A variety of tetrahydro-5H-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.