Simultaneous formation of 3-(benzimidazol-2-yl)quinoxalin-2(1H)-ones and 2-(benzimidazol-2-yl)quinoxalines from quinoxalin-2(1H)-one-3-carbaldoximes when exposed to 1,2-benzenediamines

Abstract Interaction of quinoxalin-2(1H)-one-3-carbaldoximes with 1,2-benzenediamine derivatives in AcOH or n-BuOH at reflux in the presence of sulfuric acid as catalyst was found to give 3-(benzimidazol-2-yl)quinoxalin-2(1H)-ones and 2-(benzimidazol-2-yl)quinoxalines in relatively good yields, which formed as a result of the Weidenhagen reaction and Mamedov rearrangement, respectively. The reaction in AcOH afforded 2-(benzimidazol-2-yl)quinoxalines in preference to the 3-(benzimidazol-2-yl)quinoxalin-2(1H)-ones, while the reverse result was obtained in n-BuOH. The synthetic utility of this strategy was illustrated by the concise, one-pot synthesis of 3-(3H-imidazo[4,5-b]pyridin-2-yl)quinoxalin-2(1H)-ones.