SYNTHESIS OF PYRIDAZINE DERIVATIVES .23. TETRAZOLO-AZIDO TRANSFORMATIONS IN SOME FUSED AZOLOPYRIDAZINES

6‐Azidotetrazolo[1,5‐b]pyridazine (III) has been prepared by two different routes and is easily transformed into the 6‐amino derivative (IV). The attempted cyclization of 6‐hydrazinotetrazolo[1,5‐b] pyridazine (II) into the postulated tricycle has been shown to result in the formation of 6‐azido‐s‐triazolo [4,3‐b]pyridazine (VI), obtained also in a separate experiment from VII. The azido structure of VI has been confirmed from spectroscopic data and from its conversion into 6‐amino‐s‐triazolo [4,3‐b]pyridazine (VIII), obtained in another experiment from VII. Similarly, cyclization of II with cyanogen bromide resulted in the simultaneous formation of the s‐triazolo ring and ring opening of the fused tetrazolo ring, giving IX. For 6‐azido‐2‐phenylimidazo[1,2‐b]pyridazine (XII) the expected azide structure proved to be correct. Copyright © 1968 Journal of Heterocyclic Chemistry