Studies with 2-(Arylhydrazono)aldehydes: Synthesis and Chemical Reactivity of Mesoxalaldehyde 2-Arylhydrazones and of Ethyl 2-Arylhydrazono-3-oxopropionates

The coupling reaction of 3-(dimethylamino)acrolein (2a) and ethyl 3-(dimethylamino)acrylate (2b) with arenediazonium chlorides afforded the 2-(arylhydrazono)aldehydes 1a - e. Compounds 1a, b reacted with hydroxylamine hydrochloride to yield the oximes 4a, b. The dioxime 5 was obtained from reaction of 1a with an excess of hydroxylamine hydrochloride. This dioxime afforded the 1,2,3-triazole carbonitrile 6 when treated with acetic anhydride, while α-hydrazono propionitrile 8 was obtained when 5 was treated with acetic acid. Compounds 1a - e could be utilized for the synthesis of a variety of pyrazoles and arylazolopyrimidines via reaction with hydrazines, haloketones and aminoazoles, respectively.