Ultrasound-Promoted preparation and application of novel bifunctional core/shell Fe3O4@SiO2@PTS-APG as a robust catalyst in the expeditious synthesis of Hantzsch esters

In this work, D-(-)-α-phenylglycine (APG)-functionalized magnetic nanocatalyst (Fe₃O₄@SiO₂@PTS-APG) was designed and successfully prepared in order to implement the principles of green chemistry for the synthesis of polyhydroquinoline (PHQ) and 1,4-dihydropyridine (1,4-DHP) derivatives under ultrasonic irradiation in EtOH. After preparing of the nanocatalyst, its structure was confirmed by different spectroscopic methods or techniques including Fourier transform infrared (FTIR) spectroscopy, energy-dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and thermal gravimetric analysis (TGA). The performance of Fe₃O₄@SiO₂@PTS-APG nanomaterial, as a heterogeneous catalyst for the Hantzsch condensation, was examined under ultrasonic irradiation and various conditions. The yield of products was controlled under various conditions to reach more than 84% in just 10 min, which indicates the high performance of the nanocatalyst along with the synergistic effect of ultrasonic irradiation. The structure of the products was identified by melting point as well as FTIR and ¹H NMR spectroscopic methods. The Fe₃O₄@SiO₂@PTS-APG nanocatalyst is easily prepared from commercially available, lower toxic and thermally stable precursors through a cost-effective, highly efficient and environmentally friendly procedure. The advantages of this method include simplicity of the operation, reaction under mild conditions, the use of an environmentally benign irradiation source, obtaining pure products with high efficiency in short reaction times without using a tedious path, which all of them address important green chemistry principles. Finally, a reasonable mechanism is proposed for the preparation of polyhydroquinoline (PHQ) and 1,4-dihydropyridine (1,4-DHP) derivatives in the presence of Fe₃O₄@SiO₂@PTS-APG bifunctional magnetic nanocatalyst.

CuO-decorated magnetite-reduced graphene oxide: a robust and promising heterogeneous catalyst for the oxidative amidation of methylarenes in water via benzylic sp3 C–H activation

CuO-decorated magnetite-reduced graphene oxide: a heterogeneous catalyst for the oxidative amidation of methylarenes in water at room temperature.

Chitosan-encapsulated manganese ferrite particles bearing sulfonic acid group catalyzed efficient synthesis of spiro indenoquinoxalines

A simple, highly versatile and efficient synthesis of 5-phenyl-spiro[diindenopyridine-indenoquinoxaline]-diones is achieved through a four-component one pot reaction of ninhydrin, 1,2-diaminobenzene, 1,3-indandione and aniline. This reaction was catalyzed by MnFe₂O₄@CS-Bu-SO₃H MNPs as a very efficient, recyclable heterogeneous catalyst in acetonitrile under reflux conditions. The catalyst can be recovered from the subsequent reaction mixture and reused for at least five cycles without any appreciable loss in its efficiency. The core–shell structure and composition of the produced magnetic nanocatalyst were analyzed using FT-IR, XRD, VSM, SEM, EDX and TGA techniques.

A simply, highly versatile and efficient synthesis of 5-phenyl-spiro [diindeno pyridineindenoquinoxaline]-diones is achieved through five component one pot reaction of ninhydrin, 1,2-diaminobenzene, 1,3-indandione and anilines.

DABA MNPs: a new and efficient magnetic bifunctional nanocatalyst for the green synthesis of biologically active pyrano[2,3-c]pyrazole and benzylpyrazolyl coumarin derivatives

A new core–shell magnetic silica functionalized with 3,4-diaminobenzoic acid nanocatalyst (Fe₃O₄@SiO₂@PTS-DABA) was prepared and characterized. The Fe₃O₄@SiO₂@PTS-DABA catalyst was applied for the synthesis of dihydropyranopyrazole and benzylpyrazolyl coumarin derivatives.

A new bifunctional heterogeneous nanocatalyst for one-pot reduction-Schiff base condensation and reduction–carbonylation of nitroarenes

In this work, synthesis of Pd–NHC-γ-Fe₂O₃-n-butyl-SO₃H and its activity as a bifunctional heterogeneous nanocatalyst containing Pd–NHC and acidic functional groups, are described. This newly synthesized nanomagnetic catalyst is fully characterized by different methods such as FT-IR, XPS, TEM, VSM, ICP and TG analysis. At first, the catalytic activity of Pd–NHC-γ-Fe₂O₃-n-butyl-SO₃H is evaluated for the reduction of nitroarenes in aqueous media using NaBH₄ as a clean source of hydrogen generation at ambient temperature. Using the promising results obtained from the nitroarene reduction, this catalytic system is used for two one-pot protocols including reduction-Schiff base condensation and reduction–carbonylation of various nitroarenes. In these reactions the in situ formed amines are further reacted with aldehydes to yield imines or carbonylated to amides. The desired products are obtained in good to high yields in the presence of Pd–NHC-γ-Fe₂O₃-n-butyl-SO₃H as a bifunctional catalyst. The catalyst is reused with the aid of a magnetic bar for up to six consecutive cycles without any drastic loss of its catalytic activity.

This paper presents synthesis of Pd–NHC-γ-Fe₂O₃-n-butyl-SO₃H and its activity as bifunctional heterogeneous nanocatalyst containing Pd–NHC and acidic functional groups.

Superparamagnetic nanoparticle-catalyzed coupling of 2-amino pyridines/pyrimidines with trans-chalcones

An aerobic coupling of 2-aminopyrimidines or 2-aminopyridines with trans-chalcones to afford aroylimidazo[1,2-a]pyrimidines and aroylimidazo[1,2-a]pyridines is reported. Reactions proceed in the presence of CuFe₂O₄ superparamagnetic nanoparticle catalyst, two equivalents of iodine, oxygen oxidant, and 1,4-dioxane solvent. The catalyst is superior to many common copper or iron complexes. Copper ferrite could be easily separated by magnetic decantation and reused up to 5 times without a major loss of activity. The method described here marks a rare example of using a simple, heterogeneous catalyst for synthesis of fused heterocycles. To our best knowledge, aroylimidazo[1,2-a]pyrimidines and aroylimidazo[1,2-a]pyridines were not previously synthesized using this protocol.

An aerobic coupling of 2-aminopyrimidines or 2-aminopyridines with trans-chalcones to afford aroylimidazo[1,2-a]pyrimidines and aroylimidazo[1,2-a]pyridines is reported.

A magnetic nanoparticle-supported N-heterocyclic carbene-palladacycle: an efficient and recyclable solid molecular catalyst for Suzuki-Miyaura cross-coupling of 9-chloroacridine

A robust magnetic nanoparticle-supported N-heterocyclic carbene-palladacycle has been readily synthesized by directly anchoring the structural defined acenaphthoimidazolylidene palladacycle with a long tail on magnetic nanoparticles (MNPs), and functioned as a solid molecular catalyst and exhibited extremely high catalytic activity towards the challenging Suzuki-Miyaura cross-coupling reactions between less-studied heterocyclic 9-chloroacridine and diverse boronic acids. Remarkably, the catalyst could be used 5 times without obvious loss of activity highlighting the efficiency of our strategy of immobilization of previledged catalysts.

Synthesis of triphenylamines via ligand-free selective ring-opening of benzoxazoles or benzothiazoles under superparamagnetic nanoparticle catalysis

Synthesis of triphenylamines via ligand-free selective ring-opening of benzoxazoles or benzothiazoles with aryl halides under CuFe₂O₄ superparamagnetic nanoparticle catalysis.

Activated nanostructured bimetallic catalysts for C–C coupling reactions: recent progress

This minireview highlights the recent progress made in the last decade towards the development of activated bimetallic alloy nanoparticle catalysts for C–C coupling reactions, including asymmetric C–C bond coupling reactions.

Reduction of selective polyaromatic nitrotriptycene via an azoxytriptycene intermediate under ambient conditions using a cobalt/cobalt oxide nanocomposite (CoNC)

Selectively targeted polyaromatic 2-nitrotriptycene (M1) and 2,6,14-trinitrotriptycene (M2) were chosen as model substrates for demonstrating catalytic hydrogenation, under ambient conditions, using a cobalt/cobalt oxide based nanocomposite (CoNC) as the catalytic material.

Nanoparticle supported, magnetically separable manganese porphyrin as an efficient retrievable nanocatalyst in hydrocarbon oxidation reactions

Magnetically separable manganese porphyrin was prepared by immobilizing on functionalized magnetic nanoparticles via the amino propyl linkage and used as an efficient retrievable nanocatalyst in hydrocarbon oxidation reactions.

Synergistic cascade catalysis by metal nanoparticles and Lewis acids in hydrogen autotransfer

Of the many types of catalysis involving two or more catalysts, synergistic catalysis is of great interest because novel reactions or reaction pathways may be discovered when there is synergy between the catalysts. Herein, we describe a synergistic cascade catalysis, in which immobilized Au/Pd bimetallic nanoparticles and Lewis acids work in tandem to achieve the N-alkylation of primary amides to secondary amides with alcohols via hydrogen autotransfer. When Au/Pd nanoparticles were used with metal triflates, a significant rate acceleration was observed, and the desired secondary amides were obtained in excellent yields. The metal triflate is thought to not only facilitate the addition of primary amides to aldehydes generated in situ, but also enhance the returning of hydrogen from nanoparticles to hydrogen-accepting intermediates. This resulted in a more rapid turnover of the nanoparticle catalyst, and ultimately translated into an increase in the overall rate of the reaction. The two catalysts in this co-catalytic system work in a synergistic and cascade fashion, resulting in an efficient hydrogen autotransfer process.

C-H arylation of triphenylene, naphthalene and related arenes using Pd/C

A highly selective arylation of a number of polyaromatic hydrocarbons (PAHs) with aryliodonium salts and Pd/C as the only reagent is reported. The first C-H functionalization of triphenylene is explored, and proceeds at the most sterically hindered position. This non-chelate assisted C-H functionalization extends the reactivity profile of Pd/C and provides controlled access to π-extended PAHs, an important aspect of work towards the preparation of nanographenes. Mechanistic studies suggest in situ formation of catalytically active insoluble nanoparticles, and that the reaction likely proceeds via a Pd(0)/Pd(ii) type reaction manifold.

Magnetically recoverable chitosan-stabilised copper–iron oxide nanocomposite material as an efficient heterogeneous catalyst for azide–alkyne cycloaddition reactions

Chitosan-stabilised copper–iron oxide nanocomposite material is found to be a very efficient recyclable/reusable heterogeneous catalyst for azide–alkyne cycloaddition reactions under mild conditions.

Fe3O4@SiO2·HM·SO3H as a recyclable heterogeneous nanocatalyst for the microwave-promoted synthesis of 2,4,5-trisubstituted imidazoles under solvent free conditions

A simple, highly versatile and efficient synthesis of 2,4,5-trisubstituted imidazoles catalyzed by Fe₃O₄@SiO₂·HM·SO₃H is achieved via a three component one pot reaction of benzil, benzaldehyde and NH₄OAc.

Efficient magnetic and recyclable SBILC (supported basic ionic liquid catalyst)-based heterogeneous organocatalysts for the asymmetric epoxidation of trans-methylcinnamate

A green heterogeneous catalytic alternative was developed for the asymmetric epoxidation of trans-methylcinnamate to (2R,3S)-phenyl glycidate.