1,3-dipolar cycloadditions .98. The chemistry of thiocarbonyl S-sulfides

3,3,5,5-Tetraaryl-1,2,4-trithiolanes (1) equilibrate in solution with diaryl thioketones 2 and their S-sulfides 7 (thiosulfines). Activated acetylenes (DMAD, dicyanoacetylene, cyclooctyne) as dipolarophiles capture 7 furnishing 1,2-dithioles. A sulfur transfer from 2,2-diphenylthurane to thiones gives rise to thione S-sulfides 7 which quickly form 1,2,4-trithiolanes with a second molecule of thione. According to kinetic measurements, the desulfurizations of diphenylthurane by thiones are slower than those by P(III) compounds and follow the second order. 1,2,4-Trithiolanes and thiones undergo metathesis reactions via cycloreversion-cycloaddition. Thione S-sulfides are not isolable, bur decompose to thiones and elementary sulfur by fast sulfur transfer reactions. The MS of the 1,2-dithiolanes and 1,2,4-trithiolanes reveal the importance of distonic radical ions. Copyright (C) 1996 Elsevier-Science Ltd