Utilising Non-Covalent Interactions in Developing Enantioselective Radical Transformations

This thesis details the development of catalytic, enantioselective strategies for radical reactions, utilising non-covalent interactions to control the asymmetry of these processes. The first research chapter describes the use of chiral phosphoric acids to control the enantioselectivity in the reactions of α-amino radicals. Firstly, a Giese reaction with α,β-unsaturated carbonyls is reported. This was found to be successful for a range of substrates, with the catalyst being able to exert control over the stereocentres originating from both the amine nucleophile and the acrylamide acceptor. Secondly, a reaction with polarity-mismatched acceptors, in the form of electron-rich enamides, is disclosed. While high enantioselectivities were achieved in some cases, the reaction was found to be effective only for a limited range of substrates. Thirdly, the Minisci-type addition of cyclic α-amino radicals into heteroarenes is detailed, including substrate design and limitations of the process. The second research chapter details preliminary studies into developing asymmetric nickel-catalysed functionalisations of α-amino radicals, using two different approaches. Initially, investigations were performed to determine whether chiral phosphoric acids, bound to the substrate via hydrogen bonding, could induce asymmetry. The subsequent approach relied on using an anionic ligand, ion-paired to a chiral cation derived from cinchona alkaloids, to create a chiral environment around the metal centre. The challenges encountered for both approaches are discussed. The third research chapter describes the incipient phase of a project based on the use of cinchona alkaloids-derived catalysts to perform enantioselective and desymmetrising hydrogen atom transfer from vicinal diols. The α-hydroxy radicals generated in the process were utilised in Giese additions and stereochemical isomerisation reactions, with high levels of enantioselectivity.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2023

Author dc:creator

• Bacos, Paul David

Advisor dc:contributor.advisor

• Phipps, Robert

• Organic Chemistry

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/fd91ee7c-df4e-4c6a-86cb-02ddda4daa0c/download
• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.106630

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/365260