Activation of C–F, Si–F, and S–F Bonds by N-Heterocyclic Carbenes and Their Isoelectronic Analogues
Eunsung Lee, Ewa Pietrasiak
Abstract
Reactions involving C–F, Si–F, and S–F bond cleavage with N-heterocyclic carbenes and isoelectronic species are reviewed. Most examples involve activation of aromatic C–F bond via an SNAr pathway and nucleophilic substitution of fluorine in electron-deficient olefins. The mechanism of the C–F bond activation depends on the reaction partners and the reaction can proceed via addition–elimination, oxidative addition (concerted or stepwise) or metathesis. The adducts formed upon substitution find applications in organic synthesis, as ligands and as stable radical precursors, but in most cases, their full potential remains unexplored. 1 Introduction 1.1 The C–F Bond 1.2 C–F Bond Activation: A Short Summary 1.3 C–F Bond Activation: A Special Case of SNAr 1.4 N-Heterocyclic Carbenes (NHCs) 1.5 The Purpose of this Article 2 C–F bond Activation in Acyl Fluorides 3 Activation of Vinylic C–F Bonds 4 Activation of Aromatic C–F Bonds 5 X–F Bond Activation (X = S or Si) 6 C–F Bond Activation by Main Group Compounds Isoelectronic with NHCs 7 Conclusions and Outlook