Organic Electrosynthesis

4 January 2019
7 December 2019

Robert Francke

Dan Little

Shinsuke Inagi

Electrosynthesis is naturally a huge topic within the field of electrochemistry. Although it has an extensive history, it has recently seen a new era of growth and is now largely considered its own field rather than simply a sub-discipline. ChemElectroChem, together with Robert Francke (University of Rostock, Germany), Dan Little (University of California Santa Barbara, USA), and Shinsuke Inagi (Tokyo Institute of Technology, Japan), have prepared this Special Issue with the aim to cover the following topics:

  • Organic electrosynthesis (methods, mechanisms, and technology)
  • Electrochemistry of conducting polymers
  • Spectroelectrochemistry with organic molecules
  • Surface modification of electrodes
  • Electrochemical conversion of biorenewables
  • Stereoelectrochemistry

Table of Contents

Free Access

Front Cover: Learning From Vitamin B12-Mediated Reactions: Cobalt(III)−Carbon-Assisted Catalytic C−H Difluoroacylation of (Hetero)Arenes through Controlled-Potential Electrolysis (ChemElectroChem 16/2019)

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The Front Cover shows the electrochemical activation of a vitamin B12 catalyst as well as the obtained difluoroacylated products. More information can be found in the Article by Md. J. Hossain et al. on page 4199 in Issue 16, 2019 (DOI: 10.1002/celc.201900164).

Free Access

Cover Feature: Organic Electrosynthesis: Applications in Complex Molecule Synthesis (ChemElectroChem 16/2019)

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The Cover Feature highlights the various complex organic molecules, which have become possible to access through organic electrosynthesis. Both anodic and cathodic reactions are discussed, showcasing the unique reactivity of electrochemically-generated radical intermediates. More information can be found in the Review by A. Shatskiy et al. on page 4067 in Issue 16, 2019 (DOI: 10.1002/celc.201900435).

Free Access

Cover Feature: Fundamental Input of Analytical Electrochemistry in the Determination of Intermediates and Reaction Mechanisms in Electrosynthetic Processes (ChemElectroChem 16/2019)

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The Cover Feature shows the precious mechanistic information harvested using simple electroanalytical techniques, as opposed to a “blurred” vision of how electrosynthesis proceeds when it is not supported by an electrochemical characterization of the species generated at electrodes. More information can be found in the Minireview by E. Labbé and O. Buriez on page 4118 in Issue 16, 2019 (DOI: 10.1002/celc.201900045).

Free Access

Cover Feature: Analysis of Conjugated Polymers Conductivity by in situ Electrochemical-Conductance Method (ChemElectroChem 16/2019)

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The Cover Feature shows the charging process of a polythiophene-based conducting polymer bearing ionophoric functionality, when this unit interacts with a convenient ion, the conductance of the polymer is affected. Using an in situ electrochemical-conductance method and an interdigital microelectrode, very small changes in the conductance (G) can be detected, obtaining valuable analytical and physical-chemical information about conducting polymers. Artwork provided by H. Segura-Silva, B. A. Frontana-Uribe and G. Salinas. More information can be found in the Minireview by G. Salinas and B. A. Frontana-Uribe on page 4105 in Issue 16, 2019 (DOI: 10.1002/celc.201801488).

Free Access

Cover Feature: Supporting-Electrolyte-Free Electrochemical Methoxymethylation of Alcohols Using a 3D-Printed Electrosynthesis Continuous Flow Cell System (ChemElectroChem 16/2019)

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The Cover Feature shows a newly developed cost-effective 3D-printed electrochemical flow system that fits any electrosynthetic setup including the Electrasyn 2.0. More information can be found in the Communication C. G. W. van Melis et al. on page 4144 in Issue 16, 2019 (DOI: 10.1002/celc.201900815).

Free Access

Learning From Vitamin B12-Mediated Reactions: Cobalt(III)–Carbon-Assisted Catalytic C−H Difluoroacylation of (Hetero)Arenes through Controlled-Potential Electrolysis

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“Difluoroacylation of (hetero)arenes catalyzed by a vitamin B12 derivative is reported, driven by a redox change of cobalt ions in organic media. The process consists of three simple steps: 1) the cobalt(I) species of a vitamin B12 derivative, prepared by controlled-potential electrolysis at −0.8 V vs. Ag/AgCl in DMSO, reacted with BrCF2CO2Et to form a cobalt(III)–CF2CO2Et complex; 2) the homolysis of this complex released a CF2CO2Et radical under visible light irradiation; 3) the generated radical reacted directly with non-activated (hetero)arenes to form desired fluoroalkylated molecules…“ Learn more about the story behind the research featured on the front cover in this issue's Cover Profile. Read the corresponding Article at 10.1002/celc.201900164.

Free Access

Organic Electrosynthesis

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Organic electrosynthesis: Electrosynthesis is naturally a huge topic within the field of electrochemistry. Although it has an extensive history, it has recently seen a new era of growth and is now largely considered its own field rather than simply a subdiscipline. This Special Issue highlights the latest research in this exciting field.

Open Access

Basic Strategies and Types of Applications in Organic Electrochemistry

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Beginners guide: The basic principles for performing electrolysis in organic chemistry under galvanostatic/potentiostatic conditions in undivided/divided/quasi-divided cell designs via direct or indirect electrochemical electron transfer reactions are exemplified at selected examples, including those where paired electrolysis has been used to utilize both electrode reactions in a productive fashion.

Organic Electrosynthesis: Applications in Complex Molecule Synthesis

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So radical! Free radical intermediates have received increasing appreciation because of their unique reactivity profile. Organic electrosynthesis constitutes a promising platform for harnessing the unique reactivity profiles of radical intermediates. This review outlines key applications of electrochemical redox reactions in complex molecule synthesis.

Metabolism-Inspired Electrosynthesis

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Break it down: Recent advances in electro-oxidative drug reactions are reviewed together with a perspective on the future use of electrosynthesis to diversify lead stage drug molecules to enable rapid testing of advanced analogues.

Analysis of Conjugated Polymers Conductivity by in situ Electrochemical-Conductance Method

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In situ electrochemical conductance is an important tool for gaining insight into the chemical and electrical behavior of π-conjugated polymers and electroactive materials. Important information about conductivity models, the type of charge carrier, and carrier-transport pathways, as well as explanations for different phenomena related to charge and mass transport can be extracted from the obtained analyses.

Electrons and Holes as Catalysts in Organic Electrosynthesis

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Role reversal: To most electrochemists, the term ‘electrocatalysis’ is known as the facilitation of a heterogeneous electron transfer by a chemical interaction between the electrode and a substrate. The opposite case, the utilization of a heterogeneous electron exchange to catalyze a chemical reaction, is a much less known but yet a very powerful approach in electrosynthesis. This remarkable strategy has been applied to a number of organic reactions and the goal of this Minireview is to discuss these cases using unifying mechanistic concepts.

Fundamental Input of Analytical Electrochemistry in the Determination of Intermediates and Reaction Mechanisms in Electrosynthetic Processes

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Seeing is believing: Simple electroanalytical approaches are demonstrated to help identify intermediates and understand mechanisms in electrosynthetic processes.

Tapping Renewables: A New Dawn for Organic Electrosynthesis in Aqueous Reaction Media

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Water is my choice! When tapping green electric energy and biogenic compounds for organic electrosynthesis H2O is the best selection from the menu. It is advocated that aqueous reaction media are not only the origin, but the future of organic electrosynthesis. It is shown that using water as the solvent opens interesting perspectives and allows bridges to be created to biological and chemical transformations in a biobased economy.

Electroorganic Synthesis and the Construction of Addressable Molecular Surfaces

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Tools of the trade: In this Minireview, an electroorganic synthesis approach to the construction of addressable, complex molecular surfaces is described along with the parameters that guided the development of that synthetic approach. The result of the work is a synthetic toolbox that will allow microelectrode arrays to be used for the “real-time” monitoring of small molecule interactions with biological targets.

Supporting-Electrolyte-Free Electrochemical Methoxymethylation of Alcohols Using a 3D-Printed Electrosynthesis Continuous Flow Cell System

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Go with the flow: A low-cost small-footprint 3D-printed electrosynthesis continuous flow cell system is designed and adapted to fit a commercially available Electrasyn 2.0. The utility and effectiveness of the combined flow/electrochemistry system over the batch process is demonstrated in the development of an improved and supporting-electrolyte-free version of the anodic methoxymethylation of alcohols.

Oxidative Cleavage of the Acyl-Carbon Bond in Phenylacetone with Electrogenerated Superoxide Anions

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Diamond cut: Cathodic reduction of dissolved molecular oxygen to superoxide anions leads to the oxidative cleavage of the acyl−carbon bond in phenylacetone derivatives. The boron-doped diamond (BDD) electrode enables a highly efficient conversion, owing to BDD's outstanding electrochemical property for utilizing the small amounts of molecular oxygen effectively.

Mn-Catalyzed Electrochemical Synthesis of Quinazolinones from Primary Alcohols/Benzyl Ethers and o-Aminobenzamides

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An efficient electrochemical approach to the synthesis of quinazolinones from o-aminobenzamides using Mn(II) as a redox-metal catalyst is presented. Both benzyl alcohols and benzyl ethers are excellent reaction partners in this electrolysis process, producing quinazolinones in satisfying yields with a wide substrate scope under ambient conditions.

Dehydrogenative Anodic Cyanation Reaction of Phenols in Benzylic Positions

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An electrochemically driven installation of cyano moieties to valuable chemical building blocks via anodic oxidation is presented. The reactive intermediates can be reacted with cyanides to obtain valuable 2-phenylacetonitriles in a facile, protective group-free, metal-free and environmentally-friendly manner. Additionally, the reaction is easily scalable and inherently safe.

Electrochemical Synthesis of Aryl Methoxymethyl Ethers

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Safe and sound: methoxymethyl protected phenols are accessible by our safe, reagent- and reagent waste-free anodic decarboxylation protocol on a preparative scale. A simple undivided cell setup using inexpensive graphite electrodes allow the preparation of valuable protected phenols at high current efficiencies and good functional group tolerance.

Electrochemical Synthesis of [1,2,3]Triazolo[1,5-a]pyridines through Dehydrogenative Cyclization

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The synthesis of [1,2,3]triazolo[1,5-a]pyridines via electrochemical dehydrogenative cyclization of hydrazones of 2-acylpyridines is presented. The reactions are carried out under mild conditions without the need for oxidizing reagents or transition-metal catalysts.

Mixed-Electrolyte-Driven Stereoselective Electrochemical Glycosylation

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A mixed bag: Mixing two different electrolytes enables electrochemical glycosylation in higher stereoselectivity.

Facile Synthesis of α-exo-Methylene Ketones from α,α-Disubstituted Allyl Alcohols by Electrochemical Oxidative Migration

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Easterly migration: Electrochemical oxidative migration of α,α-disubstituted allyl alcohols for α-exo-methylene ketones is reported. The electrochemical approach allowed easy access to synthetically valuable cyclic and acyclic α,β-unsaturated ketones in good-to-excellent yields without the use of external chemical oxidants.

Substitution Pattern-Selective Olefin Cross-Couplings

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Fine tuning: The reactivity of enol ether radical cations can be simply tuned by addition/removal of a methyl group, allowing the development of unique substitution pattern-selective olefin cross-couplings. Anodically generated enol ether radical cations selectively add to appropriately substituted alkenes to afford the corresponding cycloadducts in good-to-excellent yields.

Efficient Synthesis of Mandel Acetates by Electrochemical Carboxylation of Benzal Diacetates

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CO2 fixation: Efficient synthesis of mandel acetates, 2-acetoxy-2-arylacetic acids, is successfully carried out by electrochemical carboxylation of benzal diacetates. The present electrochemical synthesis has a wide scope and provides mandel acetates in good to excellent yields without any hazardous/severe reagents/conditions even by using carbon dioxide as a carbon source of the carboxyl group, and is promising as a conventional, powerful, and environmentally-benign synthetic process.

Electrochemical C−H/N−H Oxidative Cross Coupling of Imidazopyridines with Diarylamines to Synthesize Triarylamine Derivatives

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Couple up: An electrochemical dehydrogenative C−H/N−H cross coupling of imidazopyridines with diarylamine derivatives is developed under transition-metal- and external oxidant-free conditions. A variety of triarylamine derivatives could be obtained in high regioselectivity and moderate-to-good yields.

Electrochemical Pinacol Coupling of Acetophenone Using Boron-Doped Diamond Electrode

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Farewell to metals: boron-doped diamond (BDD) is a carbon-based, highly robust electrode material for electrosynthesis. The BDD cathode enables metal-free pinacol coupling reactions of acetophenone. The presented protocol is sustainable and inherently safe, which provides new perspectives for the old pinacol coupling reaction.

Learning From Vitamin B12-Mediated Reactions: Cobalt(III)−Carbon-Assisted Catalytic C−H Difluoroacylation of (Hetero)Arenes through Controlled-Potential Electrolysis

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Radical discovery: A naturally derived vitamin B12, which has a cobalt ion in the corrin-ring, acts as a good catalyst for difluoroacylation reaction of arenes and heteroarenes driven by controlled-potential electrolysis at −0.8 V vs. Ag/AgCl under photoirradiation in DMSO. The reaction proceeds through a radical pathway mediated by homolytic cleavage of the cobalt(III)−carbon bond.

Polymer of Intrinsic Microporosity (PIM-7) Coating Affects Triphasic Palladium Electrocatalysis

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A microporous polymer film of PIM-7 is coated onto a glassy carbon electrode, the effects on (i) aqueous solution based, (ii) solid state surface immobilised, and (iii) electrocatalytic processes on electrodeposited palladium are investigated. Triphasic electrochemical processes involving gas evolution are beneficially affected by the presence of microporous PIM-7 polymer coated over the electrode surface.

Electrochemical Oxidation of the Phenolic Benzotriazoles UV-234 and UV-327 in Organic Solvents

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Long-lived phenoxyl radicals. EPR spectroscopic measurements obtained during the electrochemical oxidation of ultraviolet stabilizer phenolic benzotriazoles under weakly basic conditions prove the existence of indefinitely long-lived phenoxyl radicals that are in equilibrium with their corresponding phenolate anions

Rapid and High-Yield Electrosynthesis of Benzisoxazole and Some Derivatives

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Selective electrosynthesis: constant-potential electrolysis (CPE) is employed to electrosynthesize anthranil and some of its congeners. Electrosynthesis is carried out at reticulated vitreous carbon cathodes in DMF containing 0.050 M TBABF4 and 4-chlorophenol (as a proton donor), featuring high yield and short reaction time. The process is catalyst-free and environmentally green, and the proton donor can be recovered entirely at the end of the process.

Electrocatalytic Fixation of Carbon Dioxide with Amines and Arylketones

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An efficient cross-coupling reaction of carbon dioxide with amines and arylketones is developed by virtue of a simple electrochemical oxidation under mild and metal-free conditions, providing a variety of O-β-oxoalkyl carbamates with moderate to good yields.

Cathodic Behaviour of Dicationic Imidazolium Bromides: The Role of the Spacer

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Carbene formation: The electrochemical reduction of imidazolium dications leads to the formation of the corresponding N-heterocyclic carbenes, which were detected after reaction with elemental sulfur. The type and yield of cathodic reduction products strongly depend on the spacer between the two imidazolium rings.

Metabolism Mimicry: An Electrosynthetic Method for the Selective Deethylation of Tertiary Benzamides

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Copycat: An electrochemical method that mimics cytochrome P450-mediated dealkylation is reported. Changing from controlled potential to controlled current conditions gave dealkylation over the expected dehydrogenative coupling. The method is operationally straightforward and solely affords mono deethylation products. Application of the electrochemical method to the insect repellent, DEET, affords on a preparative scale the major human metabolite in a single step.

Spray-Flame-Synthesized LaCo1−xFexO3 Perovskite Nanoparticles as Electrocatalysts for Water and Ethanol Oxidation

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Spray-flame synthesized LaCo1−xFexO3 perovskites show promising electrocatalytic activity towards the oxygen evolution reaction and ethanol electrooxidation. The selectivity of the ethanol oxidation reaction is influenced by the Fe content, with acetic aldehyde being detected on Fe rich perovskites while acetate is generated on the Fe-free catalysts up to potentials of 1.7 V vs. RHE.

Electrochemically Mediated Atom Transfer Radical Polymerization of Methyl Methacrylate: The Importance of Catalytic Halogen Exchange

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Gaining self-control! Electrochemically-mediated ATRP of methyl methacrylate, catalyzed by copper complexes in [BMIm][OTf] or ethanol, is well-controlled through catalytic halogen exchange by converting the C-Br chain-end functional group to C-Cl.

Electrosynthesis of Oxazol-2(3H)-Ones and Diaroylhydrazines from 1,2-Dicarbonyl Compounds and Arenediazonium Salts

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Electrochemical preparative-scaled concomitant reduction of aromatic 1,2-dicarbonyl substrates and arenediazonium tetrafluoroborates in N-methylformamide/LiClO4 as solvent-supporting-electrolyte system is used to obtain new five-membered oxazol-2(3H)-one heterocycles and 1,2-diaroylhydrazines in good yield.

Electrocatalytic Oxidation of Glycerol on Platinum Single Crystals in Alkaline Media

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Glycerol electrooxidation on Pt single crystal electrodes is a strongly structure sensitive reaction. In alkaline media the electrode activity is highly suppressed with subsequent potentiodynamic cycles. The Pt(100) electrode is less prone to poisoning in than Pt(110) and Pt(111). In-situ FTIR results are suggesting that the mechanism undergoes through glycerol dehydrogenation to alkoxydes, followed by formation of aldehyde intermediates adsorbed as η1(O)-aldehyde and η1(C)-acyl geometry.

Electrochemical Properties of 9,9′-Spiro-Bifluorenes Containing Group 14 Elements (C, Si, Ge, Sn)

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Spiro-bifluorenes electrochemistry: Cyclic voltammograms of four spiro-bifluorenes containing C, Si, Ge and Sn as the central atom are recorded in acetonitrile-dichloromethane. Controlled potential anodic oxidation is executed on a Pt anode. Each substrate behaves differently, and as a result, varying major products are found. In all cases, chlorinated products are formed additionally. A plausible mechanism for the formation of the variety of products is suggested.

Iodophenylsulfonates and Iodobenzoates as Redox-Active Supporting Electrolytes for Electrosynthesis

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A study on a number of ionically tagged iodoarenes shows that 4- and 2-iodobenzenesulfonates are useful mediators for electroorganic synthesis. The ionic tag allows for electrolysis without supporting-electrolyte additives and enables a facile recovery of the mediator from the reaction mixture.

Impact of the Replacement of a Triphenylamine by a Diphenylmethylamine Unit on the Electrochemical Behavior of Pentaerythritol-Based Push-Pull Tetramers

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Push-pull networks: Arylamine derivatives constitute outstanding building blocks for the preparation of electroactive materials for opto-electronic applications. Here, we study and rationalize the electrochemical dimerization tendencies of two D-π-A push-pull molecules based on arylamine donor groups through spectroelectrochemistry and theoretical calculations. The electrochemical behavior of one of the two push-pull molecules is exploited in its tetrameric counterpart to generate 3D push-pull networks upon electropolymerization.

Self-Standing Membranes Consisting of Inherently Chiral Electroactive Oligomers: Electrosynthesis, Characterization and Preliminary Tests in Potentiometric Setups

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Take a stand: Electrosynthesis of self-standing chiral electroactive membranes, consisting of “inherently chiral” electroactive open and closed oligomers, with high chiroptical manifestations, characterized and preliminarily tested in an ion-selective-electrode-like potentiometric setup.