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

Abstract

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(sp²)-F bond transformation of gem-difluoroalkenes through oxyindation/β-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(sp³)-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.