A Combined Experimental and Theoretical Study of the Ammonium Bifluoride Catalyzed Regioselective Synthesis of Quinoxalines and Pyrido[2,3-b]pyrazines

Abstract

Ammonium bifluoride was efficiently used at a 0.5 mol% loading to catalyze the cyclocondensation of 1,2-arylenediamines with 1,2-dicarbonyl compounds at room temperature in methanol–water to give quinoxalines or pyrido[2,3-<i>b</i>]pyrazines in excellent yields. Importantly, 2,8-disubstituted quinoxalines and 3-substituted pyrido[2,3-<i>b</i>]pyrazines were regioselectively formed by the reaction of arylglyoxals with 3-methylbenzene-1,2-diamine or pyridine-2,3-diamine, respectively. An analysis of the density functional theory reactivity indices explained the catalytic role of ammonium bifluoride.