An Overview of N-heterocyclic carbene: Properties and Applications

N-Heterocyclic carbenes are regarded as neutral compounds containing a divalent carbon atom with a six-electron valence shell, carbenes are an intriguing class of carbon-containing compounds. The successful isolation and characterization of an N-heterocyclic carbene in 1991 opened up a new class of organic compounds for investigation. They are cyclic molecules that contain one carbene and at least one nitrogen atom within the carbene-containing ring structure. These molecules are widely used as ancillary ligands for the preparation of transition-metal-based catalysts and also possess a unique characteristic feature i.e. Umpolung nature. The underlying principle of many of the NHC-catalyzed reactions is the remarkable ability of NHCs to reverse the normal mode of reactivity of aldehydes (umpolung). NHCs can catalyze transformations proceeding via the umpolung or nonumpolung mode for the synthesis of various functionalized molecules.