H5BW12O40 as a green and efficient homogeneous but recyclable catalyst in the synthesis of 4H‐Pyrans via multicomponent reaction

Keggin‐type heteropolyacid, H₅BW₁₂O₄₀ (BWA) with a higher negative charge and stronger Brønsted acidity comparing to Si and P derivatives was used as an efficient, green, and reusable catalyst in a three‐component reaction involving the cyclocondensation of various β‐dicarbonyl compounds, differently substituted aromatic aldehydes and malononitrile in EtOH/H₂O for the facile, clean, and high yielding synthesis of 4H‐pyrans. All reactions were completed in short times and the products were obtained in good to excellent yields. The reaction medium could be recycled and reused several times without any loss of efficiency.     

H3PMo12O40‐immobilized chitosan/Co3O4: A novel and recyclable nanocomposite for the synthesis of pyrimidinedione derivatives

An efficient three‐component reaction of aromatic aldehydes, 6‐aminouracil/6‐amino‐1,3‐dimethyluracil and 4‐hydroxycoumarin in the presence of a novel heterogeneous catalyst H₃PMo₁₂O₄₀‐immobilized Co₃O₄/chitosan led to a synthesis of a new class of pyrimidinedione derivatives under reflux conditions. The magnetically recoverable nanocomposite of Co₃O₄/chitosan/H₃PMo₁₂O₄₀ was fully characterized by Fourier transform‐infrared spectrophotometry, scanning electron microscopy, X‐ray powder diffraction, energy‐dispersive X‐ray spectroscopy, vibrating‐sample magnetometry and N₂ adsorption–desorption by Brunauer–Emmett–Teller analysis. Results show that Keggin‐type 12‐molybdophosphoric acid immobilized into the network of the cross‐linked chitosan with super‐paramagnetic Co₃O₄ nanoparticles. The present method offers several advantages, such as simple procedure, short reaction times and excellent yields of products. The novelty of the catalyst, high catalytic activity, easy separation from the reaction with an external magnetic field and reusability of the catalyst in six consecutive runs are additional eco‐friendly attributes of this catalytic system.     

Preparation and characterization of new inorganic–organic hybrid catalyst H3PMo12O40/Hyd‐SBA‐15 and its application in the domino multi‐component reaction

We present novel inorganic–organic hybrid catalyst to accomplish domino multi‐component reaction (MCR) for synthesis of 3‐amino‐2′‐oxospiro[benzo[c]pyrano[3,2‐a]phenazine‐1,3′‐indoline]‐2‐carbonitrile/carboxylate derivatives. This methodology offers remarkable development by easy production of H₃PMo₁₂O₄₀/Hyd‐SBA‐15 in regard to solving the problem of using harsh catalysts, also it demonstrates to be impressive and environmentally friendly in term of low reaction times and high yields.     

H3PW12O40@nano‐ZnO: An efficient,recyclable, and eco‐friendly catalyst for the green synthesis of novel benzo[a]pyrimido[5′,4′:5,6]pyrano[2,3‐c]phenazines via sequential multicomponent reactions under microwave irradiation

A simple, efficient, single‐pot synthesis of novel heteroaryl‐substituted benzo[a]pyrimido[5′,4′:5,6]pyrano[2,3‐c]phenazines has been developed via initial Knoevenagel, subsequent Michael, and final heterocyclization reactions of 2‐hydroxynaphthalene‐1,4‐dione, o‐phenylenediamine, aromatic aldehydes, and barbituric acid in the presence of H₃PW₁₂O₄₀@nano‐ZnO as a recyclable heterogeneous catalyst in EtOH under microwave irradiation (MWI). This sequential green process with several advantages, such as operational simplicity, high yield, low cost, easy handling, eco‐friendliness and reusability of the catalyst, absence of any tedious work‐up or purification, and avoidance of hazardous or toxic reagents/catalysts/solvents, opens an effective and convenient way to pyrano‐functionalized benzophenazine systems, which are promising compounds for different biomedical applications.     

Synthesis and characterization of the novel diamine‐functionalized Fe3O4@SiO2 nanocatalyst and its application for one‐pot three‐component synthesis of chromenes

Fe₃O₄@SiO₂@propyltriethoxysilane@o‐phenylendiamine as an environmentally‐benign functionalized silica‐coated magnetic organometallic nanomaterial has been synthesized and characterized by Fourier transforms infrared (FT‐IR) spectroscopy, scanning electron microscopy (SEM) images and energy dispersive X‐ray (EDX) and vibrating sample magnetometer (VSM) analyses. Then, its catalytic activity was investigated for the one‐pot three‐component condensation reaction between dimedone, malononitrile and various substituted aromatic aldehydes to afford the corresponding 2‐amino‐4H‐chromene derivatives under mild reaction conditions. This nanocatalyst can be easily recovered from the reaction mixture by using a magnet and reused for at least five times without significant decrease in catalytic activity.     

Polypyrrole/Fe3O4/CNT as a recyclable and highly efficient catalyst for one‐pot three‐component synthesis of pyran derivatives

Polypyrrole (PPY)/Fe₃O₄/CNT has been synthesized and characterized by FT‐IR, TEM and SEM techniques and its catalytic activity has been evaluated in the synthesis of several series of pyran derivatives. Tetrahydrobenzo[b]pyranes, 4H‐pyran‐3‐carboxylates, 4H,5H‐pyrano[3,2‐c]chromenes and dihydropyrano[2,3‐c]pyrazoles have been successfully prepared from one‐pot three‐component condensation of aldehyde, malononitrile and active methylene‐containing compounds (dimedone /ethyl acetoacetate/4‐hydroxycoumarin/3‐methyl‐2‐pyrazoline‐5‐one) using PPY/Fe₃O₄/CNT as a new and reusable heterogeneous catalyst. The present method offer several advantages such as; high yields of products, short reaction times, easy work‐up procedure and easy separation of the catalyst from the reaction mixture due to its magnetic character. Furthermore, chemoselective synthesis of bis‐benzo[b]pyran from terephthalaldehyde can be achieved by this method.     

Use of an efficient polystyrene‐supported cerium catalyst for one‐pot multicomponent synthesis of spiro‐piperidine derivatives and click reactions in green solvent

One‐pot multicomponent reactions are very demanding in synthetic organic chemistry. Here we report a new polystyrene‐supported cerium catalyst (PS‐Ce‐amtp) obtained via an easy two‐step procedure, which was thoroughly characterized using various techniques. PS‐Ce‐amtp catalyses the environmentally benign one‐pot multicomponent synthesis of spiro‐piperidine derivatives through the reaction of substituted aniline, cyclic active methylene compound and formaldehyde at room temperature. The catalyst also exhibits excellent catalytic activity in one‐pot synthesis of 1,4‐disubstituted 1,2,3‐triazoles via click reaction between in situ generated azides (derived from anilines and amines) and terminal alkynes. The catalyst can be recovered easily after reaction and reused five times without significant loss in its catalytic activity. The advantageous features of this catalyst are atom economy, operational simplicity, short reaction times, easy handling and high recycling efficiency.     

ZrOCl2·8H2O as an efficient and recyclable catalyst for the one‐pot multicomponent synthesis of novel [1,3]oxazino[5,6‐c]quinolin‐5‐one derivatives

A simple, efficient and eco‐friendly procedure has been developed using ZrOCl₂·8H₂O as catalyst for the synthesis of novel [1,3]oxazino[5,6‐c]quinolin‐5‐one derivatives in aqueous ethanol at room temperature. The present methodology offers several advantages such as operational simplicity, use of ZrOCl₂·8H₂O as a green, non‐toxic, inexpensive and reusable catalyst, reusability of reaction media, high yields, mild and environmentally benign reaction conditions.     

CoFe2O4@SiO2-NH2-CoII NPs catalyzed Hantzsch reaction as an efficient,reusable catalyst for the facile,green, one-pot synthesis of novel functionalized 1,4-dihydropyridine derivatives

A magnetically heterogeneous CoFe₂O₄@SiO₂-NH₂-Co^II nanoparticle was synthesized by the immobilization of Co (II) complex onto CoFe₂O₄@SiO₂ nanoparticles, and the heterogeneous magnetic nanocatalyst was characterized by XRD, TEM, TGA, EDX, and FT-IR techniques. Then, the green and reusable method was introduced for a multicomponent synthesis of 1,4-dihydropyridine derivatives via Hantszch reaction. The synthesis of 1,4-dihydropyridine derivatives was proceeded by the reaction of aldehyde, ethyl acetoacetate, and ammonium acetate in the presence of this magnetic nanocatalyst in EtOH/Water (1:1). Simple work-up, short reaction times, excellent yields (60–96%) as well as green solvent are some advantages of this novel approach, and the corresponding products were purified with no need for chromatographic separation.     

Introduction of Ag/CuO/MCM‐48 as an efficient catalyst for the one‐pot synthesis of novel pyran‐pyrrole hybrids

Bimetallic silver and copper incorporated mesoporous MCM‐48 (Ag/CuO/MCM‐48) was synthesized by simple wet‐impregnation method. The knowledge about its structural properties was gathered by means of Fourier transform‐infrared, energy‐dispersive X‐ray, X‐ray diffraction, field emission‐scanning electron microscopy, transmission electron microscopy and Brunauer–Emmett–Teller analyses. The catalytic activity of Ag/CuO/MCM‐48 was examined in the one‐pot three‐component reaction of 3‐(1‐methyl‐1H‐pyrrol‐2‐yl)‐3‐oxopropanenitrile, malononitrile and various aromatic aldehydes leading to novel pyran‐pyrrole hybrid derivatives in reduced reaction times (5–10 min) and excellent yields (88–97%). Application of Ag/CuO/MCM‐48 as a potent heterogeneous catalyst with good reusability up to five times, use of ethanol as an eco‐compatible medium and chromatography‐free work‐up are some crucial green aspects of this procedure.     

Nano n‐propylsulfonated γ‐Al2O3: a new,efficient and reusable catalyst for synthesis of spiro[indoline‐3,4‐pyrazolo[3,4‐e][1,4]thiazepine]diones in aqueous media

Nano n‐propylsulfonated γ‐Al₂O₃ is easily prepared by the reaction of nano γ‐Al₂O₃ with 1,3‐propanesultone. This reagent can be used as an efficient catalyst for the synthesis of spiro [indoline‐3,4‐pyrazolo[3,4‐e][1,4]thiazepine]diones in aqueous media. This new method consistently has the advantages of excellent yields and short reaction times. Further, the catalyst can be reused and recovered several times. Copyright © 2013 John Wiley & Sons, Ltd.     

LiBF4 integrated into [BMIm]BF4: an ionic‐liquid metal composite and homogeneous catalyst for efficient synthesis of pyran‐annulated heterocycles

The ionic liquid [BMIm]BF₄ doped with LiBF₄ was found to efficiently catalyze the three‐component reaction between isocyanides, acetylenic esters and enols or phenols at room temperature, leading to rapid synthesis of 2‐aminopyran‐annulated systems in fairly high yields. Efficiency of this catalysis and its benefits in terms of improved yields and reaction times could be ascribed to involvement of relatively stable organolithium intermediates which make the reaction more feasible. The ionic solution tolerates a significant amount of dissolved LiBF₄, while remaining fluid at room temperature to serve as solvent for the organic substrates. It retains its initial integrity after use and recovery, as it could be recycled several times without appreciable catalytic decrements. The catalytic activity of the ionic composite is completely lost in the absence of LiBF₄. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and characterization of Fe3O4@THAM-SO3H as a highly reusable nanocatalyst and its application for the synthesis of dihydropyrano[2,3-c]pyrazole derivatives

In this work, a new, green and beneficial nanomagnetic catalyst was easily fabricated using sulfuric acid as an acidic group on Fe₃O₄ nanoparticles coated with tris (hydroxymethyl) aminomethane (THAM). The synthesized catalyst was characterized by FT-IR, TGA/DTG, XRD, TEM, EDS, VSM, and SEM analyses. Next, its catalytic activity was studied for the synthesis of dihydropyrano[2,3-c]pyrazole derivatives. This catalyst has advantages such as high catalytic activity, non-toxicity, easy separation from the reaction mixture using an external magnet and reuses for several times without significantly reducing in its catalytic activity.     

Fe3O4@silica‐MCM‐41@DABCO: A novel magnetically reusable nanostructured catalyst for clean in situ synthesis of substituted 2‐aminodihydropyrano[3,2‐b]pyran‐3‐cyano

DABCO (1,4‐diazabicyclo[2.2.2]octane)‐modified magnetite with silica‐MCM‐41 shell (Fe₃O₄@silica‐MCM‐41@DABCO) as an effective, magnetic and novel heterogeneous reusable nanocatalyst was synthesized and analysed using various techniques. Evaluation of the catalytic activity of this nanocatalyst was performed in the clean synthesis of substituted 2‐aminodihydropyrano[3,2‐b]pyran‐3‐cyano in high yields via in situ reaction of azido kojic acid, malononitrile and various aldehydes.     

A one‐pot green synthesis of 2‐amino‐4H‐benzo[h]chromenes catalyzed by a dioxomolybdenum Schiff base complex supported on magnetic nanoparticles as an efficient and recyclable nanocatalyst

In this work, catalytic performance of a molybdenum Schiff base complex‐supported magnetic support as a nanocatalyst was evaluated for the preparation of 2‐amino‐4H‐benzo[h]chromenes through one‐pot, three component reactions of 1‐naphthol, various aldehydes, and malononitrile under solvent‐free conditions. A promising greener and eco‐friendly method with a short reaction time, high yield of products, and simple work‐up procedure was achieved. The nanocatalyst could be easily separated and regenerated from reaction media by an external magnet and reused at least seven consecutive times with small drops in its catalytic performance.     

Amino acid ionic liquid‐based titanomagnetite nanoparticles: An efficient and green nanocatalyst for the synthesis of 1,4‐dihydropyrano[2,3‐c]pyrazoles

The amino acid ionic liquid tetrabutylammonium asparaginate (TBAAsp) was immobilized on titanomagnetite (Fe_3?xTi_xO₄) nanoparticles in a facile one‐pot process using an organosilane compound (TMSP) as spacer. The modified Fe_3?xTi_xO₄@TMSP@TBAAsp magnetic nanoparticles were characterized using Fourier transform spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, vibrating sample magnetometry and thermogravimetric analysis. The resulting analytical data clearly verified the successful immobilization of the ionic liquid on the magnetic substrate. The magnetic ionic liquid‐based nanoparticles exhibited high catalytic activity in the synthesis of 1,4‐dihydropyrano[2,3‐c]pyrazole derivatives via a one‐pot three‐component reaction under mild reaction conditions. The catalyst was easily recycled and reused for at least six runs without any considerable loss of activity.     

Cu(II)‐supported graphene quantum dots modified NiFe2O4: A green and efficient catalyst for the synthesis of 4H‐pyrimido[2,1‐b]benzothiazoles in water

NiFe₂O₄ nanoparticles are modified by graphene quantum dots (GQDs) and utilized to stabilize the Cu(II) nanoparticles as a novel magnetically retrievable catalytic system (Cu(II)/GQDs/NiFe₂O₄) for green formation of 4H‐pyrimido[2,1‐b]benzothiazoles. The prepared catalyst can be isolated assisted by an outer magnet and recovered for five courses without significant reduction in its efficiency. The as‐prepared magnetic heterogeneous nanocomposite was characterized by UV–Vis, FT‐IR, XRD, EDS, VSM, TEM, and ICP. Performing the reactions in environmentally friendly and affordable conditions (water), the low catalyst percentage, high yield of products, short reaction times, and easy workup are the merits of this protocol.     

Fe3O4@MCM-48–SO3H:合成苯并[f]色烯并[2,3-d]嘧啶酮的高效、可磁性分离纳米催化剂（英文）

Sulfonic acid groups were grafted onto three different types of synthesized magnetic nanoparticles, namely Fe3O4, Fe3O4@SiO2, and Fe3O4@MCM‐48. The sulfonic acid‐functionalized nanoparticles were evaluated as catalysts for the synthesis of 5‐aryl‐1H‐benzo[f]chromeno[2,3‐d]pyrimidine‐2,4(3H,5H)‐dione derivatives in terms of activity and recyclability. Their catalytic activities were compared with that of the homogeneous acid catalyst 1‐methylimidazolium hydrogen sulfate ([HMIm][HSO4]). The activity of Fe3O4@MCM‐48–SO3H was comparable to those of the other heter‐ogeneous and homogeneous catalysts.     

Fe3O4@MCM-48-SO3H:An efficient magnetically separable nanocatalyst for the synthesis of benzo[f]chromeno[2,3-d]pyrimidinones

Sulfonic acid groups were grafted onto three different types of synthesized magnetic nanoparticles, namely Fe3O4, Fe3O4@SiO2, and Fe3O4@MCM‐48. The sulfonic acid‐functionalized nanoparticles were evalu...     

An efficient synthesis of novel pyridothieno-fused thiazolo[3,2-a]pyrimidinones via Pictet–Spengler reaction

An efficient method for the synthesis of novel pyrido[3',2':4',5']thieno[3',2':2,3]pyrido [4,5:d][1,3]thiazolo[3,2-a]pyrimidine-4-one derivatives (5) has been developed using a Pictet-Spengler reaction between 2-(3-aminothieno[2,3-b]pyridin-2-yl)thiazolo[3,2-a] pyrimidin-5-one (3), which could be obtained from the condensation of 7-(chloromethyl)-5H-thiazolo[3,2-a]pyrimidin-5-one (1) with 3-cyanopyridine-2-thione (2) via Thorpe-Ziegler isomerization, and aromatic aldehydes under NH₂SO₃H as catalysis in good yields.