A Review on the Halodefluorination of Aliphatic Fluorides

Abstract Halodefluorination of alkyl fluorides using group 13 metal halides has been known for quite some time (first reported by Newman in 1938) and is often utilized in its crude stoichiometric form to substitute fluorine with heavier halogens. However, recently halodefluorination has undergone many developments. The reaction can be effected with a range of metal halide sources (including s-block, f-block, and p-block metals), and has been developed into a catalytic process. Furthermore, methods for monoselective halodefluorination in polyfluorocarbons have been developed, allowing exchange of only a single fluorine with a heavier halogen. The reaction has also found use in cascade processes, where the final product may not even contain a halide, but where the conversion of fluorine to a more reactive halogen is a pivotal reaction step in the cascade. This review provides a summary of the developments in the reaction from its inception until now. 1 Introduction 2 Stoichiometric Halodefluorination 2.1 Group 13 Halodefluorination Reagents 2.2 Other Metal Halide Mediated Halodefluorination 3 Catalytic Halodefluorination 4 Monoselective Halodefluorination 5 Cascade Reactions Involving Halodefluorination 6 Summary and Outlook