α-and γ-Substitution Reactions of Cyclic γ-Acetoxy-α,β-Unsaturated Esters with a Novel Reagent BuCu-AlCl₃

Abstract

Organocopper (I) reagents are useful for carbon-carbon bond formations and it has been amply demonstrated that α,β-unsaturated acids or esters and allylic acetates react with a variety of reagents to give conjugate adducts^1,2) and substitution products³⁾, respectively. However, little is known on the carbon-carbon bond formation of γ-acetoxy-α,β-unsaturated esters with organocopper (I) reagent.⁴⁾ As part of a synthetic study directed towards toxic alkaloid with nerve-muscle activity, we required a butylated product starting from a cyclic γ-acetoxy-α,β-unsaturated ester. The unfortunate lack of reports on the reaction of cyclic γ-acetoxy-α,β-unsaturated esters with organocopper (I) reagent prompted us to describe our results on the reaction of cyclic γ-acetoxy-α,β-unsaturated esters with Bu₂CuLi, BuCu, and a novel reagent BuCu-(AlCl₃)_n.∗¹