A thin-gap cell for selective oxidation of 4-methylanisole to 4-methoxy-benzaldehyde-dimethylacetal

An electrochemical microreactor for organic electrosynthesis has been investigated for the anodic synthesis of 4-methylanisole to 4-methoxy-benzaldehyde-dimethylacetal in methanol solution. Selectivity and conversion in the single-pass thin-gap flow reactor were examined as a function of the composition of the electrolyte solution, the flow rate and the applied current. The experimental results indicate that potassium fluoride currently used for industrial synthesis and providing higher yields than sodium perchlorate, exerts an influence on the reaction mechanism: high KF concentrations facilitate the undesired oxidation of the diacetal. Nevertheless, a feed solution containing 0.1 M anisole in 0.01 M KF can be converted at 90% in the 100 mu m thin-gap cell with acceptable voltages and a measured selectivity of nearly 87%. The selectivity observed substantially higher than that typically observed in conventional electrochemical cells.