Synthesis of 2-, 3-, and 4-Substituted Pyrido[2,3-b]indoles by C-N, C-O, and C-C(sp) Bond Formation

The synthesis of 2-, 3-, and 4-substituted alpha-carbolines is described starting from the corresponding chloropyrido[2,3-b]-indoles by Buchwald-Hartwig and Sonogashira cross-coupling reactions. Regioselective Sonogashira reactions on 2,4-dichloropyrido[2,3-b]indoles are also presented as an efficient route to unsymmetrically 2,4-disubstituted alpha-carbolines.