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Sequential Nucleophilic Acyl Substitution/Alkenyl Transfer Reactions Mediated by Samarium(II) Iodide
journal contribution
posted on 1998-05-30, 00:00 authored by Gary A. Molander, Christina R. HarrisSamarium(II) iodide (SmI2) has been employed in a
one-pot, three-step, nucleophilic acyl
substitution/ketyl−olefin coupling/β-elimination reaction sequence.
This novel protocol combines
two recently developed SmI2-mediated processes to permit
the net delivery of an alkenyl moiety to
a ketone carbonyl generated as an intermediate along the sequential
reaction pathway. A
remarkable measure of stereocontrol over three to five contiguous
stereocenters is established in
the process as a result of the excellent facial selectivity conveyed in
the ketyl−olefin coupling
reaction. Unique to the SmI2-mediated process, the
relative asymmetric induction engendered in
these addition reactions is complementary to more traditional
nucleophilic addition reactions in
that the alkenyl group is delivered to the carbonyl center by an
attached tether. Moreover, the
protocol avoids the basic reaction conditions characteristic of
alkenylmagnesium halides and
alkenyllithium reagents.