Palladium-Catalyzed Asymmetric Quaternary Stereocenter Formation

An efficient palladium catalyst is presented for the formation of benzylic quaternary stereocenters by conjugate addition of arylboronic acids to a variety of beta,beta-disubstituted carbocyclic, heterocyclic, and acyclic enones. The catalyst is readily prepared from PdCl2, PhBOX, and AgSbF6, and provides products in up to 99?% enantiomeric excess, with good yields. Based on this strategy, (-)-a-cuparenone has been prepared in only two steps.