Studies with 2-arylhydrazono-3-oxopropanals: A novel route to 4-aroyl-2-aryl-1,2,3-triazoles, 3-substituted 4-arylazopyrazoles, 2-substituted glyoxalonitrile and 3-oxoalkanonitriles

2-Arylhydrazono-3-oxopropanals 1 react with hydroxylamine hydrochloride to yield the corresponding oximes 3 that are cyclized into isoxazoles 9 on reflux in acetic anhydride and are converted into 2-arylhydrazono-3-oxonitriles (4) on treatment with pyridine. The reaction of 1 with hydrazines afforded dihydrazones 10 which were converted to arylazopyrazoles II when treated with pyridine, whereas treatment with an acidic reagent resulted in the formation of 3-aroyl-2-phenyl-1,2,3-triazoles 12.