Oxidation Of Thioanisole Research Articles

Mixed‐Valence Vanadium (IV/V) Glycolates and Lactates with N‐Heterocycle Ligands: Localized Structures and Catalytic Oxidation of Thioanisole

Dimeric mixed‐valence vanadium (IV/V) glycolates and lactates with N‐heterocycle ligands, [V2O3(phen)3(glyc)]Cl·7H2O (1), [V2O3(phen)3(S‐lact)]Cl·5.5H2O (2), (NH4)2[V2O3(bpy)2(glyc)2]Cl·4H2O (3), (NH4)[V2O3(bpy)2(S‐lact)2]·7H2O (4) and (NH4)2[V2O3(bpy)2(R,S‐lact)2]Cl·H2O (5), have been isolated in a wide pH range from weak acidic to alkaline solutions (H2glyc = glycolic acid, H2lact = lactic acid, phen = 1,10‐phenanthroline, bpy = 2,2′‐bipyridine). The glycolates and lactates in 1 and 2 chelate to VV whereas in 3–5 chelate to VIV and VV with α‐alkoxy and α‐carboxy groups. These complexes feature interesting localized O=VIV–O–VV=O bridging structures, which are supported by structural analyses, bond valance calculations, UV/Vis, EPR experiments and exhibit different electrochemical behaviors. These complexes were further used for the selective oxidation of thioanisole to methyl phenyl sulfoxide.

Bioinorganic Laboratory Experiment: Synthesis and Catalytic Activity of a Vanadium Haloperoxidase Model Complex

Laboratory experiments that offer interdisciplinary experiences for students are appealing and are increasingly popular additions to undergraduate chemistry curricula. Students can capitalize on their knowledge of multiple areas of chemistry while working through an application, and this fosters the development of progressive problem-solving skills. In this laboratory experiment, students combine the fields of inorganic chemistry with biological chemistry to synthesize and test the catalytic activity of a model of vanadium haloperoxidase, an enzyme naturally produced in certain brown- and red-seaweed species. Students use 1H NMR spectroscopy to monitor the oxidation of thioanisole to methyl phenyl sulfoxide using their prepared vanadium complex as the catalyst.

Selective oxidation of thioanisole by titanium complexes immobilized on mesoporous silica nanoparticles: elucidating the environment of titanium(iv) species

The coordination environment of titanium of the catalysts was investigated by DRUV–vis, Raman and 47/49Ti MAS-NMR spectroscopies and solid-state electrochemical techniques.

Fluorescence Spectroscopic Insight into the Supramolecular Interactions in DNA-Based Enantioselective Sulfoxidation.

Interactions of copper(II)-bipyridine cofactors and thioanisole substrate with human telomeric G-quadruplex DNA were studied by UV/Vis absorption, circular dichroism, and fluorescence quenching titration. Three copper(II)-bipyridine complexes are equivalently anchored to the G-quadruplex scaffold at all five fluorescently labeled sites. Thioanisole interacts with the DNA architecture at both the second loop and 3' terminus in the absence or presence of copper(II)-bipyridine complexes. These nonspecificities in the weak interactions of CuII complexes and thioanisole with G-quadruplex might explain why DNA only affords a modest enantioselectivity in the oxidation of thioanisole. These findings provide insights toward the construction of highly enantioselective DNA-based catalysts.

Synthesis, structure, spectroscopic characterization and catalytic activity of chiral dioxidomolybdenum(VI) Schiff base complexes derived from R(−)-2-amino-1-propanol

Ten new chiral cis-dioxidomolybdenum(VI) complexes with tridentate Schiff bases were synthesized by monocondensation of R(−)-2-amino-1-propanol with salicylaldehyde and its derivatives. Their spectroscopic properties have been investigated UV-Vis, CD, IR, one- (1H, 13C) and two-dimensional (COSY, gHSQC and NOESY) NMR techniques. The single-crystal X-ray analysis of the {R(−)-2-[(1-oxidopropyl)iminomethyl]-4-methylphenolato-κ3N,O,O’}(methanol)dioxidomolybdenum(VI) reveals a distorted octahedral geometry. After optimization of reaction conditions, catalytic activity of these complexes in oxidation of olefins, i.e. styrene and cyclohexene, with aqueous 30% H2O2 or tert-butyl hydroperoxide (TBHP) as an oxidant were tested. Moreover, the molybdenum(VI) Schiff base complexes are also able to catalyze the oxidation of thioanisole to methyl phenyl sulfoxide in presence of aqueous 30% H2O2.

Can Manganese(III)‐Iodosylarene Act as an Oxidant Alongside High‐Valent Manganese(V)‐Oxo Complexes?

AbstractMetalloenzymes often utilize a high‐valent metal‐oxo species in their catalytic cycle that is formed through a combination of reduction/proton transfer steps from O2. In biomimetic chemistry, by contrast, the use of molecular oxygen is challenging and instead addition of iodosylarenes as terminal oxidants generates these high‐valent metal‐oxo intermediates. There has been controversy in the literature for many years, whether the iodosylarene (or one of its side‐products in a reaction with a metal center) can act as an active oxidant. Herein, we present a comprehensive theoretical study on the thioanisole oxidation by a range of possible oxidants originating from a reaction mixture of a Mn(III) complex with iodosylbenzene. We show here that actually there are multiple isomeric iodosylarene complexes in solution and a number of those react with substrates with rate‐determining barriers at par with high‐valent metal‐oxo species. In particular, the [MnIII(PhIO)], [MnV(O)(PhIO)] and [MnIV(O)‐I(Ph)‐O•] complexes are identified as competitive oxidants and as such care should be taken with interpreting experimental rate constants.

Ratio-Controlled Precursors of Anderson-Evans Polyoxometalates: Synthesis, Structural Transformation, and Magnetic and Catalytic Properties of a Series of Triol Ligand-Decorated {M2Mo6} Clusters (M = Cu2+, Co2+, Ni2+, Zn2+).

A series of triol ligand [CH3C(CH2OH)3] covalently decorated polyoxometalates (POMs), which could be ascribed to the primary complexes with structural formulas {M2[Mo2O4(CH3C(CH2O)3)2]3}2- (M = Cu2+, Co2+, Ni2+, Zn2+), have been synthesized in organic solvents. Single-crystal X-ray structural analysis reveals that the synthesized polyanionic clusters are comprised of three {Mo2} units and two divalent transition-metal ions connecting to each other in an alternating style, where all {Mo2} blocks were covalently decorated by two triol ligands in the trans conformation. The 1/3 molar ratio of M/Mo in the prepared complexes was higher than those ratios in typical Anderson-Evans, Wells-Dawson, and Keggin POMs. With a decrease in the M/Mo molar ratio of a Mo-contained reactant to 1/6 and/or the addition of acetic acid to the reaction solution, the primary complexes acting as precursors transformed continuously into the corresponding triol-ligand-decorated Anderson-Evans POMs. Detailed investigations were conducted by using different isopolymolybdates in various solvent environments, and several Anderson-Evans POMs in different triol-ligand-decorated fashions were obtained from the primary complexes. In addition, we also realized the transformation between the Anderson-Evans clusters in different decoration fashions by simply controlling the acidity in solution. Magnetic measurement showed a general property, but the catalytic experiments demonstrated that CoII- and Zn II-containing POMs displayed a higher efficiency for the selective oxidation of thioanisole to sulfoxide.

Bifunctional Porphyrin-Based Nano-Metal-Organic Frameworks: Catalytic and Chemosensing Studies.

The use of 5,10,15,20-tetrakis( p-phenylphosphonic acid)porphyrin (H10TPPA) as a linker in the preparation of porphyrin-based metal-organic frameworks (Por-MOFs) through coordination to lanthanides cations is reported. The resulting unprecedented materials, formulated as [M(H9TPPA)(H2O) x]Cl2· yH2O [ x + y = 7; M3+ = La3+ (1), Yb3+ (2), and Y3+ (3)], prepared using hydrothermal synthesis, were extensively characterized in the solid-state, for both their structure and thermal robustness, using a myriad of solid-state advanced techniques. Materials were evaluated as heterogeneous catalysts in the oxidation of thioanisole by H2O2 and as chemosensors for detection of nitroaromatic compounds (NACs). Nano-Por-MOFs 1-3 proved to be effective as heterogeneous catalysts in the sulfoxidation of thioanisole, with Por-MOF 1 exhibiting the best catalytic performance with a conversion of thioanisole of 89% in the first cycle and with a high selectivity for the sulfoxide derivative (90%). The catalyst maintained its activity roughly constant in three consecutive runs. Por-MOFs 1-3 can be employed as chemosensors because of a measured fluorescence quenching up to 70% for nitrobenzene, 1,4-dinitrobenzene, 4-nitrophenol, and phenol, with 2,4,6-trinitrophenol exhibiting a peculiar fluorescence profile.

Selective Oxidation of Thioanisole with Hydrogen Peroxide using Copper Complexes Encapsulated in Zeolite: Formation of a Thermally Stable and Reactive Copper Hydroperoxo Species

[Cu(terpy)]2+ complexes encapsulated into Na-Y zeolite ([Cu(terpy)]2+@Y) were prepared, and their catalytic activities for the oxidation of sulfides using hydrogen peroxide were investigated. Several spectroscopic results, as well as elemental analysis, demonstrated the formation of [Cu(terpy)]2+ complexes in supercages of Y-zeolite. [Cu(terpy)]2+@Y exhibited high selectivity for the oxidation of thioanisole into methylphenylsulfoxide when H2O2 was used. The kinetic study of this oxidation at the catalyst [Cu(terpy)]2+@Y suggests that the reaction of [Cu(terpy)]2+ species with H2O2 is the rate-determining step. The oxidation of thioanisole, benzene, and 2-phenylethylamine using [[Cu(terpy)]2+@Y]*, which was prepared from the reaction between [Cu(terpy)]2+@Y and H2O2, quantitatively proceeded to methylphenylsulfoxide, phenol, and 2-amino-1-phenylethanol, respectively. The reaction of [Cu(terpy)]2+@Y and H2O2 was found to yield thermally stable but active CuII-OOH species in [Cu(terpy)]2+@Y.

Decorated‐magnetic‐nanoparticle‐supported bromine as a recyclable catalyst for the oxidation of sulfides

ABSTRACTHerein, we present a strategy for supporting bromine as a catalyst for the oxidation of sulfides. In this strategy, branched poly(ethylene imine) was first decorated by magnetic oxide and then used to support liquid bromine to obtain solid polymeric bromine (M@PEI@Br) nanoparticles. Compared with free bromine, the stability of the M@PEI@Br nanoparticles improved obviously. The oxidation of thioanisole to methyl phenyl sulfoxide was chosen as a reaction model to evaluate the catalytic activity of the M@PEI@Br nanoparticles. All of the obtained results verify that the M@PEI@Br nanoparticles exhibited excellent catalytic efficiency and could accelerate the oxidation process under solvent‐free conditions at room temperature; this highlighted the potential of decorated polymers to support active and unstable small‐molecule organic catalysts. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46036.

Two New Sandwich-Type Polyoxomolybdates Functionalized with Diphosphonates: Efficient and Selective Oxidation of Sulfides to Sulfones.

Two sandwich-type polyoxomolybdates Na8[MO2{Mo2O5(O3PCH3C(O)PO3)}2] (M = Ni2+ (1); Co2+ (2)) were synthesized by one-pot reaction of Na2HPMo12O40·14H2O, 1-hydroxy ethidene diphosphonic acid (HEDP=HOC(CH3)(PO3H2)2), and (1) NiCl2/CoCl2 (2). Compounds 1 and 2 were characterized by single crystal X-ray analysis, X-ray powder diffraction (XRPD), IR spectroscopy, 31P NMR spectra, UV-vis spectroscopy, and thermogravimetric analyses (TGA). Structural analysis reveals that 1 and 2 exhibit similar centrosymmetric structure, which consists of one transition metal (TM) ion sandwiched by two same subunits {Mo2O5(O3PCH3C(O)PO3)}. The clusters 1 and 2 show efficient catalytic activities for oxidation of thioanisole. Moreover, they are catalytically selective for oxidizing thioanisole. Both resuable polyoxomolybdates 1 and 2 catalysts show good thermo- and hydrolytic stability. It is noted that compound 1 shows outstanding catalytic activity for oxidation of various sulfides to corresponding sulfones with 93–100% selectivity at 97–100% conversion in one hour under mild conditions, which is potentially valuable to the removal of organic sulfides.

W–N–TiO2 with positive enough level of valence band maximum and narrowing bandgap for selective aerobic oxidation in visible-light irradiation

A kind of surface complex (triethylamine and mesoporous W–N–TiO2 microspheres with large surface area: 117.5 m2g−1) catalysis was achieved via visible-light photoredox catalysis. Triethylamine behaves as a true redox mediator due to its highly favorable donating ability. With a lower bandgap (2.43 eV) and higher valence band maximum (2.905 V), W–N–TiO2 has the ability to play an active catalytic role yielding excellent conversion and selective oxidation of thioanisole (75.16%) within 12 h under visible-light irradiation. In addition, the reaction and the photocatalyst are applicable to other kinds of thioethers, generally producing high conversion rates and selectivities for the product sulfoxides. The reaction paths were elucidated to reveal that these kinds of surface complexes show characteristics that are likely to be applicable to many aerobic oxidation reactions in future.

Bicarbonate-activated hydrogen peroxide and efficient decontamination of toxic sulfur mustard and nerve gas simulants

13C NMR spectra showed that peroxymonocarbonate (HCO4−) was generated in the NaHCO3-activated H2O2 solution and pH was a key factor in its production. A cycle for the bicarbonate anion was proposed as HCO3−→HCO3 → (CO2)2*→CO2(aq)→HCO4− (H2CO4)→HCO3− (HCO3) basing on the results of NMR, electron paramagnetic resonance, chemiluminescence analysis. In this cycle, (CO2)2* was the key intermediate and (CO2)2*→2CO2+hv was the rate controlling step. Thioanisole and paraoxon, the simulants of sulfur mustard gas and nerve gas, respectively, were efficiently decontaminated by the NaHCO3-activated H2O2 solution. While HCO4− was the primary oxidant for the oxidation of thioanisole, O2− generated during the decomposition of HCO4− or H2O2 led to the secondary oxidation of the sulfide. Paraoxon was degraded in the NaHCO3-activated H2O2 solution via nucleophilic substitution by OOH− and OH−, and the degradation rate increased exponentially with increasing pH. Alkali metal ions had a catalytic effect on the degradation of paraoxon. Mustard gas and soman degraded efficiently into nontoxic products in NaHCO3-activated H2O2. A pH range of 9–10 was found to be optimum for the broad-spectrum decontamination of chemical warfare agents and other eco-toxicants using NaHCO3-activated H2O2.

Rate and Selectivity Control in Thioether and Alkene Oxidation with H2O2 over Phosphonate‐Modified Niobium(V)–Silica Catalysts

AbstractSupported metal oxide catalysts are versatile materials for liquid‐phase oxidations, including alkene epoxidation and thioether sulfoxidation with H2O2. Periodic trends in H2O2 activation was recently demonstrated for alkene epoxidation, highlighting Nb‐SiO2 as a more active and selective catalyst than Ti‐SiO2. Three representative catalysts are studied consisting of NbV, TiIV, and ZrIV on silica, each made through a molecular precursor approach that yields highly dispersed oxide sites, for thioanisole oxidation by H2O2. Initial rates trend Nb>Ti≫Zr, as for epoxidation, and Nb outperforms Ti for a number of other thioethers. In contrast, selectivity to sulfoxide vs. sulfone trends Ti>Nb≫Zr at all conversions. Modifying the Nb‐SiO2 catalyst with phenylphosphonic acid does not completely remove sulfoxidation reactivity, as it did for photooxidation and epoxidation, and results in an unusual material active for sulfoxidation but neither epoxidation nor overoxidation to the sulfone.

Green, inexpensive, and fast conversion of sulfides to sulfoxides by multiusable Mo(VI) macrocyclic Schiff base complex supported on Fe3O4 nanoparticles in solvent-free conditions

In the present study, the macrocyclic-based Mo(VI) Schiff base complex was harbored on Fe 3 O 4 nanoparticles and characterized by X-ray powder diffraction, scanning electron microscope, energy-dispersive X-ray spectroscopy, infrared spectroscopy, transmission electron microscopy, vibrating sample magnetometry, diffuse reflectance spectra, and atomic absorption spectroscopy. Separable nanocatalyst was tested under solvent-free conditions for the oxidation of methyl phenyl sulfide, diphenyl sulfide, benzyl phenyl sulfide, dipropyl sulfide, dibutyl sulfide, dimethyl sulfide, bis (4-hydroxyphenyl) sulfide, diallyl sulfide, and benzothiophene using H 2 O 2 (30% in water) as green oxidant. This catalyst is very efficient for thioanisole oxidation with 100% conversion in 3 min. We were able to separate the nanocatalyst magnetically using external magnetic field and to apply the catalyst at least six consecutive times without a significant decrease in conversion. Remarkable and excellent turnover frequency of the catalyst was obtained to oxidize the thioanisole (526,000 h −1 ), dimethyl sulfide (526,000 h −1 ), diallyl sulfide (526,000 h −1 ), dibutyl sulfide (521,000 h −1 ), and dipropyl sulfide (500,000 h −1 ). The prepared nanocatalyst has been beneficial in catalytic activity, selectivity, reaction time, and reusability with easy separation.

Heterogeneous Organophosphate Ethanolysis: Degradation of Phosphonothioate Neurotoxin by a Supported Molybdenum Peroxo Polymer.

A polystyrene-supported molybdenum peroxo material [Mo-Y(s)] was applied toward the oxidative degradation of the organophosphate neurotoxin O,S-diethylphenyl phosphonothioate (1) through ethanolysis. In addition to the operational advantages of the heterogeneous reactivity, oxidative ethanolysis with a 10-fold excess of hydrogen peroxide yields only P-S bond scission to produce diethylphenyl phosphonate and ethyl sulfate. This is the first report of a molybdenum solid support that promotes the degradation of sulfur-containing organophosphate with the turnover benefits of heterogeneous catalysis. The activation parameters of 1 ethanolysis by Mo-Y(s) (Ea = 57 ± 6 kJ/mol and ΔS⧧ = -124 ± 21 J/mol·K) and by the model compound oxodiperoxo(pyridine-2-carboxylato)molybdate(VI) bis(pyridine-2-carboxylic acid) monohydrate (3; Ea = 55 ± 5 kJ/mol and ΔS⧧ = -154 ± 15 J/mol·K) are almost identical for the oxidation of thioanisole by 3. This suggests that the rate-determining step for 1 ethanolysis is sulfur oxidation to form an intermediate phosphonothioate S-oxide, which subsequently undergoes nucleophilic attack by the ethanol solvent to form diethylphenyl phosphonate and ethyl sulfate. Evidence for the formation of this S-oxide intermediate and the postulated ethanolysis mechanism is provided.

Synthesis, characterization and catalytic activity of dioxidomolybdenum(VI) complexes with tridentate Schiff bases derived from 1R,2S(−)-norephedrine

New chiral dioxidomolybdenum(VI) complexes with tridentate Schiff base ligands obtained by monocondensation of 1R,2S(−)-norephedrine with salicylaldehyde and its derivatives were synthesized. The complexes were characterized by elemental analysis and by their IR, CD, UV–vis, one- (1H) and two-dimensional (COSY, gHSQC and NOESY) NMR spectra. After optimization of reaction conditions, catalytic activity of these complexes were tested in the oxidation of olefins, i.e. styrene and cyclohexene, using aqueous 30% H2O2 or tert-butyl hydroperoxide (TBHP) as an oxidant. Moreover, the dioxidomolybdenum(VI) Schiff base complexes have also ability to catalyze the oxidation of thioanisole to methyl phenyl sulfoxide in presence of aqueous 30% H2O2.

Targeting of High-Valent Iron-TAML Activators at Hydrocarbons and Beyond.

TAML activators of peroxides are iron(III) complexes. The ligation by four deprotonated amide nitrogens in macrocyclic motifs is the signature of TAMLs where the macrocyclic structures vary considerably. TAML activators are exceptional functional replicas of the peroxidases and cytochrome P450 oxidizing enzymes. In water, they catalyze peroxide oxidation of a broad spectrum of compounds, many of which are micropollutants, compounds that produce undesired effects at low concentrations-as with the enzymes, peroxide is typically activated with near-quantitative efficiency. In nonaqueous solvents such as organic nitriles, the prototype TAML activator gave the structurally authenticated reactive iron(V)oxo units (FeVO), wherein the iron atom is two oxidation equivalents above the FeIII resting state. The iron(V) state can be achieved through the intermediacy of iron(IV) species, which are usually μ-oxo-bridged dimers (FeIVFeIV), and this allows for the reactivity of this potent reactive intermediate to be studied in stoichiometric processes. The present review is primarily focused at the mechanistic features of the oxidation by FeVO of hydrocarbons including cyclohexane. The main topic is preceded by a description of mechanisms of oxidation of thioanisoles by FeVO, because the associated studies provide valuable insight into the ability of FeVO to oxidize organic molecules. The review is opened by a summary of the interconversions between FeIII, FeIVFeIV, and FeVO species, since this information is crucial for interpreting the kinetic data. The highest reactivity in both reaction classes described belongs to FeVO. The resting state FeIII is unreactive oxidatively. Intermediate reactivity is typically found for FeIVFeIV; therefore, kinetic features for these species in interchange and oxidation processes are also reviewed. Examples of using TAML activators for C-H bond cleavage applied to fine organic synthesis conclude the review.

Green oxidation of sulfides in solvent-free condition by reusable novel Mo(VI) complex anchored on magnetite as a high-efficiency nanocatalyst with eco-friendly aqueous H2O2

In this research work, a novel molybdenum N4-type Schiff base complex anchored covalently on magnetite nanoparticles and characterized perfectly using physico-chemical techniques and it was applied for oxidation of sulfides. The effects of solvent, reaction temperature and amount of catalysts by 30% aqueous H2O2 as environmental friendly oxidant on oxidation catalytic process were optimized. The best results in solvent-free condition was obtained. The catalyst was tested for oxidation of thioanisole, Diphenyl sulfide, Benzyl phenyl sulfide, dipropyl sulfide, dibutyl sulfide, dimethyl sulfide, bis(4-hydroxyphenyl) sulfide, diallyl sulfide and benzothiophene. The presented nanocatalyst is so effective for selective oxidation of thioanisole, dimethyl sulfide, dibutyl sulfide and diallyl sulfide with a >99% conversion, and excellent turnover frequency (93,000h−1<) in shortest time (5min). The magnetic nanocatalyst was easily recovered by using an external magnetic field and employed at least six successive times without significant decreasing in conversion.

Synthesis, structural characterization, DFT studies and catalytic properties of dinuclear oxidovanadium(V) complexes derived from adipohydrazone ligands

Two new dinuclear oxidovanadium(V) complexes, [V2O2(L1)(OCH3)2(CH3OH)2]·2(CH3OH) (1) and [V2O2(L2)(OCH3)2(CH3OH)2]·2(CH3OH) (2), were synthesized from the reaction of VO(acac)2 and hexa-dentate N2O4-donor hydrazone ligands (H4L1 and H4L2) in methanol solvent. The ligands and complexes were characterized by elemental analysis and spectroscopic methods. Single crystal X-ray analysis of the brown crystals of complexes 1 and 2 indicated that these complexes are dinuclear oxidovanadium(V) complexes which the metal ions have distorted octahedral geometry. There are several strong and directed hydrogen bonding interactions in the crystal packing of 1 and 2 which stabilize their crystalline format. The catalytic activity of these complexes was tested in the oxidation of thioanisole using H2O2. These studies indicated both complexes have high catalytic activity in the oxidation of thioanisole. The complexes were further studied by DFT and TDDFT theoretical calculations.