Carbenes and Nitrenes

This Chapter Contains Sections titled: Reviews Generation, Structure, and Reactivity Carbenes in Coordination Chemistry Carbene Complexes with Main Group Elements Carbene Complexes with Transition Metals Addition–Fragmentations Free Carbenes or Main Group Carbenoid Reactions Transition Metal-assisted Reactions Insertion–Abstraction Free Carbenes or Carbenoid Reactions Transition Metal-assisted Reactions Rearrangements Free Carbenes or Carbenoid Reactions Transition Metal-assisted Reactions Nucleophilic Carbenes–Carbenes as organocatalysts Transformations Mediated by Breslow-type Intermediates Transformations Non-mediated by Breslow-type Intermediates Nitrenes Free Nitrenes – Generation and Reactivity Transition Metal-assisted Reactions Higher Carbene Analogues References This chapter provides a wide coverage of the finest insights on the reactivity of carbenes and diazirines. It focuses on the energies of activation of electrophilic and nucleophilic carbenes. The chapter also focuses on the physical organic chemistry of carbenes provides an illustration of enthalpy–entropy compensation, which allows the understanding of carbene–alkene additions with very low energies of activation of reactions involving electrophilic carbenes. In the coordination chemistry of carbene, the steric bulk of N-heterocyclic carbene (NHC) ligands has been detailed through quantified approaches such as ‘percent buried volume’ and ‘steric maps’. The chapter reviews the influence of the steric bulk in the context of palladium–NHC complexes with regard to their abilities to perform challenging coupling involving hindered substrates. It provides numerous examples for benzoin coupling, Stetter reactions, esterification and amidation reactions, substitutions and oligomerizations, as well as arene and coumarin syntheses.