Homocoupling Of Alkynes Research Articles

Gelation of Metalloporphyrin-Based Conjugated Microporous Polymers by Oxidative Homocoupling of Terminal Alkynes

A Pd(II)/Cu(I) cocatalyzed homocoupling reaction of terminal alkynes to diynes was used to synthesize conjugated polymer organogels with tetragonal topological frameworks consisting of Zn-porphyrin units as nodes and diynes as struts. This material appears fibrous with a micrometer length, possesses outstanding elastic properties, and could be organized into desired modules. Upon drying, the transformed xerogels afford superior thermal stability and microporosity, implying that they are supported by conjugated microporous polymer (CMP) skeletons at the molecular level. The microporosity of CMP-structured xerogels could be adjusted by varying the monomer concentrations, reaction temperatures and solvent species. The notable narrowed pore size distribution is achieved under optimal conditions, which results in CMP-supported xerogels outperforming the most reported CMPs, although the networks are still amorphous in nature. By following the same synthesis route, for the first time, the interpenetrating polymer network organogels were prepared by forming two CMP components sequentially in a temperature-controlled manner and in one pot. This provides an unprecedented combination of multiple interwoven CMP modules whose functions could be assembled synergistically for prospective broader applications.

ChemInform Abstract: Development of Highly Active Heterogeneous Oxidation Catalysts Based on the Properties of Metal Hydroxides

AbstractReview: 62 refs.

On the homogeneity/heterogeneity of solid copper oxide precatalysts in the oxidative homocoupling of ethynylbenzene

The heterogeneity of copper oxide supported on γ-Al2O3 (10CuO-Al2O3) and TiO2 (10CuO-TiO2) precatalysts is assessed in the oxidative homocoupling of ethynylbenzene in piperidine, with a focus on the effect of temperature, support, and solvent on copper leaching and catalyst reactivity. It is demonstrated that for this alkyne homocoupling reaction, elevated temperature is needed to solubilize copper and activate it, likely by production of soluble molecular copper-piperidine complexes. Once this activation occurred, the reaction can occur at room temperature, giving good yields of the desired product. Copper oxide is shown to interact differently on the two supports; CuO supported on TiO2 is more dispersed and accessible than CuO supported on γ-Al2O3. Less copper leaches from 10CuO-TiO2 than from 10CuO-Al2O3 at room temperature. Nevertheless, copper species that leach from 10CuO-TiO2 are more active than the species leached from 10CuO-Al2O3, as some of the copper leached from alumina likely exists as fine, inactive CuO nanoparticles. Piperidine has multiple roles in this reaction: it acts as solvent, base, as well as an important ligand. The precatalyst 10CuO-TiO2 is reused three times, with improved performance after each cycle. Nevertheless, it cannot be considered a recyclable catalyst, but rather a reusable solid precatalyst that produced new soluble active copper species in each cycle.

ChemInform Abstract: Cu(II) Complex Heterogenized on SBA‐15: A Highly Efficient and Additive‐Free Solid Catalyst for the Homocoupling of Alkynes.

A Cu(II) complex has been heterogenized on SBA-15 by functionalization of SBA-15 with (N1-propylethane-1,2-diamine) triethoxysilane (NN-SBA-15) followed by anchoring of 2-pyridinecarboxaldehyde through Schiff's base formation between the terminal –NH2 and the aldehyde group of 2-pyridinecarboxaldehyde (Py-NN-SBA-15), and finally, copper(II) was immobilized through complexation. Copper(II) complex heterogenized on SBA-15 (Cu(II)-SBA-15) has been thoroughly characterized by different techniques such as N2 sorption, small-angle X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and solid-state 13C CP-MAS NMR spectroscopy. Cu(II)-SBA-15 is an efficient heterogenized solid catalyst for the oxidative homocoupling of phenyl acetylene into 1,4-diphenylbuta-1,3-diyne with a yield of 97%, even in the absence of palladium, co-catalyst and base additives. In the case of the homocoupling of other aromatic and aliphatic terminal alkynes, the yields were 85–98%.

Development of Highly Active Heterogeneous Oxidation Catalysts Based on the Properties of Metal Hydroxides

This manuscript summarizes our recent research results on heterogeneously catalyzed aerobic oxidation reactions using supported metal hydroxide catalysts. Metal hydroxide species possess both Lewis acid and Bronsted base sites on the same metal sites, and various kinds of substrates including alcohols, primary amines, nitriles, and terminal alkynes can be activated by the concerted action of the Lewis acid and Bronsted base pair sites. In the presence of a supported ruthenium hydroxide catalyst (Ru(OH) x /Al2O3), oxidative dehydrogenation of alcohols and primary amines efficiently proceeds to afford the corresponding carbonyl compounds (aldehydes and ketones) and nitriles, respectively. In the presence of ammonia (THF solution), Ru(OH) x /Al2O3 can catalyze ammoxidation of primary alcohols to the corresponding nitriles. This ammoxidation proceeds through the sequential reactions of oxidative dehydrogenation of primary alcohols to aldehydes, dehydrative condensation of the aldehydes with ammonia to aldimines, and oxidative dehydrogenation of the aldimines. In addition, formal α-oxygenation of primary amines to the corresponding primary amides can be realized through the Ru(OH) x /Al2O3-catalyzed oxidative dehydrogenation and nitrile hydration. Moreover, a supported copper hydroxide species on a manganese oxide-based octahedral molecular sieve (Cu(OH) x /OMS-2) can act as an efficient and highly durable heterogeneous catalyst for oxidative homocoupling of terminal alkynes to the corresponding diynes. The catalyses for the above-mentioned oxidation reactions are truly heterogeneous, and the catalysts can be reused several times with keeping their high catalytic performance.

ChemInform Abstract: Palladium(II)—Copper(I) Mediated Homotrimerization and Homotetramerization of Terminal Alkynes.

Abstract Alkyne homocoupling is commonly observed in cross coupling reactions; however, self trimerization and homotetramerization of alkynes to form branched products through cross-coupling reactions are rarely reported. We describe herein homotrimerization and homotetramerization of terminal alkynes under the Sonogashira reaction conditions that gave the corresponding modified enediynes. Substrate scope for this reaction was explored.

Synthesis of Fréchet-type Dendrimer Using Glaser-type Coupling Reaction of the Terminal Alkyne-focal Dendrons

Graphical General, fast, and efficient fusion methods for the synthesis of dendrimers with 1,4-diphenylbuta-1,3-diyne at a core were developed. The synthetic strategy was employed the fusion method of the terminal alkyne via CuI/NBS/DIPEA-mediated Glaser-type coupling reaction. Glaser-type coupling reaction under CuI/NBS/DIPEA promoting system could be completed under ambient temperature without exclusion of air and moisture. The fusion of the terminal alkyne-focal Fréchet-type dendrons 3-Dm by homo-coupling of terminal alkyne lead to the formation of symmetric Fréchet-type dendrimers 4-Gm with 1,4-diphenylbuta-1,3-diyne at core. Their structure of dendrimers was confirmed by 1H- and 13C-NMR spectroscopy, IR spectroscopy, mass spectrometry, and GPC analysis.

1,4,7-Trimethyl-1,4,7-Triazacyclononane as a Low-Loading Catalyst: CuBr–tmtacn Catalysed Glaser reaction of Acetylenes

1,4,7-Trimethyl-1,4,7-triazacyclononane (tmtacn, a cyclic trident-ligand) has been developed as a facile and efficient catalyst for Cu-catalysed homocoupling of terminal alkynes at room temperature. A variety of 1,3-diynes have been synthesised in excellent yields with a catalyst loading on a scale of 0.1–0.5 mol% CuBr–tmtacn.

Copper(I)-catalyzed homocoupling reaction of terminal alkynes in supercritical CO2

An efficient method for CuCl-catalyzed homocoupling reaction of terminal alkynes in the synthesis of symmetric 1,3-diynes has been developed in supercritical CO2 (ScCO2) without organic solvent. Homocoupling of various terminal alkynes (solid or liquid) could afford the corresponding products in moderate to excellent yields. In addition, ScCO2 play the role of reactive solvent, and DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) acts as the key additive for homocoupling reactions of terminal alkynes, which enhanced the reaction rate and the solubility of copper(I) catalyst in ScCO2.

Partially oxidized gold nanoparticles: A catalytic base-free system for the aerobic homocoupling of alkynes

The mechanism of alkyne homocoupling over gold nanoparticles and clusters, isolated and supported on CeO2, has been theoretically investigated by means of periodic DFT calculations. The theoretical study indicates that O2 dissociation on gold generates basic O atoms able to abstract the proton of the alkyne, and cationic Auδ+ and Au+ species that decrease the activation barrier for the CC bond forming step. Kinetic results show that the base-free homocoupling of alkynes is effectively catalyzed by gold nanoparticles supported on different solids, and confirm the theoretical prediction that the dissociation of oxygen on the gold nanoparticle is the controlling step of the global reaction.

Total Synthesis of Quebrachamine through Macrolactamization

AbstractThe total synthesis of quebrachamine was achieved through the macrolactamization of cis‐2‐alkenylated indole 17, which was prepared by a Sonogashira reaction between indole 5b and piperidine 11 followed by cis‐hydrogenation. We found that stoichiometric copper(I) iodide limited the undesired Glaser‐type homocoupling of alkyne 11 that would otherwise take place during the Sonogashira coupling. This direct approach allowed the total synthesis in ten linear steps starting from commercially available chemicals. Conditions for the reduction of lactam 19 by lithium aluminiumhydride were adjustable, so that either (±)‐quebrachamine or the analogue (±)‐kopsiyunnanine D was prepared.

ChemInform Abstract: A Facile Copper(I)‐Catalyzed Homocoupling of Terminal Alkynes to 1,3‐Diynes with Diaziridinone under Mild Conditions

Abstract15 examples

Palladium(II)–copper(I) mediated homotrimerization and homotetramerization of terminal alkynes

Alkyne homocoupling is commonly observed in cross coupling reactions; however, self trimerization and homotetramerization of alkynes to form branched products through cross-coupling reactions are rarely reported. We describe herein homotrimerization and homotetramerization of terminal alkynes under the Sonogashira reaction conditions that gave the corresponding modified enediynes. Substrate scope for this reaction was explored.

Copper(i)-catalyzed homo-coupling of terminal alkynes at room temperature under solvent and base free conditions using O2as an oxidant

The homo-coupling of various terminal alkynes were realized in the presence of 0.5 mol% CuI and 5 mol% benzylamine. This transformation proceeded at room temperature under solvent and base free conditions using O2 as an oxidant. The TON was up to 1760.

Cu(ii) complex heterogenized on SBA-15: a highly efficient and additive-free solid catalyst for the homocoupling of alkynes

A Cu(II) complex has been heterogenized on SBA-15 by functionalization of SBA-15 with (N1-propylethane-1,2-diamine) triethoxysilane (NN-SBA-15) followed by anchoring of 2-pyridinecarboxaldehyde through Schiff's base formation between the terminal –NH2 and the aldehyde group of 2-pyridinecarboxaldehyde (Py-NN-SBA-15), and finally, copper(II) was immobilized through complexation. Copper(II) complex heterogenized on SBA-15 (Cu(II)-SBA-15) has been thoroughly characterized by different techniques such as N2 sorption, small-angle X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and solid-state 13C CP-MAS NMR spectroscopy. Cu(II)-SBA-15 is an efficient heterogenized solid catalyst for the oxidative homocoupling of phenyl acetylene into 1,4-diphenylbuta-1,3-diyne with a yield of 97%, even in the absence of palladium, co-catalyst and base additives. In the case of the homocoupling of other aromatic and aliphatic terminal alkynes, the yields were 85–98%.

A porphyrin-linked conjugated microporous polymer with selective carbon dioxide adsorption and heterogeneous organocatalytic performances

A new porphyrin-based conjugated microporous polymer with rich nitrogen sites in the skeleton has been synthesized by alkyne–alkyne homocoupling reaction. The Brunauer–Emmett–Teller specific surface area up to 662 m2 g−1 was obtained for the new polymer framework with a pore volume of 0.55 cm3 g−1. The polymer network displays high carbon dioxide uptake capacity (up to 3.58 mmol g−1) at 273 K and 1 bar, with good selectivity towards CO2 over N2 and CH4. Furthermore, this framework also acts as a solid organocatalyst towards Knoevenagel reaction of malononitrile with aromatic, heterocyclic aldehydes, and cyclic ketones. The reaction afforded the corresponding products in excellent yields (up to 99%) with short times. Moreover, the heterogeneous catalyst was also found to exhibit an excellent recyclability (up to 10 times) without loss of efficiency.

Computational insights into carbon–carbon homocoupling reactions mediated by organolanthanide(iii) complexes

Homocoupling of terminal alkynes into trienediyl complexes by alkyl samarocenes is known experimentally. By means of computational techniques, we investigated the mechanism of this reaction in detail. The overall reaction sequence is: σ-bond metathesis, dimerisation of metallocenes, and homocoupling of two acetylides into trienediyl. We show that the rate-determining step corresponds to the homocoupling of two anionic acetylides. This coupling takes place at a bis-samarocene dimer complex in which the bridging mode of the two acetylide moieties is critical for the reaction to proceed. The limited energy barrier for the homocoupling of the carbanions originates from a synergistic effect of the two samarium centres within the dimer. Variation of the steric demand of both substrates and lanthanocenes allowed rationalising all the experimental data available for these systems.

Oxidative homocoupling of terminal alkynes under palladium-, ligand- and base-free conditions using Cu(II)-clay as a heterogeneous catalyst

Homocoupling of terminal alkynes to 1,3-diynes has been investigated with Cu(II)-modified clay under mild and operationally simple conditions without the use of any ligand or a stabilizing agent. The catalyst is robust, ecofriendly, efficient, furnishes good to excellent yields of the desired products and can be reused several times with negligible loss in catalytic activity.

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

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

ChemInform Abstract: 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.