Cu(II) immobilized on mesoporous organosilica as an efficient and reusable nanocatalyst for one‐pot Biginelli reaction under solvent‐free conditions

Cu(II) immobilized on mesoporous organosilica nanoparticles (Cu²⁺@MSNs‐(CO₂^?)₂) has been synthesized, as a inorganic–organic nanohybrid catalyst, through a post‐grafting approach. Its characterization is carried out by Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Energy dispersive X‐ray (EDX), Thermogravimetric/differential thermal analyses (TGA‐DTA), and Nitrogen adsorption–desorption analysis. Cu²⁺@MSNs‐(CO₂^?)₂ exhibits high catalytic activity in the Biginelli reaction for the synthesis of a diverse range of 3, 4‐dihydropyrimidin‐2(1H)‐ones, under mild conditions. The anchored Cu(II) could not leach out from the surface of the mesoporous catalyst during the reaction and it has been reused several times without appreciable loss in its catalytic activity.     

Silica‐supported Cu(II)–quinoline complex: Efficient and recyclable nanocatalyst for one‐pot synthesis of benzimidazolquinoline derivatives and 2H‐indazoles

The synthesis, characterization and catalytic activity of a Cu(II) complex derived from 2‐oxoquinoline‐3‐carbaldehyde Schiff base supported on amino‐functionalized silica are reported. 3‐(1H‐Benzo[d]imidazol‐2‐yl)quinolines containing piperidine, morpholine and phenylpiperazine skeletons at the C‐2 position were formed in good to excellent yields via the one‐pot reaction of 2‐chloroquinoline‐3‐carbaldehyde, benzene‐1,2‐diamines and secondary amines in the presence of the nanocatalyst under mild conditions. Moreover, the nanocatalyst was found to be recyclable for up to seven runs without significant loss of activity. Also, a series of 2H‐indazoles were synthesized by the catalytic condensation of 2‐bromobenzaldehyde, sodium azide and primary amines.     

Synthesis and characterization of MgO nanoparticles supported on ionic liquid‐based periodic mesoporous organosilica (MgO@PMO‐IL) as a highly efficient and reusable nanocatalyst for the synthesis of novel spirooxindole‐furan derivatives

The synthesis and catalytic application of a novel MgO containing periodic mesoporous organosilica with ionic liquid framework (MgO@PMO‐IL) is described. The prepared MgO@PMO‐IL was characterized by Fourier transform‐infrared spectroscopy, N₂ adsorption/desorption, transmission electron microscopy, field emission‐scanning electron microscopy, thermogravimetric and inductively coupled plasma analyses. This nanocatalyst was successfully applied as a highly efficient and recoverable catalyst for the synthesis of novel spirooxindole‐furan derivatives via the three‐component reaction of 1,3‐dicarbonyl compounds, N‐phenacyl pyridinium salts and isatin derivatives. The products were achieved in high to excellent yields with a simple work‐up procedure and short reaction times, and the catalyst could be recovered through a simple filtration process and successfully reused seven times without any significant decrease in its efficiency.     

Introduction of Ag/CuO/MCM‐48 as an efficient catalyst for the one‐pot synthesis of novel pyran‐pyrrole hybrids

Bimetallic silver and copper incorporated mesoporous MCM‐48 (Ag/CuO/MCM‐48) was synthesized by simple wet‐impregnation method. The knowledge about its structural properties was gathered by means of Fourier transform‐infrared, energy‐dispersive X‐ray, X‐ray diffraction, field emission‐scanning electron microscopy, transmission electron microscopy and Brunauer–Emmett–Teller analyses. The catalytic activity of Ag/CuO/MCM‐48 was examined in the one‐pot three‐component reaction of 3‐(1‐methyl‐1H‐pyrrol‐2‐yl)‐3‐oxopropanenitrile, malononitrile and various aromatic aldehydes leading to novel pyran‐pyrrole hybrid derivatives in reduced reaction times (5–10 min) and excellent yields (88–97%). Application of Ag/CuO/MCM‐48 as a potent heterogeneous catalyst with good reusability up to five times, use of ethanol as an eco‐compatible medium and chromatography‐free work‐up are some crucial green aspects of this procedure.     

Me3SiCl and Et3SiI‐promoted one‐pot synthesis of 1,4‐dihydropyridine derivatives

An efficient synthesis of 1,4‐dihydropyridine derivatives has been achieved by the one‐pot cyclocondensation reaction of methyl 3‐aminocrotonate and a range of aldehydes in the presence of chlorotrimethylsilane as a promoter under solvent‐free conditions. The cyclocondenstion reaction requires a very short time and takes place in good to excellent yields. Furthermore iodotriethylsilane, generated in situ by the reaction of triethylsilane and methyl iodide in the presence of palladium chloride, has been investigated for the synthesis of 1,4‐dihydropyridine derivatives. This facile and efficient method affords high yields for the preparation of 1,4‐dihydropyridines at room temperature and short reaction times. Copyright © 2009 John Wiley & Sons, Ltd.     

An efficient and new protocol for the Heck reaction using palladium nanoparticle‐engineered dibenzo‐18‐crown‐6‐ether/MCM‐41 nanocomposite in water

Palladium nanoparticle‐incorporated mesoporous organosilica (MCM‐41‐Crown.Pd) was synthesized via the grafting of dibenzo‐18‐crown‐6‐ether moieties on the MCM‐41 surface, followed by reaction of the nanocomposite with palladium acetate and then its reduction in ethanol. The cavity of the immobilized dibenzo‐18‐crown‐6 as host material can stabilize the palladium nanoparticles effectively and prevent their aggregation and separation from the surface. The structure of the nanocomposite was characterized using various techniques. The catalytic properties of the nanocomposite in the Heck coupling reaction, one of the most useful transformations in organic synthesis, between aryl halides and olefins in water were also explored. The main advantages of the method are low cost, high yields, easy work‐up and short reaction time. The nanocatalyst can be easily separated from a reaction mixture and was successfully examined for seven runs, with a slight loss of catalytic activity.     

HAp‐encapsulated γ‐Fe2O3‐supported dual acidic heterogeneous catalyst for highly efficient one‐pot synthesis of benzoxanthenones and 3‐pyranylindoles

A novel method is reported for the synthesis of benzoxanthenone and 3‐pyranylindole derivatives via one‐pot three‐component reactions using a newly synthesized HAp‐encapsulated γ‐Fe₂O₃‐supported dual acidic heterogeneous catalyst, as a reusable and highly efficient nanocatalyst. In this protocol the use of the nanocatalyst provided a green, useful and rapid method to generate products in short reaction times (4–20 min) and in excellent yields (87–96%). The paramagnetic nature of the catalyst provided a simple, trouble‐free and facile approach for the separation of the catalyst by applying an external magnet, and it could be used in eight cycles without significant loss in catalytic efficiency.     

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.     

Surfactant‐based ionic liquids for extraction of phenolic compounds combined with rapid quantification using capillary electrophoresis

A rapid liquid phase extraction employing a novel hydrophobic surfactant‐based room temperature ionic liquid (RTIL), tetrabutylphosphonium dioctyl sulfosuccinate ([4C₄P][AOT]), coupled with capillary electrophoretic‐UV (CE‐UV) detection is developed for removal and determination of phenolic compounds. The long‐carbon‐chain RTIL used is sparingly soluble in most solvents and can be used to replace volatile organic solvents. This fact, in combination with functional‐surfactant‐anions, is proposed to reduce the interfacial energy of the two immiscible liquid phases, resulting in highly efficient extraction of analytes. Several parameters that influence the extraction efficiencies, such as extraction time, RTIL type, pH value, and ionic strength of aqueous solutions, were investigated. It was found that, under acidic conditions, most of the investigated phenols were extracted from aqueous solution into the RTIL phase within 12 min. Good linearity was observed over the concentration range of 0.1–80.0 μg/mL for all phenols investigated. The precision of this method, expressed as RSD, was determined to be within 3.4–5.3% range. The LODs (S/N = 3) of the method were in the range of 0.047–0.257 μg/mL. The proposed methodology was successfully applied to determination of phenols in real water samples.     

Sucrose chelated auto combustion synthesis of BiFeO3 nanoparticles: Magnetically recoverable catalyst for the one‐pot synthesis of polyhydroquinoline

Sucrose chelated Bismuth ferrite (BiFeO₃) nanoparticles as a novel heterogeneous catalyst was synthesized by an auto combustion route. Different calcination temperatures (150 °C, 450 °C, 550 °C, 650 °C, 750 °C and 850 °C) have been employed to obtain single phased BiFeO₃ nanoparticles. The perovskite structure formation and disappearance of organic phase (sucrose) was obtained by Fourier transform infrared spectroscopy (FT‐IR). Phase determination and structural characterization was carried out by powder X‐ray diffraction (XRD). The magnetic properties were analyzed by vibrating sample magnetometer (VSM) whereas surface area/pore volume was obtained by Brunauer–Emmett–Teller (BET). Transmission electron microscope (TEM) analyzed the particles size and morphology. Thermal stability was investigated by thermogravimetric analysis (TGA) and determination of constituent elements was carried out by X‐ray Photo‐Electron Spectroscopy (XPS). Raman spectroscopy confirmed the perovskite structure of the synthesized materials. The BiFeO₃ nanoparticles so obtained were employed as heterogeneous catalyst for the synthesis of polyhydroquinoline derivatives. All the polyhydroquinoline derivatives were characterized by Fourier transform infrared spectroscopy (FT‐IR) and Nuclear magnetic resonance spectroscopy (¹H NMR). For the very first time ever we have used BiFeO₃ as a recyclable magnetic nanocatalyst in the one‐pot four component cyclization reaction of benzaldehyde, ethylacetoacetate/methylacetoacetate, dimedone/cyclohexane‐1,3‐dione, and ammonium acetate for the synthesis of polyhydroquinoline derivatives without solvent under refluxing conditions to provide excellent yields of products. BiFeO₃ nanocatalyst (without any functionalization/surface coatings) shows easy magnetic separation, recyclability, reusability along with excellent yield of polyhydroquinoline derivatives in an economic and benign way.     

Silica‐supported Perchloric Acid Catalyzed One‐pot Synthesis of 1,4‐Dihydropyridines

An environmentally friendly and highly efficient procedure for the preparation of 1,4‐dihydropyridines by the reaction between α,β‐unsaturated aldehydes, aromatic amines and β‐keto esters in the presence of silica supported perchloric acid is described.     

Synthesis and characterization of the novel diamine‐functionalized Fe3O4@SiO2 nanocatalyst and its application for one‐pot three‐component synthesis of chromenes

Fe₃O₄@SiO₂@propyltriethoxysilane@o‐phenylendiamine as an environmentally‐benign functionalized silica‐coated magnetic organometallic nanomaterial has been synthesized and characterized by Fourier transforms infrared (FT‐IR) spectroscopy, scanning electron microscopy (SEM) images and energy dispersive X‐ray (EDX) and vibrating sample magnetometer (VSM) analyses. Then, its catalytic activity was investigated for the one‐pot three‐component condensation reaction between dimedone, malononitrile and various substituted aromatic aldehydes to afford the corresponding 2‐amino‐4H‐chromene derivatives under mild reaction conditions. This nanocatalyst can be easily recovered from the reaction mixture by using a magnet and reused for at least five times without significant decrease in catalytic activity.     

A Simple and Efficient One‐pot Synthesis of 1,4‐dihydropyridines Using Nano‐WO3‐ supported Sulfonic Acid as an Heterogeneous Catalyst under Solvent‐free Conditions

Nano‐tungsten trioxide‐supported sulfonic acid (n‐WSA) was found to be an effective heterogeneous cat‐ alyst for the one‐pot reaction of aromatic aldehydes, β‐dicarbonyl compounds and ammonium acetate to afford 1,4‐dihydropyridine derivatives in good to excellent yields. The other main advantages of the pres‐ ent method are short reaction times, simple workup, ease in purification and environmentally benign methodology. The reaction conditions were optimized employing Response Surface Method technique (Central Composite Design (CCD)) which is economically considerable because of the minimum number of experiments required to evaluate the effects of multiple parameters on the response.     

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.     

Green synthesis of polyhydroquinolines catalyzed by silica‐supported ionic liquid Si–[SbSipim][PF6]

Silica‐supported ionic liquid Si–[SbSipim][PF₆] as a catalyst was used first in the synthesis of polyhydroquinolines. The catalyst exhibits high catalytic activity in the reaction, and can be easily recovered and reused without significant loss of its activity for six runs. This green method offers several advantages, including high yield, short reaction time, simple work‐up procedure, ease of separation, and recyclability of the catalyst.     

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.     

Copper nanoparticles supported on 2‐methoxy‐1‐phenylethanone‐functionalized MCM‐41: An efficient and recyclable catalyst for one‐pot three‐component C–S coupling reaction of aryl halides with benzyl bromide and thiourea

An environmentally friendly copper‐based catalyst supported on 2‐methoxy‐1‐phenylethanone‐functionalized MCM‐41 was prepared and characterized by Fourier transform‐infrared, transmission electron microscopy, field emission‐scanning electron microscopy, X‐ray diffraction and inductively coupled plasma techniques. The catalyst was applied for the one‐pot three‐component C–S coupling reactions of aryl halides with benzyl bromide and thiourea under aerobic conditions to afford the corresponding coupled products in good yields in water. The catalyst could be recovered and recycled five times. These results prove 2‐methoxy‐1‐phenylethanone‐functionalized MCM‐41 supported Cu (II) complex was not leached during the reaction. Also it shows the correct heterogeneous nature of the catalyst.     

Copper(I) oxide nanoparticles supported on magnetic casein as a bio‐supported and magnetically recoverable catalyst for aqueous click chemistry synthesis of 1,4‐disubstituted 1,2,3‐triazoles

Copper(I) oxide nanoparticles supported on magnetic casein (Cu₂O/Casein@Fe₃O₄NPs) has been synthesized as a bio‐supported catalyst and was characterized using powder X‐ray diffraction, transmission electron microscopy, energy dispersive X‐ray and Fourier transform infrared spectroscopies, thermogravimetric analysis and inductively coupled plasma optical emission spectrometry. The catalytic activity of the synthesized catalyst was investigated in one‐pot three‐component reactions of alkyl halides, sodium azide and alkynes to prepare 1,4‐disubstituted 1,2,3‐triazoles with high yields in water. The reaction work‐up is simple and the catalyst can be magnetically separated from the reaction medium and reused in subsequent reactions.     

Chloroaluminate ionic liquid‐modified silica‐coated magnetic nanoparticles: Efficient and reusable catalyst for selective synthesis of mono‐ and bis‐dihydropyrano[3,2‐b]chromenediones

The synthesis, characterization and catalytic activity of chloroaluminate ionic liquid‐modified silica‐coated magnetic nanoparticles ([SiPrPy]AlCl₄@MNPs) are described. The prepared magnetic nanocatalyst was characterized using Fourier transform infrared spectroscopy, elemental analysis, vibrating sample magnetometry, scanning and transmission electron microscopies, X‐ray diffraction and inductively coupled plasma analysis. The results showed that the ionic liquid had been successfully immobilized onto the magnetic support, and the resulting nanoparticles exhibited high catalytic activity for the synthesis of a diverse range of dihydropyrano[3,2‐b ]chromenediones via a one‐pot, three‐component and solvent‐free reaction of aromatic aldehydes, 1,3‐diones and kojic acid. This catalytic system also showed excellent activity in the selective synthesis of mono‐ and bis‐dihydropyrano[3,2‐b ]chromenediones from dialdehydes. The procedure gave the products in excellent yields and in very short reaction times. Moreover, the catalyst could be reused eight times without loss of its catalytic activity.