Synthesis of Tetrahydro-5-indolo[2,3-]quinolines through Copper-Catalyzed Cascade Reactions of Aza--quinone Methides with Indoles.

A variety of tetrahydro-5-indolo[2,3-]quinolines were prepared in 40-97% yields through a copper(II)-catalyzed cascade reaction of aza--quinone methides generated in situ from 2-(chloromethyl)anilines and indoles. Experimental results showed that the reaction underwent double 1,4-additions and sequential intramolecular cyclization. The present method features broad substrate scope, good functional group tolerance, and easy gram scalable preparation of indolo[2,3-]quinolines.