Electrochemical Denitrative Cyclization Driven by Alternating Polarity.

Alternating current electrolysis has emerged as a promising technique for addressing challenging redox reactions that are otherwise difficult or impossible for direct current electrolysis. Under mild and transition-metal-free reaction conditions, a general electrochemical denitrative cyclization of nitroarenes was developed to access various cyclic sulfone-containing derivatives of biological significance. The key to success lies in the facile manipulation of multiple redox events upon rapid alternating polarity switching to enhance the selectivity and efficiency.

Hypervalent iodine catalysis enabled iterative multi-fluorination: not just a simple alternative for the electrochemical approach.

Unlike the well-established fluoroalkylation, the direct incorporation of multiple fluorine atoms into small molecules iterative fluorinations has been much less investigated. Herein, we report a hypervalent iodine catalytically selective multi-fluorination in which the fluorination degree is controlled by the delicate balance between the HF/amine ratios. The and of hypervalent iodine catalysis and the previously established electrochemical approach in the iterative multi-fluorinations are also provided.

Batch and Continuous-Flow Electrochemical Geminal Difluorination of Indeno[1,2-]furans.

An electrochemical -difluorination of indeno[1,2-]furans using commercially available and easy-to-use triethylamine trihydrofluoride as both the electrolyte and fluorinating agent was developed. Remarkably, different reaction pathways of indeno[1,2-]furans, i.e.

Electrochemical Continuous-Flow Scholl Reaction toward Polycyclic Aromatic Hydrocarbons.

The preparation of polycyclic aromatic hydrocarbons (PAHs) by the Scholl reaction is typically performed by using superstoichiometric oxidants. Herein, we develop an electrochemical continuous-flow Scholl reaction to access PAHs that features a reduction in the use of supporting electrolytes and easy scale-up without changing the reaction conditions and setups. This reaction allows the synthesis of distorted PAHs containing three [5]helicene units that possess intriguing electronic and optical properties.

Cobalt-catalyzed amination of aziridines and azetidines toward 1,2- and 1,3-diamines.

Diamines play important roles in synthetic organic chemistry and thus facilitate life and materials sciences. Herein we report a cobalt-catalyzed ring opening, nucleophilic amination of aziridines and azetidines with -fluorosulfonamides toward a wide range of 1,2- and 1,3-diamine derivatives in moderate to good yields under mild conditions.

Electrochemical cascade migratory -cyclization of 2-alkynylbenzenesulfonamides.

Efficient control over several possible reaction pathways of free radicals is the chemical basis of their highly selective transformations. Among various competing reaction pathways, sulfonimidyl radicals generated from the electrolysis of 2-alkynylbenzenesulfonamides undergo cascade migratory or -cyclization cyclization selectively. It is found that the incorporation of an extra 2-methyl substituent biases the selective migration of the acyl- over vinyl-linker of the key spirocyclic cation intermediate and thus serves as an enabling handle to achieve the synthetically interesting yet under-investigated cascade migratory cyclization of spirocyclic cations.

Current-Controlled Electrochemical Approach Toward Mono- and Trifluorinated Isoindolin-1-one Derivatives.

An electrochemical intramolecular 5- aza-cyclization of 2-alkynylbenzamides and subsequent nucleophilic fluorination have been developed to afford the highly selective synthesis of mono- and trifluorinated isoindolin-1-one derivatives. This work demonstrates the unique capability of synthetic electrochemistry in controlling reaction selectivity through the applied electrolytic parameters. In addition, the obtained monofluorinated 3-methyleneisoindolin-1-one () displays interesting photophysical properties that are not observed in its nonfluorinated analog.

Alternating the current direction.

Waveform-controlled electrolysis enables the carbon-carbon coupling of carboxylic acids.

Electrochemical Dearomative Spirocyclization.

Electrochemical dearomative spirocyclization serves as a green and sustainable approach to convert the flat, two-dimension aromatic feedstock into the value-added three-dimension spirocyclic architectures. This review highlights the recent advances, emphasizes mechanistic discussions, and showcases synthetic applications of this emerging versatile and powerful transformation.

An electrochemical multicomponent reaction toward C-H tetrazolation of alkyl arenes and vicinal azidotetrazolation of alkenes.

The widespread use of tetrazoles in medicine, biology, and materials science continuously promotes the development of their efficient and selective syntheses. Despite the prosperous development of multicomponent reactions, the use of the most abundant and inexpensive chemical feedstocks, , alkanes and alkenes, toward the preparation of diverse tetrazoles remains elusive. Herein, we developed an electrochemical multicomponent reaction (e-MCR) for highly efficient and selective C-H tetrazolation of alkyl arenes.

Electrochemical synthesis of vicinal azidoacetamides.

Vicinal diamines are an important structural motif in bioactive natural products and pharmaceutical intermediates. Herein, an environmentally friendly and efficient electrochemical approach to azidoacetamides, as one variant of vicinal diamines, has been developed. This reaction features mild conditions and broad substrate scope, without the use of any chemical oxidant or transition-metal catalysts.

Electrophotocatalytic oxygenation of multiple adjacent C-H bonds.

Oxygen-containing functional groups are nearly ubiquitous in complex small molecules. The installation of multiple C-O bonds by the concurrent oxygenation of contiguous C-H bonds in a selective fashion would be highly desirable but has largely been the purview of biosynthesis. Multiple, concurrent C-H bond oxygenation reactions by synthetic means presents a challenge, particularly because of the risk of overoxidation.

Synthesis of Indeno[1,2-]furans via Cobalt-Catalyzed Radical-Polar Crossover [3 + 2] Cycloaddition of -Alkynylaryl β-Dicarbonyls.

Fused polycyclic furans are privileged structural scaffolds in materials chemistry, including organic semiconductors. Specifically, indeno[1,2-]furans are an interesting type of polycyclic furans featuring a fused furan and indenone framework. Unfortunately, limited studies on their photophysical properties have been performed, probably owing to the lack of efficient and straightforward approaches to those compounds.

Electrochemical vicinal oxyazidation of α-arylvinyl acetates.

α-Azidoketones are valuable and versatile building blocks in the synthesis of various bioactive small molecules. Herein, we describe an environmentally friendly and efficient electrochemical vicinal oxyazidation protocol of α-arylvinyl acetates to afford diverse α-azidoketones in good yields without the use of a stoichiometric amount of chemical oxidant. A range of functionality is shown to be compatible with this transformation, and further applications are demonstrated.

Electrochemical Dearomative Spirocyclization of -Acyl Thiophene-2-sulfonamides.

The Friedel-Crafts type alkylation of C2-tethered thiophenes has been reported to be nonregioselective. Taking advantage of the highly regioselective 5- spirocyclization of an electrochemically generated amidyl radical, we have unraveled an electrochemical dearomative spirocyclization of -acyl thiophene-2-sulfonamides. Various nucleophilic agents, including carboxylates, alcohols, and fluoride, are readily incorporated to afford the remotely functionalized spirocyclic dihydrothiophenes, and their novel spirocyclic scaffolds have been shown to exhibit promising antitumor activities.

Electrochemical Migratory Cyclization of N-Acylsulfonamides.

Benzoxathiazine dioxide, as a bioisostere of the clinically widely used diazoxide, exhibits interesting biological activity. However, limited success has been achieved in terms of its concise and direct synthesis. We report herein a facile electrochemical migratory cyclization of N-acylsulfonamides to access a diverse array of benzoxathiazine dioxides.

Electrochemical 5- aza-cyclization of 2-alkynylbenzamides toward 3-hydroxyisoindolinone derivatives.

Preparation of biologically relevant 3-hydroxyisoindolinones from readily available 2-alkynylbenzamides is an appealing synthetic approach. However, such kinds of compounds preferably undergo O-attacked 5-/6- cyclizations. Herein, we report an electrochemically generated amidyl radical proceeding a highly selective N-attacked 5- radical cyclization to form 3-hydroxyisoindolinone derivatives.

Electrochemical Sulfoxidation of Thiols and Alkyl Halides.

Sulfoxides are actively engaged as versatile synthetic building blocks, chiral ligands, bioactive molecules, and function materials. However, their oxidative syntheses from thioethers are inevitably impeded by overoxidation, excess oxidants, and the tedious preparation of thioethers. To address these shortcomings, we report herein a highly selective electrochemical sulfoxidation reaction featuring the use of simple starting materials, .

Cobalt-catalyzed Divergent Markovnikov and Anti-Markovnikov Hydroamination.

Catalytic hydroamination of the readily available alkenes is among the most straightforward means to construct diverse alkyl amines. To this end, the facile access to both regioselectivity, , Markovnikov or anti-Markovnikov hydroamination, with minimum reaction-parameter alternation, remains challenging. Herein, we report a cobalt-catalyzed highly selective and divergent Markovnikov and anti-Markovnikov hydroamination of alkenes, in which the switch of regioselectivity is achieved simply by the variation of the addition sequence of 9-BBN.

Electrochemical fluorosulfonylation of styrenes.

An environmentally friendly and efficient electrochemical fluorosulfonylation of styrenes has been developed. With the use of sulfonylhydrazides and triethylamine trihydrofluoride, a diverse array of β-fluorosulfones could be readily obtained. This reaction features mild conditions and a broad substrate scope, which could also be conveniently extended to a gram-scale preparation.

Desulfonylative Electrocarboxylation with Carbon Dioxide.

Electrocarboxylation of organic halides is one of the most investigated electrochemical approaches for converting thermodynamically inert carbon dioxide (CO) into value-added carboxylic acids. By converting organic halides into their sulfone derivatives, we have developed a highly efficient electrochemical desulfonylative carboxylation protocol. Such a strategy takes advantage of CO as the abundant C1 building block for the facile preparation of multifunctionalized carboxylic acids, including the nonsteroidal anti-inflammatory drug ibuprofen, under mild reaction conditions.

Cobalt-Catalyzed Divergent Aminofluorination and Diamination of Styrenes with -Fluorosulfonamides.

A cobalt-catalyzed aminofluorination reaction of styrenes with -fluorosulfonamides serving as both the amination and fluorination agents has been developed. The switch of selectivity in this catalytic reaction from aminofluorination to diamination could be easily achieved by the addition of 1.0 equiv of PPh.

Cobalt fluorides: preparation, reactivity and applications in catalytic fluorination and C-F functionalization.

Recent advances in the investigation of cobalt fluorides in organofluorine chemistry are highlighted. The preparation and reactivity of inorganic and organometallic cobalt fluorides are discussed. The in-depth understanding of the structures and reactivity of cobalt fluorides allows chemists to develop diverse innovative catalytic fluorination and C-F functionalization.

Redox Neutral Radical-Relay Cobalt Catalysis toward C-H Fluorination and Amination.

A redox neutral radical-relay cobalt-catalyzed intramolecular C-H fluorination of -fluoroamides featuring the in situ formed cobalt fluorides as the latent radical fluorinating agents is reported. Moreover, the reactivity of such a cobalt catalysis could be diverted from C-H fluorination to amination by engineering substrates' conformational flexibility. Preliminary mechanistic studies (UV-vis spectroscopy, cyclic voltammetry studies and DFT calculations, etc.