Heck Cross-coupling Research Articles

Efficient Synthesis of Novel Phostone and Phostam Derivatives via Regioselective Intramolecular Heck Cyclizations of (2-Iodobenzyl)buta-1,3-dienylphosphonates, (2-Iodophenyl)buta-1,3-dienylphosphonates, and N-(2-Iodophenyl)-P-buta-1,3-dienylphosphonamidates.

Here, we report the intramolecular Heck cross-coupling of 1,3-dienylphosphonates, affording unique and regioselective access to unprecedented benzofused phostone and phostam derivatives. The reactions proceeded under operationally simple and mild conditions with a wide substrate scope.

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.

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.

The ubiquitous P(o-tol)3 ligand promotes formation of catalytically-active higher order palladacyclic clusters.

The Herrmann-Beller catalyst, Pd[(C^P)(μ2-OAc)]2, is readily formed by reaction of the cyclic trimer of 'Pd(OAc)2' with P(o-tol)3. In the presence of hydroxide, Pd(C^P)(μ2-OAc)]2 converts to [Pd(C^P)(μ 2 -OH)]2. Here, we report how this activated Pd precatalyst species, and related species, serve as a conduit for formation of higher order Pd n clusters containing multiple cyclopalladated P(o-tol)3 ligands. The catalytic competency of a Pd4-palladacyclic cluster is demonstrated in an arylated Heck cross-coupling, which is comparable to the base-activated form of Herrmann's catalyst, namely [Pd(C^P)(μ2-OH)]2. The findings show that 'simple' ubiquitous phosphine ligands can promote higher order Pd speciation, moving beyond well-known phosphine-ligated Pd1 and Pd2 complexes. The findings challenge the status quo in the field, in that phosphine ligands can ligate higher order Pd n species which are catalytically competent species in cross-coupling reactions.

Palladium-Loading Ceramic Catalytic Membrane Reactors for Mizoroki–Heck Reaction

AbstractThe general and efficient palladium-loading ceramic catalytic membrane reactor has been first reported to apply in the Mizoroki–Heck reaction. The as-fabricated catalytic membrane Pd-KH792-CM has shown high activity and selectivity in the flow-through Mizoroki–Heck reactions. The consistently high activity of the catalytic membrane in the five cycles has also proved its good stability and recyclability. Synthesis of drug molecules has further demonstrated that the catalytic membrane protocol is a powerful and comprehensive alternative to the traditional Mizoroki–Heck cross-coupling.

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.

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.

Cyrene: a bio-based solvent for the Mizoroki-Heck reaction of aryl iodides.

The development of greener and more sustainable methods, as well as the adaptation of already existing protocols to more environmentally friendly procedures, has become crucial for organic synthesis. The introduction and utilization of greener solvents is a very promising alternative, especially when they can replace toxic organic solvents in the known and widely used organic reactions. Cyrene has appeared to be an excellent alternative solvent for a number of organic reactions. In this work, the development of a new, greener and more economical protocol for the Mizoroki-Heck reaction is described, using Cyrene as the green solvent and Pd/C as the palladium catalyst source. A wide substrate scope for the coupling of aryl iodides with acrylamides, acrylates, acrylic acid, acrylonitrile and styrene was demonstrated. The recyclability of Cyrene and the leaching of palladium in the final product were examined in order to enhance the industrial applicability of this protocol. Furthermore, the synthesis of the natural product piperlotine A is reported.

Preparation of a pyridyl covalent organic framework via Heck cross-coupling for solid-phase microextraction of perfluoropolyether carboxylic acids in food

The growing detection of emerging perfluoropolyether carboxylic acids (PFECAs) in food has raised considerable concerns about their high persistence, bioaccumulation, and toxicity. In this study, a pyridine-functionalized covalent organic framework (Py-COF) was synthesized by introducing basic pyridyl groups into Br-COF via Heck cross-coupling. According to density functional theory, PFECAs were adsorbed in the pore sites of Py-COF via O–···HN+ interaction, which was the stable and predominant adsorption configuration. After systematic characterization, Py-COF was used as the coating for solid-phase microextraction combined with high-performance liquid chromatography-tandem mass spectrometry (SPME-HPLC-MS/MS) for the efficient determination of PFECAs in food. Under the optimum conditions, the method showed satisfactory linearity (R2 ≥ 0.998), low limits of detection (0.001–0.004 ng g−1), and good relative recoveries (82.5 %–112 %). The established method was satisfactorily used for the analysis of trace PFECAs in food samples.

Tailor-Made POLITAG-Pd0 Catalyst for the Low-Loading Mizoroki–Heck Reaction in γ-Valerolactone as a Safe Reaction Medium

In this contribution, we have reported our study on the fine-tuned design and synthesis of new POLITAGs-Pd0 (POLymeric Ionic TAG) catalytic systems with the intention of defining highly efficient heterogeneous palladium catalysts stabilized by ionic tags able to operate at a very low loading while being fully recoverable/reusable. By varying both the support and the ratio between the metal and immobilized ionic tag, we have accessed five different heterogeneous catalytic systems that have been fully characterized (EA, XPS, TEM, and HR-TEM) to investigate their morphological differences. The catalytic efficiency of the newly prepared POLITAGs-Pd0 materials was then tested and compared in the representative Mizoroki–Heck cross-coupling reaction, a universally investigated and widely useful process. A close correlation between the catalyst support and catalytic performances has been highlighted. The best system POLITAG-Pd0-HM features a high TOF value (26,786 h–1), affording the final products in high isolated yields by using as little as only 0.0007 mol % of Pd. Moreover, this high catalytic activity coupled with the use of γ-valerolactone (GVL) as a green reaction medium has led to the definition of a very efficient waste-minimized protocol. The newly designed catalyst has been utilized in the representative synthesis of Amiloxate, a widely used sunscreen agent, that could be prepared with negligible metal contamination and very low E-factor.

Synthesis of Bio-Inspired 1,3-Diarylpropene Derivatives via Heck Cross-Coupling and Cytotoxic Evaluation on Breast Cancer Cells.

The Heck cross-coupling reaction is a well-established chemical tool for the synthesis of unsaturated compounds by formation of a new C-C bond. In this study, 1,3-diarylpropene derivatives, designed as structural analogues of stilbenoids and dihydrostilbenoids, were synthesised by the palladium-catalysed reactions of 2-amidoiodobenzene derivatives with either estragole or eugenol. The products were obtained with high (E) stereoselectivity but as two regioisomers. The ratios of isomers were found to be dependent on the nature of the allylbenzene partner and were rationalised by electronic effects exercising a determining influence in the β-hydride elimination step. In addition, the cytotoxic effects of all the Heck reaction products were evaluated against MCF-7 and MDA-MB-231 human breast cancer cells, with unpromising results. Among all, compound 7d exhibited weak cytotoxic activity towards MCF-7 cell lines with IC50 values of 47.92 µM in comparison with tamoxifen and was considered to have general toxicity (SI value < 2).

Sequential Heck Cross-Coupling and Hydrothiolation Reactions Taking Place in the Ligand Sphere of a Chiral Dehydroalanine Ni(II) Complex: Asymmetric Route to β-Aryl Substituted Cysteines.

A practically useful protocol for the asymmetric synthesis of artificial β-aryl-substituted cysteine derivatives was developed through sequential Pd(II)-catalyzed Heck cross-coupling with aryl iodides and hydrothiolation reaction with various alkyl thiols in the presence of triethylamine taking place in the ligand sphere of a robust and bench-stable chiral dehydroalanine Ni(II) complex. The subsequent acidic decomposition of the single diastereomeric Ni(II) complexes led to the target enantiopure cysteine derivatives.

Pd-PEPPSI N-Heterocyclic Carbene Complexes from Caffeine: Application in Suzuki, Heck, and Sonogashira Reactions.

The first synthesis of Pd-PEPPSI N-heterocyclic carbene complexes derived from the abundant and renewable natural product caffeine is reported. The catalysts bearing 3-chloro-pyridine, pyridine and N-methylimidazole ancillary ligands were readily prepared from the corresponding N9-Me caffeine imidazolium salt by direct deprotonation and coordination to PdX2 in the presence of N-heterocycles or by ligand displacement of PdX2(Het)2. The model Pd-PEPPSI-caffeine complex has been characterized by x-ray crystallography. The complexes were successfully employed in the Suzuki cross-coupling of aryl bromides, Suzuki cross-coupling of amides, Heck cross-coupling and Sonogashira cross-coupling. Computational studies were employed to determine frontier molecular orbitals and bond order analysis of caffeine derived Pd-PEPPSI complexes. This class of catalysts offers an entry to utilize benign and sustainable biomass-derived Xanthine NHC ligands in the popular Pd-PEPPSI systems in organic synthesis and catalysis.

Supported Pd nanoparticles on micro structured chitosan-MgAl layered double hydroxide hydrogel beads as a sustainable, effective, and recyclable nanocatalyst for Heck cross-coupling reactions

In this study, a heterogeneous nano-system with sustainable, green, highly effective, and easily recoverable properties was developed through deposition of palladium nanoparticles on chitosan-MgAl layered double hydroxide hydrogel beads (CS-MgAl LDH). Full characterization of the system denoted as Pd-CS-MgAl LDH nanocatalyst was performed by various analytical techniques including FT-IR, FE-SEM, EDS, TEM, and XRD analyses. The catalytic activity of Pd-CS-MgAl LDH was then explored in Heck cross coupling reaction, and the tests confirmed that Pd-CS-MgAl LDH is an effective and useful nanocatalyst which can couple different aryl halides with yields in the range of 90–98%. Additionally, it was found that Pd-CS-MgAl LDH nanocatalyst displays higher catalytic performance compared to other reported catalysts. Moreover, Pd-CS-MgAl LDH nanocatalyst was facilely isolated and recycled for 5 successive runs without a discernible change in its performance, showing that Pd-CS-MgAl LDH has good recoverability and practical application potential.

Syntheses of Anthracene-Centered Large PAH Diimides and Conjugated Polymers.

Polycyclic aromatic hydrocarbon (PAH) structures with suitable electron-withdrawing groups are useful building blocks for developing optical and electron-transporting materials. Here, we report the application of a double benzannulation process to the syntheses of PAH diimides with enlarged π-frameworks featuring a central anthracene moiety. The preparations are realized by copper-catalyzed [4+2] cycloaddition of ethynyl-substituted aromatic dicarboximide to 2,5-bis(phenylethynyl)terephthalaldehyde, followed by intramolecular photocyclization or direct arylation via Heck cross coupling. A central symmetric benzo[1,2-k:4,5-k']-bis(fluoranthene)-3,4,12,13-tetracarboxyl diimide (BFDI) is acquired, with the single crystal structure revealing its completely planar polycyclic skeleton. Such a shape-persistent PAH expectedly exhibits a tendency to stack face-to-face and forms J-aggregates. Moreover, BFDI can be difunctionalized site-selectively at the reactive 9 and 10 positions of the anthracene unit and then applied to prepare conjugated polymers. When coupled with 1,4-diketopyrrolo[3,4-c]-pyrrole (DPP) via thiophene and dithiophene linkers, two polymers with significantly broadened absorption bands extended to the near-infrared regime are obtained, evidencing the effective π-conjugative extension ability of BFDI unit.

A New Chiral Cyclopalladated Ferrocenylimine Self-assembly Polymeric Film supported on Silicon for Heck and Suzuki-coupling Reactions

A new chiral cyclopalladated ferrocenyl imine catalyst (called 4a2) was designed and synthesized, and its self-assembly catalytic polymeric brush supported on silicon (denoted as Si@PB4a2) was also fabricated by surface-initiated atom transfer radical polymerization (ATRP) and characterized. The catalytic properties of monomer 4a2 in homogeneous and Si@PB4a2 in heterogeneous in Heck and Suzuki cross-coupling were investigated, respectively. They exhibited higher catalytic activity in Heck, and Suzuki coupling reactions in homogeneous and heterogeneous using water as the solvent, and the catalytic activity of Si@PB4a2 with a turn of number (TON,11933 molproduct/molcat) in heterogeneous was 200 times more than that of 4a2 in homogeneous due to the ordered arrangement of the catalyst supported on silicon. Si@PB4a2 had high recyclability, i.e., at least eight runs and six runs, in Suzuki and Heck coupling reactions, respectively.

DCID-mediated Heck cross-coupling of phenolsviaC–O bond activation

In this work a palladium-catalyzed Heck cross-coupling of phenols using dichloroimidazolidinedione (DCID) as a new reagent for the activation of C–O bonds has been developed for the first time.

2‐Pyridyl‐Benzimidazole‐Pd (II) Complex Supported on Magnetic SBA‐15: An Efficient and Magnetically Retrievable Catalyst for the Heck Reaction

Abstract2‐(2’‐Pyridyl)benzimidazole (PyBzIm) was grafted onto magnetic mesoporous silica particles (Fe3O4@SBA) via a simple click reaction, and then further reacted with Na2PdCl4 in methanol. The catalyst, Fe3O4@SBA−PyBzIm−Pd(II), was characterized with FT‐IR, thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM), Brunauer‐Emmett‐Teller surface area measurement (SBET), and wide‐angle X‐ray diffraction spectroscopy (XRD). X‐Ray photoelectron spectroscopy (XPS) studies confirmed some C=N nitrogen atoms interact with palladium in the +2 oxidation state. The supported complex was found to catalyze the Heck cross coupling reaction of aryl halides and olefins. It also presents an excellent recycling efficiency over six consecutive runs without significant loss of catalyst reactivity.

C(sp3),N palladacyclic complexes bearing flexidentate ligands as efficient (pre)catalysts for Heck olefination of aryl halides

C,N-cyclopalladated complexes are among the most robust and widely used (pre)catalysts of cross-coupling reactions, combining long shelf life with high catalytic activity. In this report, we describe synthesis and properties of new Pd(II) complexes of a flexidentate ligand – 2,2-dimethyl-5-(2-pyridyl)pentane-3,5-dione (HL). Its coordinating properties resulted in the formation of two stereoisomeric cis- and trans-PdL2 complexes each with one ligand in O,O- and the other in N,C(sp3)-coordination modes. The solid-state structures have been established by means of single-crystal X-ray diffraction methods and are retained in solution as indicated by NMR spectroscopy. Both these isomers proved to be efficient (pre)catalysts of phosphine-free Heck cross-coupling of iodoarenes with olefins.