The Kharasch reaction revisited: CuX 3Li 2-catalyzed conjugate addition reactions of Grignard reagents

Abstract

The conjugate addition of Grignard reagents RMgX to α,β-unsaturated ketones and esters is effectively catalyzed by soluble copper ate-complexes of the type CuX 3Li 2, e.g. CuI · 2LiCl. In the presence of Me 3SiCl the corresponding ketone enolsilanes are formed in high yield and selectivity. Diasteroselectivity in the case of chiral ketones is similar to that observed by using stoichiometric amounts of cuprates R 2CuLi. Thus CuX 3Li 2-catalyzed 1,4-additions of Grignard reagents may be an industrially viable process.