Photocatalytic fluoroalkylations of (hetero)arenes enabled by the acid-triggered reactivity umpolung of acetoxime esters

The importance of trifluoromethyl (CF3) group-containing compounds in pharmaceuticals, agrochemicals, and materials has spurred tremendous efforts devoted to the development of methods for incorporation of the trifluoromethyl group into molecular frameworks and discoveries of trifluoromethylating reagents. In this paper, we report a general photocatalytic method for regioselective C–H fluoroalkylation of (hetero)arenes and olefines that uses readily available fluoroalkyl carboxylic anhydrides as fluoroalkylating reagents in the presence of simple acetoxime as an activator. The success achieved in the development of such a photocatalytic C–H fluoroalkylation method is attributed to discovery of the unprecedented acid-triggered reactivity umpolung of acetoxime ester toward single-electron reduction-induced cleavage of N–O σ bond. Such a new reactivity mode of oxime esters will stimulate efforts to expand the synthetic applications of readily available oxime esters.