N-Heterocyclic Carbenes in Late Transition Metal Catalysis

N-heterocyclic carbenes (NHC) are cyclic carbenes bearing at least one α-amino substituent that have marked the field of late transition metal catalysis. Their ability to stabilize otherwise highly reactive intermediates and yet promote and enhance constructive chemical steps at the metal center has been important in their extremely rapid development. Presently, in terms of catalytic applications with NHCs, late transition metals can be divided into four categories, including the heavyweights (Ru, Rh, Ni, and Pd), the well-established (Ir, Pt, Cu, and Au), the underdeveloped (Fe, Os, Co, and Ag), and the nonexistents (Mn, Tc, and Re). Great achievements have already been made in the fields of cycloisomerization and hydrofunctionalization. The ability of NHCs to stabilize important catalytic intermediates and yet to promote subsequent reaction in the coordination sphere of gold will surely lead to exciting discoveries.