2286-35-3

Li2O/ZnO catalyst was prepared by wet impregnation method and characterized by XRD, SEM, EDX, FTIR, BET surface area and UV-Vis diffuse reflectance spectroscopy. This study revealed a decrease in average particle size and change in the shape of

A novel, heterogeneous and homogeneous basic nanocatalysts were synthesized by grafting of lithium and cesium on zagrosian natural asphalt sulfonate (Li/Cs-Zagronas). The activity of these catalysts was examined in the Claisen–Schmidt and Knoevenagel condensations under mild reaction conditions. Li/Cs-Zagronas were characterized by FT-IR spectroscopy, scanning electron microscopy, X-ray diffraction, energy-dispersive spectroscopy, inductively coupled plasma and thermogravimetric analysis techniques. These nanocatalysts were removed by simple filtration and reused several times without any deterioration of activity.

A simple, effective, green and nontoxic protocol was used for the Knoevenagel condensation and the biscoumarin derivatives synthesis. It have demonstrated that the use of a new hybrid crystal as a heterogeneous catalyst makes it possible to obtain several

Abstract: A simple, highly versatile, and efficient protocol for the synthesis of substituted olefins from various aromatic aldehydes and active methylene compounds by Knoevenagel condensation using an efficient, eco-friendly, and recyclable nano-ZnO cata

In the present study, a rapid, simple and an efficient procedure for the Knoevenagel condensation of various carbonyl and active methylene compounds in ethanol at a moderate temperature in the presence of a catalytic amount of an efficient, environmentall

In this research, we synthesized and characterized a new heterogeneous basic nanocatalyst and its catalytic application was studied in the Claisen-Schmidt and Knoevenagel condensations. In order to prepare this nanocatalyst, first, the Iranian natural asphalt was sulfonated with the concentrated sulfuric acid and then, converted to the potassium natural asphalt sulfonate (K-NAS). In order to characterization of the nanocatalyst, used of FT-IR spectroscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), inductively coupled plasma (ICP) and thermogravimetric analysis (TGA) techniques. This new basic heterogeneous nanocatalyst have advantages such as being eco-friendly, huge specific surface area, high reactivity and recyclability.

An amine-functionalized metal organic framework (MOF) was used as highly efficient and recyclable heterogeneous catalyst for Knoevenagel condensation of various aromatic aldehydes and ketones in ethanol. The catalytic efficiency was demonstrated by the hi

In this work, smooth efficient and eco-friendly two component coupling method is reported for the synthesis of Knoevenagel Condensation product in presence of Bi(OTf)3 catalyst under solvent free condition. Catalyst has participated in condensation between substituted aldehydes (aromatic and hetero-aromatic) and active methylene compounds (ethyl cyanoacetate, malononitrile and cyanoacetamide) effectively to generate an excellent yield of the product. Bi(OTf)3 catalyst is stable, inexpensive and easily available was used for four times in this reaction without loss of catalytic activity. [Formula Presented]

Abstract: Acid–base copolymer materials are of considerable interest because of their fundamental implications for acid–base bifunctional catalysis applications. However, quenching the acid and base sites of the copolymer with each other in free radical polymerizations is still challenging. Herein, we demonstrate that the polymerization of styrenesulfonic acid-co-4-vinylpyridine into the mesoporous carbon material (i.e., CMK-3) can control the chain growth polymerization and result in decreasing the interaction of the acid–base sites. The results showed that by using CMK-3, 40% of the acid and base sites of the copolymer remain in their original form while 60% of acid and base sites convert to the pyridinium and sulfonate forms. Furthermore, it is demonstrated that this material can be processed as a heterogeneous bifunctional acid–base catalyst in the tandem one-pot acid–base reaction (i.e., deacetalization–Knoevenagel condensation reaction) with a high catalytic activity in aqueous media. Graphic abstract: [Figure not available: see fulltext.].

Abstract: Calcined dolomite was utilized as a low-cost and efficient catalyst for the Knoevenagel condensation of aldehydes with active methylene compounds such as malononitrile and ethyl cyanoacetate to afford substituted α, β-unsaturated carbonyl compou

A series of new prolinamide polyacrylonitrile fiber catalysts with tunable length of alkyl linker and different linker group were prepared by covalent bonding for the first time and well characterized by mechanical strength, FT-IR, XRD, EA, TGA, SEM and water contact angel. The catalytic activities of these fiber catalysts were evaluated in Knoevenagel condensation and one-pot Knoevenagel-Michael multicomponent tandem reactions to synthesize α, β-unsaturated nitrile and 2-amino-4H-chromene derivatives in water. The result show that the suitable linker length attaching amines to fiber matrix as well as the constructed hydrophobic microenvironment by linker group within the surface layers of fiber materials effectively promotes the reactions. In addition, the good swollen capacity of fiber in solvent ensure that the reaction proceed well. Fiber catalyst PANPA?2F modified by prolinamide with a C2 alkyl chain exhibited the best catalytic performance and can be easily recovered and reused for at least ten consecutive cycles without significant loss of catalytic activity and active sites leaching.

Zeolitic imidazolate framework-8 (ZIF-8) was successfully composited with an anionic basic resin 201?×?7 (717-resin) to provide a novel ZIF-8/717-resin composite. Its catalytic activity toward the Knoevenagel condensation reaction was evaluated. Results s

Bis[(3-aminopropyl)triethoxysilane]dichloride immobilized on magnetic nano-γ-Fe2O3@SiO2 has been prepared. After characterization, the reagent was used for efficient promotion of the Knoevenagel reaction, achieving high re

Mesostructured cellular foam silica was functionalized by an amino group (MCF-NH2) using the postsynthesis grafting method and utilized as a recyclable catalyst for the Knoevenagel reaction to afford α, β-unsaturated compounds. The catalyst was systematic

In recent years, great attention has been paid to cascade reactions, which can improve efficiency and reduce waste production by implementing several consecutive reactions. Herein, two bifunctional catalysts were successfully prepared by precise control of the oriented layered double hydroxides (LDHs) growth on graphene oxides (GO) using a single-drop and co-precipitation method, respectively. The resultant Ru/LDH-GO-P and Ru/LDH-GO-V composites were characterized by EXAFS, FT-IR, XRD, TG-DTA, BET, XPS, TEM, CO2-TPD, O2-TPD, etc. The catalytic performance of Ru/LDH-GO-P and Ru/LDH-GO-V for one-pot oxidation-Knoevenagel condensation reaction showed significant difference under the same experimental conditions, in which the Ru/LDH-GO-P showed 99 % conversion and 99 % selectivity, in marked contrast of 60.7 % conversion and 47.9 % selectivity using Ru/LDH-GO-V as catalyst. The large enhancement of the catalytic performance using Ru/LDH-GO-P can be attributed to the following reasons: 1) the Co3+ centers in Ru/LDH-GO-P can promote the formation of surface oxygen vacancies that can adsorb and activate O2 to get better performance; 2) the Ru/LDH-GO-P exhibited larger BET surface and more medium-strong basic active sites than the Ru/LDH-GO-V. Moreover, the Ru/LDH-GO-P catalyst can be easily recovered from the reaction system and reused for at least five times without obvious deterioration of its catalytic activity or structural integrity.

Abstract: In this paper, a new convenient strategy for the synthesis of polyethylenimine functionalized Si-MCM-41 grafted on surface modified graphene oxide has been developed. The as-synthesised catalyst exerts good catalytic activity and reusability tow

N-(2-Hydroxy-ethyl)-pyridinium chloride ([HyEtPy]Cl) was synthesized and explored as a novel promoter for 1,4-diazabicyclo [2.2.2] octane (DABCO)-catalyzed Knoevenagel condensation reactions, which showed better catalytic activity compared to other ionic liquid (IL) that had no hydroxyl group attached to the IL scaffold. The effect of hydrogen bond formation between the hydroxyl group of [HyEtPy]Cl and the carbonyl group of aldehyde played an important role in the Knoevenagel condensation reaction. In the [HyEtPy]Cl-H2O-DABCO composite system, Knoevenagel condensation reactions proceeded smoothly and cleanly, and the corresponding Knoevenagel condensation products were obtained in good to excellent yields in all cases examined. This protocol provides a versatile solvent-catalyst system, which has notable advantages such as being eco-friendly, ease of work-up and convenient reuse of the ionic liquid.

An unusual reaction between GO, DBU and DMF, that typically uses base and solvent, has been thoroughly analyzed providing valuable basic knowledge about the reactivity of GO, which is essential to control functionalization and therefore the properties of

Abstract: Amine functionalized wrinkled silica nanospheres (WSiO2–NH2) were successfully synthesized by using a simple biphase sol–gel approach. The prepared silica nanospheres were characterized by using various techniques, such as

Immobilized sulfuric acid on magnetic Fe3O4 nanoparticles (Fe3O4 MNPs-OSO3H) as a new solid acid nanocomposite was successfully synthesized and its catalytic activity in a series of condensation reactions was studied. High catalytic activity, simple separation from reaction mixture by an external magnet and good reusability are several eco-friendly advantages of this catalytic system. It is noteworthy that this catalytic system is applicable to a wide range of spectrum of aromatic aldehydes, and the desired products were obtained in good to excellent yields under mild conditions. The use of ecofriendly solvents makes also this synthetic protocol ideal and fascinating from the environmental point of view.

Sulfamic acid immobilized on diethylenetriamine functionalized Fe3O4 nanoparticles (SA-DETA-Fe3O4) was successfully prepared and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM), thermo gravimetric analysis (TGA), X-Ray diffraction (XRD) and scanning electron microscopy (SEM). The sulfamic acid was found as a magnetically separable and highly active catalyst for the oxidative coupling thiols, oxidation of sulfides. Furthermore, the SA-DETA-Fe3O4 showed the high catalytic activity in Knoevenagel condensation of aromatic aldehydes with active methylene compounds (malononitrile and ethyl cynoacetate). The nanosolid catalyst could be easily recovered by a simple magnetic separation and reused for many cycles without deterioration in catalytic activity.

Abstract: The l-lysine functionalized polyacrylonitrile fiber (PANLF) was prepared by grafting the l-lysine into a commercially available polyacrylonitrile fiber and showed highly catalytic activity for Knoevenagel condensation reaction. With low temperature (45?°C) and short reaction time (1?h), the fiber catalyst was well applicable to Knoevenagel condensation of a wide range of aldehydes and the yields could reach up to 99%. Interestingly, only in water could the reaction take place smoothly (with a yield of 88%) and a polar micro-environment promoted reaction process had been proposed to explain this phenomenon. Besides, the fiber catalyst has advantages of easy preparation, high functional degree, strong mechanical strength and thermal stability, etc. And it can be reused at least 5 times without further treatment and performed well in scaled-up experiment (amplified 50 times) and flow chemistry experiment (no loss of catalytic activity after 48?h), which indicates its potential application in industry application. Graphical Abstract: [Figure not available: see fulltext.].

A novel Ni-based metal–organic framework (Ni-MOF) with a Schiff base ligand as an organic linker, Ni3(bdda)2(OAc)2?6H2O (H2bdda?=?4,4′-[benzene-1,4-diylbis(methylylidenenitrilo)]dibenzoic acid), was synthesized and characterized using powder X-ray powder diffraction, thermogravimetric analysis, Brunauer–Emmett–Teller measurements, inductively coupled plasma atomic emission spectroscopy, transmission electron microscopy, elemental analysis and Fourier transform infrared spectroscopy. The synthesized Ni-MOF exhibited a high catalytic activity in benzyl alcohol oxidation using tert-butyl hydroperoxide under solvent-free conditions. Also, the efficiency of the catalyst was investigated in the cascade reaction of oxidation–Knoevanagel condensation under mild conditions. The Ni-MOF catalyst could be recovered and reused four times without significant reduction in its catalytic activity.

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.

Abstract: Diethylenetriamine immobilized on magnetic Fe3O4 nanoparticles (DETA-Fe3O4) was successfully prepared as a new and well dispersed magnetically separable amine catalyst. The structure of the resulting catalyst was well characterized by a series of analysis techniques such as FT-IR, SEM, EDX, VSM, TGA and XRD. The catalytic activity of DETA-Fe3O4 was evaluated with Knoevenagel condensation of active methylene compounds with aromatic aldehydes. Interestingly, the cyclocondensation of anthranilamide and aldehydes were effectively catalyzed by DETA-Fe3O4 in water, and the desired products (2,3-dihydroquinazoline-4(1H)-ones) were afforded in admirable yields. Catalysis research under aqueous medium (water) also makes this synthetic protocol ideal and fascinating from the environmental point of view. The amine catalyst can be magnetically recovered after the reaction and can be reused many times without appreciable decrease in activity.

Bromine source immobilized on magnetic nanoparticles functionalized with diethylenetriamine was successfully synthesized and characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, vibrating sample magnetometry, thermogravimetric analysis and X-ray diffraction. The catalytic activity in the synthesis of 2,3-dihydroquinazoline-4(1H)-one and polyhydroquinoline derivatives and in Knoevenagel condensation was studied. The bromine catalyst can be magnetically recovered and reused several times without significant loss of its catalytic activity. All products were obtained in high to excellent yields.

A phenyliododiacetate (PhI(OAc)2) mediated an efficient and novel protocol for the Knoevenagel reaction has been successfully accomplished. A base free, simple and straightforward method afforded wide substrate scope and good functional group tolerance, having high yields (80–92%) under environmentally benign and mild reaction conditions.

The significance of intermolecular classical and non-classical H-bonding interactions in the stabilization of a naphthalene core based conformationally rigid cleft-shaped 1,5-dioxocin (BNAP) is presented here. The importance of H-bonding interactions to a

A novel amine-functionalized ionic liquid-based periodic mesoporous organosilica (PMO-IL-NH2) was prepared and characterized and its catalytic performance was investigated in the Knoevenagel reaction. PMO-IL-NH2 was prepared by simul

A novel ionic liquid based bifunctional periodic mesoporous organosilica supported potassium carbonate (BPMO-IL-KCO3) is prepared, characterized and its catalytic efficiency is studied in the Knoevenagel reaction. The BPMO-IL-KCO3 wa

Potassium fluoride (KF)/montmorillonite (K10-MMT) nanostructure acts as an active heterogeneous base catalyst for Knovenagel condensation. Here we have described the catalytic activities of KF/K10 nanostructure in the condensation reaction of various subs

The simple and high yield synthesis of H6Cu2[PPD]6[SiW9Cu3O37]·12H2O (PPD = p-phenylenediamine) as a new organic-inorganic hybrid polyoxometalate is reported. The new compound consists of trimetal-substitution polyoxometalate of A-β-SiW9Cu3O3710-, water molecules and coordinated and noncoordinated PPD molecules. H6Cu2[PPD]6[SiW9Cu3O37]·12H2O was firmly grafted on graphene oxide decorated with Fe3O4 nanoparticles. These nanocomposites were characterized by elemental analyses, thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR), X-ray photoelectron spectrum (XPS), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and alternating gradient force magnetometer (AGFM). The results indicate that the size range of the nanoparticles are between 20 and 60 nm. The catalytic activity of H6Cu2[PPD]6[SiW9Cu3O37]·12H2O and the magnetically reusable nanocomposite of GO@Fe3O4@H6Cu2[PPD]6[SiW9Cu3O37]·12H2O were investigated in the Knoevenagel condensation and synthesis of 2,3-dihydroquinazolin-4(1H)-ones.

A highly efficient and reusable catalyst based on metal-organic frameworks (MOF) has been synthesized by post-functionalization and applied in Knoevenagel condensations of various aldehydes and ketones. The catalytic efficiency was demonstrated by the hig

We have described the catalytic activities of dicalcium phosphate dihydrate (DCPD) in the condensation reaction of various substituted benzaldehydes with active methylene compound malononitrile. The influences of reaction conditions on the corresponding c

The polyoxometalate (POM) intercalated layered double hydroxides (LDHs) have been widely used as heterogeneous catalysts. However, the application of POM-LDHs as bifunctional catalysts for cascade reaction has seldom been studied compared to the noble-metal-based catalysts. Herein, a series of POM-LDHs catalysts of Tris-LDH-X4(PW9)2 (X=Mn, Fe, Co, Ni, Cu, and Zn; Tris=Tris(hydroxymethtyl)aminomethane) have been prepared. The efficacy of Tris-LDH-Zn4(PW9)2 as efficient bifunctional catalyst has been demonstrated for cascade reactions involving oxidation of benzyl alcohol to benzaldehyde followed by Knoevenagel condensation with ethyl cyanoacetate to produce benzylidene ethyl cyanoacetate. The combination of POM's redox/acidic sites and LDHs's basic sites led to a composite catalyst with excellent activity (99 %) and selectivity (≥99 %) under mild and soluble-base-free conditions. This work offers a new design strategy for the fabrication of efficient bifunctional catalysts for the promotion of one-pot cascade reactions.

Zr(IV)-salen-MCM-41 was prepared by reaction of NH2-MCM-41 with salicylaldehyde to afford Schiff base ligands. Thereafter, ZrOCl2·8H2O was reacted with the Schiff base ligands for complex formation. The structural properti

Four kinds of amines functionalized C60 were prepared through an amination reaction of C60 with organic amines. Their surface structures and basic properties were studied by Fourier transform infrared spectrometry (FTIR), X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD) with CO2 as the probe molecule. When used as solid base catalysts, N-aminoethylpiperazine functionalized C60 (C60-AEP) showed the best catalytic activity in the Knoevenagel condensation reaction due to the highest basic strength. In addition, the C60-AEP catalyst also showed impressive catalytic stability. All these features endowed C60-AEP with characteristics of both homogeneous and heterogeneous catalysts. More interestingly, chiral l-lysine functionalized C60 (C60-L-L) can be used for asymmetric intermolecular aldol reactions.

Amine-functionalized mesoporous silica nanospheres (～80 nm) (NH2-MSNS) were prepared by a co-condensation method using tetraethyl orthosilicate and aminopropyltrimethoxysilane. The catalytic activities of the NH2-MSNS catalysts were

A series of molecular complexes have been designed, synthesized and used as organo-catalysts for the first time for very efficient Knoevenagel condensation. Molecular complexes are thermally stable, easily recyclable, and have a low cost of preparation. T

KOH/SnO2 solid superbases of specific morphology and uniform pore structure were synthesized. The SnO2 support was prepared by reflux digestion using graphene oxide as template and employed for the loading of KOH by means of grinding

Bismuth(III) nitrate pentahydrate is found as a mild and highly efficient catalyst for the rapid synthesis of 4-amino-5-pyrimidine carbonitrile and pyrimidinone derivatives via three-component reaction of aldehydes, N-unsubstituted amidines, and malononit

A solid base catalyst has been prepared by covalent functionalization of graphene oxide with 3-aminopropyl-triethoxysilane. The catalyst exhibits a superior catalytic performance in Knoevenagel condensation (over 90 % yield and at least seven times reusab

A variety of 4H-chromenes, benzochromenes, 4,5-dihydropyrano[3,2-c]chromenes, 4H-pyran-3-carboxylates, and 3,4-disubstituted isoxazol-5(4H)-ones have been synthesized in high yields by using potassium hydrogen phthalate (KHP) as an inexpensive, commercially available catalyst. It was found that the three-component tandem reaction enabled synthesis of pyran-annulated heterocycles in water at 50 °C. 3,4-Disubstituted isoxazol-5(4H)-ones were synthesized by use of 10 mol% KHP in water at room temperature. Also, treatment of methylene-containing compounds (malononitrile or ethyl cyanoacetate) with aromatic aldehydes in the presence of 5 mol% KHP resulted in α,β-unsaturated nitriles. The procedure is an easily performed, straightforward method for synthesis of a variety of pyran-annulated compounds, isoxazol-5(4H)-one-containing heterocycles, and Knoevenagel adducts. The reaction is safe, uses mild conditions, and is environmentally benign. Other notable advantages are reuse of the catalyst, no use of hazardous organic solvents, and ease of work-up.

An efficient method for the construction of carbon-carbon double bond has been developed from aromatic aldehydes and compounds with active methylene moieties in the presence of catalytic amount of solid sodium ethoxide via mechanochemical approach. This c

A direct three-component approach has been developed for the synthesis of α-cyano acrylates starting from aldehydes, alcohols and α-cyano acetamide by employing cyanuric chloride as an organocatalyst. A class of structurally diverse α-cyano acrylates have been provided with good to excellent yields via the cascade transformation of Knoevenagel condensation and amide esterification.

Solid phase synthesis of poly(propylene imine) dendrimer is described. An iterative synthesis including double Michael addition of acrylonitrile to the primary amino groups on crosslinked polystyrene support followed by reduction of nitrile groups to amin

The condensation between aromatic aldehydes and malononitrile, ethylcyanoacetate and malonic acid for the syntheses of arylidenemalononitriles, arylidenemalonic acid esters and aryl cinnamic acids in water using alum-Cs2CO3 as a solid support catalyst has been described. Alum-Cs2CO3 was found to be a highly active, stable and recyclable catalyst under reaction conditions.

The Knoevenagel condensation of aromatic aldehydes with active methylene compounds such as malononitrile, ethyl cyanoacetate, benzimidazole-2- acetonitrile and benzothiazole-2-acetonitrile proceeded very smoothly, in a reusable and cheap choline chloride and urea based deep eutectic solvents. Both reaction time and yield are satisfactory. The advantages of this catalyst are that it is readily available, biodegradable, non-toxic, low cost and is recyclable.

Magnetite-polyoxometalate hybrid nanomaterials, Fe3O 4@SiO2@NH-NH2-PW, was prepared by grafting of H3PW12O40 on the diamine-functionalized Fe 3O4 magnetite

In this work, the hydrogen bond formation ability of cation and anion of the ILs was determined by using the solvatochromic method and was found to be responsible for their catalytic activity in the Knoevenagel reactions. The enhancement in the hydrogen bond donor ability of the cations and the hydrogen bond acceptor ability of the anions can both lead to the increase in the catalytic activity of the ILs. From the proposed reaction mechanism, it was deduced that the cations of the ILs can form hydrogen bond with aldehyde to activate the CO bond as electrophile, and the anions of the ILs can promote active methylene compound to produce carboanion as nucleophile, showing dual function activation effect in the catalytic processes. In addition, the optimized N,N-dimethylethanolamnium acetate as dual function activator for the Koevenagel reactions benefits from wide substrates tolerance, ambient reaction temperature, easy work-up procedure, and easy reuse of the IL.