Photochemical reactions of N-acylbenzoxazole-2-thiones

Abstract

The photochemical reactions of N-acylbenzoxazole-2-thiones 1 are examined. Irradiation of N-acylbenzoxazole-2-thiones 1 in the presence of a variety of alkenes 2 yields 2-substituted benzoxazoles 3–20 and/or the unexpected products, iminothietanes 21–29 by intramolecular trapping of the acyl group by thiolate anion of the zwitterionic intermediate I and by the phenolate anion of the zwitterionic intermediate II, respectively, derived from the spirocyclic aminothietanes AT which are formed by regioselective [2+2] cycloaddition of the carbon–sulfur double bond of 1 to the alkene double bond.