Lewis Acid-mediated Carbon- Fluorine Bond Transformation: Substitution of Fluorine and Insertion into a Carbon-Fluorine Bond

In recent years, carbon-fluorine (C- F) bond transformation for organic synthesis has been remarkably developed. Herein, we describe four types of C- F bond transformation mediated by Lewis acids: (1) C(sp(2))- F bond transformation of gem difluoroalkenes through oxyindation/beta - fluorine elimination to afford fluorinated isocoumarins; (2) B(C6F5)(3)- catalyzed substitution of fluorine in 1 fluorostyrenes with silyl ketene acetals via abstraction of F - by in situ generated silylium ions; (3) BF3- catalyzed formal insertion of diazoesters into the C- F bonds of benzylic fluorides; and, (4) photoredox catalyst/Lewis acidic Sn species-mediated C(sp(3)) - F bond allylation of perfluoroalkylarenes. Density functional theory (DFT) study of the reaction mechanisms suggests the importance of choosing the appropriate Lewis acid to achieve an appropriate activation method for the C- F bonds in each reaction.