Chakarov, Stefan Ivanov;
(2025)
Generation and Reactivity of Oxygen-Centred Radicals and Hydrogen Atoms in Organic Synthesis.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
This thesis explores the development of novel catalytic strategies to access highly reactive and underexplored radical intermediates. Although each project addresses a distinct synthetic challenge, together they contribute to the broader goal of expanding the toolbox for sustainable radical chemistry. The first part focuses on the development of a strategy for novel titanium-based Nheterocyclic carbene catalysts capable of activating alcohols. Reaction design and conditions optimisation provided preliminary evidence consistent with homolytic C–O bond cleavage in primary alcohol substrates, while indicating that improved conversion and milder conditions will require further ligand optimisation. The second part investigates strategies for generating oxygen-centred radicals aimed at anti-Markovnikov hydroxylation of terminal olefins. Pyridine N-oxides were identified as suitable precursors for radical oxygen-transfer under photoredox conditions, providing a promising approach to direct olefin hydroxylation. Finally, the third project presents a near-UV-initiated methodology for generating a hydrogen radical. As a proof of concept, radical hydrogenation of terminal alkenes and Michael acceptors was achieved and optimised. Mechanistic studies revealed two potential pathways: (i) direct generation and radical addition of the hydrogen atom, and (ii) concerted transfer of a hydrogen radical into the olefinic π -system. Collectively, these studies demonstrate how rational catalyst and reaction design can unlock previously unexplored radical reactivity under synthetically useful conditions.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Generation and Reactivity of Oxygen-Centred Radicals and Hydrogen Atoms in Organic Synthesis |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2025. 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 UCL > Provost and Vice Provost Offices > UCL BEAMS 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 |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10218808 |
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