Reduction-Alkylation with Organocopper(I) Reagents-Alkyl Halides : Highly Regioselective α-Alkylation of γ-Acetoxy-α, β-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.