Triazines and related products. Part XIV. Decomposition of 1,2,3-benzotriazin-4(3H)-ones in the presence of reactive methylene systems

Abstract

In the presence of βγ-unsaturated esters, 1,2,3-benzotriazin-4(3H)-one (1) is thermally transformed into the quinazolino[3,2-c][1,2,3]benzotriazinone (13), which then undergoes cleavage of the N(2)–N(3) bond in the triazine ring to afford the quinazolinylphenylhydrazones (14). The initial step in the reaction probably involves a nucleophilic attack of one molecule of the triazinone (1) at the reactive 4-position of another molecule. 3-Alkyl- and 3-aralkyl-1,2,3-benzotriazin-4(3H)-ones are all stable in boiling ethyl cyanoacetate, but the 3-arylbenzotriazinones undergo thermal heterolysis of the N(2)–N(3) bond, followed by reaction with the ester, to yield phenylcarbamoylphenylhydrazones.