The Reaction of Ethyl 2-oxo-2H-chromene-3-carboxylate with Hydrazine Hydrate

摘要

Although salicylaldehyde azine (>3) was reported in 1985 as the single product of the reaction of ethyl 2-oxo-2H-chromene-3-carboxylate (>1) with hydrazine hydrate, we identified another main reaction product, besides >3, which was identified as malono-hydrazide (>4). In the last two decades, however, some articles have claimed that this reaction afforded exclusively hydrazide >2 and they have reported the use of this hydrazide >2 as a precursor in the syntheses of several heterocyclic compounds and hydrazones >6. We reported herein a study of the formation of >2 and a facile route for the synthesis of the target compounds N'-arylidene-2-oxo-2H-chromene-3-carbohydrazides >6a–>f.