Fe3O4@TiO2@O2PO2(CH2)NHSO3H as a novel nanomagnetic catalyst: Application to the preparation of 2‐amino‐4,6‐diphenylnicotinonitriles via anomeric‐based oxidation

A new, green and reusable nanomagnetic heterogeneous catalyst, namely Fe₃O₄@TiO₂@O₂PO₂(CH₂)NHSO₃H, was synthesized and fully characterized using suitable techniques such as infrared spectroscopy, X‐ray diffraction, scanning and transmission electron microscopies, thermogravimetry, vibrating sample magnetometry and energy‐dispersive X‐ray spectroscopy. The applicability of the constructed heterogeneous core–shell catalyst as a promoter was successfully explored for the synthesis of 2‐amino‐4,6‐diphenylnicotinonitrile derivatives upon the reaction of a good range of aromatic aldehydes, acetophenone derivatives, malononitrile and ammonium acetate. The desired products were obtained with good to high yields in short reaction times under solvent‐free conditions. The suggested mechanism offers an anomeric‐based oxidation route to the products in the final step of the synthetic pathway.     

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.     

Polyethylene Glycol‐(N‐Methylimidazolium) Hydroxide‐Grafted γ‐Fe2O3@HAp: A Novel Nanomagnetic Recyclable Basic Phase‐Transfer Catalyst for the Synthesis of Tetrahydrobenzopyran Derivatives in Aqueous Media

Polyethylene glycol‐(N‐methylimidazolium) hydroxide‐grafted hydroxyapatite encapsulated γ‐Fe₂O₃ nanoparticles, γ‐Fe₂O₃@HAp@PEG(mim)OH, were prepared and characterized by FTIR, SEM, TEM, TGA, and EDAX. This nanocomposite was applied as a novel, green, nanomagnetic, and recyclable basic phase‐transfer catalyst for the synthesis of tetrahydrobenzopyrans in high yields via the three‐component reaction of aromatic aldehydes, malononitrile, and dimedone or 1,3‐cyclohexanedione in aqueous media at ambient temperature.     

Synthesis of the first nanomagnetic particles with semicarbazide‐based acidic ionic liquid tag: an efficient catalyst for the synthesis of 3,3′‐(arylmethylene)bis(4‐hydroxycoumarin) and 1‐carbamato‐alkyl‐2‐naphthol derivatives under mild and green conditions

Semicarbazide functionalized with chlorosulfonic acid on the surface of silica‐coated magnetic nanoparticles, {Fe₃O₄@SiO₂@(CH₂)₃Semicarbazide‐SO₃H/HCl}, as a novel magnetic Brønsted acid catalyst according to the aims of green chemistry was synthesized and fully characterized using Fourier transform infrared, UV–visible and energy‐dispersive X‐ray spectroscopies, X‐ray diffraction, scanning electron, transmission electron and atomic force microscopies and thermogravimetric analysis. The capability and excellent activity of this nanoparticle catalyst were exhibited in the synthesis of two series of compounds with important biological activities, namely 3,3′‐(arylmethylene)bis(4‐hydroxycoumarin) and 1‐carbamato‐alkyl‐2‐naphthol derivatives, under mild, green and solvent‐free conditions. To the best of our knowledge, this is the first study of the synthesis and application of {Fe₃O₄@SiO₂@(CH₂)₃Semicarbazide‐SO₃H/HCl} as Brønsted acid solid magnetic nanoparticles. Consequently the present study can open up a novel and promising intuition in the sequence of logical design, synthesis and applications of task‐specific Brønsted acid magnetic nanoparticle catalyst with favourable properties as a full‐fledged efficient material for sustainable approaches. Copyright © 2016 John Wiley & Sons, Ltd.     

Cu(II) immobilized on Fe3O4–diethylenetriamine: A new magnetically recoverable catalyst for the synthesis of 2,3‐dihydroquinazolin‐4(1H)‐ones and oxidative coupling of thiols

Cu(II) immobilized on Fe₃O₄–diethylenetriamine was designed as a new, inexpensive and efficient heterogeneous catalyst for the synthesis of 2,3‐dihydroquinazolin‐4(1H )‐ones and the oxidative coupling of thiols. The structure of the nanomagnetic catalyst was comprehensively characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, vibrating sample magnetometry, thermogravimetric analysis, X‐ray diffraction and atomic absorption spectroscopy. Simple preparation of the catalyst from commercially available materials, high catalytic activity, simple operation, high yields, use of green solvents, easy magnetic separation and reusability of the catalyst with unaltered activity make our protocol a green and feasible synthetic strategy.     

Cu(II) immobilized on guanidinated epibromohydrin‐functionalized γ‐Fe2O3@TiO2 (γ‐Fe2O3@TiO2‐EG‐Cu(II)): A highly efficient magnetically separable heterogeneous nanocatalyst for one‐pot synthesis of highly substituted imidazoles

A simple, efficient and eco‐friendly procedure has been developed using Cu(II) immobilized on guanidinated epibromohydrin‐functionalized γ‐Fe₂O₃@TiO₂ (γ‐Fe₂O₃@TiO₂‐EG‐Cu(II)) for the synthesis of 2,4,5‐trisubstituted and 1,2,4,5‐tetrasubstituted imidazoles, via the condensation reactions of various aldehydes with benzil and ammonium acetate or ammonium acetate and amines, under solvent‐free conditions. High‐resolution transmission electron microscopy analysis of this catalyst clearly affirmed the formation of a γ‐Fe₂O₃ core and a TiO₂ shell, with mean sizes of about 10–20 and 5–10 nm, respectively. These data were in very good agreement with X‐ray crystallographic measurements (13 and 7 nm). Moreover, magnetization measurements revealed that both γ‐Fe₂O₃@TiO₂ and γ‐Fe₂O₃@TiO₂‐EG‐Cu(II) had superparamagnetic behaviour with saturation magnetization of 23.79 and 22.12 emu g^?1, respectively. γ‐Fe₂O₃@TiO₂‐EG‐Cu(II) was found to be a green and highly efficient nanocatalyst, which could be easily handled, recovered and reused several times without significant loss of its activity. The scope of the presented methodology is quite broad; a variety of aldehydes as well as amines have been shown to be viable substrates. A mechanism for the cyclocondensation reaction has also been proposed.     

Synthesis,characterization, and catalytic application of Fe3O4‐Si‐[CH2]3‐N=CH‐aryl for the efficient synthesis of novel poly‐substituted pyridines

Fe₃O₄ magnetic nanoparticles (MNPs) were functionalized by aminopropylsilane and reacted with aromatic aldehyde, and Fe₃O₄‐Si‐[CH₂]₃‐N=CH‐Aryl and Fe₃O₄‐Si‐(CH₂)₃‐NH‐CH₂‐Aryl MNPs were prepared as novel magnetic nanocatalysts. Fourier transform infrared (FT‐IR), X‐ray diffraction (XRD), and scanning and transmission electron microscopy (SEM and TEM) were used to identify the MNPs. The catalytic activity of the MNPs was evaluated in the one‐pot synthesis of some novel poly‐substituted pyridine derivatives.     

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.     

Novel ionic liquid supported on Fe3O4 nanoparticles as an efficient catalyst for the synthesis of new chromenes

An efficient procedure for the synthesis of new chromenes by the multicomponent reaction of aldehydes, 4‐hydroxycoumarin and 2‐hydroxynaphthalene‐1,4‐dione in the presence of an ionic liquid supported on Fe₃O₄ nanoparticles is described. The ionic liquid supported on Fe₃O₄ nanoparticles as a magnetic catalyst gives products in high yields. Significant features of this method are: short reaction times, excellent yields, green method and use of an effective catalyst that can be recovered and reused many times without loss of its catalytic activity.     

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.     

Fe3O4@vitamin B1 as a sustainable superparamagnetic heterogeneous nanocatalyst promoting green synthesis of trisubstituted 1,3‐thiazole derivatives

Fe₃O₄@vitamin B₁ was designed and prepared as an inexpensive and efficient heterogeneous nanocatalyst for the synthesis of new 1,3‐thiazol derivatives. The structure of the nanomagnetic catalyst was comprehensively characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, energy‐dispersive X‐ray spectroscopy, vibrating sample magnetometry and thermogravimetric analysis. The three‐component, one‐pot condensation of arylglyoxal monohydrate, cyclic 1,3‐dicarbonyls and thioamides in water as a green solvent was applied for the preparation of 1,3‐thiazol derivatives. Simple preparation of the catalyst from commercially available materials, high catalytic activity, simple operation, short reaction times, high yields and use of green solvent are some advantages of this protocol. The superparamagnetic nanocatalyst is magnetically separable and retains its stability after recycling for at least five consecutive runs without detectable activity loss.     

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.     

Gallic acid grafted to amine‐functionalized magnetic nanoparticles as a proficient catalyst for environmentally friendly synthesis of α‐aminonitriles

An effective approach of one‐pot catalytic Strecker reaction between aromatic aldehydes, aniline or toluidine and trimethylsilyl cyanide in the presence of amine‐functionalized Fe₃O₄@SiO₂ nanoparticles grafted with gallic acid (GA) as a powerful catalyst was developed. The fabricated reusable catalyst demonstrated high efficiency in the synthesis of α‐aminonitriles along with facile work‐up procedure. Fe₃O₄@SiO₂‐NH₂‐GA was characterized by Fourier transform‐infrared spectroscopy, scanning electron microscopy image, vibrating‐sample magnetometer curve, energy‐dispersive X‐ray analysis and thermogravimetric analysis.     

Caesium carbonate supported on hydroxyapatite‐encapsulated Ni0.5Zn0.5Fe2O4 nanocrystallites as a novel magnetically basic catalyst for the one‐pot synthesis of pyrazolo[1,2‐b]phthalazine‐5,10‐diones

A novel nanomagnetic basic catalyst of caesium carbonate supported on hydroxyapatite‐coated Ni_0.5Zn_0.5Fe₂O₄ magnetic nanoparticles (Ni_0.5Zn_0.5Fe₂O₄@HAP‐Cs₂CO₃) was prepared. This new catalyst was fully characterized using Fourier transform infrared spectroscopy, transmission and scanning electron microscopy, X‐ray diffraction and vibrating sample magnetometry techniques, and then the catalytic activity of this catalyst was investigated in the synthesis of 1H‐pyrazolo[1,2‐b]phthalazine‐5,10‐dione derivatives. Also, Ni_0.5Zn_0.5Fe₂O₄@HAP‐Cs₂CO₃ could be reused at least five times without significant loss of activity and could be recovered easily by applying an external magnet. Thus, the developed nanomagnetic catalyst is potentially useful for the green and economic production of organic compounds. Copyright © 2015 John Wiley & Sons, Ltd.     

Waste to wealth: conversion of nano‐magnetic eggshell (Fe3O4@Eggshell) to Fe3O4@Ca(HSO4)2: cheap,green and environment‐friendly solid acid catalyst

Eggshell is a hazardous waste by European Union regulations, so that discarded thousands of tons per year. To convert waste (eggshell) to wealth (catalyst), nano‐magnetic eggshell was prepared based on the nano‐Fe₃O₄, and then the eggshell was converted to Ca(HSO₄)₂ with organic acid, namely, chlorosulfonic acid. Based on the back titration, 5.18 mmol SO₄H group was loaded per gram of the nano‐structure. Using this method eggshell was converted to cheap, green and environment‐friendly solid acid catalyst. The prepared catalyst (nano‐ Fe₃O₄@Ca(HSO₄)₂) was characterized by Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), energy dispersive X‐ray spectroscopy (EDX), field emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and thermal gravimetric analysis (TGA). The activity of eggshell waste‐derived catalysts was successfully evaluated in the synthesis of value‐added products, namely indazolo[1,2‐b]‐phthalazinetrione derivatives as a benchmark multicomponent reaction. In addition, design of experiments shows that increase in amount of catalyst (and temperature), boost the reaction yield, especially with steeper slope at higher temperature.     

Catalytic application of sulfonic acid‐functionalized titana‐coated magnetic nanoparticles for the preparation of 1,8‐dioxodecahydroacridines and 2,4,6‐triarylpyridines via anomeric‐based oxidation

We have developed green, efficient and powerful protocols for the preparation of 2,4,6‐triarylpyridines and 1,8‐dioxodecahydroacridines in the presence of Fe₃O₄@TiO₂@O₂PO₂(CH₂)₂NHSO₃H as a sulfonic acid‐functionalized titana‐coated magnetic nanoparticle catalyst under mild and solvent‐free reaction conditions. These protocols furnished the desired products in short reaction times with good to high yields (20–40 min and 80–86% in the case of 2,4,6‐triarylpyridines; 15–90 min and 80–93% in the case of 1,8‐dioxodecahydroacridines). The final step of the mechanistic route in the synthesis of 2,4,6‐triarylpyridines proceeds via an anomeric‐based oxidation. Also, the nanomagnetic core–shell catalyst can be recycled and reused in both cases of the scrutinized one‐pot multicomponent reactions with high turnover number and turnover frequency.     

Fe3O4@NCs/BF0.2: A magnetic bio‐based nanocatalyst for the synthesis of 2,3‐dihydro‐1H‐perimidines

Nanocellulose (NC) materials have some unique properties, which make them attractive as organic or inorganic supports for catalytic applications. Nanocatalysts with diameters of less than 100 nm are difficult to separate from the reaction mixture, therefore, magnetic nanoparticles (MNPs) were used as catalysts to overcome this problem. Fe₃O₄@NCs/BF_0.2 as a green, bio‐based, eco‐friendly, and recyclable catalyst was synthesized and characterized using fourier‐transform infrared spectroscopy (FT‐IR), vibrating sample magnetometer (VSM), X‐ray diffraction (XRD), X‐ray fluorescence (XRF), Brunauer–Emmett–Teller (BET), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and thermal gravimetric analysis (TGA) techniques. Fe₃O₄@NCs/BF_0.2 was employed for the synthesis of 2,3‐dihydro‐1H‐perimidine derivatives via a reaction of 1,8‐diaminonaphthalene with various aldehydes at room temperature under solvent‐free conditions. The present procedure offers several advantages including a short reaction time, excellent yields, easy separation of catalyst, and environmental friendliness.     

Preparation of Fe3O4@5,10‐dihydropyrido[2,3‐b]quinoxaline‐7,8‐diol copper complex: A capable nanocatalyst for the green synthesis of 1‐substituted 1H‐tetrazoles

Fe₃O₄ magnetic nanoparticles functionalized with 5,10‐dihydropyrido[2,3‐b]quinoxaline‐7,8‐diol were synthesized as was their complex with copper as a novel nanomagnetic iron oxide catalyst via a simple and green method, and characterized using various techniques. The capability of the catalyst was evaluated in the one‐pot three‐component synthesis of different tetrazoles, which showed very good results. Mild reaction conditions, good reusability and simple magnetic work‐up make this methodology interesting for the efficient synthesis of tetrazoles.     

Synthesis and characterization of bromine source supported on magnetic Fe3O4 nanoparticles: A new,versatile and efficient magnetically separable catalyst for organic synthesis

Tribenzylammonium tribromide supported onto magnetic nanoparticles (Br₃‐TBA‐Fe₃O₄) as a bromine source was successfully synthesized and characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, X‐ray diffraction, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy and vibrating sample magnetometry. The synthesized catalyst is shown to be a versatile and highly efficient heterogeneous catalyst for the Knoevenagel condensation and synthesis of 2,3‐dihydroquinazolin‐4(1H )‐one and polyhydroquinoline derivatives. To the best of the authors' knowledge, this is the first report of the use of a bromine source immobilized on Fe₃O₄ nanoparticles as a magnetically separable catalyst for these reactions. The nanosolid catalyst can be magnetically recovered and reused readily several times without significant loss in catalytic efficiency.     

Synthesis,characterization and catalytic performance of core‐shell structure magnetic Fe3O4/P(GMA‐EGDMA)‐NH2/HPG‐COOH‐Pd catalyst

A strategy has been developed for the synthesis, characterization and catalysis of magnetic Fe₃O₄/P(GMA‐EGDMA)‐NH₂/HPG‐COOH‐Pd core‐shell structure supported catalyst. The P(GMA‐EGDMA) polymer layer was coated on the surface of hollow magnetic Fe₃O₄ microspheres through the effect of KH570. The core‐shell magnetic Fe₃O₄/P(GMA‐EGDMA) modified by ‐NH₂ could be grafted with HPG. Then, the hyperbranched glycidyl (HPG) with terminal ‐OH were modified by ‐COOH and adsorbed Pd nanoparticles. The hyperbranched polymer layer not only protected the Fe₃O₄ magnetic core from acid–base substrate corrosion, but also provided a number of functional groups as binding sites for Pd nanoparticles. The prepared catalyst was characterized by UV–vis, TEM, SEM, FTIR, TGA, ICP‐OES, BET, XRD, DLS and VSM. The catalytic tests showed that the magnetic Fe₃O₄/P(GMA‐EGDMA)‐NH₂/HPG‐COOH‐Pd catalyst had excellent catalytic performance and retained 86% catalytic efficiency after 8 consecutive cycles.