Abstract
Aldehydes and olefins are low-cost chemical feedstocks that can offer facile access to valuable alcohol products via reductive cross-couplings. This thesis outlines two new photochemical strategies which achieved challenging reductive aldehyde-olefin couplings under mild conditions.Firstly, a sulfoxylate-mediated and photoredox-catalysed protocol leveraging ketyl radical anions was described. Conventional strategies for accessing ketyl radicals from carbonyls are centred on single-electron reduction methods. However, this pathway is challenging due to the large negative reduction potentials of aldehydes. In this protocol, the ketyl intermediates were generated from the redox-active aldehyde derivatives, α-hydroxy sulfinates, through single-electron oxidation. These α-hydroxy sulfinates were formed in situ through the nucleophilic addition of sulfoxylates to aldehydes and could afford ketyl intermediates through oxidative desulfination, thus successfully avoiding the challenging single-electron reduction pathway.
Secondly, a Hantzsch ester-mediated and light-enabled procedure was developed. This new strategy achieved the challenging photoinduced intermolecular couplings of unactivated aliphatic aldehydes and electron-deficient olefins. Importantly, the Hantzsch ester was leveraged as a direct photoreductant instead of a reductive quencher for photoredox catalysis. The key to success of our protocol was the employment of H2O as a protic additive, which allowed the desired cross-coupling reaction whilst decelerating the undesired olefin hydrodimerization side reaction. Instead of ketyl radical anions, mechanistic studies supported olefin radical anions as the key reactive intermediates leading to carbon-carbon bond formation.
| Date of Award | 30 Sept 2025 |
|---|---|
| Original language | English |
| Awarding Institution |
|
| Supervisor | Adam Noble (Supervisor) & Alastair J J Lennox (Supervisor) |
Cite this
- Standard