the stereoisomeric trisubstituted alkene containing products.

  17. Induction of Olefin Metathesis by Acetylenes.

    DTIC Science & Technology

    1980-11-20

    essentially that of 2. The acetylene is thus an activator, but unlike the organometallic co- catalysts like C2 H5A1C1 2 , which it replaces, it is unique in...J.C.; Moulijn, J.A. Adv. Catal. 1975, 24, 131. (4) Some of the results were discussed at the 3rd NSF Workshop on Organo - metallic Chemistry, Pingree

  18. Asymmetric epoxidation of unfunctionalized alkenes catalyzed by sugar moiety-modified chiral salen-Mn(III) complexes.

    PubMed

    Zhao, Jiquan; Zhang, Yuecheng; Han, Furong; Zhao, Shanshan

    2009-01-05

    Several chiral Schiff-base ligands with sugar moieties at C-3 (3') or C-5 (5') of salicylaldehyde were synthesized from reaction of salicylaldehyde derivatives with diamine. These ligands coordinated with Mn(III) to afford the corresponding chiral salen-Mn(III) complexes characterized by FT-IR, MS, and elementary analysis. These complexes were used as catalysts for the asymmetric epoxidation of unfunctionalized alkenes. Only weak enantioselectivity is induced by the chiral sugar moieties at C-3 (3') or C-5 (5') in the case of absence of chirality in the diimine bridge moiety. It was also shown that the sugars at C-5 (5') having the same rotation direction of polarized light as the diimine bridge in the catalyst could enhance the chiral induction in the asymmetric epoxidation, but the sugars with the opposite rotation direction would reduce the chiral induction.

  19. Bis(imino)pyridine cobalt-catalyzed alkene isomerization-hydroboration: a strategy for remote hydrofunctionalization with terminal selectivity.

    PubMed

    Obligacion, Jennifer V; Chirik, Paul J

    2013-12-26

    Bis(imino)pyridine cobalt methyl complexes are active for the catalytic hydroboration of terminal, geminal, disubstituted internal, tri- and tetrasubstituted alkenes using pinacolborane (HBPin). The most active cobalt catalyst was obtained by introducing a pyrrolidinyl substituent into the 4-position of the bis(imino)pyridine chelate, enabling the facile hydroboration of sterically hindered substrates such as 1-methylcyclohexene, α-pinene, and 2,3-dimethyl-2-butene. Notably, these hydroboration reactions proceed with high activity and anti-Markovnikov selectivity in neat substrates at 23 °C. With internal olefins, the cobalt catalyst places the boron substituent exclusively at the terminal positions of an alkyl chain, providing a convenient method for hydrofunctionalization of remote C-H bonds.

  20. Domino rhodium/palladium-catalyzed dehydrogenation reactions of alcohols to acids by hydrogen transfer to inactivated alkenes.

    PubMed

    Trincado, Mónica; Grützmacher, Hansjörg; Vizza, Francesco; Bianchini, Claudio

    2010-03-01

    The combination of the d(8) Rh(I) diolefin amide [Rh(trop(2)N)(PPh(3))] (trop(2)N=bis(5-H-dibenzo[a,d]cyclohepten-5-yl)amide) and a palladium heterogeneous catalyst results in the formation of a superior catalyst system for the dehydrogenative coupling of alcohols. The overall process represents a mild and direct method for the synthesis of aromatic and heteroaromatic carboxylic acids for which inactivated olefins can be used as hydrogen acceptors. Allyl alcohols are also applicable to this coupling reaction and provide the corresponding saturated aliphatic carboxylic acids. This transformation has been found to be very efficient in the presence of silica-supported palladium nanoparticles. The dehydrogenation of benzyl alcohol by the rhodium amide, [Rh]N, follows the well established mechanism of metal-ligand bifunctional catalysis. The resulting amino hydride complex, [RhH]NH, transfers a H(2) molecule to the Pd nanoparticles, which, in turn, deliver hydrogen to the inactivated alkene. Thus a domino catalytic reaction is developed which promotes the reaction R-CH(2)-OH+NaOH+2 alkene-->R-COONa+2 alkane.

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

    SciTech Connect

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

    2008-05-27

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

  2. Biogenic Emissions of Light Alkenes from a Coniferous Forest

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    PubMed

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

    2014-09-01

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

  4. Oxidation catalyst

    DOEpatents

    Ceyer, Sylvia T.; Lahr, David L.

    2010-11-09

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

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

    PubMed

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

    2006-06-09

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

  6. Unidirectional light-driven molecular motors based on overcrowded alkenes.

    PubMed

    Cnossen, Arjen; Browne, Wesley R; Feringa, Ben L

    2014-01-01

    Over the last two decades, interest in nanotechnology has led to the design and synthesis of a toolbox of nanoscale versions of macroscopic devices and components. In molecular nanotechnology, linear motors based on rotaxanes and rotary motors based on overcrowded alkenes are particularly promising for performing work at the nanoscale. In this chapter, progress on light-driven molecular motors based on overcrowded alkenes is reviewed. Both the so-called first and second generation molecular motors are discussed, as well as their potential applications.

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

    PubMed

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

    2016-05-06

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

  8. Isomerization of C[sub 4] alkenes

    DOEpatents

    Smith, L.A. Jr.

    1984-11-13

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

  9. Isomerization of C.sub.4 alkenes

    DOEpatents

    Smith, Jr., Lawrence A.

    1984-01-01

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

  10. Zn-catalyzed enantio- and diastereoselective formal [4 + 2] cycloaddition involving two electron-deficient partners: asymmetric synthesis of piperidines from 1-azadienes and nitro-alkenes.

    PubMed

    Chu, John C K; Dalton, Derek M; Rovis, Tomislav

    2015-04-08

    We report a catalytic asymmetric synthesis of piperidines through [4 + 2] cycloaddition of 1-azadienes and nitro-alkenes. The reaction uses earth abundant Zn as catalyst and is highly diastereo- and regioselective. A novel BOPA ligand (F-BOPA) confers high reactivity and enantioselectivity in the process. The presence of ortho substitution on the arenes adjacent to the bis(oxazolines) was found to be particularly impactful, due to limiting the undesired coordination of 1-azadiene to the Lewis acid and thus allowing the reaction to be carried out at lower temperature. A series of secondary kinetic isotope effect studies using a range of ligands implicates a stepwise mechanism for the transformation, involving an initial Michael-type addition of the imine to the nitro-alkene followed by a cyclization event. The stepwise mechanism obviates the electronic requirement inherent to a concerted mechanism, explaining the successful cycloaddition between two electron-deficient partners.

  11. Pyridine is an organocatalyst for the reductive ozonolysis of alkenes

    PubMed Central

    Willand-Charnley, Rachel; Fisher, Thomas J.; Johnson, Bradley M.; Dussault, Patrick H.

    2012-01-01

    Whereas the cleavage of alkenes by ozone typically generates peroxide intermediates that must be decomposed in an accompanying step, ozonolysis in the presence of pyridine directly generates ketones or aldehydes through a process that neither consumes pyridine nor generates any detectable peroxides. The reaction is hypothesized to involve nucleophile-promoted fragmentation of carbonyl oxides via formation of zwitterionic peroxyacetals. PMID:22512349

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

    ERIC Educational Resources Information Center

    Naumescu, Adrienne Kozan; Pasca, Roxana-Diana

    2011-01-01

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

  13. Self-Assembly of Disorazole C1 through a One-Pot Alkyne Metathesis Homodimerization Strategy**

    PubMed Central

    Ralston, Kevin J; Ramstadius, H Clinton; Brewster, Richard C; Niblock, Helen S; Hulme, Alison N

    2015-01-01

    Alkyne metathesis is increasingly explored as a reliable method to close macrocyclic rings, but there are no prior examples of an alkyne-metathesis-based homodimerization approach to natural products. In this approach to the cytotoxic C2-symmetric marine-derived bis(lactone) disorazole C1, a highly convergent, modular strategy is employed featuring cyclization through an ambitious one-pot alkyne cross-metathesis/ring-closing metathesis self-assembly process. PMID:25926364

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

    DOEpatents

    Kent, Michael S.; Saunders, Randall

    1997-01-01

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

  15. Heterobimetallic s-block hydrides by σ-bond metathesis.

    PubMed

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

    2014-08-04

    Reactions between PhSiH3 and alkali-metal diamidoalkylmagnesiates ([M{N(SiMe3)2}2MgBu], M = Li, Na, K) provide either selective alkyl metathesis or the formation of polyhydride aggregates contingent upon the identity of the Group 1 metal. In the case of [M{N(SiMe3)2}2MgBu], this reactivity results in a structurally unprecedented dodecametallic decahydride cluster species.

  16. One step formation of propene from ethene or ethanol through metathesis on nickel ion-loaded silica.

    PubMed

    Iwamoto, Masakazu

    2011-09-13

    Increased propene production is presently one of the most significant objectives in petroleum chemistry. Especially the one-step conversion of ethene to propene (ETP reaction, 3C₂H₄ →2C₃H₆) is the most desired process. In our efforts, nickel ion-loaded mesoporous silica could turn a new type of ETP reaction into reality. The one-step conversion of ethene was 68% and the propene selectivity was 48% in a continuous gas-flow system at 673 K and atmospheric pressure. The reactivity of lower olefins and the dependences of the ETP reaction on the contact time and the partial pressure of ethene were consistent with a reaction mechanism involving dimerization of ethene to 1-butene, isomerization of 1-butene to 2-butene, and metathesis of 2-butene and ethene to yield propene. The reaction was then expanded to an ethanol-to-propene reaction on the same catalyst, in which two possible reaction routes are suggested to form ethene from ethanol. The catalysts were characterized mainly by EXAFS and TPR techniques. The local structures of the nickel species active for the ETP reaction were very similar to that of layered nickel silicate, while those on the inert catalysts were the same as that of NiO particles.

  17. Surface-initiated ring-opening metathesis polymerization (SI-ROMP) to attach a tethered organic corona onto CdSe/ZnS core/shell quantum dots

    NASA Astrophysics Data System (ADS)

    Vatansever, Fatma; Hamblin, Michael R.

    2016-10-01

    Core-shell CdSe/ZnS quantum dots (QDs) are useful as tunable photostable fluorophores for multiple applications in industry, biology, and medicine. However, to achieve the optimum optical properties, the surface of the QDs must be passivated to remove charged sites that might bind extraneous substances and allow aggregation. Here we describe a method of growing an organic polymer corona onto the QD surface using the bottom-up approach of surface-initiated ring-opening metathesis polymerization (SI-ROMP) with Grubbs catalyst. CdSe/ZnS QDs were first coated with mercaptopropionic acid by displacing the original tri-octylphosphine oxide layer, and then reacted with 7-octenyl dimethyl chlorosilane. The resulting octenyl double bonds allowed the attachment of ruthenium alkylidene groups as a catalyst. A subsequent metathesis reaction with strained bicyclic monomers (norbornene-dicarbonyl chloride (NDC), and a mixture of NDC and norbornenylethylisobutyl-polyhedral oligomeric silsesquioxane (norbornoPOSS)) allowed the construction of tethered organic homo-polymer or co-polymer layers onto the QD. Compounds were characterized by FT-IR, 1H-NMR, X-ray photoelectron spectroscopy, differential scanning calorimetry, and transmission electron microscopy. Atomic force microscopy showed that the coated QDs were separate and non-aggregated with a range of diameter of 48-53 nm.

  18. Transition metal complexes supported on metal-organic frameworks for heterogeneous catalysts

    DOEpatents

    Farha, Omar K.; Hupp, Joseph T.; Delferro, Massimiliano; Klet, Rachel C.

    2017-02-07

    A robust mesoporous metal-organic framework comprising a hafnium-based metal-organic framework and a single-site zirconium-benzyl species is provided. The hafnium, zirconium-benzyl metal-organic framework is useful as a catalyst for the polymerization of an alkene.

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

    ERIC Educational Resources Information Center

    Lukaszewicz, Beata

    2007-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Afanasiev, Pavel

    2015-09-01

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

  1. Some limitations of an approach to the assembly of bryostatins by ring-closing metathesis.

    PubMed

    Dumeunier, Raphaël; Gregson, Thomas; MacCormick, Somhairle; Omori, Hiroki; Thomas, Eric J

    2017-03-28

    Preliminary studies into the use of ring-closing metathesis (RCM) in a convergent approach for the total synthesis of bryostatins are described. An ester that would have provided an advanced intermediate for a synthesis of a 20-deoxybryostatin by a RCM was prepared from an unsaturated acid and alcohol corresponding to the C1-C16 and C17-C27 fragments. However, studies of the formation of the C16-C17 double-bond by RCM were not successful and complex mixtures of products were obtained. To provide an insight into factors that may be involved in hindering RCM in this system, a slightly simplified C1-C16 acid and modified C17-C25 alcohols were prepared and their use for the synthesis of analogues of bryostatins was investigated. Although only low yields were obtained, it appeared that macrolides analogous to the bryostatins can be prepared by RCM, using the Grubbs II catalyst, if the precursors lack the two methyl groups at C18. RCM was not observed, however, for substrates in which these methyl groups were present.

  2. Metal-Organic Frameworks as Catalysts for Oxidation Reactions.

    PubMed

    Dhakshinamoorthy, Amarajothi; Asiri, Abdullah M; Garcia, Hermenegildo

    2016-06-06

    This Concept is aimed at describing the current state of the art in metal-organic frameworks (MOFs) as heterogeneous catalysts for liquid-phase oxidations, focusing on three important substrates, namely, alkenes, alkanes and alcohols. Emphases are on the nature of active sites that have been incorporated within MOFs and on future targets to be set in this area. Thus, selective alkene epoxidation with peroxides or oxygen catalyzed by constitutional metal nodes of MOFs as active sites are still to be developed. Moreover, no noble metal-free MOF has been reported to date that can act as a general catalyst for the aerobic oxidation of primary and secondary aliphatic alcohols. In contrast, in the case of alkanes, a target should be to tune the polarity of MOF internal pores to control the outcome of the autooxidation process, resulting in the selective formation of alcohol/ketone mixtures at high conversion.

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

    NASA Astrophysics Data System (ADS)

    Astruc, Didier; Martinez, Victor

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

  4. Metal-catalyzed hydrosilylation of alkenes and alkynes using dimethyl(pyridyl)silane.

    PubMed

    Itami, Kenichiro; Mitsudo, Koichi; Nishino, Akira; Yoshida, Jun-ichi

    2002-04-19

    Metal-catalyzed hydrosilylation of alkenes and alkynes using dimethyl(pyridyl)silane is described. The hydrosilylation of alkenes using dimethyl(2-pyridyl)silane (2-PyMe(2)SiH) proceeded well in the presence of a catalytic amount of RhCl(PPh(3))(3) with virtually complete regioselectivity. By taking advantage of the phase tag property of the 2-PyMe(2)Si group, hydrosilylation products were isolated in greater than 95% purity by simple acid-base extraction. Strategic catalyst recovery was also demonstrated. The hydrosilylation of alkynes using 2-PyMe(2)SiH proceeded with a Pt(CH(2)=CHSiMe(2))(2)O/P(t-Bu)(3) catalyst to give alkenyldimethyl(2-pyridyl)silanes in good yield with high regioselectivity. A reactivity comparison of 2-PyMe(2)SiH with other related hydrosilanes (3-PyMe(2)SiH, 4-PyMe(2)SiH, and PhMe(2)SiH) was also performed. In the rhodium-catalyzed reaction, the reactivity order of hydrosilane was 2-PyMe(2)SiH > 3-PyMe(2)SiH, 4-PyMe(2)SiH, PhMe(2)SiH, indicating a huge rate acceleration with 2-PyMe(2)SiH. In the platinum-catalyzed reaction, the reactivity order of hydrosilane was PhMe(2)SiH, 3-PyMe(2)SiH > 4-PyMe(2)SiH > 2-PyMe(2)SiH, indicating a rate deceleration with 2-PyMe(2)SiH and 4-PyMe(2)SiH. It seems that these reactivity differences stem primarily from the governance of two different mechanisms (Chalk-Harrod and modified Chalk-Harrod mechanisms). From the observed reactivity order, coordination and electronic effects of dimethyl(pyridyl)silanes have been implicated.

  5. Metal-Support Cooperative Catalysts for Environmentally Benign Molecular Transformations.

    PubMed

    Kaneda, Kiyotomi; Mitsudome, Takato

    2017-01-01

    Metal-support cooperative catalysts have been developed for sustainable and environmentally benign molecular transformations. The active metal centers and supports in these catalysts could cooperatively activate substrates, resulting in high catalytic performance for liquid-phase reactions under mild conditions. These catalysts involved hydrotalcite-supported gold and silver nanoparticles with high catalytic activity for organic reactions such as aerobic oxidation, oxidative carbonylation, and chemoselective reduction of epoxides to alkenes and nitrostyrenes to aminostyrenes using alcohols and CO/H2 O as reducing reagents. This high catalytic performance was due to cooperative catalysis between the metal nanoparticles and basic sites of the hydrotalcite support. To increase the metal-support cooperative effect, core-shell nanostructured catalysts consisting of gold or silver nanoparticles in the core and ceria supports in the shell were designed. These core-shell nanocomposite catalysts were effective for the chemoselective hydrogenation of nitrostyrenes to aminostyrenes, unsaturated aldehydes to allyl alcohols, and alkynes to alkenes using H2 as a clean reductant. In addition, these solid catalysts could be recovered easily from the reaction mixture by simple filtration, and were reusable with high catalytic activity.

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  7. Metal-free syn-dioxygenation of alkenes.

    PubMed

    Rawling, Michael J; Tomkinson, Nicholas C O

    2013-03-07

    Reactions employing inexpensive reagents from sustainable sources and with low toxicity are becoming increasingly desirable from an academic and industrial perspective. A fascinating example of a synthetic transformation that requires development of alternative procedures is the osmium catalysed dihydroxylation. Recently there has been considerable interest in achieving this reaction through metal-free procedures. This review describes the methods available for metal-free syn-dioxygenation of alkenes.

  8. Amidoselenation and Amidotelluration of Alkenes using Oxygen as Terminal Oxidant.

    PubMed

    Sun, Kai; Wang, Xin; Zhang, Chong; Zhang, Saifei; Chen, Yao; Jiao, Hezhen; Du, Weimin

    2017-03-16

    A protocol has been established for oxygen-mediated amidoselenation and amidotelluration of alkenes under mild conditions. This method provides a simple route to a series of structurally diverse β-amido selenides and β-amido tellurides in moderate to high yields. The wide substrate scope, good functional group tolerance, ease of large-scale preparation and potential for product derivatization make this reaction attractive for the synthesis of nitrogen-, selenium- and tellurium-containing molecules.

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

    PubMed Central

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

    2011-01-01

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

  10. Biological conversion of gaseous alkenes to liquid chemicals.

    PubMed

    Desai, Shuchi H; Koryakina, Irina; Case, Anna E; Toney, Michael D; Atsumi, Shota

    2016-11-01

    Industrial gas-to-liquid (GTL) technologies are well developed. They generally employ syngas, require complex infrastructure, and need high capital investment to be economically viable. Alternatively, biological conversion has the potential to be more efficient, and easily deployed to remote areas on relatively small scales for the utilization of otherwise stranded resources. The present study demonstrates a novel biological GTL process in which engineered Escherichia coli converts C2-C4 gaseous alkenes into liquid diols. Diols are versatile industrially important chemicals, used routinely as antifreeze agents, polymer precursors amongst many other applications. Heterologous co-expression of a monooxygenase and an epoxide hydrolase in E. coli allows whole cell conversion of C2-C4 alkenes for the formation of ethylene glycol, 1,2-propanediol, 1,2-butanediol, and 2,3-butanediol at ambient temperature and pressure in one pot. Increasing intracellular NADH supply via addition of formate and a formate dehydrogenase increases ethylene glycol production titers, resulting in an improved productivity of 9mg/L/h and a final titer of 250mg/L. This represents a novel biological method for GTL conversion of alkenes to industrially valuable diols.

  11. Amine attack on coordinated alkenes: an interconversion from anti-Markovnikoff to Markovnikoff products.

    PubMed

    Pryadun, Ruslan; Sukumaran, Dinesh; Bogadi, Robert; Atwood, Jim D

    2004-10-06

    A sequence of alkene complexes of platinum, PtCl(2)(PPh(3))(alkene) (alkene = ethylene, propene, 1-butene, cis-2-butene, 1-hexene, 1-octene, and 1-decene), has been prepared. These complexes are characterized by NMR spectroscopy, including assignment of each proton, and X-ray crystal structures of the 1-propene and 1-hexene complexes. Each complex was reacted with diethylamine. For the 1-hexene, 1-octene, and 1-decene complexes, the amine displaces the alkene. For the smaller alkenes, the diethylamine nucleophilically attacks the coordinated alkene. For propene and 1-butene, the low-temperature addition leads to the anti-Markovnikoff nucleophilic attack, which slowly converts at room temperature to the Markovnikoff product. The transformation from anti-Markovnikoff to Markovnikoff addition occurs without diethylamine dissociation.

  12. First acyclic diene metathesis polymerization under biphasic conditions using a dicationic ruthenium alkylidene: access to high-molecular-weight polymers with very low ruthenium contamination.

    PubMed

    Zhao, Jing; Wang, Dongren; Autenrieth, Benjamin; Buchmeiser, Michael R

    2015-01-01

    The acyclic diene metathesis (ADMET) polymerization of 6-hydroxy-1,10-undecadiene (M1) and 6-acetoxy-1,10-undecadiene (M2) by the action of two different catalysts, i.e., the second-generation Grubbs-Hoveyda system ([RuCl2(IMesH2)(CH-2-(2-PrO-C6H4)]) (1) and the dicationic ruthenium alkylidene [Ru(DMF)3(IMesH2)(CH-2-(2-PrO-C6H4)] (2, IMesH2 = 1,3-dimesitylimidazolin-2-ylidene) is reported. Biphasic conditions using 1-butyl-2,3-dimethylimidazolium tetrafluoroborate ([BDMIM(+)BF4(-)]) and 1,2,4-trichlorobenzene (TCB) are applied. Under the chosen conditions (T = 75 °C, 20 mbar), the use of catalyst 1 results only in the formation of low-molecular-weight polymers (Mn ≤ 10,000 g mol(-1)), while catalyst 2 allows for the high yield synthesis of high-molecular-weight polymers (Mn ≤ 40,000 g mol(-1), yields ≤ 99%). Irrespective of the catalyst used, all polymers display a high trans-content (>95%). Notably, Ru-contamination of the target polymers without any additional purification is as low as 1.2 ppm with catalyst 2. Together with the high yields and high molecular weights, the low Ru-contaminations clearly illustrate the advantages of the biphasic setup.

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

    DOEpatents

    Kent, M.S.; Saunders, R.

    1997-02-18

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

  14. Asymmetric reduction of activated alkenes using an enoate reductase from Gluconobacter oxydans.

    PubMed

    Richter, Nina; Gröger, Harald; Hummel, Werner

    2011-01-01

    A recombinant enoate reductase from Gluconobacter oxydans was heterologously expressed, purified, characterised and applied in the asymmetric reduction of activated alkenes. In addition to the determination of the kinetic properties, the major focus of this work was to utilise the enzyme in the biotransformation of different interesting compounds such as 3,5,5-trimethyl-2-cyclohexen-1,4-dione (ketoisophorone) and (E/Z)-3,7-dimethyl-2,6-octadienal (citral). The reaction proceeded with excellent stereoselectivities (>99% ee) as well as absolute chemo- and regioselectivity, only the activated C=C bond of citral was reduced by the enoate reductase, while non-activated C=C bond and carbonyl moiety remained untouched. The described strategy can be used for the production of enantiomerically pure building blocks, which are difficult to prepare by chemical means. In general, the results show that the investigated enoate reductase is a promising catalyst for the use in asymmetric C=C bond reductions.

  15. Catalyst-Controlled Regioselectivity in the Synthesis of Branched Conjugated Dienes via Aerobic Oxidative Heck Reactions

    PubMed Central

    Zheng, Changwu; Wang, Dian; Stahl, Shannon S.

    2012-01-01

    Pd-catalyzed aerobic oxidative coupling of vinylboronic acids and electronically unbiased alkyl olefins provides regioselective access to 1,3-disubstituted conjugated dienes. Catalyst-controlled regioselectivity is achieved by using 2,9-dimethylphenanthroline as a ligand. The observed regioselectivity is opposite to that observed from a traditional (non-oxidative) Heck reaction between a vinyl bromide and an alkene. DFT computational studies reveal that steric effects of the 2,9-dimethylphenanthroline ligand promote C–C bond-formation at the internal position of the alkene. PMID:22998540

  16. Homochiral nickel coordination polymers based on salen(Ni) metalloligands: synthesis, structure, and catalytic alkene epoxidation.

    PubMed

    Huang, Yuanbiao; Liu, Tianfu; Lin, Jingxiang; Lü, Jian; Lin, Zujin; Cao, Rong

    2011-03-21

    One-dimensional (1D) homochiral nickel coordination polymers [Ni(3)(bpdc)(RR-L)(2)·(DMF)](n) (2R, RR-L = (R,R)-(-)-1,2-cyclohexanediamino-N,N'-bis(3-tert-butyl-5-(4-pyridyl)salicylidene), bpdc = 4,4'-biphenyldicarboxylic acid) and [Ni(3)(bpdc)(SS-L)(2)·(DMF)](n) (2S, SS-L = (S,S)-(-)-1,2-cyclohexanediamino-N,N'-bis(3-tert-butyl-5-(4-pyridyl)salicylidene) based on enantiopure pyridyl-functionalized salen(Ni) metalloligand units NiL ((1,2-cyclohexanediamino-N,N'-bis(3-tert-butyl-5-(4-pyridyl)salicylidene))Ni(II)) have been synthesized and characterized by microanalysis, IR spectroscopy, solid-state UV-vis spectroscopy, thermogravimetric analysis (TGA), circular dichroism (CD) spectroscopy, cyclic voltammetric measurement, and powder and single crystal X-ray diffraction. Each NiL as unbridging pendant metalloligand uses one terminal pyridyl group to coordinate achiral unit (nickel and bpdc(2-)) building a helical chain, while the other pyridyl group remains uncoordinated. Both 2R and 2S contain left- and right-handed helical chains made of the achiral building blocks, while the NiL as remote external chiral source is perpendicular to the backbone of the helices. The nickel coordination polymers 2R and 2S containing unsaturated active nickel center in metalloligand NiL can be used as self-supported heterogeneous catalysts. They show catalytic activity comparable with their homogeneous counterpart in alkene epoxidation and exhibit great potential as recyclable catalysts.

  17. Synthesis of nanosized silicon particles by a rapid metathesis reaction

    SciTech Connect

    Won, C.W.; Nersisyan, H.H.; Won, H.I.; Lee, H.H.

    2009-11-15

    A solid-state rapid metathesis reaction was performed in a bed of sodium silicofluoride (Na{sub 2}SiF{sub 6}) and sodium azide (NaN{sub 3}) powders diluted with sodium fluoride (NaF), to produce silicon nanoparticles. After a local ignition of Na{sub 2}SiF{sub 6}+4NaN{sub 3}+kNaF mixture (here k is mole number of NaF), the reaction proceeded in a self-sustaining combustion mode developing high temperatures (950-1000 deg. C) on very short time scales (a few seconds). Silicon nanoparticles prepared by the combustion process was easily separated from the salt byproducts by simple washing with distilled water. The structural and morphological studies on the nanoparticles were carried out using X-ray diffractometer (XRD) and field emission scanning electron microscope (FESEM). The mean size of silicon particles calculated from the FESEM image was about 37.75 nm. FESEM analysis also shows that the final purified product contains a noticeable amount of silicon fibers, dendrites and blocks, along with nanoparticles. The mechanism of Si nanostructures formation is discussed and a simple model for interpretation of experimental results is proposed. - Graphical abstract: Silicon nanoparticles 37.75 nm in mean diameter was obtained by rapid metathesis reaction performed in Na{sub 2}SiF{sub 6}+4NaN{sub 3} powder bed diluted with NaF.

  18. Regioselective photocycloaddition of pyridine derivatives to electron-rich alkenes.

    PubMed

    Sakamoto, Masami; Sano, Takeru; Fujita, Shohei; Ando, Masaru; Yamaguchi, Kentaro; Mino, Takashi; Fujita, Tsutomu

    2003-02-21

    Irradiation of a benzene solution of 3-cyano-2,6-dimethoxypyridine in the presence of ethyl vinyl ether (EVE) gave 1:1 photoadducts, 3-cyano-5-ethoxy-2,8-dimethoxy-4,5-dihydroazocine, in good yields, whose structure was established by X-ray single-crystal analysis. The photoadduct was produced via cycloaddition between the C3-C4 position of the pyridine derivatives and an alkene chromophore. On the other hand, 3-cyano-2,6-dimethoxy-4-methylpyridine cycloadds to EVE at the C2-C3 position of the pyridine ring upon irradiation. The difference is explained on the basis of the steric effect.

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

    Code of Federal Regulations, 2011 CFR

    2011-07-01

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

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

    Code of Federal Regulations, 2010 CFR

    2010-07-01

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

  1. 40 CFR 721.4464 - Mixture of hydrofluoro alkanes and hydrofluoro alkene.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

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

  2. 40 CFR 721.4464 - Mixture of hydrofluoro alkanes and hydrofluoro alkene.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

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

  3. 40 CFR 721.4464 - Mixture of hydrofluoro alkanes and hydrofluoro alkene.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

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

  4. One-pot o-nitrobenzenesulfonylhydrazide (NBSH) formation-diimide alkene reduction protocol.

    PubMed

    Marsh, Barrie J; Carbery, David R

    2009-04-17

    A one-pot protocol for the formation of 2-nitrobenzenesulfonylhydrazide (NBSH) from commercial reagents and subsequent alkene reduction is presented. The transformation is operationally simple and generally efficient for effecting diimide alkene reductions. A range of 16 substrates have been reduced, highlighting the unique chemoselectivity of diimide as a reduction system.

  5. Intermolecular Addition of Glycosyl Halides to Alkenes Mediated by Visible Light

    DTIC Science & Technology

    2010-08-25

    Visible light, an amine reductant, and a Ru(bpy)32+ photocatalyst can be used to mediate the addition of glycosyl halides into alkenes to synthesize...and a Ru(bpy)32+ photocatalyst can be used to mediate the addition of glycosyl halides into alkenes to synthesize important C-glycosides. This method

  6. Regioselective hydrothiolation of alkenes bearing heteroatoms with thiols catalyzed by palladium diacetate.

    PubMed

    Tamai, Taichi; Ogawa, Akiya

    2014-06-06

    In sharp contrast to many examples of transition-metal-catalyzed hydrothiolation of alkynes, the corresponding catalytic addition of thiols to alkenes has remained undeveloped. However, a novel Pd-catalyzed addition of thiols to alkenes bearing a heteroatom, such as oxygen and nitrogen, is found to proceed under mild conditions to give the corresponding Markovnikov adducts, regioselectively, in good yields.

  7. Ruthenium—Arene Complexes Derived from NHC•CO2 and NHC•CS2 Zwitterionic Adducts and Their Use in Olefin Metathesis

    NASA Astrophysics Data System (ADS)

    Delaude, Lionel; Demonceau, Albert

    A range of imidazol(in)ium-2-carboxylates and -dithiocarboxylates bearing alkyl or aryl groups on their nitrogen atoms were prepared by reacting the corresponding N-heterocyclic carbenes (NHCs) with either carbon dioxide or carbon disulfide. All the zwitterionic products were characterized by various analytical techniques, including thermogravimetric analysis (TGA). Their ability to act as NHC ligand precursors for in situ catalytic applications was investigated in the ruthenium-promoted ring-opening metathesis polymerization (ROMP) of cyclo-octene. Upon exposure to the [RuCl2(p-cymene)]2 dimer, the NHC CO2 adducts readily dissociated to generate [RuCl2(p-cymene)(NHC)] complexes that were highly active catalyst precursors for olefin metathesis. Conversely, the NHC CS2 betaines retained their zwitterionic nature and led to new cationic complexes of the [RuCl(p-cymene)(NHC CS2)]+PF6 - type that were devoid of any significant catalytic activity in the reaction under consideration

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

    SciTech Connect

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

    2008-05-22

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

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

    SciTech Connect

    Afanasiev, Pavel

    2015-09-15

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

  10. Thermal electron attachment to chlorinated alkenes in the gas phase

    NASA Astrophysics Data System (ADS)

    Wnorowski, K.; Wnorowska, J.; Michalczuk, B.; Jówko, A.; Barszczewska, W.

    2017-01-01

    This paper reports the measurements of the rate coefficients and the activation energies of the electron capture processes with various chlorinated alkenes. The electron attachment processes in the mixtures of chlorinated alkenes with carbon dioxide have been investigated using a Pulsed Townsend technique. This study has been performed in the temperature range (298-378) K. The obtained rate coefficients more or less depended on temperature in accordance to Arrhenius equation. The activation energies (Ea's) were determined from the fit to the experimental data points with function ln(k) = ln(A) - Ea/kBT. The rate coefficients at 298 K were equal to 1.0 × 10-10 cm3 s-1, 2.2 × 10-11 cm3 s-1, 1.6 × 10-9 cm3 s-1, 4.4 × 10-8 cm3 s-1, 2.9 × 10-12 cm3 s-1 and 7.3 × 10-12 cm3 s-1 and activation energies were: 0.27 eV, 0.26 eV, 0.25 eV, 0.21 eV, 0.55 eV and 0.42 eV, for trans-1,2-dichloroethylene, cis-1,2-dichloroethylene, trichloroethylene, tetrachloroethylene, 2-chloropropene, 3-chloropropene respectively.

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

    SciTech Connect

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

    2010-01-07

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

  12. Reforming catalysts

    SciTech Connect

    Givens, E.N.; Plank, C.J.; Rosinski, E.J.

    1980-03-04

    Crystalline aluminosilicate zeolites are mixed with conventional reforming catalysts to produce new catalytic compositions with high catalytic activity and selectivity and excellent aging characteristics. These new catalytic compositions may be utilized alone or in conjunction with conventional reforming catalysts. The acidic activity of the total catalyst system is controlled within defined limits. When so controlled the utility of these catalyst systems in reforming hydrocarbon mixtures is to reduce the C1 and C2 concentrations in reformer gas product, while increasing the C3 and C4 concentrations and maintaining high liquid yield at high octane numbers.

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed Central

    Kunz, Oliver

    2013-01-01

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

  15. High-performance vitrimers from commodity thermoplastics through dioxaborolane metathesis.

    PubMed

    Röttger, Max; Domenech, Trystan; van der Weegen, Rob; Breuillac, Antoine; Nicolaÿ, Renaud; Leibler, Ludwik

    2017-04-07

    Windmills, cars, and dental restoration demand polymer materials and composites that are easy to process, assemble, and recycle while exhibiting outstanding mechanical, thermal, and chemical resistance. Vitrimers, which are polymer networks able to shuffle chemical bonds through exchange reactions, could address these demands if they were prepared from existing plastics and processed with fast production rates and current equipment. We report the metathesis of dioxaborolanes, which is rapid and thermally robust, and use it to prepare vitrimers from polymers as different as poly(methyl methacrylate), polystyrene, and high-density polyethylene that, although permanently cross-linked, can be processed multiple times by means of extrusion or injection molding. They show superior chemical resistance and dimensional stability and can be efficiently assembled. The strategy is applicable to polymers with backbones made of carbon-carbon single bonds.

  16. Bimetallic Catalysts.

    ERIC Educational Resources Information Center

    Sinfelt, John H.

    1985-01-01

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

  17. Oxyhydrochlorination catalyst

    DOEpatents

    Taylor, Charles E.; Noceti, Richard P.

    1992-01-01

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

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

    PubMed Central

    Piou, Tiffany; Rovis, Tomislav

    2015-01-01

    Alkenes are the most ubiquitous pro-chiral functional groups accessible to synthetic chemists. For this reason, difunctionalization reactions of alkenes are particularly important, as they can be used to access highly complex molecular architectures.1,2 Stereoselective oxidation reactions, including dihydroxylation, aminohydroxylation and halogenation reactions,3,4,5,6 are well-established methods for functionalizing alkenes. However, the intermolecular incorporation of both carbon- and nitrogen-based functionalities stereoselectively across an alkene has not been reported. In this manuscript, we describe the Rh(III)-catalyzed syn carboamination of alkenes initiated by a C–H activation event that uses enoxyphthalimides as the source of the carbon and the nitrogen functionalities. The reaction methodology allows for the stereospecific formation of one C–C and one C–N bond across an alkene in a fully intermolecular sense, which is unprecedented. The reaction design involves the in situ generation of a bidentate directing group and the use of a novel cyclopentadienyl ligand to control the reactivity of Rh(III). The results provide a new route to functionalized alkenes and are expected to lead to the more convergent and stereoselective assembly of amine-containing acyclic molecules. PMID:26503048

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed Central

    Chiarucci, Michel

    2013-01-01

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

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

    PubMed

    Chiarucci, Michel; Bandini, Marco

    2013-11-21

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

  2. Selenide-Catalyzed Stereoselective Construction of Tetrasubstituted Trifluoromethylthiolated Alkenes with Alkynes.

    PubMed

    Wu, Jin-Ji; Xu, Jia; Zhao, Xiaodan

    2016-10-17

    The efficient regio- and stereoselective construction of tetrasubstituted alkenes is challenging and very important. For this purpose, we have developed an efficient approach to synthesize tetrasubstituted trifluoromethylthiolated alkenes from simple alkynes in excellent regio- and stereoselectivities by selenide-catalyzed multicomponent coupling. Using this method, trifluoromethylthiolated alkenyl triflates and arenes were achieved. In particular, the triflates could be further converted into carbofunctionalized alkenes by palladium-catalyzed cross-coupling reactions. Our method provides a new pathway for the construction of trifluoromethylthiolated tricarboalkenes. This work presents the first example of selenide-catalyzed trifluoromethylthiolation of alkynes and enables the challenging functionalizations of alkynes.

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

    PubMed

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

    2015-08-28

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

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

    PubMed

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

    2016-02-08

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

  5. Investigations into Chemical Hydrogen Storage and the anti-Markovnikov Hydroamination of Alkenes

    NASA Astrophysics Data System (ADS)

    St. John, Anthony J.

    The known carbon-boron-nitrogen (CBN) material ethylenediamine bisborane (EDBB) has been prepared and tested as a potential hydrogen storage material. Dehydrogenation of EDBB was achieved using the (t BuPOCOP)Ir(H)2 (t BuPOCOP = 2,6-bis(OPtBu2)C 6H3) catalyst. This reaction results in the release of two equivalents of hydrogen per molecule of EDBB. The product of this reaction is an insoluble, likely oligomeric, species. Heating the reaction mixture does not result in the release of additional equivalents of hydrogen. A new CBN material, 1,2-B,N-cyclohexane, was targeted as a potential hydrogen storage material. The enthalpy of dehydrogenation of 1,2-B,N-cyclohexane to 1,2-dihydro-1,2-azaborine was calculated to be 23.5 kcal/mol at 298 K using the B3LYP basis set. Ultimately, our collaborators at the University of Oregon prepared 1,2-B,N-cyclohexane. This molecule is a stable solid and undergoes thermal dehydrogenation of the B-N bond at 150 °C. The dehydrogenation of a variety of cyclic CBN materials was studied with the ( tBuPOCOP)Ir(H)2 catalyst. A number of cobalt-pincer complexes were tested as ammonia borane (AB) dehydrogenation catalysts. (PhPSiNSiP)CoCl (PhPSiNSiP = (N(SiMe2CH2PPh 2)2) was found to be a very active precatalyst for AB dehydrogenation, releasing 1 equivalent of hydrogen at 2.0 mol % catalyst loading within 5 minutes. The product of this reaction was characterized as cyclopentaborazane. The catalyst lifetime is limited and the identity of the active species remains unknown. A novel [(tBuPOCOP)Co] 2Hg complex was synthesized by reaction of (t BuPOCOP)CoI with Na/Hg. This complex was fully characterized by 1H NMR spectroscopy, elemental analysis, and X-ray crystallography. A new catalytic pathway for the anti-Markovnikov hydroamination of alkenes is proposed. The individual steps of this pathway were studied with the [(MTPA)Rh(propene)][BPh 4] (MTPA = tris((6-methyl-2-pyridyl)methyl)amine) complex. Protonation of this complex with anilinium

  6. Copper-catalyzed alkene aziridination with N-tosyloxycarbamates.

    PubMed

    Lebel, Hélène; Lectard, Sylvain; Parmentier, Michaël

    2007-11-08

    Pyridine copper complexes were found as active catalysts for the intramolecular aziridination of allylic N-tosyloxycarbamates and the intermolecular aziridination of styrenes with trichloroethyl N-tosyloxycarbamates. Free aziridines were easily obtained by basic deprotection of the trichloroethyl group.

  7. Shell Higher Olefins Process.

    ERIC Educational Resources Information Center

    Lutz, E. F.

    1986-01-01

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

  8. DFT study of the 1-octene metathesis reaction mechanism with WCl6/C catalytic system.

    PubMed

    Yüksel, Dilek; Düz, Bülent; Sevin, Fatma

    2008-05-22

    A catalytic system consisting of tungsten carbene generated from WCl(6) and an atomic carbon is investigated theoretically for the metathesis of 1-octene at B3LYP/extended LANL2DZ level of DFT. The ground-state geometries and charge distributions of the structures belonging to the reaction mechanism are located. Energetics for the complete set of reactions, involving the formation of the tungsten carbene precatalyst, Cl(4)WCCl(2), the formation of tungsten methylidene and tungsten heptylidene with this precatalyst, and finally productive and degenerative metathesis steps with these alkylidene species are calculated in terms of total electronic energy and thermal energies. The free-energy (ΔG(298)) surfaces of the structures involved in the related reactions are constructed. In addition, solvent effects on the single point energies of the structures are investigated for two different solvents, namely, cyclohexane and chloroform. The results indicate that the formation of the catalytically active heptylidene is energetically favored in comparison to the formation of methylidene, while the degenerative and productive metathesis steps are competitive. In the catalytic cycle, the formation of ethylene is exothermic, while the formation of 7-tetradecene is endothermic. As expected, solvent effects on the metathesis reactions are minor and solvation does not cause any change in the directions of the overall metathesis reactions.

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

    PubMed

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

    2016-01-22

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

  10. Biobased production of alkanes and alkenes through metabolic engineering of microorganisms.

    PubMed

    Kang, Min-Kyoung; Nielsen, Jens

    2016-08-26

    Advancement in metabolic engineering of microorganisms has enabled bio-based production of a range of chemicals, and such engineered microorganism can be used for sustainable production leading to reduced carbon dioxide emission there. One area that has attained much interest is microbial hydrocarbon biosynthesis, and in particular, alkanes and alkenes are important high-value chemicals as they can be utilized for a broad range of industrial purposes as well as 'drop-in' biofuels. Some microorganisms have the ability to biosynthesize alkanes and alkenes naturally, but their production level is extremely low. Therefore, there have been various attempts to recruit other microbial cell factories for production of alkanes and alkenes by applying metabolic engineering strategies. Here we review different pathways and involved enzymes for alkane and alkene production and discuss bottlenecks and possible solutions to accomplish industrial level production of these chemicals by microbial fermentation.

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

    PubMed Central

    Arai, Yusuke; Tomita, Ren; Ando, Gaku

    2015-01-01

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

  12. Synthesis of sulfonated oxindoles by potassium iodide catalyzed arylsulfonylation of activated alkenes with sulfonylhydrazides in water.

    PubMed

    Li, Xiaoqing; Xu, Xiangsheng; Hu, Peizhu; Xiao, Xuqiong; Zhou, Can

    2013-07-19

    A catalytic system consisting of KI, 18-crown-6, and TBHP for arylsulfonylation of activated alkenes with sulfonylhydrazides as sulfonyl precursor is described. This protocol provides a practical and environmentally benign method for the construction of sulfonated oxindoles in water.

  13. Catalyst mixtures

    DOEpatents

    Masel, Richard I.; Rosen, Brian A.

    2017-02-14

    Catalysts that include at least one catalytically active element and one helper catalyst can be used to increase the rate or lower the overpotential of chemical reactions. The helper catalyst can simultaneously act as a director molecule, suppressing undesired reactions and thus increasing selectivity toward the desired reaction. These catalysts can be useful for a variety of chemical reactions including, in particular, the electrochemical conversion of CO.sub.2 or formic acid. The catalysts can also suppress H.sub.2 evolution, permitting electrochemical cell operation at potentials below RHE. Chemical processes and devices using the catalysts are also disclosed, including processes to produce CO, OH.sup.-, HCO.sup.-, H.sub.2CO, (HCO.sub.2).sup.-, H.sub.2CO.sub.2, CH.sub.3OH, CH.sub.4, C.sub.2H.sub.4, CH.sub.3CH.sub.2OH, CH.sub.3COO.sup.-, CH.sub.3COOH, C.sub.2H.sub.6, O.sub.2, H.sub.2, (COOH).sub.2, or (COO.sup.-).sub.2, and a specific device, namely, a CO.sub.2 sensor.

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

    SciTech Connect

    Wayne Tikkanen

    2006-12-31

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

  15. Photo-oxidation catalysts

    DOEpatents

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

    2009-07-14

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

  16. Ruthenium-catalyzed hydroformylation/reduction of olefins to alcohols: extending the scope to internal alkenes.

    PubMed

    Wu, Lipeng; Fleischer, Ivana; Jackstell, Ralf; Profir, Irina; Franke, Robert; Beller, Matthias

    2013-09-25

    In the presence of 2-phosphino-substituted imidazole ligands and Ru3(CO)12 or Ru(methylallyl)2(COD) direct hydroformylation and hydrogenation of alkenes to alcohols takes place. In addition to terminal alkenes, also more challenging internal olefins are converted preferentially to industrially important linear alcohols in high yield (up to 88%) and regioselectivity (n:iso up to 99:1).

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

    NASA Technical Reports Server (NTRS)

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

    1950-01-01

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

  18. Stereochemically Defined Various Multisubstituted Alkenes Bearing a Tetrafluoroethylene (-CF2CF2-) Fragment.

    PubMed

    Sakaguchi, Yukiho; Yamada, Shigeyuki; Konno, Tsutomu; Agou, Tomohiro; Kubota, Toshio

    2017-02-03

    Highly regio- and stereoselective transformation of commercially available 4-bromo-3,3,4,4-tetrafluoro-1-butene into multisubstituted alkenes having a tetrafluoroethylene fragment through Heck reactions and/or Suzuki-Miyaura cross-coupling reactions was established. Thus, the obtained alkenes underwent a smooth reductive coupling reaction with aldehydes under the influence of MeLi/LiBr-free, affording structurally unprecedented fluorinated materials.

  19. Iminoxyl radical-promoted dichotomous cyclizations: efficient oxyoximation and aminooximation of alkenes.

    PubMed

    Peng, Xie-Xue; Deng, Yun-Jing; Yang, Xiu-Long; Zhang, Lin; Yu, Wei; Han, Bing

    2014-09-05

    A novel iminoxyl radical-involved metal-free approach to vicinal oxyoximation and aminooximation of unactivated alkenes is developed. This method utilizes the dichotomous reactivity of the iminoxyl radical to furnish a general difunctionalization on alkenes using simple tert-butyl nitrite (TBN) as the iminoxyl radical initiator as well the carbon radical trap. By using this protocol, oxime featured 4,5-dihydroisoxazoles and cyclic nitrones were facilely prepared from β,γ- and γ,δ-unsaturated ketoximes, respectively.

  20. Heterogeneous allylsilylation of aromatic and aliphatic alkenes catalyzed by proton-exchanged montmorillonite.

    PubMed

    Motokura, Ken; Matsunaga, Shigekazu; Miyaji, Akimitsu; Sakamoto, Yasuharu; Baba, Toshihide

    2010-04-02

    Allylsilylation of an alkene is the only known procedure to install both silyl and allyl groups onto a carbon-carbon double bond directly. Proton-exchanged montmorillonite showed excellent catalytic performances for the allylsilylation of alkenes. For example, the reaction of p-chlorostyrene with allyltrimethylsilane proceeded smoothly to afford the corresponding allylsilylated product in 95% yield. We also attempted to isolate the reaction intermediate on the montmorillonite surface to investigate the reaction mechanism.

  1. Direct kinetic measurements of reactions between the simplest Criegee intermediate CH2OO and alkenes.

    PubMed

    Buras, Zachary J; Elsamra, Rehab M I; Jalan, Amrit; Middaugh, Joshua E; Green, William H

    2014-03-20

    The simplest Criegee Intermediate (CH2OO), a well-known biradical formed in alkene ozonolysis, is known to add across double bonds. Here we report direct experimental rate measurements of the simplest Criegee Intermediate reacting with C2–C4 alkenes obtained using the laser flash photolysis technique probing the recently measured B(1)A′ ← X(1)A′ transition in CH2OO. The measured activation energy (298–494 K) for CH2OO + alkenes is Ea ≈ 3500 ± 1000 J mol(–1) for all alkyl substituted alkenes and Ea = 7000 ± 900 J mol(–1) for ethene. The measured Arrhenius pre-exponential factors (A) vary between (2 ± 1) × 10(–15) and (11 ± 3) × 10(–15) cm(3) molecule(–1) s(–1). Quantum chemical calculations of the corresponding rate coefficients reproduce qualitative reactivity trends but overestimate the absolute rate coefficients. Despite the small Ea's, the CH2OO + alkene rate coefficients are almost 2 orders of magnitude smaller than those of similar reactions between CH2OO and carbonyl compounds. Using the rate constants measured here, we estimate that, under typical atmospheric conditions, reaction with alkenes does not represent a significant sink of CH2OO. In environments rich in C═C double bonds, however, such as ozone-exposed rubber or emission plumes, these reactions can play a significant role.

  2. Well-Defined Polymers Bearing Pendent Alkene Functionalities via Selective RAFT Polymerization

    PubMed Central

    Ma, Jun; Cheng, Chong; Sun, Guorong; Wooley, Karen L.

    2009-01-01

    A facile synthetic approach for the preparation of well-defined (co)polymers bearing pendent alkene functionalities was established by selective reversible addition-fragmentation chain transfer (RAFT) (co)polymerization. A divinyl monomer 4-(3′-buten-1′-oxy)-2,3,5,6-tetrafluorostyrene (1) with a styrenyl group and a pendent alkene group was synthesized. Due to a very high reactivity of the styrenyl group relative to the alkene group in 1, functional fluoro(co)polymers with both well-defined structures and pendent alkene groups were prepared by RAFT polymerizations of 1 and copolymerization of 1 with pentafluorostyrene (PFS). Alkene-functionalized diblock copolymers were also prepared by RAFT copolymerization of 1 with PFS or styrene, extending from a poly(styrene-alt-maleic anhydride) macro-chain transfer agent. Hydrolysis and ammonolysis of these copolymers resulted in amphiphilic diblock fluorocopolymers with alkene-functionalized hydrophobic segments, which were shown to form internally-functionalized micelles in THF-water. PMID:20640195

  3. Synthesis of nanosized silicon particles by a rapid metathesis reaction

    NASA Astrophysics Data System (ADS)

    Won, C. W.; Nersisyan, H. H.; Won, H. I.; Lee, H. H.

    2009-11-01

    A solid-state rapid metathesis reaction was performed in a bed of sodium silicofluoride (Na 2SiF 6) and sodium azide (NaN 3) powders diluted with sodium fluoride (NaF), to produce silicon nanoparticles. After a local ignition of Na 2SiF 6+4NaN 3+ kNaF mixture (here k is mole number of NaF), the reaction proceeded in a self-sustaining combustion mode developing high temperatures (950-1000 °C) on very short time scales (a few seconds). Silicon nanoparticles prepared by the combustion process was easily separated from the salt byproducts by simple washing with distilled water. The structural and morphological studies on the nanoparticles were carried out using X-ray diffractometer (XRD) and field emission scanning electron microscope (FESEM). The mean size of silicon particles calculated from the FESEM image was about 37.75 nm. FESEM analysis also shows that the final purified product contains a noticeable amount of silicon fibers, dendrites and blocks, along with nanoparticles. The mechanism of Si nanostructures formation is discussed and a simple model for interpretation of experimental results is proposed.

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

    NASA Astrophysics Data System (ADS)

    Mohite, Dhairyashil P.

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

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

    PubMed

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

    2010-02-01

    Aliphatic hydrocarbons are highly appealing targets for advanced cellulosic biofuels, as they are already predominant components of petroleum-based gasoline and diesel fuels. We have studied alkene biosynthesis in Micrococcus luteus ATCC 4698, a close relative of Sarcina lutea (now Kocuria rhizophila), which 4 decades ago was reported to biosynthesize iso- and anteiso-branched, long-chain alkenes. The underlying biochemistry and genetics of alkene biosynthesis were not elucidated in those studies. We show here that heterologous expression of a three-gene cluster from M. luteus (Mlut_13230-13250) in a fatty acid-overproducing Escherichia coli strain resulted in production of long-chain alkenes, predominantly 27:3 and 29:3 (no. carbon atoms: no. C=C bonds). Heterologous expression of Mlut_13230 (oleA) alone produced no long-chain alkenes but unsaturated aliphatic monoketones, predominantly 27:2, and in vitro studies with the purified Mlut_13230 protein and tetradecanoyl-coenzyme A (CoA) produced the same C(27) monoketone. Gas chromatography-time of flight mass spectrometry confirmed the elemental composition of all detected long-chain alkenes and monoketones (putative intermediates of alkene biosynthesis). Negative controls demonstrated that the M. luteus genes were responsible for production of these metabolites. Studies with wild-type M. luteus showed that the transcript copy number of Mlut_13230-13250 and the concentrations of 29:1 alkene isomers (the dominant alkenes produced by this strain) generally corresponded with bacterial population over time. We propose a metabolic pathway for alkene biosynthesis starting with acyl-CoA (or-ACP [acyl carrier protein]) thioesters and involving decarboxylative Claisen condensation as a key step, which we believe is catalyzed by OleA. Such activity is consistent with our data and with the homology (including the conserved Cys-His-Asn catalytic triad) of Mlut_13230 (OleA) to FabH (beta-ketoacyl-ACP synthase III), which

  6. Highly dispersed metal catalyst

    DOEpatents

    Xiao, Xin; West, William L.; Rhodes, William D.

    2016-11-08

    A supported catalyst having an atomic level single atom structure is provided such that substantially all the catalyst is available for catalytic function. A process of forming a single atom catalyst unto a porous catalyst support is also provided.

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

    DOEpatents

    Wickham, David; Cook, Ronald

    2008-10-28

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

  8. FTIR studies of titanium tetrachloride and magnesium dichloride complexes with aromatic esters relevant to Ziegler-Natta catalysts

    NASA Astrophysics Data System (ADS)

    Solli, Kjell-Arne; Ystenes, Martin; Sobota, Piotr

    1992-03-01

    Esters of aromatic carboxylic acids and dicarboxylic acids show different effects when used as electron donors in the synthesis of milled MgCl2-supported Ziegler-Natta catalysts. Such Ziegler-Natta catalysts are synthesized by cogrinding anhydrous MgCl2 with the ester, then reacting the resulting support with TiCl4 followed by washing and drying. Alternatively, the catalyst may be synthesized by cogrinding MgCl2 with a TiCl4- aromatic ester complex. The catalyst is activated by a trialkyl aluminum in order to polymerize propene or other (alpha) -alkenes. Esters of the monoacids generally enhance the activity of the catalyst (relative to no ester), and the produced polypropene is also more isotactic. Esters of the diacids also enhance the isotacticity of the polymer produced somewhat, but the activity of the catalyst is lower.

  9. Paternò-Büchi reaction between furan and heterocyclic aldehydes: oxetane formation vs. metathesis.

    PubMed

    D'Auria, Maurizio; Racioppi, Rocco; Viggiani, Licia

    2010-08-01

    The photochemical reaction of 2-substituted heterocyclic aldehydes with furan gave the corresponding exo oxetane derivatives through the excited triplet state. However, in situ the oxetane derivatives were converted through a metathesis reaction into the corresponding Z,E-butadienyl formate derivatives. On the contrary, 3-substituted heterocyclic aldehydes gave the corresponding exo oxetane derivatives. The effect of 2-substituted heterocyclic ring in order to facilitate the metathesis reaction is explained considering the possible participation of the pi aromatic orbitals in the oxetane C-O bond cleavage.

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

    NASA Astrophysics Data System (ADS)

    Casey, Charles P.

    2006-02-01

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

  11. Reforming catalyst

    SciTech Connect

    Baird, W.C. Jr.; Swan, G.A.

    1991-11-19

    This patent describes a catalyst useful for reforming a naphtha feed at high severity reforming conditions. It comprises the metals, platinum, rhenium and iridium on a refractory porous inorganic oxide support, the support consisting essentially of alumina, wherein the concentration by weight of each of the metals platinum and rhenium is at least 0.1 percent and iridium at least 0.15 percent and at least one of the metals is present in a concentration of at least 0.3 percent, and the sum-total; concentration of the metals is greater than 0.9 percent, and wherein each catalyst particle contains all three of the metals platinum, rhenium and iridium. This patent also describes this composition wherein the catalyst contains from about 0.1 percent to about 3 percent of a halogen and from about 0.05 percent to about 0.02 percent sulfur.

  12. Imaging the dynamics of chlorine atom reactions with alkenes

    NASA Astrophysics Data System (ADS)

    Estillore, Armando D.; Visger, Laura M.; Suits, Arthur G.

    2010-08-01

    We report a study of chlorine atom reactions with a series of target monounsaturated alkene molecules: 1-pentene, 1-hexene, 2-hexene, and cyclohexene. These reactions were studied using crossed-beam dc slice ion imaging at collision energies of 4 and 7 kcal/mol. Images of the reactively scattered alkenyl radical products were obtained via single photon ionization at 157 nm. The angular distributions at low collision energy are largely isotropic, suggesting the formation of a complex that has a lifetime comparable to or longer than its rotational period, followed by HCl elimination. At high collision energy, the distributions show a sharp forward peak superimposed on the isotropic component accounting for ˜13% of the product flux. The translational energy distributions peak near zero for the backscattered product, in sharp contrast to the results for alkanes. In the forward direction, the translational energy distributions change dramatically with collision energy. At the high collision energy, a sharp forward peak at ˜80% of the collision energy appears, quite reminiscent of results of our recent study of Cl+pentane reactions. The scattering distributions for all target molecules are similar, suggesting similarity of the reaction dynamics among these molecules. Ab initio calculations of the energetics and ionization energies for the various product channels were performed at the CBS-QB3 level to aid in interpreting the results.

  13. Frustrated Lewis Pair-Like Reactivity of Rare-Earth Metal Complexes: 1,4-Addition Reactions and Polymerizations of Conjugated Polar Alkenes.

    PubMed

    Xu, Pengfei; Yao, Yingming; Xu, Xin

    2017-01-26

    Three rare-earth aryloxide ion pairs {[L1REOAr](+) /[B(C6 F5 )4 ](-) ; L1=CH3 C(2,6-iPr2 C6 H3 N)CHC(CH3 )(NCH2 CH2 PPh2 ); RE=Sc, Y, Lu; Ar=2,6-tBu2 C6 H3 } were reported that feature rare-earth/phosphorus (RE/P) combinations exhibiting frustrated Lewis pair (FLP)-like 1,4-addition reactions towards conjugated carbonyl substrates (e.g., enone, ynone, and acrylic substrates). Furthermore, these RE/P complexes were found to be effective catalysts for the polymerization of conjugated polar alkene monomers. Mechanistic studies revealed that the rare-earth metal-catalyzed polymerizations were initiated by new FLP-type 1,4-additions rather than traditional and ubiquitous covalent RE-E (E=H, C, N, etc.) bond insertion or single-electron transfer.

  14. Pressure dependence of stabilized Criegee intermediate formation from a sequence of alkenes.

    PubMed

    Drozd, Greg T; Donahue, Neil M

    2011-05-05

    Ozonolysis is a key reaction in atmospheric chemistry, although important details of the behavior of the ozonolysis intermediates are not known. The key intermediate in ozonolysis, the Criegee intermeiate (CI), is known to quickly isomerize, with the favored unimolecular pathway depending on the relative barriers to isomerization. Stabilized Criegee intermediates (SCI), those with energy below any barriers to isomerization, may result from initial formation with low energy or collisional stabilization of high energy CI. Bimolecular reactions of SCI have been proposed to play a role in OH formation and nucleation of new particles, but unimolecular reactions of SCI may well be too fast for these to be significant. We present measurements of the pressure dependence of SCI formation for a set of alkenes utilizing a hexafluoroacetone scavenger. We studied four alkenes (2,3-dimethyl-2-butene (TME), trans-5-decene, cyclohexene, α-pinene) to characterize how size and cyclization (endo vs exo) affect the stability of Criegee intermediates formed in ozonolysis. SCI yields in ozonolysis were measured in a high pressure flow reactor within a range of 30-750 Torr. The linear alkenes show considerable stabilization with trans-5-decene showing 100% stabilization at ∼400 Torr and TME having 65% stabilization at 710 Torr. Extrapolation of the yields for linear alkenes to 0 Torr shows yields significantly above zero, indicating that a fraction of their CI are formed below the barrier to isomerization. CI from endocyclic alkenes show little to no stabilization and appear to have neglible stabilization at 0 Torr. Cyclohexene derived CI showed no stabilization even at 650 Torr, while α-pinene CI had ∼15% stabilization at 740 Torr. Our results show a strong dependence of SCI formation on carbon number; adding just 2 to 3 CI carbons in linear alkenes increases stabilization by a factor of 10. Stabilization for endocyclic alkenes, at atmospheric pressure, begins to occur at a carbon

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

    DOEpatents

    Vajda, Stefan , Pellin, Michael J.; Elam, Jeffrey W [Elmhurst, IL; Marshall, Christopher L [Naperville, IL; Winans, Randall A [Downers Grove, IL; Meiwes-Broer, Karl-Heinz [Roggentin, GR

    2012-04-03

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

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

    DOEpatents

    Vajda, Stefan [Lisle, IL; Pellin, Michael J [Naperville, IL; Elam, Jeffrey W [Elmhurst, IL; Marshall, Christopher L [Naperville, IL; Winans, Randall A [Downers Grove, IL; Meiwes-Broer, Karl-Heinz [Roggentin, GR

    2012-03-27

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

  17. Preparation, characterization, and activity of α-Ti(HPO4)2 supported metallocene catalysts

    NASA Astrophysics Data System (ADS)

    Shi, Yasai; Yuan, Yuan; Xu, Qinghong; Yi, Jianjun

    2016-10-01

    A series of heterogeneous catalysts by loading metallocenes on surface of α-Ti(HPO4)2, a kind of solid acid, has been synthesized. Polymerization of alkenes, including ethylene and propylene, based on participation of the heterogeneous catalysts were studied and the results were compared to metallocenes supported on silica gel, α-Zr(HPO4)2 and clay. Higher catalytic activity, larger polymer molecular weight and narrow distribution of polymer molecular weight were obtained. Acidic strength of the support and its influence to metallocenes were studied to discover intrinsic factors in the polymerizations.

  18. Structural Evolution of a Recoverable Rhodium Hydrogenation Catalyst

    SciTech Connect

    Shaw, Wendy J.; Chen, Yongsheng; Fulton, John L.; Linehan, John C.; Gutowska, Anna; Bitterwolf, Thomas E.

    2008-06-01

    N-isopropylacrylamide was utilized as a ligand to affect recoverability into a rhodium hydrogenation catalyst. The catalyst ligand structure was characterized in situ using NMR, XAFS and IR. Model compounds including glycine, cysteamine and methionine methyl ester were also investigated to aid in the interpretation. The investigation revealed a ligand switch from RNH2 to RSR’ when the catalyst is placed in water as opposed to organic solvents. The catalyst continued to transform with time, creating Rh clusters of up to 4 rhodium atoms, with no Rh metal detected. Over the time and solvents investigated, the catalyst ligands evolve from 1-Cl, 1-NH2, and 2-CO’s to 3-Rh, 1-RSR’ and 1-CO. Upon introduction of the alkene for hydrogenation catalysis, the Rh cluster is lost, favoring instead the interaction with the reactant. The kinetics of the hydrogenation reaction were measured using a novel high pressure flow through NMR system and the catalyst was found to have a TOF of 3000/hr at 25 ºC. This work was supported by the Laboratory Directed Research and Development Program at the Pacific Northwest National Laboratory operated by Battelle for the U.S. Department of Energy.

  19. Catalyst activator

    DOEpatents

    McAdon, Mark H.; Nickias, Peter N.; Marks, Tobin J.; Schwartz, David J.

    2001-01-01

    A catalyst activator particularly adapted for use in the activation of metal complexes of metals of Group 3-10 for polymerization of ethylenically unsaturated polymerizable monomers, especially olefins, comprising two Group 13 metal or metalloid atoms and a ligand structure including at least one bridging group connecting ligands on the two Group 13 metal or metalloid atoms.

  20. Bifunctional Molecular Photoswitches Based on Overcrowded Alkenes for Dynamic Control of Catalytic Activity in Michael Addition Reactions.

    PubMed

    Pizzolato, Stefano F; Collins, Beatrice S L; van Leeuwen, Thomas; Feringa, Ben L

    2016-11-23

    The emerging field of artificial photoswitchable catalysis has recently shown striking examples of functional light-responsive systems allowing for dynamic control of activity and selectivity in organocatalysis and metal-catalysed transformations. While our group has already disclosed systems featuring first generation molecular motors as the switchable central core, a design based on second generation molecular motors is lacking. Here, the syntheses of two bifunctionalised molecular switches based on a photoresponsive tetrasubstituted alkene core are reported. They feature a thiourea substituent as hydrogen-donor moiety in the upper half and a basic dimethylamine group in the lower half. This combination of functional groups offers the possibility for application of these molecules in photoswitchable catalytic processes. The light-responsive central cores were synthesized by a Barton-Kellogg coupling of the prefunctionalized upper and lower halves. Derivatization using Buchwald-Hartwig amination and subsequent introduction of the thiourea substituent afforded the target compounds. Control of catalytic activity in the Michael addition reaction between (E)-3-bromo-β-nitrostyrene and 2,4-pentanedione is achieved upon irradiation of stable-(E) and stable-(Z) isomers of the bifunctional catalyst 1. Both isomers display a decrease in catalytic activity upon irradiation to the metastable state, providing systems with the potential to be applied as ON/OFF catalytic photoswitches.

  1. Pressure-induced metathesis reaction to sequester Cs.

    PubMed

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

    2015-01-06

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

  2. Synthesis of Diketopiperizine Peptide Derivatives by Cross-Metathesis

    DTIC Science & Technology

    2006-05-01

    derivatives using Grubbs’ second generation ruthenium catalyst 13 [(H2IMes)(PCy 3)( Cl )2Ru=CHPh] (1) to couple amino acids to the diketopiperazine...catalyst [(PCy3)2( Cl )2Ru=CHPh] where they employed allyl and homoallylamides. 14 Here we report the product yields and distributions of CM reactions of... Fmoc - kin 0 -ý " N R 2 Mes-N N-Mes = cyclohexyl, CP"’ I PhMes = 2,4,6-trimethylphenyl CI Ph PCY3 1 R - PG O R N 0 PG PG. 0 k~ N 0n PG R Heterodimer

  3. Adsorption of alkenes on acidic zeolites. Theoretical study based on the electron charge density.

    PubMed

    Zalazar, M Fernanda; Duarte, Darío J R; Peruchena, Nélida M

    2009-12-10

    In the present work, experiments on electron density changes in the adsorption process of alkenes on acidic zeolites, in the framework of atoms in molecules theory (AIM), were carried out. Electron densities were obtained at MP2 and B3LYP levels using a 6-31++G(d,p) basis set. This study explores the energetic and the electron density redistributions associated with O-H...pi interactions. The main purpose of this work is to provide an answer to the following questions: (a) Which and how large are the changes induced on the molecular electron distribution by the formation of adsorbed alkenes? (b) Can a reasonable estimate of the adsorption energy of alkenes on the active site of zeolite be solely calculated from an analysis of the electron densities? We have used topological parameters to determine the strength and nature of the interactions in the active site of the zeolite. All the results derived from the electron density analysis show that the stabilization of the adsorbed alkenes follows the order isobutene > trans-2-butene congruent with 1-butene congruent with propene > ethene, reflecting the order of basicity of C=C bonds, i.e., (C(ter)=C(prim)) > (C(sec)=C(sec)) congruent with (C(prim)=C(sec)) > (C(prim)=C(prim)). In addition, we have found a useful set of topological parameters that are good for estimating the adsorption energy in adsorbed alkenes.

  4. Synthesis of Cycloparaphenyleneacetylene via Alkyne Metathesis: C70 Complexation and Copper-Free Triple Click Reaction.

    PubMed

    Lee, Semin; Chénard, Etienne; Gray, Danielle L; Moore, Jeffrey S

    2016-10-10

    Alkyne metathesis provided an efficient macrocyclization route to a cycloparaphenyleneacetylene derivative in high yield. The cavity size was suitably matched for C70 which was tightly bound in an induced-fit fashion. The strain on the alkynyl bonds enabled a copper-free, three-fold azide-alkyne cycloaddi-tion at 50 °C.

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

    PubMed

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

    2011-03-04

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

  6. Bridgehead vicinal diallylation of norbornene derivatives and extension to propellane derivatives via ring-closing metathesis

    PubMed Central

    Gunta, Rama

    2016-01-01

    Summary Here, we report a simple synthetic strategy to the bridgehead vicinal diallylation of norbornene derivatives. These substrates are useful to generate propellanes via ring-closing metathesis. Single-crystal X-ray diffraction analysis of four compounds led to the realization of configurational correction of earlier reported molecules. PMID:27829894

  7. "Click" and Olefin Metathesis Chemistry in Water at Room Temperature Enabled by Biodegradable Micelles.

    PubMed

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

    2013-11-12

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

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

    PubMed Central

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

    2013-01-01

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

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    ERIC Educational Resources Information Center

    Gerlach, Sharon Ruth

    2010-01-01

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

  11. 2005 Nobel Prize in Chemistry: Development of the Olefin Metathesis Method in Organic Synthesis

    ERIC Educational Resources Information Center

    Casey, Charles P.

    2006-01-01

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

  12. Catalyst suppliers consolidate further, offer more catalysts

    SciTech Connect

    Rhodes, A.K.

    1995-10-02

    The list of suppliers of catalysts to the petroleum refining industry has decreased by five since Oil and Gas Journal`s survey of refining catalysts and catalytic additives was last published. Despite the consolidation, the list of catalyst designations has grown to about 950 in this latest survey, compared to 820 listed in 1993. The table divides the catalysts by use and gives data on their primary differentiating characteristics, feedstock, products, form, bulk density,catalyst support, active agents, availability, and manufactures.

  13. Sustainable solid catalyst alkylation of commercial olefins by regeneration with supercritical isobutane

    SciTech Connect

    Daniel M. Ginosar; David N. Thompson; Kyle C. Burch

    2005-12-01

    Supercritical isobutane regeneration of a USY zeolite alkylation catalyst was examined in a continuous, automated reaction / regeneration system. Two feeds were studied; a synthetic isobutane / 2-butene blend, and a commercial refinery isoparaffin / olefin blend. The refinery blend was minimally treated, containing a variety of light olefins, and contaminants, including butadiene, oxygenates and sulfur, which are well known to cause severe catalyst deactivation. Synthetic feed experiments showed that high levels of butene conversion was maintained for more than 200 hours time on stream, and that product quality and catalyst maintenance was relatively stable over the course of the experiment using a 3 hour reaction / 3 hour regeneration cycle. Catalyst activity maintenance was lower when the commercial feed was employed. High levels of alkene conversion were maintained for 78 hours and 192 hours using a 3 hour reaction / 3 hour regeneration cycle and a 2 hour reaction / 2 hour regeneration cycle, respectively.

  14. BCl3-mediated ene reaction of sulfur dioxide and unfunctionalized alkenes.

    PubMed

    Marković, Dean; Volla, Chandra M R; Vogel, Pierre; Varela-Alvarez, Adrián; Sordo, José A

    2010-05-25

    The first ene reactions of SO(2) and unfunctionalized alkenes are reported. Calculations suggest that the endergonic ene reactions of SO(2) with alkenes can be used to generate beta,gamma-unsaturated sulfinyl and sulfonyl compounds. Indeed, in the presence of one equivalent of BCl(3), the unstable sulfinic acid form stable sulfinic acid.BCl(3) complexes that can be reacted in situ with NCS to generate corresponding sulfonyl chlorides, or with a base to generate corresponding sulfinates. The latter can be reacted with electrophiles to generate sulfones, or with silyl chloride to form beta,gamma-unsaturated silyl sulfinates. The sulfinic acid.BCl(3) complexes can be reacted with ethers that act as oxygen nucleophiles to produce corresponding sulfinic esters. Thus one-pot, three-component synthesis of beta,gamma-unsaturated sulfonamides, sulfinyl esters and sulfones have been developed starting from alkenes and sulfur dioxide (reagent and solvent).

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

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

    PubMed Central

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

    2016-01-01

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

  17. Stereoselective synthesis of imidazolidin-2-ones via Pd-catalyzed alkene carboamination. Scope and limitations

    PubMed Central

    Fritz, Jonathan A.; Wolfe, John P.

    2008-01-01

    A method for the synthesis of imidazolidin-2-ones from N-allylureas and aryl or alkenyl bromides via Pd-catalyzed carboamination reactions is described. The N-allylurea precursors are prepared in one step from readily available allylic amines and isocyanates, and the Pd-catalyzed reactions effect the formation of a C–C bond, a C–N bond, and up to two stereocenters in a single step. Good diastereoselectivities are obtained for the conversion of substrates bearing allylic substituents to 4,5-disubstituted imidazolidin-2-ones, and excellent selectivity for the generation of products resulting from syn-addition across the alkene is observed when substrates derived from cyclic alkenes or E-1,2-disubstituted alkenes are employed. A brief discussion of reaction mechanism and product stereochemistry is presented. PMID:19122758

  18. Hydrocracking catalyst

    SciTech Connect

    Arias, B.; Galiasso, R.; Kum, H.

    1985-02-12

    The invention relates to a particular method for the preparation of a hydrocracking catalyst, using a high iron content bauxite as a basis. This bauxite is ground and screened to a specific size and mixed with three types of additives: a promoter additive of the P, Mo, Co, Ni, W type. A hardener additive of the phosphoric acid type, ammonium phosphate. And a lubricant and pore-generating additive of the polyvinyl alcohol, polyethylene-glycol, starch type. The particularity consists in that the three additives are added simultaneously during the extrusion of the sample. That way, a particular surface composition is obtained which allows for the activity of the catalyst. Extruded products are obtained in sizes of 1/8, 1/16, and 1/32'' and submitted to drying and calcination programs for their activation. The obtained catalyst offers a good mechanical strength, a high content in macropores and a high activity, specifically for the hydrocracking of heavy Venezuelan crudes or residues.

  19. Highly enantioselective and anti-diastereoselective catalytic intermolecular glyoxylate-ene reactions: effect of the geometrical isomers of alkenes.

    PubMed

    Zhang, Xiang; Wang, Min; Ding, Ran; Xu, Yun-He; Loh, Teck-Peng

    2015-06-05

    An efficient method for the synthesis of homoallylic alcohols with high enantioselectivities and anti-diastereoselectivities via an In(III)-catalyzed intermolecular glyoxylate-ene reaction has been developed. The geometrical isomers of alkenes were shown to have different reactivities. Only the isomers of the alkenes having a proton β-cis to the substituent reacted in this catalytic system.

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

    ERIC Educational Resources Information Center

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

    2007-01-01

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

  1. DualPhos: a versatile, chemoselective reagent for two-carbon aldehyde to latent (E)-alkenal homologation and application in the total synthesis of phomolide G

    PubMed Central

    McLeod, David

    2016-01-01

    Advances on the use of the 2-pinacolacetal-tripropylphosphonium salt DualPhos as a general reagent for the two-carbon aldehyde to alkenal homologation and a chemoselective iron (III) chloride mediated deprotection are described. The strategy allows isolation of the latent alkenal intermediates or direct hydrolysis to (E)-alkenals. The robust chemical stability of the latent alkenals is demonstrated in a total synthesis of the macrolactone phomolide G. PMID:28018615

  2. Polyethylene-bound rhodium(I) hydrogenation catalysts

    SciTech Connect

    Bergbreiter, D.E.; Chandran, R.

    1987-01-07

    Homogeneous, recoverable hydrogenation catalysts were prepared with use of functionalized ethylene oligomers as ligands. Phosphine groups were introduced onto ethylene oligomers following anionic oligomerization of ethylene. The product polyethylenediphenylphosphine ligands were then exchanged with triphenylphosphine or ethylene ligands to prepare ethylene oligomer ligated rhodium(I) complexes. These Rh(I) complexes had the solubility of polyethylene and dissolved at 90-110/sup 0/C in hydrocarbon solvents but quantitatively precipitated at 25/sup 0/C. Less than 0.1% of the charged rhodium was lost in each dissolution precipitation cycle. The rhodium(I) complexes so prepared were shown to have about 80% of the activity of tris(triphenylphosphine)rhodium chloride in hydrogenation of various alkenes including 1-octene, ..delta../sup 2/-cholestene, cyclooctene, cyclododecene, styrene, and ..cap alpha..-methylstyrene. /sup 31/P NMR spectroscopy and reactivity studies were used to characterize these catalysts.

  3. Fe(III)/NaBH4-Mediated Free Radical Hydrofluorination of Unactivated Alkenes

    PubMed Central

    Barker, Timothy J.

    2012-01-01

    A powerful Fe(III)/NaBH4-mediated free radical hydrofluorination of unactivated alkenes is disclosed using Selectfluor as a source of fluorine and resulting in exclusive Markovnikov addition. In contrast to the traditional and unmanageable free radical hydrofluorination of alkenes, the Fe(III)/NaBH4-mediated reaction is conducted under exceptionally mild reaction conditions (0 °C, 5 min, CH3CN/H2O). The reaction can be conducted open to the air and with water as a cosolvent and demonstrates an outstanding substrate scope and functional group tolerance. PMID:22860624

  4. Cascade multicomponent synthesis of indoles, pyrazoles, and pyridazinones by functionalization of alkenes.

    PubMed

    Matcha, Kiran; Antonchick, Andrey P

    2014-10-27

    The development of multicomponent reactions for indole synthesis is demanding and has hardly been explored. The present study describes the development of a novel multicomponent, cascade approach for indole synthesis. Various substituted indole derivatives were obtained from simple reagents, such as unfunctionalized alkenes, diazonium salts, and sodium triflinate, by using an established straightforward and regioselective method. The method is based on the radical trifluoromethylation of alkenes as an entry into Fischer indole synthesis. Besides indole synthesis, the application of the multicomponent cascade reaction to the synthesis of pyrazoles and pyridazinones is described.

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

    PubMed Central

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

    2015-01-01

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

  6. Stereoselective Synthesis of Saturated Heterocycles via Pd-Catalyzed Alkene Carboetherification and Carboamination Reactions

    PubMed Central

    Wolfe, John P.

    2009-01-01

    The development of Pd-catalyzed carboetherification and carboamination reactions between aryl/alkenyl halides and alkenes bearing pendant heteroatoms is described. These transformations effect the stereoselective construction of useful heterocycles such as tetrahydrofurans, pyrrolidines, imidazolidin-2-ones, isoxazolidines, and piperazines. The scope, limitations, and applications of these reactions are presented, and current stereochemical models are described. The mechanism of product formation, which involves an unusual intramolecular syn-insertion of an alkene into a Pd-Heteroatom bond is also discussed in detail. PMID:19183704

  7. Aerobic, Palladium-Catalyzed Dioxygenation of Alkenes Enabled by Catalytic Nitrite**

    PubMed Central

    Wickens, Zachary K.; Guzmán, Pablo E.; Grubbs, Robert H.

    2014-01-01

    Catalytic nitrite was found to enable carbon-oxygen bond-forming reductive elimination from unstable alkyl palladium intermediates, providing dioxygenated products from alkenes. A variety of functional groups are tolerated and high yields (up to 94%) are observed with many substrates, including a multi-gram scale reaction. Nitrogen dioxide, which could form from nitrite under the reaction conditions, was shown to be kinetically competent in the dioxygenation of alkenes. Furthermore, the reductive elimination event was probed with 18 O-labeling experiments, which demonstrated that both oxygen atoms in the difunctionalized products are derived from one molecule of acetic acid. PMID:25376666

  8. Stable metal–organic framework-supported niobium catalysts

    SciTech Connect

    Ahn, Sol; Thornburg, Nicholas E.; Li, Zhanyong; Wang, Timothy C.; Gallington, Leighanne C.; Chapman, Karena W.; Notestein, Justin M.; Hupp, Joseph T.; Farha, Omar K.

    2016-10-31

    In this study by developing structurally well-defined, supported oxide catalysts remains a significant challenge. Here, we report the grafting of Nb(V) oxide sites onto the nodes of the Zr-based metal organic framework (MOF) NU-1000 as a stable, well-defined catalyst support. Nb(V) oxide was deposited with loadings up to 1.6 mmol/g via two post-synthetic methods: atomic layer deposition in a MOF (AIM), and solution-phase grafting in a MOF (SIM). Difference envelope density (DED) measurements indicated that the two synthetic methods resulted in different local structures of the Nb(V) ions within NU-1000. Despite their high Nb(V) loadings, which were equivalent to >60% surface coverage, nearly all Nb(V) sites of the MOF-supported catalysts were active sites for alkene epoxidation, as confirmed by phenylphosphonic acid titration. The MOF-supported catalysts were more selective than the control Nb-ZrO2 catalyst for cyclohexene epoxidation with aqueous H2O2, and were far more active on a gravimetric basis.

  9. Stable metal–organic framework-supported niobium catalysts

    DOE PAGES

    Ahn, Sol; Thornburg, Nicholas E.; Li, Zhanyong; ...

    2016-10-31

    In this study by developing structurally well-defined, supported oxide catalysts remains a significant challenge. Here, we report the grafting of Nb(V) oxide sites onto the nodes of the Zr-based metal organic framework (MOF) NU-1000 as a stable, well-defined catalyst support. Nb(V) oxide was deposited with loadings up to 1.6 mmol/g via two post-synthetic methods: atomic layer deposition in a MOF (AIM), and solution-phase grafting in a MOF (SIM). Difference envelope density (DED) measurements indicated that the two synthetic methods resulted in different local structures of the Nb(V) ions within NU-1000. Despite their high Nb(V) loadings, which were equivalent to >60%more » surface coverage, nearly all Nb(V) sites of the MOF-supported catalysts were active sites for alkene epoxidation, as confirmed by phenylphosphonic acid titration. The MOF-supported catalysts were more selective than the control Nb-ZrO2 catalyst for cyclohexene epoxidation with aqueous H2O2, and were far more active on a gravimetric basis.« less

  10. Reaction of Chlorosulfonyl Isocyanate (CSI) with Fluorosubstituted Alkenes: Evidence of a Concerted Pathway for Reaction of CSI with Fluorosubstituted Alkenes (Preprint)

    DTIC Science & Technology

    2010-06-01

    ABSTRACT Concerted reactions are indicated for the electrophilic addition of chlorosulfonyl isocyanate with monofluoroalkenes. A vinyl fluorine atom on...SO2Cl R F O ‡ N SO2Cl F R O Abstract: Concerted reactions are indicated for the electrophilic addition of chlorosulfonyl isocyanate with...monofluoroalkenes. A vinyl fluorine atom on an alkene raises the energy of a step-wise transition state more than the energy of the competing concerted

  11. Cracking catalyst

    SciTech Connect

    Otterstedt, J. E. A.; Jaras, S. G.; Pudas, R.; Upson, L. L.

    1985-05-07

    A cracking catalyst having good resistance to metal poisoning has at least two particle fractions of different particle sizes, the cracking catalyzing zeolite material being concentrated to the coarser particle size fractions, and the finer particle size fractions being formed from material having relatively lower or no or insignificant cracking catalyzing activity. The particles of the finer particle size fractions have a matrix of kaolin and amorphous alumina--silica and may contain for example, an SO /SUB x/ eliminating additive such as Al/sub 2/O/sub 3/, CaO and/or MgO. The coarser particle size fractions having cracking catalyzing effect have a mean particle size of from 80 to 125 ..mu..m and the finer particle size fractions a mean particle size of from 30 to 75 ..mu..m. The coarser particle size fractions have a zeolite content of at least 20 weight % and may have a zeolite content of up to 100 weight %, the remainder consisting essentially of material which has relatively lower or no or insignificant cracking-catalyzing activity and which consists of kaolin and amorphous alumina-silica. The catalyst mass as a whole may have a zeolite content of up to 50 weight %.

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

    PubMed Central

    Wang, Hao; Houk, K. N.

    2013-01-01

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

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

    PubMed Central

    Strom, Alexandra E.

    2013-01-01

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

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

    PubMed Central

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

    2016-01-01

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

  15. Copper-mediated stereospecific C-H oxidative sulfenylation of terminal alkenes with disulfides.

    PubMed

    Tu, Hai-Yong; Hu, Bo-Lun; Deng, Chen-Liang; Zhang, Xing-Guo

    2015-11-04

    A copper and iodine-mediated C-H oxidative sulfenylation of olefins with diaryl disulfides has been developed for the stereospecific synthesis of vinyl thioether. With the combination of Cu(OTf)2 and I2, a variety of terminal alkenes underwent oxidative coupling reaction with various diaryl disulfides successfully to afford the corresponding E-vinyl sulfides in moderate to good yields.

  16. OH yields in the gas-phase reactions of ozone with alkenes

    SciTech Connect

    Rickard, A.R.; Johnson, D.; McGill, C.D.; Marston, G.

    1999-09-23

    Hydroxyl radical yields are reported for the gas-phase ozonolyses of a range of alkenes. 1,3,5-Trimethylbenzene was employed as an OH tracer, and the diminution in its concentration was used to calculate OH yields by both a simple analytical kinetic expression and a numerically integrated model. The following OH yields were obtained, relative to alkene consumed: ethene (0.14), propene (0.32), 2-methylpropene (0.60), 2,3-dimethyl-2-butene (0.89), isoprene (0.44), {beta}-pinene (0.24), and {alpha}-pinene (0.83). A structure activity relationship (SAR) is presented for the estimation of OH yields based on structural moieties and reaction branching ratios. Reaction stoichiometries ({Delta}[alkene]/{Delta}[ozone]) are also reported, along with primary carbonyl yields measured in the presence and absence of excess SO{sub 2}, both under OH-free conditions. Reaction stoichiometries are shown to be correlated with alkene OH yields, and the mechanistic implications of this observation are discussed. The fractional increase in primary carbonyl yield in the presence of excess SO{sub 2} is shown to be inversely related to the OH yield and is interpreted as a measure of the fraction of the vibrationally excited Criegee intermediate that is stabilized in air at a pressure of 1 atm.

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

    EPA Science Inventory

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

  18. Structure and Biochemical Properties of the Alkene Producing Cytochrome P450 OleTJE (CYP152L1) from the Jeotgalicoccus sp. 8456 Bacterium*

    PubMed Central

    Belcher, James; McLean, Kirsty J.; Matthews, Sarah; Woodward, Laura S.; Fisher, Karl; Rigby, Stephen E. J.; Nelson, David R.; Potts, Donna; Baynham, Michael T.; Parker, David A.; Leys, David; Munro, Andrew W.

    2014-01-01

    The production of hydrocarbons in nature has been documented for only a limited set of organisms, with many of the molecular components underpinning these processes only recently identified. There is an obvious scope for application of these catalysts and engineered variants thereof in the future production of biofuels. Here we present biochemical characterization and crystal structures of a cytochrome P450 fatty acid peroxygenase: the terminal alkene forming OleTJE (CYP152L1) from Jeotgalicoccus sp. 8456. OleTJE is stabilized at high ionic strength, but aggregation and precipitation of OleTJE in low salt buffer can be turned to advantage for purification, because resolubilized OleTJE is fully active and extensively dissociated from lipids. OleTJE binds avidly to a range of long chain fatty acids, and structures of both ligand-free and arachidic acid-bound OleTJE reveal that the P450 active site is preformed for fatty acid binding. OleTJE heme iron has an unusually positive redox potential (−103 mV versus normal hydrogen electrode), which is not significantly affected by substrate binding, despite extensive conversion of the heme iron to a high spin ferric state. Terminal alkenes are produced from a range of saturated fatty acids (C12–C20), and stopped-flow spectroscopy indicates a rapid reaction between peroxide and fatty acid-bound OleTJE (167 s−1 at 200 μm H2O2). Surprisingly, the active site is highly similar in structure to the related P450BSβ, which catalyzes hydroxylation of fatty acids as opposed to decarboxylation. Our data provide new insights into structural and mechanistic properties of a robust P450 with potential industrial applications. PMID:24443585

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-01-13

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

  1. Self-selection in olefin cross-metathesis: the effect of remote functionality.

    PubMed

    McNaughton, Brian R; Bucholtz, Kevin M; Camaaño-Moure, Ana; Miller, Benjamin L

    2005-02-17

    Olefin cross-metathesis (CM) is potentially an attractive method for generating dynamic combinatorial libraries (DCLs). In order for the CM reaction to be useful for DCL production, the course of the reaction and product distribution must be relatively insensitive to functionality remote from the reacting centers. We report on the CM of a series of allyl- and homoallylamides that are strongly dependent on remote functionality. This includes an unusual example of a cis-selective CM. [Reaction: see text

  2. Pd-N-heterocyclic carbene catalyzed synthesis of piperidine alkene-alkaloids and their anti-cancer evaluation.

    PubMed

    Kankala, Shravankumar; Kankala, Ranjith Kumar; Balaboina, Ramesh; Thirukovela, Narasimha Swamy; Vadde, Ravinder; Vasam, Chandra Sekhar

    2014-02-15

    A facile synthesis of piperidine alkene-alkaloids including natural (+)-Caulophyllumine B in high yields has been developed by Heck cross-coupling reaction catalyzed by simple in situ formed palladium-N-heterocyclic carbenes (Pd-NHCs). Formation of Pd(0) nanoparticles has been noticed during the reaction course. The synthesized piperidine alkene-alkaloids were evaluated for in vitro anti-cancer activity against a panel of human tumor cell lines of lung, breast and ovarian. Several of these piperidine alkene-alkaloids were found to possess highest growth inhibition activity than the standard drug cisplatin and support the concept to modulate drug receptor interaction.

  3. Direct and selective production of propene from bio-ethanol on Sc-loaded IN2O3 catalysts.

    PubMed

    Iwamoto, Masakazu; Mizuno, Shouta; Tanaka, Masashi

    2013-05-27

    Propene, one of key building blocks for manufacturing plastics and chemicals, could be directly and stably produced from ethanol in good yields. The conversion degree of ethanol to propene reached approximately 60 mol% by using a 3 atom% scandium-loaded indium oxide catalyst at 823 K in the presence of water and hydrogen. The introduction of Sc prevented the reduction of In2O3 to In metal during the reaction, and that of water decreased the coke formation. Both additions resulted in longer lifetimes of the catalysts. The hydrogen addition increased the conversion of acetone to propene. The reaction pathways are also suggested on the basis of the product distributions and the pulse experiments, ethanol→acetaldehyde→acetone→propene, which is quite different from the shape-selective catalysis on zeolites and the dimerization-metathesis of ethene on nickel ion-loaded silica catalysts.

  4. STUDY OF SOLVENT AND CATALYST INTERACTIONS IN DIRECT COAL LIQUEFACTION

    SciTech Connect

    Michael T. Klein; William H. Calkins; Jasna Tomic

    2000-10-04

    To provide a better understanding of the roles of a solid catalyst and the solvent in Direct Coal Liquefaction, a small reactor was equipped with a porous-walled basket which was permeable to the solvent but was not permeable to the coal or solid catalyst. With this equipment and a high volatile bituminous coal it was found that direct contact between the catalyst in the basket and the coal outside the basket is not required for catalyzed coal liquefaction. The character of the solvent in this system makes a significant difference in the conversion of the coal, the better solvents being strong donor solvents. Because of the extensive use of thermogravimetric analysis in this laboratory, it was noted that the peak temperature for volatiles evolution from coal was a reliable measure of coal rank. Because of this observation, a variety of coals of a range of ranks was investigated. It was shown in this work that measuring the peak temperature for volatiles evolution was a quite precise indicator of rank and correlated closely with the rank value obtained by measuring vitrinite reflectance, a more difficult measurement to make. This prompted the desire to know the composition of the volatile material evolved as a function of coal rank. This was then measured by coupling a TGA to a mass spectrometer using laser activation and photoionization detection TG-PI-MS. The predominant species in volatiles of low rank coal turned out to be phenols with some alkenes. As the rank increases, the relative amounts of alkene and aromatic hydrocarbons increases and the oxygenated species decrease. It was shown that these volatiles were actually pyrolytic products and not volatilization products of the coal. Solvent extraction experiments coupled with Thermogravimetric-photoionization-mass spectrometry (TG-PI-MS) indicated that the low boiling and more extractable material are essentially similar in chemical types to the non-extractable portions but apparently higher molecular weight

  5. STUDY OF SOLVENT AND CATALYST INTERACTIONS IN DIRECT COAL LIQUEFACTION

    SciTech Connect

    Michael T. Klein

    2000-01-01

    There are several aspects of the Direct Coal Liquefaction process which are not fully understood and which if better understood might lead to improved yields and conversions. Among these questions are the roles of the catalyst and the solvent. While the solvent is known to act by transfer of hydrogen atoms to the free radicals formed by thermal breakdown of the coal in an uncatalyzed system, in the presence of a solid catalyst as is now currently practiced, the yields and conversions are higher than in an uncatalyzed system. The role of the catalyst in this case is not completely understood. DOE has funded many projects to produce ultrafine and more active catalysts in the expectation that better contact between catalyst and coal might result. This approach has met with limited success probably because mass transfer between two solids in a fluid medium i.e. the catalyst and the coal, is very poor. It is to develop an understanding of the role of the catalyst and solvent in Direct Liquefaction that this project was initiated. Specifically it was of interest to know whether direct contact between the coal and the catalyst was important. By separating the solid catalyst in a stainless steel basket permeable to the solvent but not the coal in the liquefaction reactor, it was shown that the catalyst still maintains a catalytic effect on the liquefaction process. There is apparently transfer of hydrogen atoms from the catalyst through the basket wall to the coal via the solvent. Strong hydrogen donor solvents appear to be more effective in this respect than weak hydrogen donors. It therefore appears that intimate contact between catalyst and coal is not a requirement, and that the role of the catalyst may be to restore the hydrogen donor strength to the solvent as the reaction proceeds. A range of solvents of varying hydrogen donor strength was investigated. Because of the extensive use of thermogravimetric analysis in this laboratory in was noted that the peak

  6. Electrochemical catalyst recovery method

    DOEpatents

    Silva, Laura J.; Bray, Lane A.

    1995-01-01

    A method of recovering catalyst material from latent catalyst material solids includes: a) combining latent catalyst material solids with a liquid acid anolyte solution and a redox material which is soluble in the acid anolyte solution to form a mixture; b) electrochemically oxidizing the redox material within the mixture into a dissolved oxidant, the oxidant having a potential for oxidation which is effectively higher than that of the latent catalyst material; c) reacting the oxidant with the latent catalyst material to oxidize the latent catalyst material into at least one oxidized catalyst species which is soluble within the mixture and to reduce the oxidant back into dissolved redox material; and d) recovering catalyst material from the oxidized catalyst species of the mixture. The invention is expected to be particularly useful in recovering spent catalyst material from petroleum hydroprocessing reaction waste products having adhered sulfides, carbon, hydrocarbons, and undesired metals, and as well as in other industrial applications.

  7. Electrochemical catalyst recovery method

    DOEpatents

    Silva, L.J.; Bray, L.A.

    1995-05-30

    A method of recovering catalyst material from latent catalyst material solids includes: (a) combining latent catalyst material solids with a liquid acid anolyte solution and a redox material which is soluble in the acid anolyte solution to form a mixture; (b) electrochemically oxidizing the redox material within the mixture into a dissolved oxidant, the oxidant having a potential for oxidation which is effectively higher than that of the latent catalyst material; (c) reacting the oxidant with the latent catalyst material to oxidize the latent catalyst material into at least one oxidized catalyst species which is soluble within the mixture and to reduce the oxidant back into dissolved redox material; and (d) recovering catalyst material from the oxidized catalyst species of the mixture. The invention is expected to be particularly useful in recovering spent catalyst material from petroleum hydroprocessing reaction waste products having adhered sulfides, carbon, hydrocarbons, and undesired metals, and as well as in other industrial applications. 3 figs.

  8. Kinetic resolution of planar-chiral 1,2-disubstituted ferrocenes by molybdenum-catalyzed asymmetric intraannular ring-closing metathesis.

    PubMed

    Ogasawara, Masamichi; Arae, Sachie; Watanabe, Susumu; Nakajima, Kiyohiko; Takahashi, Tamotsu

    2013-03-25

    Planar chirality: Ring-closing metathesis of 1,2-diallylmetallocenes afforded the corresponding 4,7-dihydroindenyl species in high yields. The metallocenes are planar chiral with two different allylic substituents, and kinetic resolution of the racemic 1,2-diallylmetallocene derivatives was realized by molybdenum-catalyzed asymmetric ring-closing metathesis with excellent enantioselectivity (see scheme).

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  10. Iron(III)/NaBH4-Mediated Additions to Unactivated Alkenes: Synthesis of Novel 20′-Vinblastine Analogues

    PubMed Central

    Leggans, Erick K.; Barker, Timothy J.; Duncan, Katharine K.; Boger, Dale L.

    2012-01-01

    An Fe(III)/NaBH4-mediated reaction for the functionalization of unactivated alkenes is described defining the alkene substrate scope, establishing the exclusive Markovnikov addition, exploring a range of free radical traps, examining the Fe(III) salt and initiating hydride source, introducing H2O-cosolvent mixtures, and exploring catalytic variants. Its use led to the preparation of a novel, potent and previously inaccessible C20′-vinblastine analogue. PMID:22369097

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

    PubMed

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

    2014-06-01

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

  12. Hyperfine frequency shift and Zeeman relaxation in alkali-metal-vapor cells with antirelaxation alkene coating

    NASA Astrophysics Data System (ADS)

    Corsini, Eric P.; Karaulanov, Todor; Balabas, Mikhail; Budker, Dmitry

    2013-02-01

    An alkene-based antirelaxation coating for alkali-metal vapor cells exhibiting Zeeman relaxation times up to 77 s was recently identified by Balabas The long relaxation times, two orders of magnitude longer than in paraffin- (alkane-) coated cells, motivate revisiting the question of what the mechanism is underlying wall-collision-induced relaxation and renew interest in applications of alkali-metal vapor cells to secondary frequency standards. We measure the width and frequency shift of the ground-state hyperfine mF=0→mF'=0 transition (clock resonance) in vapor cells with 85Rb and 87Rb atoms, with an alkene antirelaxation coating. We find that the frequency shift is slightly larger than for paraffin-coated cells and that the Zeeman linewidth scales linearly with the hyperfine frequency shift.

  13. Development of Novel Alkene Oxindole Derivatives As Orally Efficacious AMP-Activated Protein Kinase Activators

    PubMed Central

    2013-01-01

    Adenosine 5′-monophosphate-activated protein kinase (AMPK) is emerging as a promising drug target for its regulatory function in both glucose and lipid metabolism. Compound PT1 (5) was originally identified from high throughput screening as a small molecule activator of AMPK through the antagonization of the autoinhibition in α subunits. In order to enhance its potency at AMPK and bioavailability, structure–activity relationship studies have been performed and resulted in a novel series of AMPK activators based on an alkene oxindole scaffold. Following their evaluation in pharmacological AMPK activation assays, lead compound 24 was identified to possess improved potency as well as favorable pharmacokinetic profile. In the diet-induced obesity (DIO) mouse model, compound 24 was found to improve glucose tolerance and alleviate insulin resistance. The in vitro and in vivo data for these alkene oxindoles warrant further studies for their potential therapeutic medications in metabolic associated diseases. PMID:24900695

  14. Unsymmetrical E-Alkenes from the Stereoselective Reductive Coupling of Two Aldehydes.

    PubMed

    Esfandiarfard, Keyhan; Mai, Juri; Ott, Sascha

    2017-03-01

    The unprecedented formation of unsymmetrical alkenes from the intermolecular reductive coupling of two different aldehydes is described. In contrast to the McMurry reaction which affords statistical product mixtures, selectivity in the reported procedure is achieved by a sequential ionic mechanism in which a first aldehyde is reacted with a phosphanylphosphonate to afford a phosphaalkene intermediate which, upon activation by hydroxide, reacts with a second aldehyde to the unsymmetrical E-alkenes. The described reaction is free of transition metals and proceeds under ambient temperature within minutes in good to excellent overall yields. It is a new methodology to use feedstock aldehydes for the direct production of C═C double bond-containing products and may impact how chemists think of multistep synthetic sequences in the future.

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

    PubMed

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

    2015-07-20

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

  16. Microwave-assisted formation of organic monolayers from 1-alkenes on silicon carbide.

    PubMed

    van den Berg, Sebastiaan A; Alonso, Jose Maria; Wadhwa, Kuldeep; Franssen, Maurice C R; Wennekes, Tom; Zuilhof, Han

    2014-09-09

    The rate of formation of covalently linked organic monolayers on HF-etched silicon carbide (SiC) is greatly increased by microwave irradiation. Upon microwave treatment for 60 min at 100 °C (60 W), 1-alkenes yield densely packed, covalently attached monolayers on flat SiC surfaces, a process that typically takes 16 h at 130 °C under thermal conditions. This approach was extended to SiC microparticles. The monolayers were characterized by X-ray photoelectron spectroscopy and static water contact angle measurements. The microwave-assisted reaction is compatible with terminal functionalities such as alkenes that enable subsequent versatile "click" chemistry reactions, further broadening the range and applicability of chemically modified SiC surfaces.

  17. Postpolymerization Modifications of Alkene-Functional Polycarbonates for the Development of Advanced Materials Biomaterials.

    PubMed

    Thomas, Anthony W; Dove, Andrew P

    2016-12-01

    Functional aliphatic polycarbonates have attracted significant attention as materials for use as biomedical polymers in recent years. The incorporation of pendent functionality offers a facile method of modifying materials postpolymerization, thus enabling functionalities not compatible with ring-opening polymerization (ROP) to be introduced into the polymer. In particular, polycarbonates bearing alkene-terminated functional groups have generated considerable interest as a result of their ease of synthesis, and the wide range of materials that can be obtained by performing simple postpolymerization modifications on this functionality, for example, through radical thiol-ene addition, Michael addition, and epoxidation reactions. This review presents an in-depth appraisal of the methods used to modify alkene-functional polycarbonates postpolymerization, and the diversity of practical applications for which these materials and their derivatives have been used.

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

    PubMed Central

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

    2016-01-01

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

  19. Copper-catalyzed intermolecular carboetherification of unactivated alkenes by alkyl nitriles and alcohols.

    PubMed

    Chatalova-Sazepin, Claire; Wang, Qian; Sammis, Glenn M; Zhu, Jieping

    2015-04-27

    A three-component carboetherification of unactivated alkenes has been developed allowing the rapid building of complexity from simple starting materials. A wide range of α-substituted styrenes underwent smooth reactions with unactivated alkyl nitriles and alcohols to afford γ-alkoxy alkyl nitriles with concomitant generation of a quaternary carbon center. A radical clock experiment provided clear-cut evidence that the reaction proceeds through a tertiary alkyl radical intermediate.

  20. Carbonyl products of the gas phase reaction of ozone with symmetrical alkenes

    SciTech Connect

    Grosjean, E.; Grosjean, D.

    1996-06-01

    In this study, carbonyl products have been identified and their yields measured in experiments involving the gas phase reaction of ozone with the eight symmetrical alkenes ethylene, cis-3-hexene, cis-4-octene, trans-4-octene, cis-5-decene, trans-5-decene, trans-2, 5-dimethyl-3-hexene, and (cis+trans)-3,4-dimethyl-3-hexene in purified air. Sufficient cyclohexane was added to scavenge the hydroxyl radical (OH) in order to minimize the reaction of OH with the alkenes and with their carbonyl products. Formation yields (carbonyl formed/ozone reacted) of primary carbonyls were close to the value of 1.0 that is consistent with simple reaction mechanism. Carbonyls other than the primary carbonyls R{sub 1}COR{sub 2} were identified as products. Their formation is discussed in terms of subsequent reactions of the R{sub 1}R{sub 2}COO biradicals CH{sub 3}CH{sub 2}CHOO, CH{sub 3}(CH{sub 2}){sub 2}CHOO, CH{sub 3}(CH{sub 2}){sub 3}CHOO, (CH{sub 3}){sub 2}CHCHOO, and C{sub 2}H{sub 5}C(CH{sub 3})OO. Similarities and differences are discussed for cis and trans isomers and for biradical reactions as a function of the nature and number of the substituents. The results are compared to those for the biradicals H{sub 2}COO, CH{sub 3}CHOO, and (CH{sub 3}){sub 2}COO from simpler symmetrical alkenes and contribute to a better understanding of the ozone-alkene reaction under atmospheric conditions. 51 refs., 1 fig., 3 tabs.

  1. Analysis of using binary cryogenic mixtures containing nitrogen and alkanes or alkenes in cryocoolers

    NASA Astrophysics Data System (ADS)

    Xu, M.; He, Y.; Chen, Z.

    This paper describes the working mechanism of binary cryogenic mixtures containing nitrogen and alkanes or alkenes. The Peng-Robinson equation of state is used to calculate the mixed free enthalpy of these mixtures and a method to calculate the mutual solubility is also suggested. Finally, the vapour-liquid, liquid-liquid and vapourliquid-liquid equilibria of these mixtures are analysed. Therefore, an effective method to predict the characteristics of new kinds of binary cryogenic substances is provided in this paper.

  2. The mechanism of alkene elimination from protonated toluenesulphonamides generated by electrospray ionisation.

    PubMed

    Saidykhan, Amie; Ebert, Jenessa; Martin, William H C; Gallagher, Richard T; Bowen, Richard D

    2016-01-01

    The positive ion electrospray mass spectra of a range of sulphonamides of general structure CH3C6H4SO2NHR1 [R1 = CnH2n(+1) (n = 1-7), CnH2n-1 (n = 3, 4), C6H5, C6H5CH2 and C6H5CH(CH3)] and CH3C6H4SO2NR1R(2) [R(1), R(2) = CnH2n+1 (n = 1-8)] are reported and discussed. The protonated sulphonamides derived from saturated primary and secondary aliphatic amines generally fragment to only a limited extent unless energised by collision. Two general fragmentations are observed: firstly, elimination of an alkene, CnH2n, obtained by hydrogen abstraction from one of the CnH2n+1 alkyl groups on nitrogen; secondly, cleavage to form CH3C6H4SO2+. The mechanism by which an alkene is lost has been probed by studying the variation of the intensity of the [M + H - CnH2n](+) signal with the structure of the alkyl substituent(s) on nitrogen and by monitoring the competition between the loss of different alkenes from protonated unsymmetrical sulphonamides in which two different alkyl groups are attached to nitrogen. This fragmentation is favoured by branching of the alkyl group at the carbon atom directly attached to nitrogen, thus suggesting that it involves a mechanism in which the stability of the cation obtained by stretching the bond connecting the nitrogen atom to the alkyl group is critical. This interpretation also explains the competition between alkene elimination and cleavage to form CH3C6H4SO2(+) (and, in some cases, cleavage to form C6H5CH2(+) or [C6H5CHCH3](+)).

  3. Palladium-catalyzed vinylation of aminals with simple alkenes: a new strategy to construct allylamines.

    PubMed

    Xie, Yinjun; Hu, Jianhua; Wang, Yanyu; Xia, Chungu; Huang, Hanmin

    2012-12-26

    A novel, highly selective palladium-catalyzed vinylation reaction for the direct synthesis of allylic amines from styrenes and aminals has been established. The utility of this method was also demonstrated by the rapid synthesis of cinnarizine from aldehydes, amines, and simple alkenes in one-pot manner. Mechanistic studies suggested that the reaction proceeds through a valuable cyclometalated Pd(II) complex generated by the oxidative addition of aminal to a Pd(0) species.

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

    PubMed

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

    2013-11-27

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

  5. Catalytic Determinants of Alkene Production by the Cytochrome P450 Peroxygenase OleTJE*

    PubMed Central

    Matthews, Sarah; Belcher, James D.; Tee, Kang Lan; Girvan, Hazel M.; McLean, Kirsty J.; Rigby, Stephen E. J.; Levy, Colin W.; Leys, David; Parker, David A.; Blankley, Richard T.; Munro, Andrew W.

    2017-01-01

    The Jeotgalicoccus sp. peroxygenase cytochrome P450 OleTJE (CYP152L1) is a hydrogen peroxide-driven oxidase that catalyzes oxidative decarboxylation of fatty acids, producing terminal alkenes with applications as fine chemicals and biofuels. Understanding mechanisms that favor decarboxylation over fatty acid hydroxylation in OleTJE could enable protein engineering to improve catalysis or to introduce decarboxylation activity into P450s with different substrate preferences. In this manuscript, we have focused on OleTJE active site residues Phe79, His85, and Arg245 to interrogate their roles in substrate binding and catalytic activity. His85 is a potential proton donor to reactive iron-oxo species during substrate decarboxylation. The H85Q mutant substitutes a glutamine found in several peroxygenases that favor fatty acid hydroxylation. H85Q OleTJE still favors alkene production, suggesting alternative protonation mechanisms. However, the mutant undergoes only minor substrate binding-induced heme iron spin state shift toward high spin by comparison with WT OleTJE, indicating the key role of His85 in this process. Phe79 interacts with His85, and Phe79 mutants showed diminished affinity for shorter chain (C10–C16) fatty acids and weak substrate-induced high spin conversion. F79A OleTJE is least affected in substrate oxidation, whereas the F79W/Y mutants exhibit lower stability and cysteine thiolate protonation on reduction. Finally, Arg245 is crucial for binding the substrate carboxylate, and R245E/L mutations severely compromise activity and heme content, although alkene products are formed from some substrates, including stearic acid (C18:0). The results identify crucial roles for the active site amino acid trio in determining OleTJE catalytic efficiency in alkene production and in regulating protein stability, heme iron coordination, and spin state. PMID:28053093

  6. One-Pot Strategy for Thiazoline Synthesis from Alkenes and Thioamides.

    PubMed

    Alom, Nur-E; Wu, Fan; Li, Wei

    2017-02-17

    A convenient synthesis of a privileged pharmaceutical motif, thiazoline is accomplished. This reaction utilizes simple and readily available alkene and thioamide substrates in an intermolecular fashion via a simple one-pot procedure. A wide range of functional groups is tolerated, and the thiazoline product has been further utilized for the synthesis of the corresponding β-aminothiol and thiazole from routine hydrolysis and oxidation protocols.

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

    PubMed

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

    2014-05-05

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

  8. Catalytic Determinants of Alkene Production by the Cytochrome P450 Peroxygenase OleTJE.

    PubMed

    Matthews, Sarah; Belcher, James D; Tee, Kang Lan; Girvan, Hazel M; McLean, Kirsty J; Rigby, Stephen E J; Levy, Colin W; Leys, David; Parker, David A; Blankley, Richard T; Munro, Andrew W

    2017-03-24

    The Jeotgalicoccus sp. peroxygenase cytochrome P450 OleTJE (CYP152L1) is a hydrogen peroxide-driven oxidase that catalyzes oxidative decarboxylation of fatty acids, producing terminal alkenes with applications as fine chemicals and biofuels. Understanding mechanisms that favor decarboxylation over fatty acid hydroxylation in OleTJE could enable protein engineering to improve catalysis or to introduce decarboxylation activity into P450s with different substrate preferences. In this manuscript, we have focused on OleTJE active site residues Phe(79), His(85), and Arg(245) to interrogate their roles in substrate binding and catalytic activity. His(85) is a potential proton donor to reactive iron-oxo species during substrate decarboxylation. The H85Q mutant substitutes a glutamine found in several peroxygenases that favor fatty acid hydroxylation. H85Q OleTJE still favors alkene production, suggesting alternative protonation mechanisms. However, the mutant undergoes only minor substrate binding-induced heme iron spin state shift toward high spin by comparison with WT OleTJE, indicating the key role of His(85) in this process. Phe(79) interacts with His(85), and Phe(79) mutants showed diminished affinity for shorter chain (C10-C16) fatty acids and weak substrate-induced high spin conversion. F79A OleTJE is least affected in substrate oxidation, whereas the F79W/Y mutants exhibit lower stability and cysteine thiolate protonation on reduction. Finally, Arg(245) is crucial for binding the substrate carboxylate, and R245E/L mutations severely compromise activity and heme content, although alkene products are formed from some substrates, including stearic acid (C18:0). The results identify crucial roles for the active site amino acid trio in determining OleTJE catalytic efficiency in alkene production and in regulating protein stability, heme iron coordination, and spin state.

  9. Determination of the adsorption model of alkenes and alcohols on sulfonic copolymer by inverse gas chromatography.

    PubMed

    Słomkiewicz, P M

    2004-04-23

    The determination of a number of adsorption sites on sulfonated styrene-divinylbenzene copolymer for alkenes (propene, 1-butene, 1-pentene, 1-hexene, 1-heptene, isobutene, 2-methyl-1-butene, 2-methyl-2-butene, 2-methyl-1-pentene, 2-methyl-2-pentene and 2-methyl-2-hexene) and alcohols (methanol, ethanol and n-propanol, n-butanol, 2-butanol and tert-butanol) was performed by the saturation copolymer with vapors of adsorbate, by removing the excess of adsorbate from copolymer by blowing the inert gas through copolymer bed and by the desorption of adsorbed alcohol in the programmed increase of temperature. The adsorption measurements were performed on sulfonated ion-exchange resin (Amberlyst 15) with different concentrations of the acid group, which means with a varying number of adsorption sites. The following adsorption models for alkenes were suggested: the first in which one molecule of alkene is adsorbed by two sulfonic groups, for linear alcohols, the second in which one sulfonic group can adsorb one molecule of alcohol and for non-linear alcohols the third where one molecule of alcohol is adsorbed by two or more sulfonic groups.

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

    PubMed

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

    2014-12-08

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

  11. The Pressure Dependency of Stabilized Criegee Intermediate Yields of Selected Ozone-Alkene Reactions

    NASA Astrophysics Data System (ADS)

    Hakala, J. P.; Donahue, N. M.

    2014-12-01

    Stabilized Criegee Intermediates (SCI) play an important role as an oxidizing species in atmospheric reactions. The ozonolysis of alkenes in the atmosphere, i.e. the mechanism by which the SCIs are produced, is a major pathway to the formation of Secondary Organic Aerosols (SOA) in the atmosphere. Just how much SCIs contribute to the SOA formation is not well known and fundamental research in the kinetics of SCI formation need to be performed to shed light on this mystery. The alkene ozonolysis is highly exothermic reaction, so a third body is needed for stabilizing the SCI, thus making the SCI yield pressure dependent. We studied the production of SCIs at different pressures by studying their ability to oxidize sulfur dioxide in a pressure controlled flow reactor. We used a mixture of ultra-high purity nitrogen, oxygen, and a selective scavenger for hydroxyl radical (OH) as a carrier gas, and injected a mixture of nitrogen, sulfur dioxide and selected alkene to the center of the flow for ozonolysis to take place. With the OH radical scavenged, the SCI yield of the reaction was measured by measuring the amount of sulfuric acid formed in the reaction between SCI and sulfur dioxide with a Chemical Ionization Mass Spectrometer (CIMS). This work was supported by NASA/ROSES grant NNX12AE54G to CMU and Academy of Finland Center of Excellence project 1118615.

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

    PubMed

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

    2014-03-05

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

  13. Evidence for Alkene cis-Aminocupration, an Aminooxygenation Case Study: Kinetics, EPR Spectroscopy, and DFT Calculations

    PubMed Central

    Paderes, Monissa C.; Belding, Lee; Fanovic, Branden; Dudding, Travis; Keister, Jerome B.

    2012-01-01

    Alkene difunctionalization reactions are important in organic synthesis. We have recently shown that copper(II) complexes can promote and catalyze intramolecular alkene aminooxygenation, carboamination, and diamination reactions. In this contribution, we report a combined experimental and theoretical examination of the mechanism of the copper(II)-promoted olefin aminooxygenation reaction. Kinetics experiments revealed a mechanistic pathway involving an equilibrium reaction between a copper(II) carboxylate complex and the γ-alkenyl sulfonamide substrate and a rate-limiting intramolecular cis-addition of N–Cu across the olefin. Kinetic isotope effect studies support that the cis-aminocupration is the rate-determining step. UV/Vis spectra support a role for the base in the break-up of copper(II) carboxylate dimer to monomeric species. Electron paramagnetic resonance (EPR) spectra provide evidence for a kinetically competent N–Cu intermediate with a CuII oxidation state. Due to the highly similar stereochemical and reactivity trends among the CuII-promoted and catalyzed alkene difunctionalization reactions we have developed, the cis-aminocupration mechanism can reasonably be generalized across the reaction class. The methods and findings disclosed in this report should also prove valuable to the mechanism analysis and optimization of other copper(-II) carboxylate promoted reactions, especially those that take place in aprotic organic solvents. PMID:22237868

  14. Ru Catalyzed Alkene-Alkyne Coupling. Total Synthesis of Amphidinolide P

    PubMed Central

    Trost, Barry M.; Papillon, Julien P. N.; Nussbaumer, Thomas

    2008-01-01

    A coordinatively unsaturated ruthenium complex catalyzed the formation of a carbon-carbon bond between two judiciously chosen alkene and alkyne partners in good yield, and in a chemo- and regioselective fashion, in spite of the significant degree of unsaturation of the substrates. The resulting 1,4-diene forms the backbone of the cytotoxic marine natural product amphidinolide P. The alkene partner was rapidly assembled from (R)-glycidyl tosylate, which served as a linchpin in a one-flask, sequential three-components coupling process using vinyllithium and a vinyl cyanocuprate. The synthesis of the alkyne partner made use of an unusual anti-selective addition under chelation control conditions of an allyltin reagent derived from tiglic acid. In addition, a remarkably E-selective E2 process using the azodicarboxylate-triphenylphosphine system is featured. Also featured is the first example of the use of a β-lactone as a thermodynamic spring to effect macrolactonization. The oxetanone ring was thus used as a productive protecting group that increased the overall efficiency of this total synthesis. This work was also an opportunity to further probe the scope of the ruthenium-catalyzed alkene-alkyne coupling, in particular using enynes, and studies using various functionalized substrates are described. PMID:16351124

  15. Metal-free metathesis reaction of C-chiral allylic sulfilimines with aryl isocyanates: construction of chiral nonracemic allylic isocyanates.

    PubMed

    Grange, Rebecca L; Evans, P Andrew

    2014-08-27

    We report the facile and efficient metal-free metathesis reaction of C-chiral allylic sulfilimines with aryl isocyanates. This process facilitates the room temperature construction of an array of chiral nonracemic allylic isocyanates, which are versatile intermediates for the construction of unsymmetrical ureas, carbamates, thiocarbamates and amides. Furthermore, the sulfilimine/isocyanate metathesis reaction with 4,4'-methylene diphenyl diisocyanate (4,4'-MDI) circumvents harsh reaction conditions and/or hazardous reagents employed with more classical methods for the preparation of this important functional group.

  16. Luminescent hybrid materials of lanthanide β-diketonate and mesoporous host through covalent and ionic bonding with anion metathesis.

    PubMed

    Li, Qiu-Ping; Yan, Bing

    2012-07-28

    Luminescent mesoporous materials were prepared by performing an anion metathesis reaction on ionic liquid modified SBA15, which has imidazolium chloride bridging units. The lanthanide β-diketonate complex anion was successfully anchored onto the SBA15 framework after the anion metathesis reaction. The resulting materials were characterized by FTIR, TEM, TGA, small-angle X-ray powder diffraction (SAXRD) and nitrogen adsorption-desorption isotherms. The photoluminescent properties of these materials were investigated in detail, and the results reveal that these hybrid mesoporous SBA15, prepared through this preparation approach, present favorable photoluminescent behavior such as high luminescent quantum efficiencies and long luminescent lifetimes.

  17. Metathesis in the generation of low-temperature gas in marine shales

    PubMed Central

    2010-01-01

    The recent report of low-temperature catalytic gas from marine shales took on additional significance with the subsequent disclosure of natural gas and low-temperature gas at or near thermodynamic equilibrium in methane, ethane, and propane. It is important because thermal cracking, the presumed source of natural gas, cannot generate these hydrocarbons at equilibrium nor can it bring them to equilibrium over geologic time. The source of equilibrium and the source of natural gas are either the same (generation under equilibrium control) or closely associated. Here we report the catalytic interconversion of hydrocarbons (metathesis) as the source of equilibrium in experiments with Cretaceous Mowry shale at 100°C. Focus was on two metathetic equilibria: methane, ethane, and propane, reported earlier, Q (K = [(C1)*(C3)]/[(C2)2]), and between these hydrocarbons and n-butane, Q* (K = [(C1)*(n-C4)]/[(C2)*(C3)]), reported here for the first time. Two observations stand out. Initial hydrocarbon products are near equilibrium and have maximum average molecular weights (AMW). Over time, products fall from equilibrium and AMW in concert. It is consistent with metathesis splitting olefin intermediates [Cn] to smaller intermediates (fission) as gas generation creates open catalytic sites ([ ]): [Cn] + [ ] → [Cn-m] + [Cm]. Fission rates increasing exponentially with olefin molecular weight could contribute to these effects. AMW would fall over time, and selective fission of [C3] and [n-C4] would draw Q and Q* from equilibrium. The results support metathesis as the source of thermodynamic equilibrium in natural gas. PMID:20142998

  18. Metathesis in the generation of low-temperature gas in marine shales.

    PubMed

    Mango, Frank D; Jarvie, Daniel M

    2010-01-20

    The recent report of low-temperature catalytic gas from marine shales took on additional significance with the subsequent disclosure of natural gas and low-temperature gas at or near thermodynamic equilibrium in methane, ethane, and propane. It is important because thermal cracking, the presumed source of natural gas, cannot generate these hydrocarbons at equilibrium nor can it bring them to equilibrium over geologic time. The source of equilibrium and the source of natural gas are either the same (generation under equilibrium control) or closely associated. Here we report the catalytic interconversion of hydrocarbons (metathesis) as the source of equilibrium in experiments with Cretaceous Mowry shale at 100 degrees C. Focus was on two metathetic equilibria: methane, ethane, and propane, reported earlier, Q (K = [(C(1))*(C(3))]/[(C(2))(2)]), and between these hydrocarbons and n-butane, Q* (K = [(C(1))*(n-C(4))]/[(C(2))*(C(3))]), reported here for the first time. Two observations stand out. Initial hydrocarbon products are near equilibrium and have maximum average molecular weights (AMW). Over time, products fall from equilibrium and AMW in concert. It is consistent with metathesis splitting olefin intermediates [C(n)] to smaller intermediates (fission) as gas generation creates open catalytic sites ([ ]): [C(n)] + [ ] --> [C(n-m)] + [C(m)]. Fission rates increasing exponentially with olefin molecular weight could contribute to these effects. AMW would fall over time, and selective fission of [C(3)] and [n-C(4)] would draw Q and Q* from equilibrium. The results support metathesis as the source of thermodynamic equilibrium in natural gas.

  19. Lewis Base Catalysts 6: Carbene Catalysts

    PubMed Central

    Moore, Jennifer L.

    2013-01-01

    The use of N-heterocyclic carbenes as catalysts for organic transformations has received increased attention in the past 10 years. A discussion of catalyst development and nucleophilic characteristics precedes a description of recent advancements and new reactions using N-heterocyclic carbenes in catalysis. PMID:21494949

  20. Deactivation of Oxidation Catalysts

    DTIC Science & Technology

    1991-05-01

    the fresh catalyst . The loss in chromium may be related to the formation of volatile chromium oxychlorde which vaporizes from the catalyst . It is...CeO2 only marginally improved the thtrmal stability. The addition of 2% water vapor inhibited the oxidation of ethanol for all three copper catalysts ...original activity. Field tests of a copper chromite catalyst on process gas containing H2S, methyl mercaptan, n-aldehydes, and furfural showed

  1. Calcium, Strontium and Barium Homogeneous Catalysts for Fine Chemicals Synthesis.

    PubMed

    Sarazin, Yann; Carpentier, Jean-François

    2016-12-01

    The large alkaline earths (Ae), calcium, strontium and barium, have in the past 15 years yielded a brand new generation of heteroleptic molecular catalysts for the production of fine chemicals. However, the integrity of these complexes is often plagued by ligand redistribution equilibria in solution. This personal account retraces the paths followed in our research group towards the design of stable heteroleptic alkalino-earth complexes, including the use of intramolecular noncovalent Ae···H-Si and Ae···F-C interactions. Their implementation as homogenous precatalysts for reactions such as the intramolecular and intermolecular hydroamination and hydrophosphination of activated alkenes, the hydrophosphonylation of ketones, and the dehydrogenative coupling of amines and hydrosilanes that enable the efficient and controlled formations of CP, CN, or SiN σ-bonds, is presented in a synthetic perspective that highlights their overall outstanding catalytic performance.

  2. Synthesis of Cyclic Porphyrin Trimers through Alkyne Metathesis Cyclooligomerization and Their Host–Guest Binding Study

    SciTech Connect

    Yu, Chao; Long, Hai; Jin, Yinghua; Zhang, Wei

    2016-06-17

    Cyclic porphyrin trimers were synthesized through one-step cyclooligomerization via alkyne metathesis from diyne monomers. These macrocycles show interesting host-guest binding interactions with fullerenes, selectively binding C70 (6 x 103 M-1) over C60 and C84 (no binding observed). The fullerene-encapsulated host-guest complex can undergo guest or host exchange in the presence of another guest (2,4,6-tri(4-pyridyl)-1,3,5-triazine) or host (cage COP5) molecule with higher binding affinity.

  3. Synthesis of all-hydrocarbon stapled α-helical peptides by ring-closing olefin metathesis.

    PubMed

    Kim, Young-Woo; Grossmann, Tom N; Verdine, Gregory L

    2011-06-01

    This protocol provides a detailed procedure for the preparation of stapled α-helical peptides, which have proven their potential as useful molecular probes and as next-generation therapeutics. Two crucial features of this protocol are (i) the construction of peptide substrates containing hindered α-methyl, α-alkenyl amino acids and (ii) the ring-closing olefin metathesis (RCM) of the resulting resin-bound peptide substrates. The stapling systems described in this protocol, namely bridging one or two turns of an α-helix, are highly adaptable to most peptide sequences, resulting in favorable RCM kinetics, helix stabilization and promotion of cellular uptake.

  4. Bis(Cyclic Alkyl Amino Carbene) Ruthenium Complexes: A Versatile, Highly Efficient Tool for Olefin Metathesis.

    PubMed

    Gawin, Rafał; Kozakiewicz, Anna; Guńka, Piotr A; Dąbrowski, Paweł; Skowerski, Krzysztof

    2017-01-19

    The state-of-the-art in olefin metathesis is application of N-heterocyclic carbene (NHC)-containing ruthenium alkylidenes for the formation of internal C=C bonds and of cyclic alkyl amino carbene (CAAC)-containing ruthenium benzylidenes in the production of terminal olefins. A straightforward synthesis of bis(CAAC)Ru indenylidene complexes, which are highly effective in the formation of both terminal and internal C=C bonds at loadings as low as 1 ppm, is now reported.

  5. Rapid Solid-State Metathesis Routes to Nanostructured Silicon-Germainum

    NASA Technical Reports Server (NTRS)

    Kaner, Richard B. (Inventor); Bux, Sabah K. (Inventor); Fleurial, Jean-Pierre (Inventor); Rodriguez, Marc (Inventor)

    2014-01-01

    Methods for producing nanostructured silicon and silicon-germanium via solid state metathesis (SSM). The method of forming nanostructured silicon comprises the steps of combining a stoichiometric mixture of silicon tetraiodide (SiI4) and an alkaline earth metal silicide into a homogeneous powder, and initating the reaction between the silicon tetraiodide (SiI4) with the alkaline earth metal silicide. The method of forming nanostructured silicon-germanium comprises the steps of combining a stoichiometric mixture of silicon tetraiodide (SiI4) and a germanium based precursor into a homogeneous powder, and initiating the reaction between the silicon tetraiodide (SiI4) with the germanium based precursors.

  6. Bis(Cyclic Alkyl Amino Carbene) Ruthenium Complexes: A Versatile, Highly Efficient Tool for Olefin Metathesis

    PubMed Central

    Gawin, Rafał; Kozakiewicz, Anna; Guńka, Piotr A.; Dąbrowski, Paweł

    2016-01-01

    Abstract The state‐of‐the‐art in olefin metathesis is application of N‐heterocyclic carbene (NHC)‐containing ruthenium alkylidenes for the formation of internal C=C bonds and of cyclic alkyl amino carbene (CAAC)‐containing ruthenium benzylidenes in the production of terminal olefins. A straightforward synthesis of bis(CAAC)Ru indenylidene complexes, which are highly effective in the formation of both terminal and internal C=C bonds at loadings as low as 1 ppm, is now reported. PMID:27943616

  7. Recent advances in metathesis-derived polymers containing transition metals in the side chain

    PubMed Central

    Demonceau, Albert; Fischer, Helmut

    2015-01-01

    Summary This account critically surveys the field of side-chain transition metal-containing polymers as prepared by controlled living ring-opening metathesis polymerization (ROMP) of the respective metal-incorporating monomers. Ferrocene- and other metallocene-modified polymers, macromolecules including metal-carbonyl complexes, polymers tethering early or late transition metal complexes, etc. are herein discussed. Recent advances in the design and syntheses reported mainly during the last three years are highlighted, with special emphasis on new trends for superior applications of these hybrid materials. PMID:26877797

  8. Encaging Palladium Nanoparticles in Chitosan Modified Montmorillonite for Efficient, Recyclable Catalysts.

    PubMed

    Zeng, Minfeng; Wang, Yudong; Liu, Qi; Yuan, Xia; Zuo, Shufeng; Feng, Ruokun; Yang, Jing; Wang, Baoyi; Qi, Chenze; Lin, Yao

    2016-12-07

    Metal nanoparticles, once supported by a suitable scaffolding material, can be used as highly efficient heterogeneous catalysts for numerous organic reactions. The challenge, though, is to mitigate the continuous loss of metals from the supporting materials as reactions proceed, so that the catalysts can be recycled multiple times. Herein, we combine the excellent chelating property of chitosan (CS) and remarkable stability of montmorillonite (MMT) into a composite material to support metal catalysts such as palladium (Pd). The in situ reduction of Pd(2+) into Pd(0) in the interstices of MMT/CS composites effectively encages the Pd(0) nanoparticles in the porous matrices, while still allowing for reactant and product molecules of relatively small sizes to diffuse in and out the matrices. The prepared Pd(0)@MMT/CS catalysts are highly active for the Heck reactions of aromatic halides and alkenes, and can be recycled 30 times without significant loss of activities. Positron annihilation lifetime analysis and other structural characterization methods are implemented to elucidate the unique compartmentalization of metal catalysts in the composite matrices. As both CS and MMT are economical and abundant materials in nature, this approach may facilitate a versatile platform for developing highly recyclable, heterogeneous catalysts containing metal nanoparticles.

  9. Synthesis and characterization of mangenese(III) porphyrin supported on imidazole modified chloromethylated MIL-101(Cr): A heterogeneous and reusable catalyst for oxidation of hydrocarbons with sodium periodate

    SciTech Connect

    Zadehahmadi, Farnaz; Tangestaninejad, Shahram Moghadam, Majid Mirkhani, Valiollah Mohammadpoor-Baltork, Iraj; Khosropour, Ahmad R.; Kardanpour, Reihaneh

    2014-10-15

    In the present work, chloromethylated MIL-101(Cr) modified with imidazole, Im-MIL-101, was applied as a support for immobilizing of tetraphenylporphyrinatomangenese(III) chloride. The imidazole-bound MIL-101, Im-MIL-101, not only used as support for immobilization of manganese porphyrin but also applied as a heterogeneous axial base. The Mn(TPP)Cl@Im-MIL-101 catalyst was characterized by UV–vis, FT-IR, X-ray diffraction (XRD), N{sub 2} adsorption, field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), elemental analysis and inductively coupled plasma (ICP) methods. The catalytic activity of this new catalytic system was investigated in the alkene epoxidation and alkane hydroxylation using NaIO{sub 4} as an oxidant in CH{sub 3}CN/H{sub 2}O at room temperature. This heterogeneous catalyst is highly efficient, stable and reusable in the oxidation of hydrocarbons. - Highlights: • MIL-101 was modified by covalent post synthetic modification. • Mn(TPP)Cl was anchored to imidazole modified MIL-101 by covalent attachment. • A heterogeneous catalyst was prepared. • The catalyst was used for epoxidation of alkenes and hydroxylation of alkanes. • The catalyst was reusable.

  10. Clean gasoline reforming with superacid catalysts

    SciTech Connect

    Davis, B.H.

    1993-01-01

    The data showing the selectivity for production of 1-octene during dehydration of 2-octanol for ZrO[sub 2]-A and for ZrO[sub 2]-A/S are shown in Figure 17. The unsulfated sample exhibits high selectivity for 1-octene initially, but this declines to stabilize at about 40% at a reaction temperature of 320[degrees]C. However, the selectivity of the sulfated sample for 1-octene is consistently high at a reaction temperature of 220[degrees]C. The addition of sulfate ions has therefore increased the catalytic activity over that of the unsulfated zirconia, and at the same time produced a catalyst that is very selective for 1-octene only. Thus, this ZrO[sub 2]-A/S sample clearly does not exhibit superacid character since the dehydration product is the least stable one. Under similar conditions, dehydration using amorphous silica-alumina produces an equilibrium distribution of m-alkenes. Samples of ZrO[sub 2]-N were sulfated and these catalysts were even more active for 2-octanol dehydration than ZrO[sub 2]-A/S. However, the sulfated samples based upon ZrO[sub 2]-N produced nearly 100% conversion at the highest flow rate possible with the equipment [LHSV=12] and showed an equilibrium distribution of normal octenes rather than a selectivity for 1-octene. The samples of sulfated zirconias that are described here show a wide range of activity compared to unsulfated zirconias, but none of them exhibits the chain isomerization character expected of a superacute.

  11. Enantio- and Diastereodivergent Synthetic Route to Multifarious Cyclitols from D-Xylose via Ring-Closing Metathesis

    PubMed Central

    Luchetti, Giovanni; Ding, Kejia; d'Alarcao, Marc; Kornienko, Alexander

    2009-01-01

    Short stereoselective syntheses of various cyclitols, including the derivatives of conduritol B, conduritol F, myo-inositol and chiro-inositol, have been accomplished. The key steps in the syntheses are a ring-closing metathesis process and a diastereodivergent organometallic addition to a D-xylose-derived alde-hyde. PMID:19802347

  12. Absence of the Thorpe–Ingold Effect by gem-Diphenyl Groups in Ring-Closing Enyne Metathesis

    PubMed Central

    Kim, Yi Jin; Grimm, Jonathan B.; Lee, Daesung

    2007-01-01

    In tandem ring-closing metathesis of alkynyl silaketals containing two different tethered olefins, the gem-dimethyl group showed the expected Thorpe-Ingold effect, thereby giving good level of group selectivity. Unexpectedly, however, the corresponding gem-diphenyl group did not show any Thorpe-Ingold effect for the ring closure reaction. PMID:18046462

  13. Liquid-phase synthesis of bridged peptides using olefin metathesis of a protected peptide with a long aliphatic chain anchor.

    PubMed

    Aihara, Keisuke; Komiya, Chiaki; Shigenaga, Akira; Inokuma, Tsubasa; Takahashi, Daisuke; Otaka, Akira

    2015-02-06

    Bridged peptides including stapled peptides are attractive tools for regulating protein-protein interactions (PPIs). An effective synthetic methodology in a heterogeneous system for the preparation of these peptides using olefin metathesis and hydrogenation of protected peptides with a long aliphatic chain anchor is reported.

  14. System for reactivating catalysts

    SciTech Connect

    Ginosar, Daniel M.; Thompson, David N.; Anderson, Raymond P.

    2010-03-02

    A method of reactivating a catalyst, such as a solid catalyst or a liquid catalyst is provided. The method comprises providing a catalyst that is at least partially deactivated by fouling agents. The catalyst is contacted with a fluid reactivating agent that is at or above a critical point of the fluid reactivating agent and is of sufficient density to dissolve impurities. The fluid reactivating agent reacts with at least one fouling agent, releasing the at least one fouling agent from the catalyst. The at least one fouling agent becomes dissolved in the fluid reactivating agent and is subsequently separated or removed from the fluid reactivating agent so that the fluid reactivating agent may be reused. A system for reactivating a catalyst is also disclosed.

  15. Quartz Crystal Microbalance Analysis of Diels-Alder Reactions of Alkene Gases to Functional Ionic Liquids on Chips.

    PubMed

    Hsu, Tzu-Hsuan; Chiang, Shu-Jen; Chu, Yen-Ho

    2016-11-15

    We demonstrated here a successful development of the use of functional ionic liquids FIL 1 and FIL 3 for chemoselective detection of alkene gases measured by quartz crystal microbalance. This detection of gaseous alkenes was achieved by the Diels-Alder [4 + 2] cycloadditions with FIL 1 and FIL 3 thin-coated on quartz chips. Our functional ionic liquids could be prepared by straightforward synthetic chemistry in short steps and are superior in alkene gas detection. The QCM platform developed in this work is chemoselective with fast gas diffusion into ionic liquids, readily applicable to low molecular weight alkene gases and insensitive to moisture. To the best of our knowledge, this is the first report based upon the Diels-Alder reactions demonstrating sensitive alkene gas detection in ionic liquids on a QCM. This work is a proof-of-concept inspection of the promising use of a QCM-based sensor method for reaction-directed detection of gas samples, which is part of an ongoing program aimed at studying diseases.

  16. Nickel and cobalt-catalyzed coupling of alkyl halides with alkenes via heck reactions and radical conjugate addition.

    PubMed

    Qian, Qun; Zang, Zhenhua; Chen, Yang; Tong, Weiqi; Gong, Hegui

    2013-05-01

    Cross-coupling of alkyl halides with alkenes leading to Heck-type and addition products is summarized. The development of Heck reaction with aliphatic halides although has made significant progress in the past decade and particularly recently, it was much less explored in comparison with the aryl halides. The use of Ni- and Co-catalyzed protocols allowed efficient Heck coupling of activated and unactivated alkenes with 1°, 2° and 3° alkyl halides. In addition, radical conjugate addition to activated alkenes has become a well-established method that has led to efficient construction of many natural products. The utilization of Ni- and Co-catalyzed strategies would avoid toxic tin reagents, and therefore worth exploring. The recent development of Ni- and Co-catalyzed addition of alkyl halides to alkenes displays much improved reactivity and functional group tolerance. In this mini-review, we also attempt to overview the mechanisms that are proposed in the reactions, aiming at providing insight into the nickel and cobalt-catalyzed coupling of alkyl halides with alkenes.

  17. Dynamic Covalent Synthesis of Aryleneethynylene Cages through Alkyne Metathesis: Dimer, Tetramer, or Interlocked Complex?

    SciTech Connect

    Wang, Qi; Yu, Chao; Zhang, Chenxi; Long, Hai; Azarnoush, Setareh; Jin, Yinghua; Zhang, Wei

    2016-05-01

    A dynamic covalent approach towards rigid aryleneethynylene covalent organic polyhedrons (COPs) was explored. Our study on the relationship of the COP structures and the geometry of their building blocks reveals that the topology of aryleneethynylene COPs strongly depends on the size of the building blocks. A tetramer (D2h symmetric), dimer, or interlocked complex can be formed from monomers with the same face-to-edge angle but in different sizes. As alkyne metathesis is a self-exchange reaction and non-directional, the cyclooligomerization of multi-alkyne monomers involves both intramolecular cyclization and intermolecular metathesis reaction, resulting in complicated thermodynamic process disturbed by kinetic competition. Although a tetrahedron-shaped tetramer (Td symmetric) has comparable thermodynamic stability to a D2h symmetric tetramer, its formation is kinetically disfavored and was not observed experimentally. Aryleneethynylene COPs consist of purely unsaturated carbon backbones and exhibit large internal cavities, which would have interesting applications in host-guest chemistry and development of porous materials.

  18. Metathesis reactions of tris(adamantylimido)methylrhenium and aldehydes and imines

    SciTech Connect

    Wang, W.D.; Espenson, J.H.

    1999-11-22

    The tris(imido)methylrhenium compound CH{sub 3}Re(NAd){sub 3} (Ad = 1-adamantyl) was prepared and characterized. It reacts with aromatic aldehydes ArCHO forming the imines ArCH{double{underscore}bond} NAd. The reaction occurs in three stages, during which CH{sub 3}Re(NAd){sub 2}O and CH{sub 3}Re(NAd)O{sub 2} could be detected. In the third and slowest stage CH{sub 3}ReO{sub 3} (MTO) was formed, eventually in quantitative yield. The second-order rate constant for PhCHO in C{sub 6}D{sub 6} at 298 K is 1.4 x 10{sup {minus}4} L/mol s. Electron-donating substituents at the para-position of ArCHO cause a significant diminution in rate. Treated by the Hammett equation, the reaction constant is {rho} = +0.90. The reactions between CH{sub 3}Re(NAd){sub 3} and linear aliphatic aldehydes occur much faster than do reactions of nonlinear aliphatic or aromatic aldehydes, indicating an important steric effect. Ketones do not react. The imidorhenium complex evidently undergoes a metathesis reaction with the aldehyde. Analogously, CH{sub 3}Re(NAd){sub 3} reacts with imines. Imine-imine metathesis is catalyzed by MTO homogeneously and by MTO supported on Nb{sub 2}O{sub 5}.

  19. Stitched α-helical peptides via bis ring-closing metathesis.

    PubMed

    Hilinski, Gerard J; Kim, Young-Woo; Hong, Jooyeon; Kutchukian, Peter S; Crenshaw, Charisse M; Berkovitch, Shaunna S; Chang, Andrew; Ham, Sihyun; Verdine, Gregory L

    2014-09-03

    Conformationally stabilized α-helical peptides are capable of inhibiting disease-relevant intracellular or extracellular protein-protein interactions in vivo. We have previously reported that the employment of ring-closing metathesis to introduce a single all-hydrocarbon staple along one face of an α-helical peptide greatly increases α-helical content, binding affinity to a target protein, cell penetration through active transport, and resistance to proteolytic degradation. In an effort to improve upon this technology for stabilizing a peptide in a bioactive α-helical conformation, we report the discovery of an efficient and selective bis ring-closing metathesis reaction leading to peptides bearing multiple contiguous staples connected by a central spiro ring junction. Circular dichroism spectroscopy, NMR, and computational analyses have been used to investigate the conformation of these "stitched" peptides, which are shown to exhibit remarkable thermal stabilities. Likewise, trypsin proteolysis assays confirm the achievement of a structural rigidity unmatched by peptides bearing a single staple. Furthermore, fluorescence-activated cell sorting (FACS) and confocal microscopy assays demonstrate that stitched peptides display superior cell penetrating ability compared to their stapled counterparts, suggesting that this technology may be useful not only in the context of enhancing the drug-like properties of α-helical peptides but also in producing potent agents for the intracellular delivery of proteins and oligonucleotides.

  20. Reduction in syllable onsets in the acquisition of Polish: deletion, coalescence, metathesis and gemination.

    PubMed

    łukaszewicz, Beata

    2007-02-01

    This paper focuses on four strategies of onset reduction employed by a single child (4;0-4;4) acquiring Polish: deletion, coalescence, metathesis, and gemination. Deletion and coalescence occur in word-initial onsets while metathesis and gemination are restricted to word-medial position. The data, which constitute an intriguing 'conspiracy' case (Kisseberth, 1970), are analysed within OPTIMALITY THEORY (henceforth, OT; Prince & Smolensky, 1993/2004; McCarthy & Prince, 1995) in which all surface-true 'processes' are motivated through the interaction of ranked and violable constraints. The OT account makes it possible to envisage the four strategies as different surface responses to the undominated *COMPLEXOnset which militates against onset clusters. The choice of a particular strategy as well as its restriction to a particular word position is not random but follows from the interplay between *COMPLEXOnset, sonority-based syllable structure constraints (Margin Hierarchy, CONTACT LAW), context-sensitive markedness constraints (CODA CONDITION, *Nasal-Fricative) and faithfulness constraints. The present study confirms previous sonority-based findings, supplies further evidence for universal sonority mechanisms from word-medial clusters, and points to the coexistence of child-specific and abstract adult-based phonological strategies in the child's system.

  1. Catalyst patterning for nanowire devices

    NASA Technical Reports Server (NTRS)

    Li, Jun (Inventor); Cassell, Alan M. (Inventor); Han, Jie (Inventor)

    2004-01-01

    Nanowire devices may be provided that are based on carbon nanotubes or single-crystal semiconductor nanowires. The nanowire devices may be formed on a substrate. Catalyst sites may be formed on the substrate. The catalyst sites may be formed using lithography, thin metal layers that form individual catalyst sites when heated, collapsible porous catalyst-filled microscopic spheres, microscopic spheres that serve as masks for catalyst deposition, electrochemical deposition techniques, and catalyst inks. Nanowires may be grown from the catalyst sites.

  2. Alkene/diamond liquid/solid interface characterization using internal photoemission spectroscopy.

    PubMed

    Nebel, C E; Shin, D; Takeuchi, D; Yamamoto, T; Watanabe, H; Nakamura, T

    2006-06-20

    The photochemical attachment of 10-amino-dec-1-ene molecules protected with a trifluoroacetic acid group (TFAAD) on hydrogen-terminated single-crystalline chemical vapor deposited (CVD) diamond is characterized by total photoyield spectroscopy (TPYS), conductivity, Hall-effect, spectrally resolved photoconductivity (SPC), optical transmission experiments, and, for the first time, by in situ internal photoemission (IPE) spectroscopy applied in the spectral regime from 4 to 6 eV on the alkene/diamond (liquid/solid) heterostructures. These experiments are performed on undoped, (100) oriented, single-crystalline CVD diamond films, which contain no grain boundaries and have negligible bulk and surface defect densities. X-ray photoelectron spectroscopy (XPS) is used to investigate the chemical bonding of alkene molecules to diamond. The spectroscopic set of data shows that the photochemical reaction window of H-terminated diamond is shifted below the optical gap of diamond because of the negative electron affinity. In situ IPE experiments reveal electron emission between 4.5 and 5.2 eV. A model is introduced and discussed in which valence-band electrons are optically excited into empty hydrogen-induced surface states of diamond from where they tunnel into empty pi states of alkene molecules. We theoretically discuss the fastest attachment time to achieve a saturated TFAAD layer of about 2 x 10(14) cm(-)(2) on diamond, which is experimentally detected to be 7 h. In the case of direct optical electron excitations from diamond, the bonding efficiency will be one TFAAD molecule attachment arising from about 1600 emitted electrons.

  3. Formation of {beta}-hydroxycarbonyls from the OH radical-initiated reactions of selected alkenes

    SciTech Connect

    Aschmann, S.M.; Arey, J.; Atkinson, R.

    2000-05-01

    {beta}-Hydroxycarbonyls can be formed from the gas-phase reactions of alkenes with the OH radical, both in the presence and in the absence of NO. To date, because of analytical difficulties, few data have been reported for the formation of this class of compound from the reactions of the OH radical with alkenes. The authors have determined that {beta}-hydroxy-ketones can be readily analyzed by gas chromatography, and in this work they have shown that in 1 atm of air the {beta}-hydroxyalkoxy radicals formed in the reactions of the OH radical with trans-2-butene, trans-3-hexene, 1-butene, and {alpha}-pinene in the presence of NO primarily decompose rather than react with O{sub 2}. Rate constant ratios k{sub d}/k{sub 0{sub 2}} (or lower limits thereof), where k{sub d} and k{sub 0{sub 2}} are respectively the rate constants for the decomposition and the reaction with 0{sub 2} of the intermediate {beta}-hydroxyalkoxy radicals, have been obtained for the reactions of the CH{sub 3}CH(O)CH-(OH)CH{sub 3}, CH{sub 3}CH{sub 2}CH(O)CH{sub 2}OH, and CH{sub 3}CH{sub 2}CH(O)CH(OH)CH{sub 2}-CH{sub 3} radicals at 296 {+-} 2 K and atmospheric pressure. Using the O{sub 3} reactions with the alkenes to generate OH radicals, the reactions of the OH radical to generate OH radicals, the reactions of the OH radical with trans-2-butene, trans-3-hexene, and {alpha}-pinene in the absence of NO lead to the formation of the expected {beta}-hydroxycarbonyls and (at least for trans-2-butene) the {alpha},{beta}-diol.

  4. Carbon-Carbon Bond Formation in a Weak Ligand Field: Leveraging Open Shell First Row Transition Metal Catalysts.

    PubMed

    Chirik, Paul James

    2017-01-12

    Unique features of Earth abundant transition metal catalysts are reviewed in the context of catalytic carbon-carbon bond forming reactions. Aryl-substituted bis(imino)pyridine iron and cobalt dihalide compounds, when activated with alkyl aluminum reagents, form highly active catalysts for the polymerization of ethylene. Open shell iron and cobalt alkyl complexes have been synthesized that serve as single component olefin polymerization catalysts. Reduced bis(imino)pyridine iron- and cobalt dinitrogen compounds have also been discovered that promote the unique [2+2] cycloaddition of unactivated terminal alkenes. Electronic structure studies support open shell intermediates, a deviation from traditional strong field organometallic compounds that promote catalytic C-C bond formation.

  5. Scope and mechanism of the Pt-catalyzed enantioselective diboration of monosubstituted alkenes.

    PubMed

    Coombs, John R; Haeffner, Fredrik; Kliman, Laura T; Morken, James P

    2013-07-31

    The Pt-catalyzed enantioselective diboration of terminal alkenes can be accomplished in an enantioselective fashion in the presence of chiral phosphonite ligands. Optimal procedures and the substrate scope of this transformation are fully investigated. Reaction progress kinetic analysis and kinetic isotope effects suggest that the stereodefining step in the catalytic cycle is olefin migratory insertion into a Pt-B bond. Density functional theory analysis, combined with other experimental data, suggests that the insertion reaction positions platinum at the internal carbon of the substrate. A stereochemical model for this reaction is advanced that is in line both with these features and with the crystal structure of a Pt-ligand complex.

  6. Recent Developments in Metal-Catalyzed Additions of Oxygen Nucleophiles to Alkenes and Alkynes

    NASA Astrophysics Data System (ADS)

    Hintermann, Lukas

    Progress in the field of metal-catalyzed redox-neutral additions of oxygen nucleophiles (water, alcohols, carboxylic acids, and others) to alkenes, alkynes, and allenes between 2001 and 2009 is critically reviewed. Major advances in reaction chemistry include development of chiral Lewis acid catalyzed asymmetric oxa-Michael additions and Lewis-acid catalyzed hydro-alkoxylations of nonactivated olefins, as well as further development of Markovnikov-selective cationic gold complex-catalyzed additions of alcohols or water to alkynes and allenes.

  7. Scope and Mechanism of the Pt-Catalyzed Enantioselective Diboration of Monosubstituted Alkenes

    PubMed Central

    Coombs, John R.; Haeffner, Fredrik; Kliman, Laura T.; Morken, James P.

    2013-01-01

    The Pt-catalyzed enantioselective diboration of terminal alkenes can be accomplished in an enantioselective fashion in the presence of chiral phosphonite ligands. Optimal procedures and the substrate scope of this transformation are fully investigated. Reaction progress kinetic analysis and natural abundance isotope effects suggest that the stereodefining step in the catalytic cycle is olefin migratory insertion into a Pt-B bond. DFT analysis, combined with other experimental data, suggest that the insertion reaction positions platinum at the internal carbon of the substrate. A stereochemical model for this reaction is advanced that is in line both with these features and with the crystal structure of a Pt-ligand complex. PMID:23862690

  8. One-pot synthesis of 1-iodoalkynes and trisubstituted alkenes from benzylic and allylic bromides.

    PubMed

    Pelletier, Guillaume; Lie, Sharon; Mousseau, James J; Charette, André B

    2012-11-02

    1-Iodoalkynes are formed in moderate to high yields from readily accessible benzylic and allylic alkyl bromides by a one-pot homologation/double elimination procedure with iodoform (CHI(3)). The developed conditions include facile purification and avoid the use of an excess of triphenylphosphine (PPh(3)), as described in classical Corey-Fuchs iodoalkynylation conditions. Replacing CHI(3) with CHI(2)Cl allows the isolation of the corresponding gem-(Z)-chloro-(E)-iodoalkene in good yield and stereoselectivity. Moreover, the use of benzhydryl bromides as nucleophiles enables the synthesis of trisubstituted alkenes under similar reaction conditions.

  9. Aminomethylhydroxylation of alkenes: Exploitation in the synthesis of scaffolds for small molecule libraries.

    PubMed

    Colomer, Ignacio; Adeniji, Ololade; Burslem, George M; Craven, Philip; Rasmussen, Martin Ohsten; Willaume, Anthony; Kalliokoski, Tuomo; Foster, Richard; Marsden, Stephen P; Nelson, Adam

    2015-06-01

    The application of [4+2] cycloadditions between alkenes and an N-benzoyl iminium species, generated in situ under acidic conditions, is described in the synthesis of diverse molecular scaffolds. The key reaction led to the formation of cyclic imidates in good yield and with high regioselectivity. It was demonstrated that the cyclic imidates may be readily converted into 1,3-amino alcohols. Incorporation of orthogonally-reactive functionality, such as aryl and alkyl bromides, into the cycloaddition substrates enabled the synthesis of additional scaffolds. For one scaffold, the synthesis of exemplar screening compounds was undertaken to demonstrate potential value in small molecule library production.

  10. Enantioselective epoxidation of non-functionalized alkenes using carbohydrate based salen-Mn(III) complexes.

    PubMed

    Zhao, Shanshan; Zhao, Jiquan; Zhao, Dongmin

    2007-02-05

    Three new salen ligands with carbohydrate moieties were prepared from a salicylaldehyde derivative obtained by reaction of 1,2:5,6-di-O-isopropylidene-alpha-D-glucofuranose with 3-tert-butyl-5-(chloro-methyl)-2-hydroxybenzaldehyde. These ligands were coordinated with Mn(III) to give three chiral salen-Mn(III) complexes. The complexes were characterized and employed in the asymmetric epoxidation of unfunctionalized alkenes. Catalytic results showed that although there are no chiral groups on the diimine bridge, these complexes had some enantioselectivity, which indicates the carbohydrate moiety has an asymmetric inducing effect in the epoxidation reaction.

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

    PubMed

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

    2014-05-19

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

  12. In situ EPR studies of reaction pathways in Titania photocatalyst-promoted alkylation of alkenes.

    PubMed

    Rhydderch, Shona; Howe, Russell F

    2015-03-03

    In situ EPR spectroscopy at cryogenic temperatures has been used to observe and identify paramagnetic species produced when titania is irradiated in the presence of reactants used in the photocatalytic alkylation of maleimide with t-butyl carboxylic acid or phenoxyacetic acid. It is shown that maleimide acts as an acceptor of conduction band electrons. Valence band holes oxidise t-butyl carboxylic acid to the t-butyl radical and phenoxyacetic acid to the phenoxyacetic acid radical cation. In the presence of maleimide, the phenoxymethyl radical is formed from phenoxyacetic acid. The relevance of these observations to the mechanisms of titania photocatalyst-promoted alkylation of alkenes is discussed.

  13. Stability of prostacyclin analogues: an unusual lack of reactivity in acid-catalyzed alkene hydration.

    PubMed

    Magill, A; O'Yang, C; Powell, M F

    1988-04-01

    Prostacyclin analogue 5 undergoes specific acid-catalyzed hydration (kH+ = 1.9 x 10(-7)M-1 sec-1 at 25 degrees C) and a pH-independent oxidation reaction (k0 = 1.2 x 10(-10) sec-1 at 25 degrees C) above pH approximately 5. The hydration reaction for 5 is much slower than for other structurally similar exocyclic alkenes, even though the rate-determining step is proton transfer. This slowness of reaction and an analysis of the pH-rate profile show that 5 does not exhibit significant intramolecular general acid catalysis, as does prostacyclin.

  14. Allylic Amines as Key Building Blocks in the Synthesis of (E)-Alkene Peptide Isosteres

    PubMed Central

    Skoda, Erin M.; Davis, Gary C.

    2012-01-01

    Nucleophilic imine additions with vinyl organometallics have developed into efficient, high yielding, and robust methodologies to generate structurally diverse allylic amines. We have used the hydrozirconation-transmetalation-imine addition protocol in the synthesis of allylic amine intermediates for peptide bond isosteres, phosphatase inhibitors, and mitochondria-targeted peptide mimetics. The gramicidin S-derived XJB-5-131 and JP4-039 and their analogs have been prepared on up to 160 g scale for preclinical studies. These (E)-alkene peptide isosteres adopt type II′ β-turn secondary structures and display impressive biological properties, including selective reactions with reactive oxygen species (ROS) and prevention of apoptosis. PMID:22323894

  15. Textured catalysts and methods of making textured catalysts

    DOEpatents

    Werpy, Todd; Frye, Jr., John G.; Wang, Yong; Zacher, Alan H.

    2007-03-06

    A textured catalyst having a hydrothermally-stable support, a metal oxide and a catalyst component is described. Methods of conducting aqueous phase reactions that are catalyzed by a textured catalyst are also described. The invention also provides methods of making textured catalysts and methods of making chemical products using a textured catalyst.

  16. Conversion of 1-alkenes into 1,4-diols through an auxiliary-mediated formal homoallylic C-H oxidation.

    PubMed

    Ghavtadze, Nugzar; Melkonyan, Ferdinand S; Gulevich, Anton V; Huang, Chunhui; Gevorgyan, Vladimir

    2014-02-01

    The ubiquitous nature of C-H bonds in organic molecules makes them attractive as a target for rapid complexity generation, but brings with it the problem of achieving selective reactions. In developing new methodologies for C-H functionalization, alkenes are an attractive starting material because of their abundance and low cost. Here we describe the conversion of 1-alkenes into 1,4-diols. The method involves the installation of a new Si,N-type chelating auxiliary group on the alkene followed by iridium-catalysed C-H silylation of an unactivated δ-C(sp(3))-H bond to produce a silolane intermediate. Oxidation of the C-Si bonds affords a 1,4-diol. The method is demonstrated to have broad scope and good functional group compatibility by application to the selective 1,4-oxygenation of several natural products and derivatives.

  17. The chemistry of simple alkene molecules on Si(100)c(4 × 2): The mechanism of cycloaddition and their selectivities

    NASA Astrophysics Data System (ADS)

    Akagi, Kazuto; Yoshinobu, Jun

    2016-10-01

    The chemistry of simple alkene molecules on the Si(100) surface is reviewed with the newly-produced visual presentation by theoretical calculations. The early pioneering studies by the Kyoto Group and Pittsburgh group reported the di-σ bond formation and the precursor-mediated chemisorption for acetylene and ethylene on Si(100), respectively. Thereafter, these studies have been stimulating various studies of organic molecules on Si surfaces. Our recent studies have observed the precursor states for alkene chemisorption and elucidated the microscopic mechanisms of the di-σ bond formation (cycloaddition) with the help of theoretical calculations; the site-, stereo- and regio-selective chemisorption of simple alkene molecules on Si(100)c(4 × 2) has been established.

  18. Neutral losses: a type of important variables in prediction of branching degree for acyclic alkenes from mass spectra.

    PubMed

    Zhang, Liangxiao; Fan, Wei; Cao, Dongsheng; Zeng, Maomao; Xiao, Hongbin; Liang, Yizeng

    2012-03-30

    Neutral losses are a type of important variables in mass spectral interpretation. Since it is hard to calculate or extract neutral losses from mass spectra, they are usually discarded. In this study, dissimilarity analysis was employed to extract mass spectral characteristics for predicting branching degree of acyclic alkenes. The relationships between branching degree and neutral loss were constructed under direction of experimental observation and mass spectral fragmentations. A branching degree predictor of acyclic alkenes was subsequently built based on the above relationships. After tested by the experimental data in previous studies, the predictor could correctly provide the branching degree from abundant ions of mass spectra. More importantly, this predictor was able to point out which acyclic alkenes could be predicted correctly or not.

  19. Polymer Activated Catalysts.

    DTIC Science & Technology

    1980-11-01

    dorhodiun(I) carbonyltris(triphenylphosphine), chlororhodium(I) ethylene - 20, U. RACY (Ce1n ate en m eld. side Nea~ 019140 IdAW7 141f OFeUs ma.) Three...CpTi (Cp) Cl2 RCH2CH-CH2 , RCH=CHCH3 (mainly E.) (2)R’MgBr ization was successful with 1-butene, 1-pentene, and 1- octene . In- ternal alkenes such as 2... octene apparently do not further react. Similar behavior was noted in hydrogenation reactions. In long term experiments in which fresh charges of

  20. Design and synthesis of hybrid cyclophanes containing thiophene and indole units via Grignard reaction, Fischer indolization and ring-closing metathesis as key steps

    PubMed Central

    2015-01-01

    Summary We demonstrate a new synthetic strategy to cyclophanes containing thiophene and indole moieties via Grignard addition, Fischer indolization and ring-closing metathesis as key steps. PMID:26425209

  1. Sources of C₂-C₄ alkenes, the most important ozone nonmethane hydrocarbon precursors in the Pearl River Delta region.

    PubMed

    Zhang, Yanli; Wang, Xinming; Zhang, Zhou; Lü, Sujun; Huang, Zhonghui; Li, Longfeng

    2015-01-01

    Surface ozone is becoming an increasing concern in China's megacities such as the urban centers located in the highly industrialized and densely populated Pearl River Delta (PRD) region, where previous studies suggested that ozone production is sensitive to VOC emissions with alkenes being important precursors. However, little was known about sources of alkenes. Here we present our monitoring of ambient volatile organic compounds at four representative urban, suburban and rural sites in the PRD region during November-December 2009, which experienced frequent ozone episodes. C2-C4 alkenes, whose total mixing ratios were 11-20% of non-methane hydrocarbons (NMHCs) quantified, accounted for 38-64% of ozone formation potentials (OFPs) and 30-50% of the total hydroxyl radical (OH) reactivity by NMHCs. Ethylene was the most abundant alkene, accounting for 8-15% in total mixing ratios of NMHCs and contributed 25-46% of OFPs. Correlations between C2-C4 alkenes and typical source tracers suggested that ethylene might be largely related to vehicle exhausts and industry activities, while propene and butenes were much more LPG-related. Positive Matrix Factorization (PMF) confirmed that vehicle exhaust and liquefied petroleum gas (LPG) were two major sources that altogether accounted for 52-62%, 58-77%, 73-83%, 68-79% and 73-84% for ethylene, propene, 1-butene, trans-2-butene and cis-2-butene, respectively. Vehicle exhausts alone contributed 32-49% ethylene and 35-41% propene. Industry activities contributed 13-23% ethylene and 7-20% propene. LPG instead contributed the most to butenes (38-65%) and substantially to propene (23-36%). Extensive tests confirmed high fractions of propene and butenes in LPG then used in Guangzhou and in LPG combustion plumes; therefore, limiting alkene contents in LPG would benefit regional ozone control.

  2. An Electronic Rationale for Observed Initiation Rates in Ruthenium-Mediated Olefin Metathesis: Charge Donation in Phosphine And N-Heterocyclic Carbene Ligands

    SciTech Connect

    Getty, K.; Delgado-Jaime, M.U.; Kennepohl, P.

    2009-06-01

    Ru K-edge XAS data indicate that second generation ruthenium-based olefin metathesis precatalysts (L = N-heterocyclic carbene) possess a more electron-deficient metal center than in the corresponding first generation species (L = tricyclohexylphosphine). This surprising effect is also observed from DFT calculations and provides a simple rationale for the slow phosphine dissociation kinetics previously noted for second-generation metathesis precatalysts.

  3. The effect of supported MoO(X) structures on the reaction pathways of propene formation in the metathesis of ethylene and 2-butene.

    PubMed

    Hahn, T; Kondratenko, E V; Linke, D

    2014-08-21

    The kind of surface MoOX structures on Al2O3-SiO2 was found to determine propene selectivity in the metathesis of ethylene and 2-butene. Compared to isolated tetrahedral MoOX species, their polymerized octahedral counterparts show significantly lower activity for isomerisation of 2- to 1-butene thus hindering non-selective metathesis of these butenes. In addition, they reveal higher ability to engage ethylene in propene formation.

  4. 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.

  5. UV light-mediated difunctionalization of alkenes through aroyl radical addition/1,4-/1,2-aryl shift cascade reactions.

    PubMed

    Zheng, Lewei; Huang, Hongli; Yang, Chao; Xia, Wujiong

    2015-02-20

    UV light-mediated difunctionalization of alkenes through an aroyl radical addition/1,4-/1,2-aryl shift has been described. The resulted aroyl radical from a photocleavage reaction added to acrylamide compounds followed by cyclization led to the formation of oxindoles, whereas the addition to cinnamic amides aroused a unique 1,4-aryl shift reaction. Furthermore, the difunctionalization of alkenes of prop-2-en-1-ols was also achieved through aroyl radical addition and a sequential 1,2-aryl shift cascade reaction.

  6. Catalyst Alloys Processing

    NASA Astrophysics Data System (ADS)

    Tan, Xincai

    2014-10-01

    Catalysts are one of the key materials used for diamond formation at high pressures. Several such catalyst products have been developed and applied in China and around the world. The catalyst alloy most widely used in China is Ni70Mn25Co5 developed at Changsha Research Institute of Mining and Metallurgy. In this article, detailed techniques for manufacturing such a typical catalyst alloy will be reviewed. The characteristics of the alloy will be described. Detailed processing of the alloy will be presented, including remelting and casting, hot rolling, annealing, surface treatment, cold rolling, blanking, finishing, packaging, and waste treatment. An example use of the catalyst alloy will also be given. Industrial experience shows that for the catalyst alloy products, a vacuum induction remelt furnace can be used for remelting, a metal mold can be used for casting, hot and cold rolling can be used for forming, and acid pickling can be used for metal surface cleaning.

  7. In Situ Formation of Pyridyl-Functionalized Poly(3-hexylthiophene)s via Quenching of the Grignard Metathesis Polymerization: Toward Ligands for Semiconductor Quantum Dots

    SciTech Connect

    Kochemba, William Michael; Pickel, Deanna L; Sumpter, Bobby G; Chen, Jihua; Kilbey, II, S Michael

    2012-01-01

    The synthesis of well-defined, end-functional poly(3-hexylthiophene)s (P3HTs) by in situ quenching of the Grignard metathesis (GRIM) polymerization is complicated by the extreme tendency to favor difunctional products in all but a few cases. A facile one-pot method for preparing 2-pyridyl and 3-pyridyl P3HTs with high abundance of monofunctional products is established via an examination of the kinetics of the end-functionalization quenching reaction with lithium chloride complexes of 2- and 3-pyridyl Grignard reagents. Density functional theory calculations guide the selection of pyridine as the end group, which provides the capacity to ligate cadmium selenide (CdSe) nanocrystals and arrests aggregation upon thermal annealing when dispersed in a P3HT matrix. The relative abundances of various end-functional products, as ascertained by high-resolution matrix assisted laser desorption ionization time-of-flight mass spectrometry, can be altered through the use of 1-pentene as an additive: GRIM polymerizations quenched with 3-pyridyl and 2-pyridyl Grignard reagents show 5% and 18% abundances of difunctional, pyridyl-capped P3HTs, respectively, when 1-pentene is present at 1000:1 relative to the nickel catalyst. This represents a significant improvement compared to quenching with aryl Grignard reagents, where difunctional products predominate. The ability to manipulate end group compositions coupled with the propensity of pyridyl-functionalized P3HTs to ligate semiconductor quantum dots (SQDs) opens new possibilities for tuning the morphology of conjugated polymer/SQD blends.

  8. Methods of making textured catalysts

    DOEpatents

    Werpy, Todd; Frye, Jr., John G.; Wang, Yong; Zacher, Alan H.

    2010-08-17

    A textured catalyst having a hydrothermally-stable support, a metal oxide and a catalyst component is described. Methods of conducting aqueous phase reactions that are catalyzed by a textured catalyst are also described. The invention also provides methods of making textured catalysts and methods of making chemical products using a textured catalyst.

  9. Bio-oil Stabilization by Hydrogenation over Reduced Metal Catalysts at Low Temperatures

    SciTech Connect

    Wang, Huamin; Lee, Suh-Jane; Olarte, Mariefel V.; Zacher, Alan H.

    2016-08-30

    Biomass fast pyrolysis integrated with bio-oil upgrading represents a very attractive approach for converting biomass to hydrocarbon transportation fuels. However, the thermal and chemical instability of bio-oils presents significant problems when they are being upgraded, and development of effective approaches for stabilizing bio-oils is critical to the success of the technology. Catalytic hydrogenation to remove reactive species in bio-oil has been considered as one of the most efficient ways to stabilize bio-oil. This paper provides a fundamental understanding of hydrogenation of actual bio-oils over a Ru/TiO2 catalyst under conditions relevant to practical bio-oil hydrotreating processes. Bio-oil feed stocks, bio-oils hydrogenated to different extents, and catalysts have been characterized to provide insights into the chemical and physical properties of these samples and to understand the correlation of the properties with the composition of the bio-oil and catalysts. The results indicated hydrogenation of various components of the bio-oil, including sugars, aldehydes, ketones, alkenes, aromatics, and carboxylic acids, over the Ru/TiO2 catalyst and 120 to 160oC. Hydrogenation of these species significantly changed the chemical and physical properties of the bio-oil and overall improved its thermal stability, especially by reducing the carbonyl content, which represented the content of the most reactive species (i.e., sugar, aldehydes, and ketones). The change of content of each component in response to increasing hydrogen additions suggests the following bio-oil hydrogenation reaction sequence: sugar conversion to sugar alcohols, followed by ketone and aldehyde conversion to alcohols, followed by alkene and aromatic hydrogenation, and then followed by carboxylic acid hydrogenation to alcohols. Hydrogenation of bio-oil samples with different sulfur contents or inorganic material contents suggested that sulfur poisoning of the reduced Ru metal catalysts was

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

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

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

  11. Electron transfer reactions in the alkene mono-oxygenase complex from Nocardia corallina B-276.

    PubMed Central

    Gallagher, S C; Cammack, R; Dalton, H

    1999-01-01

    Nocardia corallina B-276 possesses a multi-component enzyme, alkene mono-oxygenase (AMO), that catalyses the stereoselective epoxygenation of alkenes. The reductase component of this system has been shown by EPR and fluorescence spectroscopy to contain two prosthetic groups, an FAD centre and a [2Fe-2S] cluster. The role of these centres in the epoxygenation reaction was determined by midpoint potential measurements and electron transfer kinetics. The order of potentials of the prosthetic groups of the reductase were FAD/FAD.=-216 mV, [2Fe-2S]/[2Fe-2S].=-160 mV and FAD./FAD.=-134 mV. Combined, these data implied that the reductase component supplied the energy required for the epoxygenation reaction and allowed a prediction of the mechanism of electron transfer within the AMO complex. The FAD moiety was reduced by bound NADH in a two-electron reaction. The electrons were then transported to the [2Fe-2S] centre one at a time, which in turn reduced the di-iron centre of the epoxygenase. Reduction of the di-iron centre is required for oxygen binding and substrate oxidation. PMID:10085230

  12. Epoxidation of Short-Chain Alkenes by Resting-Cell Suspensions of Propane-Grown Bacteria

    PubMed Central

    Hou, Ching T.; Patel, Ramesh; Laskin, Allen I.; Barnabe, Nancy; Barist, Irene

    1983-01-01

    Sixteen new cultures of propane-utilizing bacteria were isolated from lake water from Warinanco Park, Linden, N.J. and from lake and soil samples from Bayway Refinery, Linden, N.J. In addition, 19 known cultures obtained from culture collections were also found to be able to grow on propane as the sole carbon and energy source. In addition to their ability to oxidize n-alkanes, resting-cell suspensions of both new cultures and known cultures grown on propane oxidize short-chain alkenes to their corresponding 1,2-epoxides. Among the substrate alkenes, propylene was oxidized at the highest rate. In contrast to the case with methylotrophic bacteria, the product epoxides are further metabolized. Propane and other gaseous n-alkanes inhibit the epoxidation of propylene. The optimum conditions for in vivo epoxidation are described. Results from inhibition studies indicate that a propane monooxygenase system catalyzes both the epoxidation and hydroxylation reactions. Experiments with cell-free extracts show that both hydroxylation and epoxidation activities are located in the soluble fraction obtained after 80,000 × g centrifugation. PMID:16346338

  13. The Role of Criegee Intermediates in Particle Formation and Growth during the Ozonolysis of Small Alkenes

    NASA Astrophysics Data System (ADS)

    Zhao, Y.; Wingen, L. M.; Perraud, V. M.; Finlayson-Pitts, B. J.

    2014-12-01

    Ozonolysis of alkenes is an important source of particulate matter (e.g., secondary organic aerosol) in the atmosphere. However, the mechanisms by which Criegee intermediates (CI) react to form the particles, particularly the oligomeric components, are currently not well understood. In this study, ozonolysis of trans-3-hexene was investigated with a focus on the formation mechanism of oligomers involving CI, as well as their contributions to particle formation and growth. Ozonolysis experiments were performed both in a static chamber and in a flow reactor in the absence and presence of an OH or stabilized CI (SCI) scavenger. The oligomeric and elemental composition of the total and size-selected particles was measured with different mass spectrometries, and the effects of adding OH and SCI scavengers were investigated. Size-selected measurements show that the relative abundance of higher ordered oligomers in the particles decreases with increasing particle size, indicating the preference of larger oligomers in the growth of smaller particles. Consistent with oligomeric composition, the O/C ratio of the particles decreases with particle size, suggesting more oxygenated organic material (e.g., primarily oligomeric peroxides) in smaller particles. The mechanism for particle formation suggested by these data is the initial reaction of RO2 radicals to the CI, followed by sequential addition of CI, in agreement with the earlier work of Sadezky et al. (2008). The relationship to the mechanism of particle formation from larger alkenes such as terpenes and the atmospheric implications will be explored.

  14. Theoretical elucidation of the mechanism of the cycloaddition between nitrone ylides and electron-deficient alkenes.

    PubMed

    Merino, P; Tejero, T; Díez-Martínez, A

    2014-03-07

    A full theoretical study of the reaction between a novel type of ylide, i.e. nitrone ylides, and alkenes has been carried out. Both concerted and polar stepwise mechanisms have been considered. Only the zwitterionic mechanism predicts correctly the experimentally observed adducts. Depending on the level of theory, the mechanism moves from concerted to polar stepwise, as demonstrated by the corresponding IRC analyses. The regio- and stereoselectivity of the reaction is well explained for both mono- and disubstituted alkenes. In the case of methyl acrylate a pathway leading to the two diastereoisomers obtained experimentally is predicted. For methyl fumarate a stereospecific mechanism is predicted as a consequence of a C-H···O═C interaction present in a Li-tricoordinated transition structure. The stereospecificity in the reaction with methyl maleate comes from a less hindered coordination around the lithium atom. Calculations with B3LYP and M06-2X functionals indicate that only the latter provides energy values in good agreement with experimental findings.

  15. Liquefaction with microencapsulated catalysts

    DOEpatents

    Weller, Sol W.

    1985-01-01

    A method of dispersing a liquefaction catalyst within coal or other carbonaceous solids involves providing a suspension in oil of microcapsules containing the catalyst. An aqueous solution of a catalytic metal salt is emulsified in the water-immiscible oil and the resulting minute droplets microencapsulated in polymeric shells by interfacial polycondensation. The catalyst is subsequently blended and dispersed throughout the powdered carbonaceous material to be liquefied. At liquefaction temperatures the polymeric microcapsules are destroyed and the catalyst converted to minute crystallites in intimate contact with the carbonaceous material.

  16. Polyolefin catalyst manufacturing

    SciTech Connect

    Inkrott, K.E.; Scinta, J.; Smith, P.D. )

    1989-10-16

    Statistical process control (SPC) procedures are absolutely essential for making new-generation polyolefin catalysts with the consistent high quality required by modern polyolefin processes. Stringent quality assurance is critical to the production of today's high-performance catalysts. Research and development efforts during the last 20 years have led to major technological improvements in the polyolefin industry. New generation catalysts, which once were laboratory curiosities, must now be produced commercially on a regular and consistent basis to meet the increasing requirements of the plastics manufacturing industry. To illustrate the more stringent requirements for producing the new generation polyolefin catalysts, the authors compare the relatively simple, first-generation polypropylene catalyst production requirements with some of the basic requirements of manufacturing a more complex new-generation catalyst, such as Catalyst Resources Inc.'s LYNX 900. The principles which hold true for the new-generation catalysts such as LYNX 900 are shown to apply equally to the scale-up of other advanced technology polyolefin catalysts.

  17. METHOD OF PURIFYING CATALYSTS

    DOEpatents

    Joris, G.G.

    1958-09-01

    It has been fuund that the presence of chlorine as an impurity adversely affects the performance of finely divided platinum catalysts such as are used in the isotopic exchange process for the production of beavy water. This chlorine impurity may be removed from these catalysts by treating the catalyst at an elevated temperature with dry hydrogen and then with wet hydrogen, having a hydrogen-water vapor volume of about 8: 1. This alternate treatment by dry hydrogen and wet hydrogen is continued until the chlorine is largely removed from the catalyst.

  18. Anaerobic oxidation of n-alkenes by sulphate-reducing bacteria from the genus Desulfatiferula: n-ketones as potential metabolites.

    PubMed

    Grossi, Vincent; Cravo-Laureau, Cristiana; Rontani, Jean-François; Cros, Magali; Hirschler-Réa, Agnès

    2011-11-01

    Two alkene-degrading sulphate-reducing bacteria from the genus Desulfatiferula (Desulfatiferula olefinivorans strain LM2801(T) and Desulfatiferula sp. strain BE2801) were investigated for their 1-alkene metabolism. Their total cellular fatty acids were predominantly C-even when they were grown on C-even 1-alkene (1-hexadecene), whereas a mixture of fatty acids with C-odd or C-even carbon chains predominated when cells were grown on C-odd 1-alkene (1-pentadecene). This is consistent with the fatty acid composition of other sulphate-reducing strains previously reported to grow on n-alkenes. Linear and 3-OH-fatty acids appear to be the main fatty acids produced by the two Desulfatiferula strains. The analysis of their neutral lipids led to identifying several n-alkanols and n-ketones with the same number of carbon atoms as the alkene growth substrate and with functionality located between C-1 and C-5. Growth of strains LM2801(T) and BE2801 on (per) deuterated 1-alkenes provided direct evidence of their anaerobic transformation to corresponding 1-alkanols, n-ketones and linear (3-OH-) fatty acids. These results demonstrate that Desulfatiferula strains oxidize a 1-alkene by oxidation of the double bond at C-1, but also at C-2 to C-5 (after eventual isomerization of the double bond) yielding the corresponding C-2 to C-5 n-ketones (via the corresponding n-alkanols). The formation of specific 3-OH-fatty acids by elongation of shorter chain fatty acids was also demonstrated. Based on our observations, pathways for anaerobic 1-alkene metabolism in sulphate-reducing bacteria from the genus Desulfatiferula are proposed. They indicate that n-ketones can constitute new metabolites of the biodegradation of n-alkenes in anaerobic environments.

  19. A new self-healing epoxy with tungsten (VI) chloride catalyst.

    PubMed

    Kamphaus, Jason M; Rule, Joseph D; Moore, Jeffrey S; Sottos, Nancy R; White, Scott R

    2008-01-06

    Using self-healing materials in commercial applications requires healing chemistry that is cost-effective, widely available and tolerant of moderate temperature excursions. We investigate the use of tungsten (VI) chloride as a catalyst precursor for the ring-opening metathesis polymerization of exo-dicyclopentadiene (exo-DCPD) in self-healing applications as a means to achieve these goals. The environmental stability of WCl6 using three different delivery methods was evaluated and the associated healing performance was assessed following fracture toughness recovery protocols. Both as-received and recrystallized forms of the WCl6 resulted in nearly complete fracture recovery in self-activated tests, where healing agent is manually injected into the crack plane, at 12wt% WCl6 loading. In situ healing using 15wt% microcapsules of the exo-DCPD produced healing efficiencies of approximately 20%.

  20. Single-Component Phosphinous Acid Ruthenium(II) Catalysts for Versatile C-H Activation by Metal-Ligand Cooperation.

    PubMed

    Zell, Daniel; Warratz, Svenja; Gelman, Dmitri; Garden, Simon J; Ackermann, Lutz

    2016-01-22

    Well-defined ruthenium(II) phosphinous acid (PA) complexes enabled chemo-, site-, and diastereoselective C-H functionalization of arenes and alkenes with ample scope. The outstanding catalytic activity was reflected by catalyst loadings as low as 0.75 mol %, and the most step-economical access reported to date to angiotensin II receptor antagonist blockbuster drugs. Mechanistic studies indicated a kinetically relevant C-X cleavage by a single-electron transfer (SET)-type elementary process, and provided evidence for a PA-assisted C-H ruthenation step.