Mild C−F Activation in Perfluorinated Arenes through Photosensitized Insertion of Isonitriles at 350 nm

Fluorinated compounds have become important in the fields of agrochemical industry, pharmaceutical chemistry and materials sciences. Accordingly, various methods for their preparation have been developed in the past. Fluorinated compounds can be accessed via conjugation with fluorinated building blocks, via C−H fluorination or via selective activation of perfluorinated compounds to give the partially fluorinated congeners. Especially the direct activation of C−F bonds, one of the strongest σ‐bonds, still remains challenging and new strategies for C−F activation are desirable. Herein a method for the photochemical activation of aromatic C−F bonds is presented. It is shown that isonitriles selectively insert into aromatic C−F bonds while aliphatic C−F bonds remain unaffected. Mechanistic studies reveal the reaction to proceed via the indirect excitation of the isonitrile to its triplet state by photoexcited acetophenone at 350 nm. Due to the relatively mild light used, the process shows high functional group tolerance and various compounds of the class of benzimidoyl fluorides are accessible from aryl isonitriles and commercially available perfluorinated arenes.