Enantioselective hydrogenation over cinchona-modified Pt: the special role of carboxylic acids.
Journal article

Enantioselective hydrogenation over cinchona-modified Pt: the special role of carboxylic acids.

  • von Arx M Laboratory of Technical Chemistry, Swiss Federal Institute of Technology, ETH-Hönggerberg HCI, Wolfgang Pauli Strasse, 8093 Zürich, Switzerland.
  • Bürgi T
  • Mallat T
  • Baiker A
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  • 2002-03-29
Published in:
  • Chemistry (Weinheim an der Bergstrasse, Germany). - 2002
English The influence of acetic acid (AcOH) and trifluoroacetic acid (TFA) on the hydrogenation of ethyl-4,4,4-trifluoroacetoacetate has been investigated by using Pt/Al(2)O(3) modified by cinchonidine and O-methylcinchonidine. We have shown that the sometimes dramatic changes in enantioselectivity and rate cannot simply be interpreted by protonation of the alkaloid modifier. We propose a new three-step reaction pathway, involving interaction of the carboxylic acid with the reactant and the chiral modifier. The mechanism is supported by IR spectroscopic identification of cyclic TFA-modifier ion pairs. This new approach can rationalise the poorly understood role of acids in the enantioselective hydrogenation of activated ketones over cinchona-modified platinum metals.
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  • English
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https://sonar.ch/global/documents/127929
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