Rhodium()-catalyzed C-H carboxylation of ferrocenes with CO

Carbon dioxide (CO 2 ) is considered as a green and renewable C1 feedstock. However, due to its thermodynamic and kinetic stability, transition metal-catalyzed carboxylation of unactivated C-H bonds with CO 2 still remains challenging. Herein, a protocol for Rh( ii )-catalyzed and CO 2 -involved carboxylation of inert sp 2 C-H bonds from the cyclopentadienyl (Cp) ring of ferrocene derivatives was reported, which produces a series of ferrocene-embedded lactones that are important molecular skeletons widely used in pharmaceuticals or ligands. Moreover, moderate enantioselectivity was achieved with a chiral NHC ligand, which can be regarded as the first example for asymmetric C-H carboxylation with CO 2 . Preliminary mechanistic experiments supported bivalent rhodium as the real active catalyst, and a reasonable catalytic cycle was proposed accordingly. Rh( ii )-catalyzed C-H carboxylation of ferrocene derivatives with CO 2 was developed. The first example of CO 2 -involved asymmetric C-H carboxylation was achieved with moderate enantioselectivity.