Cinchona methyl ethers as modifiers in the enantioselective hydrogenation of (E)-2,3-diphenylpropenoic acids over Pd catalyst

György Szllsi, Beáta Hermán, F. Fülöp, M. Bartók

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

The enantioselective hydrogenation of (E)-2,3-diphenylpropenoic acids over Pd/Al2O3 modified by (R)C8(S)C9 cinchona ethers resulted in the inversion of the sense of the enantioselectivity. To find the explanation of the phenomenon, the interaction of acids bearing different substituents with cinchona alkaloids was studied in solution by NMR spectroscopy and experiments using mixtures of modifiers were carried out. The prominent non-linear behaviour obtained revealed the altered adsorption of the cinchona methyl ethers when compared with the parent alkaloids. The investigations indicated that the interaction of the ether derivatives with the unsaturated acids is more flexible and the presence of the methyl group reshapes the chiral surface sites. The combination of these effects complemented by the bulkiness of the diaryl substituted acrylic acids may lead to the inversion of the docking preference of the substrates in the altered chiral pocket of the adsorbed modifier and consequently results in decrease in the enantioselectivity or even in the inversion of its sense. Novel evidence on the ligand-accelerated mechanism in the enantioselective hydrogenation of (E)-2,3-diphenylpropenoic acids over cinchona alkaloid-modified Pd in the presence of benzylamine was also presented.

Original languageEnglish
Pages (from-to)259-267
Number of pages9
JournalJournal of Catalysis
Volume276
Issue number2
DOIs
Publication statusPublished - Dec 15 2010

Fingerprint

Cinchona
Methyl Ethers
Hydrogenation
alkaloids
hydrogenation
Ethers
ethers
Cinchona Alkaloids
catalysts
acids
Catalysts
Acids
Enantioselectivity
inversions
Bearings (structural)
acrylic acid
Alkaloids
Ether
Nuclear magnetic resonance spectroscopy
Acrylics

Keywords

  • (E)-2,3-Diphenylpropenoic acids
  • Cinchona alkaloids
  • Cinchona methyl ethers
  • Enantioselective
  • Hydrogenation
  • Inversion
  • Non-linear effect
  • Palladium

ASJC Scopus subject areas

  • Catalysis
  • Physical and Theoretical Chemistry

Cite this

Cinchona methyl ethers as modifiers in the enantioselective hydrogenation of (E)-2,3-diphenylpropenoic acids over Pd catalyst. / Szllsi, György; Hermán, Beáta; Fülöp, F.; Bartók, M.

In: Journal of Catalysis, Vol. 276, No. 2, 15.12.2010, p. 259-267.

Research output: Contribution to journalArticle

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