Novel chemical behaviour of a [2,3] sigmatropic rearrangement product of 2-phenyltetrahydrothiopyranium 1-methylide

Abstract

1,3,4,5,6,11a-Hexahydro-7E-2-benzothionine 5, which is a [2,3] sigmatropic rearrangement product of 2-phenyltetrahydrothiopyranium 1-methylide 8, has been synthesized by reaction of 1-methyl-2-phenyltetrahydrothiopyranium triflate 3 with sodium amide in liquid ammonia or by the fluoride ion-induced desilylation of trans-2-phenyl-1-[(trimethylsilyl)methyl]tetrahydrothiopyranium perchlorate trans-7. Compound 5 is stable at room temperature and reverts to ylide 8 by ring-opening.