Practical Oxidative Homo- and Heterocoupling of Terminal Alkynes Catalyzed by Immobilized Copper in MCM-41

Recyclable Copper(I)-Catalyzed Cross-Coupling of Trialkylsilylethynes and N-Tosylhydrazones Leading to the Formation of C(sp)-C(sp3) Bonds

A highly efficient heterogeneous copper(I)-catalyzed cross-coupling of trialkylsilylethynes with N-tosylhydrazones has been achieved in dioxane at 90-110 °C via the Cu carbene migratory insertion with an SBA-15-immobilized l-proline-Cu(I) complex [SBA-15-l-Proline-CuI] as the catalyst and LiO^tBu as the base, leading to the formation of C(sp)-C(sp³) bonds. The reaction generates a wide variety of alkyltrialkylsilylalkynes in moderate to high yields. This new heterogenized copper(I) complex exhibits a comparable catalytic efficiency to homogeneous CuI and can be easily recovered through a simple centrifugation process and is recyclable up to 12 times without a remarkable loss of activity.

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.

Iron-Catalyzed Cadiot-Chodkiewicz Coupling with High Selectivity in Water under Air

An iron-based catalytic system was developed for the cross-coupling of 1-bromoalkynes with terminal alkynes to selectively generate unsymmetrical 1,3-butadiynes in water under air. It was found that a combination of 1-bromoalkynes derived from less acidic terminal alkynes with more acidic counterparts would greatly enhance yields and selectivity for unsymmetrical 1,3-butadiynes. The reaction was also applicable for the synthesis of unsymmetrical 1,3,5-hexatriynes through coupling of 1-bromoalkynes and trimethylsilyl-protected 1,3-butadiynes in a one-pot manner.

Click synthesis of 1,2,3-triazoles using copper iodide nanoparticles anchored poly(sulfonamide-thiazole) modified layered double hydroxides/chitosan nanocomposite

Click synthesis is a class of biocompatible small molecule reactions commonly used in bioconjugation. This research presents a recyclable environmentally-friendly catalyst for 1,2,3-triazoles. To this end, we immobilized poly sulfonamide-thiazole (PST), a new group of sulfonamides, on the surface of layered double hydroxides/chitosan (LDH@CS). Afterward, it was decorated using copper iodide nanoparticles (CuI NPs). LDH@CS@PST/Cu was characterized various techniques, including HNMR, ¹³CNMR, FE-SEM, FT-IR, XRD, EDX, ICP-OES, and TGA/DTA. Overall, the results revealed that LDH@CS@PST/Cu is a promising green efficient for the domino reaction of phenacyl bromides with phenylacetylene and sodium azide.

Highly selective cross-coupling reactions of 1,1-dibromoethylenes with alkynylaluminums for the synthesis of aryl substituted conjugated enediynes and unsymmetrical 1,3-diynes

A highly efficient method for the synthesis of aryl substituted conjugated enediynes and unsymmetrical 1,3-diynes via selective cross-coupling reactions of 1,1-dibromoethylenes with alkynylaluminums using the Pd(OAc)2-DPPE and Pd2(dba)3-TFP complexes as catalysts, respectively, has been successfully developed. Though the alkyl substituted conjugated enediynes and unsymmetrical 1,3-diynes were not obtained, this case is also remarkable as the same starting materials could selectively produce either aryl substituted conjugated enediynes or unsymmetrical 1,3-diynes in moderate to excellent yields (up to 99%) in the different Pd-phosphine catalytic systems.

In Situ Synthesis of CuN4 /Mesoporous N-Doped Carbon for Selective Oxidative Crosscoupling of Terminal Alkynes under Mild Conditions

The 1,3-conjugated diynes are an important class of chemical intermediates, and the selective crosscoupling of terminal alkynes is an efficient chemical process for manufacturing asymmetrical 1,3-conjugated diynes. However, it often occurs in homogenous conditions and costs a lot for reaction treatment. Herein, a copper catalyzed strategy is used to synthesize highly ordered mesoporous nitrogen-doped carbon material (OMNC), and the copper species is in situ transformed into the copper single-atom site with four nitrogen coordination (CuN₄ ). These features make the CuN₄ /OMNC catalyst efficient for selective oxidative crosscoupling of terminal alkynes, and a wide range of asymmetrical and symmetrical 1,3-diynes (26 examples) under mild conditions (40 °C) and low substrates ratio (1.3). Density functional theory (DFT) calculations reveal that the aryl-alkyl crosscoupling has the lowest energy barrier on the CuN₄ site, which can explain the high selectivity. In addition, the catalyst can be separated and reused by simply centrifugation or filtration. This work can open a facile avenue for constructing single-atom loaded mesoporous materials to bridge homogeneous and heterogeneous catalysis.

Cu/Cu2O Nanoparticles Supported on a Phenol-Pyridyl COF as a Heterogeneous Catalyst for the Synthesis of Unsymmetrical Diynes via Glaser-Hay Coupling

Covalent organic frameworks (COFs) are a new class of porous crystalline polymers with a modular construct that favors functionalization. COF pores can be used to grow nanoparticles (nPs) with dramatic size reduction, stabilize them as dispersions, and provide excellent nP access. Embedding substrate binding sites in COFs can generate host-guest synergy, leading to enhanced catalytic activity. In this report, Cu/Cu₂O nPs (2-3 nm) are grown on a COF, which is built by linking a phenolic trialdehyde and a triamine through Schiff bonds. Their micropores restrict the nP to exceptionally small sizes (∼2-3 nm), and the pore walls decorated with strategically positioned hydrogen-bonding phenolic groups anchor the substrates via hydrogen-bonding, whereas the basic pyridyl sites serve as cationic species to stabilize the [Cu_clusterCl₂]^2- type reactive intermediates. This composite catalyst shows high activity for Glaser-Hay heterocoupling reactions, an essential 1,3-diyne yielding reaction with widespread applicability in organic synthesis and material science. Despite their broad successes in homocoupled products, preparation of unsymmetrical 1,3-diynes is challenging due to poor selectivity. Here, our COF-based Cu catalyst shows elevated selectivity toward heterocoupling product(s) (Cu nP loading 0.0992 mol %; turn over frequency: ∼45-50; turn over number: ∼175-190). The reversible redox activity at the Cu centers has been demonstrated by carrying out X-ray photoelectron spectroscopy on the frozen reactions, whereas the crucial interactions between the substrates and the binding sites in their optimized configurations have been modeled using density functional theory methods. This report emphasizes the utility of COFs in developing a heterogeneous catalyst for a truly challenging organic heterocoupling reaction.

Highly Efficient Heterogeneous Copper-Catalysed O-Arylation of Phenols by Nitroarenes Leading to Diaryl Ethers

The heterogeneous O-arylation of phenols by nitroarenes was achieved in DMF at 100 °C by using an MCM-41-immobilised bidentate nitrogen copper(II) complex [MCM-41-2N-Cu(OAc)2] as catalyst, yielding a variety of unsymmetrical diaryl ethers in good to excellent yields. This heterogeneous copper catalyst can be easily prepared by a simple procedure from commercially readily available and inexpensive reagents, recovered by filtration of the reaction solution and recycled at least seven times without significant loss of activity.

Cu(II)-CMC: a mild, efficient and recyclable catalyst for the oxidative alkyne homocoupling reaction

Cu(II) heterogenized on sodium carboxymethyl cellulose (Na-CMC) has been thoroughly characterized by different techniques. Cu(II)-CMC has been applied for the first time in the homocoupling reaction of a variety of terminal alkynes. The catalyst furnished good to excellent yields of the desired products and could be reused six times without loss of catalytic activity. The Cu(II)-CMC catalysis protocol is a new efficient route to synthesize 1,3-diynes under mild conditions.

MCM-41-Immobilised Nitrogen and Sulfur Mixed Tridentate Palladium(0) Complex: A Highly Efficient and Recyclable Catalyst for the Suzuki Reaction of Aryl Bromides in Air

The novel MCM-41-immobilised nitrogen and sulfur mixed tridentate palladium(0) complex [MCM-41-2N,S-Pd(0)] was prepared from 3-(2-aminoethylamino)propyltrimethoxysilane by immobilisation on MCM-41, followed by reaction with thiophene-2-carboxaldehyde and PdCl2 and then reduction with hydrazine hydrate. This phosphine-free heterogeneous palladium(0) complex was a highly active catalyst for the Suzuki reaction of aryl bromides in air and could be recycled at least 8 times without significant loss of activity.

Highly efficient synthesis of unsymmetrical 1,3-diynes from organoalane reagents and alkynyl bromides mediated by a nickel catalyst

Highly efficient and simple cross-coupling reactions of alkynylbromides with organoalane reagents for the synthesis of unsymmetrical 1,3-diynes derivatives using Ni(OAc)₂ (2–5 mol%)/(o-furyl)₃P (4–10 mol%) as a catalyst are reported.

Functionalized hypercrosslinked polymers with knitted N-heterocyclic carbene–copper complexes as efficient and recyclable catalysts for organic transformations

An N-heterocyclic carbene–copper complex supported on hypercrosslinked polymers was synthesized and characterized by spectroscopic methods, displaying very good catalytic activity in many organic reactions.

A highly efficient heterogeneous copper-catalyzed three-component coupling of tetrahydroisoquinolines, aldehydes and 1-alkynes

A highly efficient heterogeneous copper-catalyzed three-component coupling of tetrahydroisoquinolines, aldehydes and 1-alkynes has been described.

A highly efficient heterogeneous copper-catalyzed Chan–Lam coupling reaction of sulfonyl azides with arylboronic acids leading to N-arylsulfonamides

A highly efficient and practical method for the synthesis of N-arylsulfonamides has been developed by a heterogeneous copper-catalyzed Chan–Lam coupling between sulfonyl azides and boronic acids.

Tridentate Hydroxy-Functionalised MCM-41-Immobilised Copper(I) Complex as an Efficient and Recyclable Catalyst for Coupling of Aryl Iodides with Thiols

The C–S coupling reaction of aryl iodides with thiols was achieved at 110 °C in DMF/dioxane (V/V, 1:9) in the presence of a tridentate hydroxy-functionalised MCM-41-immobilised copper(I) complex [MCM-41-3OH-CuI] with Cs2CO3 as base to afford a variety of diaryl sulfides in good to excellent yields. The MCM-41-3OH-CuI catalyst can be easily recovered by a simple filtration and reused for at least six times without significant loss of activity.

A highly efficient and reusable MCM-41-immobilized bipyridine copper(i) catalyst for the C–Se coupling of organoboronic acids with diaryl diselenides

A heterogeneous copper-catalyzed cross-coupling reaction of diaryl diselenides with organoboronic acids for the synthesis of diorganyl selenides has been described.