Synthesis of aryl ring-fused benzimidazolequinones using 6- exo- trig radical cyclizations

Abstract

The preparation of alicyclic ring-fused tetracyclic and pentacyclic benzimidazoles containing one and two fused aryl rings, respectively, is achieved conveniently in three steps, including Bu 3SnH-mediated 6- exo- trig cyclization of σ-aryl radicals generated from 1-allyl-2-(ω-bromoaryl)benzimidazoles. Inclusion of 4,7-dimethoxy substituents on the radical precursors allows access to aryl ring-fused benzimidazolequinones, a unique family of potential bioreductive anti-cancer agents.