Electrochemical-Promoted Nickel-Catalyzed Reductive Allylation of Aryl Halides

Visible Light Photoredox-Catalyzed Radical Defluorinative Arylation of α-Trifluoromethyl Alkenes with Aryl Chlorides

Photocatalytic defluorinative cross-coupling reactions of α-trifluoromethyl alkenes with diverse radical precursors have emerged as a powerful strategy for the synthesis of gem-difluoroalkenes. However, the radical defluorinative arylation is relatively rare due to the limitation of aryl radical precursors. Aryl chlorides, as ideal candidates, remain a large challenge in this reaction because of the chemical inertness of the C(sp2)-Cl bond and their high negative reduction potential. Herein, we report a radical defluorinative arylation of α-trifluoromethyl alkenes with aryl chlorides as aryl radical precursors through a consecutive photoinduced electron transfer (ConPET) process. This protocol features mild conditions, operational simplicity, wide substrate scope, and functional group tolerance, producing a diverse range of benzylic gem-difluoroalkenes in moderate to good yields. The scale-up reaction and the valuable transformations of products demonstrate the great potential applications of this approach.

Electrocatalytic Micelle-Driven Hydrodefluorination for Accessing Unprotected Monofluorinated Indoles

Toxic organic solvents and electrolytes, traditionally indispensable for electro-organic synthesis, are now being reconsidered. In developing more sustainable electro-organic synthesis, we've harnessed the aqueous micelles as solvents and electrolyte-like structures when deformed under an electric field. The technology is showcased in synthetically highly valued hydrodefluorination reactions of difluorinated indoles. This mild electrosynthetic method produces monofluorinated unprotected indole scaffolds. Our approach minimizes waste and enhances atom economy, reducing reliance on expensive and hazardous solvents and electrolytes. The surfactant's potential for recycling was verified for two cycles. Cyclic voltammetry analysis has corroborated that PS-750-M micelles in water establish a more efficient platform for hydrodefluorination. Our technology simplifies the production of monofluorinated indoles, which are crucial for many drug-like molecules.

Transition-Metal-Free Late-Stage Decarboxylative gem-Difluoroallylation of Primary Alkyl Acids

A transition-metal-free late-stage decarboxylative gem-difluoroallylation of carboxylic acids with α-trifluoromethyl alkenes has been described by the use of organo-photoredox catalysis. Both primary alkyl and heteroaryl acids were readily incorporated. This approach merits feedstock materials, mild reaction conditions, and wide functionality tolerance. The synthetic utility of this approach has been highlighted by the late-stage functionalization of a variety of acid-containing natural products and drug molecules.

When transition-metal catalysis meets electrosynthesis: a recent update

While aiming at sustainable synthesis, organic electrosynthesis has attracted increasing attention in the past few years. In parallel, with a deeper understanding of catalyst and ligand design, 3d transition-metal catalysis allows the conception of more straightforward synthetic routes in a cost-effective fashion. Owing to their intrinsic advantages, the merger of organic electrosynthesis with 3d transition-metal catalysis has offered huge opportunities for conceptually novel transformations while limiting ecological footprint. This review summarizes the key advancements in this direction published in the recent two years, with specific focus placed on strategy design and mechanistic aspects.

Metal-ligand cooperativity in chemical electrosynthesis

Electrochemistry has been an increasingly useful tool for organic synthesis, as it can selectively generate reactive intermediates under mild conditions using an applied potential. Concurrently, synergistic activity of a metal and a ligand has been used in thermal catalysis and electrocatalytic renewable fuel generation for substrate selectivity and improved catalyst activity. Combining these synthetic strategies is an attractive approach for mild, selective, and sustainable electrosynthesis. This perspective discusses examples of metal-ligand synergistic catalysis in electrochemical applications in organic and organometallic synthesis. The range of reactions and ligand design principles illustrates many opportunities for further discovery in this area and the potential for far-reaching synthetic benefits.

Electrochemical Nickel-Catalyzed 1,2-Diarylation of 1,3-Dienes

Due to the presence of carbon-carbon double bonds, 1,3-dienes exhibit great reactivity. A protocol for the site-selective diarylation of terminal 1,3-dienes is reported here. The transformation is facilitated by the Ni catalyst without the need for additional ligands, utilizing an electrochemical setup. Preliminary results indicate that by introducing chiral ligands moderate enantioselective diarylation products can be obtained. This method affords diversely substituted diarylated products that occur as structural motifs in various natural products.

Regiodivergent sulfonylation of terminal olefins via dearomative rearrangement

Sulfones are fascinating and highly used functional groups, but current syntheses still have limitations. Here, a regiodivergent transition metal-free approach towards sulfones [(E)-allylic sulfones and α-sulfonyl-methyl styrenes] is reported. The method employs commercially available olefins, bases, additives, solvents, and sodium sulfinates (RSO2Na) and produces adducts in good yields. Considering that up to 4 reactions (bromination, dearomative rearrangement, E2, and SN2) are happening, this approach is very efficient. The structures of key adducts were confirmed by X-ray crystallography.

Nickel-Catalyzed Enantioselective Dearomative Heck-Reductive Allylic Defluorination Reaction of Indoles

Herein, we describe a nickel-catalyzed asymmetric dearomative aryl-difluoroallylation reaction of indoles with α-trifluoromethyl alkenes as an electrophilic coupling partner. The reaction proceeds via a cascade sequence involving dearomative Heck cyclization and reductive allylic defluorination. A series of gem-difluoroallyl substituted indolines are obtained in moderate to good yields (36-77% yield) with excellent enantioselectivity (up to 99% ee). The reaction features broad functional group tolerance, scaled-up synthesis, and late-stage diversification.

Pd-Catalyzed Multicomponent Cross-Coupling of Allyl Esters with Alkyl Bromides and Potassium Metabisulfite: Access to Allylic Sulfones

A Pd-catalyzed multicomponent cross-coupling of allyl esters with alkyl bromides to synthesize allylic sulfones by using K2S2O5 as a connector is first reported. The reaction displays a broad range of substrate generality along with excellent functional group compatibility and produces the products with high regioselectivity (only E). Furthermore, the biologically active molecules with a late-stage modification, including aspirin, menthol, borneol, and estrone, are also highly compatible with the multicomponent cross-coupling reaction. Mechanistic studies indicate that the process of SO2 insertion into the C-Pd bond was involved in this transformation.

Photo/Ni dual-catalyzed radical defluorinative sulfonylation to synthesize gem-difluoro allylsulfones

Radical defluorinative functionalization of α-trifluoromethyl styrenes represents an effective way toward gem-difluoroalkenes. There are general interests in developing novel synthetic protocols for defluorinative functionalization with various types of radicals. However, reports on the preparation of gem-difluoro allylsulfones via an S-centered radical pathway are limited. Herein, we developed a photo/nickel dual-catalyzed defluorinative sulfonylation that rapidly and reliably synthesizes gem-difluoro allylsulfones. The merit of this protocol is exhibited by its mild conditions and wide scope, thus providing a novel strategy for the sulfonyl radical participating in radical defluorinative coupling.

A guide to organic electroreduction using sacrificial anodes

Organic electrosynthesis is a green strategy for the synthesis of valuable molecules. Electrochemical reactions using sacrificial metal anodes enable new reactivity to be uncovered that could not be achieved with traditional non-electrochemical methods. Compared with reactions using metal powder as the reducing reagent, the mild electroreduction protocols usually exhibit diverse reactivity and excellent selectivity. The inexpensive metal anodes possess low oxidation potential, which could prevent undesired overoxidation of substrates, active intermediates and products. The in situ generated metal ions from sacrificial anodes could not only serve as Lewis acids to activate the reactants but also as a promoter or mediator. This tutorial review highlights the recent achievements in this rapidly growing area within the past five years. The sacrificial anode-enabled electroreductions are discussed according to the reaction type.

Electrosynthetic C-O Bond Activation in Alcohols and Alcohol Derivatives

Alcohols and their derivatives are ubiquitous and versatile motifs in organic synthesis. Deoxygenative transformations of these compounds are often challenging due to the thermodynamic penalty associated with the cleavage of the C-O bond. However, electrochemically driven redox events have been shown to facilitate the C-O bond cleavage in alcohols and their derivatives either through direct electron transfer or through the use of electron transfer mediators and electroactive catalysts. Herein, a comprehensive overview of preparative electrochemically mediated protocols for C-O bond activation and functionalization is detailed, including direct and indirect electrosynthetic methods, as well as photoelectrochemical strategies.

Deaminative defluoroalkylation of α-trifluoromethylalkenes enabled by photoredox catalysis

Herein, we disclose a new photoredox-catalysed strategy to access gem-difluoroallylarenes from α-trifluoromethylalkenes with sterically hindered primary amines via C-N and C-F bond activation. This deaminative and defluorinative allylation is generally compatible with diverse functional groups and sterically hindered α-3° and 2° primary amines.

Electrosynthetic C-F bond cleavage

Fluorinated organic compounds are common among pharmaceuticals, agrochemicals and materials. The significant strength of the C-F bond results in chemical inertness that, depending on the context, is beneficial, problematic or simply a formidable synthetic challenge. Electrosynthesis is a rapidly expanding methodology that can enable new reactivity and selectivity for cleavage and formation of chemical bonds. Here, a comprehensive overview of synthetically relevant electrochemically driven protocols for C-F bond activation and functionalization is presented, including photoelectrochemical strategies.

Iron-catalysed reductive coupling for the synthesis of polyfluorinated compounds

Iron-catalysed reductive cross-coupling of difluorobromo acetic acid derivatives with trifluoromethyl olefins to afford polyfluorinated molecules, containing a difluorenyl and difluoroalkyl group, with a broad substrate scope.