(R)-8, Z= H (R)-8d, Z= D envisioned and are outlined in Scheme 11. Mechanism A would involve the direct exchange in (R j-13 via a six-centered Smiles rearrangementls to give (S)- 13. Mechanism B would involve two five-centered Smiles rearrangements, l8 the first yielding the achiral intermediate 14 and the second producing racemic 13 from 14. Small amounts (510%) of 14 were detected in all samples of racemic 13 by the characteristic ...