Abstract N, N′-Dialkylation of indolo [2, 3-b] quinoxaline could theoretically furnish three isomers, that is, salts dialkylated at the 5, 6-, the 6, 11-, and the 5, 11-positions. By using the 2, 3-dimethylated derivatives as models, the regioisomeric salts were selectively synthesized either by alkylation of the tetracycle or by cyclization of 1-methylisatin with N, 4, 5-trimethylbenzene-1, 2-diamine. The structure of the N, N′-dimethyl salts were ...