Reactions of 2-(benzimidazol-2-yl)acetonitrile and its N-ethoxycarbonyl derivative with some azol-3-diazonium salts

Abstract

Coupling of 2-(1-ethoxycarbonyl-benzimidazol-2-yl)acetonitrile (II) with 5-methylpyrazol-3-diazonium (IIIa) or indazol-3-diazonium salt (IIIb) does not give the corresponding derivatives VIIa, VIIb of pyrazolo[3,2-c]-1,2,4-triazine but, instead, gives the corresponding 2-(3-azolyl)-1-oxo-1,2-dihydro-1,2,4-triazino-[4,5-a]benzimidazole-4-carbonitriles VIIIa, VIIIb. Coupling of 2-(benzimidazol-2-yl)acetonitrile (I) with the diazonium salt IIIa gives 7-amino-6-(benzimidazol-2-yl)-2-methylpyrazolo[3,2-c]-1,2,4-triazine (VIa) which, on reaction with ethyl chloroformate, undergoes cyclization to 2-methyl-12,13-dihydropyrazolo[3",2":3',4']-1,2,4-triazino[5',6':6,5]-pyrimido[3,4-a]benzimidazol-12-one (IXa). The compound VIa and 1-amino-2-(benzimidazol-2-yl)-1,2,4-triazono[4,3-b]indazole (VIb) are also formed by recyclization of the compounds VIIIa and VIIIb, respectively, in boiling aqueous pyridine.