An electrochemical
approach toward rearrangement of O-aryl thiocarbamates
to the corresponding S-aryl
thiocarbamates is presented. The protocol requires only catalytic
amounts of electric charge and allows for operation at room temperature.
The electrolysis can be carried out with the simplest equipment, i.e.,
under galvanostatic conditions in an undivided cell. Furthermore,
it is demonstrated that when the electrolysis is performed in a microflow
reactor, almost quantitative yields can be achieved without using
supporting electrolyte.
Homogeneous catalysts (“mediators”) are useful for tuning selectivity in organic electrosynthesis. However, they can have a negative impact on the overall mass and energy balance if used only once or recycled inefficiently. In a previous work, we introduced the polymediator concept, in which soluble redox‐active polymers catalyze the electrochemical reaction, allowing for recovery by dialysis or pressure‐driven membrane filtration. Using anodic alcohol oxidation as a test case, it was shown that TEMPO‐modified polymethacrylates (TPMA) can serve as efficient and reusable mediators. In the present study, the properties of a TPMA sample with well‐defined molecular weight distribution were studied using cyclic voltammetry and compared to low‐molecular TEMPO species. The non‐catalytic profiles of TPMA are shaped by diffusive and adsorptive processes, whereby the latter only become pronounced at low mediator concentrations and high scan rates. Electrocatalytic studies suggest that under the applied conditions, TPMA‐catalyzed alcohol oxidation is a predominantly homogeneous process. The homogeneous kinetics are determined rather by the mediator potential than by steric influences of the polymer backbone.
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