Homocoupling Of Alkynes Research Articles

Ultrafine copper oxide nanoparticles immobilized on poly (4-vinylpyridine)-grafted UiO-66-NH2 as heterogeneous catalyst for oxidative homocoupling of terminal alkynes

Terminal alkyne homocoupling is an effective route to synthesize 1,3-diynes, which are crucial components of many fine chemicals and natural products. However, the reaction often faces challenges of catalyst recovery and typically necessitates the introduction of basic additives, which limits its practical applicability. Here, we have developed a green and efficient Cu2O@UiO-66-g-P4VP nanocatalyst that exhibits outstanding activity for homocoupling terminal alkynes under mild, base- or ligand-free conditions. The characterization results indicate that the nitrogen atoms in P4VP interfere with the electronic structure of Cu in Cu2O nanoparticles, causing the N electrons to shift onto Cu. Density functional theory (DFT) calculations suggest that this catalytic system facilitates the activation of oxygen on the copper surface, promoting the coupling reaction. This work provides a feasible strategy for the rational fabrication of MOF-supported polybase and Cu2O nanocrystals as heterogeneous nanocatalysts in the oxidative homocoupling of alkynes.

Engineering Cu2O/Cu/N-C interface to induce directional migration of charge for driving photocatalytic homo-coupling of terminal alkynes

Engineering Cu2O/Cu/N-C interface to induce directional migration of charge for driving photocatalytic homo-coupling of terminal alkynes

Synergistic catalysis by Brønsted acid and Pd species on a mesoporous ZSM-5 zeolite for the oxidative homocoupling of terminal alkynes

The Brønsted acid and Pd species on Pd@MZSM-5 synergetically catalyzed the oxidative homocoupling of terminal alkynes, where the Brønsted acid promote the alkyne chemisorption and benefit the formation of the alkynyl-palladium(ii) complex.

Rhodium-catalysed homo-coupling of terminal alkynes: divergent synthesis of bioactive 1,3-diynes and conjugated enediynes

C(sp)–C(sp) cross-coupling of terminal alkynes represents a robust tool for building biologically active 1,3-diynes although confronted with huge challenges regarding selectivity control.

Synthetic Access to 1,3-Butadiynes via Electro-redox Cuprous-Catalyzed Dehydrogenative Csp–Csp Homocoupling of Terminal Acetylenes

AbstractHerein, we disclose the oxidative homocoupling of terminal alkynes under electrochemically generated cuprous catalysis. The scope of this protocol was established by preparing an array of structurally and electronically different 1,3-butadiyne derivatives. Good synthetic yields, functional group tolerance, oxidant-free conditions, and no cross-selectivity are some of the intrinsic advantages of this methodology. The developed chemistry features the electro-redox formation of copper acetylide, an intermediate appropriate for the Csp–Csp coupling step. The chemical state of copper in the acetylide intermediate was found to be Cu(I), as confirmed by click trapping experiments, cyclic voltammetry, EPR spectroscopy, and XPS. A competition reaction to determine the reactivity of electronically dissimilar acetylenes revealed that the product ratio is rather dependent on the electronic nature of the alkynyl substituents. To highlight the synthetic value of the products, selected diynes were subjected to chemical diversification.

Air Tolerant Cadiot-Chodkiewicz and Sonogashira Cross-Couplings.

Cadiot-Chodkiewicz cross-couplings generate an unsymmetric buta-1,3-diyne by way of a Cu(I)-catalyzed coupling between a terminal alkyne and a 1-haloalkyne. Despite their widespread use, Cadiot-Chodkiewicz reactions are plagued by the generation of symmetric buta-1,3-diyne side products, formed through competing: (a) formal reductive homo-coupling of the 1-haloalkyne and (b) oxidative (Glaser-Hay/Eglinton) homo-coupling of the terminal alkyne. To overcome this issue, a large excess of one of the two reacting alkynes is commonly deployed, and difficult separations of cross- and homo-coupled products are often encountered. Here, we demonstrate that the use of ascorbate as a reductant leads to a suppression of these unwanted side reactions, hence permitting excellent yields with a roughly stoichiometric ratio of reactants. The procedure also avoids an inert gas atmosphere and uses a sustainable solvent. A similar approach is effective for cross-couplings involving a Pd(0)/Pd(II) catalytic cycle, with air tolerant Sonogashira couplings also established.

Highly Efficient Conversion of Homocoupling and Heterocoupling of Terminal Alkynes Catalyzed by AuCu24/AC‐200

AbstractRegulation of Hybrid Materials of Ministry of Education, Bimetallic nanoclusters with synergistic effect exhibit better stability and activity than monometallic nanoclusters in catalytic applications. However, the large number of ligands on the surface of nanoclusters obscure the active sites, thus reducing the catalytic activity. Here, AuCu24/AC−X (X=0, 200, 300, 500, 800) catalysts were fabricated by removing the partial ligands on the surface of AuCu24H22((p‐FPh)3P)12nanoclusters (short for AuCu24NCs), and investigated the influence of calcination temperature on catalytic performance of AuCu24/AC in homocoupling and heterocoupling of terminal alkynes. The results showed that the catalytic activity of AuCu24/AC−X exhibited a volcanic trend with the increase of X (heat treatment temperature) and the content of Cu2+also changed with the increase of X. Compared with Au25/AC‐200 and Cu25/AC‐200 catalysts, the AuCu24/AC‐200 bimetallic catalyst showed the highest catalytic activity in homocoupling and heterocoupling of terminal alkynes under mild conditions with TOF values reaching 478.7 h−1and 114.1 h−1respectively, which are higher than most reported catalysts. This work provides a research idea for the design of bimetallic nanoclusters with superior performance.

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.

Structural and Synthetic Insights on Oxidative Homocouplings of Alkynes Mediated by Alkali-Metal Manganates.

Exploiting bimetallic cooperation alkali-metal manganate (II) complexes can efficiently promote oxidative homocoupling of terminal alkynes furnishing an array of conjugated 1,3-diynes. The influence of the alkali-metal on these C-C bond forming processes has been studied by preparing and structurally characterizing the alkali-metal tetra(alkyl) manganates [(TMEDA)2 Na2 Mn(CH2 SiMe3 )4 ] and [(PMDETA)2 K2 Mn(CH2 SiMe3 )4 ]. Reactivity studies using phenylacetylene as a model substrate have revealed that for the homocoupling to take place initial metalation of the alkyne is required. In this regard, the lack of basicity of neutral Mn(CH2 SiMe3 )2 precludes the formation of the diyne. Contrastingly, the tetra(alkyl) alkali-metal manganates behave as polybasic reagents, being able to easily deprotonate phenylacetylene yielding [{(THF)4 Na2 Mn(C≡CPh)4 }∞ ] and [(THF)4 Li2 Mn(C≡CPh)4 ]. Controlled exposure of [{(THF)4 Na2 Mn(C≡CPh)4 }∞ ] and [(THF)4 Li2 Mn(C≡CPh)4 ] to dry air confirmed their intermediary in formation of 1,4-diphenyl-1,3-butadiyne in excellent yields. While the Na/Mn(II) partnership proved to be the most efficient in stoichiometric transformations, under catalytic regimes, the combination of MC≡CAr (M= Li, Na) and MnCl2 (6 mol %) only works for lithium, most likely due to the degradation of alkynylsodiums under the aerobic reaction conditions.

Deep Eutectic Solvent‐Mediated Oxidative Homocoupling of Terminal Alkynes to 1,3‐Diynes under Mild Green Conditions

AbstractWe prepared a commercially viable Deep Eutectic Solvent (DES) based on Choline Chloride‐Urea‐copper acetate for the first time. It mediates the homocoupling of terminal alkynes, using air as an oxidant. Water is the only by‐product of the entire process. The method avoids ligands, bases, oxidants, and costly palladium catalysts, which qualifies the process greener than ever. The DES can be reused at least three times without affecting the reaction yield significantly. The key features of the protocol that qualify the process as green include the ambient reaction temperatures, lesser use of conventional organic solvents in the reaction, higher yields, and easy product isolation qualify the protocol as a green process.

Green carbon-carbon homocoupling of terminal alkynes by a silica supported Cu(II)-hydrazone coordination compound.

A Cu(II) complex, [Cu(HL)(NO3)(CH3OH)]·CH3OH (1), was obtained by the reaction of Cu(NO3)2·3H2O and H2L in methanol solvent (H2L is (E)-4-amino-N'-(2-hydroxy-3-methoxybenzylidene)benzohydrazide). H2L and compound 1 were characterized by various spectroscopic analyses and the molecular structure of [Cu(HL)(NO3)(CH3OH)]·CH3OH was determined by single-crystal X-ray analysis. The results indicated the product is a mononuclear Cu(II) complex and contains a free NH2 functional group on the structure of the ligand. [Cu(HL)(NO3)(CH3OH)]·CH3OH was used for the preparation of a heterogeneous catalyst by supporting it on functionalized silica gel. The heterogeneous catalyst (Si-Cu) was prepared by an amidification reaction of [Cu(HL)(NO3)(CH3OH)]·CH3OH with functionalized silica gel. The resulting silica-supported catalyst (Si-Cu) was characterized by TGA, FT-IR, EPR, DRS, EDS, XRD, SEM and XPS analyses. Si-Cu was employed in a carbon-carbon coupling reaction and the effects of the amount of Si-Cu and temperature were investigated in the catalytic coupling. The structure of one of the products of the catalytic reactions (C16H22O2, CP1) was determined by single-crystal X-ray analysis, which proved the formation of a C-C bond and the production of di-acetylene by homocoupling of terminal alkyne. This catalytic system is stable and it can be reused for a coupling reaction without a significant change in its catalytic activity.

A synergistic {Cu2-W12O40} catalyst with high conversion for homo-coupling of terminal alkynes

The 2D {[Cu2(OAc)4]2(W12O40)}n network with unique Cu-POM synergistic cooperation to lead alkyne C–H activation is a super efficient catalyst with high conversion in homo-coupling of terminal alkynes.

Light-Harvesting Novel Hierarchical Porous Cu9S5–MnWO4 Hybrid Structures in Photocatalytic Oxidative Homocoupling of Alkynes and Amines

The discovery of light-harvesting materials for use in photocatalytic organic reactions has recently attracted attention, indicating the potential for utilizing renewable energy sources. A hybrid semiconductor (SC)-SC structure, Cu9S5-MnWO4, was synthesized using a simple, efficient method. The novel hierarchical porous Cu9S5-MnWO4 hybrid structures were then applied in the photocatalysis of oxidative homocoupling of alkynes and amines. The design of a heterogeneous catalyst based on a porous, SC-SC hybrid structure and low-cost Cu should generate interest in the fabrication and modification of photocatalysts for a wide range of applications.

Facile Synthesis of the Shape‐Persistent 4‐Hydroxybenzaldehyde Based Macrocycles and Exploration of their Key Electronic Properties: An Experimental and DFT Approach

AbstractIn the current study, a series of stabilized bis‐acetylene incorporated 4‐hydroxybenzaldehyde based macrocycles using the alkyne‐homocoupling approach were synthesized in moderate yields. A total of six newly stiff macrocycles were synthesized in a stepwise manner starting from 4‐hydroxybenzaldehyde. In the first step, base mediated propargylation was performed followed by copper mediated terminal alkyne homocoupling. The alkyne homocoupled substrate having carbonyl at both the terminals is cyclized in the final step via double imine formation reactions using substituted diamines as linker. All the newly synthesized rigid framework of the macrocycles were optimized at B3LYP/6‐31G (d,p) level of theory. Nonlinear optical behaviors of the synthesized macrocycles were explored by the DFT calculations where high values of first‐order hyperpolarizability and dipole moment were examined. In the reported study, a good agreement between experimental and theoretical parameters was observed that may play a significant contribution for the NLO applications.

Cobalt-Catalyzed Glaser-type Homocoupling Reaction

AbstractA highly efficient cobalt-catalyzed homocoupling of terminal alkynes with di-tert-butyldiaziridinone as the oxidant has been developed. The protocol tolerates a wide array of terminal alkynes, both activated and unactivated alkynes, to afford the corresponding conjugated 1,3-diynes. The mild reaction conditions further allow late-stage homocoupling of alkynes derived from complex natural products.

Homocoupling of terminal alkynes catalyzed by CuCl under solvent-free conditions

A series of symmetrical 1,4-disubstituted buta-1,3-diynes is prepared with excellent yields (up to 95%) through homocoupling of terminal alkynes catalyzed by a copper salt under solvent-free conditions. This method provides an environmentally friendly process to prepare 1,3-diynes in short reaction times under mild conditions. Furthermore, the method is suitable for a wide substrate scope and has excellent functional group compatibility. The reaction can also be scaled up to gram level.

Synthesis of Chromophore Core Fréchet-Type Dendrimer by Oxidative Homo-Coupling of Terminal Alkyne

Synthesis of Chromophore Core Fréchet-Type Dendrimer by Oxidative Homo-Coupling of Terminal Alkyne

Cu Catalyst Supported on Nitrogen and Phosphorus Co-Doped Carbon Nanosheets for Homocoupling of Terminal Alkynes Using CO2 as a Soft Oxidant

A bifunctional role of carbon dioxide (CO2) was developed in this research as a medium for catalyst preparation and as a soft oxidant for the subsequent coupling reaction. A highly dispersed and lo...

Electro-Oxidative Coupling Reactions Leading to π-Conjugated Compounds.

Electrochemical reactions are rapidly gaining attention today as a powerful and environmentally benign reaction processes for organic synthesis. We found that the electro-oxidation of palladium acetate afforded cationic palladium species and thus-generated cationic Pd species were efficient mediators for electro-oxidative coupling reactions. Homo-coupling of arylboronic acids and terminal alkynes proceeded efficiently to afford biaryls and butadiyne, respectively. Cross-coupling reactions between terminal alkynes and arylboronic acids were also achieved with the use of a Ag anode. As an advantage of electrochemical reactions, we developed a sequential reaction system switched between oxidative and neutral conditions by the on/off application of electricity, and several π-extended butadiynes were obtained in one-sequence by the system. Electrochemical intramolecular C-S coupling for the synthesis of thienoacene was also developed. The use of Bu4 NBr as a halogen mediator was essential for the reaction.

Supporting a Cu@In2O3 core–shell structure on N-doped graphitic carbon cuboctahedral cages for efficient photocatalytic homo-coupling of terminal alkynes

N-doped carbon cuboctahedral cage-supported core–shell Cu@In2O3 nanocomposites exhibit highly enhanced photocatalytic performances towards the home-coupling of terminal alkynes.