Terephthalic acid derived ligand‐stabilized palladium nanocomposite catalyst for Heck coupling reaction: without surface‐modified heterogeneous catalyst

A new protocol is reported for the synthesis of a heterogeneous palladium nanocomposite stabilized with a terephthalic acid‐derived ligand (N ,N ‐bis(4‐hydroxy‐3‐methoxybenzylidene)terephthalohydrazide). This is a highly insoluble ligand in common organic solvents, except dimethylformamide and dimethylsulfoxide. The resulting palladium nanocomposite acts as an efficient catalyst precursor for Mizoroki–Heck coupling reactions conducted under various reaction conditions. The spectral data suggest that the rate, yield and recycling of the catalyst are more effective for C–C coupling reactions. Copyright © 2016 John Wiley & Sons, Ltd.     

A highly stable and efficient magnetically recoverable and reusable Pd nanocatalyst in aqueous media heterogeneously catalysed Suzuki C–C cross‐coupling reactions

Surface modification of Fe₃O₄ nanoparticles with triethoxyethylcyanide groups was used for the immobilization of palladium nanoparticles to produce Fe₃O₄/Ethyl‐CN/Pd. The catalyst was characterized using Fourier transform infrared, wavelength‐dispersive X‐ray, energy‐dispersive X‐ray and X‐ray photoelectron spectroscopies, field‐emission scanning electron and transmission electron microscopies, and X‐ray diffraction, vibrating sample magnetometry and inductively coupled plasma analyses. In this fabrication, cyano groups played an important role as a capping agent. The catalytic behaviour of Fe₃O₄/Ethyl‐CN/Pd nanoparticles was measured in the Suzuki cross‐coupling reaction of various aryl halides (Ar? I, Ar? Br, Ar? Cl) with phenylboronic acid in aqueous phase at room temperature. Interestingly, the novel catalyst could be recovered in a facile manner from the reaction mixture by applying an external magnet device and recycled seven times without any significant loss in activity. Copyright © 2015 John Wiley & Sons, Ltd.     

Cross‐coupling reactions using porous multipod Cu2O microcrystals as recoverable catalyst in aqueous media

Porous multipod Cu₂O microcrystals were found to be an efficient, highly recyclable and eco‐friendly catalyst for the cross‐coupling reactions of aryl halides and terminal alkynes with high yields in aqueous media. Noteworthy, the Cu₂O catalyst can be reused for several times without significant decrease in catalytic activity.     

Silica‐coated nano‐Fe3O4‐supported iminopyridine palladium complex as an active,phosphine‐free and magnetically separable catalyst for Heck reactions

A novel magnetic nanoparticle‐supported iminopyridine palladium complex was successfully prepared by attaching palladium acetate to iminopyridine ligand‐functionalized silica‐coated nano‐Fe₃O₄. The as‐prepared catalyst was well characterized and was evaluated in Heck reactions in terms of activity and recyclability. It was found to be highly efficient for the reactions of various aryl iodides and aryl bromides having electron‐withdrawing groups with olefins under phosphine‐free and inert atmosphere‐free conditions. Moreover, the catalyst could be conveniently recovered using an external magnet, and the recyclability was influenced by the base in the Heck reaction. The catalyst could be reused at least six times with no significant loss in activity when triethylamine acted as the base.     

An efficient and recoverable palladium organocatalyst for Suzuki reaction in aqueous media

Meso‐tetrakis[4‐(methoxycarbonyl)phenyl]porphyrinatopalladium(II) as a palladium organocatalyst was synthesized and then used in aqueous media as a heterogeneous organocatalyst in Suzuki reaction. The prepared organocatalyst was characterized using UV–visible, infrared and NMR spectroscopies. It was found to be an efficient catalyst for Suzuki coupling reaction between phenylboronic acid and a broad range of aryl halides. Mild reaction conditions, water solvent as green media, and easy catalyst separation and reusability are the advantages of the presented method.     

Polymethyl methacrylate micro-spheres supported palladium: A new catalyst for Heck and Suzuki reactions

Polymethyl methacrylate (PMMA) micro-spheres, a kind of commercially available polymeric material was treated with PdCl₂ and formaldehyde giving a reagent with a palladium loading of 0.79 (wt.%). The Pd-PMMA catalyzed the highly efficient Heck and Suzuki reactions. The reactions can be performed under ligand-free conditions in an air atmosphere. The palladium catalyst is easily separated and can be reusable with negligible leaching of palladium.     

MCM‐41‐supported mercapto palladium(0) complex: an efficient and recyclable catalyst for the heterogeneous Stille coupling reaction

The Stille cross‐coupling reaction of organostannanes with aryl halides was achieved in the presence of a catalytic amount of MCM‐41‐supported mercapto palladium(0) complex (1 mol%) in DMF? H₂O (9:1) under air atmosphere in good to high yields. This MCM‐41‐supported palladium catalyst can be reused at least 10 times without any decrease in activity. Copyright © 2009 John Wiley & Sons, Ltd.     

Uniformly dispersed copper nanoparticles onto the modified magnetically recoverable nanocatalyst for aqueous synthesis of primary amides

Magnetically recoverable and environmentally friendly Cu‐based heterogeneous catalyst has been synthesized for the one‐pot conversion of aldehydes to their corresponding primary amides. The Fe₃O₄@SiO₂ nanocomposites were prepared by synthesis of Fe₃O₄ magnetic nanoparticles (MNPs) which was then coated with a silica shell via Stöber method. Bi‐functional cysteine amino acid was covalently bonded onto the siliceous shell of nanocatalyst. The Cu^II ions were then loaded onto the modified surface of nanocatalyst. Finally, uniformly dispersed copper nanoparticles were achieved by reduction of Cu^II ions with NaBH₄. Amidation reaction of aryl halides with electron‐withdrawing or electron‐donating groups and hydroxylamine hydrochloride catalyzed with Fe₃O₄@SiO₂@Cysteine‐copper (FSC‐Cu) MNPs in aqueous condition gave an excellent yield of products. The FSC‐Cu MNPs could be easily isolated from the reaction mixture with an external magnet and reused at least 8 times without significant loss in activity.     

Fe3O4-Lignin@Pd-NPs: A highly efficient,magnetically recoverable and recyclable catalyst for Mizoroki-Heck reaction under solvent-free conditions

Palladium nanoparticles ( Pd-NPs ) were synthesized under green conditions in water by chemical reduction of PdCl₂ with NaOH and supported by Fe ₃ O ₄ -Lignin . Fe ₃ O ₄ -Lignin is an organic–inorganic hybrid core-shell was synthesized by sonication of a mixture of Fe ₃ O ₄ -NPs (20 nm) and alkali lignin. The new materials Fe ₃ O ₄ -Lignin and Fe ₃ O ₄ -Lignin@Pd-NPs were characterized by PXRD, SEM and FT-IR spectroscopy. The Fe ₃ O ₄ -Lignin@Pd-NPs was further confirmed by UV–Visible spectroscopy, TEM, EDX, HRICP-AES and TGA/DTA. The average size of Pd-NPs determined from PXRD was 5–10 nm. The amount of palladium loaded on Fe ₃ O ₄ -Lignin obtained from EDX analysis was 26.63% by mass. The amount of Fe and Pd present in the catalyst obtained from HRICP-AES was 11.88 (wt. %) and 10.90 (wt. %) respectively per gram of lignin. The catalytic potential of Fe ₃ O ₄ -Lignin@Pd-NPs was evaluated in Mizoroki-Heck C-C coupling reaction. During the optimization studies of reaction between iodobenzene and n-butyl acrylate in various solvents and under solvent-free but aerobic conditions using various inorganic and organic bases, the product n-butyl 3-phenylprop-2-enoate ( 1a ) obtained was as high as 95% in highly polar solvents as short as in 10 min and 99% under solvent-free conditions in 3 min at 140 °C using n-Pr₃N as base. The scope of the above catalyst was investigated in the Mizoroki-Heck reaction of various aryl/heterocyclic halides and n-butyl acrylate/styrene under optimized solvent-less conditions. The corresponding products were obtained in high yields (73–99%). The catalyst recovered by magnetic decantation was reused for five times in the C-C coupling reaction between iodobenzene and n-butyl acrylate which yielded 90–95% of the desired product, 1a .     

Palladium nanoparticles immobilized on EDTA‐modified Fe3O4@SiO2 nanospheres as an efficient and magnetically separable catalyst for Suzuki and Sonogashira cross‐coupling reactions

In this study, a novel heterogeneous palladium catalyst was synthesized by anchoring palladium onto ethylenediaminetetraacetic acid (EDTA)‐coated Fe₃O₄@SiO₂ magnetic nanocomposite and used for the Suzuki and Sonogashira cross‐coupling reactions. The properties of the magnetic catalyst were characterized by FT‐IR, XRD, TEM, FE‐SEM, DLS EDX, XPS, N₂ adsorption‐desorption isotherm analysis, TGA, VSM, elemental analysis and the loading level of Pd in catalyst was measured to be 0.51 mmol/g by ICP. The catalyst was used in Suzuki cross‐coupling reactions of various aryl halides, including less reactive chlorobenzenes with phenylboronic acid without any additive or ligand under green conditions. Furthermore, we have reported this recyclable catalytic system for Sonogashira cross‐coupling reactions of various aryl halides (I, Br, Cl) under copper and ligand‐free conditions in the presence of DMF/H₂O (1:2/v:v) as a solvent. The magnetic catalyst could also be separated by an external magnet and reused six times without any significant loss of activity.     

MCM-41-supported bidentate phosphine palladium(0) complex as an efficient catalyst for the heterogeneous Stille reaction

A Stille coupling reaction of organostannanes with organic halides has been developed in the presence of a catalytic amount of MCM-41-supported bidentate phosphine palladium(0) complex (0.5 mol %) in DMF/H₂O (9:1) under air atmosphere in high yields. This polymeric palladium catalyst exhibits higher activity than Pd(PPh₃)₄ and can be reused at least 10 times without any decrease in activity.     

钯/聚乙烯醇纤维膜催化水相中的Heck偶联反应

通过静电纺丝和热交联技术、以聚乙烯醇( PVA)作为载体制备了一种电纺纤维膜负载型钯催化剂.利用扫描电镜(SEM)、能谱仪(EDS)和X射线光电子能谱(XPS)对其进行了表征.SEM结果显示:PdCl2的加入导致PVA纤维直径增加、形貌变差,而热交联过程可以减小纤维直径、改善纤维形貌.XPS表征则表明PVA可以还原pd...     

碳负载钯催化剂对Heck反应的催化性能

研究了钯碳催化剂对芳基卤和取代芳基卤与丙烯酸和苯乙烯的Heck芳基化反应的催化性能.结果表明:在反应温度为80℃、反应时间为8h、四丁基溴化铵(TBABr)作为溶剂和三丁胺作为碱的条件下,钯碳催化剂对不同取代芳基卤与丙烯酸和苯乙烯的Heck芳基化反应具有良好的催化性能,产物收率在80%以上.     

Click functionalization of magnetite nanoparticles: A new magnetically recoverable catalyst for the selective epoxidation of olefins

A new magnetically recoverable heterogeneous molybdenum catalyst was developed by means of a click chemistry approach. First, silica‐coated magnetite nanoparticles were functionalized using a bidentate ligand via thiol–ene click reaction of mercaptopropyl‐modified magnetite nanoparticles with acrylic acid. Then, a molybdenum complex was covalently supported on the surface of the clicked silica‐coated magnetite nanoparticles. The prepared catalyst was characterized using Fourier transform infrared and inductively coupled plasma optical emission spectroscopies, X‐ray diffraction, vibrating sample magnetometry and transmission electron microscopy. The catalytic performance of the prepared heterogeneous catalyst was investigated in the epoxidation of olefins with tert‐butyl hydroperoxide as oxidant. This catalyst could be reused for five runs without significant loss of activity and selectivity.     

Application of recoverable nanosized palladium(0) catalyst in Sonogashira reaction

In the absence of ligand, copper and amine, a recoverable nanoparticle palladium(0) catalyzed Sonogashira reaction of aryl iodides and bromides with terminal alkynes was developed. The protocol involved the use of an environmental-friendly reaction system with ethanol as the solvent, potassium carbonate as a base, and poly(vinylpyrrolidone) (PVP) supported nanosized palladium metal colloids as the catalyst. The palladium metal was recovered and recycled by a simple decantation of the reaction solution and used for eight consecutive trials without significant loss of its reactivity.     

Biosynthesis of palladium nanoparticles using Rosa canina fruit extract and their use as a heterogeneous and recyclable catalyst for Suzuki–Miyaura coupling reactions in water

A facile and green route for the synthesis of palladium nanoparticles was developed utilizing non‐toxic and renewable natural Rosa canina fruit extract as the reducing, stabilizing and capping agent, and they were applied as a heterogeneous catalyst for Suzuki coupling reactions between phenylboronic acid and a range of aryl halides containing iodo, bromo and chloro moieties in water under moderate reaction conditions. The structural investigation of the generated nanoparticles was performed with UV–visible spectroscopy, transmission electron microscopy, X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and energy‐dispersive X‐ray analysis. The method has some advantages such as high yields, efficiency, elimination of surfactant, chemical reductants, ligand and organic solvent, economic, cleaner reaction profiles, heterogeneous catalysis, simple methodology and easy workup. The catalyst can be recovered and reused seven times without any significant decrease in catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

Highly dispersed copper/ppm palladium nanoparticles as novel magnetically recoverable catalyst for Suzuki reaction under aqueous conditions at room temperature

An efficient procedure based on arginine‐modified Fe₃O₄@carbon magnetic nanoparticles (FCA MNPs) with highly dispersed copper nanoparticles (Cu NPs) and 92.8 ppm of Pd is reported for room temperature Suzuki reaction. For enhancing the activity of this Cu‐based heterogeneous catalyst, special arginine amino acid as a ligand with high content of heteroatoms was immobilized onto the Fe₃O₄@carbon MNPs to increase the electron density. Cu(II) ions were then loaded on the surface of the FCA MNPs and reduced to achieve uniformly dispersed Cu NPs. An aqueous mixture of metal hydroxides such as KOH, Ba(OH)₂, Ca(OH)₂, Mg(OH)₂ as a green, non‐toxic and basic medium was used for the Suzuki reaction at room temperature. This catalyst could also be recovered and reused with no loss of activity over six successful runs.     

A novel ternary GO@SiO2‐HPW nanocomposite as an efficient heterogeneous catalyst for the synthesis of benzazoles in aqueous media

A new solid acid catalyst, consisting of 12‐phosphotungstic heteropoly acid (HPW) supported on graphene oxide/silica nanocomposite (GO@SiO₂), has been developed via immobilizing HPW onto an amine‐functionalized GO/SiO₂ surface through coordination interaction (GO@SiO₂‐HPW). The GO@SiO₂‐HPW nanocomposite was characterized by Fourier transform infrared (FT‐IR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and powder X‐ray diffraction (XRD). The prepared nanocomposite could be dispersed homogeneously in water and further used as a heterogeneous, reusable, and efficient catalyst for the synthesis of benzimidazoles and benzothiazoles by the reaction of 1,2‐phenelynediamine or 2‐aminothiophenol with different aldehydes.     

Polyacrylonitrile fiber mat‐supported palladium catalyst for Mizoroki–Heck reaction in aqueous solution

A novel palladium catalyst immobilized on polyacrylonitrile fiber mats (Pd/PAN) was prepared by electrospinning. The catalytic activity and recyclability of the microwave‐assisted Pd/PAN fiber mats were examined for the Mizoroki–Heck cross‐coupling of aryl iodides with three different acrylates in aqueous solution. The morphology of the prepared Pd/PAN fiber mats was characterized by scanning electron microscopy. The large size of the PAN fiber mat‐supported palladium catalyst enables much easier separation from the reaction mixture by simple filtration. Density functional theory calculation indicates that the chelation energy of palladium chloride (PdCl₂) with propionitrile (model of PAN) is considerable smaller than that of PdCl₂ with water, suggesting that the stability and reactivity of the Pd/PAN fiber mats catalyst could be improved through the surface derivatization with polar functional groups. Copyright © 2011 John Wiley & Sons, Ltd.