Palladium nanoparticles immobilized on Schiff base‐functionalized mesoporous silica as a highly efficient and magnetically recoverable nanocatalyst for Heck coupling reaction

A new magnetically recoverable nanocatalyst was prepared by functionalization of mesoporous silica (SBA‐15) with a Schiff base ligand, and then immobilization of palladium nanoparticles on it using a simple procedure. This heterogeneous catalyst was fully characterized using appropriate analyses and its catalytic efficiency was investigated in Heck reaction using iodo‐, bromo‐ and chlorobenzene derivatives and styrene, with the aim of synthesizing stilbene derivatives, a class of compounds with a variety of pharmacological properties. Some of the characteristics of this nanocatalyst include good dispersion of palladium nanoparticles on the SBA‐15 support, easy separation, catalyses the production of stilbene derivatives in a short time with excellent yields even for bromo‐ and chlorobenzene, and preservation of its catalytic activity after eight reaction cycles.     

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.     

A highly stable and efficient magnetically recoverable and reusable Pd nanocatalyst in aqueous media heterogeneously catalysed Suzuki C–C cross‐coupling reactions

Surface modification of Fe₃O₄ nanoparticles with triethoxyethylcyanide groups was used for the immobilization of palladium nanoparticles to produce Fe₃O₄/Ethyl‐CN/Pd. The catalyst was characterized using Fourier transform infrared, wavelength‐dispersive X‐ray, energy‐dispersive X‐ray and X‐ray photoelectron spectroscopies, field‐emission scanning electron and transmission electron microscopies, and X‐ray diffraction, vibrating sample magnetometry and inductively coupled plasma analyses. In this fabrication, cyano groups played an important role as a capping agent. The catalytic behaviour of Fe₃O₄/Ethyl‐CN/Pd nanoparticles was measured in the Suzuki cross‐coupling reaction of various aryl halides (Ar? I, Ar? Br, Ar? Cl) with phenylboronic acid in aqueous phase at room temperature. 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.     

Highly dispersed copper/ppm palladium nanoparticles as novel magnetically recoverable catalyst for Suzuki reaction under aqueous conditions at room temperature

An efficient procedure based on arginine‐modified Fe₃O₄@carbon magnetic nanoparticles (FCA MNPs) with highly dispersed copper nanoparticles (Cu NPs) and 92.8 ppm of Pd is reported for room temperature Suzuki reaction. For enhancing the activity of this Cu‐based heterogeneous catalyst, special arginine amino acid as a ligand with high content of heteroatoms was immobilized onto the Fe₃O₄@carbon MNPs to increase the electron density. Cu(II) ions were then loaded on the surface of the FCA MNPs and reduced to achieve uniformly dispersed Cu NPs. An aqueous mixture of metal hydroxides such as KOH, Ba(OH)₂, Ca(OH)₂, Mg(OH)₂ as a green, non‐toxic and basic medium was used for the Suzuki reaction at room temperature. This catalyst could also be recovered and reused with no loss of activity over six successful runs.     

Fe3O4-Lignin@Pd-NPs: A highly efficient,magnetically recoverable and recyclable catalyst for Mizoroki-Heck reaction under solvent-free conditions

Palladium nanoparticles ( Pd-NPs ) were synthesized under green conditions in water by chemical reduction of PdCl₂ with NaOH and supported by Fe ₃ O ₄ -Lignin . Fe ₃ O ₄ -Lignin is an organic–inorganic hybrid core-shell was synthesized by sonication of a mixture of Fe ₃ O ₄ -NPs (20 nm) and alkali lignin. The new materials Fe ₃ O ₄ -Lignin and Fe ₃ O ₄ -Lignin@Pd-NPs were characterized by PXRD, SEM and FT-IR spectroscopy. The Fe ₃ O ₄ -Lignin@Pd-NPs was further confirmed by UV–Visible spectroscopy, TEM, EDX, HRICP-AES and TGA/DTA. The average size of Pd-NPs determined from PXRD was 5–10 nm. The amount of palladium loaded on Fe ₃ O ₄ -Lignin obtained from EDX analysis was 26.63% by mass. The amount of Fe and Pd present in the catalyst obtained from HRICP-AES was 11.88 (wt. %) and 10.90 (wt. %) respectively per gram of lignin. The catalytic potential of Fe ₃ O ₄ -Lignin@Pd-NPs was evaluated in Mizoroki-Heck C-C coupling reaction. During the optimization studies of reaction between iodobenzene and n-butyl acrylate in various solvents and under solvent-free but aerobic conditions using various inorganic and organic bases, the product n-butyl 3-phenylprop-2-enoate ( 1a ) obtained was as high as 95% in highly polar solvents as short as in 10 min and 99% under solvent-free conditions in 3 min at 140 °C using n-Pr₃N as base. The scope of the above catalyst was investigated in the Mizoroki-Heck reaction of various aryl/heterocyclic halides and n-butyl acrylate/styrene under optimized solvent-less conditions. The corresponding products were obtained in high yields (73–99%). The catalyst recovered by magnetic decantation was reused for five times in the C-C coupling reaction between iodobenzene and n-butyl acrylate which yielded 90–95% of the desired product, 1a .     

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.     

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.     

Cyclopropanation of diazoesters with styrene derivatives catalyzed by magnetically recoverable copper-plated iron nanoparticles

Simple bare copper-plated iron nanoparticles catalyzed the cyclopropanation of diazoesters with styrene derivatives. The reaction proceeded smoothly and provided the desired products in moderate to good yields, with selectivity for the trans isomer in neat conditions. The reaction scope was explored and di or tri-substituted cyclopropanes were synthesized. The catalysts could be magnetically separated and reusable up to five times. It was also characterized by TEM, XPS, and ICP-MS. A gram-scale reaction was performed with a yield of 72%.     

Mild and eco‐friendly chemoselective acylation of amines in aqueous medium using a green,superparamagnetic, recoverable nanocatalyst

Copper‐grafted guanidine acetic acid‐modified magnetite nanoparticles (Fe₃O₄@GAA‐Cu(II)) as a green, superparamagnetic and recoverable nanocatalyst is found to promote quantitative N ‐acylation of various amines in a very short time with an equimolar amount of thioacetic acid in water at room temperature. This method is found to be highly selective for amines and not sensitive to other functional groups. Mild reaction condition, high selectivity, efficiency, simple workup and excellent yields are some of the major advantages of the procedure.     

Solvent free synthesis of ynones using magnetically recoverable Copper-ferrite nanoparticles

A general and efficient biogenic CuFe₂O₄ MNP’s catalyzed synthesis of ynones has been reported for the first time. The reaction occurs in solvent free conditions without the use of any harsh conditions. The average diameter of the nanoparticles was found to be 13.07 nm. The advantages of the protocol include heterogeneous catalysis, easy recyclability of the catalyst and short reaction time.     

Copper immobilized onto polymer‐coated magnetic nanoparticles as recoverable catalyst for ‘click’ reaction

Copper supported on polymer‐coated magnetic nanoparticles was designed and synthesized as a separable heterogeneous catalyst. The catalyst was fully characterized using several techniques such as Fourier transform infrared and energy‐dispersive X‐ray spectroscopies, scanning and transmission electron microscopies, X‐ray diffraction, vibrating sample magnetometry, thermogravimetric analysis and inductively coupled plasma atomic emission spectrometry. All results showed that copper was successfully supported on the polymer‐coated magnetic nanoparticles. Also, results showed that the synthesized material can be used as an efficient catalyst for the preparation of a series of 1,4‐disubstituted 1,2,3‐triazoles from corresponding halides, alkynes and sodium azide. The catalyst can be easily isolated from the reaction solution by applying an external magnet and reused for nine runs without any significant loss of catalytic activity.     

A new magnetically recoverable heterogeneous palladium catalyst for phosphonation reactions in aqueous micellar solution

A new heterogeneous palladium complex of 2‐aminothiophenol supported on nanomagnetic γ‐Fe₂O₃ was synthesized and characterized using various methods. The catalyst was used as a magnetically recoverable heterogeneous palladium catalyst for phosphonation reactions via C ? P bond formation. Using this method, a wide range of electrophilic benzenes was coupled successfully with phosphite esters (triethyl/tri‐isopropyl/triphenylphosphite and diethyl/di‐isopropyl/diphenylphosphite) in aqueous micellar solution to generate the corresponding arylphosphonates in good to high yields. The catalyst was separated using an external magnet and reused for six consecutive cycles without any significant loss of its reactivity. Copyright © 2015 John Wiley & Sons, Ltd.     

Silver nanoparticles immobilized onto poly(4‐vinylpyridine)‐functionalized magnetic nanoparticles: A robust magnetically recyclable catalyst for oxidant‐free alcohol dehydrogenation

A heterogeneous and recyclable catalyst with a high loading of silver nanoparticles was synthesized via the silver nanoparticles being supported onto the surface of magnetic nanoparticles coated with poly(4‐vinylpyridine). The synthesized catalyst was used in the dehydrogenation of alcohols to corresponding carbonyl compounds. A broad diversity of alcohols was converted into their corresponding carbonyl compounds in excellent yields. The catalyst was easily recovered by applying an external magnetic field and reused for seven reaction cycles without considerable loss of activity. The catalyst was fully characterized using various techniques.     

Copper oxide supported on magnetic nanoparticles (CuO@γ‐Fe2O3): An efficient and magnetically separable nanocatalyst for addition of amines to carbodiimides towards synthesis of substituted guanidines

Copper oxide supported on magnetic nanoparticles was used as a green magnetic nanocatalyst for hydroamination of carbodiimides towards the synthesis of guanidines. Easy preparation and separation, low cost, non‐sensitivity to moisture and reusability of the catalyst along with diversity and high yield of products are significant features of this method.     

Liposomes as nanoreactors for copper nanoparticles synthesis

Copper nanoparticles 3.8 –10.9 nm in size were synthesized in solid-phase membrane liposomes by a facile method of copper sulfate reduction with hydrazine. A change in the excess of hydrazine leads to the controlled formation of either Cu₂O or Cu⁰ nanoparticles.     

Sulfamic acid immobilized on amino‐functionalized magnetic nanoparticles: A new and active magnetically recoverable catalyst for the synthesis of N‐heterocyclic compounds

Sulfamic acid immobilized on amino‐functionalized magnetic nanoparticles (MNPs/DETA‐SA) was successfully fabricated and characterized using various techniques. Diameters of approximately 15 nm for the MNPs/DETA‐SA were observed from scanning electron microscopy images. The as‐fabricated nanocomposite was applied as an efficient and magnetically reusable catalyst for the synthesis of 2,3‐dihydroquinazoline‐4(1H)‐one and polyhydroquinoline derivatives. All products were obtained in good to excellent yields. Recovery tests confirm that the catalyst can be readily recovered using an external magnet and reused many times without significant loss of its catalytic activity.     

Heterogeneously catalyzed synthesis of primary amides directly from primary alcohols and aqueous ammonia

In the presence of a manganese oxide based octahedral molecular sieve (OMS-2), a range of primary amides could be synthesized directly from primary alcohols and ammonia. The observed catalysis was heterogeneous, and the recovered catalyst could be reused many times without an appreciable loss of its catalytic performance.     

Threonine stabilizer‐controlled well‐dispersed small palladium nanoparticles on modified magnetic nanocatalyst for Heck cross‐coupling process in water

We report the synthesis of magnetically separable Fe₃O₄@Silica‐Threonine‐Pd⁰ magnetic nanoparticles with a core–shell structure. After synthesis of Fe₃O₄@Silica, threonine as an efficient stabilizer/ligand was bonded to the surface of Fe₃O₄@Silica. Then, palladium nanoparticles were generated on the threonine‐modified catalyst. The threonine stabilizer helps to generate palladium nanoparticles of small size (less than 4 nm) with high dispersity and uniformity. Magnetically separable Fe₃O₄@Silica‐Threonine‐Pd⁰ nanocatalyst was fully characterized using various techniques. This nanocatalyst efficiently catalysed the Heck cross‐coupling reaction of a variety of substrates in water medium as a green, safe and inexpensive solvent at 80°C. The Fe₃O₄@Silica‐Threonine‐Pd⁰ catalyst was used for at least eight successful consecutive runs with palladium leaching of only 0.05%.     

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.     

Fe3O4/SiO2 nanoparticles: an efficient and magnetically recoverable nanocatalyst for the one-pot multicomponent synthesis of diazepines

In this research, a new protocol for the one-pot multicomponent synthesis of diazepine derivatives using a 1,2-diamine, a linear or cyclic ketone, and an isocyanide in the presence of a catalytic amount of silica-supported iron oxide (Fe₃O₄/SiO₂) nanoparticles at ambient temperature in excellent yields is described.