Application of [Fe3O4@SiO2@(CH2)3Py]HSO4− as heterogeneous and recyclable nanocatalyst for synthesis of polyhydroquinoline derivatives

Four‐component condensation reaction of aromatic aldehydes, dimedone, ethyl acetoacetate and ammonium acetate in the presence of a catalytic amount of ionic liquid on silica‐coated Fe₃O₄ nanoparticles as a heterogeneous, recyclable and very efficient catalyst provided the corresponding polyhydroquinoline derivatives in good to excellent yields in ethanol under reflux condition. The [Fe₃O₄@SiO₂@(CH₂)₃Py]HSO₄^? catalyst was characterized using various techniques such as scanning electron microscopy, powder X‐ray diffraction, thermogravimetric analysis, vibrating sample magnetometry and Fourier transform infrared spectroscopy. Furthermore, the recovery and reuse of the catalyst were demonstrated seven times without detectable loss in activity.     

A new nano‐Fe3O4‐supported organocatalyst based on 3,4‐dihydroxypyridine: an efficient heterogeneous nanocatalyst for one‐pot synthesis of pyrazolo[3,4‐b]pyridines and pyrano[2,3‐d]pyrimidines

A simple and practical strategy for the synthesis of a novel nano‐Fe₃O₄‐supported organocatalyst system based on 3,4‐dihydroxypyridine (Fe₃O₄/Py) has been developed. The prepared catalyst was characterized using Fourier transform infrared spectroscopy, transmission and scanning electron microscopies, X‐ray diffraction, vibrating sample magnetometry and energy‐dispersive X‐ray analysis. Accordingly, the Fe₃O₄/Py nanoparticles show a superparamagnetic property with a saturation magnetization of 61 emu g^?1, indicating potential application in magnetic separation technology. Our experimental results reveal that the pyridine‐functionalized Fe₃O₄ nanoparticles are an efficient base catalyst for the domino condensation of various aromatic aldehydes, Meldrum's acid and 5‐methylpyrazol‐3‐amine under very mild reaction condition and in the presence of ethanol solvent. Moreover, the synthesized catalyst was used for one‐pot, three‐component condensation of aromatic aldehydes with barbituric acid and malononitrile to produce 7‐amino‐2,4‐dioxo‐5‐phenyl‐2,3,4,5‐tetrahydro‐1H‐pyrano[2,3‐d]pyrimidine‐6‐carbonitriles. All reactions are completed in short times and all products are obtained in good to excellent yields. Also, notably, the catalyst was reused five times without significant degradation in catalytic activity and performance. Copyright © 2016 John Wiley & Sons, Ltd.     

Amino acid ionic liquid‐based titanomagnetite nanoparticles: An efficient and green nanocatalyst for the synthesis of 1,4‐dihydropyrano[2,3‐c]pyrazoles

The amino acid ionic liquid tetrabutylammonium asparaginate (TBAAsp) was immobilized on titanomagnetite (Fe_3?xTi_xO₄) nanoparticles in a facile one‐pot process using an organosilane compound (TMSP) as spacer. The modified Fe_3?xTi_xO₄@TMSP@TBAAsp magnetic nanoparticles were characterized using Fourier transform spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, vibrating sample magnetometry and thermogravimetric analysis. The resulting analytical data clearly verified the successful immobilization of the ionic liquid on the magnetic substrate. The magnetic ionic liquid‐based nanoparticles exhibited high catalytic activity in the synthesis of 1,4‐dihydropyrano[2,3‐c]pyrazole derivatives via a one‐pot three‐component reaction under mild reaction conditions. The catalyst was easily recycled and reused for at least six runs without any considerable loss of activity.     

Ferrocene‐tagged ionic liquid stabilized on silica‐coated magnetic nanoparticles: Efficient catalyst for the synthesis of 2‐amino‐3‐cyano‐4H‐pyran derivatives under solvent‐free conditions

An advanced novel magnetic ionic liquid based on imidazolium tagged with ferrocene, a supported ionic liquid, is introduced as a recyclable heterogeneous catalyst. Catalytic activity of the novel nanocatalyst was investigated in one‐pot three‐component reactions of various aldehydes, malononitrile and 2‐naphthol for the facile synthesis of 2‐amino‐3‐cyano‐4H‐pyran derivatives under solvent‐free conditions without additional co‐catalyst or additive in air. For this purpose, we firstly synthesized and investigated 1‐(4‐ferrocenylbutyl)‐3‐methylimidazolium acetate, [FcBuMeIm][OAc], as a novel basic ferrocene‐tagged ionic liquid. This ferrocene‐tagged ionic liquid was then linked to silica‐coated nano‐Fe₃O₄ to afford a novel heterogeneous magnetic nanocatalyst, namely [Fe₃O₄@SiO₂@Im‐Fc][OAc]. The synthesized novel catalyst was characterized using ¹H NMR, ¹³C NMR, Fourier transform infrared and energy‐dispersive X‐ray spectroscopies, X‐ray diffraction, and transmission and field emission scanning electron microscopies. Combination of some unique characteristics of ferrocene and the supported ionic liquid developed the catalytic activity in a simple, efficient, green and eco‐friendly protocol. The catalyst could be reused several times without loss of activity.     

Fe3O4@Propylsilane@Histidine[HSO4‐] magnetic nanocatalysts: Synthesis,characterization and catalytic application for highly efficient synthesis of xanthene derivatives

The surface of Fe₃O₄ magnetic nanoparticles (MNPs) was modified by chloropropylsilane and histidine. The imidazole group of prepared Fe₃O₄@Propylsilane@Histidine MNPs converted to imidazolium hydrogen sulfate group and Fe₃O₄@Propylsilane@Histidine [HSO₄^‐] as a novel environmentally friendly ionic liquid/ magnetite nanoparticle was prepared, successfully. FT‐IR, XRD, SEM and TEM instruments was used to identifiy the histidine ionic liquids/magnetite nanoparticles (HILMNPs). The catalytic activity of synthesized HILMNPs was appraised for the synthesis of 9‐aryl‐1,8‐dioxooctahydroxanthene and spiro[indoline‐3,9′‐xanthene]trione derivatives. The activity of HILMNPs was much better than the other reported heterogeneous and homogeneous catalysts. Furthermore, the prepared catalyst could be separated from the reaction mixture and reused four times without any significant loss in its activity.     

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.     

The first urea‐based ionic liquid‐stabilized magnetic nanoparticles: an efficient catalyst for the synthesis of bis(indolyl)methanes and pyrano[2,3‐d]pyrimidinone derivatives

Urea‐based ionic liquid stabilized on silica‐coated Fe₃O₄ magnetic nanoparticles, {Fe₃O₄@SiO₂@(CH₂)₃‐Urea‐SO₃H/HCl}, as an unexceptionable and smooth releasing urea fertilizer in alkali soils was synthesized and fully characterized using Fourier transform infrared, UV–visible and energy‐dispersive X‐ray spectroscopies, X‐ray diffraction, scanning and transmission electron microscopies, atomic force microscopy and thermogravimetric analysis. The nanostructure catalyst as a novel, green and efficient catalyst was applied for the synthesis of bis(indolyl)methane derivatives via the condensation reaction between 2‐methylindole and aldehydes at room temperature under solvent‐free conditions. Also, pyrano[2,3‐d]pyrimidinone derivatives were prepared in the presence of the nanomagnetic urea‐based catalyst by the one‐pot three‐component condensation reaction of 1,3‐dimethylbarbituric acid, aldehydes and malononitrile under solvent‐free conditions at 60 °C. To the best of our knowledge, this is the first report of the synthesis of urea‐based ionic liquid stabilized on silica‐coated Fe₃O₄ magnetic nanoparticles. So the present work can open up a new and promising insight in the course of rational design, synthesis and applications of task‐specific fertilizer‐based nanomagnetic ionic liquids with desirable properties as unexceptionable substances for sustainable processes. Copyright © 2016 John Wiley & Sons, Ltd.     

Nano-Fe3O4–Supported,Hydrogensulfate Ionic Liquid–Catalyzed,One-Pot Synthesis of Polysubstituted Pyridines

Abstract

Anchoring 1-methyl-3-(triethoxysilylpropyl) imidazolium chloride onto silica-coated magnetic Fe₃O₄ particles afforded the corresponding supported ionic liquid. Exchanging the Cl^? anion by treating with H₂SO₄ gave Brønsted ionic liquid 1-methyl-3-(triethoxysilylpropyl) imidazolium hydrogensulfate. The synthesized catalyst was characterized by various techniques such as infrared, x-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and elemental analyses. The results indicated that the prepared catalyst had a nanostructure. The catalytic activity of the supported ionic liquid was examined in the synthesis of the polysubstituted pyridines by reaction of aromatic aldehydes with acetophenones and ammonium acetate in moderate to good yields under solvent-free conditions. The catalyst can be easily recovered by applying an external magnetic field and reused for at least seven runs without deterioration in catalytic activity.     

CuI/Fe3O4 NPs@Biimidazole IL‐KCC‐1 as a leach proof nanocatalyst for the synthesis of imidazo[1,2‐a]pyridines in aqueous medium

In the present work, an innovative leach proof nanocatalyst based on dendritic fibrous nanosilica (DFNS) modified with ionic liquid loaded Fe₃O₄ NPs and CuI salts was designed and applied for the rapid synthesis of imidazo[1,2‐a]pyridines from the reaction of phenyl acetylene, 2‐aminopyridine, and aldehydes in aqueous medium. The structure of the synthesized nanocatalyst was studied by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared (FT‐IR), flame atomic absorption spectroscopy (FAAS), energy‐dispersive X‐ray (EDX), and X‐ray diffraction (XRD), vapor–liquid–solid (VLS), and adsorption/desorption analysis (Brunauer–Emmett–Teller [BET] equation) instrumental techniques. CuI/Fe₃O₄NPs@IL‐KCC‐1 with high surface area (225 m² g^?1) and porous structure not only exhibited excellent catalytic activity in aqueous media but also, with its good stability, simply recovered by an external magnet and recycled for eight cycles without significant loss in its intrinsic activity. Higher catalytic activity of CuI/Fe₃O₄NPs@IL‐KCC‐1 is due to exceptional dendritic fibrous structure of KCC‐1 and the ionic liquid groups that perform as strong anchors to the loaded magnetic nanoparticles (MNPs) and avoid leaching them from the pore of the nanocatalyst. Green reaction media, shorter reaction times, higher yields (71–97%), easy workup, and no need to use the chromatographic column are the advantages of the reported synthetic method.     

Zinc cation supported on carrageenan magnetic nanoparticles: A novel,green and efficient catalytic system for one‐pot three‐component synthesis of quinoline derivatives

This is the first report of supporting zinc cation on ƛ‐carrageenan/Fe₃O₄ magnetic nanoparticles. The structural and magnetic properties of this hybrid (Zn²⁺/ƛ‐carrageenan/Fe₃O₄ nanoparticles) were identified using various techniques. This green and efficient catalytic system was applied in the synthesis of biologically important quinolines. The products were obtained in good to high yields (52–95%) from a one‐pot reaction procedure involving aromatic aldehydes, enolizable aldehydes and aniline derivatives. Our method has many advantages such as mild reaction conditions, easy work‐up, use of a reusable magnetic catalyst and high yields of products.     

Palladium immobilized on amidoxime‐functionalized magnetic Fe3O4 nanoparticles: a highly stable and efficient magnetically recoverable nanocatalyst for sonogashira coupling reaction

We describe the synthesis of a novel Fe₃O₄/amidoxime (AO)/Pd nanocatalyst by grafting of AO groups on Fe₃O₄ nanoparticles and subsequent deposition of Pd nanoparticles. Prior to grafting of AO, the 2‐cyanoethyl‐functionalized Fe₃O₄ nanoparticles prepared through combining 2‐cyanoethyltriethoxysilane and Fe₃O₄ were treated with hydroxylamine. The AO‐grafted Fe₃O₄ nanoparticles were then used as a platform for the deposition of Pd nanoparticles. The catalyst was characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, scanning and transmission electron microscopies, vibrating sample magnetometry, wavelength‐ and energy‐dispersive X‐ray spectroscopies and inductively coupled plasma analysis. Fe₃O₄/AO/Pd is novel phosphine‐free recyclable heterogeneous catalyst for Sonogashira reactions. 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.     

Green bio‐based synthesis of Fe2O3@SiO2‐IL/Ag hollow spheres and their catalytic utility for ultrasonic‐assisted synthesis of propargylamines and benzo[b]furans

A novel magnetic hybrid system containing nano‐magnetic Fe₂O₃ hollow spheres, silica shell, [pmim]Cl ionic liquid and silver nanoparticles was synthesized and characterized. The silver nanoparticles were prepared via biosynthesis using Achillea millefolium flower as reducing and stabilizing agent. The hybrid system was successfully used as an efficient and reusable catalyst for promoting green ultrasonic‐assisted A³ and KA² coupling reactions as well as benzo[b]furan synthesis. It was found that decoration of the magnetic core with non‐magnetic moieties decreased the maximum saturation magnetization. However, the catalyst was still superparamagnetic and could be simply separated from the reaction mixture using an external magnet. The heterogeneous nature of the catalyst was also confirmed by studying its reusability and stability and the leaching of silver. Use of aqueous media, high yields, short reaction times, broad substrate tolerance and low required amount of catalyst are the merits of this protocol.     

Green,cost‐effective and efficient procedure for Heck and Sonogashira coupling reactions using palladium nanoparticles supported on functionalized Fe3O4@SiO2 by polyvinyl alcohol as a highly active,durable and reusable catalyst

A novel heterogenized organometallic catalyst was synthesized by coordinating palladium with polyvinyl alcohol‐functionalized Fe₃O₄@SiO₂ nanospheres. This novel catalyst was characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, transmission electron microscope, field emission scanning electron microscope, dynamic light scattering, UV–vis spectroscopy, X‐ray photoelectron spectroscopy, energy dispersive X‐ray analysis, thermogravimetric analysis and inductively coupled plasma analysis. The prepared palladium nanoparticles supported on polyvinyl alcohol functionalized Fe₃O₄@SiO₂ nanoparticles were successfully applied as a magnetically recyclable catalyst in Heck and Sonogashira coupling reactions in water. They showed remarkable activity toward aryl halides (I, Br, Cl) using very low palladium loading in excellent yields and demonstrated high TONs (mmol of product per mmol of catalyst). Also, the catalyst could be magnetically separated and reused seven times without any appreciable loss of catalytic activity.     

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.     

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.     

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.     

Magnetic carbon nanotube‐supported imidazolium cation‐based ionic liquid as a highly stable nanocatalyst for the synthesis of 2‐aminothiazoles

Magnetic carbon nanotube‐supported imidazolium ionic liquid (CNT‐Fe₃O₄‐IL) was synthesized and investigated using various characterization techniques, including Fourier transform infrared and Raman spectroscopies, X‐ray diffraction, vibrating sample magnetometry, scanning and transmission electron microscopies, and thermogravimetric and differential thermal analyses. In order to synthesize the CNT‐Fe₃O₄‐IL nanocomposites, Fe₃O₄‐decorated multi‐walled CNTs were modified with 1‐methyl‐3‐(3‐trimethoxysilylpropyl)‐1H‐imidazol‐3‐ium chloride. This catalytic system was found to be a highly stable, active, reusable and solid‐phase catalyst for the synthesis of 2‐aminothiazoles via the one‐pot reaction of ketone, thiourea and N‐bromosuccinimide under mild conditions. Immobilized magnetic ionic liquid catalysis combines the advantages of ionic liquid media with magnetic solid support nanomaterials which enables the application of nanotechnology and green chemistry in chemical processes. Copyright © 2016 John Wiley & Sons, Ltd.     

Butane‐1‐sulfonic acid immobilized on magnetic Fe3O4@SiO2 nanoparticles: A novel and heterogeneous catalyst for the one‐pot synthesis of barbituric acid and pyrano[2,3‐d] pyrimidine derivatives in aqueous media

Butane‐1‐sulfonic acid immobilized on magnetic Fe₃O₄@SiO₂ nanoparticles (Fe₃O₄@SiO₂‐Sultone) was easily prepared via direct ring opening of 1,4‐butanesultone with nanomagnetic Fe₃O₄@SiO₂. The prepared reagent was characterized and used for the efficient promotion of the synthesis of barbituric acid and pyrano[2,3‐d] pyrimidine derivatives. All reactions were performed under mild and completely heterogeneous reaction conditions affording products in good to high yields. The catalyst is easily isolated from the reaction mixture by magnetic decantation and can be reused at least eight times without significant loss in activity.     

Manganese(III) Salen Complex Immobilized on Fe3O4 Magnetic Nanoparticles: The Efficient,Green and Reusable Nanocatalyst

A new Fe₃O₄ magnetic nanoparticles supported manganese salen complex was successfully prepared by attaching manganese acetates to a novel N,N′‐bis(salicylidine)ethylenediamine ligand functionalized Fe₃O₄. The as‐prepared catalyst was characterized by TGA, XRD, FTIR, VSM, and TEM. It was found to be an efficient catalyst for the synthesis of benzopyranopyrimidines in aqueous medium. High catalytic activity and ease of recovery from the reaction mixture using external magnet, and several reuse times without significant losses in performance are additional eco‐friendly attributes of this catalytic system.     

Synthesis of magnetically recyclable Fe3O4@[(EtO)3Si–L1H]/Pd(II) nanocatalyst and application in Suzuki and Heck coupling reactions

A Pd(II) Schiff base complex as an efficient and highly heterogeneous catalyst was developed by immobilization of a palladium complex on the surface of modified Fe₃O₄ magnetite nanoparticles. These surface‐modified nanoparticles were characterized using various techniques such as transmission electron microscopy, X‐ray diffraction, thermogravimetric analysis, vibrating sample magnetometry, elemental analysis and Fourier transform infrared spectroscopy. The palladium catalyst exhibited efficient catalytic activity in Suzuki and Heck coupling reactions. This method has notable advantages such as excellent chemoselectivity, mild reaction conditions, short reaction times and excellent yields. The yields of the products were in the range 85–100%. Also, the nanocatalyst can be easily recovered with a permanent magnet and reused at least five times without noticeable leaching or loss of its catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.