Continuous Flow Processing of Bismuth-Photocatalyzed Atom Transfer Radical Addition Reactions Using an Oscillatory Flow Reactor

Metal oxides represent an abundant and non-toxic class of photocatalysts for organic transformations. However, their use in larger scale processes is complicated by incompatibilities with continuous flow processing – a proven scale-up route for photochemistry. We detail the development of an efficient atom transfer radical addition protocol using a sustainable solvent system (acetone : PEG 400) and a low loading (2 mol%) of Bi2O3, which can be handled in an oscillatory flow reactor. Optimization of the reaction and oscillatory parameters led to high throughput (36 g in 4 h, 89% yield, 599 g L−1 h−1), with a process mass intensity (PMI) of just 8.5. The process also facilitates high recyclability (3 cycles with no loss of yield), and was demonstrated to be applicable to a range of other substrates on multigram scale, in moderate to excellent yields.

Bianchi, P.; Williams, J.; Kappe, C. O. Green Chem., 2021, 23, 2685-2693

https://doi.org/10.1039/D0GC03070H

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Continuous Flow Processing of Bismuth-Photocatalyzed Atom Transfer Radical Addition Reactions Using an Oscillatory Flow Reactor

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