The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
James J. Cregg - One of the best experts on this subject based on the ideXlab platform.
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ruthenium catalyzed Alkene alkyne coupling of disubstituted olefins application to the stereoselective synthesis of trisubstituted enecarbamates
Journal of the American Chemical Society, 2015Co-Authors: Barry M Trost, James J. CreggAbstract:The Ru-catalyzed Alkene–alkyne coupling reaction has been demonstrated to be an enabling methodology for the synthesis of complex molecules. However, to date, it has been limited to monosubstituted olefins. Herein we report the first general utilization of disubstituted olefins in the Ru-catalyzed Alkene–alkyne coupling reaction by employing carbamate directing groups. The products are stereodefined trisusbstituted enecarbamates. The elaboration of these structures toward the asymmetric synthesis of complex aminocyclopentitols and 1,2-amino alcohols is discussed.
Barry M Trost - One of the best experts on this subject based on the ideXlab platform.
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stereocontrolled synthesis of vinyl boronates and vinyl silanes via atom economical ruthenium catalyzed Alkene alkyne coupling
Angewandte Chemie, 2015Co-Authors: Barry M Trost, Dennis C Koester, Alastair N HerronAbstract:The synthesis of vinyl boronates and vinyl silanes was achieved by employing a Ru-catalyzed Alkene–alkyne coupling reaction of allyl boronates or allyl silanes with various alkynes. The double bond geometry in the generated vinyl boronates can be remotely controlled by the juxtaposing boron- and silicon groups on the alkyne substrate. The synthetic utility of the coupling products has been demonstrated in a variety of synthetic transformations, including iterative cross-coupling reactions, and a Chan-Lam-type allyloxylation followed by a Claisen rearrangement. A sequential one-pot Alkene-alkyne-coupling/allylation-sequence with an aldehyde to deliver a highly complex α-silyl-β-hydroxy olefin with a handle for further functionalization was also realized.
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ruthenium catalyzed Alkene alkyne coupling of disubstituted olefins application to the stereoselective synthesis of trisubstituted enecarbamates
Journal of the American Chemical Society, 2015Co-Authors: Barry M Trost, James J. CreggAbstract:The Ru-catalyzed Alkene–alkyne coupling reaction has been demonstrated to be an enabling methodology for the synthesis of complex molecules. However, to date, it has been limited to monosubstituted olefins. Herein we report the first general utilization of disubstituted olefins in the Ru-catalyzed Alkene–alkyne coupling reaction by employing carbamate directing groups. The products are stereodefined trisusbstituted enecarbamates. The elaboration of these structures toward the asymmetric synthesis of complex aminocyclopentitols and 1,2-amino alcohols is discussed.
Freek Kapteijn - One of the best experts on this subject based on the ideXlab platform.
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understanding the anomalous alkane selectivity of zif 7 in the separation of light alkane Alkene mixtures
Chemistry: A European Journal, 2011Co-Authors: Johan Van Den Bergh, Evgeny A Pidko, Emiel J M Hensen, Canan Gucuyener, Jorge Gascon, Freek KapteijnAbstract:C2 and C3 alkanes are selectively adsorbed from mixtures over the corresponding Alkenes on the zeolite imidazolate framework ZIF-7 through a gate-opening mechanism. As a result, the direct production of the pure Alkene upon adsorption and the pure alkane upon desorption in packed columns is possible. Herein, a detailed investigation of the step-wise adsorption and separation of alkanes and Alkenes is presented, together with a rigorous performance assessment. A molecular picture of the gate-opening mechanism underlying the unprecedented selectivity towards alkane adsorption is proposed based on DFT calculations and a thermodynamic analysis of the adsorption–desorption isotherms.
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Understanding the anomalous alkane selectivity of ZIF-7 in the separation of light alkane/Alkene mixtures.
Chemistry: A European Journal, 2011Co-Authors: Johan Van Den Bergh, Evgeny A Pidko, Emiel J M Hensen, Canan Gucuyener, Jorge Gascon, Freek KapteijnAbstract:C2 and C3 alkanes are selectively adsorbed from mixtures over the corresponding Alkenes on the zeolite imidazolate framework ZIF-7 through a gate-opening mechanism. As a result, the direct production of the pure Alkene upon adsorption and the pure alkane upon desorption in packed columns is possible. Herein, a detailed investigation of the step-wise adsorption and separation of alkanes and Alkenes is presented, together with a rigorous performance assessment. A molecular picture of the gate-opening mechanism underlying the unprecedented selectivity towards alkane adsorption is proposed based on DFT calculations and a thermodynamic analysis of the adsorption–desorption isotherms.
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Analysis of gas adsorption in Kureha active carbon based on the slit-pore model and Monte-Carlo simulations
Molecular Simulation, 2006Co-Authors: Nick Quirke, Martin Sweatman, Freek KapteijnAbstract:We analyse the adsorption of carbon dioxide and several light Alkenes and alkanes on Kureha active carbon at a range of temperatures. We find generally good agreement between the Alkene and alkane isotherms at moderate to high pressure, but find that at the lowest relative pressures for each gas there are significant discrepancies that seem to be correlated with the strength of gas – surface interactions. This pattern is similar to that observed in our previous work on the adsorption of light Alkenes and alkanes on active carbon, except the errors here are much smaller. One possible explanation for this error is poor diffusion in the experiments at the lowest relative pressures, leading to measurements of non-equilibrium states. We suggest that this poor diffusion might be caused by potential barriers (i.e. it is activated diffusion) in the narrowest pores. We also find that our analysis of the adsorption of carbon dioxide at 273 K is inconsistent with all the Alkene and alkane data. We suggest this discrepancy arises because our model of gas – surface interactions does not take contributions from polar surface sites into account. Although this study is specific to Kureha active carbon, we expect that our conclusions are relevant to other studies of gas adsorption on active carbon; they highlight the need for great care when taking measurements at low pressures, and motivate improvements in molecular models for gas adsorption in active carbons.
Pierre H.dixneuf - One of the best experts on this subject based on the ideXlab platform.
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Early Steps of Homogeneous Catalysis in Rennes: Carbon Dioxide Incorporation, Alkyne Activation and Ruthenium Catalysis
Catalysis Letters, 2015Co-Authors: Pierre H.dixneufAbstract:This review reports the first discoveries in homogeneous catalysis in Rennes. Ruthenium(II) catalysts are shown to promote the activation of terminal alkynes and the synthesis of vinylcarbamates on addition of CO2 and amines. The ruthenium–vinylidene are the key catalytic species. Applications to the addition of carboxylic acids to alkynes have opened the access to various enolesters and dienylesters via controlled catalyzed Markovnikov or anti-Markonikov additions. The catalytic synthesis of α-methylene cyclic carbonates and oxazolidinones from propargylic alcohols and CO2 is presented and shown to lead to allene derivatives via palladium catalysis. Cp*RuX(COD) catalyst promote the head to tail oxidative couplings of Alkene with alkyne, and the synthesis of functional dienes via 1,4 addition of H-nucleophiles to the biscarbene-ruthenium intermediate arising from head to head couplings of alkynes, whereas Cp*RuL2 + catalysts favour activation of alkynes via vinylidene intermediate.
Issam Hanna - One of the best experts on this subject based on the ideXlab platform.
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Substituent effects in tandem ring-closing metathesis reactions of dienynes
European Journal of Organic Chemistry, 2006Co-Authors: François-didier Boyer, Issam HannaAbstract:Several dienynes bearing different substituents have been synthesized and subjected to a ring-closing metathesis (RCM) reaction using ruthenium carbene complexes. Dienynes containing a pre-existing ring and a quaternary center attached to the alkyne give the expected tandem metathesis products in high yields. For these substrates, a high selectivity for different ring sizes was achieved by modifying the reactivity of one Alkene. In one case, an unusual non-metathetic activity of the second-generation Grubbs catalyst was observed and the cycloisomerization product was obtained as the major product. In the absence of favorable factors, especially when the starting substrates contain hindered Alkenes, a long tether chain and/or an ester group on the alkyne part, the tandem process is slowed down or completely impeded. In these cases, dienynes behave like simple enynes and afford initial metathesis products whose further reactions give dimeric compounds. © Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
