Poly(styrene)-supported co-salen complexes as efficient recyclable catalysts for the hydrolytic kinetic resolution of epichlorohydrin

Xiaolai Zheng, Christopher W. Jones, Marcus Weck

Research output: Contribution to journalArticle

Abstract

Here we describe an unprecedented synthetic approach to poly-(styrene)-supported chiral salen ligands by the free radical polymerization of an unsymmetrical styryl-substituted salen monomer (H2salen = bis(salicylidene)ethylenediamine). The new method allows for the attachment of salen moieties to the polymer main chain in a flexible, pendant fashion, avoiding grafting reactions that often introduce ill-defined species on the polymers. Moreover, the loading of the salen is controlled by the copolymerization of the styryl-substituted salen monomer with styrene in different ratios. The polymeric salen ligands are metallated with cobalt(II) acetate to afford the corresponding supported Co-salen complexes, which are used in the hydrolytic kinetic resolution of racemic epichlorohydrin, exhibiting high reactivity and enantioselectivity. Remarkably, the copolymer-supported Co-salen complexes showed a better catalytic performance (>99% ee, 54 % conversion, one hour) in comparison to the homopolymeric analogues and the small molecule Co-salen complex. The soluble poly(styrene)-supported catalysts were recovered by precipitation after the catalytic reactions and were recycled three times to afford almost identical enantiomeric excesses as the first run, with slightly reduced reaction rates.

Original languageEnglish (US)
Pages (from-to)576-583
Number of pages8
JournalChemistry - A European Journal
Volume12
Issue number2
DOIs
StatePublished - Dec 23 2005

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Keywords

  • Asymmetric catalysis
  • Cobalt
  • Kinetic resolution
  • Polymerization
  • Supported catalysts

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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