Photon Equivalents as a Parameter for Scaling Photoredox Reactions in Flow: Translation of Photocatalytic C−N Cross‐Coupling from Lab Scale to Multikilogram Scale

• Emily B. Corcoran^*a
• Jonathan P. McMullen^*b
• François Lévesque^b
• Michael K. Wismer^c
• John R. Naber^b

• ^aProcess Research & Development, Merck & Co., Inc., Boston, MA 02115 (USA)
• ^bProcess Research & Development, Merck & Co., Inc., Rahway, NJ 07065 (USA)
• ^cScientific Engineering & Design, Merck & Co., Inc., Kenilworth, NJ 07033 (USA)

With the development of new photocatalytic methods over recent decades, the translation of these chemical reactions to industrial production scales using continuous flow reactors has become a topic of increasing interest.  In this context, we describe our studies toward elucidating an empirically‐derived parameter for scaling photocatalytic reactions in flow.  By evaluating the performance of a photocatalytic C‐N cross‐coupling across multiple reactor sizes and geometries, it was demonstrated that expressing product yield as a function of the absorbed photon equivalents provided a predictive, empirical scaling parameter.  Through the use of this scaling factor and characterization of the photonic flux within each reactor, the cross‐coupling was scaled successfully from milligram‐scale in batch to a multi‐kilogram reaction in flow.

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