A highly modular electrochemical flow cell and its application in electroorganic synthesis is reported. This innovative setup facilitates many aspects: an easy adjustment of electrode distance, quick exchange of electrode material, and the possibility to easily switch between a divided or undivided cell. However, the major benefit of the cell is the exact thermal positioning of the electrode material into a Teflon piece. Thereby, the application of expensive and nonmachinable electrode materials like boron-doped diamond or glassy carbon can easily be realized in flow cells. By this geometry, the maximum surface of such valuable electrode materials is exploited. The cell size can compete with classical preparative approaches in terms of performance and productivity. The optimization of reaction parameters and an easy up-scaling to larger flow cells is possible. By using this cell, the starting material can be saved in the development of the electroorganic transformations. To demonstrate the utility of this particular cell, two transformations of important building blocks for the fine chemical and pharmaceutical industry were established including an efficient and simple workup protocol.

Lignin represents the largest renewable resource of aromatic moieties on earth and harbors a huge potential as a sustainable feedstock for the synthesis of biobased aromatic fine chemicals. Due to the complex, heterogeneous, and robust chemical structure of the biopolymer, the valorization is associated with significant challenges. Unfortunately, technical lignins, which are a large side stream of the pulp and paper industries, are mainly thermally exploited. In this study, technical Kraft lignin was selectively electrochemically depolymerized to the aroma chemical vanillin. Using electricity, toxic and/or expensive oxidizers could be replaced. The electrodegradation of Kraft lignin was performed at 160 °C in a simple undivided high-temperature electrolysis cell and studied in respect to several reaction parameters. At optimized electrolytic conditions vanillin could be obtained in high selectivity with 67% efficiency compared to the common nitrobenzene oxidation. Additionally, the established high-temperature electrolysis indicated a reliable process and could be easily adapted to a variety of different Kraft lignins.

The successive scale-up of electrochemical reactions is crucial with regard to the implementation of technical electro-organic syntheses. Therefore, we developed a scalable modular parallel-plate electrochemical flow cell. One distinctive feature of this flow cell is that the temperature of the electrodes can be easily controlled from the back side via an external cooling circuit, enabling high reproducibility of electrochemical conversions. Because the gap between the electrodes is kept narrow, small amounts or no supporting electrolyte is required. The practicability and performance of the novel flow cell were validated by three different anodic phenol−phenol cross-couplings as test reactions.

Limited fossil resources require innovative monomers and polymers derived from renewable feedstocks such as plant biomass.