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 Nanoparticles as an Efficient and Magnetically Recoverable Catalyst for Friedel–Crafts Acylation Reaction in Solvent-Free Conditions

Application of Fe₃O₄ nanoparticles (NPs) as a robust, very efficient, and magnetically recoverable catalyst was investigated in Friedel–Crafts acylation (FCA) of ferrocene and aromatic compounds. This reaction was performed with acid chlorides in solvent-free conditions at room temperature. The catalyst was easily separated by an external magnetic field from the reaction mixture. The separated catalyst was recycled for several consecutive runs without appreciable loss of its catalytic activity.

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Nitro group reduction and Suzuki reaction catalysed by palladium supported on magnetic nanoparticles modified with carbon quantum dots generated from glycerol and urea

Glycerol and urea were used as green and cheap sources of carbon quantum dots (CQD) for modifying Fe₃O₄ nanoparticles (NPs). The obtained CQD@Fe₃O₄ NPs were used for the stabilization of palladium species and the prepared catalyst, Pd@CQD@Fe₃O₄, was characterized using various techniques. This magnetic supported palladium was applied as an efficient catalyst for the reduction of aromatic nitro compounds to primary amines at room temperature using very low palladium loading (0.008 mol%) and also for the Suzuki–Miyaura cross‐coupling reaction of aryl halides as well as challenging heteroaryl bromides and aryl diazonium salts with arylboronic acids and with potassium phenyltrifluoroborate. This magnetically recyclable catalyst was recovered and reused for seven consecutive runs in the reduction of 4‐nitrotoluene to p‐toluidine and for ten consecutive runs in the reaction of 4‐iodoanisole with phenylboronic acid with small decrease of activity. The catalyst reused in the Suzuki reaction was characterized using transmission electron microscopy, vibrating sample magnetometry and X‐ray photoelectron spectroscopy. Using experiments such as hot filtration and poisoning tests, it has been shown that the true catalyst works under homogeneous conditions according to the release–return pathway of active palladium species.     

Assembly immobilized palladium(0) on carboxymethylcellulose/Fe3O4 hybrid: An efficient tailor‐made magnetically catalyst for the Suzuki–Miyaura couplings

The Pd nanoparticles (Pd NPs) embedded on magnetically retrievable carboxymethylcellulose/Fe₃O₄ (Pd⁰@CMC/Fe₃O₄) organic/inorganic hybrid were prepared via the conventional simple process. The presence of the hydroxyl and carboxyl groups within the framework of the magnetic hybrid enables the facile preparation and stabilization of Pd NPs in this organic/inorganic hybrid. This hybrid catalyst was very effective in the Suzuki – Miyaura reaction of a variety of aryl halides with arylboronic acid to afford excellent product yields. The catalyst showed good stability and could be easily recovered with an external magnetic field and reused for several times without a significant loss in its catalytic activity. Furthermore, the Pd⁰@CMC/Fe₃O₄ hybrid catalyst was fully characterized by UV–Vis, FT–IR, XRD, SEM, EDX, TEM, XPS and TGA techniques. The hot filtration test suggests that a homogeneous mechanism is operative in Suzuki – Miyaura reaction.     

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.     

Iron oxide nanoparticles coated with green tea extract as a novel magnetite reductant and stabilizer sorbent for silver ions: Synthetic application of Fe3O4@green tea/Ag nanoparticles as magnetically separable and reusable nanocatalyst for reduction of 4‐nitrophenol

Green tea extract having many phenolic hydroxyl and carbonyl functional groups in its molecular framework can be used in the modification of Fe₃O₄ nanoparticles. Moreover, the feasibility of complexation of polyphenols with silver ions in aqueous solution can improve the surface properties and capacity of the Fe₃O₄@green tea extract nanoparticles (Fe₃O₄@GTE NPs) for sorption and reduction of silver ions. Therefore, the novel Fe₃O₄@GTE NPs nano‐sorbent has potential ability as both reducing and stabilizing agent for immobilization of silver nanoparticles to make a novel magnetic silver nanocatalyst (Fe₃O₄@GTE/Ag NPs). Inductively coupled plasma analysis, transmission and scanning electron microscopies, energy‐dispersive X‐ray and Fourier transform infrared spectroscopies, and vibrating sample magnetometry were used to characterize the catalyst. Fe₃O₄@GTE/Ag NPs shows high catalytic activity as a recyclable nanocatalyst for the reduction of 4‐nitrophenol at room temperature.     

Simple surface functionalization of magnetic nanoparticles with methotrexate-conjugated bovine serum albumin as a biocompatible drug delivery vehicle

Magnetic nanoparticles (MNPs) functionalized with methotrexate (MTX)-conjugated bovine serum albumin (BSA) as a biocompatible drug delivery vehicle were synthesized using a facile method. Characterization of the functionalized MNPs (Fe₃O₄@BSA-MTX NPs) was performed using various techniques including UV–visible spectroscopy, dynamic light scattering, vibrating sample magnetometry and X-ray diffraction. The particle size and zeta potential of Fe₃O₄@BSA-MTX NPs were 105.7 ± 3.81 nm (mean ± SD) and −18.2 mV, respectively. MTX release from Fe₃O₄@BSA-MTX NPs showed an enzyme-dependent release pattern. Hemo-biocompatibility of Fe₃O₄@BSA-MTX NPs was confirmed using hemolysis test. In addition, the cytotoxicity of functionalized MNPs and free MTX against MCF-7 cell line was investigated using MTT assay. The results of experiments revealed that the Fe₃O₄@BSA-MTX NPs as a biocompatible carrier could improve the therapeutic effect of MTX.     

Picolinimidoamide-Cu(II) complex anchored on Fe3O4@SiO2 core–shell magnetic nanoparticles: an efficient reusable catalyst for click reaction

A Cu(II) complex supported on Fe₃O₄@SiO₂ core–shell magnetic nanoparticles (MNPs) was prepared and characterized by FT-IR, XRD, SEM, EDX, TEM, VSM, TGA, and AAS analysis. The load of Cu on picolinimidoamide ligand anchored on Fe₃O₄@SiO₂ core–shell MNPs was determined as 1.22, 1.54, and 1.70 wt% using AAS, EDX and TGA analyses, respectively. Synthesized Cu(II) complex on Fe₃O₄@SiO₂ MNPs efficiently catalyzed a click reaction between alkyl halides, alkynes, and sodium azide to synthesize corresponding triazoles in high to excellent yields. The catalyst was recovered using an external magnetic field, and recycled for subsequent reactions without substantial loss of efficiency.     

A capable cobalt nano‐catalyst for the N‐formylation of various amines and its biological activity studies

The Fe₃O₄ magnetic nanoparticles (Fe₃O₄ MNPs) were modified with 1,10‐phenanthroline‐5,6‐diol and the relevant Co complex (Fe₃O₄@Phendiol@Co) synthesized as a nano‐magnetic heterogeneous catalyst to be used for the N ‐formylation of various amines at room temperature under solvent‐free conditions. Also, in order to find the better concept of the catalyst role, the N ‐formylation reaction was carried out by the use of ultrasound irradiation in the absence of the Co nano‐catalyst and the results were compared. The catalyst characterized by different methods such as the elemental analysis (CHN), ICP, FT‐IR, XRD, EDX, SEM, TEM, TG‐DTA, VSM and XPS. In addition, the antioxidant and the antibacterial activities of the Fe₃O₄@Phendiol@Co nano‐catalyst and its Phendiol ligand were in vitro screened by 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) free radical scavenging and disc diffusion methods. Results showed that they possess strong antioxidant activity (IC₅₀; 0.182 ± 0.006 mg/ml) and good antibacterial potential in comparison to standards.     

Magnetically recyclable nano copper/chitosan in O‐arylation of phenols with aryl halides

Interaction of chitosan (CS) with Fe₃O₄, followed by embedding Cu nanoparticles (NPs) on the magnetic surface through adsorption of Cu²⁺, and its reduction to Cu^o via NaBH₄, offers a reusable efficient catalyst (Fe₃O₄/CS‐Cu NPs) that is employed in cross‐coupling reactions of aryl halides with phenols, which affords the corresponding diaryl ethers, with good to excellent yields. The catalyst is completely recoverable from the reaction mixture by using an external magnet. It can be reused four times, without significant loss in its catalytic activity.     

Enhancement of Fe3O4/Au Composite Nanoparticles Catalyst in Oxidative Degradation of Methyl Orange Based on Synergistic Effect

Enhancement of Fe₃O₄ /Au nanoparticles (Fe₃O₄ /Au NPs ) catalyst was observed in the oxidative degradation of methyl orange by employing H₂O₂ as oxidant. To evaluate the catalytic activity of Fe₃O₄ /Au nanoparticles, different degradation conditions were investigated such as the amounts of catalyst, H₂O₂ concentration and pH value. Based on our data, methyl orange was degraded completely in a short time. The enhanced catalytic activity and increased oxidation rate constant may be ascribed to synergistic catalyst‐activated decomposition of H₂O₂ to •OH radical, which was one of the strong oxidizing species. Besides, Fe₃O₄ /Au nanoparticles have exhibited satisfying recycle performance for potential industrial application.     

Fe3O4–cysteamine hydrochloride magnetic nanoparticles: New,efficient and recoverable nanocatalyst for Knoevenagel condensation reaction

Fe₃O₄ magnetic nanoparticles (MNPs) were obtained using a reduction–precipitation method. These MNPs were modified with cysteamine hydrochloride. This catalyst was characterized using a number of physicochemical measurements. The Fe₃O₄–cysteamine MNPs, as an efficient and heterogeneous catalyst, were successfully used for Knoevenagel condensation under mild conditions. The activity of this nanomagnetic catalyst in the Knoevenagel condensation of aromatic aldehydes and malononitrile is described. Easy preparation of the catalyst, easy work‐up procedure, excellent yields and short reaction times are some of the advantages.     

Immobilized manganese porphyrin on functionalized magnetic nanoparticles via axial ligation: efficient and recyclable nanocatalyst for oxidation reactions

Magnetic nanoparticles (MNPs), Fe₃O₄@SiO₂, have been prepared and functionalized by 3-(chloropropyl)trimethoxysilane and then by imidazole to synthesize Fe₃O₄@SiO₂-Im. The functionalized Fe₃O₄ nanoparticles were used as a support to anchor manganese porphyrin via axial ligation. The prepared catalyst was characterized by elemental analysis, FT-IR spectroscopy, X-ray powder diffraction, UV–vis spectroscopy, and scanning electron microscopy. Application of immobilized manganese porphyrin as a heterogeneous catalyst in oxidation of alkenes and sulfides was explored. To find suitable reaction conditions, effect of different parameters such as solvent and temperature on immobilization process and also various reaction parameters (oxidant, solvent, and time) on oxidation reactions has been investigated. The results showed that the immobilized Mn-porphyrin on functionalized MNPs is an efficient and reusable catalyst for oxidation of substrates.     

Fe3O4‐SAHPG‐Pd0 nanoparticles: A ligand‐free and low Pd loading quasiheterogeneous catalyst active for mild Suzuki–Miyaura coupling and C?H activation of pyrimidine cores

This paper reports a green magnetic quasiheterogeneous efficient palladium catalyst in which Pd⁰ nanoparticles have been immobilized in self‐assembled hyperbranched polyglycidole (SAHPG)‐coated magnetic Fe₃O₄ nanoparticles (Fe₃O₄‐SAHPG‐Pd⁰). This catalyst has been used for effective ligandless Pd catalyzed Suzuki–Miyaura coupling reactions of different aryl halides with substituted boronic acids at room temperature and in aqueous media. Herein, SAHPG is used as support; it also acts as a reducing agent and stabilizer to promote the transformation of Pd^II to Pd⁰ nanoparticles. Also, this environmental friendly quasiheterogeneous catalyst is employed for the first time in the synthesis of new pyrimido[4,5‐b]indoles via oxidative addition/C? H activation reactions on the pyrimidine rings, which were obtained with higher yield and faster than when Pd(OAc)₂ was used as the catalyst. Interestingly, the above‐mentioned catalyst could be recovered in a facile manner from the reaction mixture by applying an external magnet device and recycled several times with no significant decrease in the catalytic activity.     

Palladium supported on modified magnetic nanoparticles: a phosphine‐free and heterogeneous catalyst for Suzuki and Stille reactions

An efficient magnetic nanoparticle‐supported palladium (Fe₃O₄/SiO₂‐PAP‐Pd) catalyst is reported for the Suzuki cross‐coupling and Stille reactions. This method provides a novel and much improved modification of the Suzuki and Stille coupling reactions in terms of phosphine‐free catalyst, short reaction time, clean reaction and small quantity of catalyst. Another important feature of this method is that the catalyst can be easily recovered from the reaction mixture and reused with no loss of its catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.     

Encapsulation of Pd(II) into superparamagnetic nanoparticles grafted with EDTA and their catalytic activity towards reduction of nitroarenes and Suzuki–Miyaura coupling

A robust, safe and magnetically recoverable palladium catalyst was synthesized by anchoring Pd(II) onto ethylenediaminetetraacetic acid‐coated Fe₃O₄ (Fe₃O₄@EDTA) magnetic nanoparticles. The Fe₃O₄ magnetic nanoparticle‐supported Pd(II)–EDTA complex catalyst thus obtained was characterized using scanning and transmission electron microscopies, thermogravimetric analysis, vibrating sample magnetometry, X‐ray diffraction, and inductively coupled plasma atomic emission and Fourier transform infrared spectroscopies. Fe₃O₄@EDTA–Pd(II) was screened for the Suzuki reaction and reduction of nitro compounds in water. The Pd content of the catalyst was measured to be 0.28 mmol Pd g^?1. In addition, the Fe₃O₄@EDTA–Pd catalyst can be easily separated and recovered with an external permanent magnet. The anchored solid catalyst can be recycled efficiently and reused five times with only a very slight loss of catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.     

Enantioselective synthesis of 3‐amino‐1‐aryl‐1H‐benzo[f]chromene‐2‐carbonitrile derivatives by Fe3O4@PS‐arginine as an efficient chiral magnetic nanocatalyst

A novel chiral magnetic nanocatalyst was prepared by the surface modification of Fe₃O₄ magnetic nanoparticles (MNPs) with a chloropropylsilane and further by arginine to form Fe₃O₄@propylsilan‐arginine (Fe₃O₄@PS‐Arg). After the structural confirmation of Fe₃O₄@PS‐Arg synthesized MNPs by Fourier transform‐infrared, X‐ray diffraction, field emission‐scanning electron microscopy, transmission electron microscopy, vibrating‐sample magnetometry and thermogravimetric analyses, their catalytic activity was evaluated for one‐pot enantioselective synthesis of 3‐amino‐1‐aryl‐1H‐benzo[f]chromene‐2‐carbonitrile derivatives. The results showed that in the presence of 0.07 g Fe₃O₄@PS‐Arg nanocatalyst and ethanol as solvent, the best reaction yield (96%) was obtained in the least time (5 min). Easy operation, reusability and stability, short reaction time, high reaction yields and good enantioselectivity are the major advantages of the newly synthesized nanocatalyst. Also, this study provides a novel strategy for further research and investigation on the synthesis of new reusable enantioselective catalysts and chiral compounds.     

Green synthesis of Ni‐Cu‐Zn ferrite nanoparticles using tragacanth gum and their use as an efficient catalyst for the synthesis of polyhydroquinoline derivatives

Ni_0.35Cu_0.25Zn_0.4Fe₂O₄ MNPs were synthesized using tragacanth gum as biotemplate and Metals nitrate as the metal source by the sol–gel method. The sample was characterized by powder X‐ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), vibrating sample magnetometer (VSM), scanning electron microscopy (SEM) and energy dispersive X‐ray analysis (EDX). The nanoparticles exhibit ferromagnetic behaviour at room temperature, with a saturation magnetization of 52.76 emu/g and a coercivity of 80.14 Oe. Thereupon, Ni‐Cu‐Zn ferrite nanoparticles as an efficient catalyst was used for the synthesis of polyhydroquinoline derivatives via multi‐component reactions under microwave irradiation. Simple work‐up, mild reaction conditions, short reaction times, use of an economically convenient catalyst, and excellent product yields are the advantageous features of this method. The catalyst could easily be recycled and reused few times without noticeable decrease in catalytic activity.     

Magnetically recoverable AlFe/Te nanocomposite as a new catalyst for the facile esterification reaction under neat conditions

In this work, a new Fe₃O₄/AlFe/Te nanocomposite was synthesized by a one‐step sol–gel method. The Fe₃O₄ magnetic nanoparticles (MNPs) were prepared and then mixed with aluminum telluride (Al₂Te₃) in an alkali medium to produce the desired catalyst. After characterization of the Fe₃O₄/AlFe/Te nanocomposite by SEM, TEM, EDS, XRD, and ICP analyses, it was used in the esterification reaction. This heterogeneous catalyst showed high catalytic activity in the esterification of commercially available carboxylic acids with various alcohols to produce the desired esters at high conversions under neat conditions. The Fe₃O₄/AlFe/Te nanocomposites were separated from the reaction mixture via an external magnet and re‐used 8 times without significant loss of catalytic activity.     

Environmentally friendly and highly efficient synthesis of benzoxazepine and malonamide derivatives using HPA/TPI‐Fe3O4 nanoparticles as recoverable catalyst in aqueous media

A magnetic inorganic–organic nanohybrid material (HPA/TPI‐Fe₃O₄ NPs) was produced as an efficient, highly recyclable and eco‐friendly catalyst for the one‐pot multi‐component synthesis of malonamide and 2,3,4,5‐tetrahydrobenzo[b ][1,4]oxazepine derivatives with high yields in short reaction times (25–35 min) in aqueous media at room temperature. The nanohybrid catalyst was prepared by the chemical anchoring of H₆P₂W₁₈O₆₂ onto the surface of modified Fe₃O₄ nanoparticles (NPs) with N ‐[3‐(triethoxysilyl)propyl]isonicotinamide (TPI) linker. The magnetic recoverable catalyst was easily recycled at least ten times without any loss of catalytic activity.