CeO2/CuO@N-GQDs@NH2 nanocomposite as a high-performance catalyst for the synthesis of benzo[g]chromenes

A three-component reaction of aromatic aldehydes, malononitrile or ethyl cyanoacetate and 2-hydroxy-1,4-naphthaquinone has been achieved in the presence of an amino-functionalized CeO₂/CuO@ nitrogen graphene quantum dot nanocomposite as a highly effective heterogeneous catalyst to produce benzo[g]chromenes. The catalyst has been characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, energy-dispersive X-ray spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller (BET) and vibrating sample magnetometry. This new catalyst has been demonstrated to be highly effective in the preparation of benzo[g]chromenes.     

An eco-friendly and energy-efficient protocol for the Heck reaction under solar radiation catalyzed by rice husk silica‐anchored cinchonine.Pd nanocomposite

An environmentally friendly and energy-efficient method for the carbon–carbon bond formation via cross-coupling Heck reaction using rice husk silica-anchored cinchonine.Pd nanocomposite as a heterogeneous catalyst under concentrated solar radiation is being reported. In this investigation, first, silica nanoparticles were synthesized using rice husks as available agricultural bioresources. Then, the surface of nano silica was modified by grafting (3-mercaptopropyl) trimethoxysilane, and after that, thiol-ene free radical reaction of its SH groups with alkene function of cinchonine by azobisisobutylonitrile initiator. Finally, the target nanocomposite, nano SiO₂-S-Cin.Pd, was created via loading palladium nanoparticles into the mesoporous nanocomposite by its reaction by palladium acetate, followed by ethanol reduction. The structure and morphology of the nano SiO₂-S-Cin.Pd nanocomposite was characterized using Fourier transform infrared spectra, X-ray diffraction patterns, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. The catalytic ability of this nanocomposite was investigated in the arylation of olefins in both concentrated solar radiation and conventional thermal conditions. A comparison of the conventional and CSR methods for C–C bond formation in PEG, showed that the CSR approach is a better alternative route with a high energy-saving strategy. The nanocatalyst is easily removed from the mixture and has been tested on several runs without a loss of catalytic activity. The heterogeneity of the nano SiO₂-S-Cin.Pd catalyst was confirmed by hot filtration test. This method has the advantages of simple methodology, easy work-up, high yields, short reaction times, and greener conditions. In addition to convenience, this technology improves product purity and offers economic and environmental benefits.     

Silica‐Supported P2O5 as an Efficient Heterogeneous Catalyst for the One Pot Synthesis of 3‐Amino‐imidazo[2,1‐b](1,3)benzothiazole under Green Conditions

The new approach involving the solid supported catalyst for the formation of C–N bond followed by cyclization has been reported. In this work we have reported a facile, efficient, and environment‐friendly protocol for the synthesis of some new 3‐amino‐imidazo[2,1‐b](1,3)benzothiazole derivatives by one‐pot condensation of 2‐aminobenzothiazole, indole‐3‐carbaldehyde, and aryl isocyanide in the presence of silica‐supported P₂O₅ as a heterogeneous solid acid catalyst. The reaction was performed using conventional method under green conditions. The present approach offers the advantages of simple methodology, inexpensive acid catalyst, short reaction time, easy work up with excellent yield, simple purification and use of green solvent. All the newly synthesized compounds were characterized in details using physical and chemical techniques such as melting point, ¹H NMR, ¹³C NMR, and FTIR spectroscopy.     

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.     

Biosynthesis of Pd/MnO2 nanocomposite using Solanum melongena plant extract and its application for the one‐pot synthesis of 5‐substituted 1H‐tetrazoles from aryl halides

In this work, for the first time, Solanum melongena plant extract was used for the green synthesis of Pd/MnO₂ nanocomposite via reduction osf Pd(II) ions to Pd(0) and their immobilization on the surface of manganese dioxide (MnO₂) nanoparticles (NPs) as an effective support. The synthesized nanocomposite were characterized by various analytical techniques such as Fourier transform infrared (FT‐IR), X‐ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy dispersive X‐ray spectroscopy (EDS) and UV–Vis spectroscopy. The catalytic activity of Pd/MnO₂ nanocomposite was used as a heterogeneous catalyst for the one‐pot synthesis of 5‐substituted 1H‐tetrazoles from aryl halides containing various electron‐donating or electron‐withdrawing groups in the presence of K ₄ [Fe (CN) ₆ ] as non‐toxic cyanide source and sodium azide. The products were obtained in good yields via a simple methodology and easy work‐up. The nanocatalyst can be recycled and reused several times with no remarkable loss of activity.     

Fe(III) @g-C<Subscript>3</Subscript>N<Subscript>4</Subscript> nanocomposite-catalyzed green synthesis of di-indolyloxindole derivatives

A Fe(III)/g-C₃N₄ nanocomposite was simply synthesized by impregnation of FeCl₃ with g-C₃N₄, and the heterogeneous nanocomposite was characterized by various techniques; including X-ray diffraction, Fourier-transform infrared spectroscopy, and transmission electron microscopy. Then, the 3-indolylation reaction of isatin with indole derivatives was carried out in the presence of the Fe(III)/g-C₃N₄ nanocomposite in water in reflux conditions. The results showed that the corresponding products were synthesized in excellent yields (up to 96%) in a short time (30 min). The significant features of this protocol are the non-toxic solvent, green media, short reaction time and high yields.     

Spirooxindole-fused pyrazolo pyridine derivatives: NiO–SiO2 catalyzed one-pot synthesis and antimicrobial activities

We describe here a one-pot synthesis of 13 spirooxindole-fused pyrazolo pyridine derivatives using NiO–SiO₂ catalyst via three-component reaction of isatin, 5-amino-3-methylpyrazole, and malononitrile. This multicomponent one-pot protocol also features shorter reaction time, good yield, and simple work-up using a recoverable and reusable solid acid heterogeneous catalyst. The NiO–SiO₂ catalyst was characterized using different instrumental techniques such as X-ray diffraction study, surface area analysis, transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, UV-DRS (diffuse reflectance spectroscopy), and energy dispersive X-ray analysis (EDX). The new compounds were tested for in-vitro anti-microbial activity.     

Chitosan/CuO nanocomposite films mediated regioselective synthesis of 1,3,4-trisubstituted pyrazoles under microwave irradiation

Copper oxide-chitosan nanocomposite was synthesized simply via simple solution casting method and was characterized by different analytical techniques, including Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), and Thermogravimetric analysis (TGA). The copper oxide content in the prepared nanocomposite film was estimated from the Energy-dispersive X-ray spectroscopy (EDS) and the copper content in the sample was found to be 12.57 wt%. From the XRD pattern, the average particle size was calculated using Debye-Scherrer formula and was found to be 33.5 nm. The TGA curves showed that the thermal stability of the hybrid nanocomposite was found to be superior to the native CS, which is attributed to the existence of the thermally stable CuO. The chitosan/CuO nanocomposite has proven to be an excellent heterogeneous base catalyst for regioselective 1,3-dipolar cycloaddition of hydrazonoyl chlorides 1a-j with enamine 2 to give 1,3,4-trisubstituted pyrazoles 3a-j in excellent yields. The performance of the nanocomposite was optimized by varying several reaction conditions.     

Trisaminomethane–cobalt complex supported on Fe3O4 magnetic nanoparticles as an efficient recoverable nanocatalyst for oxidation of sulfides and C–S coupling reactions

In this work, trisaminomethane–cobalt complex immobilized onto the surface of Fe₃O₄ magnetic nanoparticles was successfully prepared via a simple and inexpensive procedure. The prepared nanocatalyst was considered a robust and clean nanoreactor catalyst for the oxidation and synthesis of sulfides under green conditions. This ecofriendly heterogeneous catalyst was characterized by Fourier transform infrared spectroscopy, X-ray diffractometry, energy-dispersive X-ray spectroscopy, inductively coupled plasma-atomic emission spectroscopy, thermogravimetric analysis, vibrating sample magnetometry, X-ray mapping, scanning electron microscopy, and transmission electron microscopy techniques. Use of green medium, easy separation and workup, excellent reusability of the nanocatalyst, and short reaction time are some outstanding advantages of this method.     

Synthesis and characterization of terbium doped TiO2 nanoparticles and their use as recyclable and reusable heterogeneous catalyst for efficient and environmentally sustainable synthesis of spiroannulated indolo[3,2-c]quinolines- mimetic scaffolds of isocryptolepine

An efficient and environmentally sustainable domino protocol has been presented for the synthesis of structurally diverse spiroannulated indolo[3,2-c]quinolines involving three component sequential reaction of phenylhydrazine, o-aminoacetophenone and cyclic ketones using nanostructured terbium doped TiO₂ as recyclable and reusable heterogeneous catalyst. The nanostructured catalyst was synthesized successfully and characterized by X-ray Diffraction (XRD), transmission electron microscopy (TEM), EDX and Fourier transform infra-red spectroscopy (FTIR). The substitution of Ti⁺⁴ with Tb⁺³ and the formation of Ti-O-Tb bonds as a result of doping of Terbium with TiO₂ NPs increases the catalytic efficiency and facilitates the reaction to provide the products in excellent yields. The present protocol with special features; operational simplicity, atom-economy, mild reaction conditions, environmental sustainability and high synthetic efficiency with recyclability and reusability of catalyst has been reported for the first time to synthesize spiroannulated indoloquinolines and expecting to provide the library of promising new leads in drug discovery research.     

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.     

Pt deposited TiO2 catalyst fabricated by thermal decomposition of titanium complex for solar hydrogen production

C, N codoped TiO₂ catalyst has been synthesized by thermal decomposition of a novel water-soluble titanium complex. The structure, morphology, and optical properties of the synthesized TiO₂ catalyst were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of the Pt deposited TiO₂ catalysts synthesized at different temperatures was evaluated by means of hydrogen evolution reaction under both UV–vis and visible light irradiation. The investigation results reveal that the photocatalytic H₂ evolution rate strongly depended on the crystalline grain size as well as specific surface area of the synthesized catalyst. Our studies successfully demonstrate a simple method for the synthesis of visible-light responsive Pt deposited TiO₂ catalyst for solar hydrogen production.     

L-Tyrosine-Pd complex supported on Fe3O4 magnetic nanoparticles: A new catalyst for C–C coupling and Synthesis of sulfides

In the present work, Fe₃O₄@L-Tyrosine-Pd heterogeneous nanocatalyst was prepared by a simple and inexpensive procedure. The prepared nanocatalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray Diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), inductively coupled plasma optical emission spectroscopy (ICP-OES), scanning electron microscopy (SEM), Transmission electron microscopy)TEM(, X-ray mapping, thermal gravimetric analysis (TGA), N₂ adsorption and desorption (BET) and vibrating sample magnetometer (VSM) techniques. Besides, it was employed as an efficent catalyst for C-C cross coupling and S-arylation reactions under green conditions. The optimized conditions for these reactions are described. The heterogeneous catalyst can be easily separated by applying a simple magnet and can also be reused in several consecutive runs without appreciable change in its catalytic activity.     

Preparation of core/shell/shell CoFe2O4/OCMC/Cu (BDC) nanostructure as a magnetically heterogeneous catalyst for the synthesis of substituted xanthenes,quinazolines and acridines under ultrasonic irradiation

Highly efficient synthesized magnetic cobalt ferrite nanoparticles supported on OCMC@Cu (BDC) was utilized in the preparation of biologically active heterocyclic compounds through one-pot three-component reactions between of aldehydes, dimedone, aryl amines/2-naphthol/urea under ultrasonic irradiation. This method has various advantages including excellent yields, little catalyst loading, simple procedure, facile catalyst separation, short reaction times, eco-friendly approach and simple purification. The catalyst was characterized by various spectroscopy methods such as fourier-transform infrared (FT-IR), energy-dispersive X-ray (EDX), scanning electron microscope (SEM), X-ray diffraction (XRD) and N₂ adsorption–desorption isotherm (BET). Furthermore, the heterocyclic compounds were characterized by spectral techniques. The nanocomposite was simply separated byusing an external magnet, and it can be recycled several times without significant loss of activity.     

L-lysine-Pd Complex Supported on Fe3O4 MNPs: a novel recoverable magnetic nanocatalyst for Suzuki C-C Cross-Coupling reaction

In this work, L-lysine-Pd Complex, immobilized onto the surface of Fe₃O₄ MNPs, was successfully prepared via simple and inexpensive procedure. The prepared nanocatalyst was considered as a robust and clean nano-reactor catalyst for the Suzuki and Heck C-C Cross-Coupling reactions in water as the green condition. This eco-friendly heterogeneous catalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), X-Ray Diffractometer (XRD), energy-dispersive X-ray spectroscopy (EDS), inductively coupled plasma atomic emission spectroscopy (ICP), X-ray mapping, BET, thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) techniques. The use of a green medium, easy separation and workup, excellent reusability of the nanocatalyst and short reaction time are some outstanding advantages of this method.     

A novel nanomagnetic solid acid catalyst for the synthesis of new functionalized bis-coumarin derivatives under microwave irradiations in green conditions

In this study, a novel, green, environmentally friendly and magnetically heterogeneous catalyst based on the immobilization of sulfosalicylic acid onto Fe₃O₄ nanoparticles (Fe₃O₄@sulfosalicylic acid MNPs) is reported. The bis-coumarin analogs were synthesized in high yield using the reaction of 1 equivalent of aryl aldehydes with 2 equivalents of 4-hydroxycoumarin in water under microwave irradiation conditions. Scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, thermogravimetric analysis, dynamic light scattering, vibrating sample magnetometry, Fourier transform infrared spectroscopy, UV–visible absorption, and Brunauer-Emmett-Teller (BET) techniques confirmed the successful synthesis of the catalyst. The main attractive characteristics of the presented green protocol are very short reaction times (10–15 min), excellent yields, and the avoidance of hazardous or toxic reagent and solvents. Thermal durability, easy separation, and high reusability are important advantages of the new catalyst in comparison to other catalysts.     

Synthesis and analysis of ZnO-CoMoO4 incorporated organic compounds for efficient degradation of azo dye pollutants under dark ambient conditions

In recent years, the degradation of organic dyes under dark conditions, at room temperature and atmosphere pressure, without additional lights or chemical stimulants, has been widely investigated. Here, a nanocomposite of ZnO-CoMoO₄ was synthesized using an organic template and investigated as a catalyst to degrade methyl orange in aqueous environment under dark, ambient conditions. The organic compounds of Abies Pindrow Royle were reacted with a precursor solution following sol–gel synthesis methodology to modify the chemistry and morphology of ZnO-CoMoO_4, so formed. The structure of the nanocomposite was confirmed by X-ray diffraction, Raman spectroscopy and energy dispersive X-ray spectroscopy while nanostructures were examined by field emission scanning electron microscopy. Organic functional groups were determined by Fourier transform infrared spectroscopy and Gas chromatography–mass spectrometry. The organic compound incorporated nanocomposite was revealed to be an excellent catalyst with 95% degradation of methyl orange in aqueous environment under dark ambient conditions within 10 min. The catalyst also revealed 99% degradation of azo dye in the presence of solar light. Furthermore, the catalysts illustrated good stability with pseudo first order kinetics (R² < 1) in the light as well as in the dark conditions with outstanding reusability till four cycles of experiments. Therefore, nanostructure and organic species of Abies Pindrow Royle were found to enhance the catalytic behavior of ZnO-CoMoO₄ towards methyl orange degradation even in dark conditions.     

A novel ternary GO@SiO2‐HPW nanocomposite as an efficient heterogeneous catalyst for the synthesis of benzazoles in aqueous media

A new solid acid catalyst, consisting of 12‐phosphotungstic heteropoly acid (HPW) supported on graphene oxide/silica nanocomposite (GO@SiO₂), has been developed via immobilizing HPW onto an amine‐functionalized GO/SiO₂ surface through coordination interaction (GO@SiO₂‐HPW). The GO@SiO₂‐HPW nanocomposite was characterized by Fourier transform infrared (FT‐IR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and powder X‐ray diffraction (XRD). The prepared nanocomposite could be dispersed homogeneously in water and further used as a heterogeneous, reusable, and efficient catalyst for the synthesis of benzimidazoles and benzothiazoles by the reaction of 1,2‐phenelynediamine or 2‐aminothiophenol with different aldehydes.     

Efficient four‐component synthesis of spiroindole derivatives catalysed by a versatile and reusable nano‐paramagnetic catalyst

A simple, efficient and environmentally benign route was developed for the preparation of spiro(indoline‐3,4‐pyrano[2,3‐c ]pyrazole) derivatives with good yields from condensation of isatins, malononitrile (or ethyl cyanoacetate), hydrazine hydrate and ethyl acetoacetate catalysed by PFu@Fe₃O₄ nanocomposite. The use of easily available catalyst, shorter reaction times, better yields, simplicity of reaction, heterogeneous system and easy work‐up are the advantages of the method presented. Characterization of the catalyst was performed using Fourier transform infrared spectroscopy, X‐ray diffraction and transmission electron microscopy.     

Synthesis of benzo[b]xanthene-triones and tetrahydrochromeno[2,3-b]xanthene tetraones via three- or pseudo–five-component reactions using Fe3O4@SiO2/PEtOx as a novel,magnetically recyclable,and eco-friendly nanocatalyst

In this study, poly(2-ethyl-2-oxazoline) (PEtOx) immobilized on Fe₃O₄ nanoparticles (Fe₃O₄@SiO₂/PEtOx) has been constructed as a new, heterogeneous, efficient, and recyclable nanocatalyst. The prepared nanocatalyst was characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), powder X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS) analysis, and vibrating-sample magnetometer (VSM) techniques. Nanocatalyst was employed to synthesize benzo[b]xanthene-triones and tetrahydrochromeno[2,3-b]xanthene tetraones via one-pot three- or pseudo–five-component reaction between 2-hydroxy-1,4-naphthoquinone or 2,5-dihydroxy-1,4-benzoquinone, aldehyde, and dimedone or 1,3-cyclohexanedione under reflux condition in ethanol. The catalyst could be easily separated and recycled several times without considerable loss of activity. Clean methodology, easy work-up, mild reaction condition, short reaction time with good-to-excellent yields, and simple preparation of the catalyst are some advantages of the presented work.