Pyridazine Derivatives, IX. Synthesis of 2H-Pyridazin-3-ones with Aroylpiperazinyl Groups

Several 2H-pyridazin-3-ones with phenylor 2-furoylpiperazinyl group, have been prepared.6-~heny?-5-1~~-aroyl-fl~-pipeeazinyl]-2~pyridazin-3-ones were obtained by nucleophilic substitution of the chlorine atom of B-phenyl-5-chloro-2B-pyridazin-3-one or alternatively, by hroylhtion of N1-piperazinyl-28-pyridazin-3-one.Also, 6-phen~l-5-(3~-aroyl-~'-piperazinylmethy1)-2B-pyridazin-3-ones were prepared by displacement of the bromine in 6-phenyl-5-bramomethy1-2H-pyridhzin-3-one.It is known that a series of 2H-pyridazin-3-ones of general formula I have antihypertensive properties112 experiments with a relatively large number of structural variations have shown that the substitution at position 5 (e.8.5-CH3) is favourable to these pr~perties.~It has also been noted that there is an N-aro?l~i?erazine moiety in several drugs acting an the cardiovascular system including the ol-adrenerbic blocker prazosin (II), and its benzothiadiazine analogue3 (III), losulazine4 (IV), and vesnarinone5 (V).