Photoredox-Catalyzed Tandem Insertion/Cyclization Reactions of Difluoromethyl and 1,1-Difluoroalkyl Radicals with Biphenyl Isocyanides

Using visible-light photoredox conditions, difluoromethylation and 1,1-difluoroalkylation of biphenyl isocyanides have allowed the synthesis of a series of 6-(difluoromethyl)- and 6-(1,1-difluoroalkyl)phenanthridines via tandem addition/cyclization/oxidation processes. The reactions are carried out in wet dioxane at room temperature using fac-Ir(ppy)3 as catalyst to form a large variety of substituted phenanthridine products in good to excellent yield.