Batch versus Flow Photochemistry: A Revealing Comparison of Yield and Productivity

TLDR

Flow photochemistry has been reported to be superior to batch photochemistry in recent studies. The authors aimed to determine whether flow truly offers an advantage over batch. They optimized a broad range of synthetic photochemical transformations in both batch and flow reactors, comparing yields and productivities. Yields were essentially identical across all comparisons, productivity varied little between flow and batch when key parameters were matched—single‑layer FEP reactors were 20 % less productive and three‑layer reactors 20 % more productive—while a scale‑up of a potentially explosive [1.1.1] propellane ring‑opening with butane‑2,3‑dione demonstrated flow’s practical utility.

Abstract

Abstract The use of flow photochemistry and its apparent superiority over batch has been reported by a number of groups in recent years. To rigorously determine whether flow does indeed have an advantage over batch, a broad range of synthetic photochemical transformations were optimized in both reactor modes and their yields and productivities compared. Surprisingly, yields were essentially identical in all comparative cases. Even more revealing was the observation that the productivity of flow reactors varied very little to that of their batch counterparts when the key reaction parameters were matched. Those with a single layer of fluorinated ethylene propylene (FEP) had an average productivity 20 % lower than that of batch, whereas three‐layer reactors were 20 % more productive. Finally, the utility of flow chemistry was demonstrated in the scale‐up of the ring‐opening reaction of a potentially explosive [1.1.1] propellane with butane‐2,3‐dione.