How Lewis Acids Catalyze Diels–Alder Reactions

Pascal Vermeeren, Trevor A. Hamlin, Israel Fernández*, F. Matthias Bickelhaupt

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

The Lewis acid(LA)-catalyzed Diels–Alder reaction between isoprene and methyl acrylate was investigated quantum chemically using a combined density functional theory and coupled-cluster theory approach. Computed activation energies systematically decrease as the strength of the LA increases along the series I2<SnCl4<TiCl4<ZnCl2<BF3<AlCl3. Emerging from our activation strain and Kohn–Sham molecular orbital bonding analysis was an unprecedented finding, namely that the LAs accelerate the Diels–Alder reaction by a diminished Pauli repulsion between the π-electron systems of the diene and dienophile. Our results oppose the widely accepted view that LAs catalyze the Diels–Alder reaction by enhancing the donor–acceptor [HOMOdiene–LUMOdienophile] interaction and constitute a novel physical mechanism for this indispensable textbook organic reaction.

Original languageEnglish
Pages (from-to)6201-6206
Number of pages6
JournalAngewandte Chemie. International Edition
Volume59
Issue number15
Early online date16 Jan 2020
DOIs
Publication statusPublished - 6 Apr 2020

Bibliographical note

German Edition: DOI: 10.1002/ange.201914582

Keywords

  • Activation strain model
  • density functional calculations
  • Diels–Alder reactions
  • Lewis acid catalysis
  • Pauli repulsion

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