Monoclinic zirconia nanoparticle-catalyzed regioselective synthesis of some novel substituted spirooxindoles through one-pot multicomponent reaction in a ball mill: A step toward green and sustainable chemistry

A highly efficient, green as well as atom economical protocol for the synthesis of substituted spirooxindoles from m-ZrO₂ NPs catalyzed multicomponent reaction of isatin derivatives with ethyl cyanoacetate and 1,3-dicarbonyl compounds in a ball mill has been established. Because of the simple and readily available starting materials, easy operation, and high bioactivity of substituted spirooxindoles, this strategy can be broadly applied to medicinal chemistry. The recyclability of the m-ZrO₂ Nps catalyst is another emphasis of proposed methodology.     

Silver phosphate supported on metal–organic framework (Ag3PO4@MOF‐5) as a novel heterogeneous catalyst for green synthesis of indenoquinolinediones

A new Ag₃PO₄@MOF‐5 catalyst has been synthesized and successfully applied in the green synthesis of a library of indenoquinolinediones via one‐pot, multi‐component reaction of aldehyde, indanedione and enaminone under solvent‐free conditions at room temperature. The catalyst was characterized using various spectroscopic techniques and elemental analysis. The catalyst can be easily separated and exhibits significant recyclability, with insignificant loss of activity after four consecutive runs. The protocol presented has advantages like green reaction conditions, high yield of products, no need for column chromatography and good recyclability.     

MnO2@Fe3O4 Magnetic Nanoparticles as Efficient and Recyclable Heterogeneous Catalyst for Benzylic sp3 C−H Oxidation

Herein, we report a highly chemoselective and efficient heterogeneous MnO₂@Fe₃O₄ MNP catalyst for the oxidation of benzylic sp³ C?H group of ethers using TBHP as a green oxidant to afford ester derivatives in high yield under batch/continuous flow module. This catalyst was also effective for the benzylic sp³ C?H group of methylene derivatives to furnish the ketone in high yield which can be easily integrated into continuous flow condition for scale up. The catalyst is fully characterized by spectroscopic techniques and it was found that 0.424 % MnO₂@Fe₃O₄ catalyzes the reaction; the magnetic nanoparticles of this catalyst could be easily recovered from the reaction mixture. The recovered catalyst was recycled for twelve cycles without any loss of the catalytic activity. The advantages of MnO₂@Fe₃O₄ MNP are its catalytic activity, easy preparation, recovery, and recyclability, gram scale synthesis with a TOF of up to 14.93 h^?1 and low metal leaching during the reaction.     

Nano ceria catalyzed synthesis of α-aminophosphonates under ultrasonication

A simple, efficient and general method has been developed for the one-pot three component syntheses of α-aminophosphonates. The condensation of aldehyde, amine and triethyl phosphite by employing CeO₂ nanoparticles as catalyst gave α-aminophosphonates. The catalyst showed good recyclability. Nano CeO₂ has been found to be an excellent catalyst for the green synthesis of α-aminophosphonates under ultrasound irradiation and solvent-free condition. The α-aminophosphonates are obtained in good to excellent yield. This catalyst provides cleaner conversion, short reaction time and high selectivity which makes the protocol feasible and economical attractive.     

A one‐pot method for synthesis of reduced graphene oxide‐supported Cu–Cu2O and catalytic application in tandem reaction of halides and sodium azide with terminal alkynes

Reduced graphene oxide (RGO)‐supported Cu–Cu₂O nanocomposite material (Cu‐Cu₂O@RGO) was prepared through a one‐pot reflux synthesis method. The morphology, crystal structure and composition of the prepared Cu‐Cu₂O@RGO were characterized using transmission electron microscopy, X‐ray diffraction, and X‐ray photoelectron, infrared and Raman spectroscopies. Cu‐Cu₂O@RGO as a heterogeneous catalyst was applied to tandem reactions of halides and sodium azide with terminal alkynes to synthesize effectively 1,4‐disubstituted 1,2,3‐triazoles. Moreover, the catalyst showed excellent recyclability performance with very little leaching of the metal. Compared with homogeneous catalysts, Cu‐Cu₂O@RGO as a green and efficient catalyst was recoverable, easy to separate and highly stable in the tandem method for the synthesis of 1,2,3‐triazole compounds.     

Ionic Liquid Promoted Multicomponent Reaction: A Good Strategy for the Eco‐Compatible Synthesis of Functionalized Pyrroles

Task specific [bmim]BF₄ was found to be reusable, alternative, and effective reaction media for multicomponent synthesis of highly functionalized pyrroles. Generality of the procedure was established by synthesizing various pyrroles from wide range of aromatic/aliphatic amine, phenacyl bromide, and electrophilic alkynes by utilizing this protocol without any acid or metal catalyst. Ecocompatibility, short reaction time, excellent yield, recyclability of [bmim]BF₄, low cost, easy work‐up, and mild reaction conditions are additional advantages of the procedure in the context of sustainable and green chemistry.     

Synthesis of bifunctional cyclic carbonates from CO2 catalysed by choline-based systems

Easily prepared choline iodide is an active catalyst for the synthesis of cyclic carbonates through the coupling reaction of CO₂ and epoxides using low pressure (1 MPa), moderate temperature (85 ºC) and green solvents (ethanol and propan-2-ol). The effects of reaction temperature, pressure, reaction time and amount of catalyst used were also investigated. The results showed moderate to high yields and excellent selectivities of cyclic carbonates with vinyl or acrylate groups under mild reaction conditions. The heterogenization of choline over a Merrifield resin gives access to a supported catalyst with good recyclability and reactivity that can be extended to a variety of terminal epoxide substrates.     

Rutile phase nanoTiO2 as an effective heterogeneous catalyst for condensation reaction of isatin derivatives with 1,2-diaminobenzene under solvent free conditions: A greener “NOSE” approach

Rutile phase of TiO₂ nanoparticles were readily prepared and identified as an efficient heterogeneous catalyst for the synthesis of a library of quinoxaline derivatives by condensation reaction of isatin derivatives with o-phenylenediamine under solvent-free conditions. The presented method is mild, environmentally friendly, inexpensive and highly effective to give the products in good to excellent yields. The recyclability of the catalyst is another emphasis of proposed methodology.     

Fe3O4@SiO2@sulfated boric acid as superparamagnetic and recyclable nanocatalyst‐assisted,one‐pot,pseudo four‐component synthesis of 5‐amino‐2‐aryl‐3H‐chromeno[4,3,2‐de][1,6]naphthyridine‐4‐carbonitrile derivatives

The catalytic performance of the superparamagnetic nanocatalyst Fe₃O₄@SiO₂@Sulfated boric acid as a green, recyclable, and acidic solid catalyst in the synthesis of chromeno[4,3,2‐de][1,6]naphthyridine derivatives has been studied. Chromeno[4,3,2‐de][1,6]naphthyridine derivatives via a pseudo four‐component reaction from aromatic aldehydes (1 mmol), malononitrile (2 mmol), and 2′‐hydroxyacetophenone in the presence of Fe₃O₄@SiO₂@Sulfated boric acid (0.004 g) as a nanocatalyst in 3 mL of water as a green solvent at 80°C has been synthesized. The advantages of this method are higher product yields in shorter reaction times, easy recyclability and reusability of the catalyst, and easy work‐up procedures. The nanocatalyst was reused at least six times. The nanocatalyst retained its stability in the reaction, and after reusability, it was separated easily from the reaction by an external magnet.     

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.     

La(OTf)3-catalyzed,three-component synthesis of spiro[Indolo-3,10′-indeno[1,2-b]quinolin]-2,4,11′-triones in PEG-400 under conventional heating and ultrasonic irradiation

An efficient La(OTf)₃-catalyzed three-component reaction has been developed for the synthesis of highly substituted spiro[indolo-3,10′-indeno[1,2-b]quinolin]-2,4,11′-triones in polyethylene glycol (PEG-400) under conventional heating and ultrasonic irradiation. The most exciting feature of this methodology is its mechanism involving the unusual ring opening of an isatin moiety followed by recyclization. All the reactions resulted in good yield of products. The important features of this reaction are use of green solvent, good yields, less reaction times, and recyclability of the catalyst.     

A facile and efficient carbocatalytic route to quaternary C-bearing N-tosylaziridines from Morita-Baylis-Hillman adduct in water

Graphene oxide (GO)/GO-I₂ co-catalyzed green synthesis of tosylaziridine bearing keto and nitrile/ester functional groups is reported. The strategy involves sequential GO-catalyzed oxidation of benzylic alcohol and GO-I₂ catalyzed nitrene insertion into olefin of Morita-Baylis-Hillman adduct. Operational simplicity, use of water as solvent, ambient reaction conditions, excellent yield of products (88–96%) and recyclability of catalyst up to five times without any substantial change in morphology as well as catalytic efficiency are the salient features of the envisaged protocol.     

Efficient and Green Synthesis of N‐aryl Pyrroles Catalyzed by Ionic Liquid [H‐NMP][HSO4] in Water at Room Temperature

A suitable and efficient method for the synthesis of N‐aryl pyrroles by using 2,5‐dimethoxy tetrahydrofuran and several primary aromatic amines in the presence of the catalytic amount of [H‐NMP][HSO₄] under room temperature was described. This method has the advantages such as; easy reaction workup, absolutely separated of catalyst from the reaction mixture and smoothly recyclability of catalyst. In this reaction, N‐substituted pyrroles were obtained as desired products in excellent yields and short reaction times via green and one‐pot procedure.     

Silica‐coated nano‐Fe3O4‐supported iminopyridine palladium complex as an active,phosphine‐free and magnetically separable catalyst for Heck reactions

A novel magnetic nanoparticle‐supported iminopyridine palladium complex was successfully prepared by attaching palladium acetate to iminopyridine ligand‐functionalized silica‐coated nano‐Fe₃O₄. The as‐prepared catalyst was well characterized and was evaluated in Heck reactions in terms of activity and recyclability. It was found to be highly efficient for the reactions of various aryl iodides and aryl bromides having electron‐withdrawing groups with olefins under phosphine‐free and inert atmosphere‐free conditions. Moreover, the catalyst could be conveniently recovered using an external magnet, and the recyclability was influenced by the base in the Heck reaction. The catalyst could be reused at least six times with no significant loss in activity when triethylamine acted as the base.     

CuFeO2/tetrabutylammonium bromide catalyzes selective synthesis of 1,4‐disubstituted 1,2,3‐triazoles in neat water at room temperature

A completely green medium including water as a solvent and antiviral CuFeO₂ as a catalyst is described for the synthesis of 1,4‐disubstituted 1,2,3‐triazoles. Excellent yields of products are obtained at room temperature. Cost effectiveness, high stability and high recyclability of CuFeO₂ along with antiviral properties of the catalyst make it a unique catalyst for cycloadditions of phenylacetylene with a wide variety of aryl halides. Copyright © 2016 John Wiley & Sons, Ltd.     

Effective and selective aerobic oxidation of primary and secondary alcohols using CoFe2O4@HT@Imine‐CuII and TEMPO in the air atmosphere

In this study, we present a versatile and easy procedure for modifying a cobalt ferrite nanoparticle step by step. A new nanocatalyst was prepared via Cu^II immobilized onto CoFe₂O₄@HT@Imine. The catalyst was fully characterized by Fourier‐transform infrared (FT‐IR), energy‐dispersive X‐ray spectroscopy (EDX), field emission scanning electron microscopy (FE‐SEM), X‐ray diffraction (XRD), and vibrating sample magnetometer (VSM) analyses. The current procedure as a green protocol offers benefits including a simple operational method, an excellent yield of products, mild reaction conditions, minimum chemical wastes, and short reaction times. Without any significant reduction in the catalytic performance, up to five recyclability cycles of the catalyst were obtained. The optimization results suggest that the best condition in the oxidation of benzyl alcohol derivatives is 0.003 g of the CoFe₂O₄@HT@Imine‐Cu^II catalyst, TEMPO, at 70°C under solvent‐free condition and air.     

Use of nanoporous Na+-montmorillonite sulfonic acid (SANM) as an eco-benign, efficient and reusable solid acid catalyst for the one-pot synthesis of 14-aryl-14-H-dibenzo[a,j]xanthenes and 1,8-dioxo-dodecahydroxanthene derivatives

Nanoporous Na⁺-montmorillonite sulfonic acid was found to be an efficient and green catalyst for the synthesis of various 14-aryl-14H-dibenzo[a,j]xanthenes and 1,8-dioxo-dodecahydroxanthene derivatives by the reaction of aldehydes with 2-naphthol and 1,3-cyclohexanedione, respectively. This novel synthetic method has the advantages of high yields, short reaction times and recyclability of the catalyst, simplicity and easy workup compared to the conventional methods reported in the literature.     

Diimino Nickel Complex Anchored into the MOF Cavity as Catalyst for Epoxidation of Chalcones and Bischalcones

Nickel-pyridylimine complex was incorporated into (Cr)NH₂-MIL-101 through condensation of 2-pyridine carboxaldehyde and NiCl₂ in presence of (Cr)NH₂-MIL-101-MOF in a one pot method. The prepared catalyst was characterized by XRD, FTIR, SEM, TEM and NMR methods. The obtained catalyst demonstrates an appropriate pattern for a post-synthetic covalent modification with catalytic active sites. This heterogeneous catalyst showed efficiency in the epoxidation reaction of chalcones and bischalcones, and exhibited appropriate recyclability, rather short reaction times and high yields.     

Convenient Synthesis of 14‐Aryl‐14‐H‐dibenzo[a,j]xanthenes Catalyzed by Acyclic Brønsted Acidic Ionic Liquid [H—NMP]+[HSO4]− under Microwave Irradiation

Efficient method for direct preparation of 14‐aryl‐14‐H‐dibenzo[a,j]xanthenes through condensation of β‐naphthol with various aromatic aldehydes in the presence of the catalytic amount of [H—NMP]⁺[HSO₄]^? under microwave irradiation was described. This method has the advantages such as; very easy reaction workup, absolute separation of catalyst from the reaction mixture and smooth recyclability of catalyst. In this reaction 14‐aryl‐14‐H‐dibenzo[a,j]xanthenes were obtained as desired products in excellent yields and short reaction times via green and one‐pot procedure.     

Macroporous 3D carbon-nitrogen (CN) confined MoOx catalyst for enhanced oxidative desulfurization of dibenzothiophene

Macroporous 3D carbon doped with nitrogen confined Mo catalyst (MoO_x@CN) had been prepared by a facile one-step pyrolysis technique using silica as a template and was employed for oxidative desulfurization (ODS) of dibenzothiophene (DBT) in model fuel with H₂O₂ as oxidant. The effect of different operating conditions (i.e., reaction temperature and time, catalyst dosage, H₂O₂/DBT (O/S) molar ratio) were also systematic investigated. Under the optimal reaction condition, MoO_x@CN catalyst exhibited highly excellent ODS performance toward DBT, the highest sulfur removal efficiency can be up to 99.9% and sulfur content was wiped out from 800 ppm to 10 ppm. Due to the robust 3D structure promoting rapid transfer, in addition to the increased number of active sites induced by the Mo vacancies, the catalyst, prepared using chitosan and ammonium heptamolybdate in a mass ratio of 1:0.5, displayed rapid kinetics and low activation energy in the oxidation of dibenzothiophene. Moreover, it exhibited excellent recyclability after five cycles without any obvious decrease in catalytic activity for the oxidative desulfurization reaction.