3D printed electrochemical sensor and microfluidic system for the detection of L-tryptophan using degradable material

Herein, we constructed an integrated system for L-tryptophan (L-Trp) detection by assembling an electrochemical sensor and a microfluidic platform. Amongst, the sensor was printed using conductive polymer filaments and then chemically activated to expose porous nanostructure on the surface. A calibration curve was established between 31.26-1000.00 μmol/L and the limit of detection (LOD) was 10.41 μmol/L. The sensor exhibited satisfactory reproducibility, selectivity and stability. The recovery ranged between 99.06-102.09 % with relative standard deviations less than 5.21 %. The results show that L-Trp undergoes a two-proton, two-electron transfer in the anodic reaction. Once integrated into a printed microfluidic module from photosensitive resin, the sensor showed a wider detection range (15.00-70.00, 100-4000 μmol/L) with a lower LOD (5.00 μmol/L), which may be due to faster mass transfer in microfluidics. The consistency and validity were affirmed with ultra-visible spectrophotometer and HPLC. The integrated system allows point-of-testing owing to its small size, portability and low cost.

Electrifying Redox-Neutral Palladium-Catalyzed Carbonylations: Multielectron Transfer as a Catalyst Driving Force

Palladium-catalyzed bond-forming reactions such as carbonylations offer an efficient and versatile avenue to access products from often feedstock reagents. However, the use of catalysts also comes with a cost, as their need to be regenerated after each product-forming cycle requires balancing thermal operations. The latter can lead to high barriers even with catalysts as well as restrict their application to many products. We introduce herein an alternative approach to palladium catalyst design, where instead electrochemical potential can drive catalysis by continual two-electron cycling of the metal oxidation state. The power behind these redox steps offers a route to carry out carbonylation reactions, including the catalytic synthesis of high-energy aroyl halide electrophiles, at unprecedentedly mild ambient temperature and pressure. More generally, analysis suggests this catalyst functions by a distinct multi-electron exchange pathway, where two-electron reduction enables oxidative addition and two-electron oxidation drives product elimination. The combination creates a unique platform where both these reverse operations are favored in the same system and with electrochemical potential energy as the only added energy source.

Cascade Catalytic Systems for Converting CO2 into C2+ Products

The excessive emission and continuous accumulation of CO2 have precipitated serious social and environmental issues. However, CO2 can also serve as an abundant, inexpensive, and non-toxic renewable C1 carbon source for synthetic reactions. To achieve carbon neutrality and recycling, it is crucial to convert CO2 into value-added products through chemical pathways. Multi-carbon (C2+) products, compared to C1 products, offer a broader range of applications and higher economic returns. Despite this, converting CO2 into C2+ products is difficult due to its stability and the high energy required for C-C coupling. Cascade catalytic reactions offer a solution by coordinating active components, promoting intermediate transfers, and facilitating further transformations. This method lowers energy consumption. Recent advancements in cascade catalytic systems have allowed for significant progress in synthesizing C2+ products from CO2. This review highlights the features and advantages of cascade catalysis strategies, explores the synergistic effects among active sites, and examines the mechanisms within these systems. It also outlines future prospects for CO2 cascade catalytic synthesis, offering a framework for efficient CO2 utilization and the development of next-generation catalytic systems.

Advanced development of finite element analysis for electrochemical catalytic reactions

The development of robust simulation techniques is crucial for elucidating electrochemical catalytic mechanisms and can even provide guidance for the tailored design and regulation of highly efficient catalysts. Finite element analysis (FEA), as a powerful numerical simulation tool, can effectively simulate and analyze the sophisticated processes involved in electrochemical catalytic reactions and unveil the underlying microscopic mechanisms. By employing FEA, researchers can gain better insights into reaction kinetics and transport processes, optimize electrode design, and predict electrochemical performance under various reaction conditions. Consequently, the application of FEA in electrochemical catalytic reactions has emerged as a critical area of current research and a summary of the advanced development of FEA for electrochemical catalytic reactions is urgently required. This review focuses on exploring the applications of FEA in investigating the crystal structure effect, tip effect, multi-shell effect, porous structure effect, and mass transfer phenomena in electrochemical reactions. Particularly emphasized are its applications in the fields of CO2 reduction, oxygen evolution reaction, and nitrogen reduction reaction. Finally, the challenges encountered by this research field are discussed, along with future directions for further advancement. We aim to provide comprehensive theoretical and practical guidance on FEA methods for researchers in the field of electrochemical catalysis, thereby fostering the advancement and wider implementation of FEA within this domain.

Reverse-engineered Electro-Fenton for the selective synthesis of oxalic or oxamic acid through the degradation of acetaminophen: A novel green electrocatalytic refinery approach

The Electro-Fenton process (EF) has been conventionally applied to efficiently degrade refractory and/or toxic pollutants. However, in this work, EF was used as a reverse engineering tool to selectively synthesize highly value-added products (oxalic or oxamic acid) through the degradation of the model pollutant acetaminophen, a widely used analgesic and antipyretic drug. It was found that the production of either oxalic or oxamic acid is dictated by the applied current density. Hence, oxalic acid is favored at low current densities trough a mechanism dominated by homogeneous •OH radical oxidation, while oxamic acid is the majoritarian product at high current densities where electron transfer at the anode surface becomes an important mechanism in combination with •OH oxidation. Under optimal reaction conditions (0.71 mA cm-2 and 100 mg l-1 of initial total organic carbon (TOC) concentration), up to 227.1 ± 26.3 mg l-1 of oxalic acid were produced, with high yield and selectivity of 54.9 ± 5.1 % and 94.7 ± 9.9 %, respectively (the TOC removal was 42.0 ± 2.4 %). In the case of oxamic acid, the highest concentration of 33.8 ± 2.1 mg l-1 was produced at 2.13 mA cm-2 and an initial TOC concentration of 50 mg l-1, which represented a yield of 18.7 ± 0.3 % and 60.9 ± 9.3 % selectivity (71.1 ± 4.4 % of TOC removal). It is worth noting that at low current density when oxalic acid is favored, the selectivity for both products was 100 %, meaning that those were the only products remaining in the solution, with oxalic acid as the major product (94.7 ± 9.9 % with initial TOC of 100 mg l-1, and 98.7 ± 0.9 % with initial TOC of 50 mg l-1). This is a pioneer work on EF applications to the field of wastewater valorization/refining through the recovery of value-added products within a circular economy.

Paired Electrosynthesis at Interdigitated Microband Array Electrodes without Intentionally Added Electrolyte: C-C Coupling of Dicyanobenzenes with Methanol

The formation of substituted benzyl alcohols from dicyanobenzenes and methanol (C-C coupling) is demonstrated as a model system for paired electrosynthesis and investigated at interdigitated microband array electrodes in a microreactor with/without intentionally added supporting electrolyte. A Pt-Pt microband array with 5 μm bands separated by 5 μm gaps is employed in a dimethyl sulfoxide (DMSO) solvent. Yields are optimized to approximately 50% at the point of 100% conversion. The mechanism is investigated by employing isotope labeling (CD3OD, CH3OD, d 6-DMSO, 13CH3OH). The methylene group (12C or 13C) is obtained with H2, D2, and DH substitution patterns, and a hypothesis for a corresponding mechanism is discussed aided with density functional theory (DFT) calculations. Implications for sustainable electrosynthesis at paired microband electrodes are discussed.

Mechanistic insights into the visible-light-driven O-arylation of carboxylic acids catalyzed by xanthine-based nickel complexes

We present a photocatalytic protocol for the O-arylation of carboxylic acids using nickel complexes bearing C8-pyridyl xanthines. Our studies suggest that the underlying mechanism operates independently of external photosensitizers. Stoichiometric experiments and crystallographic studies characterize the catalytically relevant Ni complexes. Spectroscopic and computational investigations propose a thermally controlled Ni(i)/Ni(iii) cycle followed by a photochemical regeneration of Ni(i) species. Furthermore, the pathways leading to the hydrodehalogenation of aryl halides, the comproportionation of Ni(i) and Ni(iii) species, the dimerization of Ni(i) intermediates and the influence of the counter ion on the cross-coupling reaction are unveiled. These investigations offer a comprehensive mechanistic understanding of the photocatalytic cross-coupling reaction catalyzed by a single Ni species and highlight key aspects of nickel-catalyzed metallaphotoredox reactions.

Synergistic enhancement of electrochemical alcohol oxidation by combining NiV-layered double hydroxide with an aminoxyl radical

Electrochemical alcohol oxidation (EAO) represents an effective method for the production of high-value carbonyl products. However, its industrial viability is hindered by suboptimal efficiency stemming from low reaction rates. Here, we present a synergistic electrocatalysis approach that integrates an active electrode and aminoxyl radical to enhance the performance of EAO. The optimal aminoxyl radical (4-acetamido-2,2,6,6-tetramethylpiperidine 1-oxyl) and Ni0.67V0.33-layered double hydroxide (LDH) are screen as cooperative electrocatalysts by integrating theoretical predictions and experiments. The Ni0.67V0.33-LDH facilitates the adsorption and activation of N-(1-hydroxy-2,2,6,6-tetramethylpiperidin-4-yl)acetamide (ACTH) via interactions with ketonic oxygen, thereby improving selectivity and yield at high current densities. The electrolysis process is scaled up to produce 200 g of the steroid carbonyl product 8b (19-Aldoandrostenedione), achieving a yield of 91% and a productivity of 243 g h-1. These results represent a promising method for accelerating electron transfer to enhance alcohol oxidation, highlighting its potential for practical electrosynthesis applications.

Electrochemical C-O and C-N Arylation using Alternating Polarity in flow for Compound Libraries

Etherification and amination of aryl halide scaffolds are commonly used reactions in parallel medicinal chemistry to rapidly scan structure-activity relationships with abundant building blocks. Electrochemical methods for aryl etherification and amination demonstrate broad functional group tolerance and extended nucleophile scope compared to traditional methods. Nevertheless, there is a need for robust and scale-transferable workflows for electrochemical compound library synthesis. Herein we describe a platform for automated electrochemical synthesis of C-X arylation (X=NH, OH) in flow to access compound libraries. A comprehensive Design of Experiment (DoE) study identifies an optimal protocol which generates high yields across>30 aryl halide scaffolds, diverse amines (including electron-deficient sulfonamides, sulfoximines, amides, and anilines) and alcohols (including serine residues within peptides). Reaction sequences are automated on commercially available equipment to generate libraries of anilines and aryl ethers. The unprecedented application of potentiostatic alternating polarity in flow is essential to avoid accumulating electrode passivation. Moreover, it enables reactions to be performed in air, without supporting electrolyte and with high reproducibility over consecutive runs. Our method represents a powerful means to rapidly generate nucleophile independent C-X arylation compound libraries using flow electrochemistry.

Transition-Metal Free Amination and Hydrodefluorination of Aryl Fluorides Promoted by Solvated Electrons

Cross-coupling reactions for constructing C-N bonds represent a pivotal advancement in chemical science. Traditional methodologies, including nucleophilic aromatic substitution (SNAr) and transition metal-catalyzed cross-couplings, have limitations concerning aryl scope, reliance on toxic and costly transition-metal catalysts, and issues related to atom economy and waste generation from ligands and additives. In this work, we introduce a novel method for aminating neutral, electron-rich, and electron-deficient aryl halides, eliminating the need for transition metals. Our approach involves the activation of aryl halides using solvated electrons generated from granulated lithium and sonication. This serves as a sustainable source of reducing power, facilitating the efficient formation of C-N bonds under near ambient conditions. Competitive selectivity studies between halide and ester functionalities were explored. Reaction scope and conducted mechanistic studies which supported the proposed radical-nucleophilic substitution (SRN1) mechanism for the reaction. Notably, the developed reaction has a highly competitive reductive dehalogenation pathway during the C-N coupling reaction, and this mechanistic divergency was thoroughly explored. This work not only broadens the scope of C-N coupling reactions which typically employs aryl bromides and iodides and rarely aryl fluorides which is also equally abundant, but also introduces a new way to do C-N coupling reactions using solvated electrons.

Influence of Complex Multiphasic Flow on the Thiuram Electrosynthesis in a Microchannel Reactor

As an important sustainable method for chemical synthesis, organic electrosynthesis experienced a renaissance in recent years for its excellent atom economy. Although microchannel reactors have been proposed to advanced electrosynthesis devices to obtain low energy cost and high reaction performance, the complex multiphasic flow in the electrochemical microchannels are very less reported and the effects of flow condition on the electrosynthesis reaction are less reported. Taking the electrosynthesis of tetraethyl thiuram disulfide (TETD) as a typical case, we developed a visualized electrochemical microchannel reactor equipped with fluorine-doped tin oxide (FTO) loaded glass electrode to investigate the gas-liquid-liquid triple phase flow pattern and the main factors influenced the response current at certain applied cell voltage. The gas-liquid-liquid hybrid flow with low gas hold-up and high liquid flow rate was found crucial for preventing coverage of TETD on the electrode, which provided 23.1 % low current attenuation ratio at 3.0 V cell voltage. The research not only exhibited the complex evolution mechanism of the response current, but also showed the importance of flow condition control for balancing the work efficiency and energy consumption of electrosynthesis process.

Electrochemically Induced, Metal Free Synthesis of 2-substituted chroman-4-ones

Electrochemically induced, decarboxylative functionalization of chromone-3-carboxylic acids by N-hydroxyphthalimide esters as alkyl radical precursors was studied. Electrochemical protocol offers a sustainable and green approach, obviating the need for catalysts, relying on the direct reduction of NHPI esters using electric current. Developed protocol provides a straightforward route to the synthesis of diverse molecules with potential biological activity.

Linear Paired Electrolysis Enables Redox-Neutral (3 + 2) Annulation of Benzofuran with Vinyldiazo Compounds

Electrosynthesis has emerged as a versatile and sustainable tool in organic chemistry, offering an efficient pathway for the construction of complex molecular architectures under mild and environmentally benign conditions. Traditional electrochemical approaches, however, predominantly rely on either anodic oxidation or cathodic reduction, limiting their capacity to achieve redox-neutral transformations using a single electrode. In this work, we introduce a linear paired electrolysis strategy that circumvents these limitations, enabling a redox-neutral (3 + 2) annulation of benzofuran with vinyldiazo compounds. This method facilitates the formation of benzofuran-fused tricyclic scaffolds, which are valuable in synthetic chemistry and medicinal applications. The transformation proceeds through sequential anodic oxidation and cathodic reduction, leveraging a radical cation pathway to deliver polycyclic compounds with high selectivity. The efficiency and mechanism of this process are thoroughly validated using cyclic voltammetry and in situ electrochemical mass spectrometry (EC-MS) and supported by theoretical calculations, shedding light on the potential of redox-neutral electrochemical transformations.

Monomeric and Dimeric Boron (III) Subphthalocyanines Functionalized with 4-Hydroxy-Benzoic Acid as Potential Photosensitizers and Photocatalysts in Sulfoxidation

Axial modification of boron (III) subphthalocyanine bromides with 4-hydroxy-benzoic acid successfully led to the formation of the macrocycles with anchored 4-carboxyphenoxy group [RsPcPHBA] (R=tBu, H) in the axial position and to a new dimer [sPcPHBAsPc] as minor product. Tri-tert-butyl and unsubstituted subphthalocyanines bearing benzoate ([tBusPcBA], [sPcBA]), phenoxy-group ([tBusPcOPh], [sPcOPh])) in the axial position, have been also investigated as well as control sPcs. All compounds were characterized by NMR, IR, UV-Vis and mass spectrometry. The electrochemical properties were studied using cyclic voltammetry (CV) and square wave voltammetry (SWV). Singlet oxygen generation was systematically measured for all synthesized [RsPcX] by kinetic method of chemical trap decomposition (DPBF) and by determination of phosphorescence of singlet oxygen (at 1270 nm). Axially modified subphthalocyanines exhibit high quantum yields of singlet oxygen (1O2) generation (0.47-0.62). The observed exceptional photostability in oxygen-saturated ethanol or toluene solutions and high 1O2 quantum yields allows to use [tBusPcPHBA] as photocatalysts of selective oxidative transformations of organic sulfides to sulfoxides. Loading the catalyst to 9.7 ⋅ 10-2 mol % made it possible to achieve complete conversion of the substrate (TON up to 1700).

Electroprecipitating the Sulfate Radical Anion Amplifies Electrochemiluminescence in Space and Time

We have discovered a strategy to synthesize reactive radical salts, effectively bottling up radicals in space and time for future use. We apply this new principle to electrochemiluminescence (ECL) through the simultaneous electro-reduction of peroxydisulfate, S2O82-, and tris(bipyridine)ruthenium(II), [Ru(bpy)3]2+ in a water/acetonitrile mixture. The electrode generates a concentration profile exceeding the solubility of the cation and anion pair, promoting precipitation. After the application of a potential, leads are disconnected, and the crystals electrolessly chemiluminesce during dissolution and can be transported to other solutions for later chemiluminescence uses. Our method extends ECL hundreds of micrometers from the electrode surface and increases the ECL lifetime by orders of magnitude. Control experiments, including electron spin resonance, validate the crystallization of SO4•-, allowing detailed mechanistic insight. We demonstrate platform generalizability by precipitating a radical salt made of calcium and SO4•-, and we demonstrate the salt's ability to drive chemiluminescence. Our results emphasize the elegant chemical tenet that extremely reactive radicals can be bottled up as solids to be used as future reagents if precipitation occurs more quickly than the radical lifetime.

Microfluidic programmable strategies for channels and flow

This review summarizes programmable microfluidics, an advanced method for precise fluid control in microfluidic technology through microchannel design or liquid properties, referring to microvalves, micropumps, digital microfluidics, multiplexers, micromixers, slip-, and block-based configurations. Different microvalve types, including electrokinetic, hydraulic/pneumatic, pinch, phase-change and check valves, cater to diverse experimental needs. Programmable micropumps, such as passive and active micropumps, play a crucial role in achieving precise fluid control and automation. Due to their small size and high integration, microvalves and micropumps are widely used in medical devices and biological analysis. In addition, this review provides an in-depth exploration of the applications of digital microfluidics, multiplexed microfluidics, and mixer-based microfluidics in the manipulation of liquid movement, mixing, and splitting. These methodologies leverage the physical properties of liquids, such as capillary forces and dielectric forces, to achieve precise control over fluid dynamics. SlipChip technology, which branches into rotational SlipChip and translational SlipChip, controls fluid through sliding motion of the microchannel. On the other hand, innovative designs in microfluidic systems pursue better modularity, reconfigurability and ease of assembly. Different assembly strategies, from one-dimensional assembly blocks and two-dimensional Lego®-style blocks to three-dimensional reconfigurable modules, aim to enhance flexibility and accessibility. These technologies enhance user-friendliness and accessibility by offering integrated control systems, making them potentially usable outside of specialized technical labs. Microfluidic programmable strategies for channels and flow hold promising applications in biomedical research, chemical analysis and drug screening, providing theoretical and practical guidance for broader utilization in scientific research and practical applications.

A photoelectrocatalytic system as a reaction platform for selective radical-radical coupling

The selection of electrode material is a critical factor that determines the selectivity of electrochemical organic reactions. However, the fundamental principles governing this relationship are still largely unexplored. Herein, we demonstrate a photoelectrocatalytic (PEC) system as a promising reaction platform for the selective radical-radical coupling reaction owing to the inherent charge-transfer properties of photoelectrocatalysis. As a model reaction, the radical trifluoromethylation of arenes is shown on hematite photoanodes without employing molecular catalysts. The PEC platform exhibited superior mono- to bis-trifluoromethylated product selectivity compared to conventional electrochemical methods utilizing conducting anodes. Electrochemical and density functional theory (DFT) computational studies revealed that controlling the kinetics of anodic oxidation of aromatic substrates is essential for increasing reaction selectivity. Only the PEC configuration could generate sufficiently high-energy charge carriers with controlled kinetics due to the generation of photovoltage and charge-carrier recombination, which are characteristic features of semiconductor photoelectrodes. This study opens a novel approach towards selective electrochemical organic reactions through understanding the intrinsic physicochemical properties of semiconducting materials.

Nickel-Catalyzed Electrochemical Cross-Electrophile C(sp2)-C(sp3) Coupling via a NiII Aryl Amido Intermediate

Cross-electrophile coupling (XEC) between aryl halides and alkyl halides is a streamlined approach for C(sp2)-C(sp3) bond construction, which is highly valuable in medicinal chemistry. Based on a key NiII aryl amido intermediate, we developed a highly selective and scalable Ni-catalyzed electrochemical XEC reaction between (hetero)aryl halides and primary and secondary alkyl halides. Experimental and computational mechanistic studies indicate that an amine secondary ligand slows down the oxidative addition process of the Ni-polypyridine catalyst to the aryl bromide and a NiII aryl amido intermediate is formed in situ during the reaction process. The relatively slow oxidative addition is beneficial for enhancing the selectivity of the XEC reaction. The NiII aryl amido intermediate stabilizes the NiII-aryl species to prevent the aryl-aryl homo-coupling side reactions and acts as a catalyst to activate the alkyl bromide substrates. This electrosynthesis system provides a facile, practical, and scalable platform for the formation of (hetero)aryl-alkyl bonds using standard Ni catalysts under mild conditions. The mechanistic insights from this work could serve as a great foundation for future studies on Ni-catalyzed cross-couplings.

De novo construction of amine-functionalized metal-organic cages as heterogenous catalysts for microflow catalysis

Microflow catalysis is a cutting-edge approach to advancing chemical synthesis and manufacturing, but the challenge lies in developing efficient and stable multiphase catalysts. Here we showcase incorporating amine-containing metal-organic cages into automated microfluidic reactors through covalent bonds, enabling highly continuous flow catalysis. Two Fe4L4 tetrahedral cages bearing four uncoordinated amines were designed and synthesized. Post-synthetic modifications of the amine groups with 3-isocyanatopropyltriethoxysilane, introducing silane chains immobilized on the inner walls of the microfluidic reactor. The immobilized cages prove highly efficient for the reaction of anthranilamide with aldehydes, showing superior reactivity and recyclability relative to free cages. This superiority arises from the large cavity, facilitating substrate accommodation and conversion, a high mass transfer rate and stable covalent bonds between cage and microreactor. This study exemplifies the synergy of cages with microreactor technology, highlighting the benefits of heterogenous cages and the potential for future automated synthesis processes.

Nickel-Catalyzed Highly Selective Radical C-C Coupling from Carboxylic Acids with Photoredox Catalysis

Controlling the cross-coupling reaction between two different radicals is a long-standing challenge due to the process occurring statistically, which would lead to three products, including two homocoupling products and one cross-coupling product. Generally, the cross-coupling selectivity is achieved by the persistent radical effect (PRE) that requires the presence of a persistent radical and a transient radical, thus resulting in limited radical precursors. In this paper, a highly selective cross-coupling of alkyl radicals with acyl radicals to construct C(sp2)-C(sp3) bonds, or with alkyl radicals to construct C(sp3)-C(sp3) bonds have been achieved with the readily available carboxylic acids and their derivatives (NHPI ester) as coupling partners. The success originates from the use of tridentate ligand (2,2' : 6',2''-terpyridine) to enable radical cross-coupling process to Ni-mediated organometallic mechanism. This protocol offers a facile and flexible access to structurally diverse ketones (up to 90 % yield), and also a new solution for the challenging double decarboxylative C(sp3)-C(sp3) coupling. The broad utility and functional group tolerance are further illustrated by the late-stage functionalization of natural-occurring carboxylic acids and drugs.

Bromide-Mediated Silane Oxidation: A Practical Counter-Electrode Process for Nonaqueous Deep Reductive Electrosynthesis

The counter-electrode process of an organic electrochemical reaction is integral for the success and sustainability of the process. Unlike for oxidation reactions, counter-electrode processes for reduction reactions remain limited, especially for deep reductions that apply very negative potentials. Herein, we report the development of a bromide-mediated silane oxidation counter-electrode process for nonaqueous electrochemical reduction reactions in undivided cells. The system is found to be suitable for replacing either sacrificial anodes or a divided cell in several reported reactions. The conditions are metal-free, use inexpensive reagents and a graphite anode, are scalable, and the byproducts are reductively stable and readily removed. We showcase the translation of a previously reported divided cell reaction to a >100 g scale in continuous flow.

Photoelectrochemical Fe/Ni cocatalyzed C-C functionalization of alcohols

The simultaneous activation of reactants on the anode and cathode via paired electrocatalysis has not been extensively demonstrated. This report presents a paired oxidative and reductive catalysis based on earth-abundant iron/nickel cocatalyzed C-C functionalization of ubiquitous alcohols. A variety of alcohols (i.e., primary, secondary, tertiary, or unstrained cyclic alcohols) can be activated at very low oxidation potential of (~0.30 V vs. Ag/AgCl) via photoelectrocatalysis coupled with versatile electrophiles. This reactivity yields a wide range of structurally diverse molecules with broad functional group compatibility (more than 50 examples).

Paired Electrosynthesis at Interdigitated Microband Electrodes: Exploring Diffusion and Reaction Zones in the Absence of a Supporting Electrolyte

Electrosynthesis traditionally requires dedicated reactor systems and an added electrolyte, although some paired electrosynthesis processes are possible at interdigitated microband electrodes simply immersed in solution and without an intentionally added electrolyte. Here, 1,1'-ferrocenedimethanol oxidation and activated olefin electro-hydrogenation reactions are investigated as model processes at a Pt-Pt interdigitated microband array electrode with 5 μm width and with 5 μm interelectrode gap. Voltammetric responses for electro-hydrogenation are discussed, and product yields are determined in methanol (MeOH) in the presence/absence of an added electrolyte (LiClO4). An isotope effect is observed in CH3OD solvent, leading to olefin monodeuteration linked to a fast EC-type process close to the cathode surface (in the cathode reaction zone) rather than to charge annihilation in the interelectrode zone. A finite element simulation is employed to visualize/discuss reaction zones and to contrast the rate of charge annihilation processes with/without a supporting electrolyte.

Intricacies of Mass Transport during Electrocatalysis: A Journey through Iron Porphyrin-Catalyzed Oxygen Reduction

Electrochemical steps are increasingly attractive for green chemistry. Understanding reactions at the electrode-solution interface, governed by kinetics and mass transport, is crucial. Traditional insights into these mechanisms are limited, but our study bridges this gap through an integrated approach combining voltammetry, electrochemical impedance spectroscopy, and electrospray ionization mass spectrometry. This technique offers real-time monitoring of the chemical processes at the electrode-solution interface, tracking changes in intermediates and products during reactions. Applied to the electrochemical reduction of oxygen catalyzed by the iron(II) tetraphenyl porphyrin complex, it successfully reveals various reaction intermediates and degradation pathways under different kinetic regimes. Our findings illuminate complex electrocatalytic processes and propose new ways for studying reactions in alternating current and voltage-pulse electrosynthesis. This advancement enhances our capacity to optimize electrochemical reactions for more sustainable chemical processes.

Electro/Ni Dual-Catalyzed Decarboxylative C(sp3)-C(sp2) Cross-Coupling Reactions of Carboxylates and Aryl Bromide

Paired redox-neutral electrolysis offers an attractive green platform for organic synthesis by avoiding sacrificial oxidants and reductants. Carboxylates are non-toxic, stable, inexpensive, and widely available, making them ideal nucleophiles for C-C cross-coupling reactions. Here, we report the electro/Ni dual-catalyzed redox-neutral decarboxylative C(sp3)-C(sp2) cross-coupling reactions of pristine carboxylates with aryl bromides. At a cathode, a NiII(Ar)(Br) intermediate is formed through the activation of Ar-Br bond by a NiI-bipyridine catalyst and subsequent reduction. At an anode, the carboxylates, including amino acid, benzyl carboxylic acid, and 2-phenoxy propionic acid, undergo oxidative decarboxylation to form carbon-based free radicals. The combination of NiII(Ar)(Br) intermediate and carbon radical results in the formation of C(sp3)-C(sp2) cross-coupling products. The adaptation of this electrosynthesis method to flow synthesis and valuable molecule synthesis was demonstrated. The reaction mechanism was systematically studied through electrochemical voltammetry and density functional theory (DFT) computational studies. The relationships between the electrochemical properties of carboxylates and the reaction selectivity were revealed. The electro/Ni dual-catalyzed cross-coupling reactions described herein expand the chemical space of paired electrochemical C(sp3)-C(sp2) cross-coupling and represent a promising method for the construction of the C(sp3)-C(sp2) bonds because of the ubiquitous carboxylate nucleophiles and the innate scalability and flexibility of electrochemical flow-synthesis technology.

Electrochemical Sensors and Biosensors for Identification of Viruses: A Critical Review

Due to their life cycle, viruses can disrupt the metabolism of their hosts, causing diseases. If we want to disrupt their life cycle, it is necessary to identify their presence. For this purpose, it is possible to use several molecular-biological and bioanalytical methods. The reference selection was performed based on electronic databases (2020-2023). This review focused on electrochemical methods with high sensitivity and selectivity (53% voltammetry/amperometry, 33% impedance, and 12% other methods) which showed their great potential for detecting various viruses. Moreover, the aforementioned electrochemical methods have considerable potential to be applicable for care-point use as they are portable due to their miniaturizability and fast speed analysis (minutes to hours), and are relatively easy to interpret. A total of 2011 articles were found, of which 86 original papers were subsequently evaluated (the majority of which are focused on human pathogens, whereas articles dealing with plant pathogens are in the minority). Thirty-two species of viruses were included in the evaluation. It was found that most of the examined research studies (77%) used nanotechnological modifications. Other ones performed immunological (52%) or genetic analyses (43%) for virus detection. 5% of the reports used peptides to increase the method's sensitivity. When evaluable, 65% of the research studies had LOD values in the order of ng or nM. The vast majority (79%) of the studies represent proof of concept and possibilities with low application potential and a high need of further research experimental work.

A Novel Bubble-based Microreactor for Enhanced Mass Transfer Dynamics toward Efficient Electrocatalytic Nitrogen Reduction

Electrocatalytic nitrogen reduction reaction (eNRR) is a promising method for sustainable ammonia production. Although the majority of studies on the eNRR are devoted to developing efficient electrocatalysts, it is critical to study the influence of mass transfer because of the poor N2 transfer efficiency. Herein, a novel bubble-based microreactor (BBMR) is proposed that efficiently promotes the mass transfer behavior during the eNRR using microfluidic strategies. The BBMR possesses abundant triphasic interfaces and provides spatial confinement and accurate potential control, ensuring rapid mass transfer dynamics and improved eNRR performance, as confirmed by experimental and simulation studies. The ammonia yield of the reaction over Ag nanoparticles can be enhanced to 31.35 µg h-1 mgcat. -1, which is twice that of the H-cell. Excellent improvements are also achieved using Ru/C and Fe/g-CN catalysts, with 5.0 and 8.5 times increase in ammonia yield, respectively. This work further demonstrates the significant effect of mass transfer on the eNRR performance and provides an effective strategy for process enhancement through electrode design.

Electrochemical hydrogenation and oxidation of organic species involving water

Fossil fuel-driven thermochemical hydrogenation and oxidation using high-pressure H2 and O2 are still popular but energy-intensive CO2-emitting processes. At present, developing renewable energy-powered electrochemical technologies, especially those using clean, safe and easy-to-handle reducing agents and oxidants for organic hydrogenation and oxidation reactions, is urgently needed. Water is an ideal carrier of hydrogen and oxygen. Electrochemistry provides a powerful route to drive water splitting under ambient conditions. Thus, electrochemical hydrogenation and oxidation transformations involving water as the hydrogen source and oxidant, respectively, have been developed to be mild and efficient tools to synthesize organic hydrogenated and oxidized products. In this Review, we highlight the advances in water-participating electrochemical hydrogenation and oxidation reactions of representative organic molecules. Typical electrode materials, performance metrics and key characterization techniques are firstly introduced. General electrocatalyst design principles and controlling the microenvironment for promoting hydrogenation and oxygenation reactions involving water are summarized. Furthermore, paired hydrogenation and oxidation reactions are briefly introduced before finally discussing the challenges and future opportunities of this research field.

Unlocking the Potential of Oxidative Asymmetric Catalysis with Continuous Flow Electrochemistry

In the field of catalytic asymmetric synthesis, the less-treated path lies in oxidative catalytic asymmetric transformations. The hurdles of pinpointing the appropriate chemical oxidants and addressing their compatibility issues with catalysts and functionalities present significant challenges. Organic electrochemistry, employing traceless electrons for redox reactions, is underscored as a promising solution. However, the commonly used electrolysis in batch cells introduces its own set of challenges, hindering the advancement of electrochemical asymmetric catalysis. Here we introduce a microfluidic electrochemistry platform with single-pass continuous flow reactors that exhibits a wide-ranging applicability to various oxidative asymmetric catalytic transformations. This is exemplified through the sulfenylation of 1,3-dicarbonyls, dehydrogenative C-C coupling, and dehydrogenative alkene annulation processes. The unique properties of microfluidic electrochemical reactors not only eliminate the need for chemical oxidants but also enhance reaction efficiency and reduce the use of additives and electrolytes. These salient features of microfluidic electrochemistry expedite the discovery and development of oxidative asymmetric transformations. In addition, the continuous production facilitated by parallel single-pass reactors ensures straightforward reaction upscaling, removing the necessity for reoptimization across various scales, as evidenced by direct translation from milligram screening to hectogram asymmetric synthesis.

Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

Due to their ease of preparation, stability, and diverse reactivity, N-hydroxyphthalimide (NHPI) esters have found many applications as radical precursors. Mechanistically, NHPI esters undergo a reductive decarboxylative fragmentation to provide a substrate radical capable of engaging in diverse transformations. Their reduction via single-electron transfer (SET) can occur under thermal, photochemical, or electrochemical conditions and can be influenced by a number of factors, including the nature of the electron donor, the use of Brønsted and Lewis acids, and the possibility of forming charge-transfer complexes. Such versatility creates many opportunities to influence the reaction conditions, providing a number of parameters with which to control reactivity. In this perspective, we provide an overview of the different mechanisms for radical reactions involving NHPI esters, with an emphasis on recent applications in radical additions, cyclizations and decarboxylative cross-coupling reactions. Within these reaction classes, we discuss the utility of the NHPI esters, with an eye towards their continued development in complexity-generating transformations.

Microfluidic Platforms for Real-Time In Situ Monitoring of Biomarkers for Cellular Processes

Cellular processes are mechanisms carried out at the cellular level that are aimed at guaranteeing the stability of the organism they comprise. The investigation of cellular processes is key to understanding cell fate, understanding pathogenic mechanisms, and developing new therapeutic technologies. Microfluidic platforms are thought to be the most powerful tools among all methodologies for investigating cellular processes because they can integrate almost all types of the existing intracellular and extracellular biomarker-sensing methods and observation approaches for cell behavior, combined with precisely controlled cell culture, manipulation, stimulation, and analysis. Most importantly, microfluidic platforms can realize real-time in situ detection of secreted proteins, exosomes, and other biomarkers produced during cell physiological processes, thereby providing the possibility to draw the whole picture for a cellular process. Owing to their advantages of high throughput, low sample consumption, and precise cell control, microfluidic platforms with real-time in situ monitoring characteristics are widely being used in cell analysis, disease diagnosis, pharmaceutical research, and biological production. This review focuses on the basic concepts, recent progress, and application prospects of microfluidic platforms for real-time in situ monitoring of biomarkers in cellular processes.

Transition-Metal-Free, Reductive Csp2-Csp3 Bond Constructions via Electrochemically Induced Alkyl Radicals

Construction of the Csp2-Csp3 bond without the aid of transition metal catalysts has been achieved by coupling the electrogenerated alkyl radicals with electron deficient (hetero)arenes in an undivided cell. Simultaneous cathodic reduction of both unactivated alkyl halides and cyanobenzenes under high potential enables radical-radical cross-coupling to deliver alkylarenes in the absence of transition metals. Depending on the coupling partner, the electrogenerated alkyl radicals can also proceed the Minisci-type reaction with N-heteroarenes without redox agents.

Asymmetric Paired Electrocatalysis: Enantioselective Olefin-Sulfonylimine Coupling

Asymmetric electrocatalysis offers exciting new strategies for the synthesis of chiral molecules through novel reaction pathways. However, simultaneous activation of reactants on both electrodes via asymmetric paired electrolysis, which is more energy efficient and economic than single half-electrode synthesis, remains a formidable challenge. Herein, an asymmetric olefin-sulfonylimine coupling via paired electrocatalysis is presented for the first time. In this protocol, Co-catalyzed hydrogen atom transfer on the anode and Ni-catalyzed sulfonylimine reduction on the cathode were seamlessly cross-coupled. The new catalytic system enables the formation of chiral amine products bearing a tetrasubstituted carbon stereocenter with a high enantioselectivity (up to 96% ee).

Towards Industrially Important Applications of Enhanced Organic Reactions by Microfluidic Systems

This review presents a comprehensive evaluation for the manufacture of organic molecules via efficient microfluidic synthesis. Microfluidic systems provide considerably higher control over the growth, nucleation, and reaction conditions compared with traditional large-scale synthetic methods. Microfluidic synthesis has become a crucial technique for the quick, affordable, and efficient manufacture of organic and organometallic compounds with complicated characteristics and functions. Therefore, a unique, straightforward flow synthetic methodology can be developed to conduct organic syntheses and improve their efficiency.

Direct C(sp3)-H Arylation of Unprotected Benzyl Anilines and Alkylarenes by Organocatalysis under Visible Light

Reported herein is direct C(sp3)-H arylation of unprotected benzyl anilines and alkylarenes via consecutive photoinduced electron transfer by visible light irradiation. Reductive quenching cycles and radical-radical cross-coupling were involved, and electron paramagnetic resonance experiments provide evidence for the formation of radical intermediates formed in situ. The protocol highlights transition metal free, external oxidant free, broad substrate scope, and high efficiency (>60 examples, up to 96%).

Paired Electrolysis Enabled Trifluoromethylheteroaromatization of Alkenes and Alkyne with Trifluoromethyl Thianthrenium Triflate (TT-CF3+OTf-) as a Bifunctional Reagent

We report a strategic exploitation of trifluoromethyl thianthrenium triflate (TT-CF3+OTf-) as both electromediator and CF3 radical precursors for paired electrolysis. Enabled by this strategy, the three-component trifluoromethylheteroaromatization of alkenes and alkynes was realized. The superiority of TT-CF3+OTf- to other electrophilic CF3 reagents is attributed to the cathodic generation of thianthrene (TT) as a mediator, which shifts the heterogeneous oxidation of interest to a homogeneous one.

Electrochemically Driven C4-Selective Decyanoalkylation of Cyanopyridines with Unactivated Alkyl Bromides Enabling C(sp3)-C(sp2) Coupling

With cyanopyridines and alkyl bromides as coupling partners, an electrochemically driven C4-selective decyanoalkylation has been established to access diverse 4-alkylpyridines in one step. The reaction proceeds through the single electron reduction/radical-radical coupling tandem process under mild electrolytic conditions, achieving the cleavage of the C(sp2)-CN bond and the formation of C(sp3)-C(sp2). The practicality of this protocol is illustrated by no sacrificial anodes, a broad substrate scope, and gram-scale synthesis.

Photoinduced α-Aminoalkylation of Sulfonylarenes with Alkylamines

α-Aminoalkylation of sulfonylarenes with alkylamines was found to be induced by photoirradiation. Here various types of alkylamines, such as trialkylamines, dialkylamines, N,N-dialkylanilines and N-alkylanilines as well as sulfonylarenes containing an azole, azine, heterole or benzene ring are available. The reaction proceeds through a homolytic aromatic substitution (HAS) process consisting of addition of an α-aminoalkyl radical to a sulfonylarene and elimination of the sulfonyl radical to give the α-arylalkylamine, where photoirradiation is considered to induce homolysis of sulfonylarenes leading to the generation of α-aminoalkyl radicals that make a radical chain operative.

Substrate-Mediator Duality of 1,4-Dicyanobenzene in Electrochemical C(sp2 )-C(sp3 ) Bond Formation with Alkyl Bromides

Electrochemical approaches to form C(sp2 )-C(sp3 ) bonds have focused on coupling C(sp3 ) electrophiles that form stabilized carbon-centered radicals upon reduction or oxidation. Whereas alkyl bromides are desirable C(sp3 ) coupling partners owing to their availability and cost-effectiveness, their tendency to undergo radical-radical homocoupling makes them challenging substrates for electroreductive cross-coupling. Herein, we disclose a metal-free regioselective cross-coupling of 1,4-dicyanobenzene, a useful precursor to aromatic nitriles, and alkyl bromides. Alkyl bromide reduction is mediated directly by 1,4-dicyanobenzene radical anions, leading to negligible homocoupling and high cross-selectivity to form 1,4-alkyl cyanobenzenes. The cross-coupling scheme is compatible with oxidatively sensitive and acidic functional groups such as amines and alcohols, which have proven difficult to incorporate in alternative electrochemical approaches using carboxylic acids as C(sp3 ) precursors.

Selective C(sp3)-H arylation/alkylation of alkanes enabled by paired electrocatalysis

We report a combination of electrocatalysis and photoredox catalysis to perform selective C(sp3)-H arylation/alkylation of alkanes, in which a binary catalytic system based on earth-abundant iron and nickel is applied. Reaction selectivity between two-component C(sp3)-H arylation and three-component C(sp3)-H alkylation is tuned by modulating the applied current and light source. Importantly, an ultra-low anodic potential (~0.23 V vs. Ag/AgCl) is applied in this protocol, thus enabling compatibility with a variety of functional groups (>70 examples). The robustness of the method is further demonstrated on a preparative scale and applied to late-stage diversification of natural products and pharmaceutical derivatives.

Mechanistic studies of Ni-catalyzed electrochemical homo-coupling reactions of aryl halides

Ni-catalyzed electrochemical arylation is an attractive, emerging approach for molecular construction as it uses air-stable Ni catalysts and efficiently proceeds at room temperature. However, the homo-coupling of aryl halide substrates is one of the major side reactions. Herein, extensive experimental and computational studies were conducted to examine the mechanism of Ni-catalyzed electrochemical homo-coupling of aryl halides. The results indicate that an unstable NiII(Ar)Br intermediate formed through oxidative addition of the cathodically generated NiI species with aryl bromide and a consecutive chemical reduction step. For electron-rich aryl halides, homo-coupling reaction efficiency is limited by the oxidative addition step, which can be improved by negatively shifting the redox potential of the Ni-catalyst. DFT computational studies suggest a NiIII(Ar)Br2/NiII(Ar)Br ligand exchange pathway for the formation of a high-valent NiIII(Ar)2Br intermediate for reductive elimination and production of the biaryl product. This work reveals the reaction mechanism of Ni-catalyzed electrochemical homo-coupling of aryl halides, which may provide valuable information for developing cross-coupling reactions with high selectivity.

A Paradigm Shift in Catalysis: Electro- and Photomediated Nickel-Catalyzed Cross-Coupling Reactions

ConspectusTransition-metal catalyzed cross-coupling reactions are fundamental reactions in organic chemistry, facilitating strategic bond formations for accessing natural products, organic materials, agrochemicals, and pharmaceuticals. Redox chemistry enables access to elusive cross-coupling mechanisms through single-electron processes as an alternative to classical two-electron strategies predominated by palladium catalysis. The seminal reports of Baran, MacMillan, Doyle, Molander, Weix, Lin, Fu, Reisman, and others in merging redox perturbation (photochemical, electrochemical, and purely chemical) with catalysis are pivotal to the current resurgence and mechanistic understanding of first-row transition metal-based catalysis. The hallmark of this redox platform is the systematic modulation of transition-metal oxidation states by a photoredox catalyst or at a heterogeneous electrode surface. Electrocatalysis and photocatalysis enhance transition metal catalysis' capacity for bond formation through electron- or energy-transfer processes that promote otherwise challenging elementary steps or elusive mechanisms. Cross-coupling conditions promoted by electrocatalysis and photocatalysis are mild, and bond formation proceeds with exceptionally high chemoselectivity and wide functional group tolerance. The interfacing of abundant first-row transition-metal catalysis with electrocatalysis and photocatalysis has brought about a paradigm shift in cross-coupling technology as practitioners are quickly applying these tools in synthesizing fine chemicals and pharmaceutically relevant motifs. In particular, the merger of Ni catalysis with electro- and photochemistry ushered in a new era for carbon-carbon and carbon-heteroatom cross-couplings with expanded generality compared to their thermally driven counterparts. Over the past decade, we have developed enabling photo- and electrochemical methods throughout our combined research experience in industry (BMS, AstraZeneca) and academia (Professor Baran, Scripps Research) in cross-disciplinary collaborative environments. In this Account, we will outline recent progress from our past and present laboratories in photo- and electrochemically mediated Ni-catalyzed cross-couplings. By highlighting these cross-coupling methodologies, we will also compare mechanistic features of both electro- and photochemical strategies for forging C(sp2)-C(sp3), C(sp3)-C(sp3), C-O, C-N, and C-S bonds. Through these side-by-side comparisons, we hope to demystify the subtle differences between the two complementary tools to enact redox control over transition metal catalysis. Finally, building off the collective experience of ourselves and the rest of the community, we propose a tactical user guide to photo- and electrochemically driven cross-coupling reactions to aid the practitioner in rapidly applying such tools in their synthetic designs.

Modulating Charge Transfer Pathways to Enhance Photocatalytic Performance of the Metal-Organic Layer Nanosheet

Two-dimensional metal-organic layer (MOL) nanosheets, as nonhomogeneous catalysts, show better optical activity in the field of photocatalysis due to their unique structural advantages. Current research focuses on how to modify the structure of 2D nanosheets by means of crystal engineering to modulate the intralayer electron transfer pathway and systematically investigate the impacts of size effect and electron transfer pathway on the energy utilization efficiency of crystalline materials. In the present work, a triple lophine-derived ligand was designed and prepared, which exhibits a large π-conjugation system and multiple D-A (D: donor, A: acceptor) electron transfer pathways. 2D MOL constructed with Cd ions can be exfoliated by physical sonication to obtain double-walled 2D MOL nanosheets. Compared with the bulk crystalline material, the 2D nanosheets exhibit better photovoltaic properties. Benefiting from the excellent structural advantages, 2D MOL nanosheets could be used as photocatalysts for a variety of aerobic oxidation reactions under mild conditions (10 W white LED, room temperature), such as the trifluoromethylation of coumarins, the synthesis of benzimidazole derivatives from aromatic diamines and aromatic aldehydes, and the preparation of 2,4,6-triarylpyridine derivatives, all with high conversion rates and selectivity (yield typically greater than 88%). The related results illustrate that the introduction of the photoactive triple-lophine unit into 2D MOL nanosheets can effectively modulate the electron transport mode and enhance energy utilization, which provides a new research idea for the development of nonhomogeneous photocatalysts aimed at the applications of visible light-driven organic conversion.

Electrochemical Late-Stage Functionalization

Late-stage functionalization (LSF) constitutes a powerful strategy for the assembly or diversification of novel molecular entities with improved physicochemical or biological activities. LSF can thus greatly accelerate the development of medicinally relevant compounds, crop protecting agents, and functional materials. Electrochemical molecular synthesis has emerged as an environmentally friendly platform for the transformation of organic compounds. Over the past decade, electrochemical late-stage functionalization (eLSF) has gained major momentum, which is summarized herein up to February 2023.

Electrochemical Post-Ugi Cyclization for the Synthesis of Highly Functionalized Spirolactams

The combination of the Ugi reaction and electro-organic synthesis can aid in the creation of novel heterocycles that have not been previously explored. In this study, a new strategy utilizing bis-amides from the Ugi reaction has been developed, which can produce C-S, C-Se, and C-C═O functionalized five-membered spirolactams mediated by electricity under catalyst- and metal-free conditions. Notably, this approach can be applied using a microelectro-flow reactor (μ-EFR) for gram-scale synthesis. The described strategy can synthesize complex azaspiro-fused tricyclic scaffolds with high diastereo- and regioselectivity, highlighting its versatility and potential.

Microfluidic Aqueous Two-Phase Focusing of Chemical Species for In Situ Subcellular Stimulation

Confinement of chemical species in a controllable micrometer-level (several to a dozen micrometers) space in an aqueous environment is essential for precisely manipulating chemical events in subcellular regions. However, rapid diffusion and hard-to-control micrometer-level fluids make it a tough challenge. Here, a versatile open microfluidic method based on an aqueous two-phase system (ATPS) is developed to restrict species inside an open space with micron-level width. Unequal standard chemical potentials of the chemical species in two phases and space-time correspondence in the microfluidic system prevent outward diffusion across the phase interface, retaining the target species inside its preferred phase flow and creating a sharp boundary with a dramatic concentration change. Then, the chemical flow (the preferred phase with target chemical species) is precisely manipulated by a microfluidic probe, which can be compressed to a micron-level width and aimed at an arbitrary position of the sample. As a demonstration of the feasibility and versatility of the strategy, chemical flow is successfully applied to subcellular regions of various kinds of living single cells. Subcellular regions are successfully labeled (cytomembrane and mitochondria) and damaged. Healing-regeneration behaviors of living single cells are triggered by subcellular damage and analyzed. The method is relatively general regarding the species of chemicals and biosamples, which could promote deeper cell research.

Electrochemical Direct α-Arylation of Alkylamines with Sulfonylarenes

The electrochemical α-arylation of alkylamines with sulfonylarenes has been developed. Here, diverse trialkylamines and aryl(dimethyl)amines are applicable to the α-arylation with sulfonylarenes having an azole, azine, and benzene nucleus. The α-arylation was scaled up using an electrolysis flow cell. Mechanistic studies show that anodic oxidation of an alkylamine with a sulfinate as a mediator followed by deprotonation gives an α-aminoalkyl radical, which undergoes homolytic aromatic substitution (HAS) on a sulfonylarene to give the corresponding α-arylalkylamine.

Scalable electrosynthesis of commodity chemicals from biomass by suppressing non-Faradaic transformations

Electrooxidation of biomass platforms provides a sustainable route to produce valuable oxygenates, but the practical implementation is hampered by the severe carbon loss stemming from inherent instability of substrates and/or intermediates in alkaline electrolyte, especially under high concentration. Herein, based on the understanding of non-Faradaic degradation, we develop a single-pass continuous flow reactor (SPCFR) system with high ratio of electrode-area/electrolyte-volume, short duration time of substrates in the reactor, and separate feeding of substrate and alkaline solution, thus largely suppressing non-Faradaic degradation. By constructing a nine-stacked-modules SPCFR system, we achieve electrooxidation of glucose-to-formate and 5-hydroxymethylfurfural (HMF)-to-2,5-furandicarboxylic acid (FDCA) with high single-pass conversion efficiency (SPCE; 81.8% and 95.8%, respectively) and high selectivity (formate: 76.5%, FDCA: 96.9%) at high concentrations (formate: 562.8 mM, FDCA: 556.9 mM). Furthermore, we demonstrate continuous and kilogram-scale electrosynthesis of potassium diformate (0.7 kg) from wood and soybean oil, and FDCA (1.17 kg) from HMF. This work highlights the importance of understanding and suppressing non-Faradaic degradation, providing opportunities for scalable biomass upgrading using electrochemical technology.

Defluorinative Thiolation of gem-Difluoroalkenes by Convergent Paired Electrolysis

Herein, we have successfully developed a convergent paired electrolysis strategy for the defluorinative thiolation process utilizing thiols and gem-difluoroalkenes as precursors. This protocol exhibits remarkable tolerance toward a wide range of functional groups, as exemplified by the successful late-stage defluorothiolation of complex molecules. Additionally, this strategy is amenable to gram-scale synthesis, making use of both anodic oxidation and cathodic reduction processes in an efficient manner. Several control studies were conducted and suggested a convergent paired electrolysis mechanism.

A field guide to flow chemistry for synthetic organic chemists

Flow chemistry has unlocked a world of possibilities for the synthetic community, but the idea that it is a mysterious "black box" needs to go. In this review, we show that several of the benefits of microreactor technology can be exploited to push the boundaries in organic synthesis and to unleash unique reactivity and selectivity. By "lifting the veil" on some of the governing principles behind the observed trends, we hope that this review will serve as a useful field guide for those interested in diving into flow chemistry.