Ligand-catalyzed asymmetric alkynylboration of enones: a new paradigm for asymmetric synthesis using organoboranes.

Asymmetric conjugate alkynylation of enones may be effected using a B-1-alkynyldiisopropylboronate and catalytic amounts of binaphthol ligands. The high enantioselectivities observed are comparable to those obtained using stoichiometric amounts of binaphthol-modified boronate reagents, suggesting that this is a ligand-accelerated process. This is the first demonstration that catalytic amounts of chiral diols can be used with boronates to effect high levels of stereochemical control.