Research on heterocyclic compounds. XXXIII: Synthesis and analgesic activity of imidazo[1,2-b]pyridazine-2-acetic acid derivatives

A series of imidazo[1,2-b]pyridazine-2-acetic esters, acids and amides was synthesized and tested for antiinflammatory, analgesic and ulcerogenic activities. The ethyl esters were prepared by cyclocondensation of some 3-aminopyridazines with ethyl 4-chloroacetoacetate, followed by hydrolysis or ammonolysis in order to obtain the corresponding acids and amides. The capacity of inhibiting the carrageenan-induced edema in the rat paw and the writhes induced by acetic acid in mice were evaluated, as well as the ulcerogenic action in rats. The acidic derivatives showed significant analgesic activity which is comparable to that found in other series of imidazo[1,2-b]pyridazine analogs previously examined