Supramolecular Fe3O4@PEG/−diaza crown ether@Ni: a novel magnetically reusable nano catalyst for the clean synthesis of 2‐aryl‐2,3‐dihydroquinazolin‐4(1H)‐ones

Ni@diaza crown ether complex supported on magnetic nanoparticle was provided by grafting technique. The catalytic activity of Fe₃O₄@diaza crown ether@Ni was explored through one‐pot synthesis of 2,3‐dihydroquinazolin‐4(1H)‐ones and it was used as an efficient and recoverably constant nanocatalyst. FT‐IR, SEM, TEM, XRD, BET, ICP, EDS, and TGA techniques were employed to specify the nanocatalyst. This heterogeneous catalyst demonstrated acceptable recyclability and could be used again several times with no considerable loss of its catalytic activity.     

Synthesis and characterization of copper(II) Schiff base complex supported on Fe3O4 magnetic nanoparticles: a recyclable catalyst for the one‐pot synthesis of 2,3‐dihydroquinazolin‐4(1H)‐ones

Fe₃O₄–Schiff base of Cu(II) is found to be a recyclable and heterogeneous catalyst for the rapid and efficient synthesis of various 2,3‐dihydroquinazolin‐4(1H)‐one derivatives from the two‐component condensation of 2‐aminobenzamide and an aldehyde. This reaction is simple, green and cost‐effective. Separation and recycling can also be easily done by magnetic decantation of the Fe₃O₄ nanoparticles with an external magnet. The prepared catalyst was characterized using thermogravimetry, Fourier transform infrared spectroscopy, vibrating sample magnetometry, inductively coupled plasma analysis, X‐ray diffraction and scanning electron microscopy. Copyright © 2015 John Wiley & Sons, Ltd.     

Cu(II) immobilized on guanidinated epibromohydrin‐functionalized γ‐Fe2O3@TiO2 (γ‐Fe2O3@TiO2‐EG‐Cu(II)): A highly efficient magnetically separable heterogeneous nanocatalyst for one‐pot synthesis of highly substituted imidazoles

A simple, efficient and eco‐friendly procedure has been developed using Cu(II) immobilized on guanidinated epibromohydrin‐functionalized γ‐Fe₂O₃@TiO₂ (γ‐Fe₂O₃@TiO₂‐EG‐Cu(II)) for the synthesis of 2,4,5‐trisubstituted and 1,2,4,5‐tetrasubstituted imidazoles, via the condensation reactions of various aldehydes with benzil and ammonium acetate or ammonium acetate and amines, under solvent‐free conditions. High‐resolution transmission electron microscopy analysis of this catalyst clearly affirmed the formation of a γ‐Fe₂O₃ core and a TiO₂ shell, with mean sizes of about 10–20 and 5–10 nm, respectively. These data were in very good agreement with X‐ray crystallographic measurements (13 and 7 nm). Moreover, magnetization measurements revealed that both γ‐Fe₂O₃@TiO₂ and γ‐Fe₂O₃@TiO₂‐EG‐Cu(II) had superparamagnetic behaviour with saturation magnetization of 23.79 and 22.12 emu g^?1, respectively. γ‐Fe₂O₃@TiO₂‐EG‐Cu(II) was found to be a green and highly efficient nanocatalyst, which could be easily handled, recovered and reused several times without significant loss of its activity. The scope of the presented methodology is quite broad; a variety of aldehydes as well as amines have been shown to be viable substrates. A mechanism for the cyclocondensation reaction has also been proposed.     

CoFe2O4@SiO2‐CPTES‐Guanidine‐Cu(II): A novel and reusable nanocatalyst for the synthesis of 2,3‐dihydroquinazolin‐4(1H)‐ones and polyhydroquinolines and oxidation of sulfides

CoFe₂O₄@SiO₂‐CPTES‐Guanidine‐Cu(II) magnetic nanoparticles were synthesized and used as a new, inexpensive and efficient heterogeneous catalyst for the synthesis of polyhydroquinolines and 2,3‐dihydroquinazoline‐4(1H)‐ones and for the oxidation of sulfides. The structure of this nanocatalyst was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, vibrating sample magnetometry, thermogravimetric analysis, X‐ray diffraction and inductively coupled plasma optical emission spectrometry. Simple preparation, high catalytic activity, simple operation, high yields, use of green solvents, easy magnetic separation and reusability of the catalyst are some of the advantages of this protocol.     

Magnetic Fe3O4 nanoparticles supported imine/Thiophene‐nickel (II) complex: A new and highly active heterogeneous catalyst for the synthesis of polyhydroquinolines and 2, 3‐dihydroquinazoline‐4(1H)‐ones

A new magnetically separable nickel catalyst (Ni(NO₃)_2?Imine/Thiophene‐Fe₃O₄@SiO₂) was readily prepared and structurally characterized by Fourier transform infrared spectroscopy (FT‐IR), Scanning electron microscopy (SEM), Energy‐dispersive X‐ray spectroscopy (EDX), Vibrating sample magnetometer (VSM), X‐Ray diffraction (XRD) and Atomic absorption spectroscopy (AAS). The Ni(NO₃)_2?Imine/Thiophene‐Fe₃O₄@SiO₂ exhibited efficient catalytic activity in the synthesis of 2,3‐dihydroquinazoline‐4(1H)‐ones and polyhydroquinolines. Catalysis research under water and solvent‐free conditions makes also this synthetic protocol ideal and fascinating from the environmental point of view. The catalyst can be magnetically recovered after the reaction and can be reused for many times without appreciable decrease in activity.     

Copper(I) complex of 1,3‐DimethylBarbituric acid modified SBA‐15 and its catalytic role for the synthesis of 2,3‐Dihydroquinazolin‐4(1H)‐ones and Imidazoles

An efficient one‐pot method for synthesis of 2,3‐dihydroquinazolin‐4(1H)‐ones and tri/tetra substituted‐1H‐imidazoles has been accomplished in the presence of catalytic amounts of Cu(I)‐1,3‐dimethylbarbituric acid modified SBA‐15 as heterogeneous catalyst with good to excellent yields. The catalyst is reusable and can be applied several times without any decrease in product yield. The synthesized catalyst was characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD), energy dispersive X‐ray spectroscopy (EDS), thermal gravimetric analysis (TGA), N₂ adsorption/desorption isotherms (BET), Fourier transform infrared spectroscopy (FT‐IR) and atomic absorption spectroscopy (AAS).     

Synthesis and characterization of bromine source supported on magnetic Fe3O4 nanoparticles: A new,versatile and efficient magnetically separable catalyst for organic synthesis

Tribenzylammonium tribromide supported onto magnetic nanoparticles (Br₃‐TBA‐Fe₃O₄) as a bromine source was successfully synthesized and characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, X‐ray diffraction, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy and vibrating sample magnetometry. The synthesized catalyst is shown to be a versatile and highly efficient heterogeneous catalyst for the Knoevenagel condensation and synthesis of 2,3‐dihydroquinazolin‐4(1H )‐one and polyhydroquinoline derivatives. To the best of the authors' knowledge, this is the first report of the use of a bromine source immobilized on Fe₃O₄ nanoparticles as a magnetically separable catalyst for these reactions. The nanosolid catalyst can be magnetically recovered and reused readily several times without significant loss in catalytic efficiency.     

Eco‐friendly and Efficient Synthesis of 2,3‐Dihydroquinazolin‐4(1H)‐ones

A simple and facile method for the synthesis of 2,3‐dihydroquinazolin‐4(1H)‐ones through the direct cyclocondensation of one‐pot three‐component cyclocondensation of isatoic anhydride, ammonium acetate (or primary amines) and aldehydes; and anthranilamide and aldehydes using silica supported ferric chloride (SiO₂‐FeCl₃) as catalyst under solvent‐free conditions is described.     

Sulfamic acid immobilized on amino‐functionalized magnetic nanoparticles: A new and active magnetically recoverable catalyst for the synthesis of N‐heterocyclic compounds

Sulfamic acid immobilized on amino‐functionalized magnetic nanoparticles (MNPs/DETA‐SA) was successfully fabricated and characterized using various techniques. Diameters of approximately 15 nm for the MNPs/DETA‐SA were observed from scanning electron microscopy images. The as‐fabricated nanocomposite was applied as an efficient and magnetically reusable catalyst for the synthesis of 2,3‐dihydroquinazoline‐4(1H)‐one and polyhydroquinoline derivatives. All products were obtained in good to excellent yields. Recovery tests confirm that the catalyst can be readily recovered using an external magnet and reused many times without significant loss of its catalytic activity.     

Synthesis of Fe3O4@SiO2@DOPisatin‐Ni(II) and Cu(II) nanoparticles: Highly efficient catalyst for the synthesis of sulfoxides and disulfides

The catalytic activity of two magnetic catalysts Fe₃O₄@SiO₂@DOPisatin‐M(II) (M = Ni, Cu) was investigated in the environmentally green H₂O₂ oxidant‐based oxidation of sulfides to sulfoxides and oxidative coupling of thiols to disulfides. By using these catalysts, various substrates were successfully converted into their corresponding product. These catalysts could also be reused multiple time without significant loss of activity. The physical and chemical properties of the catalysts were determined using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), energy dispersive X‐ray spectroscopy (EDX) and atomic absorption spectroscopy (AAS).     

Synthesis of 2‐Aryl‐2,3‐dihydro‐1,8‐naphthyridin‐4(1H)‐ones by Deprotective Cyclization of N‐{3‐[(2E)‐3‐Arylprop‐2‐enoyl]pyridin‐2‐yl}‐2,2‐dimethylpropanamides in Water

A new and convenient method for the preparation of 2‐aryl‐2,3‐dihydro‐1,8‐naphthyridin‐4(1H)‐ones 4 has been developed. Thus, N‐{3‐[(2E)‐3‐arylprop‐2‐enoyl]pyridin‐2‐yl}‐2,2‐dimethylpropanamides 3 are synthesized from commercially available pyridin‐2‐amine using an easily performed three‐step sequence and are subjected to cyclization with deprotection under acidic conditions in H₂O to give the desired products. Similarly, 2‐aryl‐2,3‐dihydro‐1,7‐naphthyridin‐4(1H)‐ones 8 and 2‐aryl‐2,3‐dihydro‐1,6‐naphthyridin‐4(1H)‐ones 12 can be prepared from pyridin‐3‐amine and pyridin‐4‐amine, respectively.     

Magnetically recyclable palladium nanoparticles (Fe3O4‐Pd) for oxidative coupling between amides and olefins at room temperature

A convenient method for the synthesis of magnetically recyclable palladium nanoparticles (Fe₃O₄‐Pd) is described. The catalytic application of the Fe₃O₄‐Pd nanoparticles was explored for the first time in oxidative coupling between amides and olefins. p‐Toluenesulfonic acid plays a significant role in the oxidative amidation reaction. The reaction proceeds at room temperature, resulting in (Z)‐enamides under ambient air in the absence of co‐catalyst and ligand. The superparamagnetic nature of Fe₃O₄‐Pd facilitates easy, quantitative recovery of the catalyst from a reaction mixture, and it can be reused for up to three consecutive cycles with a slight decrease in catalytic activity.     

Copper(II)‐Catalyzed Tandem Synthesis of Substituted 3‐Methyleneisoindolin‐1‐ones

An efficient strategy for the synthesis of a variety of 3‐methyleneisoindolin‐1‐ones has been developed. The reaction proceeded from coupling of 2‐iodobenzamides (or 2‐bromobenzamides) and terminal alkynes via Cu(OAc)₂·H₂O/2,2′‐biimidazole catalyzed in DMF at 60°C and subsequent additive cyclization produced substituted 3‐methyleneisoindolin‐1‐ones in good to excellent yields.     

Cp2ZrCl2‐catalyzed synthesis of 2‐substituted quinozolin‐4(3H)‐ones

Zirconocene dichloride (Cp₂ZrCl₂) in the presence of DMF was found to be a highly efficient catalyst for the synthesis of structurally diverse 2‐substituted quinozolin‐4(3H)‐ones by reaction of anthranilimide with a wide range of aryl aldehydes. Copyright © 2013 John Wiley & Sons, Ltd.     

Silica‐bonded S‐sulfonic Acid as a Recyclable Catalyst for Synthesis of 2,3‐Dihydroquinazolin‐4(1H)‐ones

2,3‐Dihydroquinazolin‐4(1H)‐one derivatives were synthesized via a one‐pot, three component reaction of isatoic anhydride and an aromatic aldehyde with ammonium acetate or primary amine catalyzed by silica‐bonded S‐sulfonic acid in ethanol at 80°C. The reaction work‐up is simple and the catalyst is easily separated from the products by filtration. The heterogeneous catalyst was recycled for ten runs upon the condensation reaction of isatoic anhydride and 4‐chlorobenzaldehyde with ammonium acetate without losing its catalytic activity.     

Copper(II)‐Catalyzed Synthesis of N‐Substituted‐3‐amino‐4‐cyano‐isoquinoline‐1(2H)‐ones by the Reaction of N‐Substituted‐2‐iodobenzamides with Malononitrile

A novel Cu(OAc)₂·H₂O catalyzed coupling reaction of N‐substituted‐2‐iodobenzamides with malononitrile to afford N‐substituted‐3‐amino‐4‐cyano‐isoquinoline‐1(2H)‐ones is described. The reaction proceeded in DMSO at 90°C for 5 h in nitrogen without external ligands.     

Isatin‐SO3H coated on amino propyl modified magnetic nanoparticles (Fe3O4@APTES@isatin‐SO3H) as a recyclable magnetic nanoparticle for the simple and rapid synthesis of pyrano[2,3‐d] pyrimidines derivatives

Isatin‐SO₃H coated on amino propyl modified magnetic nanoparticles (Fe₃O₄@APTES@isatin‐SO₃H) is found to be a novel, efficient, and reusable magnetic nanocatalyst, and characterized by FT‐IR, SEM, TEM, XRD, EDX, VSM, and TGA analysis. The magnetic nanocatalyst demonstrated outstanding performance in synthesis of pyrano[2,3‐d] pyrimidines derivatives via one‐pot three‐component reaction of various aromatic aldehydes 1, malononitrile 2, and barbituric acid 3 under reflux conditions in mixture of H₂O:EtOH (1:1) as solvent. Easy workup procedure, short reaction time, high yield, simple preparation and easy recovery of the catalyst, mild reaction conditions are some advantages of this work.     

Efficient Synthesis of 2‐(2‐Aminophenyl)‐2,3‐dihydropyridin‐4(1H)‐ones Based on a Cyclization/Ring Cleavage Procedure

(Benzyloxycarbonyl)‐protected 3,4‐benzo‐7‐hydroxy‐2,9‐diazabicyclo[3.3.1]non‐7‐enes were prepared by one‐pot cyclizations of 1,3‐bis(silyl enol ethers) with quinazolines. Subsequent hydrogenation resulted in one‐pot deprotection and rearrangement to give 2‐(2‐aminophenyl)‐2,3‐dihydropyridin‐4(1H)‐ones.     

Magnetized inorganic–bioorganic nanohybrid [nano Fe3O4‐SiO2@Glu‐Cu (II)]: A novel nanostructure for the efficient solvent‐free synthesis of thiazolidin‐2‐imines

In this research, a solvent‐free four‐component one‐pot reaction of phenyl isothiocyanate, phenylacetylene, various kinds of aldehydes, and amines was interpreted to obtain the desired five‐membered heterocycles named thiazolidin‐2‐imines. The promotor of this transformation is a novel magnetite‐based multilayered inorganic–bioorganic nanohybrid prepared via embedding glutamic acid on the magnetized silica followed by anchoring Cu (II) [nano Fe₃O₄‐SiO₂@Glu‐Cu (II)]. The newly synthesized nanostructure is characterized through Fourier‐transform infrared (FT‐IR), field‐emission scanning electron microscopy (FESEM), energy dispersive X‐ray analysis (EDAX), transmission electron microscopy (TEM), X‐ray fluorescence (XRF), thermogravimetric analysis or derivative thermogravimetric (TGA/DTG), vibrating sample magnetometer (VSM), X‐ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) techniques. This protocol is a straightforward one‐step procedure to obtain thiazolidin‐2‐imines without requirement to propargylamines or imines as substrates. In addition, easy work‐up procedure, high yields of products, absence of organic solvents in the reaction media, recovery and reusability of nano Fe₃O₄‐SiO₂@Glu‐Cu ( II) to promote the reaction at least for three runs without activity lost, simple separation of the catalyst from reaction mixture via an external magnet, and regioselectivity of the method are some highlighted aspects of the approach.     

Ring Opening of 2‐(Benzylamino)‐2H‐1,4‐benzoxazin‐3(4H)‐ones and 2‐Bromo‐2H‐1,4‐benzoxazin‐3(4H)‐ones

Substituted 2‐(benzylamino)‐2H‐1,4‐benzoxazin‐3(4H)‐ones are unstable under alkaline and acidic conditions, undergoing opening of the benzoxazinone ring. 2‐Bromo‐2H‐1,4‐benzoxazin‐3(4H)‐ones show similar degradation under alkaline conditions, while replacement of Br at C(2) to give 2‐hydroxy‐2H‐1,4‐benzoxazin‐3(4H)‐ones was observed only under mild alkaline conditions. Mechanisms of ring opening and degradation to 2‐aminophenol derivatives are proposed.