Remote Asymmetric Induction via a Chiral Acetylene Equivalent

Asymmetric
transformations have, to date, typically relied on proximal
steric biasing to favor the formation of one enantiomer over the other
during the enantiodetermining step. We report the use of an enantioenriched
oxabicycle that serves both as a chiral auxiliary and an acetylene
surrogate following two selective palladium-catalyzed carbopalladations
and a postcatalytic retro-Diels–Alder step. Differentiating
functional groups, that are remote from the reactive alkene, direct
the reaction with an ortho-iodostyrene and a terminating
reagent in a domino fashion, providing enantioenriched indenes. The
phosphine ligand has a dramatic influence on the overall process,
as alkyl- and arylphosphines lead to opposite major enantiomers of
the final indene product.