Bifunctional N-heterocyclic carbene ligands for Cu-catalyzed direct C-H carboxylation with CO2Electronic supplementary information (ESI) available. CCDC 1576746 and 1576622. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7ra11414a

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 CO 2 , showing higher isolated yields than those with the N , N ′-(2,6-diisopropylphenyl)imidazolylidene Cu catalyst. A copper-catalyzed direct C-H carboxylation of heteroarene compounds using diethylene glycol-functionalized imidazo[1,5, a ] pyridin-3-ylidene (DEG-ImPy) ligands has been developed.