Electrochemistry represents one of the most intimate ways of interacting with molecules. This review discusses advances in synthetic organic electrochemistry since 2000. Enabling methods and synthetic applications are analyzed alongside innate advantages as well as future challenges of electroorganic chemistry.

Synthetic Organic Electrochemical Methods Since 2000: On the Verge of a Renaissance

4.2. Solid-Supported Electrolytes 2280 4.3. Solid-Supported Mediators 2282 4.4. Supported Substrate-Product Capture 2283 4.5. A Unique Electrolyte/Solvent System 2285 5. Reaction Conditions 2285 5.1. Supercritical Fluids 2285 5.1.1. Electrochemical Properties of scCO2 2285 5.1.2. Electroreductive Carboxylation in scCO2 2286 5.1.3. Electrochemical Polymerization in scCO2 2286 5.2. The Cation-Pool Method 2286 5.2.1. Generation of N-Acyliminium Ion Pools 2286 5.2.2. Generation of Alkoxycarbenium Ion Pools 2287 5.2.3. Generation of Diarylcarbenium Ion Pools 2288 5.2.4. Generation of Other Cation Pools 2289 6. Electrochemical Devices 2289 6.1. Electrode Materials 2289 6.2. Ultrasound and Centrifugal Fields 2290 6.3. Electrochemical Microflow Systems 2290 7. Combinatorial Electrochemical Synthesis 2292 7.1. Parallel Electrolysis Using a Macrosystem 2292 7.2. Parallel Electrolysis Using a Microsystem 2293 7.3. Serial Electrolysis Using a Microsystem 2294 8. Conclusions 2294 9. Acknowledgments 2294 10. References 2294

Modern Strategies in Electroorganic Synthesis

Organic electrosynthesis: a promising green methodology in organic chemistry

Conventional methods for carrying out carbon–hydrogen functionalization and carbon–nitrogen bond formation are typically conducted at elevated temperatures, and rely on expensive catalysts as well as the use of stoichiometric, and perhaps toxic, oxidants. In this regard, electrochemical synthesis has recently been recognized as a sustainable and scalable strategy for the construction of challenging carbon–carbon and carbon–heteroatom bonds. Here, electrosynthesis has proven to be an environmentally benign, highly effective and versatile platform for achieving a wide range of nonclassical bond disconnections via generation of radical intermediates under mild reaction conditions. This review provides an overview on the use of anodic electrochemical methods for expediting the development of carbon–hydrogen functionalization and carbon–nitrogen bond formation strategies. Emphasis is placed on methodology development and mechanistic insight and aims to provide inspiration for future synthetic applications in the field of electrosynthesis.

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Electrochemical strategies for C-H functionalization and C-N bond formation.

Electrochemistry serves as a powerful method for generating reactive intermediates, such as organic cations. In general, there are two ways to use reactive intermediates for chemical reactions: (1) generation in the presence of a reaction partner and (2) generation in the absence of a reaction partner with accumulation in solution as a “pool” followed by reaction with a subsequently added reaction partner. The former approach is more popular because reactive intermediates are usually short-lived transient species, but the latter method is more flexible and versatile. This review focuses on the latter approach and provides a concise overview of the current methods for the generation and accumulation of cationic reactive intermediates as a pool using modern techniques of electrochemistry and their reactions with subsequently added nucleophilic reaction partners.

Electrogenerated Cationic Reactive Intermediates: The Pool Method and Further Advances

We have successfully developed a novel electrolytic system using solid-supported bases for in situ generation of a supporting electrolyte from methanol as a solvent. Anodic methoxylation of phenyl 2,2,2-trifluoroethyl sulfide using solid-supported bases was carried out to provide the α-methoxylated product in good to excellent yields. The α-methoxylated product and solid-supported bases were easily separated by only filtration, and the separated solid-supported bases were recyclable. Anodic methoxylation of phenyl 2,2,2-trifluoroethyl sulfide was successfully carried out 10 times by the recycling of silica gel-supported piperidine in good yields.

Development of an electrolytic system using solid-supported bases for in situ generation of a supporting electrolyte from methanol as a solvent.

An electrolytic system that uses solid-supported bases for in situ generation of a supporting electrolyte from acetic acid solvent.

We have successfully developed a novel environmentally friendly electrolytic system using recyclable solid-supported bases for in situ generation of a supporting electrolyte from methanol as a solvent. It was found that solid-supported bases are electrochemically inactive at an electrode surface. It was also found that solid-supported bases dissociate methanol into methoxide anions and protons. Therefore, in the presence of solid-supported bases, it was clarified that methanol serves as both a solvent and a supporting electrolyte generated in situ. Anodic methoxylation of various compounds with solid-supported bases was carried out to provide the corresponding methoxylated products in good to excellent yields with a few exceptions. The methoxylated products and the solid-supported bases were easily separated by only filtration, and the desired pure methoxylated products were readily isolated simply by concentration of the filtrates. The separated and recovered solid-supported bases were recyclable for several times.

Development of a Novel Environmentally Friendly Electrolytic System by Using Recyclable Solid‐Supported Bases for In Situ Generation of a Supporting Electrolyte from Methanol as a Solvent: Application for Anodic Methoxylation of Organic Compounds

Electrolytic partial fluorination of organic compounds. Part 56: Highly regioselective anodic mono- and difluorination of s-triazolo[3,4-b][1,3,4]thiadiazine derivatives☆

This article describes our recent results of electroorganic synthesis, especially focusing on new organic electrolytic systems toward green sustainable chemistry as follows: (a) Electroorganic synthesis using recyclable solid-supported bases, (b) electrocatalytic hydrogenation and dehalogenation using new electrolytic systems, (c) electrosynthesis of organofluorine compounds, conducting polymers, and others in ionic liquids.

Toshio Fuchigami

Papers

Development of an electrolytic system using solid-supported bases for in situ generation of a supporting electrolyte from methanol as a solvent.

An electrolytic system that uses solid-supported bases for in situ generation of a supporting electrolyte from acetic acid solvent.

Development of a Novel Environmentally Friendly Electrolytic System by Using Recyclable Solid‐Supported Bases for In Situ Generation of a Supporting Electrolyte from Methanol as a Solvent: Application for Anodic Methoxylation of Organic Compounds

Electrolytic partial fluorination of organic compounds. Part 56: Highly regioselective anodic mono- and difluorination of s-triazolo[3,4-b][1,3,4]thiadiazine derivatives☆

Development of New Methodologies Toward Green Sustainable Organic Electrode Processes