1,3-Oxathiolan-Synthese: Spirocyclische 1,3-Oxathiolane aus der Lewis-Säure-katalysierten Umsetzung von cyclischen Trithiocarbonaten und Oxiranen

1,3‐Oxathiolanc Synthesis: Spirocyclic 1,3‐Oxathiolanes from the Lewis‐Acid‐Catalyzed Reaction of Cyclic Trithiocarbonates and Oxiranes 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‐tetrathia‐spiro[4.4]nonane (7) is isolated as a minor product. The molecular structures of 5a, 6e, and 7 are established by X‐ray crystallography.