Transition-metal-catalyzed reactions promoted by cyclic (alkyl or aryl)(amino)carbene ligands

Summary

Cyclic (alkyl or aryl)aminocarbenes (CAACs/CArACs) have been prepared by replacement of one of the amino substituents of normal (diamino)carbenes (NHCs) by alkyl or aryl scaffolds, showing stronger nucleophilicity and electrophilicity than commonly used phosphine and NHC ligands. As a result, their use in tuning the electronic properties and steric environments of coordinated metals in catalytic reactions is of great interest. Significant progress in the field has been made, showing the interesting ability of CAACs/CArACs as ligands in promoting organic reactions. A broad range of catalytic reactions, including hydroamination, hydrogenation, olefin metathesis, borylation, and other transformations, have been developed with CAAC/CArAC ligands addressing the synthetic challenges associated with molecular construction. This review demonstrates the development of organic reactions with CAAC/CArAC ligands from the view of synthetic chemistry, focusing on the discussion and elucidation of related mechanisms for insight into the discovery of new reactions.