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A concise hydrosilylation of alkynes for synthesizing β‐(E)‐vinylsilanes catalyzed by dirhodium(II)/XantPhos has been developed. In this reaction, β‐(E)‐vinylsilanes were generated from the isomerization of β‐(Z)‐vinylsilanes catalyzed by dirhodium(II) hydride species rather than the direct insertion of triple bond into M−H or M−Si bond (traditional Chalk‐Harrod mechanism or modified Chalk‐Harrod mechanism). The hydrosilylation displayed a broad substrate scope for alkynes and tertiary silanes, tolerating diverse functional groups including halides, nitriles, amines, esters, and heterocycles. [ABSTRACT FROM AUTHOR]

Modular access to alkenylsilanes was reported via nickel-catalyzed regiodivergent and stereoselective hydrosilylation of disubstituted alkynes. Herein, strategic use of an amide backbone and the appropriate selection of ligands allows highly regiocontrol and stereocontrol in the key syn -silametallation step. [Display omitted] [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]

The trans‐addition of intermetallic σ‐bonds (E−E′; E E'=Si, B, Se, P, Sn, etc.) across alkynes has emerged as an exceptionally atom‐economical means of constructing multi‐substituted alkenes, which readily transform into densely functionalized and biologically active compounds. Compared to the widely studied cis‐E−E' additions, trans‐E−E' additions remain a more challenging and underdeveloped area. In this article, recent advances in trans‐E−E' additions are summarized, encompassing various interelement compounds such as Si−Si, B−B, Si−B, P−B, Se−B, and B−Sn. We aim to provide a deeper understanding of trans‐E−E' additions and facilitate the further development of synthetic methodologies and applications of vicinally trans‐bismetallated alkenes. [ABSTRACT FROM AUTHOR]

Here, we present the synthesis of polysubstituted chalcogenofurans involving an oxidative cycloaddition between 1,3‐diones and chalcogenoalkynes. The method utilizes blue LEDs as a clean energy source, methylene blue as a photocatalyst – an inexpensive and non‐toxic dye – and ammonium persulfate as an oxidant, all conducted at room temperature. This benign protocol enables access to a wide range of chalcogenofurans with good to excellent yields and outstanding regioselectivity. Only one regioisomer was obtained, indicating strong radical stabilization by the chalcogen atom. Various functionalities in both alkynes and 1,3‐diones demonstrated amenability to the developed reaction. A mechanistic understanding, derived from control experiments and the detection of radical intermediates, suggests that a radical forms at the carbon‐2 position of the 1,3‐dione, which subsequently adds to the chalcogenoalkyne, resulting in the formation of an olefinic intermediate. Following this, an intramolecular radical addition occurs, which, upon photoredox cycle closure, leads to the formation of the desired products. [ABSTRACT FROM AUTHOR]

A bisphosphirane‐fused anthracene (5) was prepared by treatment of a sterically encumbered amino phosphorus dichloride (3) with MgA ⋅ THF3 (A=anthracene). X‐ray diffraction analysis revealed a pentacyclic framework consisting of 5 with two phosphirane rings fused to the anthracene in a trans‐fashion. Compound 5 has been shown to be an efficient phosphinidene synthon, readily liberating two transient phosphinidene units for subsequent downstream bond activation via the reductive elimination of anthracene under mild conditions. The formal oxidative addition of H2 and E−H (E=Si, N, P) bonds by the liberated phosphinidene provided diphosphine and substituted phosphines. Furthermore, phosphinidene transfer to alkenes and alkynes smoothly yielded the corresponding phosphiranes and phosphirenes. The mechanism of the H2 activation by 5 was investigated by density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]

Comprehensive Summary Alkenylsulfonates are commonly encountered in medicinal chemistry, polymer chemistry, and organic synthesis. In this research, an electrochemical reaction involving alkynes, NaHSO3, and alcohols has been developed. This method yields functionalized alkenylsulfonates in good yields with broad functional group tolerance. Mechanism studies indicate that anodic oxidation of inorganic sulfite, radical insertion process, and HAT process are involved in this transformation. [ABSTRACT FROM AUTHOR]

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]

Ligand-protected metal nanoclusters provide an ideal platform for investigating photoredox catalysis. The central challenge is balancing their stability and catalytic activity. Here we show a photochemical reduction–oxidation cascade method for synthesizing an Au8Cu6 nanocluster, which features a robust structure and active surface. Photoredox catalytic activity of Au8Cu6 is developed for the functionalization of alkynes under oxidative conditions. Mechanism studies based on the precise structure reveal the catalytic process of the Au8Cu6 nanocluster. Oxidant-dependent selectivity of Au8Cu6 catalysis is developed for chemodivergent synthesis of mono- and di-functionalized products in high efficiency. The results will stimulate more research on metal nanocluster synthesis and catalysis. Ligand-protected metal nanoclusters provide an ideal platform for investigating the balance of stability and activity in photoredox catalysis. Here, the authors apply a photochemical reduction–oxidation cascade method to synthesize an Au8Cu6 nanocluster with a robust structure and active surface. [ABSTRACT FROM AUTHOR]

A route for the construction of benzofulvenes derivatives through 4‐Aminobenzotriazole (ABTA) directed Pd‐catalyzed cascade reactions of amides with inner alkynes was developed. This method afforded a diverse array of benzofulvene derivatives in yields ranging from 34% to 91%. The control experiments indicated that the substrate reacts with alkynes in tandem to synthesize 1,3‐diene intermediates, and ultimately 1,3‐diene underwent intramolecular cyclization to produce benzofulvene derivatives. Furthermore, the directing group can be removed. [ABSTRACT FROM AUTHOR]

The reaction between aldehydes or ketones and alkynes—the carbonyl‐alkyne metathesis—constitutes a very useful strategy for the synthesis of α,β‐unsaturated carbonyls. We now demonstrate that iodine is a highly efficient catalyst for both the intra‐ and intermolecular metathesis reaction in very small concentrations (0.1–1 mol %). Our protocol outperforms other catalytic systems, is operationally very simple, cheap, metal‐free, and tolerates a large variety of functional groups (e. g. −CN, −CO2Me, −Br, −OH) at very low catalyst loadings. We can furthermore show that iodine‐catalyzed carbonyl‐alkyne metatheses can be combined with other iodine‐catalyzed reactions in one‐pot procedures to afford larger and more complex molecular structures. Finally, our mechanistic studies indicate that the iodonium ion is the active catalyst under the reaction conditions. [ABSTRACT FROM AUTHOR]

An efficient and cost‐effective Cu (I) mediated protocol for the C(sp2)–C(sp) cross‐coupling of 3‐chalcone‐2‐chloroquinoline with terminal alkynes has been disclosed by optimizing a wide range of catalysts, ligands, base, and solvents. This approach conveniently assembles various alkynylated hybrids with excellent to moderate yields. Appropriate functional group tolerance and significant mechanistic pathway with mild reaction conditions well‐justified this synthetic transformation more sustainable towards the greener exploration. [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]

Carbon‐carbon bond forming reactions are powerful synthetic tools for constructing organic molecular frameworks. In this study, strongly Lewis acidic bis(pentafluorophenyl)boron enolates were generated from alkynes through oxygen transfer from 2,6‐dibromopyridine N‐oxide using tris(pentafluorophenyl)borane [B(C6F5)3]. Boron enolates were highly reactive owing to the strong Lewis acidity of the boron centers, and thus immediately coupled with alkynes. N‐Ethynylphthalimide reacted as an alkyne with 2,6‐dibromopyridine N‐oxide and B(C6F5)3 to form a semi‐stable bis(pentafluorophenyl)boron enolate through the coordination of the carbonyl group to the boron center. This enolate underwent coupling with another alkyne. [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]

The activation of various homopropargylic pyridines by cis‐[RuII/OsII(dppm)2Cl2] (dppm=1,1‐bis(diphenylphosphino)methane) has previously been shown to generate a diverse array of metallacycles and metalated heterocyclic complexes. However, a minor structural modification of introducing a halide onto the pyridyl group of the alkyne substrate resulted in the formation of unprecedented Ru(II)/Os(II)−haloquinolizine complexes. These complexes display (1) κ2(X,C)‐haloquinolizine chelates arising from the cycloisomerization of HC≡CC(OH)(CH2(6‐X‐2‐py))(Ph) on [RuII/OsII(dppm)2]2+ moieties via a vinylidene pathway, (2) five‐membered Ru/Os−X−C−N−C rings (X=F, Cl, Br) ortho‐ and peri‐fused to quinolizinium skeletons, and (3) uncommon M−X−R bonding interactions that are atypical in coordination complexes. Despite being divalent and integrated into a five‐membered Ru−X−C−N−C ring system, the X atoms in the Ru(II) complexes are susceptible to substitution by O in the presence of −OH, resulting in the formation of quinolizinium‐fused ruthenaoxazole complexes. Overall, this work highlights the importance of considering metal−halocarbon bonding interactions in catalytic or coordination designs. [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]

Transition metal-catalyzed addition of organometallics to aryl(alkyl)alkynes has been well known to proceed with the regioselectivity in forming a carbon–carbon bond at the alkyl-substituted carbon (β-addition). Herein, the reverse regiochemistry with high selectivity in giving 1,1-diarylalkenes (α-addition) was realized in the reaction of arylboronic acids with aryl(alkyl)alkynes by use of a rhodium catalyst coordinated with a chiral diene ligand, whereas the arylation of the same alkynes proceeded with the usual regioselectivity (β-addition) in the presence of a rhodium/DM-BINAP catalyst. The regioselectivity can be switched by the choice of ligands on the rhodium catalysts. This reverse regioselectivity also enabled the catalytic asymmetric synthesis of phoenix-like axially chiral alkylidene dihydroanthracenes with high enantioselectivity through an α-addition/1,4-migration/cyclization sequence. Transition-metal-catalysed additions of carbon species to aryl(alkyl)alkynes is an established and useful methodology for building towards useful molecular complexity. Here, the authors present rhodium-catalysed regiodivergent additions to aryl(alkyl)alkynes, which allows access to the uncommonly found α-addition products through modulation of the ligand choice. [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]

A new approach for the preparation of 3-alkenyl furans and thiophenes by selective C3–H alkenylation of furan-2- and thiophene-2-carboxylic acids with internal alkynes has been developed, and novel 3-alkenylated furans and thiophenes have been synthesized and characterized. The main advantages of the developed approach are the use of readily available substrates in which the COOH function serves as a traceless in situ removable directing group, the high regioselectivity of the C3–H alkenylation, which provides easy access to C3-alkenylated furans and thiophenes with highly reactive C2–H and C5–H bonds that are difficult to access by previously reported methods, and the use of a relatively inexpensive [RuCl2(p-cymene)2] precatalyst in the absence of copper and silver promoters. [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]

The cyclization of heteroatom‐functionalized alkynes induced by d6‐transition‐metal centers has traditionally been associated with the vinylidene pathway. However, recent evidence suggests that d6‐transition‐metal centers can also activate alkynes through non‐vinylidene pathways. In this study, we conducted a comprehensive experimental and theoretical investigation into the reactions between the Ru(II) complex [Ru([9]aneS3)(bpy)(OH2)]2+ and 2‐alkynylanilines. Our study revealed that the selectivity between the vinylidene and non‐vinylidene pathways can be tuned by reaction temperature, substrate, and solvent polarity. This strategic control allows for the preferential formation of either C2‐ or C3‐metalated indole zwitterion complexes. Additionally, we identified a rare decyclization mechanism that enables the conversion of C2‐metalated indoles to C3‐metalated indoles, underscoring the significance of product stability in these pathways. Overall, this work demonstrates practical approaches to control the preference between vinylidene and non‐vinylidene pathways, which is crucial for the design of new catalysts and metalated heterocyclic complexes. [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]

Hydration reactions consist of the introduction of a molecule of water into a chemical compound and are particularly useful to transform alkynes into carbonyls, which are strategic intermediates in the synthesis of a plethora of compounds. Herein we demonstrate that L–cysteine can catalyse the hydration of activated alkynes in a very effective and fully regioselective manner to access important building blocks in synthetic chemistry such as β‐ketosulfones, amides and esters, in aqueous media. The mild reaction conditions facilitated the integration with enzyme catalysis to access chiral β‐hydroxy sulfones from the corresponding alkynes in a one‐pot cascade process in good yields and excellent enantiomeric ratios. These findings pave the way towards establishing a general method for metal‐free, cost‐effective, and more sustainable alkyne hydration processes. [ABSTRACT FROM AUTHOR]

Alkynyl amides play crucial roles in organic synthesis in the production of bioactive compounds and valuable heterocycles. Despite numerous studies on their synthesis, challenges persist due to the necessity of harsh or hazardous conditions and the use of costly or unstable reagents. Herein, we present a one‐pot method for the synthesis of all three bonds of the alkyne under transition‐metal‐free conditions. An important feature of this chemistry is the use of readily available feedstock chemicals, such as methyl esters and acetamides. This approach offers efficient access to a wide range of aryl and alkyl alkynyl amides and demonstrates excellent tolerance towards various functional groups in a sustainable and cost‐effective manner. [ABSTRACT FROM AUTHOR]

The intramolecular 1,2‐aminoboration of alkynes by aminoboranes is rare and invariably requires a catalyst to proceed, while the intermolecular aminoboration of alkynes is yet entirely unknown. Through an exploration of the significance of electronics in alkynes for activating the B−N σ‐bond of aminoboranes, we demonstrate in this work the first intermolecular 1,2‐aminoboration of alkynes. These reactions employ a series of (amino)dihaloboranes and aminoboronic esters, mild reaction conditions, and no catalysts, yielding syn‐addition alkene products with the incorporation of two crucial functionalities: amino and boryl. While highly electron‐rich examples can afford the aminoborated products (Z)‐2‐borylethenamines, other alkynes, including unactivated and less electron‐rich examples, do not lead to the corresponding aminoborated products due to the fundamental impediment that the reactions are significantly endergonic. [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]

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]