A New Approach to the Synthesis of 1,2- and 1,4-Dihydropyrido[3,2-b]indole Derivatives

Intramolecular cyclization of α-cyano-β-(3-p-nitrophenylaminoindol-2-yl)acrylonitrile yields 1-p-nitrophenyl-2-imino-3-cyano-1,2-dihydropyrido[3,2-b]indole 7, methylation of which by methyl iodide in acetone in the presence of potassium carbonate is accompanied by the addition of acetonyl anion and formation of 1-p-nitrophenyl-2-dimethylamino-3-cyano-4-acetonyl-1,4-dihydropyrido[3,2-b]indole 9.