Abstract

Flow Electrosynthesis and Development of Electrochemical Flow Cells for Scale up of Laboratory Synthesis

Richard C D Brown, Professor, University of Southampton

Electrosynthesis is a potentially powerful tool for chemists, enabling many types of reaction, and in some cases without reagents or catalysts. Despite the clear attractions of electrosynthesis, it remains somewhat underutilised in academic and industrial labs. Although flow electrosynthesis has been practiced for many years for selected applications, recently, microfluidic electrochemical flow reactors have emerged as a convenient platform for laboratory electrosynthesis.

Despite a number of interesting electrosyntheses in microfluidic devices, much of the literature reports productivity rates of mg h^–1, which limits the use of the technology. We recently demonstrated that with careful design of the flow path, flow rates could be significantly increased, leading to productivities of multiple grams per hour without affecting conversion and yield in devices with relatively small footprint.^1,2 High productivity rates have been demonstrated in multiple reactions such as anodic methoxylation of N-formylpyrrolidine,² and N-heterocyclic carbene (NHC) mediated oxidative esterification and amidation of aldehydes.^3,4

To extend the productivity rate available in laboratory flow electrosynthesis reactors we developed a flow cell possessing an enlarged electrode area while retaining a micron-scale interelectrode gap. Using the anodic methoxylation as a test reaction, the “Ammonite” scale up flow cell was shown to be capable of producing methoxylated product at rates exceeding 20 g h^–1 with high conversion and selectivity.⁵ The reactor has a small footprint, easily fitting within a standard fumehood, allowing scale up of flow