Mechanistic Aspects of the Electrochemical Oxidation of Aliphatic Amines and Aniline Derivatives

Electrochemically-Driven 1,4-Aryl Migration via Radical Fluoromethylation of N-Allylbenzamides: a Straightforward Access to Functionalized β-Arylethylamines

An electrochemical radical Truce Smiles rearrangement of N-allylbenzamides is documented herein. The selective 1,4-aryl migration was triggered by the radical fluoromethylation of the alkene providing a direct route to fluoro derivatives of the highly privileged β-arylethylamine pharmacophore. This practical transformation utilizes readily available starting materials and employs an electrical current to drive the oxidative process under mild reaction conditions. It accommodates a variety of migratory aryl groups with different electronic properties and substitution patterns. Careful selection of the protecting group on the nitrogen atom of the N-allylbenzamide is crucial to outcompete the undesired 6-endo cyclization and achieve high level of selectivity towards the 1,4-aryl migration. DFT calculations support the reaction mechanism and unveil the origin of selectivity between the two competitive pathways.

Visible light mediated iron-catalyzed addition of oxamic acids to imines

Oxamic acids where shown to add to imines, providing a broad range of α-aminoacid amides in generally good yields. The process is efficient on pre-formed imines but may also be conducted using a 3-component strategy by simply mixing aldehydes, amines and oxamic acids in the presence of ferrocene, acting both as a photocatalyst under visible light and as a Lewis acid. The reaction proceeds through the addition onto the imine of a carbamoyl radical intermediate generated through a charge transfer from the carboxylate ligand to a Fe(iii) species (LMCT).

Electrochemical Multicomponent Synthesis of Alkyl Alkenesulfonates using Styrenes, SO2 and Alcohols

A novel electrochemical approach to access alkyl alkenesulfonates via a multicomponent reaction was developed. The metal-free method features easy-to-use SO2 stock solution forming monoalkylsulfites from alcohols with an auxiliary base in-situ. These intermediates serve a dual role as starting materials and as supporting electrolyte enabling conductivity. Anodic oxidation of the substrate styrene, radical addition of these monoalkylsulfites and consecutive second oxidation and deprotonation preserve the double bond and form alkyl β-styrenesulfonates in a highly regio- and stereoselective fashion. The feasibility of this electrosynthetic method is demonstrated in 44 examples with yields up to 81 %, employing various styrenes and related substrates as well as a diverse set of alcohols. A gram-scale experiment underlines the applicability of this process, which uses inexpensive and readily available electrode materials.

Calibration-free electrochemical sensor to monitor factor-Xa inhibitors at the point-of-care anticoagulation therapy

This article presents a novel proof of concept for the blood plasma quantification of clinically relevant concentrations of direct oral anticoagulants, DOACs, including rivaroxaban and edoxaban, as well as low-molecular-weight heparins, LMWHs, such as enoxaparin and dalteparin, utilising a calibration-free disposable electrochemical sensor with co-facing electrodes. A dose-response curve was generated for rivaroxaban and edoxaban to demonstrate the sensor's ability to detect ≥9.00 ng mL-1 rivaroxaban and quantify it in the 11.0-140 ng mL-1 range. Similarly, the lower detection limit for edoxaban was 12.9 ng mL-1, with a quantification range of 16.8-140 ng mL-1. The significance of this sensor lies in its ability to quantify rivaroxaban and edoxaban below 30 ng mL-1, which is crucial in emergency care centres when patients undergoing DOAC therapy require emergency surgery or reversal of DOACs due to bleeding or ischemic stroke. Furthermore, the sensor can detect ≥0.016 IU mL-1 enoxaparin and ≥0.013 IU mL-1 dalteparin and quantify them in the 0.025-0.75 and 0.019-0.75 IU mL-1 range, respectively. Additionally, a dose-response curve was presented to demonstrate the potential ability of this sensor to quantify factor-Xa inhibitors independently of which DOACs or LMWHs are used. With the assay completed in less than 30 s using a minimal volume of 7 μL sample, the possibility to work at physiological pH and under calibration-free format makes this assay an excellent candidate for point-of-care testing.

Novel disposable and portable 3D-printed electrochemical apparatus for fast and selective screening of 25E-NBOH in forensic samples

The advent of new psychoactive substances (NPS) has caused enormous difficulty for legal control since they are rapidly commercialized, and their chemical structures are routinely altered. In this aspect, derivatives phenethylamines, such as 25E-NBOH, have received great attention in the forensic scenario. Hence, we propose portable and cost-effective (U$ 5.00) 3D-printed devices for the electrochemical screening of 25E-NBOH for the first time. The cell and all electrodes were printed using acrylonitrile butadiene styrene filament (insulating material) and conductive filament (graphite embedded in a polylactic acid matrix), respectively, both by the fused deposition modeling (FDM) 3D printing technique. The electrochemical apparatus enables micro-volume analysis (50-2000 μL), especially important for low sample volumes. A mechanistic route for the electrochemical oxidation of 25E-NBOH is proposed based on cyclic voltammetric data, which showed two oxidation processes around +0.75 V and +1.00 V and a redox pair between +0.2 and -0.2 V (vs. graphite ink pseudo-reference). A fast and sensitive square-wave voltammetry method was developed, which exhibited a linear working range from 0.85 to 5.1 μmoL-1, detection limit of 0.2 μmol L-1, and good intra-electrode precision (n = 10, RSD <5.3 %). Inter-electrode measurements (n = 3, RSD <9.8 %) also attested that the electrode production process is reproducible. Interference tests in the presence of other drugs frequently found in blotting paper indicated high selectivity of the electrochemical method for screening of 25E-NBOH. Screening analysis of blotting paper confirmed the presence of 25E-NBOH in the seized samples. Moreover, a recovery percentage close to 100 % was found for a spiked saliva sample, suggesting the method's usefulness for quantitative purposes aimed at information on recent drug use.

Bromine-mediated strategy endows efficient electrochemical oxidation of amine to nitrile

Conventional methods for nitrile synthesis bring inherent environmental risks due to their reliance on oxidants and harsh reaction conditions. Meanwhile, direct electrooxidation of amines to nitriles suffers from low current density. In this study, we propose an innovative indirect electrooxidation strategy for nitrile formation, mediated by Br-/Br2, utilizing a highly efficient CoS2/CoS@Graphite Felt (GF) electrode. Notably, the anodic nitrile generation can be synergistically coupled with the cathodic hydrogen evolution reaction (HER). Through meticulous optimization of reaction parameters, we achieve an impressive 98% selectivity for octanenitrile at a current density of 60 mA cm-2 with a remarkable faradaic efficiency (FE) of 87%. Furthermore, our approach demonstrates excellent versatility, as we successfully evaluate both aliphatic and aromatic primary amines, highlighting its promising potential for practical applications in the field.

Design, Synthesis, and Mechanism of Novel 9-Aliphatic Amine Tryptanthrin Derivatives against Phytopathogenic Bacteria

Taking inspiration from the use of natural product-derived bactericide candidates in drug discovery, a series of novel 9-aliphatic amine tryptanthrin derivatives were designed, synthesized, and evaluated for their biological activity against three plant bacteria. The majority of these compounds exhibited excellent antibacterial activity in vitro. Compound 7c exhibited a significantly superior bacteriostatic effect against Xanthomonas axonopodis pv Citri (Xac), Xanthomonas oryzae pv Oryzae (Xoo), and Pseudomonas syringae pv Actinidiae (Psa) with final corrected EC50 values of 0.769, 1.29, and 15.5 μg/mL, respectively, compared to the commercial pesticide thiodiazole copper which had EC50 values of 58.8, 70.9, and 91.9 μg/mL. Preliminary mechanism studies have demonstrated that 7c is capable of altering bacterial morphology, inducing reactive oxygen species accumulation, promoting bacterial cell apoptosis, inhibiting normal cell growth, and affecting cell membrane permeability. Moreover, in vivo experiments have substantiated the effectiveness of 7c as a therapeutic and defensive agent against the citrus canker. The proteomic analysis has unveiled that the major disparities are located within the bacterial secretion system pathway, which hinders membrane transportation. These discoveries imply that 7c could be an auspicious prototype for developing antiphytopathogenic bacterial agents.

LQFM289: Electrochemical and Computational Studies of a New Trimetozine Analogue for Anxiety Treatment

This study employs electrochemical and Density Functional Theory (DFT) calculation approaches to investigate the potential of a novel analogue of trimetozine (TMZ) antioxidant profile. The correlation between oxidative stress and psychological disorders indicates that antioxidants may be an effective alternative treatment option. Butylatedhydroxytoluene (BHT) is a synthetic antioxidant widely used in industry. The BHT-TMZ compound derived from molecular hybridization, known as LQFM289, has shown promising results in early trials, and this study aims to elucidate its electrochemical properties to further support its potential as a therapeutic agent. The electrochemical behavior of LQFM289 was investigated using voltammetry and a mechanism for the redox process was proposed based on the compound's behavior. LQFM289 exhibits two distinct oxidation peaks: the first peak, Ep1a ≈ 0.49, corresponds to the oxidation of the phenolic fraction (BHT), and the second peak, Ep2a ≈ 1.2 V (vs. Ag/AgCl/KClsat), denotes the oxidation of the amino group from morpholine. Electroanalysis was used to identify the redox potentials of the compound, providing insight into its reactivity and stability in different environments. A redox mechanism was proposed based on the resulting peak potentials. The DFT calculation elucidates the electronic structure of LQFM289, resembling the precursors of molecular hybridization (BHT and TMZ), which may also dictate the pharmacophoric performance.

One Material-Opposite Triboelectrification: Molecular Engineering Regulated Triboelectrification on Silica Surface to Enhance TENG Efficiency

Molecular engineering is a unique methodology to take advantage of the electrochemical characteristics of materials that are used in energy-harvesting devices. Particularly in triboelectric nanogenerator (TENG) studies, molecular grafting on dielectric metal oxide surfaces can be regarded as a feasible way to alter the surface charge density that directly affects the charge potential of triboelectric layers. Herein, we develop a feasible methodology to synthesize organic-inorganic hybrid structures with tunable triboelectric features. Different types of self-assembled monolayers (SAMs) with electron-donating and withdrawing groups have been used to modify metal oxide (MO) surfaces and to modify their charge density on the surface. All the synthetic routes for hybrid material production have been clearly shown and the formation of covalent bonds on the MO's surface has been confirmed by XPS. The obtained hybrid structures were applied as dopants to distinct polymer matrices with various ratios and fiberization processes were carried out to the prepare opposite triboelectric layers. The formation of the fibers was analyzed by SEM, while their surface morphology and physicochemical features have been measured by AFM and a drop shape analyzer. The triboelectric charge potential of each layer after doping and their contribution to the TENG device's parameters have been investigated. For each triboelectric layer, the best-performing tribopositive and tribonegative material combination was separately determined and then these opposite layers were used to fabricate TENG with the highest efficiency. A comparison of the device parameters with the reference indicated that the best tribopositive material gave rise to a 40% increase in the output voltage and produced 231 V, whereas the best tribonegative one led to a 33.3% rise in voltage and generated 220 V. In addition, the best device collected ~83% more charge than the reference device and came up with 250 V that corresponds to 51.5% performance enhancement. This approach paved the way by addressing the issue of how molecular engineering can be used to manipulate the triboelectric features of the same materials.