Accessing [6,6,5,6] tetracyclic indeno-quinolines via a photomediated cascade reaction of electron-rich 1,7-enynes

Abstract

Synthesis of various sulfonyl- and trifluoromethyl-decorated tetracyclic indeno-quinolines from 1,7-enynes via a cascade radical addition–cyclization–aromatization sequence is presented. The reaction was found to show broad substrate scope with good functional group tolerance on the sulfonyl and o-alkynyl aniline derivatives. The protocol was successfully extended for late-stage modification of various sulfonyl-containing drugs and other radical precursors to obtain the corresponding indeno-quinolines in good yields. Control experiments corroborated the proposed photomediated radical cascade mechanism.