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Zhiping Yin - One of the best experts on this subject based on the ideXlab platform.
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sakurai reaction of 3 3 bis Silyl Silyl enol ethers with acetals involving selective deSilylation of the geminal bis silane concise synthesis of nematocidal oxylipid
ChemInform, 2013Co-Authors: Lu Gao, Zhenlei Song, Zhiping YinAbstract:The Lewis acid-promoted reaction of 3,3-bis(Silyl) Silyl enol ethers with various acetals is studied.
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sakurai reaction of 3 3 bis Silyl Silyl enol ethers with acetals involving selective deSilylation of the geminal bis silane concise synthesis of nematocidal oxylipid
Organic Letters, 2013Co-Authors: Lu Gao, Zhenlei Song, Zhiping YinAbstract:3,3-Bis(Silyl) Silyl enol ethers have been shown to exhibit predominantly Sakurai reactivity, rather than Mukaiyama aldol reactivity, in their Lewis acid promoted reactions with acetals. Starting from a geminal bis(Silyl) moiety consisting of two different Silyl groups, such as SiMe3 and SiMe2Ph, the SiMe3 is selectively eliminated to give monoprotected E- vinylSilyl diols with good to excellent syn-diastereoselectivity. This reaction also underpinned a synthesis of the nematocidal oxylipid from Notheia anomala, demonstrating the attractive bifunctionality of geminal bis(silanes).
Gilles Pierre - One of the best experts on this subject based on the ideXlab platform.
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SmI2 induced cross coupling of nitrones and Silyl acrylates : synthesis of polyhydroxylated pyrrolidines
2011Co-Authors: Gilles PierreAbstract:Les nitrones peuvent être réduites par le diiodure de samarium et réagir selon une additionconjuguée avec des acrylates-Silylés, Silylés ou ,diSilylés. Ce couplage réducteur,développé avec des aldonitrones simples, a conduit à des dérivés Silylés de g-Nhydroxyaminoacides.Ces derniers ont pu être réduits puis cyclisés en g-lactames substituéspar un groupement Silylé, dont la position et la configuration dépendent de l’acrylate dedépart. L’oxydation de Tamao-Fleming a ensuite permis la conversion des composés Silylésen leurs correspondants hydroxylés avec rétention de configuration. Cet enchaînementréactionnel a alors été appliquée à une nitrone cyclique polyalkoxylée dérivée du L-xylose, cequi a permis les synthèses de la 7-desoxy Uniflorine A et de la (+)-Australine, deuxpyrrolizidines polyhydroxylées inhibiteurs de glucosidases.Nitrones are reduced by samarium diiodide and react through a conjugated addition with Silylacrylates. This cross coupling, developed with simple aldonitrones, allowed the preparation ofSilyl g-N-hydroxyaminoacids derivatives. The latter were reduced and cyclised in g-lactams inwhich the position and the configuration of the Silyl group depend of the starting acrylate.Tamao-Fleming oxidation was used for the conversion of Silyl group to hydroxyl group withretention of configuration. Then, the reaction was applied to a cyclic polyalkoxy nitronederived from L-xylose and it allowed the synthesis of 7-deoxy Uniflorine A and (+)-Australine, polyhydroxylated pyrrolizidines exhibiting glucosidases inhibition
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Couplage croisé induit par SmI2 de nitrones avec des acrylates Silylés : synthèse de Pyrrolizidines polyhydroxylées
HAL CCSD, 2011Co-Authors: Gilles PierreAbstract:Nitrones are reduced by samarium diiodide and react through a conjugated addition with Silylacrylates. This cross coupling, developed with simple aldonitrones, allowed the preparation ofSilyl g-N-hydroxyaminoacids derivatives. The latter were reduced and cyclised in g-lactams inwhich the position and the configuration of the Silyl group depend of the starting acrylate.Tamao-Fleming oxidation was used for the conversion of Silyl group to hydroxyl group withretention of configuration. Then, the reaction was applied to a cyclic polyalkoxy nitronederived from L-xylose and it allowed the synthesis of 7-deoxy Uniflorine A and (+)-Australine, polyhydroxylated pyrrolizidines exhibiting glucosidases inhibition.Les nitrones peuvent être réduites par le diiodure de samarium et réagir selon une additionconjuguée avec des acrylates-Silylés, Silylés ou ,diSilylés. Ce couplage réducteur,développé avec des aldonitrones simples, a conduit à des dérivés Silylés de g-Nhydroxyaminoacides.Ces derniers ont pu être réduits puis cyclisés en g-lactames substituéspar un groupement Silylé, dont la position et la configuration dépendent de l’acrylate dedépart. L’oxydation de Tamao-Fleming a ensuite permis la conversion des composés Silylésen leurs correspondants hydroxylés avec rétention de configuration. Cet enchaînementréactionnel a alors été appliquée à une nitrone cyclique polyalkoxylée dérivée du L-xylose, cequi a permis les synthèses de la 7-desoxy Uniflorine A et de la (+)-Australine, deuxpyrrolizidines polyhydroxylées inhibiteurs de glucosidases
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Couplage croisé induit par SmI2 de nitrones avec des acrylates Silylés. Synthèse de Pyrrolizidines polyhydroxylées
2011Co-Authors: Gilles Pierre, Py SandrineAbstract:Les nitrones peuvent être réduites par le diiodure de samarium et réagir selon une additionconjuguée avec des acrylates-Silylés, Silylés ou ,diSilylés. Ce couplage réducteur,développé avec des aldonitrones simples, a conduit à des dérivés Silylés de g-Nhydroxyaminoacides.Ces derniers ont pu être réduits puis cyclisés en g-lactames substituéspar un groupement Silylé, dont la position et la configuration dépendent de l acrylate dedépart. L oxydation de Tamao-Fleming a ensuite permis la conversion des composés Silylésen leurs correspondants hydroxylés avec rétention de configuration. Cet enchaînementréactionnel a alors été appliquée à une nitrone cyclique polyalkoxylée dérivée du L-xylose, cequi a permis les synthèses de la 7-desoxy Uniflorine A et de la (+)-Australine, deuxpyrrolizidines polyhydroxylées inhibiteurs de glucosidases.Nitrones are reduced by samarium diiodide and react through a conjugated addition with Silylacrylates. This cross coupling, developed with simple aldonitrones, allowed the preparation ofSilyl g-N-hydroxyaminoacids derivatives. The latter were reduced and cyclised in g-lactams inwhich the position and the configuration of the Silyl group depend of the starting acrylate.Tamao-Fleming oxidation was used for the conversion of Silyl group to hydroxyl group withretention of configuration. Then, the reaction was applied to a cyclic polyalkoxy nitronederived from L-xylose and it allowed the synthesis of 7-deoxy Uniflorine A and (+)-Australine, polyhydroxylated pyrrolizidines exhibiting glucosidases inhibition.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF
Lu Gao - One of the best experts on this subject based on the ideXlab platform.
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sakurai reaction of 3 3 bis Silyl Silyl enol ethers with acetals involving selective deSilylation of the geminal bis silane concise synthesis of nematocidal oxylipid
ChemInform, 2013Co-Authors: Lu Gao, Zhenlei Song, Zhiping YinAbstract:The Lewis acid-promoted reaction of 3,3-bis(Silyl) Silyl enol ethers with various acetals is studied.
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sakurai reaction of 3 3 bis Silyl Silyl enol ethers with acetals involving selective deSilylation of the geminal bis silane concise synthesis of nematocidal oxylipid
Organic Letters, 2013Co-Authors: Lu Gao, Zhenlei Song, Zhiping YinAbstract:3,3-Bis(Silyl) Silyl enol ethers have been shown to exhibit predominantly Sakurai reactivity, rather than Mukaiyama aldol reactivity, in their Lewis acid promoted reactions with acetals. Starting from a geminal bis(Silyl) moiety consisting of two different Silyl groups, such as SiMe3 and SiMe2Ph, the SiMe3 is selectively eliminated to give monoprotected E- vinylSilyl diols with good to excellent syn-diastereoselectivity. This reaction also underpinned a synthesis of the nematocidal oxylipid from Notheia anomala, demonstrating the attractive bifunctionality of geminal bis(silanes).
Yujiro Hayashi - One of the best experts on this subject based on the ideXlab platform.
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amphiphilic immobilized diphenylprolinol alkyl ether catalyst on ps peg resin
Bulletin of the Chemical Society of Japan, 2021Co-Authors: Seitaro Koshino, Shusuke Hattori, Shota Hasegawa, Naoki Haraguchi, Takeshi Yamamoto, Michinori Suginome, Yasuhiro Uozumi, Yujiro HayashiAbstract:Diphenylprolinol Silyl ether is a widely used organocatalyst, and its immobilization on a solid support was investigated for the easy recycling and reuse of this catalyst. Because a Silyl ether bon...
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Two Reaction Mechanisms via Iminium Ion Intermediates: The Different Reactivities of Diphenylprolinol Silyl Ether and Trifluoromethyl-Substituted Diarylprolinol Silyl Ether.
Chemistry (Weinheim an der Bergstrasse Germany), 2015Co-Authors: Hiroaki Gotoh, Tadafumi Uchimaru, Yujiro HayashiAbstract:The reactions of α,β-unsaturated aldehydes with cyclopentadiene in the presence of diarylprolinol Silyl ethers as catalyst proceed via iminium cations as intermediates, and can be divided into two types; one involving a Michael-type reaction (type A) and one involving a cycloaddition (type B). Diphenylprolinol Silyl ethers and trifluoromethyl-substituted diarylprolinol Silyl ethers, which are widely used proline-type organocatalysts, have been investigated in this study. As the LUMO of the iminium ion derived from trifluoromethyl-substituted diarylprolinol Silyl ether is lower in energy than that derived from diphenylprolinol Silyl ether, as supported by ab initio calculations, the trifluoromethyl-substituted catalyst is more reactive in a type B reaction. The iminium ion from an α,β-unsaturated aldehyde is generated more quickly with diphenylprolinol Silyl ether than with the trifluoromethyl-substituted diarylprolinol Silyl ether. When the generation of the iminium ion is the rate-determining step, the diphenylprolinol Silyl ether catalyst is the more reactive. Because acid accelerates the generation of iminium ions and reduces the generation of anionic nucleophiles in the Michael-type reaction (type A), it is necessary to select the appropriate acid for specific reactions. In general, diphenylprolinol Silyl ether is a superior catalyst for type A reactions, whereas the trifluoromethyl-substituted diarylprolinol Silyl ether catalyst is preferred for type B reactions.
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a theoretical and experimental study of the effects of Silyl substituents in enantioselective reactions catalyzed by diphenylprolinol Silyl ether
Chemistry: A European Journal, 2014Co-Authors: Hiroaki Gotoh, Tadafumi Uchimaru, Yujiro Hayashi, Daichi Okamura, Tatsuya Yamazaki, Yasuto Ameda, Seiji Tsuzuki, Dieter SeebachAbstract:The effect of Silyl substituents in diphenylprolinol Silyl ether catalysts was investigated. Mechanistically, reactions catalyzed by diphenylprolinol Silyl ether can be categorized into three types: two that involve an iminium ion intermediate, such as for the Michael-type reaction (type A) and the cycloaddition reaction (type B), and one that proceeds via an enamine intermediate (type C). In the Michael-type reaction via iminium ions (type A), excellent enantioselectivity is realized when the catalyst with a bulky Silyl moiety is employed, in which efficient shielding of a diastereotopic face of the iminium ion is directed by the bulky Silyl moiety. In the cycloaddition reaction of iminium ions (type B) and reactions via enamines (type C), excellent enantioselectivity is obtained even when the Silyl group is less bulky and, in this case, too much bulk reduces the reaction rate. In other cases, the yield increases when diphenylprolinol Silyl ethers with bulky substituents are employed, presumably by suppressing side reactions between the nucleophilic catalyst and the reagent. The conformational behaviors of the iminium and enamine species have been determined by theoretical calculations. These data explain the effect of the bulkiness of the Silyl substituent on the enantioselectivity and reactivity of the catalysts.
Dennis Russowsky - One of the best experts on this subject based on the ideXlab platform.
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Adição de nucleofilos de carbono a ions iminio e aciliminio : sintese de B-aminocetonas e enantiosseletiva da base necinica (+) - hastanecina
2017Co-Authors: Dennis RussowskyAbstract:Resumo: As b-aminocetonas 50-58 e 67-70 foram preparadas em 35-80% de rendimento através da adição de silil enoléteres à ions imínio gerados a partir das iminas (bases de Schiff) correspondentes ativadas por 15% moI de TMSOTf ou por quantidades catalíticas de ácidos de Lewis (Cp2BOTf, BF3 OEt2, Me2AlCI ou TiC4). A proporção diastereoisomérica das b- aminocetonas mostrou-se dependente das condições da reação: à - 78°C, com catálise de TMSOTf ou Cp2BOTf, predominou a formação dos isômeros SYN (ed= 0-66%) enquanto que à O°C ou temperatura ambiente os isômeros ANTI (ed= 0-60%) foram produzidos majoritariamente. A adição de enolatos acíclicos de lítio e titânio com geometria Z levaram à obtenção preferencial das b-aminocetonas de configuração relativa ANTI (ed= 20- 100% e 34-64%, respectivamente) enquanto que enolatos cíclicos (geometria E) forneceram majoritariamente as b-aminocetonas configuração relativa SYN (ed= 0-46%). A adição de enolatos de boro à iminas levaram, em um único caso, à obtenção da b-aminocetona desejada. Todavia, esta reação pode ser alcançada utilizando a imina previamente ativada com n- Bu2 BOTf: os isômeros de configuração relativa ANTI foram sempre predominantes independentemente da geometria do enolato ou da temperatura da reação. A adição dos silil enoléteres 249 e 250 ao íon N-aciliminio 223, gerado a partir da aciloxilactama correspondente 235 e 15% mol de TMSOTf, forneceu as lactamas TRANS, 251 e 253 (68-73%) com boa ou excelente estereosseletividade facial (70-100%). O emprego do silil cetenoacetal 255b e dos silil cetenotioacetais 253 e 257 nas reações com o íon N-acilimínio 223 forneceram exclusivamente os respectivos adutos TRANS, 254, 256, 258 (seletividade facial) mas não permitiu controlar a estereoquímica do centro assimétrico C-6 da cadeia lateral. O emprego do enolato de boro quiral 259 na reação com o íon N-acilimínio quiral 223 (derivado do ácido S-málico) promovida por n.Bu2BOTf, permitiu obter o aduto (-)-260 como um único isômero em 53% de rendimento. A estereoquímica absoluta 4S, 5R, 6R foi estabelecida através da sua transformação na base necínica (+ )-hastanecina (193, 8 etapas, 3,5% de rendimento total).Abstract: b-aminoketones 50-58 and 67-70 were prepared in 35-80% yield through the addition of sililenolethers to iminiun ions generated from the corresponding imines (Schiff bases) and 15% mol of TMSOTf or catalytic amount of Lewis acid (Cp2BOTf, BF3 OEt2, Me2AlCI ou TiC4). The diastereoisomeric ratio of the b-aminoketones proved to be dependent on the reaction conditions: at -78°C and TMSOTf or Cp2BOTf, the SYN isomer predominated (de=0-66%) while at 0°C or room temperature the ANTI isomer was the major one (de=0-60%). The addition of acyclic lithium and titaniun enolates of Z configuration led to ANTI-b-aminoketones preferentially (de=20-100% and 34-64%, respectively) while cyclic lithiurn enolates (E configuration) afforded the SYN isomer as the major b-aminoketone (de=046%). The addition of boron enolates to Schiff bases led, in one case, to the isolation of b-aminoketone. However it could be carried out when the imine was previously activated with n-Bu2BOTf: the ANTI isomer predominated (de=0-32%) regardless the enolate configuration and the reaction temperature. The addition of Silyl enolethers 249 and 250 to N-acyliminium ion 223,generated from the corresponding a-acyloxylactam 235 and 15% moI of TMSOTf, afforded the TRANS-lactams 251 and 251 (68-73% yield) with good to excellent facial selectivity (70-100%). When Silyl keteneacetals 255b and Silyl ketenethioacetals 253 and 257 were employed TRANS adducts 254, 256, 258 were exclusively formed (facial selectivity) but without stereochemical control of stereogenic center at C-6 on the side chain. When chiral boron enolate 259 was employed in the reaction with chiral N-acyliminiurn ion 223 (derived from S-malic acid) promoted by n-Bu2BOTf, the chiral adduct (-)-260 was obtained as a single product in 53% yield. Its 4S, 5R, 6R configuration was established after its conversion to the necinic base (+)- hastanecine (193, 8 steps, 3,5% overal] yield)
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Adição de nucleofilos de carbono a ions iminio e aciliminio : sintese de B-aminocetonas e enantiosseletiva da base necinica (+) - hastanecina
Universidade Estadual de Campinas . Instituto de Quimica, 1995Co-Authors: Dennis RussowskyAbstract:As b-aminocetonas 50-58 e 67-70 foram preparadas em 35-80% de rendimento através da adição de silil enoléteres à ions imínio gerados a partir das iminas (bases de Schiff) correspondentes ativadas por 15% moI de TMSOTf ou por quantidades catalíticas de ácidos de Lewis (Cp2BOTf, BF3 OEt2, Me2AlCI ou TiC4). A proporção diastereoisomérica das b- aminocetonas mostrou-se dependente das condições da reação: à - 78°C, com catálise de TMSOTf ou Cp2BOTf, predominou a formação dos isômeros SYN (ed= 0-66%) enquanto que à O°C ou temperatura ambiente os isômeros ANTI (ed= 0-60%) foram produzidos majoritariamente. A adição de enolatos acíclicos de lítio e titânio com geometria Z levaram à obtenção preferencial das b-aminocetonas de configuração relativa ANTI (ed= 20- 100% e 34-64%, respectivamente) enquanto que enolatos cíclicos (geometria E) forneceram majoritariamente as b-aminocetonas configuração relativa SYN (ed= 0-46%). A adição de enolatos de boro à iminas levaram, em um único caso, à obtenção da b-aminocetona desejada. Todavia, esta reação pode ser alcançada utilizando a imina previamente ativada com n- Bu2 BOTf: os isômeros de configuração relativa ANTI foram sempre predominantes independentemente da geometria do enolato ou da temperatura da reação. A adição dos silil enoléteres 249 e 250 ao íon N-aciliminio 223, gerado a partir da aciloxilactama correspondente 235 e 15% mol de TMSOTf, forneceu as lactamas TRANS, 251 e 253 (68-73%) com boa ou excelente estereosseletividade facial (70-100%). O emprego do silil cetenoacetal 255b e dos silil cetenotioacetais 253 e 257 nas reações com o íon N-acilimínio 223 forneceram exclusivamente os respectivos adutos TRANS, 254, 256, 258 (seletividade facial) mas não permitiu controlar a estereoquímica do centro assimétrico C-6 da cadeia lateral. O emprego do enolato de boro quiral 259 na reação com o íon N-acilimínio quiral 223 (derivado do ácido S-málico) promovida por n.Bu2BOTf, permitiu obter o aduto (-)-260 como um único isômero em 53% de rendimento. A estereoquímica absoluta 4S, 5R, 6R foi estabelecida através da sua transformação na base necínica (+ )-hastanecina (193, 8 etapas, 3,5% de rendimento total).b-aminoketones 50-58 and 67-70 were prepared in 35-80% yield through the addition of sililenolethers to iminiun ions generated from the corresponding imines (Schiff bases) and 15% mol of TMSOTf or catalytic amount of Lewis acid (Cp2BOTf, BF3 OEt2, Me2AlCI ou TiC4). The diastereoisomeric ratio of the b-aminoketones proved to be dependent on the reaction conditions: at -78°C and TMSOTf or Cp2BOTf, the SYN isomer predominated (de=0-66%) while at 0°C or room temperature the ANTI isomer was the major one (de=0-60%). The addition of acyclic lithium and titaniun enolates of Z configuration led to ANTI-b-aminoketones preferentially (de=20-100% and 34-64%, respectively) while cyclic lithiurn enolates (E configuration) afforded the SYN isomer as the major b-aminoketone (de=046%). The addition of boron enolates to Schiff bases led, in one case, to the isolation of b-aminoketone. However it could be carried out when the imine was previously activated with n-Bu2BOTf: the ANTI isomer predominated (de=0-32%) regardless the enolate configuration and the reaction temperature. The addition of Silyl enolethers 249 and 250 to N-acyliminium ion 223,generated from the corresponding a-acyloxylactam 235 and 15% moI of TMSOTf, afforded the TRANS-lactams 251 and 251 (68-73% yield) with good to excellent facial selectivity (70-100%). When Silyl keteneacetals 255b and Silyl ketenethioacetals 253 and 257 were employed TRANS adducts 254, 256, 258 were exclusively formed (facial selectivity) but without stereochemical control of stereogenic center at C-6 on the side chain. When chiral boron enolate 259 was employed in the reaction with chiral N-acyliminiurn ion 223 (derived from S-malic acid) promoted by n-Bu2BOTf, the chiral adduct (-)-260 was obtained as a single product in 53% yield. Its 4S, 5R, 6R configuration was established after its conversion to the necinic base (+)- hastanecine (193, 8 steps, 3,5% overal] yield)
