6-Hydrazinonicotinic acid hydrazide: A useful precursor for chemo- and regioselective synthesis of new heteroaryl-linked pyridinohydrazones

Abstract

In order to demonstrate the reactivity differentiation between the two dinucleophilic centers in the 6-hydrazinonicotinic acid hydrazide hydrate (1), a series of seven new 6-[(2-(arylidene)hydrazinyl]nicotinohydrazides (4) was chemoselectively accessed from the reaction of 1 with seven aryl or heteroaryl aldehydes by a simple procedure in ethanol as solvent. In a subsequent study, cyclization reactions of 4 with some 4-alkoxy-1, 1, 1-trifluoroalk-3-en-2-ones or triethylorthoacetate were proceeded easily also in ethanol, an eco-friendly solvent, to give regioselectively nine examples of pyrazolinyl- pyridinohydrazones and one 1, 3, 4-oxadiazole derivative, respectively, as stable and pure compounds in good yields. © ARKAT-USA, Inc.