β-Oxo Anilides in Heterocyclic Synthesis: Novel Synthesis of Substituted Pyridazinones, Pyridine, Pyrimidines and Pyrazolotriazines

Diazotization and coupling of acetoacetanilide derivative 1 with aromatic amines afforded the arylhydrazones 2a,b. Arylhydrazones 2a,b were treated with (DMF-DMA) to yield the pyridazine derivatives 3a,b in good yield. Pyridazinone was treated with hydrazine hydrate to yield 4a,b. Reaction of 2a with hydroxylamine hydrochloride afforded the oxime derivative 5. Similarly, the reaction of acetoacetanilide 1 with hydroxylamine hydrochloride gave 3-hydroxyimino-N-p-tolyl-butyramide 8 not the pyrazolone 9. The reaction of anilide 4 with aromatic aldehydes yielded 10a,b. Also, when anilide 4 was reacted with a mixture of aromatic aldehydes, urea or thiourea afforded the pyrimidines 11a,b. The reaction of anilide 1 with active methylene reagents was also investigated. So, 1 was reacted with malononitrile to give the pyridone derivative 12. Similarly, anilide 1 was reacted with cyanoacetamide under the same reaction conditions to yield 4-methyl-2-oxo-6-p-tolylamino-1,2-dihydro-pyridine-3-carbonitrile 13 in quantitative yield. The reaction of 1 with ylidenemalononitrile depends on structure of substituent. Thus, reaction of 1 with benzylidenemalononitrile or naphthylidenemalononitrile afforded 14a,b, while that with p-anisidine-malononitrile afforded 15. Coupling 1 with diazotized 16 - 18 afforded 19 - 21 respectively. Condensing 1 and aminopyrazoles 22a,b afforded the acyclic adduct 23a,b rather than the pyrazolopyrimidine 24a,b.