Asymmetric Intramolecular
Pauson–Khand Reaction
Mediated by a Remote Sulfenyl or Sulfinyl Group
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Abstract
In this work, we report the use of the asymmetric intramolecular
Pauson–Khand reactions of 4-aryl-4-cyano-1,6-enynes for obtaining
enantiomerically enriched bicyclo[3.3.0]octenones, and the influence
of both the quaternary stereocenter and the sulfur functions located
at <i>ortho</i>-position of the aryl group, on their stereoselectivity
and reactivity. The sulfenyl derivatives bearing substituted or unsubstituted
triple bonds and mono- and disubstituted alkene moieties afford bicyclo[3.3.0]octenones
in high yields with complete diastereocontrol. These results are explained
by assuming the association of the lone electron pair at sulfur to
the Co–alkyne complexes