Copper(I)-Catalyzed Formal Carboboration of Alkynes: Synthesis of Tri- and Tetrasubstituted Vinylboronates

The first copper-catalyzed formal carboboration of alkynes, in which a C–B bond and a C–C bond are created in a single catalytic cycle, is presented. The reaction proceeds with high regioselectivity and syn-stereoselectivity to form tri- and tetrasubstituted vinylboronic esters from commercially available bis(pinacolato)diboron. A subsequent cross-coupling reaction gives access to highly substituted alkenes.