Thesis

Transfer of alkyl groups in novel amidine dications and other superelectrophiles

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Awarding institution
  • University of Strathclyde
Date of award
  • 2014
Thesis identifier
  • T13703
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Abstract
  • This thesis explores the synthesis and the reactivity of novel amidine salts resulting from various N-methylformamides and N-methylbenzamides I and II. Treatment of these compounds with triflic anhydride under mild conditions led to extremely facile alkyl transfer from an sp3-hybridised nitrogen centre to very weakly nucleophilic triflate anions. For the reaction pathway of substrates III and VII, in silico studies propose an equilibrium between the more stable tetrahedral triflate intermediate IV and the superelectrophilic amidinium disalt V from which dealkylation takes place. The unprecedented α-aminotriflate IV was characterised by lowtemperature 1H- and 13C-NMR spectra and the rate of alkyl transfer for substrates III and VII determined. Unlike formamides III and VII, in silico and low-temperature NMR studies of the reaction of benzamide IX with triflic anhydride showed amidinium disalt intermediate XI to be more stable than tetrahedral triflate X due to steric factors. Due to the enhanced alkyl transfer activity of amidinium disalt XV derived from benzene-based formamide XIII, low temperature NMR studies did not allow for observation of intermediates XIV or XV. However, the benzamide analogue XVII with phenyl residues on the tertiary amine allowed for isolation and characterisation of amidinium dication XVIII. The reaction protocol was subsequently applied to derivatives of 2-(alkylthio)phenylformamides XIX which underwent alkyl transfer to yield benzothiazolium salt XXII. Interestingly, benzamide analogue XXIII afforded benzthiazolium disalt XXIV upon addition of triflic anhydride, but gradually dephenylated to monocation XXV.
Resource Type
DOI
Date Created
  • 2014
Former identifier
  • 1031359

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