β-Alanine-functionalized magnetic graphene oxide quantum dots: an efficient and recyclable heterogeneous basic catalyst for the synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-dione and 2,3-dihydroquinazolin-4(1H)-one derivatives

In this research, we report a novel synthesis of magnetic β-alanine-functionalized-graphene oxide quantum dots Fe₃O₄@GOQDs-N-(β-alanine) as a recyclable and eco-friendly heterogeneous nanocatalyst. The catalytic efficiency of these nanosheets was explored as a basic catalyst for a one-pot three-component synthesis of various 1H-pyrazolo[1,2-b]phthalazine-5,10-dione and 2,3-dihydroquinazolin-4(1H)-one derivatives. The reactions proceeded smoothly under mild and green conditions to afford the respected products in excellent yields. The structure of this newly fabricated catalyst was successfully confirmed by different analytical techniques such as Fourier transform infrared spectroscopy, X-ray diffraction, field emission-scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, vibrating sample magnetometry, and thermogravimetric analysis. The stability and recyclability of the catalyst were examined by performing the model reaction in six consecutive runs. The recovered catalyst from the first run was directly used for the next runs with no significant loss of catalytic activity.     

Effective one-pot synthesis of tetrahydrobenzo[b]pyran derivatives using nickel Schiff-base complex immobilized on iron oxide nanoparticles

Nickel Schiff-base complex immobilized on silica-coated Fe₃O₄ as a heterogeneous catalyst was designed and characterized by different techniques, such as Fourier transform infrared (FT-IR), X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), inductively coupled plasma (ICP) and vibrating sample magnetometry (VSM) thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET). The synthesized nanocatalyst has been explored as a new and efficient recyclable heterogeneous catalyst for the one-pot three-component synthesis of tetrahydrobenzo[b]pyran derivatives. The reaction proceeds smoothly to supply the respective products in excellent yields and low reaction times. The catalyst can be easily recovered by a magnetic field and reused for eight consecutive reaction cycles without significant loss of activity.     

Glycolic acid-supported cobalt ferrite-catalyzed one-pot synthesis of pyrimido[4,5-b]quinoline and indenopyrido[2,3-d]pyrimidine derivatives

Herein, one-pot synthesis of pyrimido[4,5-b]quinoline and indenopyrido[2,3-d]pyrimidine derivatives was developed by the three-component reaction of aldehydes, 6-amino-1,3-dimethyluracil, and 1,3-dicarbonyl compounds in the presence of glycolic acid-supported cobalt ferrite CoFe₂O₄@SiO₂@Si (CH₂)₃NHCOOCH₂COOH as a novel magnetic catalyst in ethanol at reflux conditions. Glycolic acid-supported cobalt ferrite was characterized via Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and vibrating sample magnetometer (VSM). Moreover, the catalyst was easily recovered with magnetic separation and recycled at least for five times without significant loss of its catalytic activity. The products were formed in excellent yields over appropriate reaction times under environmentally friendly conditions. The high efficiency and easy isolation of catalyst from products with an external permanent magnet are some of the remarkable advantages of this method.     

Thiazoline-Iridium (III) Complexes and Immobilized Nanomaterials as Selective Catalysts in N-Alkylation of Amines with Alcohols

In this research, a new series of thiazoline-iridium (III) complexes ( 4 – 7 ) derived from cysteine were prepared and fully characterized by conventional methods. The molecular structure of complex 5 was also determined by single-crystal X-ray diffraction. These complexes were evaluated as catalysts for hydrogen-borrowing reactions of amines with alcohols. In particular, complex 5 showed the best activity as catalyst. Various amines have been alkylated with alcohols affording moderate to good yield (33–99%). Moreover, the immobilized nanomaterials ( M _1,2 ) were fabricated by sonication process from the best catalyst 5 with the multi-walled carbon nanotubes (MWCNTs) and graphene oxide (GO), respectively, and characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) spectroscopy, and inductively coupled plasma-mass spectrometry (ICP-MS). The M _1,2 nanomaterials were also tested as catalysts in model catalytic reaction for N-alkylation. The M ₁ nanomaterial showed significantly higher activity than the M ₂ nanomaterial. The M ₁ catalyst was recovered by filtration and reused for four catalytic cycles with high conversion (99%, 97%, 96%, and 86%).     

Unmodified Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanostructure promoted with external magnetic field: safe,magnetically recoverable,and efficient nanocatalyst for N- and C-alkylation reactions in green conditions

Transition metal compounds have emerged as suitable catalysts for organic reactions. Magnetic compounds as soft Lewis acids can be used as catalysts for organic reactions. In this report, the Fe₃O₄ nanostructures were obtained from Fe²⁺ and Fe³⁺-salts, under an external magnetic field (EMF) without any protective agent. The X-ray photoelectron spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy tools were used to characterize these magnetic compounds. The two-dimensional (2-D, it showed nanometric size in the two dimensions, nanorod structure) Fe₃O₄ compound showed high catalytic activity and stability in N- and C-alkylation reactions. A diverse range of N- and C-alkylation products were obtained in moderate to high yield under green and mild conditions in air. Also the N- and C-alkylation products can be obtained with different selectivity and yield by exposure reactions with EMF. Results of alkylation reactions showed that the presence of Fe(II) and Fe(III) species on the surface of magnetic catalysts (phase structure of magnetic compounds) are essential as very cheap active sites. Also, morphology of magnetic catalysts had influence on their catalytic performances. After the reaction, the catalyst/product(s) separation could be easily achieved with an external magnet and more than 95% of catalyst could be recovered. The catalyst was reused at least four times without any loss of its high catalytic activity for N- and C-alkylation reactions.     

Generation of sulfate radicals by supported ruthenium catalyst for phenol oxidation in water

In this study we report the preparation of RuO₂/Fe₃O₄@nSiO₂@mSiO₂ core–shell powder mesoporous catalyst for heterogeneous oxidation of phenol by peroxymonosulfate (PMS) as oxidant. The properties of this supported catalyst were characterized by SEM–EDS (scanning electron microscopy–energy dispersive X-ray spectroscopy), XRD (powder X-ray diffraction), TEM (transmission electron microscopy), and nitrogen adsorption–desorption. It is found that using ruthenium oxide-based catalyst is highly effective in activating PMS for related sulfate radicals. The effects of catalyst loading, phenol concentration, PMS concentration, reaction temperature, and reusability of the as-prepared catalyst on phenol degradation were investigated. In RuO₂/Fe₃O₄@nSiO₂@mSiO₂ mesoporous catalyst, Oxone (PMS) was effectively activated and 100 % phenol degradation occurred in 40 min. The magnetic RuO₂/Fe₃O₄@nSiO₂@mSiO₂ catalyst was facility separated from the solution by an external magnetic field. To regenerate the deactivated catalyst and improve its catalytic properties, three different methods involving annealing in air, washing with water, and applying ultrasonics were used. The catalyst was recovered thoroughly by heat treatment.     

Titania-silica nanoparticles ensemblies assisted heterogeneous catalytic strategy for the synthesis of pharmacologically significant 2,3-diaryl-3,4-dihydroimidazo[4,5-b]indole scaffolds

Present paper elicits the multicomponent reaction (MCR) strategy assisted by titania nanoparticles hosted on silica (TiO₂.SiO₂ NPs) as heterogeneous catalyst to synthesize a series of pharmacologically significant 2,3-diaryl-3,4-dihydroimidazo[4,5-b]indole derivatives. To the best of our information, the use of isatin as one of the precursors was hitherto unreported. The decrease in reaction time, low catalyst loading, high product yield (up to 92%), and excellent reusability of the catalyst (up to 7 cycles) put this protocol under the umbrella of green chemistry tenets. Characterization of catalysts was achieved through a number of techniques viz., energy-dispersive X-ray (EDX) spectroscopy, field emission scanning electron microscopy (FESEM), powder X-ray diffraction (XRD), fourier transform infrared (FTIR) spectra of adsorbed pyridine, temperature-programmed desorption of ammonia, and porosity measurements by nitrogen adsorption (Brunauer–Emmett–Teller [BET] method). Also, the structures of synthesized compounds were corroborated on the basis of FTIR, nuclear magnetic resonance (NMR), mass, and elemental analyses data.     

Anchored Ni-dimethylglyoxime complex on Fe3O4@SiO2 core/shell nanoparticles for the clean catalytical synthesis of dicoumarols

Ni-Dimethylglyoxime complex immobilized on functionalized Fe₃O₄ was synthesized by a post-grafting way and utilized as a novel, thermally stable, recoverable, and efficient for green synthesis of dicoumarols through reaction of 4-hydroxycoumarin with various aldehydes in excellent yields and higher rate. Fe₃O₄@SiO₂-silylcyclopropyl-dimethylglyoxime-Ni superparamagnetic nanoparticles (MNP_s) were investigated by Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, vibrating sample magnetometer, and Brunauer–Emmett–Teller technique. This nanocatalyst could be conveniently recovered via the use of an external magnetic field and reused for subsequent reactions for at least 7 times without any remarkable change and decrease in catalytic activity.     

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.     

Cu(I)-anchored polyvinyl alcohol coated-magnetic nanoparticles as heterogeneous nanocatalyst in Ullmann-type C–N coupling reactions

In this paper, the preparation of a novel magnetic nanocatalyst (Fe₃O₄@PVA/CuCl) is described, which involves coating of polyvinyl alcohol (PVA) onto the surface of Fe₃O₄ nanoparticles and its subsequent coordination with CuCl catalyst. The nanocatalyst was characterized by various analytical methods, including Fourier-transform infrared, X-ray diffraction, inductively coupled plasma spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy, vibrating-sample magnetometry, and EDX elemental mapping. Moreover, the nanocatalyst was efficiently used in the N-arylation of amines via the formation of a carbon–nitrogen bond between the aryl halides and amines by Ullmann-type coupling reactions. The catalyst was sufficiently stable and can be reused for at least seven times in a model Ullmann reaction without remarkable alteration in its catalytic behavior. Heterogeneity of the catalyst was investigated by a hot filtration test.     

Magnetic NiFe2O4 nanoparticles: efficient,heterogeneous and reusable catalyst for synthesis of acetylferrocene chalcones and their anti‐tumour activity

A robust synthesis of magnetic NiFe₂O₄ nanoparticles via a hydrothermal technique was investigated. The prepared magnetic NiFe₂O₄ nanoparticles were characterized using powder X‐ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM), high‐resolution TEM, energy‐dispersive X‐ray spectroscopy, thermogravimetric analysis, infrared spectroscopy and vibrating sample magnetometry. XRD and TEM analyses confirmed the formation of single‐phase ultrafine nickel ferrite nanoparticles with highly homogeneous cubic shape and elemental composition. Moreover, the prepared magnetic NiFe₂O₄ nanoparticles were used as an efficient, cheap and eco‐friendly catalyst for the Claisen–Schmidt condensation reaction between acetylferrocene and various aldehydes (aromatic and/or heterocyclic) yielding acetylferrocene chalcones in excellent yields, with easy work‐up and reduced reaction time. The products were purified via crystallization. The structures of the produced compounds were elucidated using various spectroscopic analyses (¹H NMR, ¹³C NMR, GC–MS). The catalyst is readily recovered by simple magnetic decantation and can be recycled several times with no discernible loss of catalytic activity. Furthermore, the prepared chalcone derivatives were evaluated for their anti‐tumour activity against three human tumour cell lines, namely HCT116 (colon cancer), MCF7 (breast cancer) and HEPG2 (liver cancer), and showed a good activity against colon cancer. Copyright © 2016 John Wiley & Sons, Ltd.     

Nicotinic acid-supported cobalt ferrite-catalyzed one-pot synthesis of substituted chromeno[3,4-b]quinolines

One-pot synthesis of substituted chromeno[3,4-b]quinoline derivatives was developed by three-component reaction of aldehydes, dimedone or 1,3-cyclohexadione, and 4-aminocoumarin in the presence of nicotinic acid-supported cobalt ferrite [CoFe₂O₄@SiO₂@Si(CH₂)₃Cl@NA] as a novel magnetic catalyst in chloroform at reflux conditions. Nicotinic acid-supported cobalt ferrite was characterized via Fourier transform infrared spectroscopy, X-ray diffraction, thermal gravimetric analysis, scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, and vibrating sample magnetometry. Moreover, the catalyst could be easily recovered by magnetic separation and recycled up to five times without significant loss of its catalytic activity. The products formed in excellent yields over appropriate reaction times under environmentally friendly conditions. High efficiency and easy isolation of the catalyst from products by simple magnetic attraction are some of the considerable advantages of this procedure.     

Amelioration of H4[W12SiO40] by nanomagnetic heterogenization: For the synthesis of 1H–pyrazolo[1,2‐b]phthalazinedione derivatives

We conveniently coated silicotungstic acid (STA, H₄[W₁₂SiO₄₀]) on amino‐functionalized Si–magnetite nanoparticles, as surface functionalization of magnetic nanoparticles is an excellent way for green and efficient catalysis. The nanoparticles were structurally characterized using various techniques. The catalytic activity and recyclability of the STA–amine–Si–magnetite nanoparticles were probed through synthesis of 1H–pyrazolo[1,2‐b]phthalazinedione derivatives. The reaction proceeds smoothly to provide products in excellent yields and short reaction times. The catalyst could be readily recovered using a simple external magnet and reused several times without any significant loss in activity. Herein, we report a comparison of the activity of H₄[W₁₂SiO₄₀] as a homogeneous and heterogeneous catalyst, the latter being found to be more efficient. The findings offer effective methods for environmentally friendly synthesis of pyrazolo[1,2‐b]phthalazinedione derivatives.     

Copper coordinated-poly(α-amino acid) decorated on magnetite graphene oxide as an efficient heterogeneous magnetically recoverable catalyst for the selective synthesis of 5- and 1-substituted tetrazoles from various sources: A comparative study

In this work, poly(α-amino acid)-Cu(II) complex immobilized on magnetite graphene oxide (GO/Fe₃O₄@PAA-Cu-complex) was prepared via a multistep synthesis and employed as an efficient, heterogeneous, magnetically recyclable nanocatalyst for one-pot, three component synthesis of 5- and 1-substituted tetrazoles using different substrates including benzaldehydes, benzonitriles, and anilines in mild conditions. The different approaches were mechanically investigated and compared. The catalyst was fully characterized by Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), energy dispersive X-ray spectroscopy (EDX), inductively coupled plasma (ICP), FE-SEM and TEM analyses. The magnetic nanocatalyst could be readily separated from the reaction mixture by an external magnet and reused for several times without significant loss of catalytic activity. Also, the spectroscopic analysis revealed the stability and durability of the catalyst. Finally, the chemoselectivity of the method was investigated by the various combinations of aldehyde, nitrile, and oxime.     

Efficient synthesis of β-aminoketones catalyzed by Fe3O4@ quillaja sapogenin/Ni (II) as a novel magnetic nano-catalyst

A new nano-magnetic core–shell Fe₃O₄@quillaja sapogenin/Ni (II) was synthesized and characterized thoroughly using various tests including energy-dispersive X-ray spectroscopy (EDS), Brunauer–Emmett–Teller (BET), thermo-gravimetric analysis (TGA), high-resolution transmission electron microscopy (HR-TEM), vibrating sample magnetometer (VSM), Fourier transform infrared (FT-IR) spectroscopy, inductively coupled plasma (ICP), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The achievements demonstrated that the proposed agents were beneficial to synthesis the derivatives of β-aminoketone. Moreover, it was possible to recover the catalyst by means of simple magnetic decantation quickly. Besides, no reduction in the activity of the catalyst occurred, even though it was utilized in various reactions.     

CoNiFe2O4@Silica-SO3H nanoparticles: New recyclable magnetic nanocatalyst for the one-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones/thiones under solvent-free conditions

A useful and green synthesis of 3,4-dihydropyrimidin-2(1H)-ones/thiones derivatives were achieved by one-pot cyclocondensation between substituted aryl aldehydes, diketone/ketoester, and urea/thiourea using magnetic CoNiFe₂O₄@Silica-SO₃H nanoparticles under solvent-free condition. The choice of this approach showed essential advantages such as short reaction time, simple work-up procedure, high activity of the catalyst, high yield of the reaction products, the magnetic properties of the catalyst, and environmentally amiable conditions. In addition, the catalyst recovered and reused four times without notable loss of its activity. The magnetic CoNiFe₂O₄@Silica-SO₃H nanoparticles were described by Fourier-transform infrared spectroscopy (FT-IR), field emission scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, and vibrating sample magnetometer. The products were obtained with excellent yields (88–98%). The formation of the products was confirmed and identified with their physical properties (melting points), the FT-IR, ¹H NMR, ¹³C NMR, mass spectrometry, and the elemental analysis.     

Synthesis,characterization and application of magnetic biochar sulfonic acid as a highly efficient recyclable catalyst for preparation of spiro-pyrazolo[3,4-b]pyridines

A magnetic biochar sulfonic acid was prepared and characterized by fourier infrared spectroscopy (FT-IR), powder x-ray diffraction technology, scanning electron microscope, transmission electron microscope and vibrating sample magnetometer techniques. The prepared catalyst exhibited excellent catalytic activity for synthesis of spiro-pyrazolo[3,4-b]pyridine derivatives via one-pot three-component reaction of 1H-pyrazol-5-amine, isatin and 3-oxo-3-phenylpropanenitrile. The catalyst could be readily recovered and reused several times without an obvious decay of catalytic performance.

     

Homogeneous and heterogeneous olefin epoxidation catalyzed by a binuclear Mn(II)Mn(III) complex

The synthesis and characterization of a binuclear carboxylated bridged manganese complex containing the heptadentate ligand N,N′-bis(2-hydroxybenzyl)-N,N′-bis(2-methylpyridyl)-2-ol-1,3-propanediamine (H₃bbppnol) is reported. This complex was characterized by elemental analysis; infrared, electronic (UV–vis) and EPR spectroscopy; and conductivity measurements. The complex was immobilized on silica by either adsorption or entrapment via a sol–gel route. The obtained solids were characterized by thermogravimetric analyses (TG and DSC), UV–vis and infrared spectroscopy, and X-ray diffraction. The catalytic performance of the binuclear manganese complex in epoxidation reactions was evaluated for both homogeneous and heterogeneous systems. The catalytic investigation revealed that the complex performs well as an epoxidation catalyst for the substrates cyclohexene (26–39%) and cyclooctene (29–74%). The solids containing the immobilized complex can be recovered from the reaction medium and reused, maintaining good catalytic activity.     

Preparation and characterization of Cu supported on 2-(1H-benzo[d]imidazol-2-yl)aniline-functionalized Fe3O4 nanoparticles as a novel magnetic catalyst for Ullmann and Suzuki cross-coupling reactions

Copper supported on 2-(1H-benzo[d]imidazol-2-yl)aniline (BIA)-functionalized Fe₃O₄ nanoparticles (Cu-BIA-Si-Fe₃O₄) as a novel magnetic catalyst was designed and used for the synthesis of new products via Ullmann and Suzuki cross-coupling reactions. The Ullmann reaction was performed by mixing arylboronic acid with aniline derivatives in dimethylsulfoxide solvent. Also, diaryls were synthesized via Suzuki C–C reactions between aryl halides and phenylboronic acid in the same solvent. The prepared materials and catalyst were characterized with various analytical techniques. The Cu-BIA-Si-Fe₃O₄ catalyst demonstrated catalytic efficiency with good to excellent yields for both types of reactions in comparison with commercial palladium catalysts. Also, the catalyst could be recovered by a simple filtration and retained its activity even after several cycles.     

Preparation,characterization and application of silica‐supported palladium complex as a new and heterogeneous catalyst for Suzuki and Sonogashira reactions

An efficient heterogeneous Pd catalytic system has been developed, based on immobilization of Pd nanoparticles (PNPs) on a silica‐bonded propylamine–cyanuric–cysteine (SiO₂–pA–Cyan–Cys) substrate. The synthesized catalyst was characterized by transmission electron microscopy, scanning electron microscopy, FT‐IR, N₂ adsorption analysis (BET), TGA and inductively coupled plasma/atomic emission spectroscopy, and catalytic activity of this catalyst was investigated in the Suzuki and Sonogashira cross‐coupling reactions. The catalysts showed excellent performance in these two reactions, including various aryl halide derivatives (except aryl chloride derivatives) with phenylboronic acid and phenylacetylene under green conditions. Moreover, the catalyst was recycled for several runs without any significant loss of catalytic activity. Copyright © 2014 John Wiley & Sons, Ltd.