Preparation,characterization and use of new lignocellulose-based bio nanocomposite as a heterogeneous catalyst for sustainable synthesis of pyrimido benzazoles

A sustainable combinatorial synthesis of densely substituted pyrimido [1,2-b] benzazole derivatives in water under microwave irradiation was performed using a new lignocellulose-based bio nanocomposite (BNC) as heterogeneous catalyst. The lignocellulosic waste peanut shells (LCWPS) were turned into a value-added product, a new BNC PS/ZnO, which was prepared via in situ hydrothermal synthesis. The as-prepared BNC was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction spectrum. PS/ZnO has been successfully used in a sustainable catalytic method for the synthesis of pyrimido [1, 2-b] benzazole derivatives in water under microwave irradiation. The time of this reaction was significantly reduced. This catalytic system has a very high turnover number (TON?～?10³) and turnover frequency (TOF?～?10^5?h^?1). This paper presents the benefit of sustainable management of LCWPS, a bio-sourced polymeric carbohydrate for production of new nanocatalyst.     

Co-salen functionalized on graphene as an efficient heterogeneous catalyst for cyclohexene oxidation

Co-salen functionalized on graphene with an average pore size of 27.7 nm as a heterogeneous catalyst exhibited good catalytic activity and recyclability in cyclohexene oxidation.     

Butane‐1‐sulfonic acid immobilized on magnetic Fe3O4@SiO2 nanoparticles: A novel and heterogeneous catalyst for the one‐pot synthesis of barbituric acid and pyrano[2,3‐d] pyrimidine derivatives in aqueous media

Butane‐1‐sulfonic acid immobilized on magnetic Fe₃O₄@SiO₂ nanoparticles (Fe₃O₄@SiO₂‐Sultone) was easily prepared via direct ring opening of 1,4‐butanesultone with nanomagnetic Fe₃O₄@SiO₂. The prepared reagent was characterized and used for the efficient promotion of the synthesis of barbituric acid and pyrano[2,3‐d] pyrimidine derivatives. All reactions were performed under mild and completely heterogeneous reaction conditions affording products in good to high yields. The catalyst is easily isolated from the reaction mixture by magnetic decantation and can be reused at least eight times without significant loss in activity.     

Mn(III)‐salan/graphene oxide/magnetite nanocomposite as a highly selective catalyst for aerobic epoxidation of olefins

A nanocomposite was synthesized using carbon‐coated Fe₃O₄ nanoparticle‐decorated reduced graphene oxide as a convenient and efficient supporting material for grafting of a manganese–reduced Schiff base (salan) complex via covalent attachment. The nanocomposite was characterized using X‐ray diffraction, Fourier transform infrared and diffuse reflectance UV–visible spectroscopies, inductively coupled plasma atomic emission spectrometry and scanning electron microscopy. It was evaluated as a catalyst for the aerobic epoxidation of olefins in acetonitrile in combination with a sacrificial co‐reductant (isobutyraldehyde). The catalytic performance of the heterogeneous system of the Mn–salan complex is superior to that of the homogeneous one. The catalyst activity strongly depends on the reaction temperature and nature of the solvent. The epoxide yield increases with the nucleophilic character of the olefin. The nanocomposite performs well as an epoxidation catalyst for electron‐rich and conjugated olefins. It can be recovered from the reaction medium by magnetic decantation and reused, maintaining good catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis of gold nanoparticles decorated on sulfonated three‐dimensional graphene nanocomposite and application as a highly efficient and recyclable heterogeneous catalyst for Ullmann homocoupling of aryl iodides and reduction of p‐nitrophenol

Gold nanoparticles were decorated onto sulfonated three‐dimensional graphene (3DG‐SO₃H) through spontaneous chemical reduction of HAuCl₄ by 3DG‐SO₃H. This nanocomposite exhibited excellent catalytic activity for the synthesis of symmetric biaryls via the Ullmann homocoupling of aryl iodides in an aqueous medium. Additionally, this nanocomposite was used as a catalyst for the reduction of p‐nitrophenol to p‐aminophenol. The catalyst could be used more than six times successively without significant deactivation.     

Gold nanoparticles supported on thiol‐functionalized reduced graphene oxide as effective recyclable catalyst for synthesis of tetrahydro‐4H‐chromenes in aqueous media

Gold nanoparticles supported on thiol‐functionalized reduced graphene oxide (AuNPs@RGO‐SH) were found to be a biocompatible, stable, recyclable heterogeneous catalyst. The catalysts were characterized by field emission scanning electron microscopy (FE‐SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT‐IR), thermal gravimetric analysis (TGA), and X‐ray diffraction spectroscopy (XRD). The obtained catalyst was used in synthesis of tetrahydro‐4H‐chromenes in aqueous media with excellent yields. The catalysts could be easily separated from the reaction mixture and recovered several times without a significant loss of activity.     

Pd‐Pt/modified GO as an efficient and selective heterogeneous catalyst for the reduction of nitroaromatic compounds to amino aromatic compounds by the hydrogen source

In this work, different nitroaromatic compounds were successfully reduced to their corresponding aromatic amines with excellent conversion and selectivity in methanol at 50 °C by using Pd‐Pt nanoparticles immobilized on the modified grapheme oxide (m‐GO) and hydrogen as the reducing source. The catalytic efficiency of Pd and Pd‐Pt loading on the modified GO was investigated for the reduction of various nitroaromatic compounds, and the Pd‐Pt/m‐GO system demonstrated the highest conversion and selectivity. The catalyst was characterized by different techniques including FT‐IR, Raman, UV–Vis, XRD, BET, XPS, FESEM, EDS, and TEM. The metal nanoparticles with the size of less than 10 nm were uniformly distributed on the m‐GO. The catalyst could be reused at least five times without losing activity, showing the stability of the catalyst structure. Finally, the efficiency of the prepared catalyst was compared with Pd‐Pt/AC, and Pd‐Pt/GO catalysts.     

Green synthesis of TiO2 nanoparticles as an efficient heterogeneous catalyst with high reusability for synthesis of 1,2‐dihydroquinoline derivatives

Nano materials find wide applications due to their behavior at nano scale. TiO₂ nanoparticles (TiO₂ NPs) was synthesized using Neem leaf extract. This is simple, rapid, eco‐friendly, cheaper and green tools for TiO₂ NPs synthesis using agricultural waste at lower applied temperature. Characterization of the extracted TiO₂ NPs was confirmed by XRD, SEM, EDAX, TEM, HR‐TEM, SAED, and FT‐IR, respectively. The catalytic activity of TiO₂ NPs was investigated in synthesis of 1,2‐dihydroquinoline derivatives with excellent yields and low cost. Purification of the synthesized 1,2‐dihydroquinoline derivatives carried out by easy work‐up of non‐chromatographic methods.     

Scolecite as an efficient heterogeneous catalyst for the synthesis of 2,4,5-triarylimidazoles

Natural scolecite has been found as an effective catalyst for the one-pot synthesis of 2,4,5-triarylimidazole derivatives via a three component reaction using benzil or benzoin, aldehydes and ammonium acetate. This method provides several advantages such as being environmentally benign, reusable, possessing high yields with increased variations of the substituents in the product and preparative simplicity.      

Graphene‐mesoporous anatase TiO2 nanocomposite: A highly efficient and recyclable heterogeneous catalyst for one‐pot multicomponent synthesis of benzodiazepine derivatives

The potential to bias chemical reaction pathways is a significant goal for physicists and material researchers to design revolutionary materials. Recently, two‐dimensional materials have appeared as a promising candidate for exploring novel catalyst activity in organic reaction. In this context, herein we report an easy and efficient synthesis of substituted benzodiazepines in high yields through the graphene‐based mesoporous TiO₂ nanocomposite (Gr@TiO₂ NCs) catalyst. To validate the merits of the Gr@TiO₂ NCs as a catalyst, we have also designed TiO₂ nanoparticle (NPs) under similar conditions. Successful comprehension realization of Gr@TiO₂ NCs and TiO₂ NPs were concluded from the XRD, SEM, HR‐TEM, EDS elemental mapping, FT‐IR, Raman, UV–Vis and TGA analysis. Gr@TiO₂ NCs has the propitious catalyst performance (~98%) over the TiO₂ NPs (~77%), which could be scrutinized in terms of graphene support toward the TiO₂ NPs and enable the large contact area between graphene and TiO₂ NPs. Incorporated graphene maintaining TiO₂ as a catalytically active and attracting electron to site isolation, as well as protecting TiO₂ from oxidative degradation during the reaction. Moreover, the role of graphene is suggested to prolonged reaction duration, yield and unaltered throughout the reaction because of the π‐π interaction between graphene and TiO₂ NPs. Additionally, the catalyst is recycled by filtration and reprocessed six times without having a significant loss in its catalytic activity.     

Zirconium (IV) porphyrin graphene oxide: a new and efficient catalyst for the synthesis of 3,4‐dihydropyrimidin‐2(1H)‐ones

A covalently cross‐linked graphene oxide (GO) as a catalyst was prepared by a cross‐linking process using the nucleophilic reaction of zirconium (IV)‐coordinated 5,10,15,20‐tetrakis (aminophenyl)porphyrin (ZrPPh) with carboxyl groups of the edges of GO (GO‐ZrPPh). The chemical structure of catalyst was characterized by different analyses such as FT‐IR, SEM, TEM, EDS, ICP, TGA and UV. All analyses confirm the occurrence of successfully covalent immobilization of ZrPPh on the GO. Also, TEM and SEM images show that ZrPPh has been immobilized in the both of the edges and the basal plane of GO. The activity of the catalyst was studied for the synthesis of 3,4‐dihydropyrimidin‐2(1H)‐ones via Biginelli reaction. The cross‐linked catalyst is able to catalyze the reaction in short reaction times and good to excellent yields.     

Postsynthetic modification of IRMOF‐3 with a copper iminopyridine complex as heterogeneous catalyst for the synthesis of 2‐aminobenzothiazoles

A copper iminopyridine complex has been immobilized on to a metal–organic framework (MOF) through postsynthetic modification of IRMOF‐3. The modified MOFs were fully demonstrated by using a variety of methods, and the structural integrity of the modified MOFs has been confirmed by powder X‐ray diffraction (XRD). Furthermore, it was shown that the modified IRMOF‐3 can act as an efficient solid catalyst for the synthesis of 2‐aminobenzothiazoles via the reaction of 2‐iodoanilines with isothiocyanates in a heterogeneous manner. Moreover, the catalyst could be facilely separated from the reaction mixture and reused for six consecutive cycles without significant degradation in catalytic activity. Copyright © 2014 John Wiley & Sons, Ltd.     

Electrospun copper oxide nanoparticles as an efficient heterogeneous catalyst for N-arylation of indole

The N-arylation of indoles with a variety of aryl bromides is reported using copper oxide nanoparticles as a heterogeneous catalyst. These copper oxide nanoparticles, which were produced in a novel, facile, and scalable fashion via an electrospinning technique, resulted in an excellent product yield under mild conditions. Moreover, the catalyst was easily recovered and reused several times without significant loss of activity.     

Mo (CO)6‐assisted Pd‐supported magnetic graphene oxide‐catalyzed carbonylation‐cyclization as an efficient way for the synthesis of 4(3H)‐quinazolinones

In this paper, a novel catalyst is introduced based on the immobilization of palladium on modified magnetic graphene oxide nanoparticles. The catalyst is characterized by several methods, including transmission electron microscopy, scanning electron microscopy, X‐ray fluorescence, vibrating‐sample magnetometer, Fourier transform‐infrared and dynamic light scattering (DLS) analysis. The activity of the catalyst was investigated in the synthesis of 4(3H)‐quinazolinones via Pd‐catalyzed carbonylation‐cyclization of N‐(2‐bromoaryl) benzimidamides by Mo (CO)₆. The Mo (CO)₆ is used as a carbon monoxide source for performing the reaction under mild conditions. The catalyst showed good reusability, and no change in activity was observed after 10 cycles of recovery.     

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.     

MCM‐41‐supported mercapto palladium(0) complex: an efficient and recyclable catalyst for the heterogeneous Stille coupling reaction

The Stille cross‐coupling reaction of organostannanes with aryl halides was achieved in the presence of a catalytic amount of MCM‐41‐supported mercapto palladium(0) complex (1 mol%) in DMF? H₂O (9:1) under air atmosphere in good to high yields. This MCM‐41‐supported palladium catalyst can be reused at least 10 times without any decrease in activity. Copyright © 2009 John Wiley & Sons, Ltd.     

Terephthalic acid derived ligand‐stabilized palladium nanocomposite catalyst for Heck coupling reaction: without surface‐modified heterogeneous catalyst

A new protocol is reported for the synthesis of a heterogeneous palladium nanocomposite stabilized with a terephthalic acid‐derived ligand (N ,N ‐bis(4‐hydroxy‐3‐methoxybenzylidene)terephthalohydrazide). This is a highly insoluble ligand in common organic solvents, except dimethylformamide and dimethylsulfoxide. The resulting palladium nanocomposite acts as an efficient catalyst precursor for Mizoroki–Heck coupling reactions conducted under various reaction conditions. The spectral data suggest that the rate, yield and recycling of the catalyst are more effective for C–C coupling reactions. Copyright © 2016 John Wiley & Sons, Ltd.     

One‐step synthesis of Pt@three‐dimensional graphene composite hydrogel: an efficient recyclable catalyst for reduction of 4‐nitrophenol

A Pt@three‐dimensional graphene (Pt@3DG) composite hydrogel with a unique porous nanostructure was prepared and used as an efficient, recyclable and robust catalyst for the reduction of 4‐nitrophenol to 4‐aminophenol under mild conditions. The influence of graphene architecture on catalytic activities was comparatively investigated by loading the same amount of Pt on reduced graphene oxide. Pt@3DG exhibits a very high catalytic activity owing to the three‐dimensional macroporous framework with high specific surface area, numerous activation sites and efficient transport pathways. Moreover, catalyst separation can be easily achieved by simple filtration, and the catalyst can be reused for at least five runs, maintaining its high catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

CuI‐functionalized halloysite nanoclay as an efficient heterogeneous catalyst for promoting click reactions: Combination of experimental and computational chemistry

Amine‐functionalized halloysite nanotubes (HNTs‐2 N) were prepared and further modified by introduction of salicylaldehyde and formation of imine functionality (HNTs‐2 N‐Sal). The latter was subsequently used for immobilization of CuI and formation of CuI@HNTs‐2 N‐Sal, which could effectively promote click reactions of terminal alkynes, sodium azide and α‐haloketones or alkyl halides in aqueous media and under mild reaction conditions to afford 1,2,3‐triazoles in relatively short reaction times. Notably, the catalyst could be recycled in up to six reaction runs with negligible loss of catalytic activity and CuI leaching. Also, the geometry of CuI adsorption on the modified HNTs surface was explored by molecular simulation with density functional theory. Furthermore, topographic steric maps of possible coordination modes were obtained using the recently released SambVca2 web application tool. Based on obtained results, a catalytic site with superior performance was suggested.     

Cross‐coupling reactions using porous multipod Cu2O microcrystals as recoverable catalyst in aqueous media

Porous multipod Cu₂O microcrystals were found to be an efficient, highly recyclable and eco‐friendly catalyst for the cross‐coupling reactions of aryl halides and terminal alkynes with high yields in aqueous media. Noteworthy, the Cu₂O catalyst can be reused for several times without significant decrease in catalytic activity.