The reported structures of reaction products of enaminones with malononitrile in ethanolic piperidine are revised. A novel route to 2,3-dihydropyridazine-4-carboxylic acids 4a-c via reactions of 2-cyano-5-(dimethylamino)-5-arylpenta-2,4-dienamides 8a-c with nitrous acid or with benzenediazonium chloride is reported. Compounds 8a-c are converted to 1,2-dihydropyridine-3-carboxylic acid and 1,2-dihydropyridine-3-carbonitrile derivatives upon reflux in EtOH/ HCl and in AcOH.

Efficient routes to 2-arylhydrazono-3-oxoalkanonitriles, 1,2,3-and 1,2,4-triazoles, and 3-aminoisoxazole utilising the oximes of the title hydrazones are reported. The behaviour of the oximes on pyrolysis in the gas phase and by flash vacuum is analysed. X-ray crystallography were used to confirm the structure of the triazole 10b and the 3-oxoalkanonitrile 12f.

3-Oxoalkanenitriles 1a-d were obtained in high yield by treating enaminones 6a-d with hydroxylamine hydrochloride and stirring the resulting oxime with diethyl oxalate. The formed 3oxoalkanenitriles 1a,b readily undergo self-condensation to yield 2aroylanilines 3a,b on heating in pyridine for eight hours or by irradiation in microwave for 1.5 minutes. In contrast, 1c-e were recovered unreacted under similar conditions. Pyrolysis of 3aminocrotononitrile 14 produced a mixture of the aminopyridine 16, 19, and aminobenzene 22. Heating 14 in aqueous media has resulted in formation of the pyridine 20, while heating the same compound in acetic acid has afforded pyridone 20 and acetyl pyridine 24.

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Several new enaminodienones prepared from substituted acetone and dimethylformamide dimethylacetal were used as precursors for synthesis of pyridines, pyranones and benzofurans.