Heck Cross-coupling Reactions Research Articles

RETRACTED: Nanomagnetic Salamo-based-Pd(0) Complex: an efficient heterogeneous catalyst for Suzuki–Miyaura and Heck cross-coupling reactions in aqueous medium

In order to develop a magnetic nanocatalyst, an asymmetric salamo-based-Palladium(0) complex grafted on Fe3O4 MNPs was synthesized and characterized using physicochemical methods including FT-IR, XRD, SEM, TEM, EDS, ICP-AES, X-ray mapping, TGA and VSM analyses. Catalytic activities of [Fe3O4@H2L‐Pd (0)] were examined towards two catalytic reactions: a) synthesis of biaryls via the Suzuki C-C cross-coupling of phenylboronic acid with aryl halides and b) one-pot synthesis of butyl cinnamates via the Heck C-C cross-coupling of butyl acrylate with aryl halides under green conditions in aqueous medium. Moreover, the effects of the catalyst amount, reaction temperature, type of the solvent and nature of base on catalytic activity were investigated. The [Fe3O4@H2L‐Pd(0)] nanocatalyst was recycled for at least six consecutive reaction cycles without a significant loss of its catalytic activity. This illustrates the sustainable anchoring of palladium(0) on Fe3O4.

Structural Transitions at the Water/Oil Interface by Ionic-Liquid-like Surfactant, 1-Butyl-3-methylimidazolium Dioctyl Sulfosuccinate: Measurements and Mechanism.

Reverse micelle (RM) aggregates have a wide range of applications in various areas of science and technology. A continuous demand exists to replace interfacial surfactant molecules with various nonconventional amphiphiles. Ionic liquid (IL)-like surfactants (IL-surf's) constitute a class of such molecules that are being researched extensively. Here, we have formulated several water/IL-surf/oil microemulsions by optimizing the core droplet size with varying oil phases. The best composition of water/[BMIM][AOT]/IPM ([BMIM][AOT]: 1-butyl-3-methylimidazolium dioctyl sulfosuccinate; IPM: isopropyl myristate) was then analyzed in detail through experimental and computer simulations. Our results from DLS measurements suggest a structural transition from spherical aggregates in the parent water/[Na][AOT]/IPM solution to cylindrical droplets in the IL-surf-based system. The Raman and ATR-FTIR spectral analysis suggest a variation in the microstructure of the water/oil interface due to the differential interaction of the counterions with AOT headgroups and water. Molecular dynamics simulation results provided the direct image of the interface showing a structured versus uneven water/oil interface in [Na][AOT] versus [BMIM][AOT] RMs, where the larger [BMIM] cations weakly bind with the AOT headgroups due to their low charge density. Finally, an application of this IL-surf-based formulation was tested by carrying out a Heck cross-coupling reaction that showed significantly higher yield under milder reaction conditions.

Dendritic structured palladium complexes: magnetically retrievable, highly efficient heterogeneous nanocatalyst for Suzuki and Heck cross-coupling reactions.

The recyclable nanomagnetic Pd-complex PAMAM G0-Pd@γ-Fe2O3 is reported for catalytic C–C cross-coupling reactions of challenging substrates. Mainly, a great variety of aryl chlorides can be used as substrates for Suzuki–Miyaura and Mizoroki–Heck reactions under mild reaction conditions (60–90 °C) and low catalyst loading (<1 mol% Pd) in aqueous media. The presence of numerous polar groups in the polymer matrix increases the solubility of the catalyst in water, thus facilitating its operation in aqueous environments. The immobilization of the catalyst on the surface of a magnetic platform allows its effective recovery and reuse without significant loss of catalytic activity for at least six cycles with total leaching of <1% palladium metal, meeting the requirements for acceptable metal residues in the pharmaceutical industry.

Magnetically Recoverable Nanoparticulate Catalysts for Cross-Coupling Reactions: The Dendritic Support Influences the Catalytic Performance.

Carbon-carbon cross-coupling reactions are among the most important synthetic tools for the preparation of pharmaceuticals and bioactive compounds. However, these reactions are normally carried out using copper, phosphines, and/or amines, which are poisonous for pharmaceuticals. The use of nanocomposite catalysts holds promise for facilitating these reactions and making them more environmentally friendly. In the present work, the PEGylated (PEG stands for poly(ethylene glycol) pyridylphenylene dendrons immobilized on silica loaded with magnetic nanoparticles have been successfully employed for the stabilization of Pd2+ complexes and Pd nanoparticles. The catalyst developed showed excellent catalytic activity in copper-free Sonogashira and Heck cross-coupling reactions. The reactions proceeded smoothly in green solvents at low palladium loading, resulting in high yields of cross-coupling products (from 80% to 97%) within short reaction times. The presence of magnetic nanoparticles allows easy magnetic separation for repeated use without a noticeable decrease of catalytic activity due to the strong stabilization of Pd species by rigid and bulky dendritic ligands. The PEG dendron periphery makes the catalyst hydrophilic and better suited for green solvents. The minor drop in activity upon the catalyst reuse is explained by the formation of Pd nanoparticles from the Pd2+ species during the catalytic reaction. The magnetic separation and reuse of the nanocomposite catalyst reduces the cost of target products as well as energy and material consumption and diminishes residual contamination by the catalyst. These factors as well as the absence of copper in the catalyst makeup pave the way for future applications of such catalysts in cross-coupling reactions.

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.

Palladium supported on urea-containing porous organic polymers as heterogeneous catalysts for C–C cross coupling reactions and reduction of nitroarenes

The novel palladium nanoparticles (Pd@POPs) were successfully prepared with controllable sizes and dispersity through the introduction of H2PdCl4 into urea-linked porous organic polymers (POPs) in an aqueous environment followed by reducing Pd(II) to Pd(0) by NaBH4. The newly prepared Pd@POPs were thoroughly characterized by FT-IR, ICP-AES, BET, XRD, SEM and TEM. Furthermore, the catalytic reactivities of this novel Pd@POPs were investigated via Heck, Suzuki-Miyaura cross-coupling reaction and nitroarene reduction, and they exhibited superior catalytic performances in all these three reactions, producing the corresponding products in up to quantitative yields. Additionally, the Pd@POPs had excellent recyclability in both Heck and Suzuki-Miyaura cross-coupling reactions with the repeating time up to four times and ten times, respectively, along with no obvious decrease of catalytic reactivities.

Facile Synthesis and Characterization of Palladium@Carbon Catalyst for the Suzuki-Miyaura and Mizoroki-Heck Coupling Reactions

Palladium-based carbon catalysts (Pd/C) can be potentially applied as an efficient catalyst for Suzuki–Miyaura and Mizoroki–Heck coupling reactions. Herein, a variety of catalysts of palladium on activated carbon were prepared by varying the content of ‘Pd’ via an in situ reduction method, using hydrogen as a reducing agent. The as-prepared catalysts (0.5 wt % Pd/C, 1 wt % Pd/C, 2 wt % Pd/C and 3 wt % Pd/C) were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and Brunauer–Emmett–Teller (BET) analyses. The catalysts were tested as a coupling catalyst for Suzuki–Miyaura coupling reactions involving aryl halides and phenyl boronic acid. The optimization of the catalyst by varying the palladium content on the activated carbon yielded Pd/C catalysts with very high catalytic activity for Suzuki reactions of aryl halides and a Mizoroki–Heck cross-coupling reaction of 4-bromoanisol and acrylic acid in an aqueous medium. A high ‘Pd’ content and uniform ‘Pd’ impregnation significantly affected the activity of the catalysts. The catalytic activity of 3% Pd/C was found to make it a more efficient catalyst when compared with the other synthesized Pd/C catalysts. Furthermore, the catalyst reusability was also tested for Suzuki reactions by repeatedly performing the same reaction using the recovered catalyst. The 3% Pd/C catalyst displayed better reusability even after several reactions.

Confined synthesis of homogeneous Tetrakis(triphenyl phosphine) palladium within hollow porous polymeric nanospheres for catalysis application

Abstract In this paper, we report a facile “ship-in-bottle” confined synthesis method to encapsulate the large-sized homogeneous tetrakis(triphenyl phosphine) palladium (Pd(PPh3)4) catalyst into hyper-crosslinked hollow porous polymeric nanospheres (H-PPNs). The hyper-crosslinked microporous shell can prevent the free Pd(PPh3)4 molecules escaping from the cavity in H-PPNs. The obtained Pd(PPh3)4@H-PPNs catalysts not only retain the high catalytic reactivity (>99%) of homogeneous Pd(PPh3)4 for Suzuki−Miyaura (turnover of frequency of 2829 h−1) and Heck cross-coupling reactions, but also show outstanding reusability just like that of heterogeneous catalysis system.

Heck Cross-Coupling Reactions in Ionic Liquid mediated Pd Nanocatalysts

: We straightforwardly synthesized 18 different types of palladium nanoparticles by using a series of palladium metal precursors and ionic liquids. All the materials went for XRD, TEM, and ICPOES analysis, before going to Heck cross-coupling reaction as a catalyst. We evaluated the catalytic performance of our developed IL#Pd MNP catalyst over Heck cross-coupling reaction between different terminal olefins with various 3-iodo-benzopyrones, including sterically hindered, electron-rich, electron neutral and electron-deficient systems. We obtained the Heck cross-coupling reaction product in good to average yield under phosphine free reaction condition with an added advantage of 6 times catalyst recycling.

Prospects and Applications of Palladium Nanoparticles in the Cross-coupling of (hetero)aryl Halides and Related Analogues.

Discovering efficient methods for the formation of carbon‐carbon bonds is a central ongoing theme in organic synthesis. Cross‐coupling reactions catalysed by metal nanoparticles are attractive alternatives to the traditional use of metal counterparts due to the catalytic tunability, selectivity, recyclability and reusability of the nanoparticles. The ongoing search for sustainable processes demands that reusable and environmentally benign catalysts are used. While the advantages of nanoparticles catalysts over bulk catalysts cannot be overemphasised, the problem of sintering, agglomeration and leaching are drawbacks to their full industrial applications. Hence, efforts are being made towards advancing the efficiency of the catalytic nanoparticle systems over the years. This review presents the progress, the challenges and the prospects of palladium nanoparticle with focus on Heck, Suzuki, Hiyama and Sonogashira cross‐coupling reactions involving (hetero) aryl halides and the analogues.

Introduction of a Recyclable Basic Ionic Solvent with Bis-(NHC) Ligand Property and The Possibility of Immobilization on Magnetite for Ligand- and Base-Free Pd-Catalyzed Heck, Suzuki and Sonogashira Cross-Coupling Reactions in Water

A new versatile and recyclable NHC ligand precursor has been developed with ligand, base, and solvent functionalities for the efficient Pd-catalyzed Heck, Suzuki and Sonogashira cross-coupling reactions under mild conditions. Furthermore, NHC ligand precursor was immobilized on magnetite and its catalytic activity was also evaluated towards the coupling reactions as a heterogeneous catalyst. The NHC ligand precursor was prepared with imidazolium functionalization of TCT followed by a simple ion exchange by hydroxide ions. However, the results revealed an excellent catalytic activity for the both homogeneous and heterogeneous catalytic systems. 1.52 g.cm−3 and 1194 cP was obtained for the density and viscosity of the NHC ligand precursor respectively. On the other hand, the heterogeneous type could be readily recovered from the reaction mixture and reused for several times while preserving its properties. Heterogeneous nature of the magnetic catalyst was studied by hot filtration, mercury poisoning, and three-phase tests. High to excellent yields were obtained for all entries for the both homogeneous and heterogeneous catalysts, which reflects the high consistency of the catalyst.

Synthesis and characterization of chitosan pyridyl imine palladium (CPIP) complex as green catalyst for organic transformations

In this work, the modification of chitosan using 2-acetyl pyridine has been used to prepare an intermediate, chitosan pyridyl imine (CPI), in first step and then in second step it is further reacted with Pd(OAc)2 to develop chitosan pyridyl imine palladium (CPIP) complex catalyst in a very simplistic way. The formed CPIP has been extensively characterized with respect to raw chitosan utilizing methods including FT-IR, pyrolysis GC–MS, XRD, XPS, FE-SEM, EDS, TGA-DTG and DSC. TG-DSC study suggested that the catalyst is thermally stable up to 300 °C. This catalyst shows an excellent activity in the reduction of toxic pollutant nitrobenzene to less toxic aniline. CPIP complex has also been found to give magnificent results in Suzuki–Miyaura and Heck cross-coupling reactions, and therefore, using this green catalyst, the toxic phosphine ligand can be excluded from cross-coupling reactions. This study furnishes an economic and eco-friendly catalyst for organic transformation in sustainable chemistry.

Ionic liquid immobilized Cu(I)–hydrazone–triphenylphosphine complex: an easily recyclable catalytic system for Suzuki and Heck cross couplings

A highly efficient, reusable, catalytic system of Heck and Suzuki cross-coupling reactions was observed for an inexpensive copper complex dispersed in ethyl-methyl imidazolium hexafluorophosphate medium, [EMIM]PF6. The reaction conditions were optimized by studying the effects of temperature, catalyst concentration, solvent, and time. This method functions for a variety of substrates towards the cross-coupling reactions. Most notably, the catalyst – ionic liquid mixture was easily recoverable and reused six times without much loss in the catalytic activity, causing a notably very low impact on the environment.

Facile one-pot synthesis of superfine palladium nanoparticles on polydopamine-functionalized carbon nanotubes as a nanocatalyst for the Heck reaction

Heterogeneous Pd nanocatalysts are efficient catalysts for the Heck reaction but require multi-step, sophisticated procedures and harsh reaction conditions. In this work, a green and facile strategy has been developed to decorate Pd nanoparticles on polydopamine (PDA)-coated multi-walled carbon nanotubes (Pd/CNTs-PDA) via a one-pot method. The obtained nanoparticles were characterized by various techniques including transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, which proved that Pd NPs are well-dispersed on the PDA and between the surfaces of the PDA and CNTs. The resultant Pd/CNTs-PDA catalysts exhibit excellent catalytic reactivity toward the Heck reaction at low temperatures. Moreover, by DFT simulation, we found that during the PDA polymerization process, a large number of unsaturated N and CO species are more active than the groups on the PDA end product to anchor Pd NPs. The results provide evidence that the catalyst synthesized by the one-pot method exhibited good activity because sufficient active sites could be created to effectively promote Pd NPs dispersion during the dopamine polymerization process. Additionally, the Pd/CNTs-PDA catalyst was successfully employed in Heck cross-coupling reactions with various functionalized substrates. This method opens a window for the fabrication of high-performance nanocomposite catalysts under mild conditions using simple methods and has several potential applications.

Pd/Cu-Free Cobalt-Catalyzed Suzuki and Heck Using Green Bio-Magnetic Hybrid and DFT-Based Theoretical Study

Several highly efficient and magnetically recyclable cobalt catalytic systems were prepared using magnetic chitosan and some safe and available organic compounds (Co-ligand@MNPs/Ch). The structure of these nanocomposites was confirmed by various physicochemical techniques such as FT-IR, XRD, TGA, VSM, TEM, SEM, CHNS and ICP-OES. These nano composites exhibit remarkable catalytic efficiency for Suzuki and Heck cross-coupling reactions in mild and green reaction conditions. The facile accessibility of starting materials, possible performance in air and eco-friendly conditions are merits of our catalysts. In addition, to describe and go insight to role and effect of ligands present in these catalysts, electrostatic interactions, density functional theory (DFT) model in molecular method were employed.

Palladium supported aminobenzamide modified silica coated superparamagnetic iron oxide as an applicable nanocatalyst for Heck cross-coupling reaction

An applicable palladium-based nanocatalyst was constructed through the immobilization of palladium onto 2-aminobenzamide functionalized silica coated superparamagnetic iron oxide magnetic nanoparticles. The nanocatalyst (named as Pd@ABA@SPIONs@SiO2) was characterized by several characterization methods, including scanning electron microscope (SEM), transmission electron microscopy (TEM), vibrating-sample magnetometry (VSM), energy-dispersive X-ray spectroscopy (EDS), dynamic light scattering (DLS), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), inductively coupled plasma (ICP), and X-ray photoelectron spectroscopy (XPS) analyses. Microscopy results showed that the nanoparticles are spherical in shape with 20–25 nm size. The size of the nanoparticles was confirmed by the DLS method. The superparamagnetic nature of the catalyst was confirmed by the VSM method. The successful functionalization of SPIONs@SiO2 was confirmed by FT-IR spectroscopy. The presence of palladium in the structure of the nanocatalyst was illustrated by XRD and EDS analysis. Also using XPS technique, the oxidation state of palladium in Pd@ABA@SPIONs@SiO2 was determined zero before and after the catalyst was applied in Mizoroki-Heck reaction. Several aryl halides and alkenes were reacted in the presence of the nanocatalyst and formed the corresponding products in high isolated yields. The nanocatalyst showed very good reusability and did not decrease its activity after 10 sequential runs. Density functional theory (DFT) calculation was performed to provide a mechanism for the reaction and confirmed the role of the palladium catalyst in the reaction function.

Layered double hydroxides as heterogeneous catalyst systems in the cross-coupling reactions: an overview.

Layered double hydroxides (LDHs) are recognized as two-dimensional (2D) clay materials, which comprise the interlayer anions and host layers with a positive charge (brucite-like M(OH)6 octahedral). They have been used as effective and eco-friendly heterogeneous catalytic systems in cross-coupling reactions. In this review, we try to underscore the applications of (LDHs) as an efficient and green catalyst in some important name reactions, namely Suzuki, Heck, Sonogashira, and Ullmann cross-coupling reactions leading to carbon-carbon bond formations.

Fe3O4@HcdMeen-Pd(0) Organic–Inorganic Hybrid: As a Novel Heterogeneous Nanocatalyst for Chemo and Homoselective Heck C–C Cross-Coupling Synthesis of Butyl Cinnamates

Methyl-2-(1-methyl-2′-amino-ethane)amino-1-cyclopentenedithiocarbo-xylate was supported on the modified Fe3O4 MNPs. Afterwards, Pd(OAc)2 was immobilized on the modified MNPs and, then, the nanoparticles were analyzed using FT-IR, XRD, EDS, ICP-OSE, SEM, TGA and VSM spectroscopy. The catalytic efficiency of the prepared heterogeneous Pd-NPs was successfully examined in “Heck cross coupling reaction”, involving the reaction of butyl acrylate with various aryl halides in water. The advantages of this strategy include, easy recovery and efficient reusability of the expensive Pd-NPs, obtaining high yields of the butyl cinnamate cross-coupled products, short reaction times, and being performed in water for a wide range of substrates. A novel HcdMeen-Pd(0) complex was synthesized on the surface of modified Fe3O4 MNPs and fully characterized by FT-IR, XRD, EDS, ICP-OSE, SEM, TGA and VSM spectroscopy analysis. The obtained complex was then used for Chemo And Homoselective Heck C–C cross-coupling synthesis of butyl cinnamates with in water as green solvent.

Fe-MIL-101 modified by isatin-Schiff-base-Co: a heterogeneous catalyst for C–C, C–O, C–N, and C–P cross coupling reactions

Fe-MIL-101-isatin-Schiff-base-Co was synthesized and applied as a catalyst for Ullmann-type, Buchwald–Hartwig, Hirao, Hiyama and Mizoroki–Heck cross-coupling reactions of aryl halides.

Synthesis and structural characterization of a palladium complex as an anticancer agent, and a highly efficient and reusable catalyst for the Heck coupling reaction under ultrasound irradiation: A convenient sustainable green protocol

The complex [Pd(paOH)2].2Cl (1) was synthesized by the self-assembly method with palladium chloride and pyridine-2-carbaldehyde-oxime (paOH) in aqueous acetonitrile solution under ambient conditions. Complex 1 was fully characterized by FT-IR, UV–vis and NMR spectroscopic techniques, as well as elemental analysis. The single crystal X-ray structure of complex 1 indicates that the Pd(II) ion is bonded to four nitrogen atoms from two pyridine-2-carbaldehyde-oxime ligands. The molecular geometry of the Pd(II) ion in complex 1 is distorted square-planar with a trans geometry and with two free chloride ions. Using an MTT assay, the anticancer activities of the palladium complex 1 were studied with respect to human breast cancer (MCF-7) and hepatocellular carcinoma (HePG-2) cell lines. The data obtained show that complex 1 displays strong activity towards the viability and the growth of the cancer cell lines MCF-7 and HepG2. Additionally, complex 1 exhibits excellent catalytic activity for the Heck cross-coupling reaction with water as the solvent under ultrasound irradiation. Ultrasound irradiation not only enhanced the rate and the yield of the reaction, but also promoted the in situ generation of a well-dispersed zero-valent Pd-colloidal species as the active catalyst from complex 1. Finally, the luminescence spectrum of complex 1 is discussed.