Reaction of aminobenzoateesters with N,N′-dimethylformamide azine dihydrochloride: crucial influence of intramolecular hydrogen bonding for the formation of 1,2,4-triazoles

Abstract

The reaction of N,N′-dimethylformamide azine (DMFA) or its dihydrochloride derivative (DMFA·2HCl) with o-RO(O)CC₆H₄NH₂ (R = Me, Et) leads to co-crystallization products o-RO(O)CC₆H₄NH₂·DMFA (R = Me, Et), while the same reaction of DMFA·2HCl with m- and p-RO(O)CC₆H₄NH₂ (R = Me, Et) provides the corresponding 4-substituted 1,2,4-triazoles (1–4). Reaction of the same m- and p-substituted amines with DMFA has failed, while addition of a few drops of HCl or HNO₃ in this reaction mixture has allowed us to obtain the corresponding triazole derivatives. Thus, the direct transamination reaction with the formation of triazoles 1–4 is catalysed by acidic catalysts. Molecular structures of DMFA, o-EtO(O)CC₆H₄NH₂·DMFA and 3 were elucidated by X-ray diffraction.