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 TiCl 4 , 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.