Cobalt-catalyzed mono-coupling of R3SiCH2MgCl with 1,2-dihalogenoethylene: a general route to γ-substituted (E)-allylsilanes

The reaction of trimethylsilylmethylmagnesium chloride (TMSCH2MgCl) with 1,2-dihalogenoethylene in the presence of 1 mol % of Co(II) or Co(III) acetylacetonate in THF or THF–NMP proceeded exclusively in a mono-coupling pathway to provide 3-trimethylsilyl-1-halogeno-1-propene with >99% of E geometry in high yield, which was converted to a variety of γ-substituted allylsilanes by Ni- or Pd-catalyzed coupling with organometallic compounds.