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 C?C bond is its trans selectivity. One‐pot electrophilic substitution of the C? Zn bond by Cu^I‐mediated C? C bond formation and subsequent manipulation of the C? Si bond provides a modular access to Z‐α,β‐disubstituted enamides.