Green Chemistry: Electrochemical Organic Transformations via Paired Electrolysis

Abstract

Paired electrolysis is highly valuable from the viewpoint of efficiency as well as atom and energy economies. In order to optimize the latter two for chemical reactions, the development of paired electrochemical processes is necessary. When both of the electrodes in an electrochemical cell (divided and undivided) are applied as working electrodes, and both sides of the processes (oxidation and reduction) yield valuable compounds, this ideal electrolysis phenomena is defined as paired electrosynthesis. This paired electrolysis offers the opportunity to reduce the spent energy and time, when compared with a single electrolysis system that is only used to achieve a product of interest, while ignoring the other side of the electrolysis (anodic or cathodic). In an ideal case, 200% current efficiency could be achieved during paired electrosynthesis using cathodic and anodic processes to provide the same product. Paired electrosynthesis is a highly efficient green process and, therefore, is beneficial for preserving resources and minimizing waste. However, while a paired electrosynthesis is beneficial, both oxidation and reduction processes must be compatible to counter the yield losses and equally ease separation and purification of both sides of the electrode products. Greater efforts are required to perform paired electrosynthesis with a more systematic and rational approach to achieve optimal products under paired conditions. Nevertheless, new computational tools could be applied for assistance in this matter. There is a considerable level of adventure in designing new paired electrosynthetic processes and accompanying opportunities to design innovative and powerful synthetic strategies. Herein, an overview of several examples of paired electrosyntheses and their advantages are summarized that will aid researchers to both develop a greater understanding of this subject and subsequently employ paired electrolysis for green and sustainable synthesis of organic molecules.

Fluorine-modified cobalt electrocatalyst for quinoline hydrogenation with water at room temperature

“…Third, developing a thermodynamically more favorable organic oxidation reaction to replace the low-value and kineticsluggish oxygen evolution reaction (OER) is of great signi cance to enhance the performance of cathodic reactions in an aqueous solution. [52][53][54][55][56] Electrocatalytic hydrogenation of 1a can be accomplished by adopting a divided Co-F||NiSe two-electrode electrolyzer by using the oxidation of 1,6-hexanediamine (4a) to replace OER. Adiponitrile (5a), an important industrial feedstock for nylon production, and 2a with high yields are simultaneously synthesized.…”

Organic synthesis via Kolbe and related non-Kolbe electrolysis: an enabling electro-strategy

“…Easy access to value-added chemicals using modern synthetic tools [89][90][91][92] (such as electrochemistry, photochemistry, flow chemistry, biochemistry, digital chemistry) have been progressing fast due to their environmentally friendly approach with less or no waste / side products, giving a safe and steady route to get desirable products. Asymmetric electrochemical transformations remain highly desired.…”

Renewable Electricity Enables Green Routes to Fine Chemicals and Pharmaceuticals

“…Electrical current could play a role in forming reaction intermediates in such chemical transformations with minimal, or in the absence of, waste production by direct or indirect electrolysis processes using batch and flow technologies. Furthermore, the merging of technologies can accelerate production yields [5–9] . At present, considering ongoing climate challenges, stakeholders related to the production of fine chemicals and pharmaceuticals are enamoured to introduce green and sustainable techniques that conserve energy, generate fewer by‐products, and derive maximum atom economies with low cost.…”

“…Furthermore, the merging of technologies can accelerate production yields. [5][6][7][8][9] At present, considering ongoing climate challenges, stakeholders related to the production of fine chemicals and pharmaceuticals are enamoured to introduce green and sustainable techniques that conserve energy, generate fewer by-products, and derive maximum atom economies with low cost. Carboxyl-, fluorine-, methoxy-, amide-, sulfur-, and nitrogen-containing heterocycles are important in the pharmaceutical industry due to their role in drug discovery.…”