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.