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Electrochemical Reduction of Trifluoroacetylpyridinium Salts for the Oxytrifluoromethylation of Styrenes

Wilson, Isobel; (2022) Electrochemical Reduction of Trifluoroacetylpyridinium Salts for the Oxytrifluoromethylation of Styrenes. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

New trifluoromethylation reactions are constantly being developed to keep up with the demand for fluorinated pharmaceuticals and agrochemicals. This PhD project was focused on developing an electrosynthetic trifluoromethylation reaction from cheap and readily available starting materials. The reasons for this were two-fold. One was to improve upon the current, traditional methods for trifluoromethylation that use harsh reaction conditions and toxic starting materials. The other was to demonstrate the ease and utility of electrosynthesis to the wider organic community. We focused our attention on using trifluoroacetylpyridinium salts as a source for the trifluoromethyl radicals, which we attempted to synthesise from trifluoroacetic anhydride and pyridine. Cyclic voltammetry showed that these salts underwent a single reduction process within the solvent window, making them good candidates for electrosynthesis. It was also demonstrated that upon reduction the trifluoroacetylpyridinium salts with electron withdrawing substituents on the pyridinium ring formed films on carbon-based electrodes. The films were studied to gain an insight into the fate of the radicals produced upon electron transfer with the trifluoroacetylpyridinium salts. Investigations involving x-ray photoelectron spectroscopy and redox probes revealed that the thickness and porosity of the films were dependent on the substituents on the trifluoroacetylpyridinium ring. This demonstrated a new method for attaching pyridine to an electrode. Once a detailed understanding of the electrochemical behaviour of the trifluoroacetylpyridinium salts had been established they were used for the successful electrosynthetic oxytrifluoromethylation of styrenes to afford trifluorophenylpropanone derivatives.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Electrochemical Reduction of Trifluoroacetylpyridinium Salts for the Oxytrifluoromethylation of Styrenes
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Copyright © The Author 2022. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author's request.
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL
URI: https://discovery.ucl.ac.uk/id/eprint/10143938
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