Lewis Acid Mediated Reactions of Organocopper Reagents. Entrainment in the Conjugate Addition to α,β-Unsaturated Ketones, Esters, and Acids via the RCu*BF3 System

Article abstract of DOI:10.1021/jo00340a026

Lewis acid mediated reactions of organocopper reagents with various kinds of α,β-unsaturated carbonyl derivatives are described.RCu*BF3, as well as RCu-other Lewis acid systems, is useful for the conjugate addition to the α,β-unsaturated ketones and esters, whose double bonds are sterically crowded.Certain α,β-unsaturated carboxylic acids also undergo a 1,4-addition through this reagent.Methyl sorbate undergos a 1,4-addition via BuCu*BF3, while undergoing a 1,6-α,δ-addition via Bu2CuLi.BuCu*BF3 reacts more readily with an aldehyde than with a ketone; the degree of chemoselectivity is greater than that of Bu2CuLi, BuLi, or BuMgBr.The R2CuLi-BF3 system is useful for the double alkylation of α,β-unsaturated esters at the β-position and the carbonyl center.Stereochemical aspects of these new copper reagents are also reported.