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A visible-light-initiated electron-donor–acceptor (EDA) complex-driven regioselective vicinal and oxidative geminal thiosulfonylation of alkynes is presented. Organic thiosulfonates act as an acceptor, producing either sulfonyl (RSO2˙) or thiyl (RS˙) radicals under base and solvent switchable conditions. Simultaneous installation of three different functionalities, viz carbonyl, sulfonyl, and thiyl, takes place under one condition, while another condition leads to vicinal thiolation and sulfonylation. [ABSTRACT FROM AUTHOR]

Diarylacetylenes undergo anti -dimagnesiation using magnesium bromide and sodium dispersion to afford (E)-1,2-dimagnesioalkenes. This dimagnesiation utilizes simple magnesium bromide as a reduction-resistant electrophile, contrasting with the previously reported dimagnesiation using tricky organomagnesium halides. The resulting vicinal double Grignard reagents react with various electrophiles to yield multisubstituted alkenes stereoselectively. [ABSTRACT FROM AUTHOR]

Functionalized 1,2,4,5-tetrasubstituted benzenes are synthetically difficult or laborious to access. The Rh-catalyzed [2+2+2] cycloaddition of a diyne and internal alkyne offers a seemingly straightforward route to these scaffolds; however, this has been largely restricted to alkynes bearing activating (coordinating) functional groups, with very few examples of unactivated alkynes. In this work, we disclose an assessment of Rh-catalyzed [2+2+2] cycloadditions employing unactivated internal alkynes, focusing on the structural diversity and compatibility of both alkyne and diyne components. The limitations of this method are disclosed, with exceptionally bulky alkynes and specific functional groups undergoing side reactions. Furthermore, the practicalities of gram-scale reactions and catalyst recovery/reuse are demonstrated. [ABSTRACT FROM AUTHOR]

휋‐Conjugated polymers, including those based on acetylenic repeating units, are an exciting class of materials that offer narrow optical band gaps and tunable frontier orbital energies that lead to their use in organic electronics. This work expands the knowledge of structure‐property relationships of acetylenic polymers through the synthesis and characterization of a series of Glaser‐Hay‐coupled model compounds and random copolymers comprised of BF2 formazanate, fluorene, and/or bis(alkoxy)benzene units. The model compounds and copolymers synthesized exhibit redox activity associated with the reversible reduction of the BF2 formazanate units and the irreversible reduction of the fluorene and bis(alkoxy)benzene units. The copolymers exhibit absorption profiles characteristic or intermediate of their respective models and homopolymers, leading to broad absorption of UV–vis light. The alkyne linkages of the model compounds and copolymers are reacted with [Co2(CO)8] to convert the alkyne functional groups into cobalt carbonyl clusters. This transformation leads to blue‐shifted absorption profiles due to a decrease in π‐conjugation, demonstrating the ability to tune the properties of these materials through post‐polymerization functionalization. The redox activity and broad absorption bands of the polymers reported make them excellent candidates for use in photovoltaics and other light‐harvesting applications. [ABSTRACT FROM AUTHOR]

An N‐heterocyclic carbene palladium (NHC‐palladium)‐catalyzed denitrogenative coupling of aryldiazonium salts with terminal alkynes in ionic liquids has been accomplished. This catalytic strategy provides an effective and green synthetic protocol for the assembly of structurally diverse internal alkynes with excellent functional group compatibility and mild conditions. In the presence of 1 mol % of IMes‐Pd‐Im‐Cl2 as the catalyst, a wide range of terminal alkynes and aryldiazonium salts could be excellently tolerated. Basic ionic liquid plays a crucial role in this catalytic system, which not only acts as the green solvent, but also provides basic environment for the carbon‐carbon bond formation process. Notably, this catalytic system could be recycled up to six times and reused without significant loss of catalytic activity. [ABSTRACT FROM AUTHOR]

Alkynes have been the preferred substrates since the early development of gold catalysis at the dawn of this century. Amongst them, 1‐haloalkynes have gained increased interest in recent years due to the versatility offered by these bifunctional entities as well as the identification of unique reaction modes in this already mature research field. Herein, the seminal contributions that resulted in the observed growth in recent years and the most recent developments will be discussed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The multiple mortise‐and‐tenon joint parts are the core factors to provide the structural stability and diversity of Chinese Luban locks; however, constructing such structures is very challenging. Herein, single crystals of a covalent organic nanoribbon (named CityU‐27) are prepared through the assembly of hexahydroxytriphenylene (HHTP), 4,4′‐vinylenedipyridine (BYE), and phenylboronic acid (BA) together through dative boron←nitrogen (B←N) bonds. The single‐crystal X‐ray diffraction analysis indicates that CityU‐27 has a covalent organic nanoribbon structure, where each nanoribbon forms multiple and tight π–π interactions with four neighboring others to generate a Luban lock‐like configuration. CityU‐27 has been demonstrated to be an efficient photocatalyst in a one‐pot tandem reaction of hydrogen evolution reaction (HER) and semi‐hydrogenation reaction of alkynes in series to produce olefins without any additional photosensitizers and co‐catalysts (metal‐free). [ABSTRACT FROM AUTHOR]

We herein describe the first example of ligand‐controlled, copper‐catalyzed regiodivergent asymmetric difunctionalization of terminal alkynes through a cascade hydroboration and hydroallylation process. The catalytic system, consisting of (R)‐DTBM‐Segphos and CuBr, could efficiently achieve asymmetric 1,1‐difunctionalization of aryl terminal alkynes, while ligand switching to (S,S)‐Ph‐BPE could result in asymmetric 1,2‐difunctionalization exclusively. In addition, alkyl substituted terminal alkynes, especially industrially relevant acetylene and propyne, were also valid feedstocks for asymmetric 1,1‐difunctionalization. This protocol is characterized by good functional group tolerance, a broad scope of substrates (>150 examples), and mild reaction conditions. We also showcase the value of this method in the late‐stage functionalization of complicated bioactive molecules and simplifying the synthetic routes toward the key intermediacy of natural product (bruguierol A). Mechanistic studies combined with DFT calculations provide insight into the mechanism and origins of this ligand‐controlled regio‐ and stereoselectivity. [ABSTRACT FROM AUTHOR]

A general protocol for regioselective electrochemical [2 + 2] cyclization of N-acyl indoles with alkynes was described. This novel method was carried out under mild, chemical oxidant-free, and transition-metal-free conditions, with a broad substrate scope and good functional group tolerance to provide cyclobutene-fused indolines with high regioisomeric ratios and was readily scalable to the gram scale. Mechanistic studies have suggested that the selective reduction of radical cations at the cathode to form a double radical intermediate is the key step in the reaction. [ABSTRACT FROM AUTHOR]

Vinylsilanes are very useful building blocks in organic synthesis and have widespread applications in life sciences and materials chemistry. Here we describe the potential of complex cis‐[Fe(PCP‐iPr)(CH2CH2CH3)(CO)2] as an effective catalyst for the hydrosilylation of both terminal and internal alkynes with SiPhH3 to give vinylsilanes. The reactions were typically performed with a catalyst loading of 1 mol% for 24 h at 70 °C. The catalytic reaction is initiated by migratory insertion of a CO ligand into the Fe─alkyl bond to yield an acyl intermediate, which reacts with silanes to form the 16e− Fe(II) silyl catalyst [Fe(PCP‐iPr)(SiPhH2)(CO)]. In the case of aliphatic terminal alkynes good regioselectivity (anti‐Markovnikov addition) toward the thermodynamically more stable β‐(E)‐vinylsilanes in ratios of up to 10:90 was achieved, while for aromatic alkynes the selectivities were poor with ratios of β‐(Z)‐ to β‐(E)‐vinylsilanes of about 40:60. With internal unsymmetrical alkynes, the two possible regioisomers of the syn‐addition of SiPhH3 were obtained in different ratios with no clear trend toward one regioisomer. Internal symmetrical alkynes yielded exclusively the respective syn‐products in high yields. Mechanistic investigations including deuterium labelling studies were undertaken to provide a reasonable reaction mechanism. [ABSTRACT FROM AUTHOR]

A broad study on [4 + 1]- and [4 + 2]-cycloaddition reactions of a thiazole-2-thione-based 1,4-diphosphinine (1) is reported, with a special focus on reversible reactions. Reactions of 1 with group 13 carbenoids DippNacNacM (M = Al and Ga) afford [4 + 1] adducts that can be classified as Al and Ga phosphides or as 7-metalla-1,4-norbornadienes. Reactions of 1 with alkynes and alkenes result in [4 + 2]-cycloaddition, affording 1,4-diphosphabarrelenes. The effect of different dienophiles on the formation of 1,4-diphosphabarrelenes and their thermal [4 + 2]-cycloreversion reactions is studied from an experimental as well as theoretical point of view, opening the door for protection/deprotection strategies in this chemistry. [ABSTRACT FROM AUTHOR]

Metallacyclobutadienes (MCBDs) are key intermediates of alkyne metathesis reactions. There are in principle two isomerization pathway from kinetic to thermodynamic MCBDs, intermolecular and intramolecular. However, systems that simultaneously isolate two kinds of MCBD isomers have not been achieved, thus restricting the mechanistic studies of the isomerization. Here the reactivity of a metallapentalyne that contains an M≡C bond within the aromatic ring, with alkynes to afford a series of MCBD‐fused metallapentalenes is studied. In some cases, both kinetic and thermodynamic products are isolated in the same system, which has never been observed in previous MCBD reactions. Furthermore, the isomerization of MCBD‐fused metallapentalenes is investigated both experimentally and theoretically, indicating that it is an intramolecular process involving a metallatetrahedrane (MTd) intermediate. This research provides experimental evidence demonstrating that one MCBD can undergo intramolecular rearrangement to transform into another. [ABSTRACT FROM AUTHOR]

An efficient methodology for the synthesis of highly diverse 4-aminoquinoline derivatives from activated alkynes and 2-aminobenzonitriles mediated by Lewis acid is described. The reaction proceeds via sequential aza-Michael addition/intramolecular annulation to afford highly substituted 4-aminoquinolines in good yields. The reaction is operationally simple and has high atom-economy with broad substrate scope. The post synthetic application of the reaction provides 4 H -benzo[ de ][1,6]naphthyridines. [ABSTRACT FROM AUTHOR]

A silver-catalyzed dearomative decarboxylative [3+2] spiroannulation of aryl oxamic acids with alkynes is described. The reaction provides reliable access to a range of azaspiro[4,5]trienones in moderate yields in aqueous media. In addition, the reaction exhibits a broad substrate scope and good functional group compatibility. [ABSTRACT FROM AUTHOR]

Reductive functionalization of C–C unsaturated systems, including alkenes and alkynes, with a range of hydroelements (H[E]) is one of the most fundamental and highly practical methods for the synthesis of functionalized hydrocarbons. Since the resultant hydrocarbon products have strong applicability as synthetic intermediates, numerous homogeneous organo(metallic) catalysts have been intensively utilized to date for reductive functionalization reactions. In particular, well-defined transition-metal-based catalysts capable of controlling the regio- or stereoselectivity of a product by harnessing the addition of H[E] (E = H, B, Si, Ge) into Cα –Cβ unsaturated bonds have drawn special attention. In this review , we describe recent examples of transition-metal catalytic systems (M = Fe, Co, Rh, Pd, Ni) for regio- or stereodivergent hydroelementation reactions of (conjugated) alkenes, alkynes, and allenes to give a pair of isomeric products in high selectivities from the same starting compounds simply by variation of the ligand. Mechanistic aspects of the ligand-controlled selectivity divergence are discussed in detail on the basis of experimental observations and/or computational insights. 1 Introduction 2 Hydroelementation of Alkenes and Alkynes 3 Hydroelementation of Conjugated Dienes and Diynes 4 Hydroelementation of Allenes 5 Summary and Outlook [ABSTRACT FROM AUTHOR]

One-carbon ring expansion reaction of N-heterocycles has gained particular attention in the past decade because this method allows for the conversion of readily available N-heterocycles into potentially useful complex ring-expanded N-heterocycles, which are inaccessible by traditional methods. However, the catalytic asymmetric variant of this reaction has been rarely reported to date. Herein, we disclose an enantioselective one-carbon ring expansion reaction through chiral copper-catalyzed diyne cyclization, leading to the practical, atom-economic and divergent assembly of an array of valuable chiral N-heterocycles bearing a quaternary stereocenter in generally good to excellent yields with excellent enantioselectivities (up to >99% ee). This protocol represents the first example of asymmetric one-carbon ring expansion reaction of N-heterocycles based on alkynes. [ABSTRACT FROM AUTHOR]

Molecular platforms are essential components of various surface‐mounted molecular devices. Here, we document the synthesis of two universal triptycene‐based tripodal pedestals featuring terminal alkynes in the axial position. We showcase their versatility by incorporating them into the structures of diverse functional molecules such as unidirectional light‐driven molecular motors, photoswitches, and Brownian molecular rotors using standard cross‐coupling reactions. We also present their fundamental physical properties, including acidity constants, data from differential scanning calorimetry, and crystallographic analysis of two parent and five derived structures. Finally, and importantly, we demonstrate that the photochemical properties of selected photoswitch representatives remain uncompromised when fused with tripods. [ABSTRACT FROM AUTHOR]

In the absence of directing auxiliaries, catalytic addition of nucleophiles to unactivated alkynes with accurate control of regioselectivity remains an ongoing challenge in organic chemistry. Herein, we realized a Ag‐catalysed regiospecific hydration process of unactivated alkynes. Computational investigations offered insights into the origin of the regiochemical outcome. The practicability and efficacy of the protocol was exemplified by its simple reaction conditions without incorporation of acidic additives, as well as the tolerance of a wide range of alkynes equipped with various functional groups, leading to the ketone products in up to 98 % yield. Direct modification of bioactive organic molecules and gram‐scale experiments further showcased the application potential of the strategy. The catalyst control principles are expected to advance efforts towards the development of general site‐selective addition of nucleophile to unsaturated substrates, removing the requirement for neighboring activating groups. [ABSTRACT FROM AUTHOR]

A phenanthroline-type ligand containing an annealed 1,2,4-triazine ring was used to prepare novel Ir(III) complexes 3 and 4. The complexes are non-luminescent but show luminogenic behaviour following the inverse electron demand Diels–Alder (IEDDA) reaction with bicyclononyne (BCN) derivatives. It was observed that the complexes react with BCN-C10 faster than the corresponding free ligands. The magnitude of this accelerating metal-coordination effect, however, is less profound than in previously reported Ir(III) complexes of 1,2,4-triazines, in which the triazine was directly coordinated to the Ir(III) metal centre. Nevertheless, luminogenic behaviour opens prospects for the use of such complexes in bioimaging applications, which was demonstrated by developing a convenient methodology using the "chemistry on the complex" concept for labelling antibodies with luminescent Ir(III) complexes. The bioorthogonal reactivity of complex 4 was demonstrated by metabolically labelling live cells with BCN groups, followed by a luminogenic IEDDA reaction with the triazine iridium complex. [ABSTRACT FROM AUTHOR]

Described herein is a novel visible-light-promoted three-component radical iodo-alkylative cyclization of alkynes using iodoform as a bifunctional iodine atom source. Visible-light irradiation of a polar–polar interaction complex of iodoform with malonate enables the cooperative hydrogen atom transfer process to generate alkyl radical and trigger a cascade reaction sequence. [ABSTRACT FROM AUTHOR]

A catalyst‐based switchable regioselective C−H activation/annulation of acrylamides with propargyl carbonates has been developed, delivering C5 or C6 alkenyl substituted 2‐pyridones. This robust protocol proceeds with a broad substrate scope and good functional group tolerance under redox‐neutral reaction conditions. More significantly, this reaction is highly effective with previously challenging unsymmetrical alkynes, including unbiased alkyl‐alkyl substituted alkynes, with perfect and switchable regioselectivity. Additionally, mechanistic studies and DFT calculations were performed to shed light on the switchable regioselectivity. [ABSTRACT FROM AUTHOR]

Acetylene and methylacetylene are impurities commonly found in the raw materials used for the production of polymers such as polypropylene and polyethylene. Experimental evidence indicates that both acetylene and methylacetylene can decrease the productivity of the Ziegler-Natta catalyst and alter the properties of the resulting polymer. However, there is still a lack of understanding regarding the mechanisms through which these substances affect this process. Therefore, elucidating these mechanisms is crucial to develop effective solutions to this problem. In this study, the inhibition mechanisms of the Ziegler-Natta catalyst by acetylene and methylacetylene are presented and compared with the incorporation of the first propylene monomer (chain initiation) to elucidate experimental effects. The Density Functional Theory (DFT) method was used, along with the B3LYP-D3 functional and the 6-311++G(d,p) basis set. The recorded adsorption energies were −11.10, −13.99, and −0.31 kcal mol−1, while the activation energies were 1.53, 2.83, and 28.36 kcal mol−1 for acetylene, methylacetylene, and propylene, respectively. The determined rate constants were 4.68 × 1011, 5.29 × 1011, and 2.3 × 10−8 M−1 s−1 for acetylene, methylacetylene, and propylene, respectively. Based on these values, it is concluded that inhibition reactions are more feasible than propylene insertion only if an ethylene molecule has not been previously adsorbed, as such an event reinforces propylene adsorption. [ABSTRACT FROM AUTHOR]

Low‐energy light, endowing with excellent characteristics of lower energy, fewer side reactions, more abundance in solar light. The scenario has been developed for the fabrication of indenone through a low‐energy green light driven radical annulation reaction between α‐keto acids and internal alkynes using Rhodamine 6G as photocatalyst. Various kinds of substrates are suitable for this methodology, affording the corresponding indenones in a greener and efficient manner. [ABSTRACT FROM AUTHOR]

A convenient synthetic protocol for diverse 4, 5-disubstituted-6-methyl-2-(methylthio)pyrimidines was successfully developed by Sonogashira reactions. In the presence of Pd-Cu catalysts, one-pot, multi-step reaction of amines, terminal alkynes, and 4-chloro-5-iodo-6-methyl-2-(methylthio)pyrimidine in DMF at 80°C resulted in 4, 5-disubstituted-6-methyl-2-(methylthio)pyrimidine derivatives in moderate to good yields. [ABSTRACT FROM AUTHOR]

This study presents metal‐free protocols for the reduction radical coupling of enamides with diverse alkynes, triggered by 1,1,1,3,3,3‐Hexafluoro‐2‐propanol (HFIP), enabling access to β‐keto alkylamides. The established approach demonstrates remarkable efficiency, facile gram‐scale synthesis, and outstanding functional group tolerance. Mechanistic investigations have revealed that the radical reaction is initiated through H‐bonding electron transfer (Hb‐ET) between enamides and HFIP promoted by acids. Notably, the introduction of Hb‐ET protocols for generating radicals represents a highly promising approach in the field of radical chemistry. [ABSTRACT FROM AUTHOR]

Hydrophosphination and oxyphosphination are two important topical reactions in order to prepare organophosphorus derivatives from unsaturated derivatives such as alkenes and alkynes in a more sustainable fashion. Noticeably, metal catalysed versions have shown great interest and efficiency. By contrast, the use of earth abundant transition metal based catalysts for such transformations is less reported, even if there is a growing interest during the last decade. This review article reports and highlights recent developments using manganese, iron, cobalt, nickel and copper based catalysts for hydro‐ and oxyphosphination, notably exhibiting the selectivity, functional group tolerance, milder conditions and catalyst design. Even if significant progresses were made, the scopes are still rather limited (mainly focused on activated olefins such as styrenes) and chemo‐ and stereo‐selectivity issues still have to be solved, notably for asymmetric transformations. Of interest, the use of visible light including blue one as activator emerged, giving promising and stimulating results at ambient conditions. [ABSTRACT FROM AUTHOR]

Comprehensive Summary Key Scientists Electron‐rich alkynes, such as ynol and thioynol ethers, have proven to be versatile and appealing partners in catalytic cycloaddition reactions, and thus have raised considerable attentions owing to the practical application in the modular assembly of valuable carbo‐ and heterocycles. The past decades have witnessed inspiring advances in this emerging field, and an increasing number of related discoveries have been exploited. Divided into two main sections on the basis of substrate type, in each section this comprehensive review will initially summarize their synthetic preparations and subsequently examine their reactivity in every sort of catalytic cycloaddition with emphasis on the methodology development, aimed at providing an access to this burgeoning area and encouraging further innovations in the near future. For the cycloaddition of ynol ethers, in 2004, Kozmin et al. firstly developed a silver‐catalyzed [2 + 2] cycloaddition of siloxy alkynes with electron‐poor olefins. In 2012, Hiyama et al. realized a palladium‐catalyzed formal [4 + 2] annulation of alkynyl aryl ethers with internal alkynes. In the same year, Sun et al. discovered an efficient [6 + 2] cyclization between siloxy alkynes and 2‐(oxetan‐3‐yl)benzaldehydes by applying HNTf2 as catalyst. In 2017, Wender et al. first utilized vinylcyclopropanes (VCPs) as coupling partners in the [5 + 2] annulation of ynol ethers. In 2018 and 2020, Ye et al. reported zinc‐catalyzed formal [3 + 2] and [4 + 3] cycloaddition, respectively. For the cycloaddition of thioynol ethers, in 2004, Hilt et al. realized a [4 + 2] cycloaddition by employing the alkynyl sulfides and acyclic 1,3‐dienes. In 2006, a ruthenium‐catalyzed [2 + 2] cycloaddition of thioynol ethers with bicyclic alkenes was accomplished by Tam. In 2014, Sun et al. reported an elegant iridium‐catalyzed click reaction of thioalkynes with azides. [ABSTRACT FROM AUTHOR]

The direct synthesis of alkenes from alkynes usually requires the use of transition‐metal catalysts. Unfortunately, efficient biocatalytic alternatives for this transformation have yet to be discovered. Herein, the selective bioreduction of electron‐deficient alkynes to alkenes catalysed by ene‐reductases (EREDs) is described. Alkynes bearing ketone, aldehyde, ester, and nitrile moieties have been effectively reduced with excellent conversions and stereoselectivities, observing clear trends for the E/Z ratios depending on the nature of the electron‐withdrawing group. In the case of cyanoalkynes, (Z)‐alkenes were obtained as the major product, and the reaction scope was expanded to a wide variety of aromatic substrates (up to >99 % conversion, and Z/E stereoselectivities of up to >99/1). Other alkynes containing aldehyde, ketone, or ester functionalities also proved to be excellent substrates, and interestingly gave the corresponding (E)‐alkenes. Preparative biotransformations were performed on a 0.4 mmol scale, producing the desired (Z)‐cyanoalkenes with good to excellent isolated yields (63–97 %). This novel reactivity has been rationalised through molecular docking by predicting the binding poses of key molecules in the ERED‐pu‐0006 active site. [ABSTRACT FROM AUTHOR]

Hydroesterification of alkynes is a crucial synthetic transformation, enabling the formation of esters directly with high atom economy. Recent advancements have centered on improving the reaction's selectivity, efficiency, and environmental sustainability, particularly through the innovation of ligands and catalysts, making the process more practical for industrial applications. Herein, we report a highly selective and efficient hydroesterification of alkynes using a novel recyclable ligand, accommodating a wide range of alkyne substrates as well as various alcohols and phenols. The reaction proceeds under mild conditions, affording the desired esters in high yields with excellent regioselectivities. A notable feature of this method is the recyclability of the ligand, which can be recovered and reused multiple times without significant loss of activity or selectivity. Mechanistic studies revealed that palladium was well dispersed on the nanoscale and was essential for this sustainable hydroesterification process. [ABSTRACT FROM AUTHOR]

We report herein a synthetic strategy for the generation of direct selenothiocyanation from both terminal and internal alkynes via a radical process. Alkynes derived from bioactive molecules, such as L (−)-borneol and L -menthol, are suitable for selenothiocyanation reaction. This method features metal-free conditions and readily available reagents. [ABSTRACT FROM AUTHOR]

Precisely designing asymmetrical structures is an effective strategy to optimize the performance of metallic catalysts. Asymmetric Pt clusters were attached to defect-rich porous alumina nanosheets (Pt clu/dp-Al2O3) using a pyrolysis technique coupled with wet impregnation. These Pt-functionalized nanosheets feature a high concentration of active sites, demonstrating remarkable cycling performance and catalytic activity in alkyne diboration. The conversion yield and selectivity can reach up to 97% and 95%, correspondingly. [ABSTRACT FROM AUTHOR]

The present review discusses the development of new metal‐free conditions for the hydroacylation of alkenes and alkynes under both thermal and photochemical conditions from 2018, and their application to the synthesis of various bioactive molecules over the past few years. The key point highlights the remarkable progress made by metal‐free catalytic systems in comparison to the conventional metal catalysts in the hydroacylation of alkenes, alkynes, and arenes. Both inter‐ and intramolecular hydroacylation reactions and their mechanistic pathways were discussed. The most current developments in the synthesis of several natural, pharmaceutical, and heterocyclic compounds using hydroacylation reactions have also been introduced. [ABSTRACT FROM AUTHOR]

Gold(III) complexes containing trifluoromethyl ligands are efficient catalysts in the hydration of alkynes, operating at low catalyst loadings, without additives, using environmentally friendly solvents and at mild conditions (60 °C). Hydration of terminal and internal alkynes provides the corresponding ketones in quantitative yields without special precautions as dry solvents or inert atmospheres. Remarkably, hydration of asymmetric internal alkynes proceeds with moderate to notable regioselectivities, providing mixtures of the two possible isomers with ratios up to 90 : 10. [ABSTRACT FROM AUTHOR]

Alkynes are simple yet important organic feedstocks. The selenylation of alkynes is able to produce complex selenium‐containing compounds in a facile way. Although there are some reviews about the selenylation of alkynes, most of them focus on one specific reaction or what types of products that can be obtained. There is a lack of attention given to the various uses of different selenium reagents and their mechanisms. This review mainly focuses on recent advances (2013–2023) based on diverse selenium reagents. Mechanisms and how the added reagents work will be discussed. Different reaction types, including difunctionalization, Se‐annulation, spiro‐cyclization, C−Se coupling, click reaction will be recorded in this review. The regioselectivity can be achieved through various mechanisms, including radicals, seleniraniums or electrophilic cyclization. We hope it will do help for future research in this area. [ABSTRACT FROM AUTHOR]

We have developed the Rh‐catalyzed enantioselective [2+2+2] cycloaddition of homopropargyl enamides (tosylamide‐tethered 1,6‐enynes) with alkynes to construct tetrahydroindole skeletons found in natural alkaloids and pharmaceuticals. This cycloaddition proceeds at room temperature in high yields and regio‐ and enantioselectivity with a broad substrate scope. The preparative scale reaction followed by substituent conversion on the nitrogen atom and the diastereoselective [4+2] cycloaddition with singlet O2 affords hexahydroindole‐diols bearing three stereogenic centers and variable substituents on the nitrogen. Mechanistic studies have revealed that the substituents of the enynes change the ratio of intramolecular and intermolecular rhodacycle formation when using terminal alkynes, varying the ee values of the cycloadducts. [ABSTRACT FROM AUTHOR]

The mechanism of an iron‐catalyzed C—H alkenylation of pivalophenone derivatives with unsymmetric internal alkynes is investigated in details by means of density functional theory calculations. It is shown that the reaction begins with two consecutive ligand exchanges, followed by a fast and reversible oxidative addition C—H activation step. Next, an alkyne insertion into the Fe—H bond, two isomerization steps, and a reductive elimination afford the final product. The reductive elimination is the turnover‐limiting step of the process, and also determines the regiochemical outcome of the reaction. The origin of the regioselectivity is proposed to be the steric repulsion between the bulky trimethylsilyl group and the aromatic fragment in the reductive elimination step leading to the not observed regioisomer. [ABSTRACT FROM AUTHOR]

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]

Heteropolycyclic molecular systems, which are essential components in the fields of materials and pharmacology, frequently consist of 2D extended organic aromatic rings. Here, we introduce a type of inorganic-organic hybrid 3D conjugates by merging an aromatic boron cluster with a phosphine and a π-conjugated unit. To achieve this, a couple-close synthetic strategy via B–H activation of nido-carboranes with alkynes has been developed, which leads to diverse boron cluster-extended phosphoniums in a twisted structure with high yields under mild conditions. Experimental and theoretical results reveal that the fusion between the boron cluster and the formed borophosphonium heterocycle facilitates electron delocalization throughout the structure. The unusual framework demonstrates distinct properties from bare boron clusters and pure aromatic ring-extended counterparts, such as improved thermal/chemical stability and photophysical properties. Thus, the boron cluster-based 3D conjugates expand the library of aromatic-based heterocyclics, showcasing great potential in functional materials. 2D π-conjugated systems incorporated with heteroatoms can suffer from stability issues and aggregation-induced quenching effects. Here, the authors develop a methodology for the synthesis of cluster-ring-fused 3D aromatic heterocycles, which could find use in functional materials, via the palladium-catalyzed B–H activation of boron clusters. [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]

5-(4,5-Dihydro-1H-pyrazol-3-yl)isoxazoles (pyrazoline-isoxazoles) are readily oxidized by active manganese dioxide in benzene or dichloromethane at room temperature. As a result, a simple and efficient method for the synthesis of the corresponding pyrazoleisoxazoles in 94–99% yields was developed. It was shown that 3-ethynyl-1H-pyrazoles are inactive in the 1,3-dipolar cycloaddition reaction with nitrile oxides and nitrile imines. The synthesized di- and trisubstituted pyrazole-isoxazoles showed weaker luminescent properties compared to pyrazoline-isoxazoles. [ABSTRACT FROM AUTHOR]

1-Iodoalkynes are one type of the most reactive and the most practical intermediates in organic synthesis. Here, some facile and efficient methods for the 1-iodination of terminal alkynes are developed using N-iodosuccinimide (NIS) as an iodination reagent and some inexpensive mild bases as catalysts. K2CO3 and 4-dimethylaminopyridine (DMAP) have been proven to be the most suitable inorganic and organic bases, succeeding in 17 examples with excellent yields (up to 99%). [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]

Reactions of a dicopper(I) tert-butoxide complex with alkynes possessing boryl or silyl capping groups resulted in formation of unprecedented tetracopper(I) μ-acetylide/diyne complexes that were characterized by NMR and UV/Vis spectroscopy, mass spectrometry and single-crystal X-ray diffraction. These compounds possess an unusual μ4 -η1 :η1 :η1 :η1 coordination mode for the bridging organic fragment, enforced by the rigid and dinucleating nature of the ligand utilized. Thus, the central π system remains unperturbed and accessible for subsequent reactivity and modification. This has been corroborated by addition of a fifth copper atom, giving rise to a pentacopper acetylide complex. This work may provide a new approach by which metal-metal cooperativity can be exploited in the transformation of acetylide and diyne groups to a variety of substrates, or as a starting point for the controlled synthesis of copper(I) alkyne-containing clusters.

There is an urgent need for improved therapy to better control the ongoing COVID-19 pandemic. The main protease Mpro plays a pivotal role in SARS-CoV-2 replications, thereby representing an attractive target for antiviral development. We seek to identify novel electrophilic warheads for efficient, covalent inhibition of Mpro. By comparing the efficacy of a panel of warheads installed on a common scaffold against Mpro, we discovered that the terminal alkyne could covalently modify Mpro as a latent warhead. Our biochemical and X-ray structural analyses revealed the irreversible formation of the vinyl-sulfide linkage between the alkyne and the catalytic cysteine of Mpro. Clickable probes based on the alkyne inhibitors were developed to measure target engagement, drug residence time, and off-target effects. The best alkyne-containing inhibitors potently inhibited SARS-CoV-2 infection in cell infection models. Our findings highlight great potentials of alkyne as a latent warhead to target cystine proteases in viruses and beyond.

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]