Entropy-Controlled and Enantiodivergent Lewis Acid Catalysis in Water

Karolina Aplander, U. Marcus Lindstrom, Johan Wennerberg

Research output: Contribution to journalArticlepeer-review

4 Citations (SciVal)

Abstract

Developing new and useful methods in asymmetric catalysis is of continuous importance. A current challenge is to address the imperatives of green chemistry, such that processes maximize resource-efficiency and minimize the generation of waste. To this end, this article discloses the potential of alpha-amino acids in the development of entropy-controlled and enantiodivergent Lewis acid catalysis. In an ytterbium-catalyzed aqueous Michael addition reaction, natural alpha-amino acids induced not only a large rate acceleration, but also an unusual and remarkable reversed temperature effect on enantioselectivity. As demonstrated with 17 alpha-amino acids, the enantioselectivity of the reaction can be significantly altered, and even reversed, simply by modifying the reaction temperature. After determining differential thermodynamic activation parameters, it was revealed that an unusually large entropy contribution was responsible for the observed effects. By further correlation to the influence of the aqueous medium, we put forward the concept of stereospecific aqueous solvation (SAS), which describes the bearing of aqueous solvation on the equilibrium of diastereomeric transition states, and thus on the R/S ratio of the product.
Original languageEnglish
Pages (from-to)848-856
JournalSynthesis
Volume44
Issue number6
DOIs
Publication statusPublished - 2012

Bibliographical note

The information about affiliations in this record was updated in December 2015.
The record was previously connected to the following departments: Organic chemistry (S/LTH) (011001240)

Subject classification (UKÄ)

  • Organic Chemistry

Keywords

  • water
  • Michael reaction
  • Lewis acid
  • enantioselective
  • catalysis

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