Cu(I)-catalysed chemo-, regio-, and stereoselective radical 1,2-carboalkynylation with two different terminal alkynes

Transition-metal-catalysed asymmetric multicomponent reactions with two similar substrates often suffer from the lack of strategies to control the chemo-, regio-, and stereoselectivity of these substrates due to the close similarity in the chemical structures and properties of each reagent. Here, we describe a Cu(I)-catalysed asymmetric radical 1,2-carboalkynylation of two different terminal alkynes and alkyl halides with high chemo-, regio-, and stereoselectivity by using sterically bulky chiral tridentate anionic N,N,P-ligands and modulating alkynes with different electronic properties to circumvent above-mentioned challenges. This method features good substrate scope, high functional group tolerance of two different terminal alkynes, and diverse alkyl halides, providing universal access to a series of useful axially chiral 1,3-enyne building blocks.

Copper-catalyzed three-component radical aminoazolation of vinylarenes with N-fluorobenzenesulfonimide and trimethylsilylazole derivatives

A copper-catalyzed three-component radical aminoazolation of vinylarenes with N-fluorobenzenesulfonimide (NFSI) and trimethylsilylazole derivatives has been developed. This methodology provides an efficient and straightforward approach to generate various β-sulfoamino azoles in good to excellent yields. The protocol features exclusive chemo- and regioselectivity, and excellent functional group tolerance under mild conditions.

Photoinduced Copper-Catalyzed Regio- and Diastereoselective Multicomponent [3 + 2 + 1] Radical Cyclization To Access Tetrahydropyridines

The use of simple raw materials to construct complex piperidine scaffolds via multicomponent reactions is highly desirable from the perspectives of atom and step-economy. In this Letter, we present a photoinduced copper-catalyzed three- or four-component [3 + 2 + 1] radical cyclization, utilizing inexpensive and readily available feedstock amines, alkynes, and aldehydes, to synthesize multisubstituted bicyclic or spirocyclic tetrahydropyridines. This method is notable for its mild conditions, atom-economic approach, excellent regio- and diastereoselectivity, and the simultaneous activation of two α-amino C(sp3)-H bonds, resulting in the formation of three C-C bonds and one C-N bond in a single step. Mechanistic studies suggest that the α-aminoalkyl radical is the key intermediate in this reaction, which undergoes sequential radical addition, 1,5-HAT, and 6-exo-trig-type radical cyclization.

Kharasch-Type Haloalkylation of Alkenes by Photoinduced Copper Catalysis

The simultaneous construction of C-C and C-X bonds in a single step facilitates multistep synthesis through rapid carbon chain growth and subsequent transformations of halide functionalities. Traditional Kharasch addition requires simple polyhalogenated compounds or those with electron-withdrawing groups at the α-carbon. Herein, we present a Kharasch-type reaction utilizing a broad range of carboxylic acid-derived redox-active esters as the alkyl source, which enables the efficient introduction of highly functionalized alkyl groups. Our method produces α-halo carbonyls that enable versatile nucleophilic substitutions for synthesizing valuable compounds, such as unnatural α-amino acids.

Heterogeneous g-C3N4/NaI Dual Catalytic Difunctionalization of Alkenes with Heteroarenes and Methyl Carbazate under Visible Light

Herein, a photoinduced heterogeneous catalytic system merging g-C3N4 and NaI has been established for the difunctionalization of alkenes in conjunction with heteroarenes and methyl carbazate. This approach is notable for its broad substrate tolerance, encompassing a wide range of alkenes and heteroarenes and leading to the formation of the corresponding esters with moderate to good yields. Additionally, the scalability of the synthetic process and the versatility of the product transformations have been illustrated, highlighting its potential for practical application in organic synthesis.

NIS-promoted carbochalcogenation of styrenes: regioselective C-3 alkylation of pyrazolo[1,5-a]pyrimidines

An N-iodosuccinimide (NIS) mediated transition metal and solvent-free, regioselective multicomponent cascade reaction is developed for the C-3 alkylation of pyrazolo[1,5-a]pyrimidines via a three-component reaction of styrenes, diaryl dichalcogenides and pyrazolo[1,5-a]pyrimidines. This operationally simple, cost-effective and rapid reaction furnishes C-3 functionalized pyrazolo[1,5-a]pyrimidines in good to excellent yields. The reaction is scalable and operates via an electrophilic substitution mechanism.

Copper-Catalyzed Enantioselective Three-Component Carboamidation of Styrenes with Alkanes and Amides

Efficient assembly of valuable chiral molecules from readily available and low-cost chemical feedstocks remains one of the most challenging tasks in synthetic chemistry today. Radical-mediated three-component carboamination of alkenes offers an attractive strategy for addressing this challenge. However, most existing reports focus on racemic examples and are largely limited to activated alkenes, preactivated alkylation reagents, or sufficiently active nucleophiles. Herein, we report a highly enantioselective three-component carboamidation of styrenes with unactivated alkanes and weakly nucleophilic amides. Enantioselective control is achieved by using chiral cationic copper catalysts. This method enables the synthesis of a variety of optically active amides with excellent enantioselectivity. Mechanistic studies reveal that the reaction proceeds via hydrogen atom transfer from the alkane followed by radical addition to the olefin.

Enhanced Pyridine-Oxazoline Ligand-Enabled Pd(II)-Catalyzed Aminoacetoxylation of Alkenes for the Asymmetric Synthesis of Biaryl-Bridged 7-Membered N-Heterocycles and Atropisomers

A new class of binaphthyl unit-enhanced pyridine-oxazoline ligands was developed to promote the Pd-catalyzed enantioselective intramolecular 7-exo aminoacetoxylation of unactivated biaryl alkenes. Biaryl-bridged 7-membered N-heterocycles bearing a chiral center were obtained in good yields with excellent enantioselectivities (up to 99:1 er). Computational investigations on a series of biaryl-bridged 7-membered rings provided insights into the rotational barrier of the potentially chiral biaryl unit by the substituent effect including the heteroatom, the protecting group, and the chiral center. The kinetic resolution of racemic axially chiral biaryls via intramolecular enantioselective aminoacetoxylation of alkenes has also been achieved, affording previously inaccessible biaryl-bridged 7-membered N-heterocycles bearing both a chiral center and a chiral axis, as well as axially chiral biaryl amino alcohols.

Nickel-Catalyzed 1,1-Carboboration of Polysubstituted Internal Alkenes

Herein, we report a nickel-catalyzed 1,1-carboboration of di- and trisubstituted alkenyl boronates through a chain-walking strategy. This reaction effectively addresses the polarity-mismatch problem via ligand control, enabling the coupling of various carbon-based electrophiles while accommodating a broad range of functional groups. The approach yields diverse tetrasubstituted carbon gem-diboronate derivatives with exceptional regioselectivity. The synthetic utility of this method is further demonstrated through the concise synthesis of high-value bioactive molecules.

An Atomically Dispersed Mn Photocatalyst for Vicinal Dichlorination of Nonactivated Alkenes

A novel Mn-based single-atom photocatalyst is disclosed in this study, designed for the dichlorination of alkenes to achieve vicinal dichlorinated products using N-chlorosuccinimide as a mild chlorinating agent, which have widespread applications as pest controlling agents, polymers, flame retardants, and pharmaceuticals. In developing this innovative catalyst, we achieved the atomic dispersion of Mn on aryl-amino-substituted graphitic carbon nitride (f-C3N4). This marks the first instance of a heterogeneous version, offering an operationally simple, sustainable, and efficient pathway for dichlorination of alkenes, including drugs, bioactive compounds, and natural products. This material was extensively characterized by using techniques such as UV-vis spectroscopy, X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), magic-angle spinning (MAS), and solid-state nuclear magnetic resonance (ssNMR) spectroscopy to understand it at the atomic level. Furthermore, mechanistic studies based on multiscale molecular modeling, combining classical reactive molecular dynamics (RMD) simulations and quantum chemistry (QC) calculations, illustrated that the controlled formation of Cl radicals from the in situ formed Mn-Cl bond is responsible for the dichlorination reaction of alkenes. In addition, gram-scale and reusability tests were also performed to demonstrate the applicability of this approach on an industrial scale.

Cu-catalyzed photoredox chlorotrifluoromethylation of polysubstituted alkenes and pharmacological evaluation

A visible-light-mediated chlorotrifluoromethylation catalyzed by a copper-based photo-redox catalyst of internal alkenes is reported. The reaction proceeds with complete regioselectivity under mild reaction conditions using commercially available F3CSO2Cl as both the trifluoromethyl and chlorine source, leading to the synthesis of added-value chemicals with atom-economy. A vast array of internal alkenes were functionalized in decent to good yields, highlighting a great tolerance to various functional groups. A radical process starting from a single electron reduction of F3CSO2Cl with an excited copper catalyst was evidenced, and the synthetic utility of our products was showcased by the synthesis of valuable molecules such as α-trifluoromethylated amides, α-trifluoromethylated-β-aminoamides, and trifluoromethyl alkenes. In addition, the library was evaluated in vitro for its cytotoxicity against lung carcinoma (A549) and colorectal adenocarcinoma (DLD-1) cell lines, and for its antifungal and antibacterial activities against C. albicans, E. coli and S. aureus strains, respectively. Compounds 2a, 2m, 2n, and 2o demonstrated anticancer activities, while compounds 2a, 6g, and 6h exhibited weak antibacterial activities, underscoring the therapeutic potential of this class of molecules and suggesting opportunities for further optimization.

Rh-Catalyzed and Self-Directed Aromatic C-H Activation of Enaminones to Divergent Alkenylated and Annulated Compounds

By means of simple Rh catalysis, the direct activation of the ortho-C-H bond in aryl enaminones has been realized with the enaminone structure as a traceless directing fragment. The products resulting from C-H alkenylation and further annulation via intramolecular C-H bond addition could be accessed depending upon the structure of alkenes. The annulated products could be used for the easy synthesis of valuable 2-aza-fluorenones in a one-pot operation by employing NH4OAc.

Electrochemical 1,2-Alkylarylation of Styrenes with Malonates and N-Heteroarenes via Direct C(sp3)-H/C(sp2)-H Functionalization

A general and atom-economical electrochemical dehydrogenative method for the intermolecular 1,2-alkylarylation of styrenes with malonates and nucleophilic N-heteroarenes (including indoles and pyrroles) has been developed. This transformation provides a regioselective route to construct highly valuable 1,1-diarylalkanes enabled by C(sp3)-H/C(sp2)-H functionalization under mild conditions, and H2 is the only theoretical byproduct. Mechanistic studies indicated that the reaction proceeded through the oxidative of the C(sp3)-H bond to generate alkyl radical, radical addition across the C═C bond, single electron oxidation and C(sp2)-H functionalization cascades.

TBHP-Promoted Trifluoromethyl-difluoromethylthiolation of Unactivated Alkenes with CF3SO2Na and PhSO2SCF2H

A TBHP-promoted trifluoromethyl-difluoromethylthiolation of alkenes was reported. Langlois' reagent was used as a stable and inexpensive trifluoromethyl source. In the presence of TBHP, the trifluoromethyl radical generated reacted with alkenes, achieving a new alkyl radical, which could be trapped by PhSO2SCF2H, forming C-C and C-S bonds in one step and incorporating trifluoromethyl and difluoromethylthio groups. The mild conditions and broad functional group tolerance endowed the reaction with great potential in the field of pharmaceuticals and agrochemicals.

Gold-Catalyzed 1,2-Carboxyarylation of Alkenes

Herein, we disclose an unprecedented gold-catalyzed 1,2-carboxyarylation of alkenes through ligand-enabled Au(I)/Au(III) catalysis. Unlike other approaches for the arylative functionalization of C-C multiple bonds, attempts to utilize weak nucleophiles such as carboxylate anions were unsuccessful. The key to achieving this transformation is the use of a 1,3-diketone-appended alkene, which undergoes gold-catalyzed oxyarylation followed by retro-aldol reaction to afford the product. Detailed mechanistic investigations were conducted to support the proposed mechanism.

Copper-Catalyzed Selective Amino-alkoxycarbonylation of Unactivated Alkenes with CO

1,2-Amino-difunctionalization reactions of alkenes allow the efficient introduction of different functional groups and the rapid construction of valuable functionalized amines. In this respect, we report a copper-catalyzed 1,2-amino-alkoxycarbonylation of unactivated alkenes with CO and alkylamine precursors in the presence of a Lewis acid additive. The novel protocol allows direct access to valuable β-amino acid derivatives from easily available starting materials. The presented methods feature high chemo- and regioselectivities, good functional group tolerance, and substrate scope including diverse bioactive compounds and drug-like molecules. Mechanistic studies indicate that the Lewis acid additive is the key to realizing the efficient umpolung addition of nucleophilic aminyl radicals to electron-rich alkenes, which represents an elegant activation strategy for aminyl radicals.

Enantioselective Photoredox- and Cu-Catalyzed Cyanoalkylation of Styrenes via Deoxygenation of Alkoxyl Radicals with Organophosphorus Compounds(III)

The enantioselective cyanoalkylation of styrenes by a cooperative photoredox and copper catalysis system has been established, providing straightforward access to structurally diverse enantioenriched alkyl nitriles in good yields with excellent enantioselectivities under mild conditions via deoxygenation of alkoxyl radicals with organophosphorus compounds(III). In addition, the reaction features a wide substrate scope and good functional group tolerance, and the resultant alkyl nitriles could be easily converted into a series of chiral carboxylic acids, amides, esters, etc.

Carbon Monoxide and Alkoxycarbonyl Radical Enabled Migration Strategy for the Carbonylative Functionalization of Unactivated Alkenes

Herein we report a "carbonylative migration" strategy for the acylation-esterification type double functionalization of unactivated alkenes using alkyloxalkyl chlorides and CO as the reagents. The transformation is proceeded by the alkoxycarbonyl radical addition to unactivated alkenes, followed by the insertion of carbon monoxide to induce intramolecular migration of heteroaryl groups, which is different from the traditional reaction modes. The reaction conditions were mild and well tolerated with varieties of functional groups. A variety of 1,4-dicarbonyl compounds with different ester groups were produced easily which has high potential applications in biology, medicine, and other fields.

Nickel-Catalyzed Three-Component Carboamination/Cyclization of Alkynes To Access 2,3-Disubstituted Quinolines

Presented herein is a nickel-catalyzed chemo- and regioselective three-component tandem carboamination and cyclization of terminal alkynes with organoboronic acids and anthranils for facile and modular access to 2,3-substituted quinolines. In this process, anthranil has dual roles: serving as an electrophilic aminating reagent and a redox buffer to suppress the generation of an off-cycle Ni(0) complex. Moreover, the anionic acetylacetonate (acac) ligand was found to be vital to ensure a productive Ni(I)-Ni(III)-Ni(I) catalytic cycle.

Ruthenium-Catalyzed Remote Trifunctionalization of Non-Activated Alkenes via Cyano Migration and meta-C(sp2)-H Functionalization

A novel Ru-catalyzed radical-triggered trifunctionalization of hexenenitriles is presented, employing a strategy of remote cyano group migration and meta-C(sp2)-H functionalization. Through remote cyano migration, the alkenyl moiety undergoes difunctionalization to the formation of a benzylic radical intermediate. This intermediate facilitates para-selective C-H bond addition relative to the C-Ru bond within the Ru(III) complex, ultimately enabling trifunctionalization. This methodology provides an efficient route to a diverse array of nitrile-containing compounds with broad functional group compatibility.

Photoredox/Cr-catalyzed enantioselective radical-polar crossover transformation via C-H functionalization

Asymmetric multicomponent reactions that aim to control multiple chiral centers with high selectivity in a single step remain an on-gonging challenge. The realm of enantioselective radical-polar crossover transformation achieved through C-H Functionalization has yet to be fully explored. Herein, we present a successful description of a photoredox/Cr-catalyzed enantioselective three-component (hetero)arylalkylation of 1,3-dienes through C-H functionalization. A diverse array of chiral homoallylic alcohols could be obtained in good to excellent yields, accompanied by outstanding enantioselectivity. The asymmetric radical-polar crossover transformation could build two chiral centers simultaneously and demonstrates broad substrate tolerance, accommodating various drug-derived aldehydes, (hetero)aromatics, and 1,3-diene derivatives. Preliminary mechanistic studies indicate the involvement of a radical intermediate, with the chiral allylic chromium species reacting with various aliphatic and aromatic aldehydes through Zimmerman-Traxler transition states enabled by dual photoredox and chiral chromium catalysis.

Electrochemical Difunctionalization of Alkenes

Owing to their wide utilizations in synthesis and their products prevalence in numerous natural products, pharmaceuticals and functional materials, the alkene difunctionalization methods for the selective transformations of the olefins are important and have attracted much attention form the synthetic chemists. Among them, the electrochemical alkene difunctionalization reaction is particularly promising and has becoming a potent and sustainable tool for the selective transformations of alkenes into vicinal difunctionalized structures in organic synthesis through simultaneous incorporation of two functional groups. Herein, we summarize recent progress in the electrochemical alkene difunctionalization reactions according to the alkene difunctionalization types as well as the category of the radicals over the past five years. By selecting the remarkable synthetic examples, we have elaborately discussed the substrate scope and the mechanisms for the electrochemical olefin difunctionalization reaction.

Metallaphotoredox Enabled Single Carbon Atom Insertion into Alkenes for Allene Synthesis

Efficient methods for synthesizing allenes from readily available starting materials pose a persistent challenge in organic chemistry. In this work, we present a novel two-stage protocol for allene synthesis involving the single-atom insertion into alkenes, facilitated by synergistic photoredox and cobalt catalysis. Diverging from conventional methods such as the Doering-LaFlamme reaction, this photochemical rearrangement approach operates efficiently under mild conditions in a radical-based manner. The protocol exhibits a broad substrate scope and demonstrates applicability in the late-stage diversification of alkene-containing natural products and bioactive molecules. Preliminary mechanistic studies and density functional theory (DFT) calculations offer insights into the reaction pathway, indicating a radical mechanism involving fleeting cyclopropyl carbene intermediates followed by rapid ring opening to form allenes.

Cu-Catalyzed Diastereo- and Enantioselective Synthesis of Borylated Cyclopropanes with Three Contiguous Stereocenters

Direct synthesis of enantioenriched scaffolds with multiple adjacent stereocenters remains an important yet challenging task. Herein, we describe a highly diastereo- and enantioselective Cu-catalyzed alkylboration of cyclopropenes, with less reactive alkyl iodides as electrophiles, for the efficient synthesis of tetra-substituted borylated cyclopropanes bearing three consecutive stereocenters. This protocol features mild conditions, a broad substrate scope, and good functional group tolerance, affording an array of chiral borylated cyclopropanes in good to high yields with excellent diastereo- and enantioselectivities. Detailed mechanistic experiments and kinetic studies were conducted to elucidate the reaction pathway and the rate-determining step of the reaction. DFT calculations revealed that the π···π stacking interaction between the phenyl groups on the substrate and the phosphorus ligand, along with the smaller distortion in the CuL-Bpin part, contributed to the high diastereo- and enantioselectivities. The synthetic utility of the protocol was showcased by the facile synthesis of some valuable chiral cyclopropanes with multiple chiral centers.

Ni-catalyzed regioselective and site-divergent reductive arylalkylations of allylic amines

Catalytic methods by switching the least parameters for regioselective and site-divergent transformations to construct different architectures from identical and readily available starting materials are among the most ideal catalytic protocols. However, the associated challenge to precisely control both regioselectivity and site diversity renders this strategy appealing yet challenging. Herein, Ni-catalyzed cross-electrophile regioselective and site-divergent 1,2- and 1,3-arylalkylations of N-acyl allylic amines have been developed. This Ni-catalyzed reductive three-component protocol enables 1,2-arylalkylation and 1,3-arylalkylation of allylic amines with aryl halides and alkyl halides with excellent chemo-, regio- and site-selectivity, representing the first example of controlled migratory difunctionalization of alkenes under reductive conditions. A wide range of terminal and internal unactivated allylic amines, aryl halides and alkyl precursors were tolerated, providing straightforward and efficient access to diverse C(sp3)-rich branched aliphatic amines from identical starting materials.

Enantioselective construction of silicon-stereogenic vinylsilanes from simple alkenes

The diverse utility of acyclic vinylsilanes has driven the interest in the synthesis of enantioenriched vinylsilanes bearing a Si-stereogenic center. However, the predominant approaches for catalytic asymmetric generation of Si-stereogenic vinylsilanes have mainly relied on transition metal-catalyzed reactions of alkynes with different silicon sources. Here we successfully realize the enantioselective synthesis of linear silicon-stereogenic vinylsilanes with good yields and enantiomeric ratios from simple alkenes under rhodium catalysis. The significance of this transformation lies in its ability to achieve regioconvergent and enantioconvergent conversion, efficiently transforming petroleum-derived isomeric mixtures of olefin feedstocks into a single regio- and stereoisomer product. The practicality of this method is further exemplified by the diverse downstream transformations of these enantioenriched silicon-stereogenic vinylsilanes leveraging the olefin functionality and the leaving group nature of the aryl substituent on silicon as well as the development of chiral π-conjugated double bond systems.

Recent advances in electrochemical copper catalysis for modern organic synthesis

In recent decades, organic electrosynthesis has emerged as a practical, sustainable, and efficient approach that facilitates valuable transformations in synthetic chemistry. Combining electrochemistry with transition-metal catalysis is a promising and rapidly growing methodology for effectively forming challenging C-C and C-heteroatom bonds in complex molecules in a sustainable manner. In this review, we summarize the recent advances in the combination of electrochemistry and copper catalysis for various organic transformations.

Nickel-Catalyzed Three-Component 1,1-Difunctionalization of Unactivated Alkenes with Quinoxaline/Naphthoquinone and Arylboronic Acids via Organometallic-Radical Relay

A nickel-catalyzed intermolecular three-component 1,1-difunctionalization of unactivated alkenes with quinoxaline/naphthoquinone and arylboronic acids via organometallic-radical relay is developed. This efficient protocol provides a new method to access a variety of arylalkanes in moderate to good yields with a broad substrate scope and excellent functional group tolerance. The mechanistic studies provide insights into the mechanism and origin of chemo- and regioselectivity as well as confirm the generation of functionalized benzylic radicals.

Electrochemically Induced Synthesis of N-Allyloxyphthalimides via Cross-Dehydrogenative C-O Coupling of N-Hydroxyphthalimide with Alkenes Bearing the Allylic Hydrogen Atom

The electrochemically induced reaction between alkenes, bearing an allylic hydrogen atom, and N-hydroxyphthalimide was investigated. Cross-dehydrogenative C-O coupling with phthalimide-N-oxyl radical, derived from N-hydroxyphthalimide, occurs instead of oxidation of the allylic site, with the formation of a carbonyl group or functionalization of the double C=C bond. The discovered transformation proceeds in an undivided electrochemical cell equipped with a carbon felt anode and a platinum cathode. Coupling products were obtained with yields up to 79%. The developed process is based on the abstraction of hydrogen atom from the allylic position for functionalization while the C=C bond remains unreacted. The method exploits the ability of the phthalimide-N-oxyl radical to abstract hydrogen atoms with the following interception of the intermediate C-centered radical.

Dual Photoredox/Copper-Catalyzed Three-Component Alkylcyanation of Alkenes and 1,4-Alkylcyanation of 1,3-Enynes Employing Sulfoxonium Ylides as the Carbon Radical Precursors

A novel dual photoredox/copper-catalyzed three-component alkylcyanation of alkenes and 1,4-alkylcyanation of 1,3-enynes have been developed. In this radical cyanoalkylation reaction, the photoredox induced alkyl radical from sulfoxonium ylides adds to the carbon-carbon double bonds of styrenes or 1,3-enynes, and the generated benzylic or allenyl radicals couple with a Cu(II) cyanide complex to achieve selective cyanation. The reaction exhibits high chemo- and regioselectivity and a wide substrate scope, providing an efficient method for the synthesis of alkyl nitriles and allenyl nitriles in a single step.

Photocatalytic EnT-Mediated Aminophosphorylation of Alkenes Using Oxime Esters as Bifunctional Reagents

C-P bond formation has typically been achieved by a single-electron transfer process. Herein, a novel class of oxime ester bifunctionalization reagents were first applied to the photocatalytic β-aminophosphorylation of modular olefins. The bifunctional reagents generate two distinct radical species (imine and phosphoryl radicals) that exhibit excellent regioselectivity. Subsequently, these radicals are attached to the olefins through a single-step EnT catalytic process, establishing a novel synthetic pathway. This protocol is characterized by excellent regioselectivity, broad functional group tolerance, and mild reaction conditions, which would enrich the diversity and versatility to facilitate the diversity-oriented synthesis of β-aminophosphorylated complex molecule scaffolds.

Phosphinothio(seleno)ation of alkynes/olefins and application on the late-stage functionalization of natural products

Non-metallic catalysis has been known as a remarkable development strategy for hydrofunctionalization of unsaturated hydrocarbons. Herein, we report a unique chemically active method of BF3·OEt2 promoted multi-component, highly regioselective, and chemoselective hydrothio(seleo)phosphonylation of unsaturated hydrocarbons, which exhibits high yield and good substrate universality. The reaction mechanism was further elucidated to be Markovnikov addition by controlling experiments, 31P and 19F NMR spectra tracking experiments, X-ray diffraction analysis, and DFT calculations. Furthermore, the gram-scale attempt and the application of the reaction on the derivatization of natural products have been successfully conducted, leading to the discovery of 3as with potential anti-Parkinson's disease (PD) activities at 1 μM. This streamlined and efficient methodology has established a new platform for non-metallic Lewis acids-promoted hydrofunctionalization of unsaturated hydrocarbons and its application on new drug research.

Copper-Catalyzed Asymmetric Radical Oxysulfonylation of 2-Vinylbenzoic Acids to Access Chiral Sulfonyl Phthalides

This study presents the development of a radical enantioselective alkene oxysulfonylation approach for the synthesis of enantioenriched sulfonyl phthalides via a catalyst system consisting of a copper salt and an OPPA ligand. The reaction proceeded under mild conditions with a wide range of substrates, good yields, and excellent enantioselectivities. Mechanistic studies suggested that the reaction proceeded through a radical-mediated process. Scalable synthesis and transformation experiments also demonstrated the applicable potential of this method.

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.

General Alkene 1,2-syn-Cyano-Hydroxylation Procedure Via Electrochemical Activation of Isoxazoline Cycloadducts

Stereoselective alkene 1,2-difunctionalization is a privileged strategy to access three-dimensional C(sp3)-rich chiral molecules from readily available "flat" carbon feedstocks. State-of-the-art approaches exploit chiral transition metal-catalysts to enable high levels of regio- and stereocontrol. However, this is often achieved at the expense of a limited alkene scope and reduced generality. 1,3-Dipolar cycloadditions are routinely used to form heterocycles from alkenes with high levels of regioselectivity and stereospecificity. Nevertheless, methods for the ring-opening of cycloadducts to reveal synthetically useful functionalities require the use of hazardous reagents or forcing reaction conditions; thus limiting their synthetic applications. Herein, we describe the implementation of a practical, general and selective electrosynthetic strategy for olefin 1,2-syn-difunctionalization, which hinges on the design of novel reagents-consisting of a nitrile oxide 1,3-dipole precursor, equipped with a sulfonyl-handle. These can selectively difunctionalize alkenes via "click" 1,3-dipolar cycloadditions, and then facilitate the telescoped electrochemical single electron transfer activation of the ensuing isoxazoline intermediate. Cathodic reduction of the cycloadduct triggers a radical fragmentation pathway delivering sought-after stereodefined 1,2-syn-hydroxy nitrile derivatives. Our telescoped electrochemical procedure tolerates a wide range of functionalities, and─crucially─enables the difunctionalization of both electron-rich, electron-poor and unactivated olefins, with diverse degree of substitution; thus providing a robust, general and selective metal-free alternative to current alkene difunctionalization strategies. Capitalizing on these features, we employed our electrosynthetic method to enable the late-stage syn-hydroxy-cyanation of natural products and bioactive compounds, and streamline the de novo synthesis of pharmaceutical agents.

Direct alkene functionalization via photocatalytic hydrogen atom transfer from C(sp3)-H compounds: a route to pharmaceutically important molecules

Direct functionalization of alkenes with C(sp3)-H substrates offers unique opportunities for the rapid construction of pharmaceuticals and natural products. Although significant progress has been made over the past decades, the development of green, high step-economy methods to achieve these transformations under mild conditions without the need for pre-functionalization of C(sp3)-H bonds remains a substantial challenge. Therefore, the pursuit of such methodologies is highly desirable. Recently, the direct activation of C(sp3)-H bonds via photocatalytic hydrogen atom transfer (HAT), especially from unactivated alkanes, has shown great promise. Given the potential of this approach to generate a wide range of pharmaceutically relevant compounds, this review highlights the recent advancements in the direct functionalization of alkenes through photocatalytic HAT from C(sp3)-H compounds, as well as their applications in the synthesis and diversification of drugs, natural products, and bioactive molecules, aiming to provide medicinal chemists with a practical set of tools.

Photoinduced Asymmetric Alkene Aminohetarylation with Chiral Sulfoximine Reagents

Given the pivotal role of β-(het)arylethylamine moiety in bioactive molecules, the direct amino(het)arylation of alkenes occupies a privileged position in the construction of (het)arylethylamine derivatives. Herein we devise chiral sulfoximines as novel bifunctional reagents which exhibit remarkable efficiency in the challenging asymmetric alkene aminohetarylation reaction, particularly in terms of reactivity and stereo-control. The chiral reagents can be conveniently accessed in gram scale, and efficiently generate N-centered radicals under mild photochemical conditions. The transformation proceeds through enantioselective 1,4-hetaryl migration, ensuring precise chirality transfer from sulfur- to carbon-centers, rendering wide applicability to both aromatic and aliphatic alkenes. Furthermore, the method is straightforward to operate and does not require transition metals or photosensitizers, making it an attractive and practical option.

Light-Induced Difunctionalization of Alkenes with Polyhaloalkanes and Quinoxalin-2(1H)-ones

Herein, we report a metal-free light-induced three-component reaction for the synthesis of polychloroalkyl-substituted quinoxalin-2(1H)-ones using commercially available alkenes, polyhalo alkanes, and quinoxalin-2(1H)-ones. Preliminary mechanistic studies suggested the generation of radical intermediates via an EDA-complex, single electron transfer, or halogen atom transfer pathway. Under mild reaction conditions, various alkenes and quinoxalin-2(1H)-ones containing different functional groups are compatible, providing the corresponding polychloroalkyl-substituted quinoxalin-2(1H)-ones in moderate to good yields.

Photo-/Electrocatalytic Difunctionalization of Alkenes Enabled by C-H Radical Functionalization

The difunctionalization of alkenes represents a powerful tool to incorporate two functional groups into the alkene bones for increasing molecular complexity and has been widely utilizations in chemical synthesis. Upon the catalysis of the green, sustainable, mild photo-/electrochemistry technologies, much attentions have been attracted to the development of new tactics for the transformations of the important alkene and alkane feedstocks driven by C-H radical functionalization. Herein, we summarize recent advances in the photo-/electrocatalytic difunctionalization of alkenes enabled by C-H radical functionalization. We detailedly discuss the substrate scope and the mechanisms of the photo-/electrocatalytic alkene difunctionalization reactions by selecting impressive synthetic examples, which are divided into four sections based on the final terminated step, including oxidative radical-polar crossover coupling, reductive radical-polar crossover coupling, radical-radical coupling, and transition-metal-catalyzed coupling.

Recent advances in photocatalytic and transition metal-catalyzed synthesis of disulfide compounds

Disulfide bonds are essential in protein folding, cellular redox balance, materials science, and drug development. Despite existing synthetic methods, the efficient and selective synthesis of unsymmetrical disulfides remains challenging. This review highlights innovative approaches in visible light photocatalysis, including decarboxylation, deoxydisulfidation of alcohols, and direct C-H disulfidation, showcasing broad substrate applicability and functional group tolerance under mild conditions. Additionally, it explores transition metal-catalyzed systems with copper, nickel, palladium, chromium, Iridium, Rhodium molybdenum, and scandium, offering effective strategies for unsymmetrical disulfide bond formation and late-stage functionalization of complex molecules through reductive coupling, selective oxidation, and novel insertion reactions.

Dicarbofunctionalization of Vinylarenes with Pyridine and Aldehydes via Photocatalytic Hydrogen Atom Transfer

We describe a metal-free and mild three-component reaction utilizing vinylarenes, alkyl aldehydes, and 4-cyanopyridine. In this reaction, the scope of vinylarenes and alkyl aldehydes includes over 40 examples, generating a variety of β-pyridinyl ketones. Moreover, potential applications of this method have been demonstrated by the functionalization of pharmaceutical molecules. An acyl radical is proposed to be produced via a polarity-matched hydrogen atom transfer between alkyl aldehydes and a triplet-state diradical from benzophenone.

Photosensitized Three-Component Carboimination of Alkenes Based on the Relay of Oxy Radicals to Carbon Radicals

Here, we present a metal-free photosensitized three-component reaction for the carboimination of alkenes based on oxime carbonates. Homolysis of oxime carbonates via light-mediated energy transfer enables the simultaneous generation of iminyl radicals and alkoxycarbonyloxyl radicals. The alkoxycarbonyloxyl and alkoxy radicals can act as an effective hydrogen atom transfer reagent, abstracting hydrogen atoms from alkanes and aldehydes, silanes, and phosphine oxide. This strategy exhibits broad functional group tolerance under mild reaction conditions, further broadening the diversity of alkene carboimination.

Shuttle HAT for mild alkene transfer hydrofunctionalization

Hydrogen atom transfer (HAT) from a metal-hydride is a reliable and powerful method for functionalizing unsaturated C-C bonds in organic synthesis. Cobalt hydrides (Co-H) have garnered significant attention in this field, where the weak Co-H bonds are most commonly generated in a catalytic fashion through a mixture of stoichiometric amounts of peroxide oxidant and silane reductant. Here we show that the reverse process of HAT to an alkene, i.e. hydrogen atom abstraction of a C-H adjacent to a radical, can be leveraged to generate catalytically active Co-H species in an application of shuttle catalysis coined shuttle HAT. This method obviates the need for stoichiometric reductant/oxidant mixtures thereby greatly simplifying the generation of Co-H. To demonstrate the generality of this shuttle HAT platform, five different reaction manifolds are shown, and the reaction can easily be scaled up to 100 mmol.

Highly Enantioselective Decarboxylative Difluoromethylation

Organofluorine molecules that contain difluoromethyl groups (CF2H) at stereogenic centers have gained importance in pharmaceuticals due to the unique ability of CF2H groups to act as lipophilic hydrogen bond donors. Despite their potential, the enantioselective installation of CF2H groups into readily available starting materials remains a challenging and underdeveloped area. In this study, we report a nickel-catalyzed decarboxylative difluoromethylation reaction that converts alkyl carboxylic acids into difluoromethylated products with exceptional enantioselectivity. This Ni-catalyzed protocol exhibits broad functional group tolerance and is applicable for synthesizing fluorinated bioisosteres of biologically relevant molecules.

A General Copper-Box System for the Asymmetric Arylative Functionalization of Benzylic, Propargylic or Allenylic Radicals

Radical-involved arylative cross-coupling reactions have recently emerged as an attractive strategy to access valuable aryl-substituted motifs. However, there still exist several challenges such as limited scope of radical precursors/acceptors, and lack of general asymmetric catalytic systems, especially regarding the multicomponent variants. Herein, we reported a general copper-Box system for asymmetric three-component arylative radical cross-coupling of vinylarenes and 1,3-enynes, with oxime carbonates and aryl boronic acids. The reactions proceed under practical conditions in the absence or presence of visible-light irradiation, affording chiral 1,1-diarylalkanes, benzylic alkynes and allenes with good enantioselectivities. Mechanistic studies imply that the copper/Box complexes play a dual role in both radical generation and ensuing asymmetric cross-coupling. In the cases of 1,3-enynes, visible-light irradiation could improve the activity of copper/Box complex toward the initial radical generation, enabling better efficiency match between radical formation and cross-coupling.

Photoinduced copper-catalyzed asymmetric cyanoalkylalkynylation of alkenes, terminal alkynes, and oximes

The asymmetric dicarbofunctionalization of alkenes via a radical relay process can provide routes to diverse hydrocarbon derivatives. Three-component carboalkynylation, limited to particular alkyl halides and using readily available cycloketone oxime esters as redox-active precursors, is restricted by the available pool of suitable chiral ligands for broadening the redox potential window of copper complexes and simultaneously creating the enantiocontrol environment. Herein, we report a new hybrid tridentate ligand bearing a guanidine-amide-pyridine unit for photoinduced copper-catalyzed cyanoalkylalkynylation of alkenes. Leveraging the copper catalyst's redox capability is achieved via merging the electron-rich ligand with a readily organized configuration and enhanced absorption in the visible light range, which also facilitates the enantioselectivity. The generality of the catalyst system is exemplified by the efficacy across a number of alkenes, terminal alkynes and cycloketone oxime esters, working smoothly to give alkyne-bearing nitriles with good yields and excellent enantioselectivity. A mechanistic study reveals that the chiral copper catalyst meets the requirements of possessing sufficient reduction ability, good light absorption properties, and appropriate steric hindrance.

Transition Metal-Free Difunctionalization of Unactivated Alkenes: Arylation/Azidation, Arylation/Chlorination, and Arylation/Cyanation

Arylethylamines represent a privileged scaffold in pharmaceutical compounds and form the backbone of many medical drugs, including those used for treating neurological diseases and pain. Their biomedical significance has inspired new synthetic methods that rely on transition metal-catalyzed aminoarylation reaction to an alkene, often in conjunction with a photoredox catalyst or a photosensitizer, and guided by a directing or stabilizing group. Here, we introduce a simple and effective method for azidoarylation of unactivated alkenes under transition metal-free conditions. Visible or near-UV light irradiation of readily available triarylbismuth dichlorides generates an aryl radical that selectively adds to the alkene, and the resulting homobenzyl radical is intercepted by an amine equivalent. This method offers a broad substrate scope and also enables aryl chlorination and arylcyanation of unactivated alkenes.

Cu0-Promoted Truce-Smiles Rearrangement for Aryl-Difluoromethylenation of C═C Bonds via a Reductive Radical-Polar Crossover Process

An efficient Cu0-promoted Truce-Smiles rearrangement for the aryl-difluoromethylenation of C═C bonds by the reaction of N-alkyl-N-(arylsulfonyl)methacrylamide and 2-bromodifluoromethyl-1,3-benzodiazole via a reductive radical-polar crossover process under mild reaction conditions is presented. The protocol enables practical access to a variety of single regioisomer α-aryl-β-difluoromethylene amides in good to excellent yields through consecutive difluoromethylenation, radical-polar crossover, 1,4-aryl migration, SO2 extrusion, and N-H bond formation cascade reaction.