Heck Cross-coupling Reactions Research Articles

Phosphine-incorporated Metal-Organic Framework for Palladium Catalyzed Heck Coupling Reaction.

As an emerging material with the potential to combine the high efficiency of homogeneous catalysts and high stability and recyclability of heterogeneous catalysts, metal-organic frameworks (MOFs) have been viewed as one of the candidates to produce catalysts of the next generation. Herein, we heterogenized the highly active mono(phosphine)-Pd complex on surface of UiO-66 MOF, as a catalyst for Suzuki and Heck cross coupling reactions. The successful immobilization of these Pd-monophosphine complexes on MOF surface to form UiO-66-PPh2-Pd was characterized and confirmed via comprehensive set of analytical methods. UiO-66-PPh2-Pd showed high activity and selectivity for both Suzuki and Heck Cross Coupling Reactions. This strategy enabled facile access to mono(phosphine) complexes which are challenging to design and require multistep synthesis in homogeneous systems, paving the way for future MOF catalysts applications by similar systems.

Efficient heck and Suzuki-Miyaura cross-coupling reactions catalyzed by heterogeneous Pd NPs-decorated porous MOF catalysts under mild conditions

Carbon-carbon coupling reactions are extremely interesting for a variety of applications, including pharmaceuticals and biologically active compounds. In this study, we investigated the utilization of functionalized MIL-101 porous MOF for stabilizing palladium nanoparticles (NPs) and examined their catalytic performance in the cross-coupling reaction of aryl halides with phenylboronic acid and methyl acrylate under mild conditions. To achieve this, MIL-101(Al) was synthesized using a solvothermal method, followed by functionalization with environmentally friendly l-Cysteine (CYS). Subsequently, the MIL-101(Al)-CYS compound was immersed in an ethanolic solution of palladium and stirred overnight. The catalyst exhibited remarkable efficiency (over 90 %) in Suzuki and Heck cross-coupling reactions, demonstrating excellent activity and recyclability. The reactions were conducted in polyethylene glycol 200 (PEG 200), a green reaction medium, at temperatures of 70 °C and 60 °C, with Pd loadings of 0.22 and 0.08 mol%, respectively. MOF-based catalysts, owing to their highly tunable structures and porosity, hold great promise as heterogeneous catalysts in organic reactions.

Development and synthesis of a novel salen-type ligand based on phenylalanine for Mizoroki-Heck, and S-arylation cross-coupling reactions

In this article, we introduced a novel salen-type ligand precursor and applied it in the Pd-catalyzed Mizoroki–Heck and Cu-catalyzed S-arylation cross-coupling reactions. For the preparation of this structure, (DL)-phenyl alanine was employed as a starting material. These ligand precursor and related catalytic system can be readily synthesised. Various aryl halides (-I, -Br) and alkenes were applied successfully in this protocol to give the corresponding Mizoroki-Heck cross-coupling and S-arylated products in high to excellent yields.

Biogenically synthesized palladium nanoparticles for hydrogen evolution study: An efficient catalyst for 4-nitrophenol reduction and C-C coupling reactions

Indian cork extract is employed for the greener production of palladium nanoparticles (Pd NPs) an effective heterogeneous catalyst with a concentration of 30.1%. Plant extract-mediated phytochemicals were found responsible for reducing Pd(II) to Pd(0) without the aid of an external reducing agent. XRD, UV–visible, and other analyses demonstrated the successful formation of Pd NPs. These NPs were evident to have better electrocatalytic activity in the hydrogen evolution reaction (HER) in an acidic medium. The Tafel slope (174 mV/dec) of the Pd NPs catalyst confirmed the Volmer-Heyrovsky mechanism for HER study and demonstrated the electrochemical desorption of hydrogen is the rate-determining step. In terms of synthetic organic chemistry perspectives, the applicability of Pd NPs has been subsequently demonstrated for the reduction of toxic 4-nitrophenol to synthetically important 4-aminophenol with a minimum catalyst loading at ambient conditions. Additionally, the outstanding catalytic activity of synthesized heterogeneous Pd NPs catalyst has been showcased for direct Heck and Hiyama cross-coupling reactions.

Furaldehyde-based magnetic supported palladium nanoparticles as an efficient heterogeneous catalyst for Mizoroki–Heck cross-coupling reaction

Novel furaldehyde-based magnetic nanoparticles are used as an efficient catalyst for the Mizoroki–Heck reaction of arylhalide and olefins.

Dual photoredox/nickel-catalyzed Mizoroki–Heck cross-coupling reactions

A method for the Mizoroki–Heck reaction of electron-deficient olefins acrylates with aryl bromides to obtain α-arylation products of acrylates via a dual light/nickel catalytic system is described. This transformation features a broad substrate scope, good functional group tolerance.

Sonogashira coupling reactions with ligand-free heterogeneous nanoporous Pd catalyst

The Sonogashira coupling reaction is one of the most important protocols for the production of aryl alkynes. In order to solve the problems existing in Sonogashira cross-coupling reaction, according to the application of nanoporous palladium in Suzuki and Heck cross-coupling reactions, nanoporous palladium was used as the sustainable catalyst for the Sonogashira cross-coupling reaction. A sustainable catalyst system was tested and optimized without cuprous ion, phosphine ligand, or amine additives. Nanoporous palladium catalyst remained stable over five cycles without significant leaching or loss of catalytic activity, and the desired alkynes were obtained in high yields.

One pot preparation of PVA-sodium alginate-PdCl2 with excellent recyclability properties as a catalyst for Heck cross-coupling reactions

One pot preparation of PVA-sodium alginate-PdCl2 with excellent recyclability properties as a catalyst for Heck cross-coupling reactions

A new activated carbon-supported Pd–ZnO catalyst for Heck Cross-coupling reactions

In this work, to develop catalysts for Heck-type coupling reactions, a hybrid ZnO-Pd nanocatalyst was fabricated on activated carbon sourced from polymer debris. Such techniques as transmission electron microscopy (TEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) surface area analysis were applied for the identification of hybrid materials. The catalytic conversion capacity of the hybrid material was tested by Heck cross-coupling reactions through a series of aryl iodides and bromines with styrene. It was observed that cross-coupling reactions were catalyzed by designed hybrid material with a reaction yield of more than 90%. The recyclability of the hybrid was also tested by Heck reaction of 1-bromo-4-nitrobenzene with styrene, and the hybrid catalyst showed remarkable stability up to 5 cycles.

Biomacromolecule supported N-heterocyclic carbene-palladium(II) as a novel catalyst for Suzuki–Miyaura and Mizoroki–Heck cross-coupling reactions

Biomacromolecule supported N-heterocyclic carbene-palladium(II) as a novel catalyst for Suzuki–Miyaura and Mizoroki–Heck cross-coupling reactions

Palladium CNC-pincer complex supported on magnetic nanospindles as a highly efficient and recyclable nanocatalyst in Mizoroki–Heck cross-coupling and reduction of nitroarenes

Fe3O4 nanospindles were synthesized through the hydrothermal method followed by thermal treatment. The composite of Fe3O4@SiO2 core–shell nanospindles was synthesized by the Stuber process via the hydrolysis of tetraethyl orthosilicate (TEOS) in the presence of Fe3O4 nanospindles. Palladium triazine‐bridged bisimidazolium pincer complex was successfully supported on Fe3O4@SiO2 core–shell nanospindles. The magnetic nanospindles‐supported palladium CNC-pincer complex was used as a practical and recyclable catalyst in the Mizoroki–Heck cross-coupling reaction and reduction of nitroarenes.

On-Surface Cross-Coupling Reactions

On-surface synthesis, as a bottom-up synthetic method, has been proven to be a powerful tool for atomically precise fabrication of low-dimensional carbon nanomaterials over the past 15 years. This method relies on covalent coupling reactions that occur on solid substrates such as metal or metal oxide surfaces under ultra-high-vacuum conditions, and the achievements with this method have greatly enriched fundamental science and technology. However, due to the complicated reactivity of organic groups, distinct diffusion of reactants and intermediates, and irreversibility of covalent bonds, achieving the high selectivity of covalent coupling reactions on surfaces remains a great challenge. As a result, only a few on-surface covalent coupling reactions, mainly involving dehalogenation and dehydrogenation homocoupling, are frequently used in the synthesis of low-dimensional carbon nanosystems. In this Perspective, we focus on the development and synthetic applications of on-surface cross-coupling reactions, mainly Ullmann, Sonogashira, Heck, and divergent cross-coupling reactions.

Catalysis of a Bis-Caffeine Palladium(II) NHC-Pincer Complex

A tridentate bis-NHC Pd complex, based on caffeine, was studied for its catalytic activity. This complex displayed a high catalytic activity in the Suzuki–Miyaura and Mizoroki–Heck cross-coupling reactions of aryl halides. The Sonogashira cross-coupling was also investigated but reveals a fast plateauing of the reaction. Aryl iodides as well as aryl bromides react when equipped with either electron-donating or electron-withdrawing substituents. Aryl chlorides, which contained electron-withdrawing groups, were also reactive under the applied conditions.

In-situ formation of electron-deficient Pd sites on AuPd alloy nanoparticles under irradiation enabled efficient photocatalytic Heck reaction

Plasmonic metal nanoparticles have emerged as important candidates for photocatalysis. Numerous studies have shown that coupling of a plasmonic component (such as Au) as the light energy harvester with a catalytically active metal component (such as Pd) to form hybrid or alloy structures could achieve enhanced catalytic performance. However, the microscopic mechanism relative to the multicomponent plasmonic photocatalysis is still elusive. Here, we find that the electron-deficient Pd sites (Pdδ+) on AuPd alloy nanoparticle were formed under visible light irradiation, which play a decisive role in the AuPd alloy nanoparticle photocatalysis. The in-situ formed Pdδ+ under irradiation offers ideal platform for the catalytic reaction which is comparable to that under thermal heating conditions (>100 °C). The AuPd alloy nanoparticles show excellent conversion and selectivity for visible-light-driven Heck cross-coupling reaction under ambient conditions. The combination of experimental and density functional theory results suggest that the photocatalytic Heck reaction proceeds via a new radical-based single-electron transfer pathway on the AuPd alloy, and the in-situ formed Pdδ+ sites ideally provided efficient catalytic sites for the activation of reactant with much lower activation energy barrier under irradiation. The present work sheds light on the new mechanistic understandings of bimetallic plasmonic photocatalysis.

Insightful Improvement in the Design of Potent Uropathogenic E. coli FimH Antagonists

Selective antiadhesion antagonists of Uropathogenic Escherichia coli (UPEC) type-1 Fimbrial adhesin (FimH) are attractive alternatives for antibiotic therapies and prophylaxes against acute or recurrent urinary tract infections (UTIs) caused by UPECs. A rational small library of FimH antagonists based on previously described C-linked allyl α-D-mannopyranoside was synthesized using Heck cross-coupling reaction using a series of iodoaryl derivatives. This work reports two new members of FimH antagonist amongst the above family with sub nanomolar affinity. The resulting hydrophobic aglycones, including constrained alkene and aryl groups, were designed to provide additional favorable binding interactions with the so-called FimH "tyrosine gate". The newly synthesized C-linked glycomimetic antagonists, having a hydrolytically stable anomeric linkage, exhibited improved binding when compared to previously published analogs, as demonstrated by affinity measurement through interactions by FimH lectin. The crystal structure of FimH co-crystallized with one of the nanomolar antagonists revealed the binding mode of this inhibitor into the active site of the tyrosine gate. In addition, selected mannopyranoside constructs neither affected bacterial growth or cell viability nor interfered with antibiotic activity. C-linked mannoside antagonists were effective in decreasing bacterial adhesion to human bladder epithelial cells (HTB-9). Therefore, these molecules constituted additional therapeutic candidates' worth further development in the search for potent anti-adhesive drugs against infections caused by UPEC.

Supramolecular Pd@methioine-EDTA-chitosan nanocomposite: an effective and recyclable bio-based and eco-friendly catalyst for the green Heck cross-coupling reaction under mild conditions.

Supramolecular palladium(ii) supported on modified chitosan by dl-methionine using an ethylenediaminetetraacetic acid linker (Pd@MET-EDTA-CS) was designed and prepared through a simple procedure. The structure of this novel supramolecular nanocomposite was characterized by different spectroscopic, microscopic and analytical techniques including FTIR, EDX, XRD, FESEM, TGA, DRS, TEM, AA, and BET. The obtained bio-based nanomaterial was successfully investigated, as a highly efficient and green heterogeneous catalyst, in the Heck cross-coupling reaction (HCR) for the synthesis of various valuable biologically active cinnamic acid ester derivatives from the corresponding aryl halides using several acrylates. Indeed, aryl halides containing I or Br survived very well under optimized conditions to afford the corresponding products compared to the substrates with Cl. The prepared Pd@MET-EDTA-CS nanocatalyst promoted the HCR in high to excellent yields and short reaction times with minimum Pd loading (0.0027 mol%) on its structure as well as without any leaching occurring during the process. The recovery of the catalyst was performed by simple filtration and the catalytic activity remained approximately constant after five runs for the model reaction.

A palladium(0)-threonine complex immobilized on the surface of magnetic mesocellular foam: an efficient, stable, and magnetically separable nanocatalyst for Suzuki, Stille, and Heck cross-coupling reactions.

In this study, a new palladium nanocatalyst was supported on l-threonine functionalized magnetic mesocellular silica foams (MMCF@Thr-Pd) and was characterized by FT-IR, XRD, BET, SEM, EDS, VSM, TGA, ICP-OES and elemental mapping techniques. The obtained MMCF@Thr-Pd performance can show excellent catalytic activity for Stille, Suzuki, and Heck coupling reactions, and the corresponding products were obtained with high yields. More importantly, the efficient and stable MMCF@Thr-Pd nanocatalyst was recovered by applying an external magnetic field and reused for at least five consecutive runs without a change in the catalytic activity.

Pd@l-asparagine-EDTA-chitosan: a highly effective and reusable bio-based and biodegradable catalyst for the Heck cross-coupling reaction under mild conditions.

In this research, a novel supramolecular Pd(ii) catalyst supported on chitosan grafted by l-asparagine and an EDTA linker, named Pd@ASP-EDTA-CS, was prepared for the first time. The structure of the obtained multifunctional Pd@ASP-EDTA-CS nanocomposite was appropriately characterized by various spectroscopic, microscopic, and analytical techniques, including FTIR, EDX, XRD, FESEM, TGA, DRS, and BET. The Pd@ASP-EDTA-CS nanomaterial was successfully employed, as a heterogeneous catalytic system, in the Heck cross-coupling reaction (HCR) to afford various valuable biologically-active cinnamic acid derivatives in good to excellent yields. Different aryl halides containing I, Br and even Cl were used in HCR with various acrylates for the synthesis of corresponding cinnamic acid ester derivatives. The catalyst shows a variety of advantages including high catalytic activity, excellent thermal stability, easy recovery by simple filtration, more than five cycles of reusability with no significant decrease in its efficacy, biodegradability, and excellent results in the HCR using low-loaded Pd on the support. In addition, no leaching of Pd into the reaction medium and the final products was observed.

3D printing of a palladium-alumina cermet monolithic catalyst: catalytic evaluation in microwave-assisted cross-coupling reactions

A straightforward manufacture strategy is proposed to obtain an efficient and robust palladium-alumina (Pd0/Al2O3) cermet monolithic catalyst, specifically designed to perform safe microwave assisted organic synthesis (MAOS). In this approach, a cermet catalyst with high surface area, controlled composition and adapted shape and dimensions to a microwave reactor vessel is generated via 3D printing technology and sintering. The resulting catalyst has been explored in heterogeneous Suzuki, Sonogashira, Stille and Heck cross-coupling reactions, in MAOS. The Pd0 catalyst is permanently active, stable, without leaching and can be recycled and reused at least 200 reaction cycles. The generation of hot spots, sparking or hazardous discharges is controlled by the effective immobilization of the palladium in the monolithic structure during the reaction. The palladium content is forming part of both the internal and external structure, providing greater mechanical resistance and catalytic activity with respect to the basic ceramic material (alumina).

Efficient and biocompatible new palladium-supported boehmite nanoparticles: synthesis, characterization and application in Suzuki-Miura and Mizoroki-Heck coupling reactions.

Palladium complex-supported on boehmite (Pd(0)-SMTU-boehmite) nanoparticles were synthesized and characterized by using XRD, SEM, EDS, TGA, BET, ICP and FT-IR techniques. When applied as a new catalyst for C-C coupling reactions of Suzuki-Miyaura and Mizoroki-Heck in PEG-400 solvent, the Pd(0)-SMTU-boehmite nanoparticles showed excellent activity and recyclability. The study of palladium leaching by the ICP-OES technique and hot filtration led to the catalyst exhibiting excellent stability and recyclability.