α,β-Unsaturated thiocarbonyl S-sulfides (thiosulfines). Their generation, intramolecular trapping by a non-activated CC dipolarophile via[5 + 2] cycloaddition and trans-sulfurization ability

Abstract

α,β-Unsaturated thiocarbonyl S-sulfides (thiosulfines)10 were generated by sulfurization of the thioketones 5 and were intramolecularly trapped as 1,5-dipoles giving 8, whereas, in the presence of Et₃N, they were transformed by trans-sulfurization via 1,5 cyclization into the thioketones 13 capable of undergoing the intramolecular hetero-Diels–Alder reaction to give cycloadducts 9.