Electrochemical generation and utilisation of Alkoxy Radicals

Elgehani, Albara 2023. Electrochemical generation and utilisation of Alkoxy Radicals. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

This thesis describes investigations performed in the development of novel methods for the generation and utilization of alkoxy radicals via synthetic organic electrochemistry. The work described within is separated into 3 parts. Firstly, work in chapter 2 describes efforts to generate alkoxy radicals anodically from tertiary cycloalkanols. During this investigation a novel method for the generation of alkoxy radicals was developed using proton coupled electron transfer (PCET), to perform the deconstructive functionalisation of tertiary substituted cycloalkanols of various ring sizes that contained electron rich rings to generate a wide range of synthetically useful distally functionalised ketones (>30 examples, up to 97% yield). The investigation and use of inexpensive triaryl amine redox mediators as a means to activate different electron rich rings is discussed through the use of cyclic voltammetry studies. A facile scale up was demonstrated with a simple single pass flow electrochemistry set up using a commercially available ammonite 8 flow reactor. Mechanistic investigations demonstrated the role and importance of the alkoxy radical intermediate and the utility of the ketone products formed was also demonstrated. Next chapter 3 discusses the work following the development of our PCET approach for the generation of alkoxy radicals. Initial focus is placed upon overcoming the limitation of the previous work and looking to expand on the use of mediators in our lab. The chapter investigated the use of Photoelectrochemistry as a means to activate previously inaccessible rings and investigation into different radical traps and the role of radical phylicity. This investigation would ultimately lead to a second publication of deconstructive functionalization of unstrained cycloalkanols via electrochemically generated aromatic radical cations, which, like the alkoxy radical work before, generated synthetically useful distally functionalised ketones although this time by trapping using a variety of nucleophiles (36 examples, up to 72% yield). Finally, chapter 4 follows the investigation into the generation of alkoxy radicals via cathodic reduction. This work involves the synthesis of a number of different redox handles that would act as conduits by which alkoxy radicals could be generated electrochemically directly at the cathode. Extensive cyclic voltammetry studies were used to compare redox handles, which showed some limited success. In an attempt iv to further improve the reaction yields, a range of photochemical mediators were employed with limited results.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Chemistry
Date of First Compliant Deposit:	2 April 2024
Last Modified:	02 Apr 2024 10:12
URI:	https://orca.cardiff.ac.uk/id/eprint/167648

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