1,3-Oxathiolane Synthesis: Spirocyclic 1,3-Oxathiolanes from the Lewis-Acid-Catalyzed Reaction of Cyclic Trithiocarbonates and Oxiranes

Article abstract of DOI:10.1002/hlca.19910740714

The cyclic trithiocarbonates 1,3-dithiolane-2-thione (4) and 1,3-dithiole-2-thione (9) in 1,2-dichloroethane and MeCN, respectively, react with alkyl- and phenyl-substituted oxiranes 2 in the presence of Lewis acids to give 1-oxa-4,6,9-trithiaspiro<4.4>nonanes 5 and 6 (Scheme 2) and 1-oxa-4,6,9-trithiaspiro<4.4>non-7-enes 10 and 11 (Scheme 3), respectively.The reactions proceed regioselectively yielding 2-alkyl (5, 10) and 3-phenyl-derivatives (6, 11) as the main products.From the reaction of 4 and 2-phenyloxirane (2e) with TiCl4, 2-phenyl-1,4,6,9-tetrathiaspiro<4.4>nonane (7) is isolated as a minor product.The molecular structures of 5a, 6e, and 7 are established by X-ray crystallography.