Triazines and related products. Part III. Synthesis and rearrangement of 3,4-dihydro-4-imino-1,2,3-benzotriazines

A series of 3-substituted-3,4-dihydro-4-imino-1,2,3-benzotriazines (V) have been prepared by cyclization of the appropriate o-cyanophenyltriazenes (IV) in 70% aqueous ethanol or in ethanol containing 2% piperidine. Triazenes with powerful electron-withdrawing substituants cyclize directly to substituted 4-anilino-1,2,3-benzotriazines (VI). Rearrangement of 3-aryl-3,4-dihydro-4-imino-1,2,3-benzotriazines to the isomeric 4-anilino-1,2,3-benzotriazines has been effected in ethanol or in 2N-hydrochloric acid and is facilitated by electron-withdrawing substituents in the aryl nucleus. The contrasting stabilities of 3-benzyl- and 3-phenethyl-3,4-dihydro-4-imino-1,2,3-benzotriazine have been attributed to a steric affect.