Design of Experiments-Based Optimization of an Electrochemical Decarboxylative Alkylation using a Spinning Cylinder Electrode Reactor

A design of experiments model has been developed to optimize an electrochemical protocol for the decarboxylative N-alkylation of pyrazole in a spinning cylinder electrode reactor. The electrochemical reaction requires the incorporation of molecular sieves as an additive to ensure the absence of moisture and prevent potential electrode corrosion issues. The spinning cylinder electrode reactor proved to be an idea platform to scale up this transformation, involving a suspension of solid particles, to multigram scales. The reaction model, which showed an excellent fitting with the experimental data, provided insights on the effect of important electrolysis parameters unique to this reactor design, such as the electrode spinning speed, on the reaction conversion and selectivity. Furthermore, the design of experiments also supplied optimal electrolysis parameters for this complex multivariable reaction system, resulting in full conversion of the substrate and excellent selectivity for a 600 mL volume reaction in recirculation flow mode, with 94% isolated yield for the target N-alkylated product.