One‐pot synthesis of 1‐ and 5‐substituted 1H‐tetrazoles using 1,4‐dihydroxyanthraquinone–copper(II) supported on superparamagnetic Fe3O4@SiO2 magnetic porous nanospheres as a recyclable catalyst

An effective one‐pot, convenient process for the synthesis of 1‐ and 5‐substituted 1H‐tetrazoles from nitriles and amines is described using1,4‐dihydroxyanthraquinone–copper(II) supported on Fe₃O₄@SiO₂ magnetic porous nanospheres as a novel recyclable catalyst. The application of this catalyst allows the synthesis of a variety of tetrazoles in good to excellent yields. The preparation of the magnetic nanocatalyst with core–shell structure is presented by using nano‐Fe₃O₄ as the core, tetraethoxysilane as the silica source and poly(vinyl alcohol) as the surfactant, and then Fe₃O₄@SiO₂ was coated with 1,4‐dihydroxyanthraquinone–copper(II) nanoparticles. The new catalyst was characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, dynamic light scattering, thermogravimetric analysis, vibration sample magnetometry, X‐ray photoelectron spectroscopy, nitrogen adsorption–desorption isotherm analysis and inductively coupled plasma analysis. This new procedure offers several advantages such as short reaction times, excellent yields, operational simplicity, practicability and applicability to various substrates and absence of any tedious workup or purification. In addition, the excellent catalytic performance, thermal stability and separation of the catalyst make it a good heterogeneous system and a useful alternative to other heterogeneous catalysts. Also, the catalyst could be magnetically separated and reused six times without significant loss of catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

Design and characterization of Dendrimer of MNPs as a novel,heterogeneous and reusable nanomagnetic organometallic catalyst for one‐pot synthesis of hydroxyl naphthalene‐1,4‐dione derivatives under solvent‐free conditions

A novel super acidic magnetic nanoparticle as catalyst was successfully synthesized. The preparation of this dendrimer sulfonic acid functionalized γ‐Fe₂O₃ magnetic core‐shell silica nanoparticles as a new recoverable and heterogeneous nanocatalyst was described. The new catalyst was characterized using various techniques such as scanning electron microscopy (SEM), energy dispersive spectrum (EDS), and thermo gravimetric synthesis (TGA). Moreover, we have examined the catalytic activity of the catalyst for one‐pot, efficient and facile synthesis of 2‐hydroxy‐1,4‐naphthoquinone derivatives via a three‐component condensation reaction of 2‐hydroxynaphthalene‐1,4‐dione, aromatic aldehydes and aniline derivatives. High yields of products, short reaction times, waste‐free, mild, ambient and solvent‐free reaction conditions are advantages of this protocol. Also, the catalyst can be easily recovered by an external magnetic and reused several times without significant loss of its catalytic activity.     

Silica‐Encapsulated Pt‐Sn Intermetallic Nanoparticles: A Robust Catalytic Platform for Parahydrogen‐Induced Polarization of Gases and Liquids

Recently, a facile method for the synthesis of size‐monodisperse Pt, Pt₃Sn, and PtSn intermetallic nanoparticles (iNPs) that are confined within a thermally robust mesoporous silica (mSiO₂) shell was introduced. These nanomaterials offer improved selectivity, activity, and stability for large‐scale catalytic applications. Here we present the first study of parahydrogen‐induced polarization NMR on these Pt‐Sn catalysts. A 3000‐fold increase in the pairwise selectivity, relative to the monometallic Pt, was observed using the PtSn@mSiO₂ catalyst. The results are explained by the elimination of the three‐fold Pt sites on the Pt(111) surface. Furthermore, Pt‐Sn iNPs are shown to be a robust catalytic platform for parahydrogen‐induced polarization for in vivo magnetic resonance imaging.     

Iron promotion of V‐HMS mesoporous catalysts for ultra‐deep oxidative desulfurization

Bimetallic Fe‐V‐HMS (HMS, hexagonal mesoporous silica) catalysts with various molar ratios of iron to vanadium were synthesized using a co‐synthesis method, and investigated for oxidative desulfurization of dibenzothiophene (DBT) using tert‐butyl hydroperoxide as an oxidant. The catalysts were characterized using X‐ray diffraction, temperature‐programmed desorption of ammonia, Fourier transform infrared spectroscopy and N₂ physical adsorption–desorption techniques. The Fe‐V‐HMS catalyst with a 2:1 molar ratio of iron to vanadium exhibited the highest total acidity and the highest catalytic activity. DBT was almost completely oxidized to dibenzothiophenesulfone, a species with a higher polarity that could be subsequently adsorbed on the Fe‐V‐HMS, and therefore the Fe‐V‐HMS acts as both a catalyst and an adsorbent simultaneously. The desulfurization rate was 98.1%. A pseudo‐first‐order model was fitted to the experimental data, and the activation energy was found to be 38.79 kJ mol^?1. The encouraging performance of Fe‐V‐HMS offers the prospect of the design of a one‐pot oxidative desulfurization process without needing extraction of sulfones from fuel oil with a chemical solvent.     

Synthesis of multifunctional polymer containing Ni‐Pd NPs via thiol‐ene reaction for one‐pot cascade reactions

Recently, acid–base bifunctional catalysts have been considered due to their abilities, such as the simultaneous activation of electrophilic and nucleophilic species and their high importance in organic syntheses. However, the synthesis of acid–base catalysts is problematic due to the neutralization of acidic and basic groups. This work reports a facial approach to solve this problem via the synthesis of a novel bifunctional polymer using inexpensive materials and easy methods. In this way, at the first step, heterogeneous poly (styrene sulfonic acid‐n‐vinylimidazole) containing pentaerythritol tetra‐(3‐mercaptopropionate) (PETMP) and trimethylolpropane trimethacrylate (TMPTMA) cross‐linkers were synthesized in the pores of a mesoporous silica structure using click reaction as a novel bifunctional acid–base catalyst. After that, Ni‐Pd nanoparticles supported on poly (styrenesulfonic acid‐n‐vinylimidazole)/KIT‐6 as a novel trifunctional heterogeneous acid–base‐metal catalyst was prepared. The prepared catalysts were characterized by various techniques like FT‐IR, TGA, ICP‐AES, DRS‐UV, TEM, FE‐SEM, EDS‐Mapping, and XRD. The synthesized catalysts were efficiently used as bifunctional/trifunctional catalysts for one‐pot, deacetalization‐Knoevenagel condensation and one‐pot, three‐step and a sequential reaction containing deacetalization‐Knoevenagel condensation‐reduction reaction. It is important to note that the synthesized catalyst showing high chemo‐selectivity for the reduction of nitro group, alkenyl double bond and ester group in the presence of nitrile. Moreover, it was found that the different nanoparticles including Ni, Pd, and alloyed Ni‐Pd showing different chemo‐selectivity and catalytic activity in the reaction.     

Cooperative Acid–Base Effects with Functionalized Mesoporous Silica Nanoparticles: Applications in Carbon–Carbon Bond‐Formation Reactions

Acid–base bifunctional mesoporous silica nanoparticles (MSN) were prepared by a one‐step synthesis by co‐condensation of tetraethoxysilane (TEOS) and silanes possessing amino and/or sulfonic acid groups. Both the functionality and morphology of the particles can be controlled. The grafted functional groups were characterized by using solid‐state ²⁹Si and ¹³C cross‐polarization/magic angle spinning (CP/MAS) NMR spectroscopy, thermal analysis, and elemental analysis, whereas the structural and the morphological features of the materials were evaluated by using XRD and N₂ adsorption–desorption analyses, and SEM imaging. The catalytic activities of the mono‐ and bifunctional mesoporous hybrid materials were evaluated in carbon–carbon coupling reactions like the nitroaldol reaction and the one‐pot deacetalization–nitroaldol and deacetalization–aldol reactions. Among all the catalysts evaluated, the bifunctional sample containing amine and sulfonic acid groups (MSN–NNH₂–SO₃H) showed excellent catalytic activity, whereas the homogeneous catalysts were unable to initiate the reaction due to their mutual neutralization in solution. Therefore a cooperative acid–base activation is envisaged for the carbon–carbon coupling reactions.     

Tungstate supported mesoporous silica SBA‐15 with imidazolium framework as a hybrid nanocatalyst for selective oxidation of sulfides in the presence of hydrogen peroxide

In this work, a new heterogeneous catalyst (SBA‐15/Im/WO₄^2?) was prepared, and then its performance in the oxidation of organic sulfides was studied (using 30% H₂O₂ as green oxidant under neutral reaction conditions). This organic–inorganic hybrid mesoporous material was characterized by various techniques, such as FT‐IR, inductively coupled plasma, X‐ray powder diffraction, high‐resolution‐transmission electron microscopy, N₂ adsorption–desorption and thermogravimetric analysis. The catalyst was also applied to the selective oxidation of various sulfides. The hybrid catalyst was easily recovered, and was very stable and retained good activity for at least five successive runs without any additional activation. Moreover, there was no remarkable decrease in the activity and selectivity of the catalyst. The products could be easily isolated by just removing the solvent after filtering the catalyst. The yields of the catalytic productions through this catalyst were in the range from 75% to 97%.     

Ionic liquid‐functionalized mesoporous silica nanoparticles ([pmim]FeCl4/MSNs): Efficient nanocatalyst for solvent‐free synthesis of N,N′‐diaryl‐substituted formamidines

We report the synthesis of ionic liquid‐functionalized mesoporous silica nanoparticles ([pmim]FeCl₄/MSNs) via a method of post‐grafting on parent MSNs. This hybrid material was characterized using scanning and transmission electron microscopies, energy‐dispersive X‐ray spectroscopy, nitrogen adsorption–desorption analysis, Fourier transform infrared spectroscopy, powder X‐ray diffraction and thermal analyses. The material was utilized as an efficient heterogeneous catalyst for the synthesis of N ,N ′‐diaryl‐substituted formamidines through the reaction of triethyl orthoformate with arylamines under solvent‐free conditions. The catalyst was recovered easily and reused several times without significant loss of its catalytic activity.     

Magnetic nanoporous MCM‐41 supported ionic liquid/palladium complex: An efficient nanocatalyst with high recoverability

In this study, a novel magnetic mesoporous MCM‐41 silica supported ionic liquid/palladium complex (Fe₃O₄@MCM@IL/Pd) with core‐structure was prepared and characterized and its catalytic performance was developed under green conditions. The Fe₃O₄@MCM@IL/Pd was prepared via a post grafting method and was characterized using Fourier transform infrared spectroscopy, thermal gravimetric analysis, wide‐ and low‐angle powder X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, vibration sample magnetometer and energy‐dispersive X‐ray analyses. This was applied as an efficient and recoverable nanocatalyst for the one‐pot synthesis of pyrano[2,3‐d]pyrimidine derivatives under ultrasonic conditions. The catalyst was magnetically recovered and reused for 12 consecutive cycles without significant loss of its activity and selectivity.     

Mesoporous Core–Shell Fenton Nanocatalyst: A Mild,Operationally Simple Approach to the Synthesis of Adipic Acid

Mesoporous nanoparticles composed of γ‐Al₂O₃ cores and α‐Fe₂O₃ shells were synthesized in aqueous medium. The surface charge of γ‐Al₂O₃ helps to form the core–shell nanocrystals. The core–shell structure and formation mechanism have been investigated by wide‐angle XRD, energy‐dispersive X‐ray spectroscopy, and elemental mapping by ultrahigh‐resolution (UHR) TEM and X‐ray photoelectron spectroscopy. The N₂ adsorption–desorption isotherm of this core–shell materials, which is of type IV, is characteristic of a mesoporous material having a BET surface area of 385 m² g^?1 and an average pore size of about 3.2 nm. The SEM images revealed that the mesoporosity in this core–shell material is due to self‐aggregation of tiny spherical nanocrystals with sizes of about 15–20 nm. Diffuse‐reflectance UV/Vis spectra, elemental mapping by UHRTEM, and wide‐angle XRD patterns indicate that the materials are composed of aluminum oxide cores and iron oxide shells. These Al₂O₃@Fe₂O₃ core–shell nanoparticles act as a heterogeneous Fenton nanocatalyst in the presence of hydrogen peroxide, and show high catalytic efficiency for the one‐pot conversion of cyclohexanone to adipic acid in water. The heterogeneous nature of the catalyst was confirmed by a hot filtration test and analysis of the reaction mixture by atomic absorption spectroscopy. The kinetics of the reaction was monitored by gas chromatography and ¹H NMR spectroscopy. The new core–shell catalyst remained in a separate solid phase, which could easily be removed from the reaction mixture by simple filtration and the catalyst reused efficiently.     

Selective Functionalization of Hollow Nanospheres with Acid and Base Groups for Cascade Reactions

The inner‐surface functionalization of hollow silica spheres has rarely been reported and is still a challenging topic. Herein, we report a deacetalization–Henry cascade reaction catalyzed by dual‐functionalized mesoporous silica hollow nanospheres with basic amine groups (?NH₂) on the internal shell and carboxylic acid groups (?COOH) on the external shell. The selective functionalization has been realized by a combination of “step‐by‐step post‐grafting” and “cationic surfactant‐assisted selective etching” strategy. Compared to unisolated catalyst, the selectively isolated acidic and basic dual catalyst provides excellent catalytic performance for the deacetalization–Henry cascade reaction in terms of both activity (>99 %) and selectivity (95 %).     

Bis(4‐pyridylamino)triazine‐stabilized magnetite nanoparticles: preparation,characterization and application as a retrievable catalyst for the green synthesis of 4H‐pyran, 4H‐thiopyran and 1,4‐dihydropyridine derivatives

Synthesis of bis(4‐pyridylamino)triazine stabilized on silica‐coated nano‐Fe₃O₄ particles, and their feasibility as a reusable heterogeneous basic catalyst are reported. The catalytic performance of this novel material was studied for the green synthesis of highly functionalized 4H ‐pyran, 4H ‐thiopyran and 1,4‐dihydropyridine derivatives via one‐pot multicomponent reactions. Eco‐friendly method, high yield and purity of desired products, short reaction time along with ease of workup procedure outline the advantages of these new methodologies over earlier ones. Surface and magnetic properties of the core–shell hybrid nanoparticles were characterized via transmission and scanning electron microscopies, X‐ray diffraction, energy‐dispersive X‐ray and Fourier transform infrared spectroscopies and vibrating sample magnetometry. Copyright © 2016 John Wiley & Sons, Ltd.     

Highly dispersed palladium nanoclusters incorporated in amino‐functionalized silica spheres for the selective hydrogenation of succinic acid to γ‐butyrolactone

Highly dispersed palladium nanoclusters incorporated on amino‐functionalized silica sphere surfaces (Pd/SiO₂‐NH₂) were fabricated by a simple one‐pot synthesis utilizing 3‐(2‐aminoethylamino)propyltrimethoxysilane (AAPTS) as coordinating agent. Uniform palladium nanoclusters with an average size of 1.1 nm can be obtained during the co‐condensation of tetraethyl orthosilicate and AAPTS owing to the strong interaction between palladium species and amino groups in AAPTS. The palladium particle size can be controlled by addition of AAPTS and plays a significant role in the catalytic performance. The Pd/SiO₂‐NH₂ catalyst exhibits high catalytic activity for succinic acid hydrogenation with 100% conversion and 94% selectivity towards γ‐butyrolactone using 1,4‐dioxane as solvent at 240°C and 60 bar for 4 h. Moreover, the Pd/SiO₂‐NH₂ catalyst is robust and readily reusable without loss of its catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.     

Periodic mesoporous organosilica grafted palladium organometallic complex: efficient heterogeneous catalyst for water‐medium organic reactions

Water‐medium organic reactions were studied over periodic mesoporous silica (PMO) containing Pd(II) organometallic complex. This heterogeneous catalyst was achieved by Pd(II) compound coordinated with the PPh₂‐ligand onto the pore surface of phenylene‐bridged PMO support. This catalyst displayed ordered mesoporous channels, which ensured the high dispersion of Pd(II) active sites and the convenient diffusion of reactant molecules into the pore channels. Meanwhile, the phenyl group in the pore wall of PMO could enhance the surface hydrophobicity which promoted the adsorption of organic reactant molecules on the catalyst in aqueous environment. As a result, this elaborated catalyst exhibited comparable activity and selectivity with the corresponding PdCl₂(PPh₃)₂ homogeneous catalyst in the water‐medium organic reactions, and could be used repeatedly, showing a good potential in industrial applications. Copyright © 2010 John Wiley & Sons, Ltd.     

Preparation and characterization of a silica‐based magnetic nanocomposite and its application as a recoverable catalyst for the one‐pot multicomponent synthesis of quinazolinone derivatives

An environmentally benign magnetic silica‐based nanocomposite (Fe₃O₄/SBA‐15) as a heterogeneous nanocatalyst was prepared and characterized using Fourier transform infrared and ultraviolet–visible diffuse reflectance spectroscopies, scanning electron microscopy, X‐ray diffraction, vibrating sample magnetometry and Brunauer–Emmett–Teller multilayer nitrogen adsorption. Its catalytic activity was investigated for the one‐pot multicomponent synthesis of 2,3‐dihydroquinazolin‐4(1H)‐ones starting from isatoic anhydride, ammonium acetate and various aldehydes under mild reaction conditions and easy work‐up procedure in refluxing ethanol with good yields. The nanocatalyst can be recovered easily and reused several times without significant loss of catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.     

Encapsulating Palladium Nanoparticles Inside Mesoporous MFI Zeolite Nanocrystals for Shape‐Selective Catalysis

Pd nanoparticles were successfully encapsulated inside mesoporous silicalite‐1 nanocrystals (Pd@mnc‐S1) by a one‐pot method. The as‐synthesized Pd@mnc‐S1 with excellent stability functioned as an active and reusable heterogeneous catalyst. The unique porosity and nanostructure of silicalite‐1 crystals endowed the Pd@mnc‐S1 material general shape‐selectivity for various catalytic reactions, including selective hydrogenation, oxidation, and carbon–carbon coupling reactions.     

Preparation and characterization of Fe3O4@SiO2/APTPOSS core–shell composite nanomagnetics as a novel family of reusable catalysts and their application in the one‐pot synthesis of 1,3‐thiazolidin‐4‐one derivatives

Octakis[3‐(3‐aminopropyltriethoxysilane)propyl]octasilsesquioxane (APTPOSS) as a polyhedral oligomeric silsesquioxane derivative was prepared and used as a pioneer reagent to obtain a novel core–shell composite using magnetic iron oxide nanoparticles as the core and the inorganic–organic hybrid polyhedral oligomeric silsesquioxane as the shell. Fe₃O₄@SiO₂/APTPOSS were confirmed using Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, dynamic light scattering, thermogravimetric analysis, X‐ray diffraction and vibrating sample magnetometry. The inorganic–organic hybrid polyhedral oligomeric silsesquioxane magnetic nanoparticles were used as an efficient new heterogeneous catalyst for the one‐pot three‐component synthesis of 1,3‐thiazolidin‐4‐ones under solvent‐free conditions. Moreover, these nanoparticles could be easily separated using an external magnet and then reused several times without significant loss of catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

Green and reusable homogeneous oxidative system with ceric ammonium nitrate/[Imim‐PEG1000‐TEMPO] for efficient aerobic oxidation of alcohols and one‐pot synthesis of benzimidazoles from alcohols under ambient conditions

An efficient and reusable catalytic system for aerobic oxidation of alcohols and one‐pot synthesis of benzimidazoles from alcohols with ceric ammonium nitrate and PEG₁₀₀₀–ionic liquid‐immobilized 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) is described. This system shows excellent activity and selectivity, affording the target products with good yields. Moreover, the catalytic system can be recycled and reused without significant loss of catalytic activity after seven runs. Copyright © 2014 John Wiley & Sons, Ltd.     

Porphyrin‐based polymer‐supported palladium as an excellent and recyclable catalyst for Suzuki–Miyaura coupling reaction in water

A porphyrin‐based polymer with high surface area was synthesized using 5,10,15,20‐tetraphenylporphyrin through a one‐pot Friedel–Crafts alkylation reaction. Pd(II) was successfully supported on this polymer. This strategy provides an easy approach to produce highly stable Pd–porphyrin‐based polymer. The resulting Pd catalyst was characterized using Fourier transform infrared and X‐ray photoelectron spectroscopies, thermogravimetric analysis, scanning and transmission electron microscopies and N₂ adsorption–desorption measurements. This porphyrin‐based polymer‐supported Pd was used as a heterogeneous catalyst for Suzuki–Miyaura coupling reaction in water. The results demonstrated that this Pd catalyst indeed exhibited excellent catalytic activity and recycling performance in water, even for inactive aryl chloride substrate. A new heterogeneous strategy for catalyzing the Suzuki–Miyaura reaction in water is provided.     

An In Situ Carbonization–Replication Method to Synthesize Mesostructured WO3/C Composite as Nonprecious‐Metal Anode Catalyst in PEMFC

A meostructured WO₃/C composite with crystalline framework and high electric conductivity has been synthesized by a new in situ carbonization–replication route using the block copolymer (poly(ethylene glycol)‐block‐poly(propylene glycol)‐block‐poly(ethylene glycol)) present in situ in the pore channels of mesoporous silica template as carbon source. X‐ray diffraction, X‐ray photoelectron spectroscopy, transmission electron microscopy, thermogravimetry differential thermal analysis, and N₂ adsorption techniques were adopted for the structural characterization. Cyclic voltammetry, chronoamperometry, and single‐cell test for hydrogen electrochemical oxidation were adopted to characterize the electrochemical activities of the mesoporous WO₃/C composite. The carbon content and consequent electric conductivity of these high‐surface‐area (108–130 m² g^?1) mesostructured WO₃/C composite materials can be tuned by variation of the duration of heat treatment, and the composites exhibited high and stable electrochemical catalytic activity. The single‐cell test results indicated that the mesostructured WO₃/C composites showed clear electrochemical catalytic activity toward hydrogen oxidation at 25 °C, which makes them potential non‐precious‐metal anode catalysts in proton exchange membrane fuel cell.