Heterogeneous Catalyst For Knoevenagel Condensation Research Articles

A functionalized UiO-66 MOF for turn-on fluorescence sensing of superoxide in water and efficient catalysis for Knoevenagel condensation.

In the present work, a new MOF material of the UiO-family called Zr-UiO-66-NH-CH2-Py (1) has been obtained by the solvothermal technique and successfully characterized. The MOF structure was assembled with 2-((pyridin-4-ylmethyl) amino) terephthalic acid (H2BDC-NH-CH2-Py) as linker and Zr4+ ion. The activated form of 1 (called 1') exhibits considerable thermal and chemical stability. Compound 1' showed a very rapid and selective response for the fluorometric sensing of superoxide (O2·-) in aqueous medium even in the presence of the potentially competitive reactive oxygen species (ROS). The limit of detection value for O2·- sensing is 0.21 μM, which is comparable with those of the reported O2·- sensors. This is the first MOF based fluorescent sensor for the detection of O2·-. The response time of this MOF sensor for O2·- is very short (240 s). On the other hand, 1' was employed as a solid heterogeneous catalyst for Knoevenagel condensation between benzaldehyde and ethyl cyanoacetate at 80 °C in ethanol resulting in a very high yield of the desired product. The effects of the esterified linker ((CH3)2BDC-NH-CH2-Py) and the corresponding metal salt (ZrCl4) on this catalytic reaction were examined separately. We have also tested the substrate scope elaborately for the catalytic reaction promoted by catalyst 1'.

Zirconium potassium phosphate methyl and/or phenyl phosphonates as heterogeneous catalysts for Knoevenagel condensation under solvent free conditions

Three different basic zirconium potassium phosphate methyl and/or phenyl phosphonates of general formula Zr(PO3OK)2-(x+y)(PO3Me)x(PO3Ph)y namely ZrKP-Me, ZrKP-Ph and ZrKP-MePh have been prepared as amorphous solids. The catalytic activity of the solids was tested in the Knoevenagel condensation between several aldehydes with malononitrile and ethyl cyanoacetate in solvent free condition at room temperature and 50 °C, respectively. The hydrophobic groups on the solid catalysts surface favour reagent diffusion toward the basic sites increasing the catalytic activity of the prepared solids compared to the complete inorganic layered zirconium potassium phosphate, Zr(KPO4)2.

Efficient Synthesis of Branched Polyamine Based Thermally Stable Heterogeneous Catalyst for Knoevenagel Condensation at Room Temperature

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 toward Knoevenagel condensation of different substituted aromatic aldehydes with malononitrile and ethyl cyanoacetate. Moreover, it shows remarkable thermal stability. The physicochemical characteristics of the catalyst as probed by FTIR, XRD, N2 sorption isotherms, TGA, XPS, FESEM, TEM, and solid state 13C NMR analyses, were discussed to get an idea about the catalytic mechanism of Knoevenagel condensation.

Nanosized Copper Oxide as a Reusable Heterogeneous Catalyst for Knoevenagel Condensation

Nanosized Copper Oxide as a Reusable Heterogeneous Catalyst for Knoevenagel Condensation

Efficient heterogeneous catalysis by dual ligand Zn(ii)/Cd(ii) MOFs for the Knoevenagel condensation reaction: adaptable synthetic routes, characterization, crystal structures and luminescence studies

Chemically stable Zn(ii)/Cd(ii) MOFs as a heterogeneous catalysts for Knoevenagel condensation.

Covalently immobilized ionic liquids on single layer nanosheets for heterogeneous catalysis applications.

Ionic liquids (ILs) have attracted significant attention because of their unique chemical and physical properties. Immobilization of ILs on solid materials helps increase their efficiency and facilitate their recycling. In our present work, ILs were immobilized on α-zirconium phosphate (ZrP) single layer nanosheets by a post-grafting method. The immobilized ILs were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The characterization results supported that the ILs were covalently grafted onto ZrP nanosheets via the chemical reaction of ethoxyl silane groups in ILs with the surface hydroxyl groups on ZrP nanosheets. A high density of grafting of ILs on individual ZrP nanosheets was achieved. The immobilized ILs on individual ZrP nanosheets can be uniformly dispersed in polar chemicals and are readily accessible. When applied as a heterogeneous catalyst for Knoevenagel condensation under a solvent-free condition, such immobilized ILs exhibited high efficiency and can be easily recycled and reused.

Fe3O4@UiO-66-NH2 core–shell nanohybrid as stable heterogeneous catalyst for Knoevenagel condensation

Magnetic separation is an attractive alternative to filtration or centrifugation for separating solid catalysts from a liquid phase. Here, core-shell Fe3O4@UiO-66-NH2 nanohybrids with well-defined structures were constructed by dispersing magnets in a dimethylformamide (DMF) solution containing two metal–organic framework (MOF) precursors, namely ZrCl4 and 2-aminobenzenetricarboxylic acid. This method is simpler and more efficient than previously reported step-by-step method in which magnets were consecutively dispersed in DMF solutions each containing one MOF precursor, and the obtained Fe3O4@UiO-66-NH2 with three assembly cycles has a higher degree of crystallinity and porosity. The core-shell Fe3O4@UiO-66-NH2 is highly active and selective in Knoevenagel condensations because of the bifunctionality of UiO-66-NH2 and better mass transfer in the nano-sized shells. It also has good recycling stability, and can be recovered magnetically and reused at least four times without significant loss of catalytic activity and framework integrity. The effects of substitution on the reactivity of benzaldehyde and of substrate size were also investigated.

Mn-grafted imine-functionalized mesoporous SBA-15 as an efficient catalyst for Knoevenagel condensation under mild conditions

Surface functionalization of SBA-15 followed by its reaction with manganese acetate has been carried out to develop a new Mn-grafted functionalized mesoporous material and it was characterized by powder X-ray diffraction (XRD), BET nitrogen adsorption–desorption, IR spectroscopy, transmission electron microscopy and diffuse reflectance UV–Vis spectroscopy. The XRD and TEM analyses showed that textural properties of SBA-15 were retained during the grafting procedure and after five-time recycling. The resulting material was successfully applied as a heterogeneous catalyst for Knoevenagel condensation in good to excellent yields under mild conditions.

Solvent Free Highly Dispersed Zinc Oxide within Confined Space of Al- Containing SBA-15 as an Efficient Catalyst for Knoevenagel Condensation

A mesoporous silica-supported zinc oxide catalyst was successfully synthesized by directly grinding zinc nitrate into the as-prepared Al-Containing SBA-15 occluded with template and characterized by powder X-ray diffraction (XRD), BET nitrogen adsorption-desorption methods, IR spectroscopy, transmission electron microscopy and diffuse reflectance UV-Vis spectroscopy. This solvent-free method not only saves the time and energy, but also enables a high dispersion of zinc oxide without pore blocking in the channels of mesoporous silica. The XRD and TEM analyses show that textural properties of Al-SBA-15 retained after coating process. The resulting material was successfully applied as a heterogeneous catalyst for Knoevenagel Condensation in good to excellent yields under mild conditions. Keywords: ZnO. Al-SBA-15, mesoporous, heterogeneous catalyst, solvent-free, knoevenagel condensation.

New Green, Recyclable Magnetic Nanoparticles Supported Amino Acids as Simple Heterogeneous Catalysts for Knoevenagel Condensation

New Green, Recyclable Magnetic Nanoparticles Supported Amino Acids as Simple Heterogeneous Catalysts for Knoevenagel Condensation

Polystyrene-supported chloroaluminate ionic liquid as a new heterogeneous Lewis acid catalyst for Knoevenagel condensation

Abstract Non-hygroscopic polystyrene-supported chloroaluminate ionic liquid was prepared from the reaction of Merrifield resin with 1-methylimidazole followed by reaction with aluminum chloride. This Lewis acidic ionic liquid is environmentally friendly heterogeneous catalyst for the Knoevenagel condensation of aromatic and aliphatic aldehydes with ethyl cyanoacetate. The catalyst is stable (as a bench top catalyst) and reusable.

Polystyrene-Supported Pyridinium Chloroaluminate Ionic Liquid as a New Heterogeneous Lewis Acid Catalyst for Knoevenagel Condensation

Non-hygroscopic polystyrene-supported chloroaluminate ionic liquid was prepared from the reaction of Merrifield resin with pyridine followed by reaction with aluminium chloride. This Lewis acidic ionic liquid is an environmentally friendly heterogeneous catalyst for the Knoevenagel condensation of aromatic and aliphatic aldehydes with ethyl cyanoacetate. The catalyst is stable (as a bench top catalyst) and can be easily recovered and reused without appreciable change in its efficiency.

ChemInform Abstract: Silica Supported Ammonium Acetate: An Efficient and Recyclable Heterogeneous Catalyst for Knoevenagel Condensation Between Aldehydes or Ketones and Active Methylene Group in Liquid Phase.

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Silica Supported Ammonium Acetate: An Efficient and Recyclable Heterogeneous Catalyst for Knoevenagel Condensation between Adehydes or Ketones and Active Methylene Group in Liquid Phase

A simple and efficient method has been developed for Knoevenagel condensation between aldehydes or ketones and active methylene group by stirring in methylene chloride at 60 °C under heterogeneous conditions using silica supported ammonium acetate. The products are obtained in excellent yields and are in a state of high purity. The structures of the products were confirmed by IR, 1 H NMR and mass spectral data and comparison with authentic samples available commercially.