Rhodium-Catalyzed Regio- and Enantioselective Direct Allylation of Methyl Ketones

We report a highly branch-selective and enantioselective allylic alkylation of simple ketones with racemic aliphatic allylic carbonates under mild conditions. By using a Rh-bisoxazolinephosphine system and catalytic amounts of a base in THF, a series of chiral beta-branched gamma,delta-unsaturated ketones were obtained with excellent regio- and enantioselectivities. An outer-sphere nucleophilic substitution C-C bond-formation process is proposed on the basis of mechanistic studies.