Unexpected Reduction of Ethyl 3-Phenylquinoxaline-2- carboxylate 1,4-Di-N-oxide Derivatives by Amines

Abstract

The unexpected tendency of amines and functionalized hydrazines to reduceethyl 3-phenylquinoxaline-2-carboxylate 1,4-di-N-oxide (1) to afford a quinoxaline 1c andmono-oxide quinoxalines 1a and 1b is described. The experimental conditions werestandardized to the use of two equivalents of amine in ethanol under reflux for two hours,with the aim of studying the distinct reductive profiles of the amines and thechemoselectivity of the process. With the exception of hydrazine hydrate, which reducedcompound 1 to a 3-phenyl-2-quinoxalinecarbohydrazide derivative, the amines only actedas reducing agents.

Keywords

• Quinoxaline N-oxides
• reduction
• carboxylate
• amines.