Blue-light special on perfluoroalkylations

Abstract

Direct trifluoromethylation of aromatic rings is an important synthetic tool for chemists. Although an abundance of new methods that use less harsh reagents, have improved product selectivity, and minimize waste have been reported during the past decade, cost-effective scalable processes have remained underdeveloped. Corey R. J. Stephenson and his coworkers at the University of Michigan in collaboration with process chemistry researchers at Eli Lilly & Co. may have found a solution. The team has designed a scaled up photochemical flow reactor that employs an inexpensive reagent combination under mild conditions to produce kilogram amounts of trifluoromethylated arenes and heteroarenes (Chem 2016, DOI: 10.1016/j.chempr.2016.08.002). The researchers use 4-phenylpyridine N-oxide as a redox trigger that is activated by a blue light-absorbing ruthenium bipyridine catalyst. This photoredox system decarboxylates trifluoroacetic anhydride to generate a trifluoromethyl radical that reacts with an arene or heteroar...