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.