Efficient heterogeneous asymmetric catalysis of the Mukaiyama aldol reaction by silica- and ionic liquid-supported Lewis acid copper(II) complexes of bis(oxazolines)

S. Doherty, Peter Goodrich, Christopher Hardacre, V. Parvulescu, Cristina Paun

Research output: Contribution to journalArticlepeer-review

60 Citations (Scopus)

Abstract

Lewis acid complexes based on copper(II) and an imidazolium-tagged bis(oxazoline) have been used to catalyse the asymmetric Mukaiyama aldol reaction between methyl pyruvate and 1-methoxy-1-tri-methylsilyloxypropene under homogeneous and heterogeneous conditions. Although the ees obtained in ionic liquid were similar to those found in dichloromethane, there was a significant rate enhancement in the ionic liquid with reactions typically reaching completion within 2 min compared with only 55% conversion after 60 min in dichloromethane. However, this rate enhancement was offset by lower chemoselectivity in ionic liquids due to the formation of 3-hydroxy-1,3-diphenylbutan-1-one as a by-product. Supporting the catalyst on silica or an imidazolium-modified silica using the ionic liquid or in an ionic liquid-diethyl ether system completely suppressed the formation of this by-product without reducing the enantioselectivity. Although the heterogeneous systems were characterised by a drop in catalytic activity the system could be recycled up to five times without any loss in conversion or ee.
Original languageEnglish
Pages (from-to)295-302
Number of pages8
JournalAdvanced Synthesis & Catalysis
Volume350 (2)
Issue number2
DOIs
Publication statusPublished - Jan 2008

ASJC Scopus subject areas

  • Catalysis
  • Chemistry (miscellaneous)
  • Organic Chemistry

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