Regioselective synthesis of highly functionalized alkenylboronates by Cu-catalyzed borylation of propargylic silylalkynes.

High regioselectivity was achieved in the Cu(i)-catalyzed borylation of internal propargylic alkynes with a silyl substituent to afford multifunctionalized alkenylboron compounds. While both the silyl and propargylic substituents are known to act as directing groups, a N-heterocyclic carbene (NHC)-Cu complex furnished β-vinylboronate products (relative to Si) with high selectivity.