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

A variety of tetrahydro-5 H -indolo[2,3- b ]quinolines were prepared in 40-97% yields through a copper(II)-catalyzed cascade reaction of aza- o -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- b ]quinolines.