Two different structures for copper and lithium derivatives of vinylic enolates. The effect of structure on the direction of electrophilic attack

Abstract

Copper derivatives of enolates derived from αβ-unsaturated esters, acids, or ketones have the copper linked covalently to an sp²-hybridised carbon atom α to the carbonyl group. Their protonolysis or iodination proceeds with retention of configuration. Lithium derivatives of these compounds have the α-carbon sp-hybridised and the steric course of electrophilic attack does not depend on the configuration of the starting material, but on the ease of approach of the electrophile in the plane of the C(1)–C(2) double bond and the groups attached to the β-carbon atom.