AbstractCoupling of dimedone with the diazonium salt of 4‐aminoantipyrine afforded 2,3‐dimethyl‐4‐[2‐(5,5‐dimethyl‐ 2,6‐dioxocyclohex‐2‐ylidend)‐hydrazino]‐5‐oxo‐1‐phenylpyrazoline (3). Reaction of 3 with excess phenylhydrazine gave the mixed trishydrazone derivative 4. Treatment of 3 with hydroxylamine produced the bisoxime 5 which upon dehydrative cyclization with acetic anhydride gave the corrsponding tetrahydrobenzo[d][1,2,3]triazole derivative 7. A one‐pot synthesis of 7 was done by reacting 3 with hydroxylamine hydrochloride in pyridine, followed by heatment with acetic anhydride.