Synthesis and analgesic activity of some 4,6-disubstituted-3(2H)-pyridazinone derivatives.

A series of 6-morpholino-4-aryl-3(2H)-pyridazinone alkanoic acids, their ester and amide derivatives were prepared and tested for their in vivo analgesic activity by using the p-benzoquinone-induced writhing test. The analgesic activity of the compounds 6-morpholino-4-aryl-3(2H)-pyridazinone (6a-b) were comparable but little lower than that of acetyl-salicylic acid (CAS 50-78-2) as an analgesic agent. The 6-morpholino-4-aryl-3(2H)-pyridazinones having a propanoic acid (10a-b), ester (7a) and amides (12a-b, 12d and 12g) as side chains at the position 2 of the pyridazinone ring showed higher activity than the reference compound without gastric ulceration forming potential. All other compounds generally showed higher activity but caused gastric ulceration in the animals.