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Lookup NU author(s): Dr Simon DohertyORCiD, Dr Rakesh Rath
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Enantiopure Lewis acid complexes of conformationally flexible acyclic and monocyclic NUPHOS diphosphines, δ- and λ-[(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 δ- and λ-[(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. © 2005 American Chemical Society.
Author(s): Doherty S, Goodrich P, Hardacre C, Luo H-K, Nieuwenhuyzen M, Rath RK
Publication type: Article
Publication status: Published
Journal: Organometallics
Year: 2005
Volume: 24
Issue: 24
Pages: 5945-5955
ISSN (print): 0276-7333
ISSN (electronic): 1520-6041
Publisher: American Chemical Society
URL: http://dx.doi.org/10.1021/om0505716
DOI: 10.1021/om0505716
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