Stereoselective synthesis of (Z)-α,β-unsaturated ketones via hydromagnesiation of alkynylsilanes

Hydromagnesiation of alkynylsilanes 1 gives (Z)-alpha-silylvinyl Grignard reagents 2, which are treated with alkyl iodides in the presence of Cut to give (Z)-1,2-disubstituted vinylsilanes 3 in high yields. Intermediates 3 can undergo the Friedel-Crafts acylation reactions with acyl chlorides to afford (Z)-alpha,beta-unsaturated ketones in good yields with high stereoselectivity.