Rate and equilibrium constants for the addition of N-heterocyclic carbenes into benzaldehydes: A remarkable 2-substituent effect

Christopher J. Collett, Richard S. Massey, James E. Taylor, Oliver R. Maguire, Ann Marie C. O'Donoghue, Andrew D. Smith

Research output: Contribution to journalArticlepeer-review

47 Citations (Scopus)

Abstract

Abstract Rate and equilibrium constants for the reaction between N-aryl triazolium N-heterocyclic carbene (NHC) precatalysts and substituted benzaldehyde derivatives to form 3-(hydroxybenzyl)azolium adducts under both catalytic and stoichiometric conditions have been measured. Kinetic analysis and reaction profile fitting of both the forward and reverse reactions, plus onwards reaction to the Breslow intermediate, demonstrate the remarkable effect of the benzaldehyde 2-substituent in these reactions and provide insight into the chemoselectivity of cross-benzoin reactions. It takes 2-: Measurement of rate and equilibrium constants for the reaction between N-aryl triazolium NHC precatalysts and substituted benzaldehydes under catalytic and stoichiometric conditions demonstrate the remarkable kinetic and thermodynamic effect of the benzaldehyde 2-substituent in these reactions, potentially providing insight into the chemoselectivity of cross-benzoin reactions.

Original languageEnglish
Pages (from-to)6887-6892
Number of pages6
JournalAngewandte Chemie - International Edition
Volume54
Issue number23
Early online date23 Apr 2015
DOIs
Publication statusPublished - 1 Jun 2015

Keywords

  • 2-substituent effect
  • kinetics
  • mechanistic studies
  • N-heterocyclic carbenes
  • organocatalysis

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

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