Merging Enabling Technologies and Photochemical Reactions for the Advanced Synthesis of Chemical Building Blocks

Le résumé fourni par la source

Enabling technologies such as monochromatic LEDs, flow chemistry, and algorithmic tools for experimental design have undergone rapid development in recent years. These innovations have addressed many past limitations in chemical processes, with their advantages now well documented. Photochemical transformations in particular have benefited substantially from the integration of flow technology, wavelength-specific LEDs, and statistically guided optimisation strategies. This thesis demonstrates the application of these enabling technologies to advance photochemical transformations. Firstly, this thesis addresses prior limitations in the use of aryl aldehydes in tetrabutylammonium decatungstate (TBADT) HAT catalysis, as described in Chapter 2. The work demonstrates the process-intensification capabilities of flow technology and high-power LEDs in photocatalytic reactions, showing how these tools can be exploited to minimise unwanted side reactions. By employing historically challenging substrates for photochemical transformations, an efficient flow system was developed to access γ-ketonitriles through C–C bond formation. Furthermore, it was observed that certain high-throughput processes required an additional quench step, a phenomenon not apparent at longer reaction times. Secondly, Chapter 3 explores the development of novel substituted alkyne sulfones as radical leaving groups, or radicofugal groups. This study highlights the role of substitution in sulfonated alkynes for their effective use as radicofugal groups. It demonstrates how these groups can preserve π-bonds in Giese-type additions, enabling the efficient formation of ynones. In addition, the methodology incorporates the previously challenging aryl aldehyde substrates and provides a Pd-free alternative to the acyl Sonogashira reaction, offering distinct chemoselectivity advantages. Finally, Chapter 4 investigates the use of novel low-wavelength monochromatic LEDs. A custom design-of-experiments model, generated with the aid of artificial-intelligence algorithms, was combined with 3D-printed reactors in this work. The developed systems were applied to overcome prior limitations in the photoisomerisation of isoxazoles to ketenimines, demonstrating clear advantages in throughput and scalability. Moreover, targeted substrate irradiation was shown to enhance the chemoselectivity of photochemical transformations. In addition, the study evaluated the cost-effectiveness and sustainability of replacing traditional Hg-based light sources with monochromatic LEDs by assessing their external quantum yield.

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