Synthesis of 4-aminopyrido[3,2-b]indole derivatives

3-Arylamino-2-formylindoles were converted into oximes and then acetylated to give the corresponding O-acetyl derivatives. Chloroacetylation of the latter was accompanied by elimination of acetic acid, yielding 3-(N-aryl-N-chloroacetyl)amino-2-cyanoindoles. When heated in pyridine, these nitriles underwent cyclization into novel δ-carboline derivatives: 4-amino-1-aryl-2-oxo-1,2-dihydropyrido[3,2-b]indol-3-yl)pyridinium chlorides. The structures of the compounds obtained were proved by IR and ¹H NMR spectroscopy and mass spectrometry. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1201—1207, July, 2006.