Photoredox-Catalyzed Radical Cascade Cyclization with Carboxylic Anhydrides to Access CF2H/CF2Cl-Substituted Indolo- and Benzimidazo[2,1-a]isoquinolin-6(5H)-Ones.

An efficient photocatalytic protocol for difluoro- and chlorodifluoromethyl radical-triggered cyclization of alkenyl-tethered 2-aryl indoles/benzimidazoles was developed using commercially available, low-cost carboxylic anhydrides as CF2H/CF2Cl sources and simple acetoxime as the activating reagent. This reaction engages free C3-H indole substrates that were previously challenging. It features broad substrate scope and good functional-group tolerance, delivering more than 50 examples of high-value CF2H/CF2Cl-containing indolo- and benzimidazo[2,1-a]isoquinolin-6(5H)-ones in good yields.