Kinetic resolution of racemic {alpha}-olefins with ansa-zirconocene polymerization catalysts: Enantiomorphic site vs. chain end control
- Creators
- Byers, Jeffery A.
- Bercaw, John E.
Abstract
Copolymerization of racemic {alpha}-olefins with ethylene and propylene was carried out in the presence of enantiopure C1-symmetric ansa metallocene, {1,2-(SiMe2)2({eta}5-C5H-3,5-(CHMe2)2)({eta}5-C5H3)}ZrCl2 to probe the effect of the polymer chain end on enantioselection for the R- or S-{alpha}-olefin during the kinetic resolution by polymerization catalysis. Copolymerizations with ethylene revealed that the polymer chain end is an important factor in the enantioselection of the reaction and that for homopolymerization, chain end control generally works cooperatively with enantiomorphic site control. Results from propylene copolymerizations suggested that chain end control arising from a methyl group at the beta carbon along the main chain can drastically affect selectivity, but its importance as a stereo-directing element depends on the identity of the olefin.
Additional Information
© 2006 by the National Academy of Sciences. Edited by Tobin J. Marks, Northwestern University, Evanston, IL, and approved July 21, 2006 (received for review April 18, 2006). Published online on October 10, 2006, 10.1073/pnas.0603071103. We thank Julia Kornfield and Lucia Fernandez-Ballester for DSC instrumentation and help with thermograph interpretation and Steven Cohen and Jerome Streeky at BP Chemicals (now Ineos) for molecular weight measurements. This work was supported by the National Science Foundation and the Department of Energy. Author contributions: J.A.B. and J.E.B. designed research; J.A.B. performed research; J.A.B. and J.E.B. analyzed data; and J.A.B. and J.E.B. wrote the paper. Conflict of interest statement: No conflicts declared. This article is a PNAS direct submission.Attached Files
Published - BYEpnas06.pdf
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Additional details
- PMCID
- PMC1622822
- Eprint ID
- 9958
- Resolver ID
- CaltechAUTHORS:BYEpnas06
- NSF
- Department of Energy (DOE)
- Created
-
2008-03-28Created from EPrint's datestamp field
- Updated
-
2021-11-08Created from EPrint's last_modified field