Copper-catalyzed conjugate addition of the Grignard reagents in the presence of Me3SiCl and HMPA proceeds in much higher yield than the reaction of conventional organocopper reagents and shows very good regio-, stereo-, and chemoselectivities.
Chlorotrimethylsilane, particularly if combined with hexamethylphosphoric triamide or 4-dimethylaminopyridine, strongly promote the conjugate addition of stoichiometric organocopperreagents.