π-Facial Diastereoselectivity in Diels-Alder Reactions of 2,5-Dimethylthiophene Oxide.

Abstract A series of [4 + 2] cycloadditions with 2,5-dimethylthiophene oxide (2), generated in situ by peracid oxidation of 2,5-dimethylthiophene (1), are described. In all cases the syn adduct (with respect to the sulfoxide oxygen) is formed exclusively.