Rapid trifluoromethylation and perfluoroalkylation of five-membered heterocycles by photoredox catalysis in continuous flow

Abstract

Trifluoromethylated and perfluoroalkylated heterocycles are important building blocks for the synthesis of numerous pharmaceutical products, agrochemicals and are widely applied in material sciences. To date, trifluoromethylated and perfluoroalkylated hetero-aromatic systems can be prepared utilizing visible light photoredox catalysis methodologies in batch. While several limitations are associated with these batch protocols, the application of microflow technology could greatly enhance and intensify these reactions. A simple and straightforward photocatalytic trifluoromethylation and perfluoroalkylation method has been developed in continuous microflow, using commercially available photocatalysts and microflow components. A selection of five-membered hetero-aromatics were successfully trifluoromethylated (12 examples) and perfluoroalkylated (5 examples) within several minutes (8-20 min). Photo workflow: A simple and straightforward photocatalytic method for perfluoroalkylation in continuous flow is developed. A photo-microreactor, constructed from commercially available components, enables accelerated photocatalysis employing [Ru(bpy)3Cl2] as photocatalyst under irradiation by blue LED light. A series of electron-rich hetero-aromatics is successfully trifluoromethylated within 8-16 min. Also, a selection of hetero-aromatics is perfluoroalkylated within 10-20 min. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.