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. We report here a ligand-free cobalt-based catalyst for the alkoxycarbonylation of chloroacetates to dialkyl malonates, which are important industrial intermediates. 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 was achieved even after 8 recycles. The feasibility of this system was demonstrated through 14 examples of the alkoxycarbonylation reaction. FTIR 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.