Synthesis of 3-methyl-[1,2,4] -triazepino[6,5,4-jk] carbazol-4(3H)one

The title compound ( 14 ), a representative of a novel ring system, was prepared from 9H-carbazole-1-carboxylic acid 1-methylhydrazide ( 7 ) and triethyl orthoformate. Attempted cyclization of 7 with triethyl orthoacetate led only to 9H-carbazole-l-carboxylic acid 2-(l-ethoxyethylidene)-l-methylhydrazide ( 16 ). Treatment of 16 with trifluoroacetic acid gave 9H-carbazole- 1 -carboxylic acid ( 12 ). A postulated mechanism for this transformation was supported by studies with model compounds. A new synthesis of 1 -benzoyl-2-methylhydrazine ( 24 ), using 1-acetyl-1-methylhydrazine ( 22 ) as a synthon, is described.