Sequential Ketyl-Olefin Coupling/beta-Elimination Reactions Mediated by Samarium(II) Iodide.

Samarium(II) iodide (SmI(2)) has been employed in an intramolecular sequential ketyl-olefin coupling/beta-elimination reaction. The overall process results in the net addition of an alkenyl species to a ketone carbonyl. This novel protocol for the intramolecular delivery of an alkenyl moiety avoids the basic reaction conditions typical of nucleophilic additions that are mediated by alkenylmagnesium halides and alkenyllithium reagents. A high degree of stereocontrol is imparted in the SmI(2)-mediated process as a result of the excellent facial selectivity conveyed in the initial ketyl-olefin coupling reaction. The relative asymmetric induction engendered in these addition reactions is complementary to more traditional nucleophilic addition reactions in that the alkenyl group is directed to the carbonyl center by an attached tether.