The chemistry of a ketene-sulfur dioxide adduct

We have demonstrated the formation of a reactive species from ketene and sulfur dioxide and have investigated some of its reactions. The 3 + 2 ← 5 cycloaddition reactions of this intermediate with benzylideneaniline and its derivatives gave the corresponding 2,3-diphenylthiazolidin-4-one 1,1-dioxides. The reduction of 2,3-diphenylthiazolidin-4-one 1,1-dioxide with lithium aluminum hydride yielded the corresponding thiazolidine. Aniline and its derivatives reacted with the ketene-sulfur dioxide adduct to give thioaceto-1,3-dianilide 3-oxide. o-Phenylenediamine gave 2,1,5]benzothiadiazepin-4-one 2-oxide, a derivative of a new ring system, 2,1,5]benzothiadiazepine. o-Aminophenol yielded 1,2,5]benzothiazepin-4-one 2-oxide.