Mendoza-Espinosa, D.; Donnadieu, B.; Bertrand, G. Synthesis of a Variety of 4,5-Functionalized Imidazol-2-Ylidenes from a Single 4,5-Unsubstituted Imidazol-2-Ylidene. J. Am. Chem. Soc. 2010, 132, 7264-7265.
Using the nucleophilicity of NHCs and aNHCs, as well as the leaving group ability of the former, the carbon?carbon double bond of imidazol-2-ylidenes can be readily mono- and difunctionalized. These results provide also a new light on the formation of abnormal carbene adducts from classical unsaturated NHCs.