Regio‐ and Stereoselective Approach to 1,2‐Di‐ and 1,1,2‐Trisilylethenes by Cobalt‐Mediated Reaction of Silyl‐Substituted Dibromomethanes with Silylmethylmagnesium Reagents

Functional ethenes: Treatment of dibromo(silyl)methanes 2 a with silylmethyl Grignard reagents 1 and catalytic CoCl2 affords (E)-1,2-disilylethenes 3 a in excellent yields. Dibromodisilylmethanes 2 b undergo a similar transformation to furnish trisilylethenes 3 b with excellent stereo- and regioselectivity in the presence of a stoichiometric amount of a cobaltate reagent.