The 67th special feature, titled “Electrosynthesis Revolutionizing Synthetic Organic Chemistry,” will focus on electrosynthesis, an innovative technology with the potential for sustainable compound production. Electrosynthesis is a chemical process that uses electricity as the main driving force for reactions, replacing harmful chemicals with electrons. The topic spans both small- and macro-molecule synthesis and highlights the adaptability and promise of electrosynthesis in several areas. The emphasis on the importance of electrosynthesis in the area of green chemistry makes it of interest to professionals and academic researchers in the field of industrial chemistry. This special feature presents a path of change toward a more environmentally friendly, sustainable, and efficient chemical synthesis.

Redox behavior is a fundamental and fascinating feature of polycyclic aromatic hydrocarbons (PAHs). Cyclic voltammetry (CV) measurements are commonly performed to estimate the electronic structure of PAHs and to determine the stability of their oxidation and reduction states. However, the influences of electrolytes on electrochemically oxidized/reduced PAHs have rarely been discussed. In this note, we report voltammetric analyses of five PAHs (anthracene, 9,10-dimethylanthracene, phenanthrene, pyrene, and perylene) in Bu₄NB(C₆F₅)₄/CH₂Cl₂ and Bu₄NTfO/CH₂Cl₂, respectively, to highlight how the electrolyte-coordination affects the oxidative voltammetric behavior of PAHs. In most cases, reversible voltammetric responses were obtained with Bu₄NB(C₆F₅)₄/CH₂Cl₂, suggesting that this electrolyte is enough weakly coordinating to investigate its intrinsic oxidation behavior. On the other hand, irreversible voltammetric responses were obtained with Bu₄NTfO/CH₂Cl₂, indicating that the presence of a relatively coordinating anion, TfO⁻, destabilizes the radical cation species and induces further chemical and electrochemical processes. This study provides hints for rational electrolyte design to properly understand the redox behavior of molecules and maximize the potential of functional molecules for applications related to redox chemistry.

β-Scission from alkoxy radical enables selective C_sp3-C_sp3 bond cleavage under ambient conditions, offering a useful method for organic synthesis. Various photocatalytic systems for β-scission have been reported, where proton-coupled electron transfer (PCET) mechanism plays a key role in the generation of alkoxy radical and thus β-scission. Electrochemical β-scission has been mainly pioneered in the presence of mediator, and a direct electrochemical system has rarely been investigated. Here, we investigated the β-scission via direct electrochemical oxidation using a model compound with β-O-4 linkage. Synthetic experiments suggested smooth progress of β-scission in the presence of collidine as a base. Cyclic voltammetry measurement, voltammetric simulation, and quantum simulation suggested the PCET mechanism is responsible for the electrochemical reaction, which is followed by β-scission process. This report provides fundamental insights into the electrochemical β-scission via direct electron transfer on the electrode, which contribute to future applications such as biomass valorization.

A reactive π-conjugated polymer, bromo-substituted polythiophene, was synthesized by constant potential electrooxidative polymerization of 3-bromo-4-dodecylthiophene in an acetonitrile solution of Bu₄NPF₆. The resulting polymer was applied as a reactive precursor for functional polythiophenes. The protonation via lithiation of the polybromothiophene proceeded quantitatively. The phenylation of the polybromothiophene by the Kumada-Tamao coupling reaction also proceeded with a 70 % efficiency. The changes in optical and electronic properties of the polymers by their reactions are discussed by the results of UV-vis absorption spectroscopy, photoluminescence spectroscopy, and cyclic voltammetric analysis. The emission colors of the bromo-substituted, protonated, and phenylated polymers were green, yellow, and blue, respectively, demonstrating the tunability of this approach.

Cathodic reduction efficiently cleaved N–O bonds. The simple cathodic reduction of Weinreb amides in a divided cell afforded the corresponding amide in good yields. Cyclic voltammetry experiments and density functional theory calculations suggested that the direct reduction of the N-methoxy amide generates the methoxy radical and amide anion. The release of methanol derived from methoxy radical would be the driving force of the N–O bond cleavage.

Herein, we report that the 2,7-dimethoxynaphthyl (2,7-DMN) group is a novel electroauxiliary that is readily installed at the N-α position of a carbamate through Friedel–Crafts-type arylation. The resulting N-α C–C bond is easily cleaved through low-potential electrochemical oxidation to give the corresponding iminium cation.

The electrochemical synthesis of dibenzothiophene S,S-dioxides was achieved by the anodic oxidation of biaryl sulfonyl hydrazides. The use of Bu₄NOTf as the electrolyte in HFIP/CH₃NO₂ (15 : 1) is essential. Several biaryl sulfonyl hydrazides followed by dibenzothiophene S,S-dioxides under mild electrochemical conditions. Control experiments and density functional theory calculations suggested that the electrooxidation of biaryl sulfonyl hydrazides would generate sulfonyl radicals or sulfonyl cations which were converted to dibenzothiophene S,S-dioxides.

Convergent paired electrosynthesis of β-nitroalcohols using an undivided cell was successfully demonstrated by combining anodic generation of benzaldehydes from benzyl alcohols and cathodic formation of nitromethyl anion from nitromethane (CH₃NO₂) via an electrogenerated base (EGB). Linear sweep voltammetry measurements in 0.1 M Bu₄NBF₄/CH₃NO₂ and 0.1 M Bu₄PBF₄/CH₃NO₂ (M = mol L⁻¹), and the electrolysis in the absence of a substrate using a divided cell suggested that N-methylhydroxylamine (CH₃NHOH) may be formed as an EGB. Paired electrolysis of various benzyl alcohols was carried out to provide the corresponding β-nitroalcohols in moderate yields except for p-nitrobenzyl alcohol.

Catechols and their metal complexes are known to participate in electron-transfer reactions in diverse fields. However, most studies have been limited to dioxolene complexes in which the central metal and catechol moieties are directly linked via two adjacent oxygen atoms. Because catechol has oxygen atoms at adjacent positions the oxygen atoms can serve as coordination atoms. In this study, manganese(I) diimine(tricarbonyl) complexes with a free catechol unit are unprecedentedly synthesized to generate an oxidized form, o-quinone, on the complexes. Two types of monodentate ligands are used to control the electronic states of the complexes. Complexes containing the reduced (catechol) form are successfully isolated and characterized using spectroscopic and crystallographic analyses. The redox-responsive nature of the Mn complexes is confirmed by electrochemical analysis. The redox-induced interconversion between the catechol and o-quinone units is observed only in the complex, using electrochemical techniques. This study paves the way for the in situ electrochemical formation of redox-active, unstable organic compounds. Furthermore, the experimental methodologies described herein can establish the redox properties of the resulting species.

Anodic formation of N,O-acetals using amides or carbamates as starting materials, commonly referred to as Shono oxidation, has been an iconic reaction in the field of synthetic organic electrochemistry. However, it is, in principle, not stereoselective and the commonly used neighboring-carbonyl-group participation is not usually effective. Herein, we demonstrate that the use of alkylidene protective groups is extremely effective in controlling the stereoselectivity. Although the detailed mechanism remains an open question, under our reaction conditions, the conformation restriction effect is dominant rather than the steric hindrance effect.

Electrochemical carboxylation of benzyl alcohols even in the absence of an electron-withdrawing group on the phenyl ring was successfully carried out by improving our previous electrolysis conditions. Constant current electrolysis of benzyl alcohols including diphenylmethanol in DMSO containing 0.1 mol dm⁻³ Bu₄NBF₄ in the presence of carbon dioxide using an undivided cell equipped with a platinum plate cathode and a magnesium rod anode at room temperature resulted in direct substitution of a hydroxyl group by a carboxyl group at the benzylic position to give the corresponding arylacetic acids including diphenylacetic acid in moderate to good yields. Although the effect of DMSO as a solvent is still unclear, the results indicate the potential for a useful, convenient, and eco-friendly synthetic method for arylacetic acids from benzyl alcohols.

Fluorine-containing π-conjugated polymers show unique optoelectronic properties because of installed fluorine atoms into their main chains. To manipulate their optoelectronic properties, replacing fluorine atoms with other functional groups or elements by polymer reaction is straightforward. However, polymer reactions applicable to fluorine-containing π-conjugated polymers remain limited to those using nucleophilic aromatic substitution reactions. Here, we report the cathodic hydrodefluorination of a 1,2,4,5-tetrafluorophenylene moieties containing π-conjugated polymer using a platinum (Pt) plate or a zinc (Zn) plate as a working electrode. The use of a Pt plate as a working electrode converts tetrafluorophenylene units to difluorophenylene units and monofluorophenylene units. On the other hand, the use of a Zn plate as a working electrode is found to be effective in suppressing the formation of the monofluorophenylene units. We also demonstrate the facile tuning of the optoelectronic properties of the pristine π-conjugated polymer by the cathodic hydrodefluorination.

Oligosaccharides and polysaccharides containing glucosamine are abundant and essential for many living species, including plants, fungi, insects, and other organisms. TMG-chitotriomycin with the N,N,N-Trimethyl-d-glucosaminyl (TMG) unit shows potent and selective inhibition of insect and fungal GlcNAcases with no inhibition of mammalian and plant GlcNAcases. We have already achieved the total synthesis of TMG-chitotriomycin by automated electrochemical assembly. Thus, we have been interested in synthesis of oligoglucosamine analogues with the TMG unit. Here we synthesized 2- and 3-TMG-chitotriomycin which are analogues of TMG-chitotriomycin and 3-TMG-NAG₅ which is a poly N-acetyl glucosamine (PNAG) pentasaccharide analogue.

The electrode reaction of violurate was studied using optically transparent thin-layer spectroelectrochemical voltammetry. With the application of positive potential, the two strong absorption bands of violurate in the UV region decreased, and an absorption band indicating the formation of violurate neutral radicals arose between them at pH 7.

The pursuit of chiral nanographenes with robust chiral stability and good chiroptical responses is of great interest for material-based applications. However, the most reported preparation processes involve intricate synthetic pathways and harsh conditions, resulting in readily epimerization due to their low epimerization barriers. In this study, we present a streamlined one-pot electrochemical synthesis for a novel double oxaza[7]dehydrohelicene, characterized by a substantial epimerization barrier (33.8 kcal mol⁻¹) and notable chiroptical responses (|g_lum| = 1.5 × 10⁻³). To optimize the electrochemical conditions efficiently, we applied a Bayesian optimization (BO) approach with expected improvement (EI) or lower confidence bound (LCB) as an acquisition function, aiming to maximize exploration and exploitation while minimizing the number of experiments needed to identify global maxima. Additionally, the structural and optical features of this molecule have been studied using X-ray crystallographic analysis, and the absorption and emission behaviors were rationalized based on DFT calculations.

Photocatalytic single-electron transfer (SET) reactions involving perfluoroalkyl halides play a crucial role in synthetic organic chemistry. However, the electrochemical data for these compounds, which are essential in the discussion of the SET process, are missing. In this study, the electrochemical reduction potentials of perfluoroalkyl halides, alkyl halides, and other analogous compounds were investigated in 0.1 M Bu₄NPF₆/CH₃CN using Ag, Pt, and glassy carbon electrodes. The Ag electrode showed remarkable catalytic properties and a positive reduction peak shift during the reduction reaction; this indicates that the Ag electrode is suitable for estimating the electrochemical potential of the SET process. This study provides a comprehensive dataset for the electrochemical measurements of perfluoroalkyl and alkyl halides, which will help synthetic organic chemists select appropriate reaction systems for these compounds.

To enhance the performance of Ru in hydrogen evolution reaction (HER), the design and fabrication of catalytic supports become one of the critical research topics. Carbon supports possessing the excellent conductivity and remarkable cost advantage have become one of the primary choices in fabrications of composite catalysts. In our present studies, the NHPC (N-doped hierarchical porous carbon) supports are fabricated by the carbonizations of soluble starch, ammonium citrate and sodium bicarbonate, and the Ru/NHPC catalysts are successfully prepared by the reactions of RuCl₃·3H₂O with NaBH₄ and NHPC in the ultrasonic treatment. As a result, it is found that Ru goodly dispersed on the surfaces of NHPC in nano sizes, and the Ru/NHPC catalysts manifest the fabulous HER performance. For instance, the overpotential of 11.2 %Ru/NHPC (the loading of RuCl₃·3H₂O is 0.05 g) is 33 mV at a current density of 10 mA cm⁻², which is remarkably lower than 48 mV of glassy carbon electrode (20 %Pt/C) in alkaline medium (1 M (mol L⁻¹) KOH). The Tafel slope of 11.2 %Ru/NHPC is 36 mV dec⁻¹ at 10 mA cm⁻² in the same conditions. Although the 11.2 %Ru/NHPC is in the acidic medium (0.5 M H₂SO₄), it also displays the routine HER performance. In short, this present study provides a useful approach to facilitate the application of Ru as a hydrogen evolution catalyst.

Aqueous Na-ion batteries are attracting attention as candidates for large-scale rechargeable batteries with a high safety level. We proposed a novel electrolyte composed of NaClO₄ dissolved in water, along with ethylene glycol, to serve as an innovative solution for aqueous Na-ion batteries. The potential window of NaClO₄ aqueous-based electrolyte expanded as the ethylene glycol concentration increased. Specifically, when incorporating ethylene glycol into a 7 m (= mol kg⁻¹) NaClO₄ aqueous electrolyte, we observed a favorable cyclability pattern in the context of the NaTi₂(PO₄)₃ anode, akin to that exhibited by a 17 m NaClO₄ aqueous electrolyte. Moreover, the irreversible capacity of NaTi₂(PO₄)₃ decreased as the ethylene glycol concentration increased. This effect was evident even at low rates such as 0.2 mA cm⁻². Notably, the NaTi₂(PO₄)₃ anode’s capacity, when utilizing a 7 m NaClO₄ solution with a higher fraction of ethylene glycol (X_E = 0.5), remained stable at 120 mAh g⁻¹ even after the completion of 15 cycles. On the other hand, the Na₂MnP₂O₇ cathode properties 7 m NaClO₄ aqueous electrolyte could not be improved by adding a small amount of ethylene glycol.

Herein, we report a single-step mechanochemical synthesis of highly porous nitrogen-doped carbon and its electrocatalytic oxygen reduction activity. X-ray diffraction and X-ray photoelectron spectroscopy measurements revealed that solid–gas mechanochemical treatment (MT) using a planetary ball mill cleaved the C–C bonds in carbon black (CB) and simultaneously incorporated nitrogen atoms with a high proportion of quaternary N into the carbon network. MT at a milling speed of 600 rpm yielded nitrogen-doped porous carbon (N-PC) with an optimal combination of nitrogen content of 2.20 at% and surface area of 516 m² g⁻¹, which is 10 times larger than that of CB (51.1 m² g⁻¹). Owing to the high nitrogen content and large surface area, N-PC synthesized by MT at a milling speed of 600 rpm exhibited higher oxygen reduction activity than N-PC synthesized by MT at a milling speed of 800 rpm and porous carbon synthesized by MT at a milling speed of 300 rpm.

Materials with a high Li-ion conductivity and deformability are garnering interest for the facile fabrication of safe all-solid-state batteries with high energy densities. Hence, increasing attention has been focused on Li-containing chloride materials that meet these requirements since they were first reported in 2018 (Asano et al. Advanced Materials 2018, 30 (44), 1803075). In this paper, we report a novel Li-containing chloride of Li₃LuCl₆ with a high Li-ion conductivity (σ_{25 °C} = 3.1 × 10⁻⁴ S cm⁻¹) and sufficient deformability. Furthermore, its defect derivative of Li_3−xLuCl_6−x (x = 1), i.e., Li₂LuCl₅ with a higher Li-ion conductivity (σ_{25 °C} = 5.2 × 10⁻⁴ S cm⁻¹), is synthesized. Scanning electron microscopy confirms the dense packing of both Li₃LuCl₆ and Li₂LuCl₅ as compressed pellets. Hence, Li₂LuCl₅ is presented as a promising solid electrolyte with a high Li-ion conductivity and deformability, which presents a novel opportunity for exploring the composition of Li₂MCl₅ (M: trivalent metal ion) compounds and indicates potential applications as an all-solid-state battery material. Furthermore, as there are no reported cases of high-Li-ion-conductivity chloride materials with the Li₂MCl₅ composition until this work, this study is expected to increase the progress in future studies of LiCl-deficient Li₂MCl₅ compositions with a Li₃MCl₆ composition.

A positive electrode composed of LiCoO₂ (LCO) and Li₃BO₃ (LBO) was formed on one side of a Li_6.6La₃Zr_1.6Ta_0.4O₁₂ (LLZT) solid electrolyte sheet by applying LCO fine powder to LLZT sheet precoated with a Nb thin layer, placing a droplet of aqueous solution of LiOH and H₃BO₃, and being annealed at ∼700 °C in an oxygen atmosphere. After binding a negative electrode, a Li metal foil, on the other side of LLZT sheet precoated with a Li thin layer, electrochemical reaction at the LiCoO₂-Li₃BO₃ composite positive electrode was observed in an all-solid-state battery configuration, i.e., a LCO-LBO/Nb/LLZT/Li cell, by a newly-developed laboratory-based hard x-ray photoelectron spectroscopy (HAXPES) apparatus equipped with a Cr-Kα source (5414.9 eV) and bias application system. A sharp main peak and a broad satellite peak characteristic to LCO were observed in the Co 2p_3/2 region at the pristine state. During charging, i.e., delithiation from LCO, the main peak was asymmetrically broadened to a higher binding energy due to the partial oxidation of Co³⁺ ions at 780 eV to Co⁴⁺ ions at ∼781 eV. In addition, the full width half maximum (FWHM) of the Co⁴⁺ peak increased with increasing the amount of lithium insertion, while that of the Co³⁺ peak remained unchanged. The decrease of satellite peak further confirms the oxidation of Co³⁺ ions. During the subsequent discharging, i.e., lithiation of LCO, those recovered to the original states, confirming the reversible reduction of Co⁴⁺ ions to Co³⁺ ions. When all the peaks were calibrated with respect to B 1s peak corresponding to LBO as a bulk electrolyte, the Co³⁺ peaks shifted consistently with the change in cell voltage during charge/discharge cycles, due to the shift of Fermi level of LCO.