Photochemical ring opening of 1-arylpyrimidin-2(1H)-ones

Abstract

The photochemical reactions of 1-arylpyrimidin-2(1H)-ones have been examined. Irradiation of the 1-arylpyrimidin-2(1H)-ones (3a–f) in benzene–methanol gave 1-alkoxycarbonylamino-3-aryliminoprop-1-enes (4), (6), and (7), which were hydrolysed to give the corresponding 3-alkoxycarbonylaminoprop-2-enal (5), in 45–55% yield. The formation of the N-arylimine products (4), (6), and (7) was presumed to arise from an unstable isocyanate intermediate (8) formed initially by Type I cleavage of the 1-arylpyrimidin-2(1H)-one (3).