Reduction of indolo [2, 3-b] quinoxalines with zinc in the presence of an anhydride gave N, N-diacyl trapped 6, 11-dihydroindolo [2, 3-b] quinoxalines in 43–92% yields. When the reduction with zinc was performed in TFA/TFAA, an unexpected ring opened product was isolated in 49% yield. The structure of this product could be identified as 1, 2-dihydro-1- trifluoroacetyl-3-[(2-trifluoroacetylamino) phenyl] quinoxaline.
