Next Generation Photocatalysts for C-H Functionalisation

Lead Research Organisation: University of Nottingham
Department Name: Sch of Chemistry

Abstract

The fundamental goal of this collaborative research project is the development of synthetic methodologies that will allow for the efficient construction of medicinally relevant compounds from simple, readily available starting materials. In this context, the project involves the design and synthesis of novel photocatalysts that can be exploited in synthetic organic reactions. Harnessing light to promote reactivity can be viewed as a more sustainable and economic energy source when compared to conventional methods such as heat and can be used to overcome significant reaction barriers. The most used catalysts in organic photoredox chemistry involve transition-metal complexes comprised of iridium, rhodium, or ruthenium. However, these platinum-group metals are rare, expensive, and usually require pre-functionalised starting materials for the reactions to proceed. In recent years, the development of catalysts that avoid these metals have shown promise in this field. However, these catalysts have limitations including low selectivity and the requirement of high energy UV-light. Furthermore, the reactions developed using these catalysts can be low yielding, be limited in scope and display competitive product decomposition. Crucial to progressing in this area is the development of novel visible light responsive photocatalysts that can be modified to (i) enhance the catalytic efficiency, (ii) exhibit additional functionality - that can be used to facilitate catalyst isolation and/or recycling, and (iii) increase the reaction rates and yield. This has sparked the drive towards more sustainable, tuneable, and selective visible-light active photocatalysts that can be used in synthetic organic reactions.

In terms of organic reaction types, particular attention will be focused on photocatalytic C-H functionalisation for this project. Couplings through C-H bond functionalisation involves the use of simple substrates that are directly converted into more complex molecules, without the need of a previous functionalisation, thus considerably reducing waste generation and the number of synthetic steps required. By combining C-H functionalisation and photoredox catalysis, established synthetic methodology could be applied and incorporated into drug discovery, as part of structure-activity relationship (SAR) exploration and late-stage functionalisation.

Proposed solution and methodology

The successful design and synthesis of a variety of photoactive catalysts forms the basis of this project. The type of catalyst we endeavour to synthesise consists of a core structure functionalised with a variety of organic ligands. By careful design, we aim to investigate the effect of different ligands on the photocatalytic performance of the catalyst, taking into consideration the effects on selectivity, yield, catalytic recycling, and efficiency of the reactions conducted. After the demonstration of the catalytic performance of the photocatalysts and insight is gained into the chemical reactivity and applicability of the catalysts, the next aim of the project involves the development of novel methodology exploiting the catalysts to their full potential. The successful completion of these aims will firstly advance existing reactions that have limitations inherent with the specific catalysts used previously, and secondly, will provide access to currently unknown or inaccessible reaction routes, allowing simple organic substrates to be converted into complex structures, under mild and efficient reaction conditions.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/S022236/1 01/10/2019 31/03/2028
2284947 Studentship EP/S022236/1 01/10/2019 30/09/2023 Nicole Tsang