Unexpected stereoselective CuBr₂-catalyzed cascade reaction of 2-ethynylanilines with silylynamides: facile and atom-economical access to N-vinylsilylindoles

A stereoselective copper-catalyzed cascade reaction of 2-ethynylanilines with silylynamides has been developed. In this protocol, inexpensive CuBr₂ is utilized as the catalyst. This simple, ligand-free, and cost-effective catalytic system furnishes valuable N-vinylsilylindoles in good to excellent yields, with perfect stereoselectivity in open air. Its potential synthetic applicability is illustrated by a large-scale experiment and down-stream synthetic transformation of the products.