Coupling Of Terminal Alkynes Research Articles

Insights Into the Magnesium‐Catalyzed C−C Coupling of Terminal Alkynes with Carbodiimides

AbstractThe bis‐guanidinate anion stabilized amido magnesium (II) compound [LMgN(SiMe3)2; L={(ArHN)(ArN)−C=N−C=(NAr)(NHAr); Ar=2,6‐Et2−C6H3}] (Mg‐1) has been synthesized and characterized. It has been successfully employed as a pre‐catalyst for the catalytic C−C coupling of terminal alkynes with carbodiimides, producing propiolamidine products with moderate to good yields. The active catalyst bis‐guanidinate magnesium acetylide [LMgC≡C−Ph]2 (Mg‐2) and the intermediate magnesium propiolamidinate [LMg{(NiPr)2C}C≡C−Ph] (Mg‐3) involved in the catalytic reaction were isolated and thoroughly characterized through multinuclear NMR and mass spectral analyses, as well as single crystal X‐ray diffraction studies. Based on the above findings, a plausible mechanistic cycle has been proposed. Additionally, a new example of bis‐guanidinate supported structurally characterized magnesium propiolamidate compound [LMg{(4−CH3−C6H4)N−(C−C≡C−Ph)=O]2 (Mg‐4) has been described via the reaction between Mg‐2 and isocyanate.

Copper on charcoal: copper nanoparticles catalyzed for highly efficient aerobic oxidative coupling of terminal alkynes

Copper on charcoal: copper nanoparticles catalyzed for highly efficient aerobic oxidative coupling of terminal alkynes

Universal inter-molecular radical transfer reactions on metal surfaces.

On-surface synthesis provides tools to prepare low-dimensional supramolecular structures. Traditionally, reactive radicals are a class of single-electron species, serving as exceptional electron-withdrawing groups. On metal surfaces, however, such species are affected by conduction band screening effects that may even quench their unpaired electron characteristics. As a result, radicals are expected to be less active, and reactions catalyzed by surface-stabilized radicals are rarely reported. Herein, we describe a class of inter-molecular radical transfer reactions on metal surfaces. With the assistance of aryl halide precursors, the coupling of terminal alkynes is steered from non-dehydrogenated to dehydrogenated products, resulting in alkynyl-Ag-alkynyl bonds. Dehalogenated molecules are fully passivated by detached hydrogen atoms. The reaction mechanism is unraveled by various surface-sensitive technologies and density functional theory calculations. Moreover, we reveal the universality of this mechanism on metal surfaces. Our studies enrich the on-surface synthesis toolbox and develop a pathway for producing low-dimensional organic materials.

Metal–Ligand Cooperative Catalytic Coupling of Terminal Alkynes and Carboxylic Acids for the Stereoselective Synthesis of Dienyl Esters

Metal–Ligand Cooperative Catalytic Coupling of Terminal Alkynes and Carboxylic Acids for the Stereoselective Synthesis of Dienyl Esters

Photocatalytic oxidative coupling of terminal alkynes with p-benzoquinone to diaryl ketones by the Cu(I)-PS-POM assembling system through synergistic effect

Photocatalytic C–C bonds formation is an effective approach to synthesize the significant drug intermediates diaryl ketones. Herein, a new polyoxometalate-based metal–organic framework (POMOF), CuW6–TPT, was synthesized by assembling an oxidation catalyst [W6O19]2− into photoactive MOF constructed by photosensitizer (PS) 4,6-tri(4-pyridyl)-1,3,5-triazine (TPT) and binuclear Cu(I) units. CuW6–TPT exhibits excellent light absorption ability and unique conductivity due to the coordination bond, strong π∙∙∙π interactions and H-bonding among Cu(I) ions, TPT moieties and [W6O19]2− in the defined spatial. The abundant exposed Cu(I) catalytic centres are conductive to activate phenylacetylene in situ formation Cu(I)-phenylacetylide, which then undergoes a reductive single electron transfer (SET) process to obtain the key intermediate Cu(II)-phenylactetylide for the Paterno-Buchi (2+2) cycloaddition with benzoquinone to form the labile Cu(II)-oxetane ring. It is a direct route to synthesize diaryl ketones with a hydroxyl group from simple starting materials such as terminal alkynes with p-benzoquinone.

Dual Catalysis of Gold Nanoclusters: Photocatalytic Cross-Dehydrogenative Coupling by Cooperation of Superatomic Core and Molecularly Modified Staples.

Thiolate-protected gold nanoclusters (AuNCs) have attracted significant attention as nano-catalysts, revealing a superatomic core and gold-thiolate staples as distinct structural units. Here, we demonstrate the unprecedented dual catalytic activity of thiolate-protected [Au25 (SR)18 ]- nanoclusters, involving both photosensitized 1 O2 generation by the Au13 superatomic core and catalytic carbon-carbon bond formation facilitated by Au2 (SR)3 staples. This synergistic combination of two different catalytic units enables efficient cross-dehydrogenative coupling of terminal alkynes and tertiary aliphatic amines to afford propargylamines in high yields of up to 93 %. Mixed-ligand AuNCs bearing both thiolate and alkynyl ligands revealed the intermediacy of the alkynyl-exchanged AuNCs toward both photosensitization and C-C bond-forming catalytic cycles. Density functional theory calculations also supported the intermediacy of the alkynyl-exchanged AuNCs. Thus, the use of ligand-protected metal nanoclusters has enabled the development of an exceptional multifunctional catalyst, wherein distinct nanocluster components facilitate cooperative photo- and chemo-catalysis.

Dual Catalysis of Gold Nanoclusters: Photocatalytic Cross‐Dehydrogenative Coupling by Cooperation of Superatomic Core and Molecularly Modified Staples**

AbstractThiolate‐protected gold nanoclusters (AuNCs) have attracted significant attention as nano‐catalysts, revealing a superatomic core and gold‐thiolate staples as distinct structural units. Here, we demonstrate the unprecedented dual catalytic activity of thiolate‐protected [Au25(SR)18]− nanoclusters, involving both photosensitized 1O2 generation by the Au13 superatomic core and catalytic carbon‐carbon bond formation facilitated by Au2(SR)3 staples. This synergistic combination of two different catalytic units enables efficient cross‐dehydrogenative coupling of terminal alkynes and tertiary aliphatic amines to afford propargylamines in high yields of up to 93 %. Mixed‐ligand AuNCs bearing both thiolate and alkynyl ligands revealed the intermediacy of the alkynyl‐exchanged AuNCs toward both photosensitization and C−C bond‐forming catalytic cycles. Density functional theory calculations also supported the intermediacy of the alkynyl‐exchanged AuNCs. Thus, the use of ligand‐protected metal nanoclusters has enabled the development of an exceptional multifunctional catalyst, wherein distinct nanocluster components facilitate cooperative photo‐ and chemo‐catalysis.

Stereospecific and Regioselective Synthesis of E-Allylic Alcohols through Reductive Cross Coupling of Terminal Alkynes.

We have developed a convergent method for the synthesis of allylic alcohols that involves a reductive coupling of terminal alkynes with α-chloro boronic esters. The new method affords allylic alcohols with excellent regioselectivity (anti-Markovnikov) and an E/Z ratio greater than 200:1. The reaction can be performed in the presence of a wide range of functional groups and has a substrate scope that complements the stoichiometric alkenylation of α-chloro boronic esters performed using alkenyl lithium and Grignard reagents. The transformation is stereospecific and allows for the robust and highly selective synthesis of chiral allylic alcohols. Our studies support a mechanism that involves hydrocupration of the alkyne and cross-coupling of the alkenyl copper intermediate with α-chloro boronic esters. Experimental evidence excludes a radical mechanism of the cross-coupling step and is consistent with the formation of a boron-ate intermediate and a 1,2-metalate shift.

A Simple and Practical Bis-N-Heterocyclic Carbene as an Efficient Ligand in Cu-Catalyzed Glaser Reaction.

Conjugated diyne derivatives are important scaffolds in modern organic synthetic chemistry. Using the Glaser reaction involves the coupling of terminal alkynes which can efficiently produce conjugated diyne derivatives, while the use of a stoichiometric amount of copper salts, strong inorganic base, and excess oxidants is generally needed. Developing an environmentally friendly and effective method for the construction of symmetrical 1,3-diynes compounds by Glaser coupling is still highly desirable. In this study, we present an economical method for the production of symmetric diynes starting from various terminal acetylenes in a Glaser reaction. A simple and practical bis-N-heterocyclic carbene ligand has been introduced as efficient ligands for the Cu-catalyzed Glaser reaction. High product yields were obtained at 100 °C for a variety of substrates including aliphatic and aromatic terminal alkynes and differently substituted terminal alkynes including the highly sterically hindered substrate 2-methoxy ethynylbenzene or 2-trifluoromethyl ethynylbenzene and a series of functional groups, such as trifluoromethyl group, ester group, carboxyl group, and nitrile group. The established protocol is carried out in air under base-free condition and is operationally simple. These research work suggest that bis-N-heterocyclic carbene could also an appealing ligand for Glaser reaction and provide a reference for the preparation of symmetric 1,3-diynes in industrial filed.

Oxidation coupling of terminal alkynes over CuPd bimetallic alloy enhanced by optimized charge transfer and alloy structure

Homocoupling of terminal alkynes is an effective approach for the synthesis of 1,3-diyne, which is an important building block for numerous fine chemicals and pharmaceuticals. However, this reaction frequently encounters difficulties in catalyst recovery, and requires the addition of base or organic ligands, limiting their practical applications. Herein, we developed an efficient and recyclable CuPd bimetallic nanoalloy catalyst, which exhibited superior activity and selectivity in the homocoupling of terminal alkynes under mild conditions without any additives. In contrast to the low activity of monometallic Cu or Pd catalysts, a full conversion with a 100% selectivity for 1,3-diyne was achieved on bimetallic Cu2Pd1-400 nanoalloy with an extremely high activity. The comprehensive characterizations clearly evidenced that the alloying Cu with Pd was found to perturb the Cu electronic structure, and the positively charged Cu on the step and edge sites of CuPd nanoalloy catalyzed the homocoupling reaction via Cu-acetylide intermediates, and the density functional theory calculations revealed that the desorption of 1,3-diyne on CuPd nanoalloy was the rate-determining step for the whole reaction. This work provides a viable strategy for the rational design and fabrication of other nanoalloy catalysts for the green synthesis related to terminal alkyne oxidation.

Ruthenium‐Catalyzed C−C Coupling of Terminal Alkynes with Primary Alcohols or Aldehydes: α,β‐Acetylenic Ketones (Ynones) via Oxidative Alkynylation

AbstractThe first metal‐catalyzed oxidative alkynylations of primary alcohols or aldehydes to form α,β‐acetylenic ketones (ynones) are described. Deuterium labelling studies corroborate a novel reaction mechanism in which alkyne hydroruthenation forms a transient vinylruthenium complex that deprotonates the terminal alkyne to form the active alkynylruthenium nucleophile.

Ruthenium-Catalyzed C-C Coupling of Terminal Alkynes with Primary Alcohols or Aldehydes: α,β-Acetylenic Ketones (Ynones) via Oxidative Alkynylation.

The first metal-catalyzed oxidative alkynylations of primary alcohols or aldehydes to form α,β-acetylenic ketones (ynones) are described. Deuterium labelling studies corroborate a novel reaction mechanism in which alkyne hydroruthenation forms a transient vinylruthenium complex that deprotonates the terminal alkyne to form the active alkynylruthenium nucleophile.

Silica-grafted DBU-supported NiCl2: a sustainable heterogeneous catalyst for A3 coupling

Silica-grafted DBU-supported NiCl2 complex, 1-(3-((3-(silica-trioxysilyl) propyl) amino) propyl) azepan-2-one nickel chloride (SiO2@DBU-NiCl2), has been designed and synthesized by multistep approach and characterized by FT-IR, XRD, EDS, FE-SEM, TGA and XPS. Catalytic activity of SiO2@DBU-NiCl2 has been explored for A3 coupling of terminal alkynes, aldehydes and secondary amines resulting in excellent yields (up to 97%). Special features of present protocol are high TONs (625–1212) and TOFs (52–404), low catalyst loading (0.08 mol %), solvent-free conditions, facile recyclability and reusability of the catalyst (up to 5 times).

Stereoselective Synthesis of Functionalized 1,3‐Enynes through Recyclable Copper(I)‐Catalyzed Three‐Component Reaction of Terminal Alkynes, Diazoesters and Aldehydes

AbstractA highly efficient heterogeneous copper(I)‐catalyzed three‐component coupling of terminal alkynes, diazoesters and aldehydes has been achieved by using 10 mol% of copper(I) iodide complex [N,N‐CuI‐MCM‐41] anchored on 2‐aminoethylamino‐modified mesoporous material MCM‐41 as the catalyst under mild conditions, delivering a wide variety of 2‐alkoxycarbonyl‐substituted (E)‐1,3‐enynes in mostly good to high yields with excellent stereoselectivity. The heterogenized copper(I) complex can be facilely prepared from inexpensive reagents by using a simple procedure and exhibits a remarkably higher catalytic activity than CuI, and can be recycled more than ten times without a significant drop in its catalytic efficiency. This protocol represents the first example of heterogeneous copper‐catalyzed stereoselective construction of functionalized 1,3‐enynes from simple and commercially available starting materials.

A Copper‐Catalyzed [5+1] Cycloaddition of Terminal Alkynes with Diazo Esters through a Tandem 1,5‐H‐Shift Cyclization

Comprehensive SummaryA copper‐catalyzed [5+1] cycloaddition reaction of terminal alkynes with diazo esters for the rapid construction of protected naphthalen‐1(2H)‐one derivatives in moderate to good yields has been disclosed along with good functional group compatibility and a broad substrate scope. The mechanistic investigations reveal that this tandem cyclization process proceeds through a Cu(I)‐catalyzed coupling of terminal alkyne with diazoacetate, a 1,5‐H shift process and a thermally induced pericyclic reaction via an allene intermediate. The synthetic utility and the further transformations of the obtained cycloadduct to naphthalenone, naphthol and dihydronaphthol have been also presented in this paper.

Convenient and efficient reaction system for the oxidative coupling of terminal alkynes over Cu+-containing layered double hydroxides

An efficient and convenient catalytic procedure has been developed for the aerobic oxidative coupling of terminal alkynes to produce 1,3-conjugated diynes over CuCoFe-LDH (Layered double hydroxide) in the absence of base additive. The heterogeneous catalytic system could tolerate various arylacetylenes in good to excellent yields. The results indicated that Cu+ species in CuCoFe-LDH should play the predominant role in the transformation, and dual functions of the catalyst were observed. The CuCoFe-LDH also showed good structural and catalytical stability during the reactions.

Differential Dihydrofunctionalization: A Dual Catalytic Three‐Component Coupling of Alkynes, Alkenyl Bromides, and Pinacolborane

AbstractA new method for differential dihydrofunctionalization of terminal alkynes enables the synthesis of allylic boronate esters through reductive three‐component coupling of terminal alkynes, alkenyl bromides, and pinacolborane. The transformation is promoted by cooperative action of a copper/palladium catalyst system and results in hydrofunctionalization of both π‐bonds of an alkyne. The synthesis of allylic boronate esters can be accomplished in the presence of a wide range of functional groups, including, esters, nitriles, alkyl halides, sulfonyl esters, acetals, protected terminal alkynes, aryl halides, and silyl ethers. Mechanistic experiments reveal the importance of subtle ligand effects on the performance of the palladium co‐catalyst.

Differential Dihydrofunctionalization: A Dual Catalytic Three-Component Coupling of Alkynes, Alkenyl Bromides, and Pinacolborane.

A new method for differential dihydrofunctionalization of terminal alkynes enables the synthesis of allylic boronate esters through reductive three-component coupling of terminal alkynes, alkenyl bromides, and pinacolborane. The transformation is promoted by cooperative action of a copper/palladium catalyst system and results in hydrofunctionalization of both π-bonds of an alkyne. The synthesis of allylic boronate esters can be accomplished in the presence of a wide range of functional groups, including, esters, nitriles, alkyl halides, sulfonyl esters, acetals, protected terminal alkynes, aryl halides, and silyl ethers. Mechanistic experiments reveal the importance of subtle ligand effects on the performance of the palladium co-catalyst.

Copper‐Containing Mineral Mediated Glaser Coupling of Terminal Alkynes

AbstractCopper is one of the most abundant metals on the Earth. Elemental copper, as well as its alloys and compounds are widely used as catalysts in organic chemistry. By utilizing naturally occurring ores, the non‐eco‐friendly copper smelting process can be bypassed, leading to green and environmentally friendly procedures in comparison to the use of synthetic copper compounds. In this study we wish to present a more economical method for the production of symmetric diynes starting from various terminal acetylenes in a Glaser–Hay reaction. Out of the seven tested naturally occurring copper‐containing minerals, chalcocite (Cu2S) and bornite (Cu5FeS4) were the best applicable ones. These minerals were able to produce diynes in yields comparable to those obtained with their synthetic analogues, furthermore they proved to be partly reusable.

Azolium Aurates as Pre-Catalysts for the Oxidative Coupling of Terminal Alkynes under Mild Conditions.

A simple and efficient method for the oxidative coupling of terminal alkynes is reported for the first time, making use of imidazol(in)ium aurates as pre-catalysts. This approach displays high functional group tolerance and leads to a broad range of 1,3-diyne compounds in moderate to excellent yields using low catalyst loading and is performed in air under mild and sustainable conditions.