Photochemical reactions of pyridine-4-thiones and acridine-9-thiones with alkenes

Abstract

The photochemical reactions of thiones with alkenes have been examined. Irradiation of pyridine-4-thione (1a) in the presence of electron-poor alkenes (2a,b) gave 4-substituted pyridines (3a,b)via ring cleavage and aromatization of a thietane intermediate. The photocycloaddition reaction of acridine-9-thiones (4) to alkenes (2) proceeds regiospecifically to form the spirothietanes (5). Irradiation of semicyclic enamino thiones (9) in the presence of an alkene affords the 3-substituted cyclohex-2-en-1 -one (10).