Heck Cross-coupling Reactions Research Articles

Upcycling of Chitin to Cross-Coupling Catalysts: Tailored Supports and Opportunities in Mechanochemistry.

In this study chitin derived from shrimp shells was used in the design of heterogeneous Pd-based catalysts for Heck and Suzuki-Miyaura cross-coupling reactions. The synthesis of Pd nanoparticles supported on N-doped carbons was performed through different approaches, including a sustainable mechanochemical approach, by using a twin-screw extruder. All catalytic systems were characterized by a multitechnique approach and the effect of nanoparticles size, N-doping on the support, and their synergistic interactions were elucidated. Specifically, Kelvin Probe Atomic Force Microscopy provided valuable insights on charge transfer and metal-support interactions. The catalytic behaviour of the samples was investigated in cross-coupling reactions under batch conditions and under semi-continuous flow solvent-free conditions, respectively obtaining a quantitative yield and a noteworthy productivity of 8.7 mol/(gPdh).

Some Terminally Alkenyl-substituted Porphyrins: Synthesis and Attempts of Heck Reaction Leading to Porphyrin–Azulene Dyads

: The synthesis of meso-tetraphenylporphyrin derivatives, double functionalized in one of the phenyl rings (with a nitro group and carbon substituents), is described. 5-(4- Nitroaryl)-10,15,20-triarylporphyrinates react, in the presence of a base (t-BuOK), with carbanions containing a leaving group at the carbanionic center to give products of substitution of hydrogen at ortho-position to the nitro group via vicarious nucleophilic substitution scheme. Their alkylation with allyl bromide or 4-bromobut-1-en (t-BuOK/DMF, at 0-5°C) leads to porphyrins bearing side alkyl chain with a terminal double bond in yields of up to 82%. The above-mentioned double-substituted intermediates are very convenient substrates for Heck cross-coupling reaction. In this study, the synthesis of porphyrin–azulene dyads is reported. In some cases, the formation of highly conjugated systems is observed, with moderate yield. Their structures are interesting from both the porphyrin and azulene point of view.

Pd-catalysed one-pot and three-component sequential chemoselective double cross-coupling: Synthesis of novel 2-aryl-1,3-azoles from 4-bromophenyl tosylate

One of the principles of green and sustainable chemistry is to use green solvents and one-pot synthetic methods which can eliminate the need for drawn-out separation procedures, purification of intermediate compounds, and the production of waste by-products. Considering these concepts of green and sustainable chemistry, an efficient and novel chemoselective one-pot strategy has been developed for the novel synthesis of 2-Aryl-1,3-azoles via Suzuki and Heck cross-coupling reactions via C-2 arylation of azoles under the discriminate temperature using an ionic liquid as green solvent, promoter and ligand. The chemoselective one-pot synthesis, wide substrate scope, moderate to excellent isolated yield of pure products, mild reaction conditions and recycling/reuse of ionic liquid are highlights of this work.

Preparation of highly active and stable magnetically separable Pd NPs encapsulated in mesoporous polymelamine formaldehyde Yolk-Shell nanoreactor for the Mizoroki–Heck cross-coupling reaction

Preparation of highly active and stable magnetically separable Pd NPs encapsulated in mesoporous polymelamine formaldehyde Yolk-Shell nanoreactor for the Mizoroki–Heck cross-coupling reaction

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.

Heck reaction between free base 2-Br-porphyrin and vinyl-ferrocene derivatives. Electrochemical and spectroscopic characterisation of β-functionalised alpha and trans-vinyl-ferrocene porphyrin derivatives. A comparative study

Ferrocene–porphyrin dyads, obtained under new Heck cross-coupling reaction conditions, showed photophysical properties useful for fluorescence redox switches or combined chemodynamic and photodynamic agents.

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.