One Step Synthesis and Some Reactions of 7-Hydrazino-3,4-Diphenyl-2H -Pyrazolo [3,4-d] Pyridazine

Hydrazino-pyridazines continue to be an object of interest for improving medicinal drugs for blood pressure control such as hydralazine, which has been used for many years in the treatment of essential hypertension [1-3]. Recently, therapeutic interest in this kind of drug has increased considerably due to their cytotoxic activities, notably decreasing blood flow to tumors [4]. Lately, the syntheses of potential biologically active compounds containing pyrazolo [3,4-d] pyridazine systems have also been of great importance for medicinal and biological reasons [5,6]. Generally, pirazolo [3,4-d] pyridazines have shown good antimicrobial, antiinflammatory and analgesic activities [7]. From their structure–activity relationship, it may be expected that hydrazino-pyrazolo [3,4-d] pyridazines consisting of isosteric heterobicyclic systems, which are formed by the replacement of the benzene ring in hydralazine with a pyrazole nucleus, can exhibit interesting biological activities. On the other hand, furandiones of type 1 have been used successfully in the syntheses of various heterocycles for a long time [8]. As part of our research program on the reactions of cyclic oxalyl compounds with various hydrazines or hydrazones [9], we decided to investigate the reaction of 1 with anhydrous hydrazine.