Efficient Synthesis of Pyrido[2,3-b]indole Derivatives via Vanadium(III)-Catalyzed Cascade Cyclization of 2-(2-aminophenyl)acetonitrile and Enones

An efficient strategy for the synthesis of pyrido[2,3-b]indoles through VCl3-catalyzed cascade cyclization reactions of N,N-dimethyl enaminones or chalcones with 2-(2-aminophenyl)- acetonitrile under mild reaction conditions was developed. This method features many advantages, such as readily available starting materials, good substrate, good functional group tolerance, and good yields. A plausible reaction mechanism was provided. Moreover, the high yields of N-unprotected substrates made this reaction system extremely advantageous with currently known methods.