Unusual enantioselectivities in heterogeneous organocatalyzed reactions: Reversal of direction using proline di- versus tri-peptides in the aldol addition

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Abstract

The heterogeneous asymmetric direct aldol reactions between aldehydes (2-nitrobenzaldehyde, 2-methylpropanal) and ketones (acetone, cyclohexanone) in the presence of polystyrene (PS) resin supported di- and tripeptides were studied under otherwise identical experimental conditions at room temperature in batch reactor. For all three asymmetric aldol reactions reversal of enantiomeric excess was observed on H-Pro-Pro-Glu(OH)-PS catalyst (ee 39-50%) as compared to the H-Pro-Glu(OH)-PS catalyst (ee 52-95%). The determinant role of the conformation of the intermediate adducts held responsible for chiral induction is interpreted by quantum chemical calculations.

Original languageEnglish
Pages (from-to)86-92
Number of pages7
JournalJournal of Molecular Catalysis A: Chemical
Volume382
DOIs
Publication statusPublished - Feb 1 2014

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Keywords

  • Aldol reaction
  • Asymmetric synthesis
  • Heterogeneous catalysis
  • Organocatalysis
  • Peptides

ASJC Scopus subject areas

  • Catalysis
  • Process Chemistry and Technology
  • Physical and Theoretical Chemistry

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