A method for the site-selective and diastereoselective conjugate addition of boron-stabilized allylic nucleophiles to alpha,beta-unsaturated ketones is disclosed. Transformations involve easily prepared gamma,gamma-disubstituted allyldiboron reagents and proceed in the presence of a fluoride activator at 80 degrees C. Reactions proceed with a wide variety of enones and allyldiboron reagents efficiently to deliver ketone products that contain otherwise difficult-to-access vicinal beta-tertiary and gamma-quaternary carbon stereogenic centers and an alkenylboron moiety. The utility of the method is highlighted by several transformations, including cross-coupling and carbocyclizations.