Guanine-La complex supported onto SBA-15: A novel efficient heterogeneous mesoporous nanocatalyst for one-pot,multi-component Tandem Knoevenagel condensation–Michael addition–cyclization Reactions

In this work, we present a simple, environmentally-friendly and economical route for the preparation of a novel lanthanum (III) organometallic complex immobilized onto a highly stable mesoporous silica SBA-15 (La-guanine@SBA-15) using an inexpensive and simple method and available materials. This mesoporous heterogenized complex was comprehensively characterized using FT-IR, XRD, EDS, ICP, MAP, SEM, TGA and BET techniques. The catalytic activity of this mesoporous material was studied in one-pot multi-component tandem Knoevenagel condensation–Michael addition–cyclization reactions in order to prepare a series of benzo [a] pyrano [2, 3-c] phenazine and 4,4′-(arylmethylene)-bis-(3-methyl-1-phenyl-1H-pyrazol-5-ols) derivatives under green conditions. This catalyst exhibited highly recoverable and recyclable features in consecutive reaction runs. Besides, the products were obtained in high yields and short reaction times. In this sense, simple preparation of the catalyst from the commercially available materials, simple operation, high catalytic activity, short reaction times, high yields and the use of green reaction conditions in the mentioned organic synthesis are the most significant advantages of this protocol. In addition, this nanocatalyst was easily recovered, using simple filtration, and reused several times without significant loss of its catalytic efficiency. Moreover, the leaching, heterogeneity and stability of La-guanine@SBA-15 were studied by hot filtration test and ICP technique. Finally, stability of the catalyst after recycling was confirmed by SEM and FT-IR techniques.     

Novel thiophosphonodiamides as efficient hydrogen bond donor catalysts in tandem Michael addition–cyclization of malononitrile and 2-(E)-2-nitrovinylphenols

From l-amino acid, three chiral thiophosphonodiamides were prepared as new hydrogen bond donor organocatalysts. Under the mediation of the catalyst derived from l-valine, a tandem Michael addition/cyclization reaction between (E)-2-(2-nitrovinyl)phenols and malononitrile proceeds smoothly, giving pharmaceutically valuable 2-amino-4H-chromene-3-carbonitriles in high yields with 66–95% ee within 2 h.     

α-Fe_2O_3 nanoparticles:An efficient,inexpensive catalyst for the one-pot preparation of 3,4-dihydropyrano[c]chromenes

This paper describes the combustion synthesis ofα-Fe₂O₃ nanopowder at much lower temperature and its catalytic activity for the one-pot preparation of 3,4-dihydropyrano[c]chromenes.The combustion derivedα-Fe₂O₃ nanopowder was characterized by powder X-ray diffraction（PXRD）,Braunauer,Emmett and Teller（BET） surface area,scanning electron microscopy（SEM） and Fourier transform infrared spectroscopy（FTIR）.Highly efficient,three-component condensation of aromatic aldehyde,malanonitrile and 4- hydroxycoumarin catalyzed byα-Fe₂O₃ nanoparticles at room temperature is described.The method offers an excellent alternative to the synthesis of 3,4-dihydropyrano[c]chromenes.The reactions are rapid,clean,and the products with good yield and high purity.     

Imidazole-functionalized magnetic Fe3O4 nanoparticles: an efficient,green, recyclable catalyst for one-pot Friedländer quinoline synthesis

Research on Chemical Intermediates - An efficient and cost-effective procedure for preparation of Fe3O4 nanoparticles and supported Brønsted acidic ionic liquid...     

Magnetic nanoparticle-supported eosin Y ammonium salt: An efficient heterogeneous catalyst for visible light oxidative C–C and C–P bond formation

A highly efficient visible light mediated C–C and C–P coupling reactions of sp³ C–H bonds adjacent to the nitrogen atom in tetrahydroisoquinoline derivatives with pronucleophiles such as nitroalkanes, malononitrile, dimethyl malonate and H-phosphonate diesters were achieved by using a magnetic nanoparticle-supported eosin Y bis-benzyltriethylammonium salt (MNPs-Eosin Y) as catalyst and air as the sole oxidant, affording the corresponding products in good to excellent yields under mild reaction conditions. Notably, the supported eosin Y catalyst can easily be separated from the reaction mixture by an external permanent magnet and can be recycled at least eight times without a significant loss of activity.     

Polymer-supported palladium (II) containing N2O2: An efficient and robust heterogeneous catalyst for C–C coupling reactions

A new polymer was prepared from 1,3,5-triformylphloroglucinol (noted as TDTB) and o-phenylenediamine through Schiff base condensation reaction, and palladium (II) was immobilized on the polymer (noted as TbPo-Pd(II)). This process was easy to work-up and cost-effective. The structure and composition of TbPo-Pd(II) were fully characterized by FTIR, TGA, XPS, AAS, SEM, and TEM analyses. Meanwhile, this catalyst showed desired thermal stability and excellent performance in water/methanol system for Suzuki and Sonogashira coupling reactions. In addition, this heterogeneous catalyst can be readily recovered by simple filtration with no appreciable Pd leaching in the reaction. This work provides a powerful protocol for rapid access to asymmetrical biphenyls and aryl alkynes. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2344–2353     

Sodium acetate catalyzed tandem Knoevenagel–Michael multicomponent reaction of aldehydes, 2-pyrazolin-5-ones,and cyano-functionalized C–H acids: Facile and efficient way to 3-(5-hydroxypyrazol-4-yl)-3-aryl-propionitriles

Sodium acetate catalyzed multicomponent reaction of aryl aldehydes, 2-pyrazolin-5-ones, and malononitrile or alkyl cyanoacetates in alcohols results in the formation of substituted 3-(5-hydroxy-3-methylpyrazol-4-yl)-3-arylpropionitriles in 80–99% yields. The developed efficient catalytic approach to the substituted 3-(5-hydroxy-3-methylpyrazol-4-yl)-3-arylpropionitriles – the promising compounds for human cardiovascular diseases therapy and different biomedical applications – is beneficial from the viewpoint of diversity-oriented large-scale processes and represents facile, efficient and environmentally benign synthetic concept for multicomponent reactions strategy.     

Baker’s yeast: An efficient,green, and reusable biocatalyst for the one-pot synthesis of biologically important N-substituted decahydroacridine-1,8-dione derivatives

A green approach for one-pot three-component synthesis of N-substituted decahydroacridine-1,8-diones is offered for the first time using baker’s yeast (Saccharomyces cerevisiae) as a biocatalyst under ultrasonication. Due to growing safety and environmental concerns, enzymatic methods were constantly investigated as an attractive alternative to toxic and nonspecific chemical approaches. This method is relatively simple, efficient, inexpensive, and environment-friendly. The catalyst was recovered and reused and also the recyclability of baker’s yeast resulted in excellent yields of products without loss of any catalytic activity.     

Aqueous mortar–pestle grinding: An efficient,attractive, and viable technique for the regioselective synthesis of β-amino alcohols

A green and highly regioselective approach for the synthesis of β-amino alcohols (with yields from 15 to 98%) via the aminolysis of epoxides by varied amines using LiBr under aqueous mortar–pestle grinding conditions has been described. Use of a mild catalyst, ordinary grinding, time economy, cost effectiveness, complete regioselectivity, and a very good to excellent yield of desired products makes this process an attractive route for the synthesis of biologically significant pharmacophores. Furthermore, the developed protocol has been successfully extended to the synthesis of novel series of β-amino alcohols (3r–ad) bearing benzofused 1,2,3-triazole heterocycle with complete regioselectivity. The structure of the synthesized molecules has been characterized by spectroscopic techniques such as ¹H nuclear magnetic resonance (NMR), ¹³C NMR, and mass spectroscopy/elemental analysis.     

Embedded palladium nanoparticles on metal–organic framework/covalently sulfonated magnetic SBA-15 mesoporous silica composite: As a highly proficient nanocatalyst for Suzuki–Miyaura coupling reaction in amino acid-based natural deep eutectic solvent

In this project, the main aim is the design and present a novel and unique heterogeneous nanocatalyst based on a metal–organic framework/covalently sulfonated magnetic SBA-15 mesoporous silica composite with the emphasis on promoting clean and green synthetic transformations and increasing the catalytic properties. In more detail, initially, SBA-15 containing magnetic nanoparticles was functionalized by a 1,3-propane sultone ligand. In the next step, the functionalized mesoporous substrate was used as a scaffold for the growth and synthesis of the zeolite imidazolate framework-8 (ZIF-8) crystals. The obtained composite was further applied as a suitable support for the immobilization of Pd nanoparticles via a post-modification procedure and the generation of heterogeneous catalysts. The prepared Fe₃O₄@SBA-15-SO₃H@ZIF-8@Pd was incorporated as a heterogeneous and green catalyst in the Suzuki coupling reaction in the natural deep eutectic solvent with efficient recyclability.     

Four component tandem Knoevenagel–Michael strategy for the assembly of arylaldehydes,N,N'-dimethylbarbituric acid, 4-hydroxy-6-methyl-2H-pyran-2-one and morpholine into unsymmetrical scaffold with three different heterocyclic rings

A new type of four component tandem Knoevenagel–Michael reaction has been found consisting in the assembly of benzaldehydes, N,N'-dimethylbarbituric acid, 4-hydroxy-6-methyl-2H-pyran-2-one and morpholine in alcohols, other organic solvents or water at room temperature without catalyst or any other additives, which results in the selective formation of unsymmetrical scaffold with three different heterocyclic rings in 63–98% yields. The crystal structure of morpholinium 5-[(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)(4-nitrophenyl)methyl]-1,3-dimethyl-2,6-dioxo-1,2,3,4-tetrahydropyrimidin-6-olate has been confirmed by X-ray diffraction.     

Sulfonic acid–functionalized magnetic Fe3-xTixO4 nanoparticles: New recyclable heterogeneous catalyst for one-pot synthesis of tetrahydrobenzo[b]pyrans and dihydropyrano[2,3-c]pyrazole derivatives

In this work, titanomagnetite nanoparticles (Fe_3-xTi_xO₄) have been used as a novel suppport for the synthesis of a magnetic acidic catalyst. These nanoparticles were functionalized with sulfonic acid groups to prepare the Fe_3-xTi_xO₄@SO₃H nanoparticles. The synthesized acidic nanoparticles have been explored as new and efficient recyclable heterogeneous catalyst for a one-pot, three-component synthesis of tetrahydrobenzo[b]pyrans known as 4H-chromenes and 1,4-dihydropyrano[2,3-c]pyrazoles. The structure of the catalyst was established by infrared, energy dispersive x-ray (EDX), and scanning electron microscopy analyses. The reactions proceed smoothly to furnish the respective products in excellent yields and short reaction times. The facile reaction conditions, easy isolation of the products, versatility, and easy magnetic separation and reusability of the catalyst with no significant loss of activity are the main merits of the present method.     

Facile access to polymer supported zinc–salen complex: highly efficient heterogeneous catalyst for synthesizing hydantoins,thiohydantoins and Schiff bases in aqueous medium

Research on Chemical Intermediates - The synthesis of polymer supported zinc–salen complex (PS-Zn–salen) is described. The mononuclear zinc(II)–salen complex was characterized by...     

γ-Al2O3/triflic acid as cooperative catalysts for the tandem Michael addition/carbocyclization: An easy access to 2-substituted pyrrolo[2,1-a]isoquinolines and 3-substituted pyrrolidine-2,5-diones

A tandem Michael addition/carbocyclization of 3,4-dimethoxyphenethyl maleimide with carbon and sulfur nucleophiles is accomplished via a relay catalysis using γ-Al₂O₃/TfOH binary system. The X-ray Photoelectron Spectroscopy (XPS) analysis of binary system indicates the presence of AlF₃, AlO(OH) species_. This approach provides an easy access to 2-aryl or 2-thio aryl pyrrolo[2,1-a]isoquinolines in good yields in a tandem fashion. With suitable ratio of γ-Al₂O₃/TfOH binary system, the Michael addition of N/C/S nucleophiles to N-benzyl maleimide is also achieved. A key to the success of these reactions would be the generation of AlF₃, AlO(OH) species from γ-Al₂O₃ and TfOH, which might have delineated the disadvantageous background reactions usually displayed by a strong Brønsted acid such as TfOH.     

Silica-supported perchloric acid (HClO4–SiO2): a mild, reusable and highly efficient heterogeneous catalyst for multicomponent synthesis of 1,4-dihydropyridines via unsymmetrical Hantzsch reaction

Facile synthesis of some 1,4-dihydropyridine derivatives via Hantzsch reaction of 5,5-dimethyl-1,3-cyclohexanedione (dimedone), 1,3-diphenyl-2-propen-1-one derivatives and ammonium acetate under solvent-free condition in the presence of silica-supported perchloric acid (HClO₄–SiO₂) is described. The catalyst is easily prepared, stable, reusable and efficient under the reaction conditions.     

Copper and nickel immobilized on cytosine@MCM-41: as highly efficient,reusable and organic–inorganic hybrid nanocatalysts for the homoselective synthesis of tetrazoles and pyranopyrazoles

In this work, a green approach is reported for efficient synthesis of biologically active tetrazole and pyranopyrazole derivatives in the presence of Cu-Cytosine@MCM-41 and Ni-Cytosine@MCM-41 (copper (II) and nickel (II) catalyst on the modified MCM-41 using cytosine). The synthesis of tetrazoles and pyranopyrazoles in the presence of these catalysts was performed in green solvents such as water or poly (ethylene glycol) (PEG). All products were obtained in high TOF (turnover frequency) numbers in the presence of these catalysts, which indicate the high efficiency of these catalysts in the synthesis of tetrazole and pyranopyrazole derivatives. The prepared catalysts were characterized by various techniques such as BET, TGA, XRD, FT-IR, SEM, EDS, WDX, TEM, and AAS. Mesoporous structure of these catalysts was confirmed by nitrogen adsorption–desorption isotherms. These catalysts can be recovered and reused for several runs without significant change in their catalytic activity or metal capacity. The recovered catalysts have been characterized by XRD, SEM, EDS, WDX, FT-IR and AAS techniques, by which their heterogeneous nature has been confirmed.     

Sol–gel derived LaFeO3/SiO2 nanocomposite: synthesis,characterization and its application as a new,green and recoverable heterogeneous catalyst for the efficient acetylation of amines,alcohols and phenols

LaFeO₃/SiO₂ nanocomposite was synthesized by the sol–gel process from metal nitrates and tetraethyl orthosilicate (TEOS) as the SiO₂ source. The nanocomposite product was characterized by XRD, FT-IR, SEM, and surface area measurements and was used as a heterogeneous catalyst for the efficient acetylation of amines, alcohols and phenols to the corresponding acetates using acetic anhydride under solvent-free conditions. Among the various substrates, acetylation of amines was preceded rapidly, so that an amine group could be selectively acetylated in the presence of alcoholic or phenolic hydroxyl groups by the appropriate choice of reaction time. The catalyst can also be reused several times without the loss of activity. In addition, the catalytic activity of the LaFeO₃/SiO₂ nanocomposite was higher than that of the pure LaFeO₃ nanoparticles. The method is high yielding, clean, cost effective, compatible with the substrates having other functional groups and very suitable for the practical organic synthesis.     

Sulfonated Honeycomb Coral (HC-SO<Subscript>3</Subscript>H): a new,green and highly efficient heterogeneous catalyst for the rapid one-pot pseudo-five component synthesis of 4,4′-(aryl methylene) bis(3-methyl-1<Emphasis Type="Italic">H</Emphasis>-pyrazol-5-ol)s

Sulfonated Honeycomb Coral (HC-SO₃H), has been synthesized from the reaction of Honeycomb Coral with chlorosulfonic acid as sulfonating agent. The as-synthesized catalyst was characterized via XRF, FT-IR, TGA, SEM–EDS, XRD, BET and pH analysis. The superior catalytic activity of HC-SO₃H was investigated for the synthesis of 4,4′-(aryl methylene)bis(3-methyl-1H-pyrazol-5-ol) derivatives through the one-pot pseudo-five component reactions. The main advantages of this protocol include simple procedure, excellent yields and short reaction times besides the non-toxicity, high stability and reusability of the catalyst.