A powerful strategy for the regioselective bidirectional synthesis of unsymmetrically substituted ketones is described, relying on the fact that the exchange of a xanthate is much faster than the radical addition to an unactivated alkene. The use of an alkene as the formal "alkylating" agent associated with the tolerance for numerous functional groups and the mildness of the experimental conditions removes many of the problems associated with the classical ionic and transition-metal-based approaches.