Two-Phase Electrochemical Generation of Aryldiazonium Salts: Application in Electrogenerated Copper-Catalyzed Sandmeyer Reactions

Successive paired electrochemical late-stage modification of niclosamide a common anthelmintic drug. A green protocol for the synthesis of new drug-like molecules

Drugs based on salicylanilides such as niclosamide are of particular interest to medicinal chemistry researchers. They exhibit a wide range of biological activities, including anticancer and antiviral activities. Niclosamide is a common oral anthelmintic that has the potential to be an antiviral and anticancer drug. However, two characteristics of it, including poor oral bioavailability and high cytotoxicity, have limited its use. The synthesis of new niclosamide analogs is an attempt to overcome these limitations. The electrochemical behavior of niclosamide shows that the drug can be reduced and then oxidized at the cathode and anode, respectively. This property, along with the special capabilities of electrosynthesis methods, makes it possible to obtain unique niclosamide analogs. In this study, novel niclosamide analogs were synthesized via successive paired electrolysis of niclosamide in the presence of arylsulfinic acids as nucleophiles. The results show that niclosamide is converted to the desired product (5-chloro-N-(2-chloro-4-(phenylsulfonamido)phenyl)-2-hydroxy benzamide) after reduction and oxidation steps and reaction with the nucleophile. In the synthesized niclosamide analogs, a sulfonamide moiety is attached to the drug molecule. This work presents a green method for the synthesis of new niclosamide analogs without the need for catalysts, reductants or oxidants under mild conditions in a one-pot process.

Cathodic Deoxygenative Alkylation of Nitro(hetero)arenes with Organic Halides

We have realized a cathodic deoxygenative alkylation between nitro(hetero)arenes and organic halides, employing bis(pinacolato)diboron (B2pin2) and LiCl as additives to trap and stabilize the generated alkyl radicals and carbanions, thereby facilitating efficient N-O cleavage and selective C-N bond formation. The protocol offers an economical method for the efficient synthesis of multiple aromatic(hetero) amines, without the need for reactive reductants and the exclusion of air and moisture. Notably, the protocol is distinguished by scalability, broad functional group compatibility, and safe and mild conditions, demonstrating practicality in the synthesis and late-stage modification of various bioactive compounds.

The Strategies Towards Electrochemical Generation of Aryl Radicals

The advancement in electrochemical techniques has unlocked a new path for achieving unprecedented oxidations and reductions of aryl radical precursors in a controlled and selective manner. This approach facilitates the construction of aromatic carbon-carbon and carbon-heteroatom bonds. In light of the green merits and the growing importance of this technique in aryl radical chemistry, this review aims to provide an overview of the recent advance in the electrochemical generation of aryl radicals organized by the aryl radical precursor type, with a focus on the substrate scope, limitation, and underlying mechanism, thereby inspiring future work on electrochemical aryl radical generation.

A new type of convergent paired electrochemical synthesis of sulfonamides under green and catalyst-free conditions

Our main goal in this work is to synthesize valuable sulfonamide compounds according to the principles of green chemistry and also to present a unique convergent paired mechanism for their synthesis. In this study, we introduced a new type of convergent paired electro-organic synthesis of sulfonamide derivatives via a catalyst, oxidant, halogen and amine-free method. In this research, instead of using toxic amine compounds, an innovative mechanism based on the reduction of nitro compounds and in-situ production of amine compounds was used. The mechanism of electrophile generation is the cathodic reduction of the nitro compound to the hydroxylamine compound and then the anodic oxidation of the hydroxylamine to the nitroso compound. On the other hand, the nucleophile generation mechanism involves the two-electron oxidation of sulfonyl hydrazide to related sulfinic acid at the anode surface. The reaction leading to the synthesis of sulfonamides involves a one-pot reaction of the generated nitroso compound with the produced sulfinic compound.

A green protocol for the electrochemical synthesis of a fluorescent dye with antibacterial activity from imipramine oxidation

Electrochemical oxidation of imipramine (IMP) has been studied in aqueous solutions by cyclic voltammetry and controlled-potential coulometry techniques. Our voltammetric results show a complex behavior for oxidation of IMP at different pH values. In this study, we focused our attention on the electrochemical oxidation of IMP at a pH of about 5. Under these conditions, our results show that the oxidation of IMP leads to the formation of a unique dimer of IMP (DIMP). The structure of synthesized dimer is fully characterized by UV-visible, FTIR, ¹H NMR, ¹³C NMR and mass spectrometry techniques. It seems that the first step in the oxidation of IMP is the cleavage of the alkyl group (formation of IMPH). After this, a domino oxidation-hydroxylation-dimerization-oxidation reaction, converts IMPH to (E)-10,10',11,11'-tetrahydro-[2,2'-bidibenzo[b,f]azepinylidene]-1,1'(5H,5'H)-dione (DIMP). The synthesis of DIMP is performed in an aqueous solution under mild conditions, without the need for any catalyst or oxidant. Based on our electrochemical findings as well as the identification of the final product, a possible reaction mechanism for IMP oxidation has been proposed. Conjugated double bonds in the DIMP structure cause the compound to become colored with sufficient fluorescence activity (excitation wave-length 535 nm and emission wave-length 625 nm). Moreover, DIMP has been evaluated for in vitro antibacterial. The antibacterial tests indicated that DIMP showed good antibacterial performance against all examined gram-positive and gram-negative bacteria (Staphylococcus aureus, Bacillus cereus, Escherichia coli and Shigella sonnei).

New insight into the electrochemical reduction of different aryldiazonium salts in aqueous solutions

Electrochemical reduction of different aryldiazonium salts in aqueous solution was studied in this work and it is shown that the aryldiazonium salts are converted to the corresponding aryl radical and aryl anion. The results of this research indicate that the reduction of aryldiazonium salts takes place in two single-electron steps. Our data show that when the substituted group on the phenyl ring is H, Cl, OH, NO₂, OCH₃ or SO₃⁻, the corresponding diazonium salt shows poor adsorption characteristics, but when the substituted group is methyl, the corresponding diazonium salt shows strong adsorption characteristics. In the latter case, the voltammogram exhibits three cathodic peaks. In addition, the effect of various substitutions on the aryldiazonium reduction was studied by Hammett's method. The data are show that with increasing electron withdrawing capacity of the substituent, the reduction of corresponding diazonium salt becomes easier.

Electrochemical reduction of different aryldiazonium salts in aqueous solution was studied. It is shown that the aryldiazonium salts are converted to the corresponding aryl radical and aryl anion.