n-heterocyclic carbene–supported transition-metal catalysts for c–h functionalization: sustainable pathway for value-added chemicals

Value-added organic compounds, such as serotonin, vibsanol, moracin m, etc. can be conveniently synthesized utilizing c-h bond activation and subsequent functionalization reactions. this c-h functionalization route aligns well with the green synthetic strategy as it has greater atom and energy economy. usually, these reactions require catalysts, among which the transition metal-based ones have been investigated by many research groups; a detailed discussion of which is presented here. homogeneously catalyzed c-h functionalization reactions often require fine-tuning of the transition metal complexes. in this regard, the n-heterocyclic carbene (nhc) based ligands possess excellent characteristics as ancillary ligands. nhc ligands can be easily synthesized and modified to design suitable transition metal catalysts with great structural variety. various abundant transition metals, such as ni, cu, co as well as rare metals such as pd and ru, have been explored as catalysts for c-h functionalization reactions. these transition metal catalysts help to decrease the kinetic barriers in c-h bond activation. these complexes have successfully activated the c-h bonds through both intramolecular and intermolecular reactions. such catalytic pathways have provided an easy route to convert many abundant molecules to value-added products. herein, this article discusses the synthetic strategy of converting readily available molecules into various value-added products by the catalytic transition metal-nhc complexes through c-h functionalization reactions.