Synthesis of some new derivatives of 4‐hydrazino‐5 H ‐pyridazino[4,5‐ b ]indole

This paper describes the synthesis of 1‐chloro‐4‐hydrazino‐5 H ‐pyridazino[4,5‐ b ]indole ( 4 ) and some of the triazoles ( 6–8 ), tetrazoles ( 10–11 ), triazolotetrazoles ( 9 ) and bis ‐tetrazoles ( 12 ) derived from it. All of these were previously unknown compounds. Treating 1,4‐dioxo‐1,2,3,4‐tetrahydro‐5 H ‐pyridazino[4,5‐ b ]indole ( 1 ) with phosphorus oxychloride gave 1,4‐dichloro‐5 H ‐pyridazino[4,5‐ b ]indole ( 2 ), which reacts regioselectively with hydrazine to give compound 4 . The reactions of 4 with formic and acetic acids gave 6‐chloro‐11 H ‐1,2,4‐triazolo[4,3‐ b ]pyridazino[4,5‐ b ]indoles ( 6a‐6b ), respectively. Reaction of compound 6a with hydrazine gave 6‐hydrazino‐11 H ‐1,2,4‐triazolo[4,3–6]‐pyridazino[4,5,‐ b ]indole ( 8 ). This with nitrous acid gave 6‐azido‐11 H ‐1,2,4‐triazolo[4,3‐ b ]pyridazino[4,5‐ b ]‐indole ( 9 ). Compound 4 reacted with nitrous acid to give 6‐chloro‐11 H ‐tetrazolo[4,5‐ b ]pyridazino[4,5‐ b ]‐indole ( 10 ), which gave 1,4‐diazydo‐5 H ‐pyridazino[4,5‐ b ]indole ( 12 ), through successive reactions with hydrazine and nitrous acid. All compounds were characterized by elemental analysis, ir and 1 H‐nmr spectra.