1,2,3-Benzotriazin-4-ones and related systems. Part 6. Thermal and photolytic decomposition of 3-arylideneamino-, 3-imidoyl-, and 3-heteroaryl-1,2,3-benzotriazin-4-ones

Abstract

Thermal decomposition of 3-arylideneamino- and 3-imidoyl-1,2,3-benzotriazin-4-ones in solution gives 2-arylquinazolin-4-ones and 1,2-diaryl-1,4-dihydroquinazolin-4-ones, respectively. In the latter decompositions phenanthridones are also formed in minor but substantial (20%) yield. Possible mechanisms to account for these products are discussed. Photolysis of the 3-arylideneamino-derivatives in methanol provides a useful synthesis of aldehyde o-(methoxycarbonyl)phenylhydrazones. 3-(α-Pyridyl)- and 3-thiazol-2-yl-1,2,3-benzotriazin-4-one undergo thermal decomposition to pyrido[2,1-b]quinazolin-11-one and thiazolo[2,3-b]quinazolin-5-one, respectively.