Photochemical behaviour of some 1,2,4-oxadiazole derivatives

Abstract

The photochemical behaviour of some 1,2,4-oxadiazole derivatives in methanol has been studied at 254 nm. On irradiation, 3-amino-(or 3-methylamino-) 5-aryl-1,2,4-oxadiazoles underwent a ring photoisomerization to 1,3,4-oxadiazoles, probably through a ‘ring contraction–ring expansion’ route. Irradiation of 3-dimethylamino-5-phenyl-and 3,5-diphenyl-1,2,4-oxadiazole gave mainly open chain products derived from reaction of a photolytic intermediate with the nucleophilic solvent. Some mechanistic considerations are reported.