An electrochemical synthesis of tetrasubstituted hydrazines through dehydrogenative dimerization of secondary amines has been developed. The reactions are conducted in a simple undivided cell with constant current. The use of electricity to promote the reactions obviates the need for transition metal catalysts and oxidizing reagents, providing an efficient and sustainable access to tetrasubstituted hydrazines with diverse electronic properties.

The electro-oxidation cyanation of p-methoxybenzyl alcohol (p-MeOC₆H₄CH₂OH) to prepare aryl nitriles was studied by using cyclic voltammetry (CV) and constant current electrolysis (CCE). The effects of the volume ratio of H₂O, concentration of H₂SO₄, temperature, electrode materials, current density and solvents on the electro-chemical reaction were studied. The results showed that the yield of p-methoxylbenzonitrile (p-MeOBN) was 90% in 0.15 mol·L^-1 H₂SO₄ and 30% H₂O-DMSO solution at 60℃ and 10 mA/cm² of current density when tetrabutylammonium perchlorate (Bu₄NClO₄) was used as electrolyte. The CCE of aromatic benzyl alcohols with different p-and o-substituted analogs was investigated under the optimized reaction conditions, and the yields toward formation of the corresponding aryl nitriles were 61%~92%. A plausible mechanism for the electro-oxidation cyanation procedure was proposed. A novel paired electrochemical method for the synthesis of aryl nitriles from aromatic benzyl alcohols with hydroxylamine (HAM) as "N" source and aldehyde in situ in undivided electrochemical cell was successfully developed.

1,3,4-Oxadiazoles, standing for a class of five-membered heterocyclic compounds with multiple heteroatoms, show anti-inflammatory, anti-convulsant, anti-inositol and other biological activities. They also served as important intermediates in organic synthesis. Thus, the development of general and straightforward methods for their synthesis is of great significance. In this paper one-step synthesis of non-symmetric 2,5-disubstituted 1,3,4-oxadiazole derivatives with good yield was completed under electrocatalytic conditions by using cheap and readily available aldehydes and hydrazides as starting materials. Their structures were confirmed by IR, ¹H NMR, ¹³C NMR and HRMS analyses. The reaction features mild conditions, high atom-economy and wide substrate scope, providing a green and sustainable synthetic protocol for constructing 1,3,4-oxadiazole skeleton.

The recent developments in asymmetric organotransition metal-catalyzed electrochemistry (AOMCE) are summarized. AOMCE processes can be divided into oxidative and reductive variants. In terms of oxidations, asymmetric functionalization of olefins, oxidative kinetic resolution of secondary alcohols or aldehydes, and asymmetric C—H functionalization reactions have been developed. Reductive processes discussed include asymmetric electrochemical carboxylation with carbon dioxide, asymmetric electrochemical decarboxylation, and asymmetric reductive coupling reactions. The combination of chiral ligands, transition-metal catalysts, and electrochemistry provides a novel angle by which to address the longstanding fundamental challenge of stereoinduction in traditional electrochemical organic synthesis.

Anodic oxidation of aryl iodine compouds is a green and efficient method for the synthesis of hypervalent iodine reagents. This method replaces chemical reagents with electric current, avoiding the use of expensive and handle difficult oxidants such as m-CPBA, H₂O₂, oxone, selectfluor etc. Electrochemically generated hypervalent iodine reagents can not only promote fluorination, oxidative cyclization, but also be successfully applied in the total synthesis of natural products. In addition, recyclable aryl iodine mediator can be used to indirect anodic fluorination and easily separated from products. The organic electrochemical synthesis of hypervalent iodine reagents and their applications in various chemical transformations are reviewed.

Thiocyanate, as a versatile synthon, which has important application value in many fields such as pharmaceutical, pesticide and materials. The photocatalytic and electrocatalytic thiocyanation reactions have been widely concerned in organic chemistry due to the advantages of green, efficiency and safety. In this review, the cross-coupling/thiocyanation reactions based on the photocatalytic and electrocatalytic are described, which is expected to be helpful in exploring the green synthesis of thiocyanates compounds.

Imidazo[1,2-a]pyridines are a special nitrogen-containing compounds, which play an important role in the fields of pesticides biomedicine, optical and electrical materials. In recent years, the synthesis of functional imidazo[1,2-a]pyridines has become a hot topic for organic scientists and pharmaceutical chemists, and great progress has been made. Among them, the synthesis of functionalized imidazo[1,2-a]pyridines via visible-light catalysis and electrochemistry based on green chemistry has become the powerful tool for the synthesis of these compounds. Based on the types of canbon-hetero bonds of imidazo- [1,2-a]pyridines, the research on the construction of imidazo[1,2-a]pyridines C-3 canbon-hetero bonds by visible-light catalysis and electrochemical synthesis in recent 5 years is summarized.

In modern organic synthesis, C—H functionalization can be used to construct various bioactive skeletons quickly and directly, and increase the complexity of the target molecular structure, which becomes an effective supplement to the traditional methods. Among them, C(sp³)—H functionalization has long been a big challenge in this field. Molecular iodine has been identified as an economically and ecologically harmless transition metal substitute, and tremendous progress has been made in the challenging C(sp³)—H functionalization reaction recently. The molecular iodine-catalyzed C(sp³)—H functionalization reactions under different oxidation systems have different reaction characteristics and mechanisms. The combination of molecular iodine and hypervalent aryl iodanes, dimethyl sulfoxide (DMSO), peroxide and oxygen can efficiently catalyze the functionalization of C(sp³)—H with different mechanisms. Recently, transition-metal/iodine co-cataly- sis and iodine-containing electrochemical catalysis have also made unprecedented progress in C(sp³)—H functionalization reaction. Herein, the progress of C(sp³)—H functionalization catalyzed by iodine under different oxidation systems from 2015 to now is summarized. The research on the green catalytic system of molecular iodine in the C(sp³)—H functionalization reaction is summarized and prospected.

Allyl groups, as a kind of universal protective groups in organic synthesis, are easily introduced, and stable under acidic, basic and reductive conditions. Moreover, the deallylation may occur efficiently and selectively under mild conditions. Therefore, functional group protection with allyl moiety plays a significant role in organic synthesis, especially in the synthesis of natural products and pharmaceutical industry. In recent decades, various methods of deallylation have been developed. Herein, the comprehensive development on the deallylation reaction with base and reductant, oxidation and free radical, Lewis-acid, iodine, transition metals, and electrochemical methods is reviewed.

Nitrogenous heterocyclic compounds are widely found in medicinal molecules, natural products and functional materials. Therefore, it has great significance to develop simple and efficient methods for the construction of these compounds. Recently, remarkable progress has been made in haloids mediated electrochemical synthesis of nitrogen heterocycles. Due to the relatively mild reaction condition and environmental protection, it provides a novel approach to construct nitrogen heterocycles. In this review, the recent developments in this area are summarized.

Fluorine chemistry has been widely used in all walks of life, and the combination of fluorine chemistry and organic chemistry is blooming everywhere. Since the introduction of fluorine atoms or fluorine groups into drugs is of great significance, it is essential to seek an effective fluoroalkylation pathway. With the development of electrochemistry, people combine electrochemistry and fluoroalkylation reaction skillfully. In turn, a safer, more economical, environmentally friendly and efficient fluoroalkylation pathway is obtained. The fluoroalkylation reaction pathway under the guidance of electrochemistry has not only reformed the reaction method, but also has advantages in terms of substrate universality. Fluoroalkylation of unsaturated aliphatic compounds their derivatives and aromatic compounds under electrochemical catalysis has been reported. According to the nature of the substrate and its reaction mechanism, the progress of electrocatalytic fluoroalkylation methods is summarized.

Olefin is an important synthetic synthon, and its concise and efficient transformation has been a research hotspot in the field of organic synthesis. In recent years, the C—S bond formation based on the olefin skeleton has received particular attention from scientists. Alkenes can react with common organic sulfur-containing reagents, including thiol, disulfide, sulfoxide, sulfonyl hydrazide, sulfonyl chloride, sodium sulfinate and other kinds of organosulfur reagents to build C—S bonds at the α-position or β-position of olefin to synthesize sulfide, sulfoxide or sulfone. Thus, according to the different classification of the used organosulfur reagents, the recent research progresses in C—S bond formation reaction of olefins with organic sulfur reagents under photocatalyst-free conditions and non-electrochemical method is summarized. In the future, among the researches on the C—S bond formation reactions of olefins with inexpensive organosulfur reagents, asymmetrical synthesis and various difunctionalizations are still promising directions.

An electrochemical selenylation/cyclization of N-allylthioamides has been developed for the synthesis of selenium-containing 2-thiazolines. This protocol provides an efficient approach to produce 2-thiazolines with broad substrate scope under mild reaction conditions. Preliminary mechanistic study indicates that selenium radical may be involved. The reaction is easy operated under catalyst- and oxidant-free conditions.

Metal-free electrochemical oxidation cyanation and phosphonylation reactions had been developed, in which 2,2,6,6-tetramethylpiperidinyl-N-oxyl (TEMPO) reduced the electrode potential of substrate and avoided over oxidation of some electron rich aromatic amines under electrochemical conditions. This protocol had good functional group compatibility, which made it to be a practical and efficient method to synthesize α-aminonitriles and α-amino phosphonates under mild conditions. Preliminary study indicated that the formation of the product was through the Shono oxidation of imine species.

Minisci reaction, an important method for the construction of new carbon-carbon bonds, refers to one kind of the radical substitution reactions between a nucleophilic carbon radical and an electron-deficient nitrogen-containing aromatic heterocycle. Besides, organic electrosynthesis is experiencing a renaissance as a green synthesis technology and means. This review focuses on the recent advances in Minisci reactions under electrochemical conditions.