N-Heterocyclic Carbenes in Asymmetric Organocatalysis: Methods and Applications

Asymmetric organocatalysis with N -Heterocyclic carbenes (NHCs) has been recognized as a powerful platform for diverse transformations exploiting both umpolung and non-umpolung reactivity. Recently, the role of NHCs has been expanded to explore both new modes of substrate activation and integration with emerging strategies, including radical, photochemical and electrochemical methods, as well as synergistic catalysis (with transition metals) and cascade (domino) reactions. Despite the progress made, some challenges still remain, such as chemoselectivity, enantioselectivity and catalyst efficiency, allowing for significant potential future developments in this field.