Iron-Catalyzed Carbonylation-Peroxidation of Alkenes with Aldehydes and Hydroperoxides

Oxidative Amidation of Ferrocenyl Aldehydes with Amines Catalyzed by Chalcogenised Fe3Se2(CO)9 Cluster: Direct Transformation of Aldehyde to Amides

With the interest and knowing the importance of ferrocenyl conjugates, a direct amidation of ferrocenyl aldehyde has been developed under feasible conditions. Varieties of amines has been oxidatively coupled with ferrocene aldehyde in the presence of highly economical and robustly stable iron chalcogenide ironcarbonyl clusters [Fe3E2(CO)9, E= S, Se, and Te] and TBHP. The reaction worked in greener solvent water at a moderate temperature of 70 °C and the ferrocenyl-amides in just 30 minutes. All the varieties of amines were found to be well tolerated for the present method, and due to the high medicinal importance of ferrocenyl-amides, sole focus of this report was concentrates on the synthesis of various new ferrocenyl-amides in good to excellent amounts.

Cu-Catalyzed Asymmetric Three-Component Radical Acylarylation of Vinylarenes with Aldehydes and Aryl Boronic Acids

The direct use of readily available aldehydes as acyl radical precursors has facilitated diverse three-component acylative difunctionalization reactions of alkenes, offering a powerful route to synthesize β-branched ketones. However, asymmetric three-component acylative difunctionalization of alkenes with aldehydes still remains elusive. Here we report a copper-catalyzed asymmetric three-component radical acylarylation of vinylarenes with aldehydes and aryl boronic acids. This method begins with acyl radical formation from an aldehyde via hydrogen atom transfer. The acyl radical adds to the alkene, forming a new benzylic radical that then undergoes copper-catalyzed enantioselective arylation. A chiral binaphthyl-tethered bisoxazoline ligand is essential for achieving high stereocontrol. This strategy enables the direct synthesis of a range of synthetically valuable chiral β,β-diaryl ketones from aldehydes and vinylarenes.

Advances in radical peroxidation with hydroperoxides

Organic peroxides have become sought-after functionalities, particularly following the multi-tone consumption in polymer production and success in medicinal chemistry. The selective introduction of a peroxide fragment at different positions on the target molecule is a priority in the modern reaction design. The pioneering Kharasch-Sosnovsky peroxidation became the basic universal platform for the development of peroxidation methods, with its great potential for rapid generation of complexity due to the ability to couple the resulting free radicals with a wide range of partners. This review discusses the recent advances in the radical Kharasch-type functionalization of organic molecules with OOR fragment including free-component radical couplings. The discussion has been structured by the type of the substrate of radical peroxidation: C(sp 3 )-H substrates; aromatic systems; compounds with unsaturated C-C or C-Het bonds.

Photoinduced fluoroalkylation-peroxidation of alkenes enabled by ligand-to-iron charge transfer mediated decarboxylation

We report here a photoinduced iron-catalyzed fluoroalkylation-peroxidation of activated and/or unactivated alkenes with fluoroalkyl carboxylic acids and hydroperoxide. The ligand-to-iron charge transfer strategy effectively overcomes the high redox potential of the fluoroalkyl carboxylic acids, facilitating the difunctionalization reaction to occur smoothly under mild reaction conditions. The late-stage functionalization of drug and natural product derivatives was also demonstrated.

Visible Light-Mediated Co(II) Catalyzed Synthesis of α,β-Epoxy Ketones by Oxidative Coupling of Alkenes and Aldehydes in Water

A one-step, two-component visible light-mediated CoCl2·6H2O-catalyzed oxidative acylation of alkenes by aldehydes to synthesize α,β-epoxy ketone has been achieved in water at room temperature. The photocatalytic activity of Co(II) presented a remarkable achievement for synthesis of α,β-epoxy ketones from aldehydes and olefins, with a wide substrate compatibility including aromatic, heteroaromatic and aliphatic aldehydes, styrenes with both electron-donating and withdrawing groups, α-substituted styrenes, stilbene, acrylates, and even the challenging unactivated aliphatic alkenes. Mechanistic studies including radical trapping experiments, intermediate detection by GCMS, Hammett analysis, and DFT studies unveil the nature of the photocatalytic pathway.

Self-Catalyzed, Visible-Light-Induced Selective C3-H Aroylation of Quinoxalin-2(1H)-ones with Arylaldehydes by Air as an Oxidant

A self-catalyzed, visible-light-induced, directly selective C3-H aroylation of quinoxalin-2(1H)-ones via energy transfer and hydrogen atom transfer (HAT) catalysis has been developed. The method is highly atom-economical, eco-friendly, and easy to handle. Notably, the reaction proceeded efficiently with ambient air as the sole oxidant at room temperature.

Regioselective synthesis of N-containing polycyclic compounds via radical annulation cyclization of 1,7-dienes with aldehydes

A convenient method for oxidant-promoted radical cascade acylation or decarbonylative alkylation of 1,7-dienes with aldehydes has been established. This method allows for the rapid construction of N-containing polycyclic skeletons in a highly regio- and stereoselective manner. This transformation provides a simple and efficient method for the preparation of a range of tetrahydro-6H-indeno[2,1-c]quinolinone derivatives by sequential formation of three new carbon-carbon bonds. Additionally, this radical cascade cyclization can selectively convert aldehydes into aroyl/primary aliphatic acyl radicals and secondary or tertiary alkyl radicals.

Photoredox-Catalyzed 1,4-Peroxidation-Sulfonylation of Enynones: A Three-Component Radical Coupling Approach for the Synthesis of Highly Functionalized Allenes

An Eosin Y-catalyzed visible light-promoted 1,4-peroxidation-sulfonylation of enynones was achieved to give tetrasubstituted allenes. The photoredox catalysis of Eosin Y allowed the concomitant formation of peroxy and sulfonyl radicals, where the preferential peroxy radical addition to the alkene moiety of enynones resulted in the subsequent α-keto radical-sulfonyl radical cross couplings. The developed photoredox catalysis of Eosin Y demonstrates a regioselective 1,4-diradical addition strategy, opening up a new possibility of diradical functionalization of conjugate systems.

Photocatalytic Sulfonyl Peroxidation of Alkenes via Deamination of N-Sulfonyl Ketimines

A photocatalytic three-component sulfonyl peroxidation of alkenes with N-sulfonyl ketimines and tert-butyl hydroperoxide is reported. The reaction takes place via the photoinduced EnT process, which allows the efficient synthesis of a variety of β-peroxyl sulfones under mild reaction conditions in the absence of a transition metal catalyst. The downstream derivatizations of the peroxides were also performed. Furthermore, the utility of this protocol was manifested by the synthesis of 11β-HSD1 inhibitor and the antiprostate cancer drug bicalutamide.

Metal-catalyzed asymmetric reactions enabled by organic peroxides

As a class of multifunctional reagents, organic peroxides play vital roles in the chemical industry, pharmaceutical synthesis and polymerization reactions. Metal-catalyzed asymmetric catalysis has emerged as one of the most straightforward and efficient strategies to construct enantioenriched molecules, and an increasing number of metal-catalyzed asymmetric reactions enabled by organic peroxides have been disclosed by researchers in recent years. Despite remarkable progress, the types of asymmetric reactions facilitated by organic peroxides remain limited and the catalysis systems need to be further broadened. To the best of our knowledge, there is still no review devoted to summarizing the reactions from this perspective. In this review, we will endeavor to highlight the advances in metal-catalyzed asymmetric reactions enabled by organic peroxides. We hope that this survey will summarize the functions of organic peroxides in catalytic reactions, improve the understanding of these compounds and inspire future developments in this area.

Dual functional profluorescent nitroxides for the detection of reactive oxygen species and inhibition of collagen degradation during reassembly

High content of reactive oxygen species (ROS) in the human body leads to oxidative stress and serious health problems, such as cancer and cardiovascular or bone diseases. It is also one of the agents that cause collagen damage. Herein, detection of ROS, scavenging of formed carbon-centered radicals and inhibition of collagen fragmentation were performed in a single operation using newly synthesized profluorescent nitroxide PN1via a switch-on approach. Reassembly of acid soluble collagen (ASC) in the presence of hydroxyl and hydroperoxyl radicals, representatives of ROS, was monitored to study the efficiency of the PN1 probe. Self-assembly curves of collagen fibril solution were in accordance with differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) observations, and indicated that PN1 efficiently inhibited the collagen chain scission. In order to prevent the leakage of the probe in materials, a PN2 monomer was successfully incorporated with MMA to form a profluorescent copolymer probe. Furthermore, PN1 and PN2-MMA copolymer probes offered high sensitivity of detection of ROS in the presence of collagen fibrils with detection limits of 1.1 and 2.7 μM, respectively. The mechanism of ROS detection and inhibition of collagen degradation by profluorescent nitroxides was proposed.

Dealkenylative Functionalizations: Conversion of Alkene C(sp3)-C(sp2) Bonds into C(sp3)-X Bonds via Redox-Based Radical Processes

This review highlights the history and recent advances in dealkenylative functionalization. Through this deconstructive strategy, radical functionalizations occur under mild, robust conditions. The reactions described proceed with high efficiency, good stereoselectivity, tolerate many functional groups, and are completed within a matter of minutes. By cleaving the C(sp3)-C(sp2) bond of terpenes and terpenoid-derived precursors, rapid diversification of natural products is possible.

Access to Polyheterocyclic Compounds through Iron(II)-Mediated Radical Cascade Cyclization Utilizing 2-Ethynylbenzaldehydes and Aryl Isonitriles

An oxidative radical cascade addition cyclization approach for the synthesis of quinoline-based π-extended polyheterocyclic compounds is reported. Eco-friendly iron catalysis and inexpensive tert-butylhydroperoxide (TBHP) as the oxidant have been utilized in the transformation of various readily available ortho-alkynylated aromatic aldehydes as radical precursors with aryl isonitriles as radical acceptors. Indole and thiophene-based carbaldehydes allow the preparation of quinolines that are π-conjugated with an additional heteroarene moiety in a single sequence by applying the introduced method.

CuII-Catalyzed cis-Selective Synthesis of Ketoepoxides from Phenacyl Bromides and Water

A verity of α,β-ketoepoxides was synthesized using a Cu^II-catalyzed oxidative C-C/O-C coupled cyclization strategy with high yield and cis-selectivity. Water is used as the source of oxygen and phenacyl bromide as the carbon in the valuable epoxides. The self-coupling method was extended to cross-coupling between phenacyl bromides with benzyl bromides. A high cis-diastereoselectivity was observed in all the synthesized ketoepoxides. Control experiments and density functional theory (DFT) study were performed to understand the Cu^II-Cu^I transition mechanism.

TBAI-Catalyzed Regioselective Hydroxyperoxidation of 1-Aryl/Alkyl-1,3-dienes

An efficient, mild, and economical approach for regioselective synthesis of 4-aryl/alkyl-1-peroxy-but-3-en-2-ols from 1-substituted-1,3-butadienes using hydroperoxides and catalyzed by TBAI has been developed. This method can be executed in a simple operation with no dry conditions required and having tolerance to a wide range of substrates to access corresponding hydroxyperoxidates in good yields. Thus, an excellent regioselective orthogonal dioxygenation in a diene system has been achieved.

Photoredox-Catalyzed Acyl Lactonization of Alkenes with Aldehydes: Synthesis of Acyl Lactones

An acyl lactonization of alkenes with aldehydes under visible-light photoredox catalysis is described. With the protocol, a broad scope of alkenoic acids and aldehydes could be compatible and good functional group tolerance is obtained. A series of acyl lactones are obtained with isolated yields ranging from 50-95%. Mechanistic studies revealed that the transformation should proceed via a radical chain process.

Synthesis of ester-functionalized indolo[2,1-a]isoquinolines via iron-catalyzed radical cascade cyclization of 2-aryl-N-acryloyl indoles with carbazates

An FeCl₂·4H₂O-catalyzed oxidative alkoxycarbonylation/cyclization reaction of 2-aryl-N-acryloyl indoles with carbazates leading to ester-functionalized indolo[2,1-a]isoquinoline derivatives has been developed. The reaction features mild reaction conditions and broad functional group tolerance. Moreover, the ester group could be easily converted to the corresponding free acid and alcohol, and has high potential applications in organic and pharmaceutical synthesis. A radical pathway was proposed to explain this experiment.

Regioselective Approach to β-Peroxyl Alcohols and Ethers from Alkenes

A different regioselective three-component reaction of alkenes, oxygen sources, and hydroperoxides mediated by ammonium iodine to α-oxyperoxidates has been developed. Mechanistic studies demonstrated that regioselective radical addition and subsequent S_N2 nucleophilic substitution were possible for the formation of products. In addition to the traditional pathway of S_N2 reaction, that is, where nucleophiles attack the α-C atoms at the back side, an additional unusual transition configuration with the H₂O molecule attacking the α-C atom at the front side was obtained.

Access to 3,3'-disubstituted peroxyoxindole derivatives and α-peroxyamides via azaoxyallyl cation-guided addition of hydroperoxides

Herein, a transition metal-free approach for access to 3,3'-disubstituted peroxyoxindole is disclosed, which harnesses a transient azaoxyallyl cation. This strategy is also applicable to the synthesis of structurally diverse α-peroxycarboxylic acid surrogates. The method exhibits good functional group tolerance and is suitable for generating a library of peroxy-containing compounds.

Photocatalytic 1,2-oxo-alkylation reaction of styrenes with diazoacetates

We report on the photocatalytic 1,2-difunctionalization reaction of styrenes with acceptor-only diazoalkanes. In the presence of DABCO and tBuOOH, the carbene reactivity of diazoalkanes can be suppressed and a 1,2 oxo-alkylation reaction can be achieved (32 examples, up to 94% yield) without the formation of cyclopropane by-products via the formation of radical intermediates from ethyl diazoacetate.

Copper-Catalyzed Three-Component Germyl Peroxidation of Alkenes

The concurrent incorporation of a germyl fragment and another functional group (beyond the hydrogen atom) across the C═C double bond is a highly appealing yet challenging task. Herein we demonstrate the efficient germyl peroxidation of alkenes with germanium hydrides and tert-butyl hydroperoxide via a copper-catalyzed three-component radical relay strategy. This protocol exhibits excellent functional group tolerance and exquisite chemo- and regioselectivity under mild conditions and represents a rare example of constructing synthetically challenging metal-embedded organic peroxides.

Metal-Organic Framework-Encapsulated Anthraquinone for Efficient Photocatalytic Hydrogen Atom Transfer

Anthraquinone (AQ) as an effective hydrogen atom transfer catalyst was limited in photocatalysis application due to the dimerization of reduced AQ. Sr-NDI@AQ, encapsulating AQ into the channel of Sr-NDI, paved a new way for solving the problem of dimerization of reduced AQ and improving the catalytic efficiency owing to the fast electron transfer from reduced AQ to the ligand through host-guest interaction. The structure of Sr-NDI@AQ was determined by single-crystal X-ray diffraction, and the value for distance and torsion angle between the ligand and AQ was calculated. The photochemical and electrochemical properties for Sr-NDI@AQ were characterized through a series of experiments. The coupling reaction between aldehyde and phenyl vinyl sulfone and photoacetalization reaction were carried out, displaying the improving catalytic efficiency of Sr-NDI@AQ compared to Sr-NDI and AQ. The reaction mechanisms were proposed through radical capture and electron paramagnetic resonance experiments.

Oxidant-Switched Palladium-Catalyzed Regioselective Mono- versus Bis-ortho-Aroylation of 1-Aryl-1H-indazoles with Aldehydes via C-H Bond Activation

A highly efficient oxidant-switched palladium-catalyzed regioselective C_(sp²)-H/C_(sp²)-H cross-dehydrogenative coupling (CDC) for direct mono/bis-ortho-aroylation of substituted 1-phenyl-1H-indazoles 1a-j with various substituted aldehydes 3a-t via C_(sp²)-H bond activation has been developed. In this study, Pd-catalyzed chelation-assisted mono- or bis-aroylation of substituted 1-phenyl-1H-indazoles depends on the type of oxidant being used for the CDC reaction. While mono-ortho-aroylation of substituted 1-phenyl-1H-indazole was obtained using dicumylperoxide (DCP) as the oxidant, the bis-ortho-aroylation product has been afforded by the use of tert-butyl hydroperoxide (TBHP). Regardless of the greater activity at the C-3 position of 1H-indazoles, the greater coordinating capacity of the N atom directed the aroylating group to the ortho position, leaving behind the nondirected metalation pathway. The Pd-catalyzed operationally simplified methodology proceeded in the presence of oxidants with either DCP or TBHP in dichloroethane as the solvent at 110 °C for 16 h, which generated a miscellaneous variety of monosubstituted o-benzoyl/acyl-1-aryl-1H-indazoles 4a-t/5a-i and bis-substituted o-benzoyl-1-aryl-1H-indazoles 6a-j in ≤88% yields. The probable mechanistic pathway involves a free radical chelation-assisted approach that could be accomplished by the addition of an in situ-generated oxidant-promoted benzoyl/acyl radical to the ortho position of 1-phenyl-1H-indazoles. A wide range of substrates, a high functional group tolerance, gram-scale synthesis, control/competitive experiments, and a variety of synthetic applications further exemplify the versatility of the developed methodology.

β-Perfluoroalkyl Peroxides as Fluorinated C3-Building Blocks for the Construction of Benzo[4,5]imidazo[1,2-a]pyridines

An efficient and selective protocol for the synthesis of perfluoroalkyl-group-substituted benzo[4,5]imidazo[1,2-a]pyridines has been developed in which β-perfluoroalkyl peroxides act as novel fluorinated C3-building blocks to implement regioselective [3 + 3] annulation with 2-cyanomethyl benzimidazole under metal-free conditions. The application of the synthesized perfluoroalkylated BIPs as potent anticancer reagents versus the nonfluorinated ones demonstrated the biological utility of this method.

Concomitant Functionalization of Two Different Ketones by Merging Brønsted Acid Catalysis and Radical Relay Coupling

In previous literature, incorporation of functional groups at the α-position of unactivated carbonyl compounds was mainly restricted to one kind of corresponding precursors. Herein, we report the concomitant functionalization of...

FeIII/TBHP mediated remote C–O bond construction of 8-aminoquinolines: access to methoxylation and cyanomethoxylation

The C5 regioselective methoxylation and cyanomethoxylation of 8-aminoquinolines were achieved under FeIII/TBHP system by tuning the temperature and solvent. TBHP was investigated as an “oxygen” source in the ether bond formation for the first time.

Metal-/solvent-free oxidative [4+2]/[3+2] annulation of 2-ethynylbenzaldehydes with arylalkenes: Facile synthesis of benzo[a]fluoren-5-ones

We report here a DTBP-mediated oxidative [4+2]/[3+2] annulation between 2-alkynylbenzaldehydes and terminal arylalkenes enabled by aldehyde C(sp2)-H functionalization for assembling a range of benzo[a]fluoren-5-ones with high step-economy, simple operations under...

DMF-Assisted Radical Cyclization of o-Isocyanodiaryl Ethers via 1,5-Aryl Migration: Construction of 2-Arylbenzoxazoles

A novel DMF-assisted radical cyclization of o-isocyanodiaryl ethers via 1,5-aryl migration has been developed for the synthesis of a series of 2-arylbenzoxazoles by the FeCl₃/TBHP/Et₃N catalytic system in DMF. However, N,N-dimethylbenzo[d]thiazole-2-carboxamide and N,N-dimethylbenzo[d]selenazole-2-carboxamide were obtained from the corresponding substrate 2-isocyanophenyl p-methoxyphenyl thioether and 2-isocyanodiphenyl selenoether under the same conditions. A possible mechanism may involve aryl 1,5-migration and DMF-assisted radical cyclization of o-isocyanodiaryl ethers.

The construction of benzimidazo[2,1-a]isoquinolin-6(5H)-ones from N-methacryloyl-2-phenylbenzoimidazoles through radical strategies

Benzimidazo[2,1-a]isoquinolin-6(5H)-one constitutes a structurally unique class of tetracyclic N-heterocycles that are found throughout a myriad of biologically active natural products, pharmaceutical compounds, and functional materials. Various synthetic routes for the preparation of benzimidazo[2,1-a]isoquinolin-6(5H)-ones have been reported. In particular, the use of N-methacryloyl-2-phenylbenzoimidazoles to construct benzimidazo[2,1-a]isoquinolin-6(5H)-ones through various radical strategies have attracted widespread attention due to the versatility and simple preparation of raw materials, as well as the step-economy and mild reaction conditions. Using representative examples, we highlight significant progress in the synthesis of benzimidazo[2,1-a]isoquinolin-6(5H)-ones, including the selection of the catalytic system, substrate scope, mechanistic understanding, and applications. The contents of this review focus on the development of C-, S-, P-, and Si-centered radical addition-intramolecular cyclization strategies.

Visible-Light-Induced Transition-Metal-Free Nitrogen-Centered Radical Strategy for the Synthesis of 2-Acylated 9H-Pyrrolo[1,2-a]indoles

A convenient and efficient visible-light-induced tandem acylation/cyclization of N-propargylindoles with aryl- or alkyl-substituted acyl oxime esters for the synthesis of 2-acyl-substituted 9H-pyrrolo[1,2-a]indoles under transition-metal-free conditions, which proceeds via nitrogen-centered radical-mediated cleavage of the C-C σ-bond in acyl oxime esters, is established. The aryl or alkyl acyl radicals, which come from acyl oxime esters, attack the C-C triple bonds in N-propargylindoles and then go through intramolecular cyclization/isomerization.

Iron-Catalyzed Ring-Opening Reactions of Cyclopropanols with Alkenes and TBHP: Synthesis of 5-Oxo Peroxides

The ring opening of cyclopropanols is rarely used in multicomponent reactions. Herein we report the three-component reaction of cyclopropanols with alkenes and tert-butyl hydroperoxide (TBHP) catalyzed by an iron catalyst. This protocol enables the incorporation of both the β-carbonyl fragment and a peroxy unit across the C═C double bond regioselectively, thus allowing an efficient, facile access to 5-oxo peroxides. Modification of the biologically active molecules and various downstream derivatizations of the peroxides are also demonstrated.

Iron-catalysed radical cyclization to synthesize germanium-substituted indolo[2,1-a]isoquinolin-6(5H)-ones and indolin-2-ones

A simple and efficient strategy for iron-catalysed cascade radical cyclization was developed, by which an array of germanium-substituted indolo[2,1-a]isoquinolin-6(5H)-ones and indolin-2-ones were obtained in one pot with germanium hydrides as radical precursors. A rapid intramolecular radical trapping mode enabled the selective arylgermylation of alkenes over the prevalent hydrogermylation reaction.

A Mn-catalyzed remote C(sp3)-H bond peroxidation triggered by radical trifluoromethylation of unactivated alkenes

A manganese-catalyzed radical relay strategy for the remote trifluoromethylation-peroxidation of unactivated alkenes is disclosed. The electrophilic CF3 group was added to the C[double bond, length as m-dash]C double bonds to afford remote C-centered radicals upon 1,5-HAT, which could be efficiently trapped by Mnn+1OOBu-t species to deliver 1,6-difunctionalized products selectively under mild conditions. t-BuOOH serves as both the oxidant and the peroxy precursor in this transformation.

Hydroperoxidations of Alkenes using Cobalt Picolinate Catalysts

Hydroperoxides were synthesized in one step from various alkenes using Co(pic)2 as the catalyst with molecular oxygen and tetramethyldisiloxane (TMDSO). The hydration product could be obtained using a modified catalyst, Co(3-mepic)2, with molecular oxygen and phenylsilane. Formation of hydroperoxides occurred through a rapid Co-O bond metathesis of a peroxycobalt compound with isopropanol.

Recent advances in acyl radical enabled reactions between aldehydes and alkenes

Radical-mediated functionalization of alkenes has been emerging as an elegant and straightforward protocol to increase molecule complexity. Moreover, the abstraction of a hydrogen atom from aldehydes to afford acyl radicals has evolved as a rising star due to its high atom-economy and the ready availability of aldehydes. Considering the great influence and synthetic potential of acyl radical enabled reactions between aldehydes and alkenes, we provide a summary of the state of the art in this field with a specific emphasis on the working models and corresponding mechanisms. The discussion is divided according to the kind of alkenes and reaction type.

Atomically Dispersed Pt-N3C1 Sites Enabling Efficient and Selective Electrocatalytic C-C Bond Cleavage in Lignin Models under Ambient Conditions

Selective cleavage of C-C linkages is the key and a challenge for lignin degradation to harvest value-added aromatic compounds. To this end, electrocatalytic oxidation presents a promising technique by virtue of mild reaction conditions and strong sustainability. However, the existing electrocatalysts (traditional bulk metal and metal oxides) for C-C bond oxidative cleavage suffer from poor selectivity and low product yields. We show for the first time that atomically dispersed Pt-N₃C₁ sites planted on nitrogen-doped carbon nanotubes (Pt₁/N-CNTs), constructed via a stepwise polymerization-carbonization-electrostatic adsorption strategy, are highly active and selective toward C_α-C_β bond cleavage in β-O-4 model compounds under ambient conditions. Pt₁/N-CNTs exhibits 99% substrate conversion with 81% yield of benzaldehyde, which is exceptional and unprecedented compared with previously reported electrocatalysts. Moreover, Pt₁/N-CNTs using only 0.41 wt % Pt achieved a much higher benzaldehyde yield than those of the state-of-the-art bulk Pt electrode (100 wt % Pt) and commercial Pt/C catalyst (20 wt % Pt). Systematic experimental investigation together with density functional theory (DFT) calculation suggests that the superior performance of Pt₁/N-CNTs arises from the atomically dispersed Pt-N₃C₁ sites facilitating the formation of a key C_β radical intermediate, further inducing a radical/radical cross-coupling path to break the C_α-C_β bond. This work opens up opportunities in lignin valorization via a green and sustainable electrochemical route with ultralow noble metal usage.

Oxidative alkylation/alkynylation of terminal alkenes via alkylaldehyde decarbonylation and 1,2-alkynyl migration

A metal-free oxidative alkene alkylation/alkynylation of 1,4-enyn-3-ols with alkylaldehydes has been achieved, which offers a general access to the challenging quaternary carbon-containing but-3-yn-1-ones. The method features excellent functional group tolerance, broad substrate scope and exquisite selectivity, and provides a strategy for the difunctionalization of functional alkenes and utilization of alkylaldehydes as alkylating reagents through decarbonylation and 1,2-alkynyl migration.

Peroxide- and transition metal-free electrochemical synthesis of α,β-epoxy ketones

A novel electrochemical method for the synthesis of α,β-epoxy ketones is reported. With KI as the redox mediator, methyl ketones reacted with aldehydes under peroxide- and transition metal-free electrolytic conditions and afforded α,β-epoxy ketones in one pot (36 examples, 52-90% yield). This safe and environmental-friendly method has a broad substrate scope and can readily provide a variety of α,β-epoxy ketones in gram-scales for evaluation of their anti-cancer activities.