Conversion of some 2-arylmethylene-4-oxobutanhydrazides into pyridazinones, pyrrolones and pyrazolones

A novel series of 2-arylmethylene-4-[4-methoxy-3-methylphenyl]-4-oxobutanhydrazides (2a-c) was synthesized via the reaction of 3-arylidene-5-[4-methoxy-3-methylphenyl]furan-2(3H)-ones(1a-c) with hydrazine hydrate. The hydrazides (2a-c) were used as starting compounds for the synthesis of a variety of heterocyclic compounds: 3(2H)-pyridazinones (3a-c), N-amino-2(3H)-pyrrolones (7a-c) and 1H-pyrazol-3(2H)-ones (10a-c) via cyclization reactions. Depending on the reaction conditions, the acylation of the hydrazides (2a-c) with benzoyl chloride in toluene afforded the corresponding N`-benzoyl 4-oxobutanhydrazides (5a-b) or 1-benzoyl-1,2-dihydro-3(4H)-pyridazinones (6a-c). The condensation of the hydrazides (2a-c) with various aldehydes gave the corresponding N'-arylidene-4-oxobutanhydrazides (8a-h), which underwent ring closure into the corresponding N-arylidenamino-2(3H)-pyrrolones (9a-d) upon treatment with acetic anhydride.