Triazines and related products. Part XII. Reactions of 3,4-dihydro-4-imino-1,2,3-benzotriazines and 1,2,3-benzotriazin-4(3H)-ones in secondary amines

3-Substituted 3,4-dihydro-4-imino-1,2,3-benzotriazines (1a-g) undergo ring opening in piperidine, morpholine, and pyrrolidine to afford the o-cyanophenyltriazenes (2a-g), respectively. Attack by the bases at the exocyclic imino-substituent is implicated in these isomerisations since the 3-benzyltriazine (1h) and the 3-substituted 4-arylimino-3,4-dihydro-1,2,3-benzotriazines (4a-e) are all unreactive. Similarly, reaction of the bases at the exocyclic imino-group of the N-hydroxy-tautomer of 4-aminobenzotriazine 3-oxide (6) leads to o-azidobenzonitrile (8). The fused 1,2,3-benzotriazines (11) and (13) react with secondary amines to afford 3,3-dialkyl- or polymethylenetriazenes, but the reactivity of 3-substituted 1,2,3-benzotriazin-4(3H)-ones (19) towards piperidine and its analogues is dependent on the nature of the 3-substituent.