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.
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