Asymmetric Intramolecular Michael Addition of α-Sulfinyl Vinylic Carbanion to Enoates

The first example of an asymmetric intramolecular Michael addition reaction with use of α-lithiated vinylic sulfoxide as a Michael donor is reported. Michael addition of the α-lithiated vinylic sulfoxide to (Z)-enoates proceeds with high diastereoselectivity to give the adducts with (R)-configuration at the β-position of the ester in the five-membered-ring formation. The selectivity was reversed in the six-membered-ring formation. The resulting ester enolates were reacted with alkyl halides or benzaldehyde with high diastereoselectivity.