Lewis acid platinum complexes of conformationally flexible NUPHOS diphosphines: Highly efficient catalysts for the carbonyl-ene reaction

Simon Doherty, Peter Goodrich, Christopher Hardacre, He-Kuan Luo, Mark Nieuwenhuyzen, Rakesh Rath

Research output: Contribution to journalArticlepeer-review

46 Citations (Scopus)

Abstract

Enantiopure Lewis acid complexes of conformationally flexible acyclic and monocyclic NUPHOS diphosphines, delta- and lambda-[(NUPHOS)Pt(OTf)(2)], are efficient catalysts for the carbonyl-ene reaction between various unsymmetrical 1,1'-disubstituted alkenes and phenylglyoxal or ethyl glyoxylate. While catalyst performance was substrate dependent, ee values as high as 95% and yields up to 90% have been obtained. In a number of cases catalysts generated from delta- and lambda-[(NUPHOS)Pt{(S)-BINOL}] showed marked enhancements in enantioselectivity in ionic liquids compared with organic media. Although an enhancement in enantioselectivity was not obtained for all substrate combinations in such cases, the enantioselectivities were comparable to those obtained in dichloromethane. Furthermore, although the ee's are initially comparable in both the ionic liquid and dichloromethane, a gradual erosion of ee with time was found in the organic solvent, whereas the ee remained constant in the ionic liquid. Preliminary kinetic investigations suggest that the decrease in ee may be due to a faster racemization of the catalyst in dichloromethane compared with the ionic liquid.
Original languageEnglish
Pages (from-to)5945-5955
Number of pages11
JournalOrganometallics
Volume24 (24)
Issue number24
DOIs
Publication statusPublished - 21 Oct 2005

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Organic Chemistry

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