Homocoupling Of Alkynes Research Articles

Effect of Metal Surfaces in On-Surface Glaser Coupling

The homocoupling of alkynes at metal surfaces, which was disclosed recently, is a promising reaction for efficient construction of conjugated nanostructures at metal surfaces. However, the role of the metal substrate as well as the mechanistic course of this process have not been investigated. The metal surface could act cooperatively (a) for two-dimensional confinement to properly orient the organic reactant and (b) also as an active mediator in the C–C bond-forming reaction. Herein we report covalent coupling of the dimers of 1,4-diethynylbenzene at various metal surfaces. The model reaction was investigated experimentally by STM and also by theoretical DFT calculations. Detailed statistical analysis and the theoretical results strongly support the involvement of the metal surface in the C–C bond-forming process. On the basis of these investigations, a model with two possible reaction pathways is suggested to describe the process: C–C coupling via direct CH activation and C–C coupling via alkynyl activation by π-complex formation.

ChemInform Abstract: Copper‐Impregnated Magnetite as a Heterogeneous Catalyst for the Homocoupling of Terminal Alkynes.

AbstractThe process requires the lowest loading reported for a heterogeneous copper catalyst to date.

Recyclable Porous Polymer‐Supported Copper Catalysts for Glaser and Huisgen 1,3‐Diolar Cycloaddition Reactions

A family of polymer-attached phenanthrolines was prepared from solvothermal copolymerization of divinylbenzene with N-(1,10-phenanthroline-5-yl)acrylamide in different ratios. The polymer-supported copper catalysts were obtained through typical impregnation with copper(II) salts. The polymers and supported copper catalysts have been characterized by N2 adsortion, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TG); they exhibit a high surface area, hierarchical porosity, large pore volume, and high thermal and chemical stabilities. The copper catalyst has proved to be highly active for Glaser homocoupling of alkynes and Huisgen 1,3-diolar cycloaddition of alkynes with benzyl azide under mild conditions at low catalyst loading. The heterogeneous copper catalyst is more active than commonly used homogeneous and nonporous polystyrene-supported copper catalysts. In particular, the catalyst is easily recovered and can be recycled at least ten times without any obvious loss in catalytic activity. Metal leaching was prevented due to the strong binding ability of phenanthroline and products were not contaminated with copper, as determined by ICP analysis.

Immobilized Cu complex on modified Fe3O4 nanoparticles as a magnetically separable catalyst for the oxidative homocoupling of terminal alkynes

Fe3O4 nanoparticles were prepared by the co-precipitation method, and silica was then coated on the magnetic nanoparticles followed by modification with (3-aminopropyl)trimethoxysilane (APTMS) and complexation with CuI, Cu(bpy)2I and Cu(en)2I and designated as Fe3O4@SiO2@APTMS@Cu Complex. The prepared catalysts were characterized by FTIR, XRD, SEM, and VSCM techniques. It was found that Fe3O4@APTMS@Cu(en)2 successfully mediates the oxidative homocoupling of phenylacetylene, 4-tert-butylphenylacetylene, 1-ethynyl-4-fluorobenzene and pent-1-yn-3-ol with 67–100 % conversion and 95–100 % selectivity. The prepared Fe3O4@APTMS@Cu(en)2 nanoparticles were magnetically recovered and recycled without significant decrease in activity.

Cu (I) immobilized on functionalized SBA-15: A recyclable catalyst for the synthesis of 1,3-diynes using terminal alkynes without base

Abstract A new functionalized SBA-15 catalyst immobilized CuI was successfully prepared, and the catalytic activity was tested in the oxidative homocoupling of terminal alkynes at the absence of base, and good to excellent yields was obtained to get 1,3-diynes without any side product formation in the solution of DMSO. Moreover, the system also allowed the synthesis of unsymmetric 1,3-diynes by cross-coupling of two different terminal alkynes. Finally, the catalyst could be reused for several times without a significant loss of activity.

Copper-Impregnated Magnetite as a Heterogeneous Catalyst for the Homocoupling of Terminal Alkynes

Copper-impregnated magnetite is a versatile heterogeneous catalytic system for the synthesis of 1,3-diynes by the homocoupling of terminal alkynes. This catalyst does not require the use of pressurized oxygen as the oxidant and it does not need a solvent or harsh conditions to give the expected products. Moreover, the catalyst can be removed from the reaction medium simply by using a magnet. The reaction occurs at the lowest copper loading reported for any heterogeneous catalyst.

Cover Picture: Glaser Coupling at Metal Surfaces (Angew. Chem. Int. Ed. 14/2013)

On-surface synthesis enables the construction of defined nanostructures directly at surfaces through the covalent coupling of suitable organic precursors. These processes are carried out under ultrahigh-vacuum conditions and are monitored by scanning tunneling microscopy. In their Communication on page 4024 ff., A. Studer, H. Fuchs, and co-workers present a systematic study of the homocoupling of alkynes (Glaser coupling) as a versatile strategy for the construction of conjugated polymers at various metal surfaces.

Cover Picture: Palladium-Catalyzed Oxidative Cross-Coupling between Heterocycles and Terminal Alkynes with Low Catalyst Loading (Angew. Chem. Int. Ed. 13/2013)

The direct alkynylation of electron-rich aromatic heterocycles with terminal alkynes was accomplished in high yields and good selectivity when using a low loading of palladium catalyst, as described by W. Su and co-workers in their Communication on page 3630 ff. A high loading of palladium catalyst led to poor yields because of the undesired homocoupling of alkynes.

A facile copper(I)-catalyzed homocoupling of terminal alkynes to 1,3-diynes with diaziridinone under mild conditions.

A novel and efficient Cu(I)-catalyzed oxidative homocoupling of terminal alkynes with diaziridinone as an oxidant is described. Various terminal alkynes can be transformed into the corresponding 1,3-diynes in good yields. The reaction process is base-free, operationally simple, and amenable to the gram scale.

Mesoporous silica-supported copper-catalysts for homocoupling reaction of terminal alkynes at room-temperature

Amine-functionalized mesoporous silica-supported copper catalysts SBA-15@amine–Cu and SBA-15@Oamine–Cu were prepared and proved to be efficient and reusable for homocoupling of terminal alkynes at room temperature with air as the oxidant. SBA-15@amine–Cu exhibited better recyclability than SBA-15@Oamine–Cu. The differences in the catalytic performances of the catalysts could be ascribed to catalyst structure and the interaction between copper and the supports. The as-prepared catalysts were systematically characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES), high resolution-transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and nitrogen physical adsorption. The analysis indicated that the mesoporous structure of the materials was retained during the immobilization process. XPS results suggested that the as-prepared catalysts were not obtained by a simple physical adsorption of CuCl on the supports. It is noted that, for aliphatic alkynes, the catalytic activity of SBA-15@amine–Cu is even higher than that of the homogeneous copper catalytic system and that of some previously reported heterogeneous systems.

Ligand‐Free Synthesis of 1,4‐Disubstituted‐1,3‐diynes by Iron/Copper Cocatalyzed Homocoupling of Terminal Alkynes

AbstractA simple and efficient protocol for Fe/Cu cocatalyzed oxidative homocoupling reaction of terminal alkynes to symmetrical 1,4‐disubstituted‐1,3‐diynes was presented. The results showed that both CuBr and FeCl3 played crucial roles in the reaction. It is noteworthy that this protocol employs mild, efficient, aerobic and ligand free conditions. The alkynes, including aromatic, heteroaromatic and aliphatic alkynes, were transformed into the corresponding 1,3‐diynes in good to excellent yields.

Efficient alkyne homocoupling catalysed by copper immobilized on functionalized silica

Copper immobilized on a functionalized silica support is a good catalyst for the homocoupling of terminal alkynes. The so‐called Glaser–Hay coupling reaction can be run in air with catalytic amounts of base. The copper catalyst is active for multiple substituted alkynes, in both polar and non‐polar solvents, with good to excellent yields (75–95%). Depending on the alkyne, full conversion can be achieved within 3–24 h. The catalyst was characterized by TGA, inductively coupled plasma and X‐ray photoelectron spectroscopy. Leaching tests confirm that the catalyst is and remains heterogeneous. Importantly, the overall reaction requires only alkyne and oxygen (in this case, air) as reagents, making this a clean catalytic oxidative coupling reaction. Copyright © 2012 John Wiley & Sons, Ltd.

ChemInform Abstract: Terminal Alkyne Homocoupling Reactions Catalyzed by an Efficient and Recyclable Polymer‐Supported Copper Catalyst at Room Temperature under Solvent‐Free Conditions.

AbstractBoth aromatic and aliphatic terminal alkynes undergo the homocoupling reaction within only 10‐20 minutes to give the corresponding 1,4‐disubstituted 1,3‐diynes in excellent to high yields.

Importance of bases on the copper-catalyzed oxidative homocoupling of terminal alkynes to 1,4-disubstituted 1,3-diynes

Copper-catalyzed, solvent-free oxidative homocoupling of terminal alkynes can be performed to 1,3-diynes in good to excellent yields in the absence of any additives, using air as environmentally friendly oxidant and the occurrence of water as an exclusive byproduct in the whole process. It is shown that AcO− of copper (II) acetate catalyst may take the role of base and found that the homocoupling cannot occur using weakly basic copper salt catalysts such as CuBr, CuCl, or CuI. Thus, the bases are absolutely necessary in the process of the homocoupling of terminal alkynes.

ChemInform Abstract: Heterogeneous Catalytic Homocoupling of Terminal Alkynes

AbstractReview: 64 refs.

Heterogeneous Catalytic Homocoupling of Terminal Alkynes

The homocoupling of terminal alkynes under heterogeneous catalysis is tackled in this perspective. The performance of different unsupported and supported catalysts, primarily based on palladium and copper, is analyzed from a critical point of view. This type of coupling provides the most direct access to 1,3-diynes, which can be found in nature and are very important compounds in organic synthesis.

Naked and Self‐Clickable Propargylic‐Decorated Single‐Chain Nanoparticle Precursors via Redox‐Initiated RAFT Polymerization

Protection of acetylenic monomers is a common practice to avoid parasitic side reactions during polymerization. Herein, we report that redox-initiated RAFT polymerization allows the direct, room temperature synthesis of a variety of single-chain nanoparticle precursors (displaying narrow molecular weight dispersity, M[overline](W)/M[overline](n) = 1.12 -1.37 up to M[overline](W) = 100 kDa) containing well-defined amounts of naked, unprotected acetylenic functional groups available for rapid and quantitative intrachain cross-linking via metal-catalyzed carbon-carbon coupling (i.e., C-C "click" chemistry). To illustrate the useful "self-clickable" character of the new unprotected acetylenic precursors, single-chain nanoparticles have been prepared for the first time in a facile and highly efficient manner by copper-catalyzed alkyne homocoupling (i.e., Glaser-Hay coupling) at room temperature under normal air atmosphere.

Electrochemical monitoring of the oxidative coupling of alkynes catalyzed by triphenylphosphine gold complexes

Electrochemical monitoring of the oxidative coupling of alkynes in the homogeneous phase through catalytic cycles involving triphenylphosphine gold complexes and selectfluor as oxidant reveals that at least two gold species in +3 and +1 oxidation states are implicated. Electrochemically driven homocoupling of terminal alkynes using molecular oxygen as the oxidant can be performed using such catalysts.

Oxidative Homocoupling of Alkynes Using Supported Ionic Liquid Phase (SILP) Catalysts - Systematic Investigation of the Support Influence

Supported Ionic Liquid Phase (SILP) catalysts have been prepared by effective immobilization of [Cu(TMEDA)(OH)]Cl in a nano-metric film of an ionic liquid on various oxidic support materials. The catalysts were tested for the oxidative homocoupling of 1-alkynes to the corresponding diynes in in a combined high throughput and conventional batch reaction approach. Among the screened support materials silica based materials performed best. The results indicate that for the specific reaction the thickness of the ionic liquids layer and therefore the mobility of the homogeneous copper complex within the ionic liquid layer as deduced from solid state nmr measurements have major impact on the catalytic performance. The optimized catalysts could be recycled up to four times without any loss of activity.

Dinickel(ii) complexes: Preparation and catalytic activity

Ligands (L(a-c)) based on 2,7-bis(3,5-di-R-pyrazol-1-yl)-1,8-naphthyridine (a, R = H; b, R = CH(3); c, R = Ph) were prepared for the construction of a series of dinickel complexes. Treatment of L(x) with NiCl(2) in an anhydrous methanol/THF solution resulted in the formation of dinuclear complexes [(L(x))(μ-Cl)(2)Ni(2)Cl(2)(CH(3)OH)(2)] (3, x = a; 4, x = b; 5, x = c). These new complexes were characterized by elemental analysis, IR and UV-Vis spectroscopic techniques. The structures of complexes 3 and 4 were further confirmed by X-ray diffraction studies. Interestingly, crystals of 4 were obtained as a co-crystallization of 4 and the methanol substituted species [{(L(b))(μ-Cl)(2)Ni(2)Cl(CH(3)OH)(3)}Cl] (4'). These dinickel complexes have been tested in the catalytic homo-coupling of terminal alkynes with the use O(2) as the oxidant, showing excellent activities. A clear improvement on the catalytic activity of these complexes is observed as compared to the mono-nuclear species.