Ambiphilicity of ring-expanded N-heterocyclic carbenes
François Vermersch, Victor T. Wang, Mehdi Abdellaoui, Rodolphe Jazzar, Guy Bertrand
Abstract
N-heterocyclic carbenes, such as imidazole-2-ylidenes and imidazolin-2-ylidenes, the popular class of singlet carbenes introduced by Arduengo in 1991 have not been shown to be ambiphilic owing to the two σ-withdrawing, π-donating amino groups flanking the carbene centre. However, our experimental data suggest that ring-expanded N-heterocyclic carbenes (RE-NHCs), especially the seven and eight membered rings, are significantly ambiphilic. Our results also show that the steric environment in RE-NHCs can become a determining factor for controlling the E-H bond activation.
Topics & Concepts
CarbeneImidazoleSteric effectsRing (chemistry)ChemistryMedicinal chemistryStereochemistrySinglet stateOrganic chemistryCatalysisPhysicsExcited stateNuclear physicsN-Heterocyclic Carbenes in Organic and Inorganic ChemistryCatalytic Cross-Coupling ReactionsSynthesis and characterization of novel inorganic/organometallic compounds