Stereoselective S_N2' alkylation reaction sequence of the γ,δ-epoxy α,β-unsaturated ester system via γ,δ-chlorohydrin intermediates by the use of a R3Al-CuCN reagent

摘要

A novel stereoselective S_N2' alkylation reaction sequence of the γ,δ-epoxy α,β-unsaturated ester system has been developed which involves a regioselective substitution reaction with chloride ions at the γ-posi-tion and a subsequent S_N2' alkylation reaction of the resulting γ-chloro-δ-hydroxy derivatives with a R3Al-CuCN reagent. The new methodology was demonstrated to be applicable to a variety of substrates and to provide various δ-hydroxy-α-alkyl-β,γ-unsaturated esters including those bearing a quaternary asymmetric carbon atom at the α-position in a highly stereoselective manner and high yields.