Trans-Selective Radical Silylzincation of Ynamides†

The silylzincation of terminal ynamides is achieved through a radical-chain process involving (Me3Si)3SiH and R2Zn. A potentially competing polar mechanism is excluded on the basis of diagnostic control experiments. The unique feature of this addition across the CC bond is its trans selectivity. One-pot electrophilic substitution of the C sp 2Zn bond by CuI-mediated CC bond formation and subsequent manipulation of the C sp 2Si bond provides a modular access to Z-α,β-disubstituted enamides.