Colson, Eloïse (2022). Classical and Quantum Dots Photoredox Catalyzed Synthetic Methods. (Thesis). Universität Bern, Bern
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Abstract
Quantum dots are nanometer-sized semiconductors composed of an inorganic core and surrounded by an organic layer of ligands. Due to their nanometric size, quantum dots exhibit discrete atomic-like states and are able, upon light excitation, to engage in electron transfers with small organic molecules. Their use as photocatalysts in preparative organic synthesis is developing rapidly but is largely limited to net reductive processes. In addition, quantum dots are still far from being adopted as common photocatalysts by organic chemists, despite the current craze for photoredox protocols. As part of a collaboration with a team of physical-chemists from the CEA in Grenoble (France), we had the objective to develop quantum dot photocatalysts (in Grenoble) and to use them for preparative organic chemistry (in Bern). A first phase was devoted to the development of redox neutral photochemical methods using iridium photocatalysis. We investigated boronate complexes as radical precursors by one-electron oxidation and found that alcoholate-substituted boronate complexes where efficient at generating not the corresponding alkoxyl radical, but the phenyl radical. The alcohol substituent was important to reduce the formation of a biphenyl side-product. The utility of the generated phenyl radical was demonstrated by an allylation reaction as well as by its ability to engage in iodine abstraction. No substrate scope was investigated for these transformations and quantum dot photocatalysis was not applied in this case. Next, we turned our intention to alpha-aminoalkyl radicals as key intermediates in a radical [3+3]-annulation reaction leading to biologically relevant tropane and related alkaloid skeletons. We demonstrated that a broad scope of aniline derivatives could be engaged in this transformation. The products are distinct from the Robinson annulated products and functional handles are available for further derivatization. In addition, important milestones towards the total synthesis of (+)- euphococcinine were achieved. After the development of suitable quantum dots in Grenoble, these photocatalysts were used for the radical annulation reaction. Despite limitations observed in the scope for reaction scale exceeding 0.05 mmol, promising results were obtained with N-phenylpyrrolidine on 0.2 mmol scale.
| Item Type: | Thesis |
|---|---|
| Dissertation Type: | Cumulative |
| Date of Defense: | 28 October 2022 |
| Subjects: | 500 Science > 540 Chemistry 500 Science > 570 Life sciences; biology |
| Institute / Center: | 08 Faculty of Science > Department of Chemistry, Biochemistry and Pharmaceutical Sciences (DCBP) |
| Depositing User: | Hammer Igor |
| Date Deposited: | 04 Nov 2024 16:26 |
| Last Modified: | 04 Nov 2024 23:25 |
| URI: | https://boristheses.unibe.ch/id/eprint/5556 |
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