Diethylene glycol-functionalized imidazo[1,5-a]pyridin-3-ylidenes (DEG-ImPy) have been developed as bifunctional N-heterocyclic carbene ligands. The DEG-ImPy Cu(i) complexes efficiently catalyzed the direct C-H carboxylation of benzoxazole with CO2, showing higher isolated yields than those with the N,N′-(2,6-diisopropylphenyl)imidazolylidene Cu catalyst.
Park, D. A., Ryu, J. Y., Lee, J., & Hong, S. (2017). Bifunctional N-heterocyclic carbene ligands for Cu-catalyzed direct C-H carboxylation with CO2. RSC Advances, 7(83), 52496–52502. https://doi.org/10.1039/c7ra11414a