Selective and scalable electrosynthesis of 2H-2-(aryl)-benzo[d]-1,2,3-triazoles and their N-oxides by using leaded bronze cathodes

Electrosynthesis of 2H-2-(aryl)benzo[d]-1,2,3-triazoles and their N-oxides from 2-nitroazobenzene derivatives is reported. The electrolysis is conducted in a very simple undivided cell under constant current conditions with a leaded bronze cathode and a glassy carbon anode. The product distribution between 2H-2-(aryl)benzo[d]-1,2,3-triazoles and their N-oxides can be guided by simply controlling the current density and the amount of the charge applied. The reaction tolerates several sensitive functional groups in reductive electrochemistry. The usefulness and the applicability of the synthetic method is demonstrated by a formal synthesis of an antiviral compound

Para-fluorination of anilides using electrochemically generated hypervalent iodoarenes

The para-selective fluorination reaction of anilides using electrochemically generated hypervalent ArIF2 is reported, with Et3N ⋅ 5HF serving as fluoride source and as supporting electrolyte. This electrochemical reaction is characterized by a simple set-up, easy scalability and affords a broad variety of fluorinated anilides from easily accessible anilides in good yields up to 86 %

Reproducibility in electroorganic synthesis : myths and misunderstandings

The use of electric current as a traceless activator and reagent is experiencing a renaissance. This sustainable synthetic method is evolving into a hot topic in contemporary organic chemistry. Since researchers with various scientific backgrounds are entering this interdisciplinary field, different parameters and methods are reported to describe the experiments. The variation in the reported parameters can lead to problems with the reproducibility of the reported electroorganic syntheses. As an example, parameters such as current density or electrode distance are in some cases more significant than often anticipated. This Minireview provides guidelines on reporting electrosynthetic data and dispels myths about this technique, thereby streamlining the experimental parameters to facilitate reproducibility

Azolylborates for Electrochemical Double Layer Capacitor Electrolytes

Asymmetric tetraalkylammonium salts of azolylborates were synthesized and studied with respect to their suitability as supporting electrolytes in electrochemical double layer capacitors. In contrast to current conducting salts used in this device, azolylborates exhibit an excellent stability towards thermal load and moisture. In addition to good conductivity and stability towards cathodic reduction we found certain limitations when more positive potentials were applie

Degradation of lignosulfonate to vanillic acid using ferrate

A new method is presented using electrochemically generated ferrate to degrade the technically relevant bio-based side-stream products, lignin and lignosulfonate. An exclusive degradation to vanillic acid is found, which was previously a reported by-product. As a natural resource, lignin can be utilized to substitute fossil-based chemicals in the industry to reduce greenhouse gas emissions and positively impact climate change. Ferrate is generated from grey cast iron sacrificial anodes in 40 wt% NaOH with a current efficiency of over 22% at a current density of up to 100 mA cm−2. Vanillic acid is obtained as the sole product after optimizing the reaction parameters, temperature, time, and ferrate concentration for the lignosulfonate degradation via the design of experiments. As a result, yields of 7.2 wt% of the flavoring agent and antioxidant vanillic acid are achieved. The presented two-step degradation provides an inexpensive path for the production of vanillic acid on a laboratory scale from a highly abundant bio-based side-stream

The “green” electrochemical synthesis of periodate

High-grade periodate is relatively expensive, but is required for many sensitive applications such as the synthesis of active pharmaceutical ingredients. These high costs originate from using lead dioxide anodes in contemporary electrochemical methods and from expensive starting materials. A direct and cost-efficient electrochemical synthesis of periodate from iodide, which is less costly and relies on a readily available starting material, is reported. The oxidation is conducted at boron-doped diamond anodes, which are durable, metal-free, and nontoxic. The avoidance of lead dioxide ultimately lowers the cost of purification and quality assurance. The electrolytic process was optimized by statistical methods and was scaled up in an electrolysis flow cell that enhanced the space–time yields by a cyclization protocol. An LC-PDA analytical protocol was established enabling simple quantification of iodide, iodate, and periodate simultaneously with remarkable precision

Electrosynthetic screening and modern optimization strategies for electrosynthesis of highly value-added products

Unlike common analytical techniques such as cyclic voltammetry, statistics-based optimization tools are not yet often in the toolbox of preparative organic electrochemists. In general, experimental effort is not optimally utilized because the selection of experimental conditions is based on the one-variable-at-a-time principle. We will summarize statistically motivated optimization approaches already used in the context of electroorganic synthesis. We discuss the central ideas of these optimization methods which originate from other fields of chemistry in relation to electrosynthetic applications

Dehydrogenative electrochemical synthesis of N-aryl-3,4-dihydroquinolin-2-ones by iodine(III)-mediated coupling reaction

Electrochemically generated hypervalent iodine(III) species are powerful reagents for oxidative C-N coupling reactions, providing access to valuable N-heterocycles. A new electrocatalytic hypervalent iodine(III)-mediated in-cell synthesis of 1H-N-aryl-3,4-dihydroquinolin-2-ones by dehydrogenative C-N bond formation is presented. Catalytic amounts of the redox mediator, a low supporting electrolyte concentration and recycling of the solvent used make this method a sustainable alternative to electrochemical ex-cell or conventional approaches. Furthermore, inexpensive, readily available electrode materials and a simple galvanostatic set-up are applied. The broad functional group tolerance could be demonstrated by synthesizing 23 examples in yields up to 96%, with one reaction being performed on a 10-fold higher scale. Based on the obtained results a sound reaction mechanism could be proposed

Challenges in the electrochemical synthesis of Si2Cl6 starting from tetrachlorosilane and trichlorosilane

The strongly increasing demand for nano- and microelectronics calls for new and environmentally benign reaction pathways for the preparation of one of the most important substrates in the production of semiconductor materials: Si2Cl6. We present a comprehensive study of the opportunities and challenges for the selective electrochemical formation of higher halo-functionalized silanes to Si2Cl6 achieved by cyclic voltammetry measurements and electrochemical synthesis. Cathodic dehalo-dimerization reaction of SiCl4 and the approach to halogen exchange for better substrate reduction are envisioned. An anodic halide-free dimerization pathway by dehydrogenation of HSiCl3 is investigated, including Lewis acid activation of the Si−H bond. In addition, tertiary amine-driven, Benkeser-like in-situ formation of a SiCl3− anion was tested as well. The target molecule Si2Cl6 is strongly promoted to direct electro-conversions making the anodic and cathodic electrosynthesis very challenging

LABS: Laboratory automation and batch scheduling : a modular open source Python program for the control of automated electrochemical synthesis with a web interface

With LABS, an open source Python-based lab software is established that enables users to orchestrate automated synthesis setups. The software consists of a user-friendly interface for data input and system monitoring. A flexible backend architecture enables the integration of multiple lab devices. The software allows users to easily modify experimental parameters or routines and switch between different lab devices. Compared to previously published projects, we aim to provide a more widely applicable and easily customizable automation software for any experimental setup. The usefulness of this tool was demonstrated in the oxidative coupling of 2,4-dimethyl-phenol to the corresponding 2,2’-biphenol. In this context, the suitable electrolysis parameters for flow electrolysis were optimized by way of design of experiments