Asymmetric intramolecular michael addition of alpha-sulfinyl vinylic carbanion to enoates.

The first example of an asymmetric intramolecular Michael addition reaction with use of alpha-lithiated vinylic sulfoxide as a Michael donor is reported. Michael addition of the alpha-lithiated vinylic sulfoxide to (Z)-enoates proceeds with high diastereoselectivity to give the adducts with (R)-configuration at the beta-position of the ester in the five-membered-ring formation. The selectivity was reversed in the six-membered-ring formation.