title: Rate and Equilibrium Constants for the Addition of N-Heterocyclic Carbenes into Benzaldehydes: A Remarkable 2-Substituent Effect.
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.
authors.affiliation: EaStCHEM, School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9ST (UK) http://ch-www.st-andrews.ac.uk/staff/ads/group/
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Collett
authors.affiliation: Department of Chemistry, Durham University, South Road, Durham, DH1 3LE (UK).
authors.forename: Richard S
authors.initials: RS
authors.lastname: Massey
authors.affiliation: EaStCHEM, School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9ST (UK) http://ch-www.st-andrews.ac.uk/staff/ads/group/
authors.forename: James E
authors.initials: JE
authors.lastname: Taylor
authors.affiliation: Department of Chemistry, Durham University, South Road, Durham, DH1 3LE (UK).
authors.forename: Oliver R
authors.initials: OR
authors.lastname: Maguire
authors.affiliation: Department of Chemistry, Durham University, South Road, Durham, DH1 3LE (UK).
authors.forename: AnnMarie C
authors.initials: AC
authors.lastname: O'Donoghue
authors.affiliation: EaStCHEM, School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9ST (UK) http://ch-www.st-andrews.ac.uk/staff/ads/group/
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Smith
keywords: N‐heterocyclische Carbene; Organokatalyse; Reaktionskinetik; Reaktionsmechanismen; Substituenteneffekte