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Catalytic C–H/N–H cross-coupling is considered an ideal strategy for accessing anilines and their derivatives, but its synthetic execution remains extremely challenging, especially when the exclusion of external oxidants is desired. Reported herein is a photoelectrocatalytic method for the preparation of anilides through the C–H/N–H coupling of arenes and carbamates, which employs DDQ as a molecular catalyst. The reactions are conducted in a simple undivided cell with visible-light irradiation and without any need for external chemical oxidants. In addition, the reactions employ arenes as a limiting agent and are compatible with benzene and halogenated benzenes. [ABSTRACT FROM AUTHOR]

An electrochemical electrophilic bromination/spirocyclization of N-benzyl-acrylamides with 2-bromoethan-1-ol as the brominating reagent has been developed. The paired electrolysis employs low concentrations of bromine produced from both cathodic reduction and anodic oxidation as an electrophile, and realizes an H2O-involved electrophilic spirocyclization. A number of unexplored brominated 2-azaspiro[4.5]decanes are obtained with satisfactory yields under mild conditions, and the reaction exhibits good efficiency at the gram-scale synthesis. In addition, this approach is further highlighted by late-stage transformations and synthetic applications in constructing cyclohepta[c]pyrrole-1,6-diones via debromination tandem cyclization of brominated 2-azaspiro[4.5]decanes. [ABSTRACT FROM AUTHOR]

An organophotoelectrocatalytic method for the C(sp2)–H alkylation of heteroarenes with unactivated C(sp3)–H compounds through dehydrogenation cross-coupling has been developed. The C(sp2)–H alkylation combines organic catalysis, photochemistry and electrochemistry, avoiding the need for external metal-reagents, HAT-reagents, and oxidants. This protocol exhibits good substrate tolerance and functional group compatibility, providing a straightforward and powerful pathway to access a variety of alkylated heteroarenes under green conditions. [ABSTRACT FROM AUTHOR]

C−H/N‐H cross‐coupling is an ideal strategy to synthesize various amines but remains challenging owing to the requirement for sacrificial chemical oxidants and the difficulty in controlling the regio‐ and chemo‐selectivity. Herein we report a site‐selective electrochemical amination reaction that can convert benzylic C−H bonds into C‐N linkages via H2 evolution without need for external oxidants or metal catalysts. The synthetic strategy involves anodic cleavage of benzylic C−H to form a carbocation intermediate, which is then trapped with an amine nucleophile leading to C−N bond formation. Key to the success is to include HFIP as a co‐solvent to modulate the oxidation potentials of the alkylbenzene substrate and the aminated product to avoid overoxidation of the latter. [ABSTRACT FROM AUTHOR]

C−H/N‐H cross‐coupling is an ideal strategy to synthesize various amines but remains challenging owing to the requirement for sacrificial chemical oxidants and the difficulty in controlling the regio‐ and chemo‐selectivity. Herein we report a site‐selective electrochemical amination reaction that can convert benzylic C−H bonds into C‐N linkages via H2 evolution without need for external oxidants or metal catalysts. The synthetic strategy involves anodic cleavage of benzylic C−H to form a carbocation intermediate, which is then trapped with an amine nucleophile leading to C−N bond formation. Key to the success is to include HFIP as a co‐solvent to modulate the oxidation potentials of the alkylbenzene substrate and the aminated product to avoid overoxidation of the latter. [ABSTRACT FROM AUTHOR]

Summary of main observation and conclusion: An electrochemical synthesis of oxazol‐2‐ones and imidazol‐2‐ones has been developed via 5‐exo‐dig cyclization of propargylic carbamates‐ and ureas‐derived amidyl radicals. The electrosynthesis relies on the dual function of 2,2,6,6‐tetramethylpiperidin‐ 1‐yl)oxyl (TEMPO) as a redox mediator for amidyl radical formation and an oxygen atom donor. The reactions are conducted under mild conditions using a simple setup and provide convenient access to functionalized oxazol‐2‐ones and imidazol‐2‐ones from readily available materials. [ABSTRACT FROM AUTHOR]

A photoelectrochemical method for the C−H alkylation of heteroarenes with organotrifluoroborates has been developed. The merger of electrocatalysis and photoredox catalysis provides a chemical oxidant‐free approach for the generation and functionalization of alkyl radicals from organotrifluoroborates. A variety of heteroarenes were functionalized using primary, secondary, and tertiary alkyltrifluoroborates with excellent regio‐ and chemoselectivity. A radical approach: A photoelectrochemical method has been developed for the C−H alkylation of heteroarenes with organotrifluoroborates under oxidant‐free conditions. A variety of heteroarenes can be functionalized with primary, secondary, and tertiary alkyl groups with excellent regio‐ and chemoselectivity. [ABSTRACT FROM AUTHOR]

A photoelectrochemical method for the C−H alkylation of heteroarenes with organotrifluoroborates has been developed. The merger of electrocatalysis and photoredox catalysis provides a chemical oxidant‐free approach for the generation and functionalization of alkyl radicals from organotrifluoroborates. A variety of heteroarenes were functionalized using primary, secondary, and tertiary alkyltrifluoroborates with excellent regio‐ and chemoselectivity. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: A photoelectrochemical approach for the C—H silylation of heteroarenes through dehydrogenation cross‐coupling with H2 evolution has been developed. The photoelectrochemical C—H silylation depends on hydrogen atom transfer (HAT) from silanes to Cl‐radical generated through the light‐induced homolytic cleavage of Cl2, in which Cl2 was produced by electrochemical oxidation of chloride. A large number of silylated heterocyclic molecules are rapidly constructed in satisfactory yields without relying on oxidants and metal reagents. [ABSTRACT FROM AUTHOR]

Abstract: We have developed a unified strategy for preparing a variety of imidazo‐fused N‐heteroaromatic compounds through regiospecific electrochemical (3+2) annulation reaction of heteroarylamines with tethered internal alkynes. The electrosynthesis employs a novel tetraarylhydrazine as the catalyst, has a broad substrate scope, and obviates the need for transition‐metal catalysts and oxidizing reagents. [ABSTRACT FROM AUTHOR]

Abstract: We have developed a unified strategy for preparing a variety of imidazo‐fused N‐heteroaromatic compounds through regiospecific electrochemical (3+2) annulation reaction of heteroarylamines with tethered internal alkynes. The electrosynthesis employs a novel tetraarylhydrazine as the catalyst, has a broad substrate scope, and obviates the need for transition‐metal catalysts and oxidizing reagents. [ABSTRACT FROM AUTHOR]

We report herein an atom-economical and sustainable approach to access amidinyl radical intermediates through the anodic cleavage of N−H bonds. The resulting nitrogen-centered radicals undergo cyclizations with (hetero)arenes, followed by rearomatization, to afford functionalized tetracyclic benzimidazoles in a highly straightforward and efficient manner. This metal- and reagent-free C−H/N−H cross-coupling reaction exhibits a broad substrate scope and proceeds with high chemoselectivity. [ABSTRACT FROM AUTHOR]

We report herein an atom-economical and sustainable approach to access amidinyl radical intermediates through the anodic cleavage of N−H bonds. The resulting nitrogen-centered radicals undergo cyclizations with (hetero)arenes, followed by rearomatization, to afford functionalized tetracyclic benzimidazoles in a highly straightforward and efficient manner. This metal- and reagent-free C−H/N−H cross-coupling reaction exhibits a broad substrate scope and proceeds with high chemoselectivity. [ABSTRACT FROM AUTHOR]

Indoles and azaindoles are among the most important heterocycles because of their prevalence in nature and their broad utility in pharmaceutical industry. Reported herein is an unprecedented noble-metal- and oxidant-free electrochemical method for the coupling of (hetero)arylamines with tethered alkynes to synthesize highly functionalized indoles, as well as the more challenging azaindoles. [ABSTRACT FROM AUTHOR]

Indoles and azaindoles are among the most important heterocycles because of their prevalence in nature and their broad utility in pharmaceutical industry. Reported herein is an unprecedented noble-metal- and oxidant-free electrochemical method for the coupling of (hetero)arylamines with tethered alkynes to synthesize highly functionalized indoles, as well as the more challenging azaindoles. [ABSTRACT FROM AUTHOR]

Comprehensive Summary Key Scientists Organic fluorine compounds are ubiquitous and pivotally important organic molecules, yet their activation and transformation have long been a formidable challenge due to the high energy and low reactivity of C—F bonds. Organic electrosynthesis, an environmentally benign synthetic method in organic chemistry, enables a myriad of chemical transformations without the need for external redox reagents. In recent years, organic electrochemistry has emerged as a powerful tool for achieving the activation and transformation of C—F bonds in fluorine‐containing compounds. This review aims to succinctly recapitulate the latest advancements in the electrochemical defluorinative transformations of C—F bonds and to delve into the reaction design, mechanistic insights, and developmental prospects of these methods.In 1959, Lund was the first to pioneer the electroreduction of CF3 to CH3 group. Electrochemistry has lately provided new opportunities for efficient conversion of organic fluorides. In 2020, Zhou and coworkers discovered the electrochemical defluorinative carboxylation of α‐CF3 alkenes. Lambert and colleagues reported electrophotocatalytic defluorinative amination of aryl fluorides. Electrochemical hydrodefluorination of trifluoromethylketones was developed by Lennox and coworkers in 2021. In the same year, Wang and Guo disclosed electrochemical radical defluorinative alkylation of α‐CF3 alkenes with Katritzky salts as the alkyl radical precursors. Subsequently, Wu and Liao described a transition‐metal‐free, site‐selective C—F arylation of polyfluoroarenes with (het)arenes using paired electrophotocatalysis. In 2023, numerous efforts were made to achieve electrochemical C—F bond activation. Xia and Guo developed an organoboron‐controlled method for the chemoselective electrochemical sequential (deutero)hydrodefluorination of trifluoroacetamides. [ABSTRACT FROM AUTHOR]

An electrochemical epoxidation of unactivated olefins using water as the source of oxygen atoms has been developed. The epoxidation reaction employs seminormal-BrCH2CH2OH as the mediator, which shows good functional group compatibility, and can easily be performed on the gram scale. A wide range of unactivated olefins could be tolerated to give the functionalized epoxides with satisfactory results at room temperature. [ABSTRACT FROM AUTHOR]

Light and electric current power the C−H alkylation of heteroaromatics under oxidant‐free conditions. Organotrifluoroborates are converted into radicals that participate in intermolecular oxidative transformations without overoxidation to carbocations. As H.‐C. Xu and co‐workers describe in their Communication on page 4592 ff., this photoelectrochemical approach may provide a platform for further sustainable synthetic methodologies. [ABSTRACT FROM AUTHOR]

Licht und elektrischer Strom treiben die C‐H‐Alkylierung von Heteroarenen unter oxidationsmittelfreien Bedingungen an. Organotrifluorborate werden in Radikale umgewandelt, die an intermolekularen oxidativen Transformationen zu Carbokationen ohne Überoxidation teilnehmen. Wie H.‐C. Xu und Mitarbeiter in ihrer Zuschrift auf S. 4640 beschreiben, bietet dieser photoelektrochemische Ansatz eine Plattform für nachhaltige Synthesemethoden. [ABSTRACT FROM AUTHOR]

The cover picture shows an electricity powered dehydrogenative [3+2] annulation reaction of (hetero)arylamines with tethered di‐, tri, and tetra‐substituted alkenes for the preparation of indoline and azaindoline products. The electrochemical reactions proceed through H2 evolution and thus avoid the use of stoichiometric chemical oxidants. This method, which is applicable to the preparation of highly functionalized (aza)indoline scaffold, enables the total synthesis of (±)‐hinckdentine A in 12 steps. More details are discussed in the article by Xu et al. on page 909–915. [ABSTRACT FROM AUTHOR]

Abstract: An electrochemical synthesis of functionalized (aza)indolines through dehydrogenative [3+2] annulation of arylamines with tethered alkenes has been developed. Previous reported syntheses through similar inter‐ and intramolecular annulation reactions required noble‐metal catalysts and are mostly limited to terminal alkenes or 1,3‐dienes. The electrosynthesis employs the easily available and inexpensive ferrocene as the molecular catalyst and is compatible with di‐, tri‐ and even tetrasubstituted alkenes to construct indolines as well as the more challenging azaindolines. Employing the newly developed electrosynthesis as a key step, the total synthesis of marine alkaloid (±)‐hinckdentine A has been achieved in 12 steps (longest linear sequence) from commercially available materials. [ABSTRACT FROM AUTHOR]

Redoxchemie. In ihrer Zuschrift auf S. 9314 ff. präsentieren X. Lu, H. ‐ C. Xu et al. eine effiziente elektrochemische Synthese für hoch funktionalisierte Indole und Azaindole mit Ferrocen als Redoxkatalysator, die theoretisch nur H2 als weiteres Produkt liefert. [ABSTRACT FROM AUTHOR]