Selective Access to 3-Cyano-1H-indoles, 9H-Pyrimido[4,5-b]indoles, or 9H-Pyrido[2,3-b]indoles through Copper-Catalyzed One-Pot Multicomponent Cascade Reactions

Novel and selective synthetic approaches toward indole derivatives via copper-catalyzed one-pot multicomponent cascade reactions of 1-bromo-2-(2,2-dibromovinyl)benzenes with aldehydes and aqueous ammonia are presented. Intriguingly, the concentration of ammonia, the molar ratio of reagents, and the structural features of the aldehyde substrate serve as key factors in controlling the selective formation of 3-cyano-1H-indoles, 9H-pyrimido[4,5-b]indoles, or 9H-pyrido[2,3-b]indoles. Compared with litetature procedures, the synthetic approaches repotted herein have advantages such as readily available starting materials, mild reaction conditions, and divergent reaction patterns toward different products with easily tunable selectivity.