Similar Publications

Continuous-flow methodologies offer promising avenues for sustainable processing due to their precise process control, scalability, and efficient heat and mass transfer. The small dimensions of continuous-flow reactors render them highly suitable for light-assisted reactions, as can be encountered in carbon dioxide hydrogenations. In this study, we present a reactor system emphasizing reproducibility, modularity, and automation, facilitating streamlined screening of conditions and catalysts for these processes.

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Development of a microfluidic photochemical flow reactor concept by rapid prototyping.

Front Chem

August 2023

Laboratory of Equipment Design, Department of Biochemical and Chemical Engineering, TU Dortmund University, Dortmund, Germany.

The transfer from batch to flow chemistry is often based on commercial microfluidic equipment, such as costly complete reactor systems, which cannot be easily tailored to specific requirements of technologies such as DNA-encoded library technology (DELT), in particular for increasingly important photochemical reactions. Customized photoreactor concepts using rapid prototyping technology offer a modular, flexible, and affordable design that allows for adaptation to various applications. In order to validate the prototype reactors, a photochemical pinacol coupling reaction at 368 nm was conducted to demonstrate the transfer from batch to flow chemistry.

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Quaternary carbons are ubiquitous in bioactive molecules; however, synthetic methods for the construction of this motif remain underdeveloped. Here, we report the synthesis of quaternary carbons from tertiary alcohols, a class of structurally diverse, bench-stable feedstocks, via the merger of photoredox catalysis and iron-mediated S2 bond formation. This alcohol-bromide cross-coupling is enabled by a novel halogen-atom transfer (XAT) reagent, which is the first reductively activated XAT reagent to be reported.

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The upscaling of biphasic photochemical reactions is challenging because of the inherent constraints of liquid-gas mixing and light penetration. Using semi-permeable coaxial flow chemistry within a modular photoreactor, the photooxidation of the platform chemical furfural was scaled up to produce routinely 29 gram per day of biobased building block hydroxybutenolide, a precursor to acrylate alternatives.

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HARC as an open-shell strategy to bypass oxidative addition in Ullmann-Goldberg couplings.

Proc Natl Acad Sci U S A

September 2020

Merck Center for Catalysis, Department of Chemistry, Princeton University, Princeton, NJ 08544

The copper-catalyzed arylation of unsaturated nitrogen heterocycles, known as the Ullmann-Goldberg coupling, is a valuable transformation for medicinal chemists, providing a modular disconnection for the rapid diversification of heteroaromatic cores. The utility of the coupling, however, has established limitations arising from a high-barrier copper oxidative addition step, which often necessitates the use of electron-rich ligands, elevated temperatures, and/or activated aryl electrophiles. Herein, we present an alternative aryl halide activation strategy, in which the critical oxidative addition (OA) mechanism has been replaced by a halogen abstraction-radical capture (HARC) sequence that allows the generation of the same Cu(III)-aryl intermediate albeit via a photoredox pathway.

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