Abstract The reaction of different substituted isatins with ortho-phenylenediamine in acetic acid has been investigated. While electron-donor substituents on isatin shift the reaction toward classical 6H-indolo [2, 3-b] quinoxaline ring closure, electron-withdrawing groups enhance the formation of 3-(2′-amino-5′-substituted)-quinoxaline-2 (1H)-ones. The structures of all synthesized compounds were assigned by using infrared, mass, 1H NMR, ...