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The twelve principles of green chemistry illuminate the pathway in the direction of sustainable and eco-friendly synthesis, marking a fundamental shift in synthetic organic chemistry paradigms. In this realm, harnessing the power of visible light for the difunctionalization of various skeletons without employing any external oxidant or reductant, specifically termed as redox-neutral difunctionalization, has attracted tremendous interest from synthetic organic chemists due to its low cost, easy availability and environmentally friendly nature in contrast to traditional metal-catalyzed difunctionalizations. This review presents an overview of recent updates on visible-light-induced redox-neutral difunctionalization reactions with literature coverage up to May 2024. [ABSTRACT FROM AUTHOR]

The visible light-promoted O-alkenylation of phenols and naphthols with terminal alkynes is achieved using 2,4,6-tris(4-fluorophenyl)pyrylium tetrafluoroborate (T(p-F)PPT) as a photocatalyst at room temperature without the need of any external ligand or additive. Apart from its excellent functional group tolerance, the protocol described herein represents an appealing alternative strategy to classical transition-metal catalysed hydroarylation reactions. Mechanistic investigations revealed that the reaction involves a radical pathway. The utility of the hydroarylated products for the synthesis of fused benzofurans via a one-pot annulation was also demonstrated. Herein, we report the first intermolecular radical hydroarylation of alkynes. [ABSTRACT FROM AUTHOR]

Herein, a straightforward method for rapid access to all-carbon tertrasubstituted alkenes bearing alkyl, aryl and alkynyl groups is established via palladium-catalyzed three-component cross-coupling reaction of internal alkynes, haloalkynes and arylboronic acids. This protocol is characterized by a broad substrate scope and excellent chemo- and regioselectivities. The dual beneficial roles of silver salts in activating haloalkynes and inhibiting bromoalkynylation have been demonstrated by serving as both the Lewis acid and halide scavenger. [ABSTRACT FROM AUTHOR]

Comprehensive Summary Herein, an unprecedented nickel‐catalyzed regioselective hydroalkynylation of unsymmetrical internal alkynes was realized with steric hindered resistance selectivity via the cyano‐directing group strategy. Significantly, the resulting 1,3‐enyne products could be effectively employed in the synthesis of novel nitrogen‐containing tricyclics compounds, that provided the potential candidate compound 8a (IC50 = 2.6—6.1 μmol/L) for the anti‐tumor cell proliferation activity. Therefore, this work not only improves the transition‐metal‐ catalyzed hydroalkynylation strategy of internal alkynes, but also exhibits versatility of 1,3‐enynes in the construction of the complex bioactive chemical space. [ABSTRACT FROM AUTHOR]

Diamidopyridine-supported titanium dibenzyl complexes undergo coordination-induced C–C reductive elimination upon addition of alkynes and quantitative formation of titanacyclopentadienes. The distinct radical mechanism of this reductive mechanism gives new insights into C–C bond formation with titanium. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: The rhodium‐catalyzed C—H bond activation and cyclization of 3‐oxopent‐4‐enenitriles with alkynes proceed efficiently. Various 2H‐pyrans with multiple substituents are achieved in good yields through regioselective formation of C—O and C—C bonds. Transformations involving hydroxy‐alkynoates resulted in products with a furo[3,4‐b]pyran skeleton via further intramolecular ester exchange processes. Different from the traditional "1‐oxatrienes pathway", this method for the synthesis of useful 2H‐pyrans possesses certain highlights in terms of readily available substrates, stable and easily derivatized products, gentle and convenient operation process, and step and atom economy. [ABSTRACT FROM AUTHOR]

α-Imino metal carbenes are versatile intermediates in organic synthesis, and have broad applications in the assembly of divergent N-heterocycles. However, the catalytic enantioselective desymmetrization based on α-imino metal carbenes has not been developed to date. Herein, we disclose an enantioselective desymmetrizing C(sp2)–H functionalization of azide-ynamides via α-imino copper carbenes, leading to the efficient assembly of divergent chiral indoloazepines in generally moderate to excellent yields with high enantioselectivities. Notably, this reaction represents the first enantioselective desymmetrization based on α-imino metal carbenes. Further synthetic transformations and biological tests show the potential utility of this method. Moreover, computational studies are employed to elucidate the reaction mechanism and the origin of enantioselectivity. [ABSTRACT FROM AUTHOR]

ABSTRACT Synthesis of 5‐alkynyl furopyrimidine nucleoside analogs, with free‐ribose groups, was carried out, and their biological activity was evaluated. The substituents introduced at the C‐5 included propargyl and homopropargyl alcohols, 4‐methylphenyl (p‐tolyl), and 4‐pentylphenyl substituted alkynyl groups (56%–88%). Subsequently, alkyne function was coordinated to dicobalt hexacarbonyl unit, yielding the corresponding dicobalt hexacarbonyl 5‐alkynyl furopyrimidine nucleosides (51%–75%). All compounds contained 4‐pentylphenyl group attached at the C‐6 position of the bicyclic base, in line with most active antiviral structures. The antiproliferative effect of these modified nucleosides on cancer cells of different phenotypes was determined using in vitro studies. The tested compounds show antiproliferative effects with median inhibitory concentration (IC50) values of 16–23 and 9–15 μM for HeLa and K562 cells. The determination of reactive oxygen species (ROS) formation in K562 cells in the presence of modified nucleosides may suggest that the mode of action of the examined compounds may be attributed to the induction of oxidative stress. [ABSTRACT FROM AUTHOR]

Ylide‐functionalized phosphines (YPhos) have been shown to yield highly active gold catalysts owing to their high donor capacity. To examine the impact of ylide functionalization on a given ligand structure, a series of ferrocenyl diphosphines functionalized with no, one or two ylide moieties and their corresponding bimetallic gold complexes were prepared. The complexes feature an anti‐conformation of the two phosphine moieties, guaranteeing the presence of two independent metal centers. Comparative studies of the complexes in the hydroamination and hydrohydrazination of alkynes revealed a significant increase in catalytic activity for each newly introduced ylide group. The di‐YPhos ligands were revealed to be the most active precatalysts, functioning effectively even at 0.1 or 0.2 mol % catalyst loading. This catalytic efficiency was demonstrated for a series of alkynes, amines and hydrazines. [ABSTRACT FROM AUTHOR]

Comprehensive Summary Catalytic methylative coupling of internal alkynes and aldehydes/aldimines through regioselective oxidative cyclization promoted by a phosphine–Co complex is presented. Such process constitutes an unprecedented and unique approach for Co‐catalyzed generation of metallacycles that reversed inherent regiochemical biases to furnish a wide range of allylic alcohols and allylic amides bearing a tetrasubstituted alkene in up to 98% yield with high regioselectivity, representing a novel and general strategy for reversal of substrate‐controlled regioselectivity in metal‐catalyzed oxidative cyclization. [ABSTRACT FROM AUTHOR]

This review article describes the development of the use of aluminum compounds in the chemistry of frustrated Lewis pairs (FLPs) over the last 14 years. It also discusses the synthesis, reactivity and catalytic applications of intermolecular, intramolecular and so‐called hidden FLPs with phosphorus, nitrogen and carbon Lewis bases. The intrinsically higher acidity of aluminum compounds compared to their boron analogs opens up different reaction pathways. The results are presented in a more or less chronological order. It is shown that Al FLPs react with a variety of polar and non‐polar substrates and form both stable adducts and reversibly activate bonds. Consequently, some catalytic applications of the title compounds were presented such as dimerization of alkynes, hydrogenation of tert‐butyl ethylene and imines, C−F bond activation, reduction of CO2, dehydrogenation of amine borane and transfer of ammonia. In addition, various Al FLPs were used as initiators in polymerization reactions. [ABSTRACT FROM AUTHOR]

We report the development of a four‐component electrochemical method for the synthesis of CF3‐oxazoles, utilizing alkynes and NaSO2CF3 in MeCN. The method leverages the simplicity and mildness of the reaction conditions, despite the inherent complexity of utilizing four distinct components through aminotrifluoromethylation of alkyne followed by in‐situ cyclization. Notably, in addition to MeCN solvent, the presence of residual water in the reaction mixture also contributed as a coupling partner. The synthesis involves a sequence of four controlled oxidation steps under constant potential with graphite electrodes, facilitated by the mediator TMEDA, highlighting the precision achievable in electrochemistry. [ABSTRACT FROM AUTHOR]

A novel deoxygenative alkynylation of amides promoted by a synergistic action of a divalent rare-earth element and a transition metal has been developed. In this method, α-alkynyl substituted amines are synthesized from unactivated amides and alkynes in a single transformation. Broad substrate scope and excellent selectivity for C＝O cleavage has been demonstrated. This approach represents a general method for the construction of versatile α-alkynyl substituted amines from unactivated amide bonds. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: By rational modification of electronic and steric properties of pincer ligands, a Co/Fe dual catalyst system is developed for one‐pot sequential Markovnikov alkyne hydrosilylation and stereoselective alkene isomerization. The protocol provides an atom‐economical and efficient approach to trisubstituted (E)‐alkenyl silanes from widely accessible terminal alkynes with high regio‐ and stereoselectivities under mild conditions. The utility of this reaction was demonstrated by gram‐scale synthesis and derivatization of bioactive molecules. The radical clock and trapping experiments indicated that radical pathway might be operative in the alkene isomerization step. [ABSTRACT FROM AUTHOR]

Chemical reactivity and applications of 4-alkynylated pyrazol-3-ones are described. A facile access to the synthesis of novel pyrazol-4-yl furan- and/or thiophene-2-carboxylates through the ring transformation and subsequent acylation of 4-alkynylated pyrazol-3-ones as the key intermediates, which were prepared from pyrazole-4,5-dione and terminal alkynes, in moderate to good yields is achieved. All the synthesized compounds were characterized by spectroscopic analysis. [ABSTRACT FROM AUTHOR]

Unstable tetra(methoxycarbonyl)cyclopentadienone was investigated in the synthesis of electron-deficient cycloheptatrienes via [4+2]-cycloaddition/cycloelimination reaction with cyclopropenes. The use of its stable dimer did not afford the product although similar reactions with alkynes have been reported. Quantum chemical calculation revealed that cyclopentadienone is not generated from the dimer and the reaction with alkynes proceeds via a more complicated cycloelimination/cycloaddition/cycloelimination cascade. However, the formation of cycloheptatrienes was found favorable over the formation of the dimer. Therefore, the trapping of tetra(methoxycarbonyl)cyclopentadienone upon formation was successful to give cycloheptatrienes with five ester groups. The use of methyl coumalate as a four-electron component was successful with cyclopropenes containing only one ester group to afford only two ester groups in the product. [ABSTRACT FROM AUTHOR]

A mild Pd-catalyzed three-component cascade cyclization functionalization of o-iodostyrenes, internal alkynes and boron reagents is presented. The transformation is driven by a controlled reaction sequence of intermolecular carbopalladation, intramolecular Heck-type cyclization, and a borylation process to give versatile boryl-functionalized indene skeletons in a selective fashion. Significantly, (Bpin)2, (Bneop)2 and CH2(Bpin)2 as boron sources are all tolerated. Additionally, the synthetic utility of this approach is demonstrated by gram-scale synthesis and synthetic transformations. [ABSTRACT FROM AUTHOR]

This report describes a copper-catalyzed, photoinduced N-to-alkyl radical relay Sonogashira-type reactions at benzylic sites in o-alkylbenzamides with alkynes. The process employs an N-to-alkyl radical mechanism, initiated through the copper-catalyzed reductive generation of nitrogen radicals. Radical translocation is facilitated by a 1,5-hydrogen atom transfer (1,5-HAT), leading to the formation of translocated carbon radicals. These radicals are then subjected to copper-catalyzed alkynylation. The methodology exhibits broad sub-strate scope and applicability to the synthesis of complex natural products. [ABSTRACT FROM AUTHOR]

The development of new catalytic methods based on lower-cost metals under environmentally friendly conditions is still a challenge. Herein, we report an efficient strategy for the synthesis of vinyl sulfones from O -propargyl alkynes and sodium salts of sulfinic acids using silver nitrate, an inexpensive and readily available catalyst, under air atmosphere using aqueous conditions. The products were obtained in good to moderate yields, and the mechanism of the reaction was also investigated. [ABSTRACT FROM AUTHOR]

A new method for the intramolecular electrophilic ipso -cyclization of alkynes with triflic anhydride-activated sulfoxides, followed by demethylation with triethylamine in one pot, is described for the synthesis of 3-thiospiro[4.5]-decatrienones in moderate to good yields. This method provides a facile strategy for assembling the sulfur-substituted spirocyclic compounds. [ABSTRACT FROM AUTHOR]

Visible‐light‐mediated [2+2] photocycloaddition reaction can be considered an ideal solution due to its green and sustainable properties, and is one of the most efficient methods to synthesize four‐membered ring motifs. Although research on the [2+2] photocycloaddition of alkynes is challenging because of the diminished reactivity of alkynes, and the more significant ring strain of the products, remarkable achievements have been made in this field. In this article, we highlight the recent advances in visible‐light‐mediated [2+2] photocycloaddition reactions of alkynes, with focus on the reaction mechanism and the late‐stage synthetic applications. Advances in obtaining cyclobutenes, azetines, and oxetene active intermediates continue to be breakthroughs in this fascinating field of research. [ABSTRACT FROM AUTHOR]

Vinyl sulfones are crucial building blocks in synthetic chemistry and core structural units of pharmaceutically active molecules, thus extensive investigations have been conducted on the construction of these skeletons. In contrast to the classical synthetic approaches, the radical sulfonylation of alkynes for producing vinyl sulfones has garnered considerable interest because of its mild conditions and high efficiency. Radical sulfonation of alkynes typically begins with the sulfonyl radical attacking the alkynes, followed by further functionalization. Moreover, the association of metal‐catalyst‐free systems with multicomponent reactions (MCRs) offers an environmentally friendly pathway for efficiently constructing complex scaffolds from readily available partners. However, there is no comprehensive review summarizing the advancements in metal‐catalyst‐free multicomponent radical sulfonylation of alkynes. Hence, we provide a categorical overview based on the objects of sulfonylation of alkynes (hydrosulfonylation, carbosulfonylation, aminosulfonylation, oxysulfonylation, sulfosulfonylation, selenosulfonylation, and iodosulfonylation), along with interpretations of the reaction mechanisms. [ABSTRACT FROM AUTHOR]

Ni‐catalyzed activation of C(sp2)−H bond remains an elusive challenge. Herein, we realized a Ni‐catalyzed selective activation of C(sp2)−H bond of formamides, which underwent addition reaction with internal alkynes to provide α,β‐unsaturated amide compounds in high yields. The protocol was featured by the cheap and nontoxic catalyst system. Preliminary mechanistic studies shed light on the reaction pathways. [ABSTRACT FROM AUTHOR]

Synthetic radicals have intrinsic power for cascading and multifunctional reactions to construct diverse molecular scaffolds. In the previous review series, we covered 1,2-difunctionalizations, remote 1,3-, 1,4-, 1,5-, 1,6-, and 1,7-difunctionalizations, addition followed by cyclization reactions, and cycloaddition-initiated difunctionalizations. Presented in this paper are radical addition-initiated trifunctionalization reactions of alkenes, alkynes, and their derivatives. After the initial radical addition, there are different pathways, such as group or hydrogen atom transfer, cyclization, and radical coupling, to complete the second and third functionalizations. [ABSTRACT FROM AUTHOR]

An efficient and operationally simple method for the synthesis of β-keto sulfones through the BF3·OEt2-promoted reaction of alkynes and sodium sulfinates is developed. With its facile and selective access to the targets, it features good functional group compatibility, mild conditions, easily available starting materials, and good yields. Notably, the reaction does not require metal catalysts or chemical reagents with pungent odors. [ABSTRACT FROM AUTHOR]

In this study, novel Cu@CuFe2O4 nanoparticles were prepared by virtue of a simple method. By utilizing a compatible system involving N‐chlorosuccinimide (NCS) as the chlorine source and Cu@CuFe2O4 magnetic nanoparticles (NPs) as recyclable catalyst, we present a novel and practical method for directly obtaining aryl α,α‐dichloroketones in aqueous trifluoroethanol (TFE). The catalyst was recovered and reused up to five times with no significant decrease in activity. The current study provides a foundational raw material for the subsequent synthesis of chlorinated functional molecules, which is achieved through a mild transformation of arylalkynes using readily available commercial feedstocks and exhibiting good tolerance with various substituents on the aromatic ring, including the aliphatic alkyne. This novel heterogeneous catalyst may be used in numerous industrial applications because of its merits, such as considerable recyclability, low requirement for catalyst loading, cost‐effectiveness, and ease of handling. [ABSTRACT FROM AUTHOR]

Organophosphorus heterocycles have long been acknowledged for their significant potential across diverse fields, including catalysis, material science, and drug development. Incorporating phosphorus functionalities into organic compounds offers a means to effectively tailor their medicinal properties, augment biological responses, and enhance selectivity and bioavailability. The distinctive physical and photoelectric characteristics of phosphorus‐containing conjugated compounds have garnered considerable interest as promising materials for organic optoelectronics. These compounds find extensive utility in various applications such as light‐emitting diodes, photovoltaic cells, phosphole‐based fluorophores, and semiconductors. [ABSTRACT FROM AUTHOR]

The atroposelective transformation of alkynes is an efficient protocol for the assembly of axially chiral compounds. Benefitting from the rapid development of chiral organocatalysts, the organocatalytic atroposelective reactions of alkynes have been extensively studied over the past decades. An array of chiral catalysts, including chiral Brønsted acid catalysts, secondary amine catalysts, N -heterocyclic carbene (NHC) catalysts, thiourea catalysts and N -squaramide catalysts, are employed in enantioselective reactions of different alkynes. This short review summarizes the recent advances on organocatalytic atroposelective reactions of alkynes according to the type of alkyne substrate. The reaction mechanisms, modes of enantiocontrol, product diversity and applications are highlighted. 1 Introduction 2 Electron-Rich Aryl Alkynes 3 Electron-Deficient Aryl Alkynes 4 Other Types of Alkynes 5 Conclusion and Outlook [ABSTRACT FROM AUTHOR]

The migratory insertion of metal-hydride into alkene has allowed regioselective access to organometallics, readily participating in subsequent functionalization as one conventional pathway of hydroalkylation, whereas analogous process with feedstock alkyne is drastically less explored. Among few examples, the regioselectivity of metal-hydride insertion is mostly governed by electronic bias of alkynes. To alter the regioselectivity and drastically expand the intermediate pools that we can access, one aspirational design is through alternative nickel-alkyl insertion, providing opposite regioselectivity induced by steric demand. Leveraging in situ formed nickel-alkyl species, we herein report the regio- and enantioselective hydroalkylation of alkynes with broad functional group tolerance, excellent regio- and enantioselectivity, enabling efficient route to diverse valuable chiral allylic amines motifs. Preliminary mechanistic studies indicate the aminoalkyl radical species can participate in metal-capture and lead to formation of nickel-alkyl, of which the migratory insertion is key to reverse regioselectivity observed in metal-hydride insertion. Although the stereochemistry of nickel hydride addition to alkenes is well-explored, the analogous addition to another feedstock, alkynes, is less studied. Here the authors develop a regio- and enantioselective hydroalkylation of alkynes to produce chiral allylic amines, proceeding via migratory insertion of a nickel–alkyl species into an alkyne pi bond. [ABSTRACT FROM AUTHOR]

The σ-arsolido complex [Mo(AsC4Me4)(CO)3(η5-C5H5)] is alkylated at arsenic by MeOTf to afford the pentamethylarsole complex [Mo(MeAsC4Me4)(CO)3(η5-C5H5)](OTf) while iodomethane affords a mixture of [Me2AsC4Me4]I, [MoMe(CO)3(η5-C5H5)], [MoI(CO)3(η5-C5H5)] and the arsole complexes cisoid- and transoid-[MoI(MeAsC4Me4)(CO)2(η5-C5H5)] and transoid-[Mo{C(＝O)Me}(MeAsC4Me4)(CO)2(η5-C5H5)], The arsole ligand in [Mo(MeAsC4Me4)(CO)3(η5-C5H5)](OTf) is readily liberated by NaI in acetone to afford free MeAsC4Me4 and [MoI(CO)3(η5-C5H5)]. In a similar manner, the reaction of [Mo(AsC4Ph4)(CO)3(η5-C5H5)] with MeI affords MeAsC4Ph4 and [MoI(CO)3(η5-C5H5)], while [Mo{AsC4(SiMe3)-2-Me2-3,4}(CO)3(η5-C5H5)] with MeOTf affords [Mo{MeAsC4(SiMe3)-2-Me2-3,4}(CO)3(η5-C5H5)](OTf). The reaction of [Mo(AsC4Me4)(CO)3(η5-C5H5)] with activated alkynes (RC≡CR: R = CF3, CO2Me) does not proceed via [4 + 2] cyclo-addition but rather electrophilic attack at arsenic followed by metallacyclisation with incorporation of a carbonyl ligand in the spirocyclic complexes [Mo{As(C4Me4)CR＝CRCO}(CO)2(η5-C5H5)]. [ABSTRACT FROM AUTHOR]

An iridium-catalyzed ligand-controlled semi-reduction of alkynes employing H2 O as the hydrogen donor, together with its application, is reported. The use of di- tert -butylphosphinous chloride is crucial for stereoselectivity toward Z -olefins, whereas the use of 2-(diphenylphosphino)benzaldehyde is crucial for stereoselectivity toward E -olefins. More than 35 alkenes were obtained in good yields and high stereoselectivities. The utility of the current method in practical applications was investigated by studying the drug effects of (E)-1,3-dimethoxy-5-styrylbenzene on nerve growth in a zebrafish model. [ABSTRACT FROM AUTHOR]

Diarylacetylenes ArC≡CAr featuring condensed aromatic hydrocarbon fragments (Ar) such as naphthalene, anthracene, phenanthrene and pyrene were converted into vinylidene ligands by 1,2‐migration reactions within the coordination sphere of half‐sandwich complexes [MII(dppe)Cp]+ (MII = RuII, FeII). Comparison of the extent of conversion of the alkyne substrates to the vinylidene complexes [Ru{=C=CAr2}(dppe)Cp]+ with those obtained from acetylenes functionalized by smaller groups (H, CH3, Ph) show that the molecular volume (VM) of the migrating group and relief of steric congestion plays a role during the rearrangement process. Conversely, the H‐atoms from the larger condensed ring aryl groups that are in close proximity to the migrating sites also have a significant influence on the efficacy and extent of the reaction by restricting access of the alkyne to the metal center, resulting in a less effective migration reaction. This combination of competing steric factors (acceleration due to relief of steric congestion and restricted access of the alkyne moiety to the reaction site) is exemplified by the facile migration of 1‐pyryl entities and the low yields of vinylidene products formed from 1,2‐bis(9‐anthryl)acetylene. [ABSTRACT FROM AUTHOR]

Metal-catalyzed highly Markovnikov-type selective hydrofunctionalization of terminal alkynes provides a straightforward and atom-economical route to access 1,1-disubstituted alkenes, which have a wide range of applications in organic synthesis. However, the highly Markovnikov-type selective transformations are challenging due to the electronic and steric effects during the addition process. With the development of metal-catalyzed organic synthesis, different metal catalysts have been developed to solve this challenge, especially for platinum group metal catalysts. In this perspective, we review homogeneous metal-catalyzed Markovnikov-type selective hydrofunctionalization of terminal alkynes according to the classified element types as well as reaction mechanisms. Future avenues for investigation are also presented to help expand this exciting field. [ABSTRACT FROM AUTHOR]

A polycyclic aromatic hydrocarbon displaying twelve edge nitrogen centers for a 42 π-electron system is reported. This compound was synthesized via Sonogashira coupling of pyrimidine precursors, [2+2+2] cycloaddition of bis(aryl) alkynes, and anionic cyclodehydrogenation. Spectroscopy, electrochemistry, and computational results suggest a narrowing of the HOMO–LUMO gap compared to the N-free analogue. Metal coordination affects the optical properties of the extended π system. [ABSTRACT FROM AUTHOR]

In 1,1,1,3,3,3‐hexafluoroisopropyl alcohol (HFIP), gem‐bis(triflyl)cyclobutenes, which can be prepared by the (2+2) cycloaddition reaction of Tf2C=CH2 with alkynes, underwent desulfination to generate the corresponding cyclobutenyl cation. This unique reactivity was successfully applied to the Friedel–Crafts type cyclobutenylation reaction of several (hetero)aromatic compounds. [ABSTRACT FROM AUTHOR]

Electrocatalytic alkynes semi-hydrogenation to produce alkenes with high yield and Faradaic efficiency remains technically challenging because of kinetically favorable hydrogen evolution reaction and over-hydrogenation. Here, we propose a hierarchically nanoporous Cu50Au50 alloy to improve electrocatalytic performance toward semi-hydrogenation of alkynes. Using Operando X-ray absorption spectroscopy and density functional theory calculations, we find that Au modulate the electronic structure of Cu, which could intrinsically inhibit the combination of H* to form H2 and weaken alkene adsorption, thus promoting alkyne semi-hydrogenation and hampering alkene over-hydrogenation. Finite element method simulations and experimental results unveil that hierarchically nanoporous catalysts induce a local microenvironment with abundant K+ cations by enhancing the electric field within the nanopore, accelerating water electrolysis to form more H*, thereby promoting the conversion of alkynes. As a result, the nanoporous Cu50Au50 electrocatalyst achieves highly efficient electrocatalytic semi-hydrogenation of alkynes with 94% conversion, 100% selectivity, and a 92% Faradaic efficiency over wide potential window. This work provides a general guidance of the rational design for high-performance electrocatalytic transfer semi-hydrogenation catalysts. Electrocatalytic alkyne semi-hydrogenation to alkenes is challenging due to the hydrogen evolution competing reaction and over-hydrogenation. Here, the authors report Cu50Au50 alloy for high selectivity towards styrene production. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Lewis base catalyzed and Brønsted acid controlled chemodivergent electrophilic selenofunctionalizations of alkynes were developed for the first time. Various selenium‐containing tetrasubstituted alkenes were readily obtained in moderate to excellent yields with complete E/Z selectivities. As the substrates were 1‐ethynyl naphthol derivatives, linear selenium‐containing tetrasubstituted alkenes were produced via intermolecular oxygen nucleophilic attack in the absence of acid additive; in contrast, cyclic selenium‐containing tetrasubstituted alkenes were generated through intramolecular carbon nucleophilic capture with the addition of Brønsted acid. [ABSTRACT FROM AUTHOR]

Polymeric materials with antibacterial properties hold great promise for combating multidrug‐resistant bacteria, which pose a significant threat to public health. However, the synthesis of most antibacterial polymers typically involves complicated and time‐consuming procedures. In this study, we demonstrate a simple and efficient strategy for synthesizing functional poly(vinylpyridinium salt)s via pyridinium‐yne click polymerization. This click polymerization could proceed with high atom economy under mild conditions without any external catalyst, yielding soluble and thermally stable poly(vinylpyridinium salt)s with satisfactory molecular weights and well‐defined structures in excellent yields. Additionally, the incorporation of luminescent units such as fluorene, tetraphenylethylene, and triphenylamine into the polymer backbone confers excellent aggregation‐enhanced emission properties upon the resulting polymers, rendering them suitable for bacterial staining. Moreover, the existence of pyridinium salt imparts intrinsic antibacterial activity against multidrug‐resistant bacteria to the polymers, enabling them to effectively inhibit wound bacterial infection and significantly expedite the healing process. This work not only provides an efficient method to prepare antibacterial polymers, but also opens up the possibility of various applications of polymers in healthcare and other antibacterial fields. [ABSTRACT FROM AUTHOR]

In this paper, an alternative and efficient copper(I)-catalyzed synthesis of 2-sulfonyliminocoumarins is developed through a three-component reaction of ortho-hydroxybenzyl alcohol, alkynes, and p-toluenesulfonyl azide. The proposed route for access to the 2-iminocoumarin ring involves a [4 + 2] hetero-Diels-Alder reaction between ortho-quinone methide and ketenimine intermediates generated in situ. [ABSTRACT FROM AUTHOR]

The copper catalyzed hydroboration of alkynes with B2pin2 was studied by in detail studies of individual relevant steps along the catalytic pathway. A number of reaction steps were retraced by in situ NMR spectroscopy as well as central intermediates and side‐products were isolated and comprehensively characterized. A copper boryl complex is central to the catalytic process by inserting the terminal alkyne substrate into the B−Cu bond. The selectivity of this step – depending on the NHC auxiliary ligand – determines the α/β selectivity observed in the product. The latter complex is protonated by the auxiliary alcohol reagent resulting in hydroboration product formation and formation of a Cu alkoxido complex. Reaction of the latter with B2pin2 results in the regeneration of the central copper boryl complex. This alcoholysis step depends on the acidity of the alcohol, in particular on the relative acidity of the alcohol vs. the alkyne substrate. A number of side reactions leading to the hydrogenation product of the alkyne substrate and a bis hydroborated product were identified and studied in some detail. It is concluded that the performance of a particular catalytic system depends crucially on the relative acidities of the reagents and generalizations may be difficult. [ABSTRACT FROM AUTHOR]

Sulfo(xo)nium diacylmethylides (sulfur ylides) are simple, stable, readily prepared, and versatile synthons. Compared with the sulfo(xo)nium monoacylmethylides, they can be compatible with more rigorous reaction conditions and showcase unique characteristics due to their excellent stability. This concept article provides an account for the syntheses of sulfo(xo)nium diacylmethylides, including the utilization of active methylene compounds, carbene precursors, sulfo(xo)nium monoacylmethylides, and electron‐deficient alkynes as substrates, with discussions on substrate scopes, proposed mechanisms, selected product examples, and applications. Challenges for further exploration and prospect on sulfo(xo)nium diacylmethylides in the future are also suggested. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Lewis base catalyzed and Brønsted acid controlled chemodivergent electrophilic selenofunctionalizations of alkynes were developed for the first time. Various selenium‐containing tetrasubstituted alkenes were readily obtained in moderate to excellent yields with complete E/Z selectivities. As the substrates were 1‐ethynyl naphthol derivatives, linear selenium‐containing tetrasubstituted alkenes were produced via intermolecular oxygen nucleophilic attack in the absence of acid additive; in contrast, cyclic selenium‐containing tetrasubstituted alkenes were generated through intramolecular carbon nucleophilic capture with the addition of Brønsted acid. [ABSTRACT FROM AUTHOR]

With halogen‐atom transfer as an effective tool, a novel catalytic enantioselective protocol to generate chiral trifluoromethylated alkynes has been established by a cooperative photoredox and nickel catalysis system, providing a straightforward and modular route to access this type of product in good yields and enantioselectivities. The halogen‐atom transfer process is essential for the reaction and this novel strategy offers another promising way to utilize alkyl halides with highly negative reduction potentials. It firstly expands nickel‐catalyzed asymmetric reductive cross‐couplings of organohalides from the traditional single‐electron transfer to halogen‐atom transfer. [ABSTRACT FROM AUTHOR]

The semi‐hydrogenation of terminal alkynes is achieved with sodium borohydride (NaBH4) as the reductant and palladium nanowires (PdNWs) as the catalysts under ambient conditions. The reaction proceeds smoothly in the presence of only 0.32 mol % of PdNWs, giving the hydrogenated products with up to 98 % overall yields, in which 97 % are semi‐hydrogenated products. Under the optimal reaction conditions, both aromatic and aliphatic terminal alkynes have been successfully converted to the corresponding olefins with high efficiency and good selectivity. This method promotes the hydrogenation of terminal alkynes under mild conditions and opens up a window for the application of metal nanowires in organic syntheses. [ABSTRACT FROM AUTHOR]

An efficient heterogeneous catalytic system for the oxidative aminocarbonylation of alkynes and amines in the presence of CO/O2 to afford substituted propiolamides has been developed. The active nanocatalyst, [Pd/Mg3Al‐LDH]‐300(D), is composed by Pd nanoaggregates (2–3 nm average particle size) stabilized over a partially dehydrated [Mg3Al‐LDH] matrix. The methodology has resulted widely applicable, being the first catalytic system, either homogeneous or heterogeneous, able to activate not only aliphatic amines but also poorly‐nucleophilic aromatic amines. In fact, >60 substituted propiolamides have been synthesized in good to excellent isolated yields through this methodology, being 27 novel compounds. An important characterization effort (XRD, 27Al MAS NMR, TGA, TPD‐CO2, BET area, XPS, HAADF‐HRSTEM and HRTEM) and optimization of the synthesis conditions of the optimal catalyst has been performed. This study, together with a series of kinetic and mechanistic essays, indicates that the optimal catalyst is composed by Pd(0) species stabilized in a partially dehydrated/dehydroxylated LDH material with a Mg/Al molar ratio of 3 and a small crystallite size. All the experimental data indicates that the in situ formation of [PdI2] active species in the material surface together with the presence of a matrix with the optimal acid/base properties are key aspects of this process. [ABSTRACT FROM AUTHOR]

The building of N-heterocyclic cores endures an influential area of research due to their ubiquitous presence in natural products, agrochemicals, and small bioactive molecules. Over the past two decades, the synthesis of N-heterocycles via C-H activation comes out as a dominating synthetic protocol in atom-economic manner. The creation of C-C/C-N bonds acts as a key determining step for the building of nitrogen-based heterocycles via direct C-H activation protocol, which could serve as a fascinating concept. In recent years, Group 9 (Co, Rh & Ir) transition metal emerged as a robust catalytic system for the development of valuable N-heterocyclic scaffolds among other transition metals due to their mild reaction conditions, high reactivity, and functional group tolerance. A diverse type of arenes such as anilines/anilides, benzamides, hydrazones, ketoximes, benzylamine, and N-aryl nitrones were subjected to the C-H bond activation for the annulation reaction. Moreover, unsaturated compounds such as alkyne and olefin as coupling partners are again the most used companions for the same purpose, i.e., formation of N-heterocycles. Therefore, this review centers on the up-to-date reports on N-heterocycles synthesis by implementing alkynes and olefins as coupling partners through Group 9 transition metals' catalysis. The methodologies will be based on the coupling of alkynes and olefin, which preferably react in an intermolecular fashion. The scope, limitation, and mechanistic investigation of the Group 9 metal-activated C-H functionalization for the access of N-containing heterocycles with unsaturated reacting partners are the primary focus of the current review. [ABSTRACT FROM AUTHOR]

This article discusses the development of a heterogeneous copper-based catalyst, Cu3N NC, for the protosilylation of unsaturated compounds. The catalyst was found to be effective in the synthesis of various silanes from alkynes, alkenes, and imines under base- and ligand-free conditions. The Cu3N NC catalyst demonstrated high activity and durability, and it could be reused multiple times without significant loss of activity. The article also presents the protosilylation of alkynes with electron-withdrawing groups, the protosilylation of alkenes, and the protosilylation of imines using the Cu3N NC catalyst. The findings contribute to the development of sustainable technologies for the production of valuable silanes. [Extracted from the article]

Green chemistry strives for sustainability at the molecular level and is gaining increasing relevance in the development of chemical reactions. The haloalkynylation reaction is a highly atom–economical C−C coupling reaction that was previously only achieved using transition metal catalysts. It enables the introduction of an alkyne unit and a halogen atom into the target molecule. Herein, we present a haloalkynylation reaction catalyzed by indium(III) halides. The use of indium(III) bromide as a catalyst leads exclusively to the cis addition products with yields up to 86 %. In addition, iodoacetylenes can be applied for the first time for the haloalkynylation reaction of internal alkynes which is an important step forward in the development of industrially relevant and sustainable catalysts. In contrast to gold catalysis, which proceeds via a similar mechanism, the use of alkyl‐substituted haloacetylenes as reagents is also possible. Based on 13C labeling experiments and quantum chemical calculations, we postulate two possible mechanisms for the indium(III)‐catalyzed haloalkynylation reactions. [ABSTRACT FROM AUTHOR]

An intermolecular annulation reaction of 2‐aryl‐1,3‐indandions with alkynes was reported using Pd(OAc)2 to access spirobi[indene]‐1,3‐diones. Under palladium catalysis, the substrates form a homocoupling dimer intermediate through a catalytic dehydrogenative cross‐coupling process. The palladium(II) species could come from dimer or 2‐aryl‐1,3‐indandion. Notably, this pathway is not typically observed in enol‐directed formal sp3 C−H functionalization/oxidative annulation palladium chemistry. This transformation provides a route to access a class of functionalized spiro carbocyclic indenes. [ABSTRACT FROM AUTHOR]

Recently, transition metal‐catalyzed ortho‐C−H bond activation/annulations involving two internal alkyne molecules have been extensively used to synthesize highly substituted polycyclic aromatic scaffolds. Such reactions have emerged as a powerful atom and step‐economical strategy for the assembly of multifunctional bioactive molecules. In this context, we focused on the recent achievements of dual C−H bond activation/annulations, as well as functionalization reactions involving diaryl/alkyl alkynes. [ABSTRACT FROM AUTHOR]