Sigmatropic Rearrangement of Cyclic α-Vinyl Sulfonium Imides : Formation of Thiazocine, Thiazonine, and Thiazecine Derivatives

Abstract

Thermolysis of the cyclic α-vinyl sulfonium p-toluenesulfonylimides (6a-c), prepared from 2-vinylthiolane (5a), 2-vinylthiane (5b), and 2-vinylthiepane (5c) by treatment with chloramine T, resulted in [2, 3]-sigmatropic rearrangement with ring-expansion to give the 1, 2-thiazocine (7a), 1, 2-thiazonine (7b), and 1, 2-thiazecine derivative (7c), respectively. Similarly, the 1, 2-benzothiazonine (17) and the 3, 4-benzothiazonine (18) were obtained from 2-vinylthiochroman (13) and 1-vinylisothiochroman (14) via the imides (15 and 16), respectively. The stereochemistry of the rearrangement is discussed.