NHC-Cu-catalyzed protoboration of monosubstituted allenes. Ligand-controlled site selectivity, application to synthesis and mechanism.

Two types of NHC-Cu complexes catalyze protoborations of terminal allenes to afford valuable 1,1- or trisubstituted vinylboron species with high site selectivity and stereoselectivity. The scope of the method, application to natural product synthesis, and mechanistic basis for the observed selectivity trends are presented.