Amine functionalized silica coated Fe3O4 nanoparticles (SiO2@MNP-A) were successfully prepared as a novel heterogeneous amine. The catalyst was characterized by XRD, FT-IR, TEM, magnetic measurement, elemental analysis and was found to be a magnetically separable and highly active catalyst for ambient Knoevenagel condensation of aromatic aldehydes and α-aromatic (heteroaromatic or polyaromatic)-substituted methylene compounds in water under ultrasonic irradiation to afford the corresponding products in good to excellent yields. Very interestingly, SiO2@MNP-A successfully catalyze the reaction of the non-cyano substituted compound with benzaldehyde to achieve a key intermediate for the preparation of Atorvastatin calcium in green and atom-economic manner. In addition, the catalyst SiO2@MNP-A can be reused for 8 times without any obvious loss of its activity. The role of ultrasonication in the Knoevenagel condensation was also discussed with the assistance of UV–vis spectrometry. 相似文献
In this work, Al2O3 was mixed with SiO2 and poly 4-vinylpyridine by the sol-gel method in order to make a composite which is used as a heterogeneous basic catalyst for Knoevenagel condensation reaction. The physical and chemical properties of the composite catalyst were investigated by XRD, FT-IR, TG, BET and SEM techniques. The catalytic performance of each material was determined for the Knoevenagel condensation reaction between carbonyl compound and malononitrile. The reactions were performed in solvent-free conditions and the product was obtained in high yield and purity after a simple work-up. The effects of the amount of catalyst, amount of monomer for the synthesis of composite and recyclability of the heterogeneous composite were investigated. The composite catalyst used for this synthetically useful transformation showed considerable level of reusability besides very good activity. 相似文献
We report a Ti(OiPr)4/pyridine-mediated Knoevenagel reaction between aromatic ketones and cyanoacetamides to provide Knoevenagel olefin products in good to excellent yields. Almost in all cases studied, a single geometrical isomer was formed and isolated under the Ti(OiPr)4/pyridine condensation conditions. This methodology was also demonstrated to be highly effective between some other Knoevenagel active methylene compounds and aromatic ketones. 相似文献
Polyvinyl amine coated Fe3O4@SiO2 composite microspheres with a core-shell structure were prepared and employed as a magnetic catalyst for Knoevenagel condensation under mild conditions. The catalyst can be readily recovered using a magnet and reused several times without loss in activity or selectivity. The performance of the magnetic base catalyst was compared with that of polyvinyl amine functionalized mesoporous SBA-15, which showed that the magnetic nanoparticles gave improved reaction rate and yield. 相似文献
Fe3O4 magnetic nanoparticles (MNPs) were obtained using a reduction–precipitation method. These MNPs were modified with cysteamine hydrochloride. This catalyst was characterized using a number of physicochemical measurements. The Fe3O4–cysteamine MNPs, as an efficient and heterogeneous catalyst, were successfully used for Knoevenagel condensation under mild conditions. The activity of this nanomagnetic catalyst in the Knoevenagel condensation of aromatic aldehydes and malononitrile is described. Easy preparation of the catalyst, easy work‐up procedure, excellent yields and short reaction times are some of the advantages. 相似文献
In this study, Fe3O4 nanoparticles were functionalized with cellulose, and then hybridized with cobalt (II)-based metal-organic framework (Co-MOF) containing carboxylate and imidazole functionalities. FTIR, XRD, FE-SEM, TEM, BET, EDX, VSM and STA analyses were used to characterize the synthesized samples. The resultant Fe3O4/cellulose/Co-MOF nanocomposite was applied efficiently as a powerful and economic heterogeneous catalyst in the condensation of a variety of different aromatic aldehydes with malononitrile under solvent-free conditions at room temperature for 10 min and offered the corresponding coupling products in high yields. The catalyst could be straightforwardly separated by a magnet from the reaction mixture and reused without a noteworthy drop in catalytic activity at least five times. The use of Fe3O4/cellulose/Co-MOF catalyst outcomes under mild reaction conditions in very short reaction time, outstanding catalytic activity, high recyclability and an easy work-up process for Knoevenagel condensation. 相似文献
The reaction rate of Knoevenagel condensation can be dramatically enhanced by irradiating the reaction mixture containing an aldehyde, diethyl malonate, P2O5, piperidine, and chlorobenzene with a commercial microwave oven. Six Knoevenagel condensation products were synthesized within 5–15 min in good yields. 相似文献
A new protocol for the Knoevenagel condensation between β-diketones and aliphatic and aromatic aldehydes promoted by Mg(ClO4)2 under mild conditions is reported. 相似文献
This study presented an effective method to modify the surface chemical reactivity of a SiO2/Fe3O4 support. The unmodified SiO2/Fe3O4 support was prepared by the hydrolysis and condensation of tetraethoxysilane on the surface of hydrophilic Fe3O4 nanoparticles. These were then modified by a heat treatment in an ethanol/water solution under reflux. The resulting samples were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and transmission/scanning electron microscopy. The immobilization of a TiO2 nanocatalyst on both unmodified and modified supports was performed to investigate the effects of the modification of the magnetic silica support on the loading of a TiO2 nanocatalyst and the photocatalytic activity. The loading of TiO2 and the photocatalytic activity were both improved. 相似文献
An efficient and simple procedure was developed for the green synthesis of various 2‐aryl‐1‐ben‐zylated‐1H‐benzimidazoles in high yields by condensation of o‐phenylenediamine with aldehydes with P2O5/SiO2 as catalyst under solvent‐free and ambient conditions. 相似文献
Abstract Knoevenagel condensation of aromatic aldehydes with active methylene compounds under solvent‐free conditions to synthesize arylidene compounds in good to excellent yields using powdered anhydrous K2CO3 and PEG400 as catalysts has been described. 相似文献
On the Influence of Seed Crystals on the Formation of Calcium Silicates with the Composition 3 CaO · 2 SiO2 The formation of the calcium silicates kilchoanite and rankinite of the composition 3 CaO · 2 SiO2 is facilitated and enabled, respectively, in the presence of appropriate seed crystals. Kilchoanite (Ca6[(SiO4)(Si3O10)]) is formed from mixtures of CaO and SiO2 in the autoclave at 200°C and from C? S? H (di, poly) under normal atmosphere at 700°C by seeding for example with kilchoanite, aluminium compounds, γ-Ca2SiO4. Rankinite (Ca3Si2O7) can be synthesized under the same conditions, when rankinite itself is applied as seed crystal. 相似文献
Abstract A rapid and efficient procedure is developed for a one-pot synthesis of nitriles by condensation of aldehydes with hydroxylamine hydrochloride in the presence of P2O5/SiO2 in solvent-free media under microwave irradiation. 相似文献
The reaction of malonylchloride with ethylene glycol or dithioglycol at low temperatures and high dilution leads to cyclic condensation products of 2∶2 composition, of which the first one reacts with aldehydes to give alkenes (Knoevenagel condensation). On the other hand, malonyl chloride and pinacol react under the same conditions to give a linear oligomeric condensation product. The Knoevenagel condensation products are electrically neutral organic Lewis acids (pK′L-values: 8.35 and 7.85). Mass-spectra, NMR-, UV- and IR-spectra were employed for structural determinations. 相似文献
Zeolite FAU with tunable SiO2/Al2O3 molar ratio has been successfully synthesized in the absence of organic structure‐directing agents (OSDA). Specifically, the addition of zinc species contributes to the feasible and effective adjustment of the framework SiO2/Al2O3 molar ratio between about 4 and 6 depending on the amount of zinc species added in the batch composition. In contrast, a typical OSDA such as tetramethylammonium hydroxide (TMAOH) has a limited effect on the SiO2/Al2O3 molar ratio of the zeolite. The role of zinc species is essential for the crystallization of zeolite FAU with a higher SiO2/Al2O3 molar ratio under the particular synthesis conditions. It is speculated that zinc species may suppress the incorporation of aluminum into the aluminosilicate framework, which is due to the Coulombic repulsive interaction. A higher SiO2/Al2O3 molar ratio is also found to be accompanied by a lower CO2 adsorption heat for CO2/CH4 separation. 相似文献
Synthesis of 1,6-diamino-4-phenyl-3,5-dicyano-2-pyridone derivatives via a one-pot, three-component reaction of aryl aldehydes, malononitrile, and cyanoacetic hydrazide at room temperature using KF-Al2O3 as a recyclable catalyst have been developed. The reaction proceeds through the initial Knoevenagel condensation between aldehyde and malononitrile in the presence of KF-Al2O3 to form the benzylidene derivative which then undergoes Michael addition with cyanoacetic hydrazide followed by intramolecular cyclization of the resulting intermediate to produce the N-amino-2-pyridones in good to excellent yields. The structure of the synthesized compounds were characterized and established on the basis of their spectral data analysis and single-crystal XRD analysis. 相似文献
Thermoanalytic studies carried out on hydrate phases Na2[SiO2(OH)2]·nH2O (n = 4, 5, 7, 8) reveal two phase transitions at elevated temperatures under open-system and non-isothermal conditions Congruent melting at temperatures Tmp is followed by condensation at temperatures Tc > 380 K with subsequent formation of solid Na2[SiO3]. Foamingof the melts upon condensation is observed through heating stage microscopy. In situ 29Si NMR experiments proved oligomeric or endless chain-type anions, [Si1+nO2+3n(OH)2](2+2n)?, to be formed in the melts under open-system conditions. From DTA double peak configurations at temperatures Tc the thermal decomposition of the melts is shown to occur in a two-step reaction, uniformly with all four hydrate phases.Isothermal studies below melting temperatures show distinct decomposition of crystalline Na2[SiO2(OH)2]·8H2O to crystalline Na2[SiO2(OH)2]·4H2O whereas all the other crystallinephases within this hydrate series dehydrate to amorphous waterglass-type materials under identical experimental conditions in long-term annealing experiments. This exceptional phase relation between the octa- and the tetrahydrate has also been proved by X-ray powder diffraction heating experiments. 相似文献