Recyclable Ligand-Free Cobalt Catalyst for Alkoxycarbonylation of Chloroacetates

Direct carbonylation of the C(sp³)Cl bond remains a challenging transformation in the chemical industry. The usual use of precious metals, the high cost of ligands, and the lack of recyclability of catalysts make their industrial application on a large scale impossible. A ligand-free cobalt-based catalyst for the alkoxycarbonylation of chloroacetates to dialkyl malonates, which are important industrial intermediates, is reported here. This catalyst uses an extremely inexpensive precursor, CoCO₃, with a very low catalyst loading (0.5 mol%) to achieve product yields of up to 99% with nearly 100% chemoselectivity. Solvents and previously essential phase transfer agents are not needed. Most importantly, the catalyst can be easily recycled without losing its activity and selectivity. Over 95% product yield is achieved even after 8 recycles. The feasibility of this system is demonstrated through 14 examples of the alkoxycarbonylation reaction. Fourier transform infrared spectroscopy investigations identified the active cobalt species as [Co(CO)₄]^-. As the first recyclable cobalt-based catalyst, this ligand-free system has great potential for large-scale industrial transfer.