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The preparation of some 6‐ and/or 7‐substituted derivatives of 1,2,3‐benzothiadiazole is described. The reactivity of some compounds was investigated in view of the possibility that 1,2,3‐benzothiadiazoles may behave as masked diazo compounds. 7‐Diazo or diazonium compounds were prepared but no interaction with the thiadiazole part could be observed.

The transformations of 7‐methyl‐7H‐ and 8‐methyl‐8H‐pyrazolo[4, 3‐d]tetrazolo[1, 5‐b]pyridazines 1, 2, 9 and 10 into 8‐methyl‐8H‐ and 9‐methyl‐9H‐pyrazolo[3, 4‐H]‐s‐triazolo[4, 3‐b]pyridazines 7 and 8, and 1‐methyl‐1H‐and 2‐methyl‐2H‐imidazo[1, 2‐b]pyrazolo[3, 4‐d]pyridazines 13 and 14 are described.

The synthesis of new tetracyclic systems and new stable tautomers of known systems 11H‐ 13 and 10H‐imidazo[1, 2‐b]pyrazolo[4, 3‐d]‐s‐triazolo[3, 4‐f]pyridazine 16, 9H‐pyrazolo[3, 4‐d]bis‐s‐triazolo[4, 3‐6:5′,1‐f]‐pyridazine 15, 10H‐pyrazolo[3, 4‐d]bis‐s‐triazolo[4, 3‐b:3′,4′‐f]pyridazine 17, and 10H‐pyrazolo[4, 3‐d)bis‐s‐triazolo[4, 3‐6:5′,1′‐f]pvridazine 18 is described.