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Christophe Michon - One of the best experts on this subject based on the ideXlab platform.
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One-pot controlled reduction of conjugated amides by sequential double Hydrosilylation catalyzed by an iridium(III) metallacycle
European Journal of Organic Chemistry, 2020Co-Authors: Yann Corre, Vincent Rysak, Márton Nagyházi, Dorottya Kalocsai, Xavier Trivelli, Jean-pierre Djukic, Francine Agbossou-niedercorn, Christophe MichonAbstract:A single and accessible cationic iridium III metallacycle catalyzes effectively the one-pot sequential double Hydrosilylation of challenging -unsaturated secondary and tertiary amides to afford in a controlled and straightforward way the corresponding reduced products, that is to say the related secondary and tertiary amides and amines. The catalytic Hydrosilylations of the conjugated amides described herein proceeded in good yields and high chemoselectivities. The critical silyl enolate, in other words silyl ketene aminal intermediate, has been observed and characterized by using control experiments, mass spectrometry and state of the art Nuclear Magnetic Resonance analyses. The present achievements indicate a promising potential of catalysts based on metallacycles for future significant developments in one-pot multicatalytic synthesis and therefore the production of highly functionalized and complex organic molecules.
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A Versatile Iridium(III) Metallacycle Catalyst for the Effective Hydrosilylation of Carbonyl and Carboxylic Acid Derivatives
European Journal of Organic Chemistry, 2017Co-Authors: Yann Corre, Vincent Rysak, Xavier Trivelli, Francine Agbossou-niedercorn, Christophe MichonAbstract:A versatile iridium(III) metallacycle catalyses rapidly and selectively the reduction of a large array of challenging esters and carboxylic acids as well as various ketones and aldehydes. Reactions proceed with high yields at room temperature through Hydrosilylation followed by desilylation. Whether the reaction of various aldehydes and ketones results exclusively in alcohols, the Hydrosilylation of esters leads to alcohols or ethers depending on the type of substrate. Regarding the carboxylic acids, the nature of the reagent controls also the outcome of the Hydrosilylation reaction, either alcohols or aldehydes being formed.
Maurice Brookhart - One of the best experts on this subject based on the ideXlab platform.
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Hydrosilylation of epoxides catalyzed by a cationic η1 silane iridium iii complex
Chemical Communications, 2011Co-Authors: Sehoon Park, Maurice BrookhartAbstract:Cationic silane complex 2, catalyzes the Hydrosilylation of epoxides and cyclic ethers to give the silyl-protected alcohols, regioselectively. A mechanistic study shows that the epoxide undergoes isomerization to the ketone, followed by Hydrosilylation.
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Hydrosilylation of carbonyl containing substrates catalyzed by an electrophilic η1 silane iridium iii complex
Organometallics, 2010Co-Authors: Sehoon Park, Maurice BrookhartAbstract:Hydrosilylation of a variety of ketones and aldehydes using the cationic iridium catalyst (POCOP)Ir(H)(acetone)+, 1 (POCOP = 2,6-bis(di-tert-butylphosphinito)phenyl), is reported. With triethyl silane, all but exceptionally bulky ketones undergo quantitative reactions employing 0.5 mol % catalyst in 20−30 min at 25 °C. Hydrosilylation of esters and amides results in over-reduction and cleavage of C−O and C−N bonds, respectively. The diastereoselectivity of Hydrosilylation of 4-tert-butyl cyclohexanone has been examined using numerous silanes and is highly temperature dependent. Using EtMe2SiH, analysis of the ratio of cis:trans Hydrosilylation products as a function of temperature yields values for ΔΔH‡ (ΔH‡(trans) − ΔH‡(cis)) and ΔΔS‡ (ΔS‡(trans) − ΔS‡(cis)) of −2.5 kcal/mol and −6.9 eu, respectively. Mechanistic studies show that the ketone complex (POCOP)Ir(H)(ketone)+ is the catalyst resting state and is in equilibrium with low concentration of the silane complex (POCOP)Ir(H)(HSiR3)+. The silane compl...
Martin Oestreich - One of the best experts on this subject based on the ideXlab platform.
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Transfer Hydrosilylation.
Angewandte Chemie (International ed. in English), 2015Co-Authors: Martin OestreichAbstract:Transfer hydrogenation is without question a common technology in industry and academia. Unlike its countless varieties, conceptually related transfer Hydrosilylations had essentially been unreported until the recent development of a radical and an ionic variant. The new methods are both based on a silicon-substituted cyclohexa-1,4-diene and hinge on the aromatization of the corresponding cyclohexadienyl radical and cation intermediates, respectively, concomitant with homo- or heterolytic fission of the Si-C bond. Both the radical and ionic transfer Hydrosilylation are brought into context with one other in this Minireview, and early insight into the possibility of transfer Hydrosilylation is included. Although the current state-of-the-art is certainly still limited, the recent advances have already revealed the promising potential of transfer Hydrosilylation.
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Formal SiH_4 chemistry using stable and easy-to-handle surrogates
Nature Chemistry, 2015Co-Authors: Antoine Simonneau, Martin OestreichAbstract:Monosilane (SiH_4) is far less well behaved than its carbon analogue methane (CH_4). It is a colourless gas that is industrially relevant as a source of elemental silicon, but its pyrophoric and explosive nature makes its handling and use challenging. Consequently, synthetic applications of SiH_4 in academic laboratories are extremely rare and methodologies based on SiH_4 are underdeveloped. Safe and controlled alternatives to the substituent redistribution approaches of hydrosilanes are desirable and cyclohexa-2,5-dien-1-ylsilanes where the cyclohexa-1,4-diene units serve as placeholders for the hydrogen atoms have been identified as potent surrogates of SiH_4. We disclose here that the commercially available Lewis acid tris(pentafluorophenyl)borane, B(C_6F_5)_3, is able to promote the release of the Si–H bond catalytically while subsequently enabling the Hydrosilylation of C–C multiple bonds in the same pot. The net reactions are transition-metal-free transfer Hydrosilylations with SiH_4 as a building block for the preparation of various hydrosilanes. Cyclohexa-2,5-dien-1-yl groups bound to silicon act as masked Si–H bonds that can be released by the action of tris(pentafluorophenyl)borane (B(C_6F_5)_3). In this way, hazardous SiH_4 is unleashed from appropriately substituted precursors and engages in alkene Hydrosilylation promoted by the same boron catalyst. The overall process is a transfer Hydrosilylation of alkenes with monosilane.
Yann Corre - One of the best experts on this subject based on the ideXlab platform.
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One-pot controlled reduction of conjugated amides by sequential double Hydrosilylation catalyzed by an iridium(III) metallacycle
European Journal of Organic Chemistry, 2020Co-Authors: Yann Corre, Vincent Rysak, Márton Nagyházi, Dorottya Kalocsai, Xavier Trivelli, Jean-pierre Djukic, Francine Agbossou-niedercorn, Christophe MichonAbstract:A single and accessible cationic iridium III metallacycle catalyzes effectively the one-pot sequential double Hydrosilylation of challenging -unsaturated secondary and tertiary amides to afford in a controlled and straightforward way the corresponding reduced products, that is to say the related secondary and tertiary amides and amines. The catalytic Hydrosilylations of the conjugated amides described herein proceeded in good yields and high chemoselectivities. The critical silyl enolate, in other words silyl ketene aminal intermediate, has been observed and characterized by using control experiments, mass spectrometry and state of the art Nuclear Magnetic Resonance analyses. The present achievements indicate a promising potential of catalysts based on metallacycles for future significant developments in one-pot multicatalytic synthesis and therefore the production of highly functionalized and complex organic molecules.
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A Versatile Iridium(III) Metallacycle Catalyst for the Effective Hydrosilylation of Carbonyl and Carboxylic Acid Derivatives
European Journal of Organic Chemistry, 2017Co-Authors: Yann Corre, Vincent Rysak, Xavier Trivelli, Francine Agbossou-niedercorn, Christophe MichonAbstract:A versatile iridium(III) metallacycle catalyses rapidly and selectively the reduction of a large array of challenging esters and carboxylic acids as well as various ketones and aldehydes. Reactions proceed with high yields at room temperature through Hydrosilylation followed by desilylation. Whether the reaction of various aldehydes and ketones results exclusively in alcohols, the Hydrosilylation of esters leads to alcohols or ethers depending on the type of substrate. Regarding the carboxylic acids, the nature of the reagent controls also the outcome of the Hydrosilylation reaction, either alcohols or aldehydes being formed.
Sehoon Park - One of the best experts on this subject based on the ideXlab platform.
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Hydrosilylation of epoxides catalyzed by a cationic η1 silane iridium iii complex
Chemical Communications, 2011Co-Authors: Sehoon Park, Maurice BrookhartAbstract:Cationic silane complex 2, catalyzes the Hydrosilylation of epoxides and cyclic ethers to give the silyl-protected alcohols, regioselectively. A mechanistic study shows that the epoxide undergoes isomerization to the ketone, followed by Hydrosilylation.
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Hydrosilylation of carbonyl containing substrates catalyzed by an electrophilic η1 silane iridium iii complex
Organometallics, 2010Co-Authors: Sehoon Park, Maurice BrookhartAbstract:Hydrosilylation of a variety of ketones and aldehydes using the cationic iridium catalyst (POCOP)Ir(H)(acetone)+, 1 (POCOP = 2,6-bis(di-tert-butylphosphinito)phenyl), is reported. With triethyl silane, all but exceptionally bulky ketones undergo quantitative reactions employing 0.5 mol % catalyst in 20−30 min at 25 °C. Hydrosilylation of esters and amides results in over-reduction and cleavage of C−O and C−N bonds, respectively. The diastereoselectivity of Hydrosilylation of 4-tert-butyl cyclohexanone has been examined using numerous silanes and is highly temperature dependent. Using EtMe2SiH, analysis of the ratio of cis:trans Hydrosilylation products as a function of temperature yields values for ΔΔH‡ (ΔH‡(trans) − ΔH‡(cis)) and ΔΔS‡ (ΔS‡(trans) − ΔS‡(cis)) of −2.5 kcal/mol and −6.9 eu, respectively. Mechanistic studies show that the ketone complex (POCOP)Ir(H)(ketone)+ is the catalyst resting state and is in equilibrium with low concentration of the silane complex (POCOP)Ir(H)(HSiR3)+. The silane compl...
