Catalyst For Oxidation Of Sulfides Research Articles

Application of sodium titanate nanotubes doped with vanadium (VNaTNT) as a heterogeneous catalyst for oxidation of sulfides at room temperature

A heterogeneous titanate nanotube (TNT) catalyst containing TiO2, Na, and V has been synthesized and used in the chemoselective oxidation of sulfides to the corresponding sulfoxides in the presence of 30% H2O2 in water. Some of the advantages of our method include excellent yields, heterogeneous conditions, simplicity, compatibility with a variety of functionalities, and ease of isolation of the products. Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and N2 adsorption were used for structural and textural characterization of the catalyst (VNaTNT).

New metal complexes supported on Fe3O4 magnetic nanoparticles as recoverable catalysts for selective oxidation of sulfides to sulfoxides

Fe3O4 nanoparticles were coated with aminopropyltriethoxysilane and subsequently reacted with isatin to obtain imine‐bonded Fe3O4 nanoparticles. The addition of ZrOCl2⋅8H2O or CuCl2 led to the formation of complexes of Zr(IV)/isatin@Fe3O4 or Cu (II)/isatin@Fe3O4 as new magnetically separable catalysts. The synthesized catalysts were characterized using various techniques. These catalysts are shown to be efficient for chemo‐selective oxidation of sulfides to sulfoxides using hydrogen peroxide as oxidative agent. This system has many advantages, such as excellent level of reusability of magnetic catalysts, high yields, simplicity of separation of catalysts using an external magnet, environmental benignity and ease of handling. Copyright © 2016 John Wiley & Sons, Ltd.

Preparation and characterization of oxovanadium(IV)-glycine imine immobilized on magnetic nanoparticles and its catalytic application for selective oxidation of sulfides to sulfoxides

A novel Fe3O4@VO (salen) complex was designed as an efficient and heterogeneous catalyst for selective oxidation of sulfides to sulfoxides using H2O2 at room temperature. The catalyst was characterized by techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, Fourier-transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), vibrating-sample magnetometry (VSM), and inductively coupled plasma optical emission spectrometry (ICP-OES) analysis. The simple preparation of the catalyst from commercially available materials, excellent chemoselectivity, easy separation of products, and straightforward recovery and reusability of the catalyst with unaltered activity make our procedure a green and practical method.

Synthesis, characterization and catalytic evaluation of H3PW12O40 included in acrylic acid/acrylamide polymer for the selective oxidation of sulfides

A series of hybrid materials (SAPTPA) based on tungstophosphoric acid H3PW12O40 (TPA) included in acrylic acid/acrylamide polymer (SAP) were synthetized. The samples were characterized by FT-IR, XRD, 31P MAS-NMR, DTA-TGA, and the acidic properties were determined by means of potentiometric titration with n-butylamine. Materials with 10, 20, 30 and 40% (w/w) TPA content in the solid (SAPTPA10, SAPTPA20, SAPTPA30 and SAPTPA40, respectively) were prepared by impregnating the polymer with tungstophosphoric acid water solutions. According to FT-IR and 31P MAS-NMR studies, the main species present in the samples is the [PW12O40]3− anion, which was partially transformed into [P2W21O71]6− and [PW11O39]7− anions during the synthesis and drying steps.Taking into account XRD results, these species are highly dispersed in the polymer matrix or appear as noncrystalline phases. The DTA-TGA results show that SAPTPA materials did not undergo any remarkable chemical changes up to 200°C. Additionally, the SAPTPA materials showed strong acid sites whose number increased as the TPA content in them was higher.The materials obtained by impregnation of TPA onto the polymer matrix present suitable physicochemical properties to be used as catalysts in the selective oxidation of sulfides to the corresponding sulfoxide/sulfone using acetonitrile as solvent and H2O2 35% w/v as a clean oxidant.The SAPTPA40 catalyst was appropriate for the selective sulfide oxidation in heterogeneous conditions and can be reused without significant loss of its catalytic activity. A convenient and selective procedure for oxidizing sulfides to sulfoxides or sulfones by varying the H2O2/substrate ratio and the temperature was found.

Preparation of DSA@MNPs and application as heterogeneous and recyclable nanocatalyst for oxidation of sulfides and oxidative coupling of thiols

Dopamine sulfamic acid-functionalized magnetic Fe3O4 nanoparticles (DSA@MNPs) were prepared by a very simple and inexpensive procedure using commercial materials and characterized by X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and vibrating-sample magnetometry (VSM) techniques. They were employed as an efficient and recoverable catalyst in oxidation of sulfides to sulfoxides and oxidative coupling of thiols to disulfides using hydrogen peroxide as green oxidant at room temperature. This is the first report of application of DSA@MNPs in organic reactions. The supported magnetic nanoparticles could be easily recovered using an appropriate external magnet, minimizing catalyst loss during separation, and reused for several times without any loss of catalytic activity. Also, the amount of sulfamic acid function in the DSA@MNPs was calculated from ion-exchange pH analysis and back titration.

Synthesis and characterization of insoluble cobalt(II), nickel(II), zinc(II) and palladium(II) Schiff base complexes: Heterogeneous catalysts for oxidation of sulfides with hydrogen peroxide

The condensation reaction of 1,2-bis(2′-aminophenoxy)benzene with 2-pyridinecarbaldehyde in a mole ratio of 1:2 gives a new Schiff base ligand (L). Four Schiff base complexes, CoL(NO3)2 (1), NiLCl2 (2), ZnL(NO3)2 (3) and Pd2LCl4 (4) have been prepared by direct reaction of the ligand (L) and appropriate metal salts. The Schiff base ligand (L) has been characterized by IR, 1H NMR and 13C NMR spectroscopy and elemental analysis. Also, all complexes have been characterized by IR and XRD spectroscopy techniques and elemental analysis. The synthesized complexes have very poor solubility in all polar and non-polar solvents such as: H2O, MeOH, EtOH, CH3CN, DMSO, DMF, CHCl3, CH2Cl2, THF, etc; therefore, they have been used as heterogeneous catalysts. Catalytic performance of the complexes was studied in oxidation of thioanisole using hydrogen peroxide (H2O2) as the oxidant. Various factors including the reaction temperature, amount of oxidant and catalyst amount were optimized. The palladium Schiff base complex, Pd2LCl4 (4), shows better catalytic activity than other complexes. Therefore, the Pd(II) Schiff base complex has been used as a catalyst for oxidation of different sulfides to their corresponding sulfones in acetonitrile with hydrogen peroxide as the oxidant. The palladium Schiff base complex, Pd2LCl4 (4), has shown a very good recyclability, up to five times, without any appreciable decreases in catalytic activity and selectivity.

An organic–inorganic hybrid supramolecular framework material based on a [P2W18O62]6−cluster and Yb & Na complexes of pyridine-2,6-dicarboxylic acid: a catalyst for selective oxidation of sulfides in water with H2O2

A rare-earth-containing polyoxometalate (RECP) hybrid, {(Yb (PDCH2)2(PDCH))·Na(H2O)2·(Na(PDCH)(H2O)2)}2[P2W18O62]·14H2O (1), based on [P2W18O62]6− cluster anions and cationic Yb & Na complex units of pyridine-2,6-dicarboxylic acid (PDCH2) has been synthesized under normal reaction conditions, which exhibited a supramolecular 3-D framework structure in the crystal lattice. Hybrid 1 acts as a green catalyst for the selective oxidation of sulfides in water with H2O2 as the reagent.

Synthesis and characterization of two binuclear nickel(II) complexes of thiophenol-based “end-off” compartmental ligands and their application as catalysts for selective oxidation of sulfides

Reaction of the binucleating S-protected ligand precursors 2-(N,N-dimethylthiocarbamato)-5-methylisophthalaldehyde di-2′-hydroxy anil (I) and 2-(N,N-dimethylthiocarbamato)-5-methylisophthalaldehyde di-2′-hydroxy 5′-methyl anil (II) with nickel(II) acetate tetrahydrate in the presence of pyrazole afforded the binuclear nickel(II) complexes [LINi2(pz)] (1) and [LIINi2(pz)] (2), respectively. The complexes have been characterized by routine physicochemical studies as well as by X-ray single crystal structure analysis. In both complexes, Ni(II) ions are doubly bridged by the thiophenolic sulfur of the pentadentate Schiff base ligand and a pyrazolate group. Efficient protocols for the oxidation of sulfides to sulfoxides with high selectivities, catalyzed by binuclear μ-thiophenolato-μ-pyrazolatonickel(II) in the presence of urea hydrogen peroxide (UHP) were explored. We obtained predominantly the monooxygenated product. The resulting products are obtained in good to excellent yields within a reasonable time.

Efficient preparation of Zr(IV)-salen grafted mesoporous MCM-41 catalyst for chemoselective oxidation of sulfides to sulfoxides and Knoevenagel condensation 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 properties of the synthesized materials were investigated by a number of analytical techniques including X-ray diffraction, N2 sorption-desorption, thermogravimetric analysis, Fourier transform infrared spectroscopy, inductively coupled plasma atomic emission spectroscpopy, and energy dispersive X-ray spectroscopy. Catalytic studies of the mesoporous materials functionalized with Zr(IV)-Schiff base complexes were investigated and extended to selective oxidation of sulfides to sulfoxides and the Knoevenagel condensation reactions of aldehydes with malononitriles and ethyl cyanoacetate. Additionally, catalyst recycling of the Zr-salen-MCM-41 materials was also studied.

Synthesis and characterization of Copper (II) Schiff base complex containing MCM-41 as robust and clean nano reactor catalyst for the selective oxidation of sulfides to sulfoxides using H2O2

An efficient and versatile procedure has been introduced for the preparation of copper supported on functionalized mesoporous silica (MCM-41) containing chelating Schiff base salen (the structure of this functionalized silica complex was studied by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, thermo gravimetric analysis and N2 adsorption and desorption), which has been applied as catalyst for the conversion of various sulfides into sulfoxides with aqueous hydrogen peroxide. Also this heterogeneous catalyst can be recovered easily and reused many times for the oxidation of sulfides without significant loss of activity and selectivity.

Zirconium oxide complex‐functionalized MCM‐41 nanostructure: an efficient and reusable mesoporous catalyst for oxidation of sulfides and oxidative coupling of thiols using hydrogen peroxide

Zirconium oxide complex‐functionalized mesoporous MCM‐41 (Zr‐oxide@MCM‐41) as an efficient and reusable catalyst is reported for the oxidation of sulfides into sulfoxides using hydrogen peroxide (H2O2) as the oxidant, with short reaction times in good to excellent yields at room temperature under solvent‐free conditions. Also, a simple and efficient method is reported for the oxidative coupling of thiols into corresponding disulfides in good to high yields using H2O2 as oxidant in the presence of Zr‐oxide@MCM‐41 as recoverable catalyst in ethanol at room temperature. A series of sulfides and thiols possessing functional groups was successfully converted into corresponding products. After completion of reactions the catalyst was easily separated with simple filtration from the reaction mixture and reused for several consecutive runs without significant loss of catalytic efficiency. The mesoporous catalyst was characterized using Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller surface area measurements, X‐ray diffraction, transmission and scanning electron microscopies, energy‐dispersive X‐ray spectroscopy and thermogravimetric analysis. Copyright © 2015 John Wiley & Sons, Ltd.

Highly Selective Oxidation of Sulfides to Sulfones by H2O2 Catalyzed by Porous Capsules

In this study, selective oxidation of different sulfides to the corresponding sulfone with hydrogen peroxide in the presence of W72Fe30 is reported. W72Fe30 is as an efficient catalyst for the selective oxidation of sulfides to sulfones, in high to excellent yields using 30 % hydrogen peroxide as an oxidant under optimum reaction conditions. Various sulfides containing functional groups such as double bond and hydroxyl group are successfully and selectively oxidized without affecting sensitive functionalities. Oxidation of sulfides to corresponding sulfone by H2O2 in the presence of W72Fe30

Preparation and Characterization of Organically Modified MCM-48 as Heterogonous Catalyst for Oxidation of Sulfides and Thiols

MCM-48 mesoporous synthesized and grafted with aminopropyl triethoxysilane (APTES) and subsequently reacted by isatin to obtain the imine of MCM-48. Addition of ZrOCl2·8H2O, leading to form the complex of Zr(IV)/isatin-MCM-48 as new Schiff base complex of zirconium(IV)-modified-MCM-48. The synthesized catalyst was characterized by XRD, TGA, FT-IR and BET. The resulting catalyst was efficient for selective oxidation of sulfides to sulfoxides and oxidation of thiols to disulfides with hydrogen peroxide. In this method isolation and reusability of catalyst have been investigated

Tungstate Supported on Periodic Mesoporous Organosilica with Imidazolium Framework as an Efficient and Recyclable Catalyst for the Selective Oxidation of Sulfides.

A catalyst based on immobilization of tungstate ions (WO4 2- ) inside the mesochannels of periodic mesoporous organosilica comprising bridged ionic liquid (1,3-bis(3-trimethoxysilylpropyl)imidazolium chloride) has been synthesized and characterized. This catalyst was then employed for the selective oxidation of organic sulfides to the corresponding sulfoxides or sulfones. The final synthesized catalyst was characterized by various techniques such as nitrogen sorption analysis, transmission electron microscopy, and thermogravimetric analysis. The catalyst was also applied to the selective oxidation of sulfides containing readily oxidizable functional groups such as hydroxyl, allylic, and even challenging aliphatic sulfides. Interestingly, it was found that on changing the reaction medium from aqueous methanol to aqueous acetonitrile, the product selectivity was changed successfully from sulfoxide to sulfone with good to excellent yields. Moreover, the catalyst can also be recovered and reused efficiently in nine subsequent reaction cycles without any remarkable decrease in the catalyst activity and selectivity.

Carbon-supported metal-modified lacunary tungstosilicic polyoxometallates used as catalysts in the selective oxidation of sulfides

Lacunary tungstosilicic polyoxometallates modified with transition metal ions [SiW11O39M(H2O)]6−, where M=Mn2+, Fe2+, Co2+or Cu2+, were synthesized and supported on activated carbon to obtain the SiW11MC catalysts. The samples were characterized by FT-IR, XRD, N2 adsorption–desorption measurements, and the acidic properties were determined using the isopropanol dehydration test reaction.The activity and selectivity of the catalysts were evaluated in the selective oxidation of a series of sulfides to sulfoxides or sulfone. The reaction was carried out in acetonitrile as solvent using H2O2 35% p/V as a clean oxidant. The conversion values decreased in the following order: SiW11MnC>SiW11FeC>SiW11CuC>SiW11CoC. The catalysts were reused without appreciable loss of their catalytic activity. It was found that the activity of the catalysts decreases in parallel with the increment in the reduction temperature values. The most easily reducible catalyst displayed the highest conversion values. We found a convenient and selective procedure for oxidizing sulfides to sulfoxides or sulfones using aqueous hydrogen peroxide and a catalytic amount of lacunary tungstosilicic polyoxometallates supported on carbon at low temperatures (20–50°C) in a reasonably short reaction time.

Tetrabutylammonium tribromide impregnated MCM-48 as a heterogeneous catalyst for selective oxidation of sulfides

We report here tetrabutylammonium tribromide supported on MCM-48 as a highly efficient heterogeneous catalyst for the selective oxidation of sulfides, in ethanolic medium using hydrogen peroxide as an oxidant.

Cellulose Sulfuric Acid: As an Efficient Bio Polymer Based Catalyst for the Selective Oxidation of Sulfides and Thiols by Hydrogen Peroxide

Cellulose sulfuric acid as a bio-polymer based solid catalyst efficiently catalyzes the selectively oxidation of sulfides to sulfoxides and thiols to disulfides using hydrogen peroxide as a green oxidant with good yields at room temperature. The developed method offers a number of advantages such as high selectivity, mild reaction conditions, simple operation, cleaner reaction profiles, low cost and biodegradability of the catalyst.

Engineering chiral Fe(salen)-based metal-organic frameworks for asymmetric sulfide oxidation.

Two chiral porous Fe(salen)-based metal-organic frameworks are constructed and are shown to be efficient and recyclable heterogeneous catalysts for asymmetric oxidation of sulfides to sulfoxides with an enantioselectivity of up to 96%.

Salen copper(II) complex heterogenized on mesoporous MCM-41 as nano-reactor catalyst for the selective oxidation of sulfides using urea hydrogen peroxide (UHP)

MCM-41 silica spheres were synthesized and functionalized with 3-aminopropyltriethoxysilane (3-APTES). The Schiff base has been derived from amino groups and 5-boromo salicylaldehyde, then a tetra dentate Cu(II)–Schiff base complex was prepared. This compound was characterized by X-ray diffraction, nitrogen physisorption, UV–Vis spectrometer, transmission electron micrographys (TEM), IR-spectra, and TGA/DTA technique. The prepared grafting Cu-salen-MCM-41 over a mesoporous surface was found to be an efficient and selective catalyst for the oxidation of different sulfides into sulfoxides with urea hydrogen peroxide (UHP) giving excellent yields at room temperature. The results showed that Cu-salen-MCM-41 is an effective catalyst for the oxidation of sulfides and can be repeatedly used and regenerated with no significant decrease in its catalytic ability. They also showed that the prepared material retained a good mesoporous structure and the best catalytic properties.

{Mo132} Nanoball as an Efficient and Cost-Effective Catalyst for Sustainable Oxidation of Sulfides and Olefins with Hydrogen Peroxide

Atom-efficient and selective oxidation of sulfides to sulfoxides and sulfones in water and epoxidation of olefins in ethanol with hydrogen peroxide catalyzed by Keplerate nanoball polyoxomolybdate {Mo132} under heterogeneous conditions are reported. The reaction yield and selectivity was affected crucially by catalyst concentration. A structurally diverse set of sulfides and olefins were transformed into desired oxidation products regardless of the electronic nature of the substituents. In spite of the heterogeneous reaction mixtures throughout the work, no difficulties with reaction progress were noted. Products were isolated easily from green media, and the catalyst could be reused several times without any appreciable decrease in catalytic activity and selectivity. Accelerated reactions under ultrasonic irradiation did not change the selectivity of the oxidation products.