Synthesis and antihypertensive activity of new 6-heteroaryl-3-hydrazinopyridazine derivatives

Abstract
The synthesis and pharmacological activity of new 6-heteroaryl-3-hydrazinopyridazines with antihypertensive action are described. The introduction of pyrrole, pyrazole, imidazole, triazole, tetrazole, thiophene, indole and carbazole heterocyclic rings into the 6 position of the pyridazine nucleus was carried out by 3 different methods of synthesis. The hypotensive action was examined on normotensive and spontaneously hypertensive rats by comparison with dihydralazine (I). 6-Imidazol-1-yl derivatives proved to be particularly active. Of these derivatives, 3-hydrazino-6-(2-methylimidazol-1-yl)pyridazine (7c) achieves 4.9 times the activity of dihydralazine when administered orally to spontaneously hypertensive rats. The LD50 values of 7c and dihydralazine are very similar.

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