Chiral catalyst has been released already when the rearrangement occurs, but the ylide may retain the chirality which is induced in the previous step by the reaction of chiral metal carbene with sulfide. Asymmetric induction is also possible in this case because the [2,3]-sigmatropic rearrangement occurs through a concerted process. This requires that the racemization of the sulfur chiral center to be slower than the [2,3]-sigmatropic rearrangement process