SEQUENTIAL NUCLEOPHILIC ACYL SUBSTITUTION ALKENYL TRANSFER-REACTIONS MEDIATED BY SAMARIUM(II) IODIDE

Samarium(II) iodide (SmI2) has been employed in a one-pot, three-step, nucleophilic acyl substitution/ketyl-olefin coupling/beta-elimination reaction sequence. This novel protocol combines two recently develope d SmI2-mediated processes to permit the net delivery of an alkenyl moi ety to a ketone carbonyl generated as an intermediate along the sequen tial reaction pathway. A remarkable measure of stereocontrol over thre e to five contiguous stereocenters is established in the process as a result of the excellent facial selectivity conveyed in the ketyl-olefi n coupling reaction. Unique to the SmI2-mediated process, the relative asymmetric induction engendered in these addition reactions is comple mentary to more traditional nucleophilic addition reactions in that th e alkenyl group is delivered to the carbonyl center by an attached tet her. Moreover, the protocol avoids the basic reaction conditions chara cteristic of alkenylmagnesium halides and alkenyllithium reagents.