Novel polymeric and oligomeric Co(salen) complexes as highly reactive and enantioselective catalysts for the hydrolytic kinetic resolution of epoxides

ORGN 33

Xiaolai Zheng, xiaolai.zheng@chemistry.gatech.edu1, Christopher W. Jones, christopher.jones@chbe.gatech.edu2, and Marcus Weck, marcus.weck@chemistry.gatech.edu1. (1) School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400, (2) School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Drive, NW, Atlanta, GA 30332-0400
We describe the synthesis and catalytic properties of the poly(styrene)- and oligo(cyclooctene)-supported Co(salen) complexes with the salen moieties being immobilized in a flexible pedant fashion. The poly(styrene)-supported salen ligands were prepared via the free radical polymerization of an unsymmetrical styryl-substituted salen monomer and the loading of the salen can be controlled readily by the copolymerization with styrene. The polymers were metallated with Co(OAc)2 to give the corresponding polymeric Co(salen) complexes that were used as active recyclable catalysts in the hydrolytic kinetic resolution (HKR) of epichlorohydrin. The Ru-catalyzed olefin metathesis of an unsymmetrical cyclooct-4-enyl-substituted Co(salen) compound generated novel oligomeric cyclic Co(salen) complexes. By enforcing the fast intramolecular bimetallic cooperative mechanism in the HKR, the oligo(cyclooctene)-supported Co(salen) catalysts exhibited extremely high catalytic reactivity and enantioselectivity in the resolution of a variety of epoxides. The structure-reactivity relationship is discussed that would lead to the general guidance for the design of HKR catalysts.
 

Asymmetric Reactions and Syntheses
8:00 AM-11:40 AM, Sunday, 26 March 2006 Georgia World Congress Center -- C302, Oral

Division of Organic Chemistry

The 231st ACS National Meeting, Atlanta, GA, March 26-30, 2006