Reduction-alkylation with organocopper(I) reagents-alkyl halides : Highly regioselective .ALPHA.-alkylation of .GAMMA.-acetoxy-.ALPHA.,.BETA.-enoates with lithium dibutylcuprate-alkyl halides and difference in the reactivity of electron-deficient olefins with organocopper(I)-Lewis acid reagents.

Abstract

Reaction of γ-acetoxy-α, β-enoates with lithium dialkylcuprate followed by alkyl halides results in the predominant or exclusive formation of α-alkyl-β, γ-enoates in high yields under mild conditions, and a synthetic application to (±)-α-vetispirene is presented. Treatment of diethyl fumarate and triethoxycarbonylethylene with Bu2CuLi·AlCl3 led to 1, 4-addition to give conjugate adducts in high yields. In sharp contrast, diethyl maleate and tetraethoxycarbonylethylene predominantly gave the respective reduction products. Evidence for a presumed dianionic intermediate, based on trapping with some electrophiles, is also presented.