Studies with 2-Arylhydrazono-3-oxopropanaIs: A Novel Route to 4-Aroyl-2-aryl-1,2,3-triazoIes, 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 11 when treated with pyridine, whereas treatment with an acidic reagent resulted in the formation of 3-aroyl-2-phenyl-l,2,3-triazoles 12.