Lithium Chloride Carbenoids in Bond Activation Reactions

Abstract

The field of transition-metal-free bond activation reactions has grown rapidly over the past years. In this context, lithium carbenoids have received renewed interest because of their unique electronic properties and their ambiphilic character. Stabilization of these usually highly reactive and thermally labile compounds has allowed the isolation of species that are stable at room temperature and enabled the development of new applications. In this article, we highlight the latest advances in the stabilization of Li/Cl carbenoids and their use in bondactivation chemistry. 1 Introduction 2 Classical Carbenoid Chemistry 3 Isolation and Properties of Li/Cl Carbenoids 4 Reactivity towards Boranes: B-X Bond Activation Reactions 5 Reactivity towards Phosphines 6 Conclusions

Synthesis, Characterization, and Trapping of a Cyclic Diborylcarbene, an Electrophilic Carbene

“…In 1958, Simmons and Smith invented a synthetic carbene equivalent, carbenoid, wherein the carbon atom was bound to both a metal cation and a (pseudo)­halogen (Figure b, left) . Since the use of zinc carbenoid I-CH 2 -ZnI for cyclopropanation, carbenoid has been widely used as a stable synthetic equivalent to carbene. − Efforts have also been devoted to isolation and characterization of carbenoids. − In addition to stable Li, Mg, and Zn carbenoids, recently, Gessner’s research group successfully isolated heavier alkali-metal (Na, K) carbenoids. − …”

A practical guide for using lithium halocarbenoids in homologation reactions

“…It is important to stress that carbenoids of lithium and magnesium, because of their excellent nucleophilicity, do react predominantly as carbanions [6, 13–16]. On the other hand, less nucleophilic carbenoids such as zinc or rhodium linked ones exhibit preferentially an electrophilic behavior [4, 22].…”