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.
Trialkylsilyl chlorides, particularly in combination with hexamethylphosphoramide or 4-dimethylaminopyridine, dramatically accelerates the conjugate addition of catalytic and stoichiometric organocopperreagents onto enones, enals, and enoates, in which very high degrees of stereo- and chemoselectivities were observed.