Fluorine-Retentive Strategies for the Functionalization of gem-Difluoroalkenes

Abstract gem-Difluoroalkenes are readily available fluorinated building blocks, and the fluorine-induced electronic perturbations of the alkenes enable a wide array of selective functionalization reactions. However, many reactions of gem-difluoroalkenes result in a net C–F functionalization to generate monofluorovinyl products or addition of F to generate trifluoromethyl-containing products. In contrast, fluorine-retentive strategies for the functionalization of gem-difluoroalkenes remain less generally developed and is now becoming a rapidly developing area. This review will present the development of fluorine-retentive strategies including electrophilic, nucleophilic, radical, and transition metal catalytic strategies with an emphasis on key physical organic and mechanistic aspects that enable reactivities. 1 Introduction 2 Two-Electron Processes 2.1 Elimination of Allyl Groups 2.2 Electrophilic Addition 2.3 Halonium and Thiiranium Intermediates 2.4 Kinetic Quench of Anionic Intermediates 2.5 Concerted Cycloadditions 3 Radical Processes 3.1 Thermal Activation 3.2 Photoactivation 3.3 Transition-Metal-Mediated 4 Reductions 5 Cross-Coupling Reactions 6 Conclusions