Electrocatalysis in iodine-based oxidations

Winterson, Bethan 2023. Electrocatalysis in iodine-based oxidations. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

With the increasing societal pressure on synthetic organic chemistry to develop sustainable approaches, electrochemistry using hypervalent iodine reagents has attracted a great deal of attention. Hypervalent iodine reagents are often used as alternatives to heavy-metal oxidants, thus could reduce the heavy metal contamination of the environment. However, their synthesis from iodine(I) compounds typically requires stoichiometric amounts of chemical oxidants which is a source of waste. The electrochemical synthesis of iodine(III) compounds obviates any demand for chemical oxidants thereby improving the atom economy of the reactions. This work outlines the electrosynthesis and application of hypervalent iodine reagents. (Difluoroiodo)arenes are powerful tools for fluorinations and can be synthesised in a single step using electrochemical methods. In this first part of this thesis, a flow electrochemical method for the synthesis of (difluoroiodo)arenes is disclosed. The use of flow chemistry improves the productivity of the reaction compared to batch techniques. A broad range of hypervalent iodine mediated reactions were achieved in high yields by coupling the electrolysis step with downstream reactions in flow. This method was further developed for the synthesis of chiral (difluoroiodo)arenes. The mediators were applied for the α-fluorination of β-ketoesters, and the products could be obtained with high yields and enantioselectivities (up to 85% yield, 82% ee). Key to the success of this work was the application of the chiral aryl iodides in an incell manner due to the instability of the formed ArIF2’s. Finally, electrochemically generated [di(alkoxy)iodo]arenes are demonstrated for C–N coupling reactions and the synthesis of unsymmetrical diaryl sulfones. The synthetic approach utilises iodine(III) reagents ligated with HFIP in combination with sulfonyl hydrazides and an arene, providing the sulfones via a denitrogenative mechanism. The system operates under ambient temperatures, affording a broad range of products in good to excellent yields.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Chemistry
Date of First Compliant Deposit:	30 April 2024
Last Modified:	30 Apr 2024 15:39
URI:	https://orca.cardiff.ac.uk/id/eprint/168508

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