Impact of Substituents on the Isatin Ring on the Reaction Between Isatins with Ortho-Phenylenediamine

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, 13C NMR, 13C-1H HSQC, and 13C-1H heteronuclear multiple bond correlation (HMBC) spectroscopic data.