Anodic Alcohol Oxidation in Catalytically Active Suspensions of Carbon Particles and TEMPO‐Modified Polymethacrylates

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Abstract
Homogeneous electrocatalysts (“mediators”) are often used in organic electrosynthesis to overcome electron transfer inhibitions and to control coupled chemical reactions. However, separating the mediators after completed electrolysis poses a challenge that is typically solved by column chromatography. In this context, the polymediator concept was previously developed, allowing for separation of mediator‐modified polymers using scalable size‐exclusive membrane processes. A problem that remained to be solved is the loss of catalytic activity with increasing molecular weight of the polymediator due to curbed mass transport, resulting in prolonged electrolysis durations. In the present report, we describe an approach to overcome this dilemma by suspending conductive carbon particles in the electrolyte. Using the 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO)‐catalyzed alcohol oxidation as a test reaction, the starting material is electrolyzed in a carbon particle suspension in the presence of TEMPO‐modified polymethacrylate (TPMA), leading to a significantly accelerated reaction compared to particle‐free conversion while maintaining high selectivity. In addition to investigating the influence of various parameters such as particle type and loading, substrate scope, scalability, and recyclability were examined, whereby promising results were obtained. Possible explanations for the enhanced performance—such as improved mass transport and mixing effects, as well as the formation of conductive networks—are discussed in detail.
Funding Information
  • Deutsche Forschungsgemeinschaft (FR 3848/2‐2)
  • Deutsche Forschungsgemeinschaft (FR 3848/6‐1)
  • Deutsche Forschungsgemeinschaft (FR 3848/4‐1)
  • National Science Foundation (CHE‐2055689)

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