Highly stereoselective intramolecular Michael addition using alpha-sulfinyl vinyllithium as an unprecedented Michael donor

[GRAPHICS] The first example of an asymmetric intramolecular Michael addition reaction using cr lithiated vinylic sulfoxide as a Michael donor is reported. Micha el addition of the alpha -lithiated vinylic sulfoxide to (Z)-enoates procee ds with high diastereoselectivity to give the adducts having a stereogenic center with (R)-configuration at the beta -position of the ester in the cyc lopentene ring formation. The selectivity was reversed in the six-membered ring formation. On the other hand, the corresponding (E)-enoates provided M ichael adducts with poor diastereoselectivity.