α-Keto Acids: Acylating Agents in Organic Synthesis

Light-Mediated Direct Decarboxylative Giese Aroylations without a Photocatalyst

Previous light-mediated approaches to the direct decarboxylative Giese aroylation reaction have mainly relied on the use of a photocatalyst and a reductive quenching pathway. By exploiting a mechanistically distinct oxidative protocol, we have successfully developed a photocatalyst-free, light-mediated direct Giese aroylation methodology.

Direct C-H functionalisation of azoles via Minisci reactions

Azoles have widespread applications in medicinal chemistry; for example, thiazoles, imidazoles, benzimidazoles, isoxazoles, tetrazoles and triazoles appear in the top 25 most frequently used N-heterocycles in FDA-approved drugs. Efficient routes for the late-stage C-H functionalisation of azole cores would therefore be highly desirable. The Minisci reaction, a nucleophilic radical addition reaction onto N-heterocyclic bases, is a direct C-H functionalisation reaction that has the potential to be a powerful method for C-H functionalisations of azole scaffolds. However, azoles have not been as widely studied as substrates for modern Minisci-type reactions as they are often more electron-rich and thus more challenging substrates compared to electron-poor 6-membered N-heterocycles such as quinolines, pyrazines and pyridines typically used in Minisci reactions. Nevertheless, with the prevalence of azole scaffolds in drug design, the Minisci reaction has the potential to be a transformative tool for late-stage C-H functionalisations to efficiently access decorated azole motifs. This review thus aims to give an overview of the C-H functionalisation of azoles via Minisci-type reactions, highlighting recent progress, existing limitations and potential areas for growth.

Visible-Light Photoredox-Catalyzed Direct Decarboxylative Functionalization of α-Keto Acids

A novel and environmentally friendly photocatalytic strategy is presented for generating acyl radicals from benzoylformic acids, which are subsequently trapped by various sulfone-based SOMOphiles. This strategy provides a robust toolkit to access a variety of synthetically important functionalized aryl-ketone derivatives, which efficiently and directly construct acyl-S, acyl-Se, acyl-C, and acyl-N bonds. The broad substrate scope, excellent functional group compatibility, and mild reaction conditions make this protocol practical and attractive.

Integrating Umpolung and CO2 Shuttling Strategies for the Synthesis of 12C- and 13C-α-Ketoacids from Aldehydes

The direct carboxylation of aldehydes with CO2 is rare due to the polarity mismatch between these two electrophilic substrates. To address this challenge, we propose a sequential approach for synthesizing α-ketoacids from commercially available aldehydes by integrating umpolung and CO2 shuttling strategies. This transition metal-free shuttle carboxylation method enables the transfer of CO2 from triphenylacetic acid potassium salt to thioacetal, eliminating the need for handling pressurized CO2 gas or using specialized equipment, while also enhancing the reaction's functional group tolerance. Furthermore, the use of stoichiometric or slightly excess amounts of triphenylacetic acid potassium salt as a formal CO2 donor makes it suitable for complete 13C labeling of α-ketoacids.

Recent Developments in Photoinduced Decarboxylative Acylation of α-Keto Acids

Ketones are ubiquitous patterns found in various biological molecules and natural products. In recent years, a number of acylation methods have been developed based on the use of α-oxocarboxylic acids as acyl-transfer reagents, with particular emphasis on the photoinduced decarboxylative acylation of α-keto acids. This review focuses on the latest advancements in acylation methodologies through the decarboxylation of α-keto acids over the past several years, highlighting their product diversity, selectivity, and applicability. Where possible, the mechanistic rationale is presented, providing a positive outlook for the promising future of this field.

Selective Synthesis of Amides and α-Ketoamides via Electrochemical Decarboxylation and Dehydration

An electrochemical and selective decarboxylation and dehydration using α-keto acids with amines is accomplished, which leads to the easy accessibility of amides and α-ketoamides, which are not only ubiquitous and valuable structure motifs found in pharmaceuticals, but also versatile building blocks in synthetic chemistry. Notably, for this efficient and green protocol, neither metal catalysts nor external oxidants are required. The process exhibits a broad scope and functional group tolerance to deliver various amides and α-ketoamides. Moreover, these two reactions have also been applied to late-stage derivatization and can be safely conducted on gram scale.

Multiphoton tandem photoredox catalysis of [Ir(dFCF3ppy)2(dtbbpy)]+ facilitating radical acylation reactions

Photoredox catalytic radical acylation reactions, utilizing [Ir(dFCF3ppy)2(dtbbpy)]+ (IrIII) as the photocatalyst and α-keto acids as the starting substrates, have recently emerged as an attractive strategy for preparing ketone derivatives. While there is consensus on the importance of detailed mechanistic insights to maximize the formation of desired products, efforts focused on uncovering the underlying elementary mechanisms of IrIII photocatalytic radical acylation reactions are still lacking. Herein, using time-resolved spectroscopy, we observed the efficient quenching of the triplet state, 3IrIII*, via electron transfer from α-keto acids, resulting in the generatation of the reduced IrII. Subsequently, IrII rapidly transforms into a stable IrH+ species through protonation, with α-keto acid acting as a proton donor. Upon absorbing additional photon(s), IrH+ is expected to transform into IrH3, involving further hydrogenation/protonation. Emission and Fourier transform infrared (FTIR) spectroscopy, together with global analysis, identify the character of IrH3/3IrH3* and corroborate its contribution to representative radical acylation reactions (decarboxylative 1,4-addition of α-keto acids with Michael acceptors, decarboxylative coupling of α-keto acids with aryl halides, and decarboxylative cyclization of 2-alkenylarylisocyanides with α-keto acids), where IrH3/3IrH3* serves as the key species to trigger the second photoredox cycle. These results elucidate the existence and generality of the tandem photoredox catalysis mechanism for IrIII photocatalytic radical acylation reactions, providing advanced insights into the mechanism of IrIII-based photoredox processes and potentially expanding their application in the design and development of new synthetic methodologies.

Photochemical radical decarboxylative disulfuration of α-keto acids and oxamic acids

A visible-light-induced directed decarboxylative disulfuration of α-keto acids and oxamic acids was developed. As a result, a series of versatile mono acyl disulfide derivatives was synthesized under mild and sustainable reaction conditions. This protocol has a broad substrate scope, good functional-group tolerance, and excellent synthetic applications.

Novel cathodic and anodic dual-emitting electrochemiluminescence of Ru(bpy)32+/α-keto acid system

Novel cathodic and anodic dual-emitting electrochemiluminescence (ECL) of Ru(bpy)32+ and α-keto acids system are studied for the first time. Based on their cathodic and anodic ECL intensity, α-keto acids including oxalate, glyoxylic acid, pyruvic acid, and phenylglyoxylic acid can be directly sensitively detected. The limits of detection (LOD) of oxalate, glyoxylic acid, pyruvic acid, and phenylglyoxylic acid are 31.25 nM, 23.26 µM, 36.36 µM, and 18.52 µM, respectively. Possible mechanism of ECL produced is also proposed. Electrochemical results show that the reduction of oxygen at the cathode to produce ·OH is a vital step for cathodic and anodic dual-emitting ECL. Furthermore, using the enhancement strategy of S2O82-/Ag+ as coreactant accelerators is proposed considering that decarboxylation of α-keto acids to produce acyl radical can be achieved via S2O82- or Ag+. Using the S2O82-/Ag+ enhancement strategy, the LOD of oxalate, glyoxylic acid, pyruvic acid, and phenylglyoxylic acid are improved and are 2.12 nM, 0.37 µM, 3.23 µM, and 0.28 µM, respectively. Coreactants of Ru(bpy)32+ with dual-emitting ECL are expanded, which includes additional substances with organic carboxylic acid characterized by the keto group in α-position. It also provides an effective way to enhance ECL and improve sensitivity. More importantly, cathodic and anodic dual-emitting ECL greatly improves the selectivity.

Combining Umpolung and Carbon Isotope Exchange Strategies for Accessing Isotopically Labeled α-Keto Acids

The integration of umpolung and carbon isotope exchange for accessing isotopically labeled α-keto acids through photoredox catalysis is elucidated. This process involves the carbonyl umpolung of C(sp2)-α-keto acids to yield C(sp3)-α-thioketal acids, followed by the carbon isotope exchange of C(sp3)-α-thioketal acids, and ultimately, deprotection to generate carbon-labeled α-keto acids.

Carbonylative cyclization of biaryl enones with aldehydes and oxamic acids

An oxidative radical-promoted carbonylative cyclization strategy for the synthesis of phenanthren-9-(10H)-one frameworks from biaryl enones using aldehydes as the carbonyl radical sources is disclosed. The reaction proceeds through a sequential addition of a carbonyl radical to the olefin followed by cyclization with an aryl ring. The method is further extended to carbamoyl radicals generated from oxamic acids to access the corresponding phenanthrenones with amide functionalities.

Synthesis of thioesters using an electrochemical three-component reaction involving elemental sulfur

An electrochemical three-component reaction involving elemental sulfur is disclosed for achieving a metal-free, oxidant-free synthesis of thioesters in a high atom-economical, step-economical and chemoselective manner. A mechanistic investigation indicates that the use of elemental sulfur to trap acyl radical derived from radical umpolung of α-keto acid with an electrochemical design can efficiently generate a carbonyl thiyl radical, which can further be captured by diazoalkane to afford various thioesters.

Electrochemical quinuclidine-mediated Minisci-type acylation of N-heterocycles with aldehydes

The electro-generation of acyl radicals from both aromatic and aliphatic aldehydes remains an unmet challenge. We provide a solution to this challenge by merging electro-oxidation and a quinuclidine-mediated hydrogen atom transfer strategy. The generation of acyl radicals at decreased applied potentials compared to that of formyl oxidation exhibits excellent functional group compatibility.

Dual Photoredox and Nickel Catalysis in Regioselective Diacylation: Exploring the Versatility of Nickel Oxidation States in Allene Activation

We present a nickel-catalyzed regioselective radical diacylation of allenes with ketoacids to produce 1,4-dione products by dual photoredox and nickel catalysis. This integrated approach merges redox-active oxidative addition and reductive elimination steps with migratory insertion. The acyl radical generated in the photoredox cycle sequentially adds to Ni(I) and Ni(II) intermediates following a Ni(I)-Ni(II)-Ni(II)-Ni(III)-Ni(I) catalytic cycle. This methodology, supported by DFT calculations, demonstrates the potential of nickel catalysis in the creation of complex molecular architectures.

Visible-Light-Driven Decarboxylative Coupling of 2H-Indazoles with α-Keto Acids without Photocatalysts and Oxidants

An efficient synthesis of functionalized 3-acyl-2H-indazoles via visible-light-induced self-catalyzed energy transfer was developed. This method utilized a self-catalyzed energy transfer process between 2H-indazoles and α-keto acids, offering advantages like absence of photosensitizers, metal catalysts, and strong oxidants, broad substrate compatibility, and operational simplicity under mild conditions.

Synthesis of Quinazolinones and Benzothiazoles Using α-Keto Acids under Ball Milling

Mechanochemistry refers to the initiation of chemical reactions via mechanical forces such as milling, grinding, or shearing to achieve the chemical transformations. As a manifestation of mechanocatalysis, herein, an oxidant-free and solvent-free approach for the synthesis of quinazolinones (23 derivatives) and benzothiazoles (23 derivatives) has been developed through stainless-steel-driven decarboxylative acyl radical generation from α-keto acids. A library of 2-arylquinazolinones and 2-arylbenzothiazoles has been prepared in moderate to good yields at room temperature. Moreover, control experiments and XPS studies supported the reduction (by zerovalent iron) of molecular oxygen through the moderate abrasion of balls, which promoted the generation of a superoxide radical anion via a SET process.

Electrochemical oxidative decarboxylative of α-oxocarboxylic acids towards the synthesis of quinazolines and quinazolinones

A mild and environmentally electrochemical method for the synthesis of quinazolines and quinazolinones has been developed through anodic oxidation decarboxylative of α-oxocarboxylic acids. The present reaction was efficiently conducted by using simple and cheap NH4I as the N-source and electrolyte in an undivided cell. The desired products, quinazolines and quinazolinones, were isolated in high yield under chemical oxidant free conditions.

Photoredox-Catalyzed Hydroacylation of Azobenzenes with Carboxylic Acids

Acyl hydrazides are widely found in bioactive compounds and have important applications as versatile synthetic intermediates. In the current report, a photoredox-catalyzed hydroacylation of azobenzenes was disclosed with carboxylic acids as the acylation reagent, affording a variety of N,N'-disubstituted hydrazides. The process possesses the advantages of mild reaction conditions, broad substrate scope, and high efficiency. Preliminary mechanistic investigation indicated that the addition of an acyl radical to the azo compound should be involved.

Synthesis of Acylhydroquinones through Visible-Light-Mediated Hydroacylation of Quinones with α-Keto Acids

A mild and eco-friendly visible-light-induced protocol for the hydroacylation of quinones with α-keto acids has been developed. In the absence of any catalyst or additive, the decarboxylative hydroacylation proceeded smoothly under visible-light irradiation at room temperature. A wide range of quinones and α-keto acids were well-tolerated and afforded hydroacylation products up to 88% isolated yield. The reaction can be scaled up, and the induced groups are useful for further synthetic applications. Preliminarily, mechanistic studies indicated that photoactive quinones absorb visible light to facilitate the transformation.

Visible-Light-Driven Regioselective Decarboxylative Acylation of N-Methyl-3-phenylquinoxalin-2(1H)-one by Dual Palladium-Photoredox Catalysis Through C-H Activation

We report herein an efficient visible-light-promoted approach for the regioselective decarboxylative C-H acylation of N-methyl-3-phenylquinoxalin-2(1H)-ones using α-oxo-2-phenylacetic acids via dual palladium-photoredox catalysis. The reactions were carried out at room temperature in the presence of 24 W blue LEDs. The established protocol tolerated a wide range of functional groups and enabled the synthesis of several acylated N-methyl-3-phenylquinoxalin-2(1H)-ones in good to excellent yields. The proposed mechanism for this transformation was supported by control experiments.

Single-Step Synthesis of γ-Ketoacids through a Photoredox-Catalyzed Dual Decarboxylative Coupling of α-Oxo Acids and Maleic Anhydrides

A photocatalytic methodology for the single step synthesis of γ-ketoacids from α-ketoacids has been developed. This method employs maleic anhydrides as traceless synthetic equivalents of acrylic acids, achieving a selective cross-coupling via a dual decarboxylative strategy, where molecular CO2 is released as the only waste byproduct. The method has also been expanded to incorporate a highly regioselective, 3-component coupling with various alcohols to access functionalized γ-ketoesters.

Isocyanides as Catalytic Electron Acceptors in the Visible Light Promoted Oxidative Formation of Benzyl and Acyl Radicals

The recent disclosure of the ability of aromatic isocyanides to harvest visible light and act as single electron acceptors when reacting with tertiary aromatic amines has triggered a renewed interest in their application to the development of green photoredox catalytic methodologies. Accordingly, the present work explores their ability to promote the generation of both alkyl and acyl radicals starting from radical precursors such as Hantzsch esters, potassium alkyltrifluoroborates, and α-oxoacids. Mechanistic studies involving UV-visible absorption and fluorescence experiments, electrochemical measurements of the ground-state redox potentials along with computational calculations of both the ground- and the excited-state redox potentials of a set of nine different aromatic isocyanides provide key insights to promote a rationale design of a new generation of isocyanide-based organic photoredox catalysts. Importantly, the green potential of the investigated chemistry is demonstrated by a direct and easy access to deuterium labeled compounds.

Dual Palladium-Photoredox-Mediated Regioselective Acylation of Carbazoles and Indolines

We have described a dual palladium-photoredox-catalyzed highly regioselective acylation of carbazoles and indolines using molecular oxygen as the green oxidant. The reaction shows a broad substrate scope and good functional group tolerance. Late-stage functionalization of a carprofen drug derivative, further manipulation of products, and gram-scale synthesis of the acylated products were illustrated to show the versatility of the method.

Decarboxylative N-Formylation of Amines with Glyoxylic Acid Promoted by H2O2

A novel method for the synthesis of formamides through the decarboxylative N-formylation of amines with glyoxylic acid has been developed. This transformation provides an efficient protocol for the synthesis of various formamides with moderate to excellent yields, and it can accommodate a wide range of functional groups under metal free and base free conditions. In addition, the large-scale experiments and high chemoselectivity have shown great potential application of this strategy.

Construction of benzoheterocycles by the reaction of α-arylglyoxylic acids and ortho-functionalized aniline under mild and minimal conditions

This work describes an environmentally friendly method for the synthesis of benzoxazinones, quinoxalinones and benzothiazoles by the reaction of α-arylglyoxylic acids and ortho-functionalized aniline. In this reaction, no other reagents are needed except for reactants and solvents. The reaction was carried out at a mild temperature of 50 °C with only water and/or carbon dioxide as the by-product. Therefore, the reaction has high practical atom economy. In addition, this strategy could be scaled up to the gram level, and the natural product Cephamandole A could be synthesized on a mass scale.

Visible-Light-Driven Hydroacylation of Unactivated Alkenes Using Readily Available Acyl Donors

Herein, we report visible-light-driven hydroacylation of unactivated alkenes. We employed benzimidazolines as new acyl donors and achieved perfect regioselectivity, high functional-group tolerance, and excellent substrate generality. We also performed mechanistic experiments to elucidate the detailed reaction mechanism. This is the first example of (1) hydroacylation of unactivated alkenes using (2) easily prepared acyl donors under (3) visible-light irradiation. Our findings offer a new strategy to synthesize a wide variety of ketones under mild conditions.

Copper-Catalyzed C2- or C3-Thioglycosylation of Indoles with N-(Thioglycosides)succinimides: An Effective Strategy for the Total Synthesis of Isatindigotindolosides

Isatindigotindolosides, indoles containing a 1-S-β-glucopyranosyl unit at position C2, show promising bioactivity. Here, we report a copper-catalyzed C2- or C3-thioglycosylation of indoles with N-(thioglycosides)succinimides to construct indole alkaloid glucosides. This reaction is widely tolerant of functional groups, as various indoles and thioglycosides are suitable. It also provides a reliable method for performing late-stage modifications of natural products, such as gramine and melatonin. Total syntheses of isatindigotindolosides I and II were successfully accomplished using the C2-thioglycosylation reaction as a key step.

Direct Aroylation of Olefins through a Cobalt/Photoredox-Catalyzed Decarboxylative and Dehydrogenative Coupling with α-Oxo Acids

A photoredox/cobalt dual catalytic procedure has been developed that allows benzoylation of olefins. Here the photoredox catalyst effects the decarboxylation of α-ketoacids to form benzoyl radicals. After addition of this radical to styrenes, the cobalt catalyst abstracts a H-atom. Hydrogen evolution from the putative cobalt hydride intermediate allows a Heck-like aroylation without the need for a stoichiometric oxidant. Mechanistic studies reveal that electronically different styrenes lead to a curved Hammett plot, thus suggesting a change in product-determining step in the catalytic mechanism.

α-Acylation of Alkenes by a Single Photocatalyst

A direct strategy for the difunctionalization of alkenes, with acylation occurring at the more substituted alkene position, would be attractive for complex ketone synthesis. We report herein a reaction driven by a single photocatalyst that enables α-acylation in this way with the introduction of a fluoromethyl, alkyl, sulfonyl or thioether group at the β-position of the alkene with high chemo- and regioselectivity under extremely mild conditions. Crucial to the success of this method are rate differences in the kinetics of radical generation through single-electron transfer (SET) between different radical precursors and the excited photocatalyst (PC*). Thus, the β-position of the alkene is first occupied by the group derived from the radical precursor that can be generated most readily, and α-keto acids could be used as an electrophilic reagent for the α-acylation of alkenes.

Progress in C-C and C-Heteroatom Bonds Construction Using Alcohols as Acyl Precursors

Acyl moiety is a common structural unit in organic molecules, thus acylation methods have been widely explored to construct various functional compounds. While the traditional Friedel-Crafts acylation processes work to allow viable construction of arylketones under harsh acid conditions, recent progress on developing acylation methods focused on the new reactivity discovery by exploiting versatile and easily accessible acylating reagents. Of them, alcohols are cheap, have low toxicity, and are naturally abundant feedstocks; thus, they were recently used as ideal acyl precursors in molecule synthesis for ketones, esters, amides, etc. In this review, we display and discuss recent advances in employing alcohols as unusual acyl sources to form C-C and C-heteroatom bonds, with emphasis on the substrate scope, limitations, and mechanism.

Synthesis of remote fluoroalkenyl ketones by photo-induced ring-opening addition of cyclic alkoxy radicals to fluorinated alkenes

Fluoroalkenyl moieties are often used as carbonyl mimics in medicine preparation, and thus the development of facile routes for the synthesis of such compounds is of great importance. In this work, we report a photocatalytic ring-opening addition of cyclic alcohols to α-(trifluoromethyl)styrenes, which underwent a proton-coupled electron transfer and β-scission process, delivering a great variety of remote gem-difluoroalkenyl ketone derivatives. This methodology can also be applied in the reaction of gem-difluorostyrenes and 1,1,2-trifluorostyrenes to access monofluoro- and 1,2-difluoroalkenyl ketones.

(NH4)2S2O8-Mediated Metal-Free Decarboxylative Formylation/Acylation of α-Oxo/Ketoacids and Its Application to the Synthesis of Indole Alkaloids

A metal-free method for the formylation/acylation of indoles and β-carbolines with (NH₄)₂S₂O₈ via direct decarboxylative cross-coupling of α-oxo/ketoacids in moderate to good yields is described. The reaction occurs between ambient temperature and 40 °C under mild reaction conditions with commercially available starting materials. This methodology can be expanded to some biologically active indole alkaloids like pityriacitrins, eudistomins Y₁ and Y₃, and marinacarbolines A-D.

Visible-light-promoted decarboxylative radical cascade cyclization to acylated benzimidazo/indolo[2,1-a]isoquinolin-6(5H)-ones in water

A metal-free visible-light-induced decarboxylative radical addition/cyclization procedure at room temperature was described for the synthesis of acylated benzimidazo/indolo[2,1-a]isoquinolines. The procedure was prepared in water via a reaction of functionalized 2-arylbenzoimidazoles or 2,3-diarylindoles and α-oxocarboxylic acids in the presence of phenyliodine(iii) diacetate (PIDA) in one step under mild reaction conditions. In this procedure, traditional heating and metal reagents could be effectively avoided to access 1,4-dicarbonyl-containing benzimidazo/indolo[2,1-a]isoquinoline-6(5H)-ones in satisfactory yields.

Silver-catalyzed decarboxylative cyclization for the synthesis of substituted pyrazoles from 1,2-diaza-1,3-dienes and α-keto acids

A silver-catalyzed decarboxylative cyclization process has been developed for the synthesis of substituted pyrazoles from the readily available 1,2-diaza-1,3-dienes and α-keto acids. Under the optimized conditions, a series of multisubstituted pyrazoles were well prepared in moderate to good yields. In addition, the synthetic utility of this protocol has been demonstrated by synthesizing analogs of FDA approved drugs such as anti-inflammatory drug, lonazolac and antiobesity drug, rimonabant.

Rapid syntheses of N-fused heterocycles via acyl-transfer in heteroaryl ketones

The wide-ranging potencies of bioactive N-fused heterocycles inspire the development of synthetic transformations that simplify preparation of their complex, diverse structural motifs. Heteroaryl ketones are ubiquitous, readily available, and inexpensive molecular scaffolds, and are thus synthetically appealing as precursors in preparing N-fused heterocycles via intramolecular acyl-transfer. To best of our knowledge, acyl-transfer of unstrained heteroaryl ketones remains to be demonstrated. Here, we show an acyl transfer-annulation to convert heteroaryl ketones to N-fused heterocycles. Driven via aromatisation, the acyl of a heteroaryl ketone can be transferred from the carbon to the nitrogen of the corresponding heterocycle. The reaction commences with the spiroannulation of a heteroaryl ketone and an alkyl bromide, with the resulting spirocyclic intermediate undergoing aromatisation-driven intramolecular acyl transfer. The reaction conditions are optimised, with the reaction exhibiting a broad substrate scope in terms of the ketone and alkyl bromide. The utility of this protocol is further demonstrated via application to complex natural products and drug derivatives to yield heavily functionalised N-fused heterocycles.

Heteroaryl ketones are ubiquitous molecular scaffolds but seldom used as synthetic precusors. Here, the authors develop an acyl transfer-annulation to convert heteroaryl ketones to N-fused heterocycles, which are prevalent in bioactive molecules.

Metal-free three-component assemblies of anilines, α-keto acids and alkyl lactates for quinoline synthesis and their anti-inflammatory activity

A new and metal-free three-component method for the synthesis of 2,4-disubstituted quinolines via the reactions of anilines, α-keto acids and alkyl lactates is reported. The reactions proceed in the presence of p-toluene sulfonic acid (p-TSA) and tert-butyl peroxybenzoate (TBPB) to provide diverse quinoline products via the construction of new CC double, C-C single and CN double bonds without producing any organic mass-based side product. Notably, the anti-inflammatory activity of the quinolines has been investigated by measuring their ability to inhibit NO release by lipopolysaccharide (LPS) induced RAW264.7 cells, leading to the identification of 4i, 4t and 4x as potent anti-inflammatory compounds in vitro.

Visible-light-induced acylation/cyclization of active alkenes: facile access to acylated isoquinolinones

Nitrogen heterocycles, especially polycyclic compounds, are significant skeletons in valuable molecules. Herein, we developed an efficient and practical visible-light-induced acylation/cyclization of active alkenes with acyl oxime derivatives for constructing acylated indolo/benzimidazo-[2,1,a]isoquinolin-6(5H) ones. This reaction was compatible with various functional groups and a series of fused indole/imidazole skeletons were prepared in up to 95% yield at room temperature.

A Practically Unified Electrochemical Strategy for Ni-Catalyzed Decarboxylative Cross-Coupling of Aryl Trimethylammonium Salts

By merging electrocatalysis and nickel catalysis, a unified strategy has been successfully applied to achieve the decarboxylative cross-coupling of four types of α-oxocarboxylic acids and their derivatives with aryl trimethylammonium salts under mild conditions. Our strategy provides a practical way for preparing aryl ketones, amides, esters, or aldehydes.

Visible-Light-Induced Dual Acylation of Alkenes for the Construction of 3-Substituted Chroman-4-ones

Heterocyclic compounds, especially oxygen-containing heterocyclic compounds, are crucial moieties in bioactive compounds and drug leads. Substituted chroman-4-ones are a kind of the most significant structural skeletons. Herein, we report a visible-light-induced dual acylation of alkenes for constructing 3-substituted chroman-4-ones, which undergoes a radical tandem cyclization reaction through carbon-carbon bond cleavage of oxime esters by a nitrogen-centered radical strategy. A series of 3-substituted chroman-4-ones were prepared with up to 86% yield.