Continuous-Flow Photocatalysis for the Direct C-H Trifluoromethylation of Heterocycles with an Organic Photoredox Catalyst

Abstract

Photocatalysis for direct C−H trifluoromethylation represents an ideal way to synthesize trifluoromethyl-containing chemical compounds, but the conventional batch processes are inefficient with limited light penetration and indispensably irradiated for a long while. Herein, we report a continuous-flow protocol for photocatalytic direct C−H trifluoromethylation of heterocycles in the presence of an organic photoredox catalyst: 2,4,6-tris(diphenylamino)-3,5-difluorobenzonitrile (3DPA2FBN). In this approach, benefiting from the merger of organic photoredox catalysis and continuous-flow techniques, a variety of trifluoromethylated heterocycles were rapidly synthesized up to 85 % yield with 80 min residence time under metal- and oxidant-free reaction conditions.