Chemical CO2 Fixation: Cr(III) and Co(III) Salen Complexes as Highly Efficient Catalysts for the Coupling of CO2 and Epoxides (21048)

New highly active Cr(III)- and Co(III) catalyst systems for the coupling of CO2 and terminal epoxides to cyclic carbonates under extremely mild conditions. Carbon dioxide is an attractive and economical C1 building block in organic synthesis and carbonates are versatile chemical intermediates. However to date, catalyst systems that convert CO2 to cyclic carbonates via the metal-catalyzed coupling of CO2 and epoxides, have been limited by reactivity/stability problems and demanding operating conditions. This invention presents catalytic systems and conditions suited for the commercial implementation of this chemistry.

ADVANTAGES: A high yield and selective conversion of CO2 and epoxides to cyclic carbonates in a potentially economic catalytic process. Cyclic carbonate chemicals and intermediates are valuable in commodity, pharmaceutical, and fine chemical production.

SUMMARY: Carbon dioxide is an attractive C1 building block in organic synthesis as it is highly functional, abundant, inexpensive, nontoxic, and nonflammable. As petroleum reserves are depleted, efficient catalytic processes employing CO2 as a feedstock are increasingly important. A promising development is the synthesis of cyclic carbonates via the metal-catalyzed coupling of CO2 and epoxides. Cyclic carbonates are valuable as monomers, solvents, chemical intermediates, and in biomedical applications. In recent decades numerous catalyst systems have been developed for this transformation. However results to date exhibit low catalyst reactivity/stability, air sensitivity, the need for co-solvents, and high pressure and/or high temperature processing.

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The present invention provides a family of Cr(III)- and Co(III) catalysts yielding cyclic carbonates from the coupling of CO2 and terminal epoxides under extremely mild conditions. Thus, propylene oxide reacts with CO2 in the presence of these complexes to quantitatively afford propylene carbonate. The reaction can be run with or without solvent, at modest temperatures (25-100°C), CO2 pressures (1-5 atm), and low catalyst level (0.075 mol%). The catalysts quantitatively afford propylene carbonate at high turn over frequency and excellent catalyst life. These catalyst systems are applicable to a variety of terminal epoxides, providing the corresponding cyclic carbonates in high yield and 100% selectivity. The catalysts have been tuned to selectively convert racemic epoxide precursors to enantiomerically enriched cyclic carbonates. Systems for the direct conversion of epoxide monomers to polycarbonates have also been identified. These Cr(III)- and Co(III)-based catalysts present a unique system with broad synthetic and commercial potential.

STATUS: Sample catalysts have been produced, characterized and key process variables elucidated. U. S. Patent No. 6,870,004 has issued.

Type of Offer: Licensing



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