The acid-catalyzed transannular cyclization of 8–10-membered γ, δ-unsaturated cyclic sulfides yields cis fused bicyclic sulfonium salts independently of the geometry of the double bond. The rate varies linearly with the acidity function–(H0) I with a slope of 1. The rate variations span about six powers of ten range, the maximum rate difference being observed for the E/Z thiacyclooct-4-ene pair. The data are consistent with the classical interpretation ...
