SEQUENTIAL KETYL-OLEFIN COUPLING BETA-ELIMINATION REACTIONS MEDIATED BY SAMARIUM(II) IODIDE

Samarium(II) iodide (SmI2) has been employed in an intramolecular sequ ential ketyl-olefin coupling/beta-elimination reaction. The overall pr ocess results in the net addition of an alkenyl species to a ketone ca rbonyl. This novel protocol for the intramolecular delivery of an alke nyl moiety avoids the basic reaction conditions typical of nucleophili c additions that are mediated by alkenylmagnesium halides and alkenyll ithium reagents. A high degree of stereocontrol is imparted in the SmI 2-mediated process as a result of the excellent facial selectivity con veyed in the initial ketyl-olefin coupling reaction. The relative asym metric induction engendered in these addition reactions is complementa ry to more traditional nucleophilic addition reactions in that the alk enyl group is directed to the carbonyl center by an attached tether.