Main-Group Lewis Acids for C–F Bond Activation

Abstract

The significant benefits of fluorinated compounds have inspired the development of diverse techniques for the activation and subsequent (de)functionalization of rather inert C–F bonds. Although substantial progress has been made in the selective activation of C(sp 2 )–F bonds employing transition metal complexes, protocols that address nonactivated C(sp 3 )–F bonds are much less established. In this regard, the use of strong main-group Lewis acids has emerged as a powerful tool to selectively activate C(sp 3 )–F bonds in saturated fluorocarbons. This Perspective provides a concise overview of various cationic and neutral silicon-, boron-, and aluminum-based Lewis acids that have been identified to facilitate the heterolytic fluoride abstraction from aliphatic fluorides. The potential of these Lewis acids in hydrodefluorination as well as defluorinative C–F bond functionalization reactions is highlighted. Emphasis is placed on the underlying mechanistic principles to provide a systematic classification of the individual reactions. Finally, brief insight into the related C–F bond activation chemistry using carbocations or Brønsted acids is presented.