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Karl Anker Jørgensen

Isotope Effects Reveal an Alternative Mechanism for "iminium-Ion" Catalysis

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  • Joseph A. Izzo, Department of Chemistry, Binghamton University, Binghamton, New York
  • ,
  • Pernille H. Poulsen
  • ,
  • Jeremy A. Intrator, Department of Chemistry, Binghamton University, Binghamton, New York
  • ,
  • Karl Anker Jørgensen
  • Mathew J. Vetticatt, Department of Chemistry, Binghamton University, Binghamton, New York

A novel mechanism for the epoxidation of enals with hydrogen peroxide catalyzed by diarylprolinol silyl ether supported by experimental 13C kinetic isotope effects (KIEs) and density functional theory calculations is presented. Normal 13C KIEs, measured on both the carbonyl- and β-carbon atoms of the enal, suggest participation of both carbon atoms in the rate-determining step. Calculations show that the widely accepted iminium-ion mechanism does not account for this experimental observation. A syn-SN2′ substitution mechanism, which avoids formation of a discrete iminium-ion intermediate, emerges as the most likely mechanism based on agreement between experimental and predicted KIEs.

Original languageEnglish
JournalJournal of the American Chemical Society
Volume140
Issue27
Pages (from-to)8396-8400
Number of pages5
ISSN0002-7863
DOIs
Publication statusPublished - 11 Jul 2018

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