Catalytic Asymmetric Addition of Polyfunctional Dialkylzincs to .beta.-Stannylated and .beta.-Silylated Unsaturated Aldehydes
摘要:
The addition of functionalized dialkylzincs to readily available beta-stannylated or beta-silylated unsaturated aldehydes in the presence of a catalytic amount of (1R,2R)-1,2-bis(trifluorosulfonamido)cyclohexane (8 mol%) provides chiral allylic alcohols in good yields (60-90%) and excellent enantioselectivity (usually in the range of 85-95% ee). The synthetic utility of these allylic alcohols as chiral building blacks is demonstrated. The gamma-stannylated allylic alcohols were submitted to a Stille coupling leading to polyfunctional allylic alcohols and gamma-alkoxy enones. A treatment with CuCN in N-methylpyrrolidone at 130 degrees C provided chiral unsaturated gamma-hydroxy nitriles. Finally, the desilylation of the gamma-silylated alcohols gave chiral allylic alcohols having a terminal double bond. The catalytic asymmetric addition was found to show an important inverse temperature dependance. A mechanism for this addition is proposed.
Simple Preparation of the Optically Active γ-Hydroxy Vinylstannanes Using Lipase-Catalyzed Hydrolysis
作者:Toshiyuki Itoh、Tadataka Ohta
DOI:10.1246/cl.1991.217
日期:1991.2
An efficient optical resolution of γ-hydroxy vinylstannanes was achieved by the lipase-catalyzed enantioselective hydrolysis of the corresponding racemic acetates using lipase PS(Pseudomonas sp.).
The addition of functionalized dialkylzincs to readily available beta-stannylated or beta-silylated unsaturated aldehydes in the presence of a catalytic amount of (1R,2R)-1,2-bis(trifluorosulfonamido)cyclohexane (8 mol%) provides chiral allylic alcohols in good yields (60-90%) and excellent enantioselectivity (usually in the range of 85-95% ee). The synthetic utility of these allylic alcohols as chiral building blacks is demonstrated. The gamma-stannylated allylic alcohols were submitted to a Stille coupling leading to polyfunctional allylic alcohols and gamma-alkoxy enones. A treatment with CuCN in N-methylpyrrolidone at 130 degrees C provided chiral unsaturated gamma-hydroxy nitriles. Finally, the desilylation of the gamma-silylated alcohols gave chiral allylic alcohols having a terminal double bond. The catalytic asymmetric addition was found to show an important inverse temperature dependance. A mechanism for this addition is proposed.