Oxidation Of Organic Sulfides Research Articles

Recent Advances in Catalytic Oxidation of Organic Sulfides: Applications of Metal-Ionic Liquid Catalytic Systems.

Catalytic oxidation of organic sulfides is of considerable significance in industrial chemistry and fuel industry. Therefore, numerous methods have been developed for the oxidation. Metal-containing ionic liquid-based catalysts can catalyze the selective oxidation reactions and are highly used in chemical processes, which have also been used as effective solvents, reaction media, extractants, and catalysts for the oxidation of organic sulfides including oxidative desulfurization of fuel oil. Recently, much attention is being drawn to the preparation of heterogenous catalysts based on the immobilization of metal- or nonmetal-containing ILs on diverse solid supports, which can be easily separated after the completion reaction and recycled. Therefore, there is still an increasing interest in developing new and efficient catalytic procedures for the oxidation of organic sulfides. In this review, we have outlined the recent advances in catalytic oxidation of organic sulfides including oxidative desulfurization of fuel oil. The versatilities and adaptabilities of metal–ionic liquid catalytic systems in the selective oxidation of sulfides are considered a powerful research field in these transformations.

Olefin-linked covalent organic framework nanotubes based on triazine for selective oxidation of sulfides with O2 powered by blue light

Imine, hydrazone, and olefin-linked covalent organic frameworks (COFs) prosper in visible light photocatalysis. Markedly, the olefin-linked COFs are usually superior in transfer of π-conjugated electron powered by visible light albeit their construction is more challenging. Herein, two olefin-linked COFs were forged between 2,4,6-trimethyl-1,3,5-triazine (TMT) and 2,4,6-tris(4-formyl-phenyl)-1,3,5-triazine (TFPT) or 1,3,5-tris(4-formyl-phenyl)-benzene (TFPB) to afford TTO-COF or TBO-COF, respectively. Both of the olefin-linked COFs based on triazine are of good crystallinity, uniform micropores, and high specific surface areas, but of different morphologies, namely nanotubes and nanosheets. Compared to TBO-COF, TTO-COF nanotubes were constructed with two building blocks based on triazine, which could not only improve the planarity of a single layer but also cause closer stacking of layers in between. Therefore, TTO-COF nanotubes exhibit better photocatalytic performance and stability in the selective oxidation of organic sulfides into corresponding sulfoxides with O2 powered by blue light. Mechanistic investigation evidence the formation of desired sulfoxides was shaped by both electron and energy transfer pathways over TTO-COF nanotubes. This work underlines the ascendancy of olefin-linked COFs inasmuch as they provide an effective platform to construct efficient and durable photocatalysts based on adaptable organic building blocks.

Dysprosium (III) Supported on CoFe2O4 MNPs as a Heterogeneous Catalyst for the Selective Oxidation of Sulfides and Synthesis of Symmetrical Disulfides

A magnetic catalyst based on immobilization of dysprosium ions on the surface of CoFe2O4 nanoparticles has been reported and used as an efficient magnetic nanocatalyst for the selective oxidation of organic sulfides and synthesis of symmetrical disulfides containing aromatic and aliphatic sulfides and thiols. The magnetic solid catalyst has been identified using TGA, FT-IR, VSM, ICP, SEM, and XRD. Moreover, the catalyst can also be separated with an external magnet and recycled several times without any remarkable decrease in its catalyst activity.

Effect of redox potential on manganese-mediated benzylalcohol and sulfide oxidation

Tridentate 1,3-bis(2 ′ -Ar-imino)isoindolinato manganese(II) complexes were found to efficiently catalyze the mild oxidation of organic sulfides to sulfoxides and benzyl alcohols to benzaldehydes with mCPBA and PhIO, but they proved almost ineffective by the use of tBuOOH and H2O2 at room temperature. The effect of electron-withdrawing and electron-donating substituents on the substrates (thioanisole and benzylalcohol), and the redox properties of the metal center by varying the aryl groups on the bis-iminoisoindoline were investigated, and showed a significant impact on the catalytic C–H oxidation and sulfoxidation reactions. Based on these results, including the linear correlations between the oxidation reactivity of the catalysts and Mn III /Mn II redox potentials, the Hammett correlation with ρ=-0.27 for 4R-PhSMe and ρ=-0.27 for 4R-PhCH2OH, electrophilic oxomanganese(IV) intermediate has been suggested as key oxidant. Furthermore, the small negative slope (-0.5) from the logk rel versus E ox o for 4R-PhSMe gives clear evidence for the direct oxygen atom transfer (OAT) mechanism instead of electron transfer (ET) mechanism between the Mn IV O and PhSMe.

Green synthesis of a vanadium(V) Schiff base complex by grinding method: study on its catalytic and anti-bacterial activity

A facile protocol was developed for the green synthesis of a Schiff base and its vanadium(V) complex. The compounds were derived from salicylaldehyde, diethylenetriamine and vanadyl sulfate by applying grinding method to overcome environmental issues with solvents. The reactions took place rapidly and products were isolated pure. The compounds were characterized with elemental, EDX, mass spectrometry, magnetic susceptibility, molar conductance, UV-vis, FTIR and NMR analysis. The synthesized vanadium(V) complex was an efficient and selective catalyst towards oxidation of organic sulfides and alcohols. The oxidation reactions were conducted under microwave irradiation as well as conventional heating. A reaction mechanism has been proposed for the catalytic oxidation reactions. The mechanism was further established by using GAUSSIAN16 suite. The complex also showed good anti-bacterial activity against Gram-positive and Gram-negative bacteria.

A Donor-Acceptor [2]Catenane for Visible Light Photocatalysis.

Colored charge-transfer complexes can be formed by the association between electron-rich donor and electron-deficient acceptor molecules, bringing about the narrowing of HOMO-LUMO energy gaps so that they become capable of harnessing visible light. In an effort to facilitate the use of these widespread, but nonetheless weak, interactions for visible light photocatalysis, it is important to render the interactions strong and robust. Herein, we employ a well-known donor-acceptor [2]catenane-formed by the mechanical interlocking of cyclobis(paraquat-p-phenylene) and 1,5-dinaphtho[38]crown-10-in which the charge-transfer interactions between two 4,4'-bipyridinium and two 1,5-dioxynaphthalene units are enhanced by mechanical bonding, leading to increased absorption of visible light, even at low concentrations in solution. As a result, since this [2]catenane can generate persistent bipyridinium radical cations under continuous visible-light irradiation without the need for additional photosensitizers, it can display good catalytic activity in both photo-reductions and -oxidations, as demonstrated by hydrogen production-in the presence of platinum nanoparticles-and aerobic oxidation of organic sulfides, such as l-methionine, respectively. This research, which highlights the usefulness of nanoconfinement present in mechanically interlocked molecules for the reinforcement of weak interactions, can not only expand the potential of charge-transfer interactions in solar energy conversion and synthetic photocatalysis but also open up new possibilities for the development of active artificial molecular shuttles, switches, and machines.

Ultra-small and highly dispersive iron oxide hydroxide as an efficient catalyst for oxidation reactions: a Swiss-army-knife catalyst

Ultra-small and highly dispersive (< 10 nm) iron oxide hydroxide is characterized by some methods. The compound is an efficient and stable catalyst for alcohol oxidation, organic sulfide oxidation, and epoxidation of alkenes in the presence of H2O2. The electrochemical oxygen-evolution reaction of the iron oxide hydroxide is also tested under acidic, neutral, and alkaline conditions. In the presence of the iron oxide hydroxide, excellent conversions (75–100%) and selectivities of substrates (92–97%), depending on the nature of the sulfide, were obtained. Benzylalcohols having electron-donating and-withdrawing substituents in the aromatic ring were oxidized to produce the corresponding aldehydes with excellent conversion (65–89%) and selectivity (96–100%) using this iron oxide hydroxide. The conversion of styrene and cyclooctene toward the epoxidation in the presence of this catalyst are 60 and 53%, respectively. Water oxidation for the catalysts was investigated at pH 2, 6.7, 12, and 14. The onset of OER at pH 14 is observed with a 475 mV overpotential. At 585 mV overpotential, a current density of more than 0.18 mA/cm2 and a turnover frequency of 1.5/h is observed. Operando high-resolution visible spectroscopy at pH 14, similar to previously reported investigations, shows that Fe(IV)=O is an intermediate for water oxidation.

Dye-TiO2/SiO2 assembly photocatalysis for blue light-initiated selective aerobic oxidation of organic sulfides

Previous attempts of incorporating TiO2 with porous SiO2 (TiO2/SiO2) to elevate the photocatalytic activity within the visible region have encountered with limited success. Therefore, light-harvesting molecules like alizarin red S (ARS) could be assembled onto TiO2/SiO2 to circumvent this bottleneck. Herein, a series of TiO2/SiO2 with different molar ratios were fashioned by the sol–gel and ensuing calcination method. Thereafter, ARS was conveniently assembled onto these TiO2/SiO2 under reaction conditions of selective aerobic oxidation of sulfides under the illumination of 460 nm blue light-emitting diodes (LEDs). Moreover, a redox mediator TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)oxyl) could boost the electron transfer from the light-excited ARS to sulfides which in turn alleviates the destruction of ARS assembled on TiO2/SiO2 (molar ratio, 1/3). The more abundant surface hydroxyl groups of SiO2 than TiO2 could ameliorate selectivities for sulfoxides. A wide range of organic sulfides can be converted into sulfoxides with above 90% selectivities and conversions over ARS-TiO2/SiO2 assembly and 2 mol% TEMPO. The positive involvement of an insulator like SiO2 represents a way forward both in scope and in depth for dye-semiconductor photocatalysis during selective transformations.

Catalytic oxidation of organic sulfides by new iron-chloro Schiff base complexes: The effect of methoxy substitution and ligand isomerism on the electronic, electrochemical and catalytic performance of the complexes

Four new Fe(III)-Chloro Schiff base complexes were synthesized and characterized. The N2O2 type tetradentate Schiff base ligands were synthesized from the condensation of meso-1,2-diphenyl-1,2-ethylenediamine with salicylaldehyde (H2L1), 3-methoxysalicylaldehyde (H2L2), 4-methoxysalicylaldehyde (H2L3) and 5-methoxysalicylaldehyde (H2L4). The corresponding iron-chloro complexes with the general formula [Fe(Ln)Cl] (n = 1–4 for complexes (1–4)) were characterized by FTIR and UV–Vis spectroscopy and elemental analysis. Crystal structure of (1) was obtained by single-crystal X-ray crystallography. Cyclic voltammetry was used to study the electrochemistry of the complexes. The complexes were used as catalysts for the selective oxidation of organic sulfide compounds to sulfoxides. High catalytic performance and selectivity were obtained. The spectroscopic, electrochemical and catalytic data are discussed based on the electronic, steric and electrochemical properties of the complexes.

Accelerated Oxidation of Organic Sulfides by Microdroplet Chemistry.

We report the rapid oxidation of organic sulfides to sulfoxides by means of microdroplet chemistry at room temperature using a spray solution containing an organic sulfide dissolved in water/methanol, dilute (11%-14%) sodium hypochlorite (NaClO), and 5% chloroauric acid (HAuCl4). Ultrasonic nebulization, easy ambient sonic-spray ionization, or electrosonic spray ionization serves as the microdroplet source. High-resolution mass spectrometry was used as an online detector, and nuclear magnetic resonance was used as an offline detector. We found that the sulfoxide yields vary between 66 and 95%, the highest rate of product formation is 195 mg/min for benzyl phenyl sulfoxide, and the time required is a few minutes, which is much less than that required for the conventional means of achieving this chemical transformation. We also applied this microdroplet method to protein fingerprinting. We found that protein sequences containing methionine can be quickly oxidized, providing useful information for protein structure determinations.

Magneli-type tungsten oxide nanorods as catalysts for the selective oxidation of organic sulfides.

Selective oxidation of thioethers is an important reaction to obtain sulfoxides as synthetic intermediates for applications in the chemical industry, medicinal chemistry and biology or the destruction of warfare agents. The reduced Magneli-type tungsten oxide WO3-x possesses a unique oxidase-like activity which facilitates the oxidation of thioethers to the corresponding sulfoxides. More than 90% of the model system methylphenylsulfide could be converted to the sulfoxide with a selectivity of 98% at room temperature within 30 minutes, whereas oxidation to the corresponding sulfone was on a time scale of days. The concentration of the catalyst had a significant impact on the reaction rate. Reasonable catalytic effects were also observed for the selective oxidation of various organic sulfides with different substituents. The WO3-x nanocatalysts could be recycled at least 5 times without decrease in activity. We propose a metal oxide-catalyzed route based on the clean oxidant hydrogen peroxide. Compared to other molecular or enzyme catalysts the WO3-x system is a more robust redox-nanocatalyst, which is not susceptible to decomposition or denaturation under standard conditions. The unique oxidase-like activity of WO3-x can be used for a wide range of applications in synthetic, environmental or medicinal chemistry.

Deep eutectic solvent mediated controlled and selective oxidation of organic sulfides and hydroxylation of arylboronic acids

A mild and efficient protocol has been developed for the controlled oxidation of wide variety of organic sulfides to corresponding sulfoxides using deep eutectic solvent (DES) as catalyst and hydrogen peroxide as oxidant under ambient condition. In presence of benzyl alcohols along with sulfides, DES selectively oxidizes only the sulfides to corresponding sulfoxides. The DES is prepared by using zirconium oxychloride and urea (1:5 ​M ratio) which is thermally stable up to 213 ​°C. The prepared DES can also be effectively applied for hydroxylation of arylbronic acids without using any additional catalyst and solvent.

Photocatalytic Molecular Oxygen Activation by Regulating Excitonic Effects in Covalent Organic Frameworks.

Excitonic effects caused by Coulomb interactions between electrons and holes play subtle and significant roles on photocatalysis, yet have been long ignored. Herein, porphyrinic covalent organic frameworks (COFs, specifically DhaTph-M), in the absence or presence of different metals in porphyrin centers, have been shown as ideal models to regulate excitonic effects. Remarkably, the incorporation of Zn2+ in the COF facilitates the conversion of singlet to triplet excitons, whereas the Ni2+ introduction promotes the dissociation of excitons to hot carriers under photoexcitation. Accordingly, the discriminative excitonic behavior of DhaTph-Zn and DhaTph-Ni enables the activation of O2 to 1O2 and O2•-, respectively, under visible light irradiation, resulting in distinctly different activity and selectivity in photocatalytic terpinene oxidation. Benefiting from these results, DhaTph-Ni exhibits excellent photocatalytic activity in O2•--engaged hydroxylation of boronic acid, while DhaTph-Zn possesses superior performance in 1O2-mediated selective oxidation of organic sulfides. This work provides in-depth insights into molecular oxygen activation and opens an avenue to the regulation of excitonic effects based on COFs.

Interfacial self-assembled thioxathone monolayers on the surfaces of silica nanoparticles as efficient heterogeneous photocatalysts for the selective oxidation of aromatic thioethers under air atmosphere

Selective oxidation of organic sulfide under mild conditions has attracted growing attention because of its potential applications for the chemical transformation and degradation of toxic organics. Thioxanthones (TXs) are important photosensitizers for the photocatalytic oxidation of organic sulfides. This paper reports the fabrication of TX-functionalized silica nanocomposites, using a bottom-up self-assembling technique, and their application as heterogeneous photocatalysts for the selective oxidation of sulfides into sulfoxides. Two types of TXs, 3-hydroxy-9H-thioxanthen-9-one (TXOH) and 9-oxo-9H-thioxanthene-2,7-dicarboxylic acid (TXCOOH), were synthesized, and their monolayers were anchored covalently on the surface of silica nanoparticles (nanoSiO2) via surface silanization and substitution reactions. The produced nanoSiO2TX and nanoSiO2TXCOOH composites emitted blue luminescence with an emission wavelength at approximately 430−434 nm; they exhibited a ∼10 nm red shift compared to TXOH and TXCOOH. Both nanocomposites acted as heterogeneous photocatalysts for the selective oxidation of aromatic thioethers into sulfoxides under mild conditions (radiation, air atmosphere, and room temperature). Good conversion efficiency and selectivity were obtained, particularly for those aromatic thioethers with benzyl- and electron-donating substituents. Since the TX monolayer was anchored covalently on the surface of nanoSiO2 particles, the nanocomposites displayed good reusability and recyclability, in addition to facile separation of the reagents and photocatalysts from the reaction system.

Highly Selective Oxidation of Organic Sulfides by a Conjugated Polymer as the Photosensitizer for Singlet Oxygen Generation.

A cationic conjugated polyelectrolyte PPET3-N2 was used as a photosensitizer for photocatalytic oxidation of organic sulfides, including thioanisole, ethyl phenyl sulfide, 4-methylphenyl methyl sulfide, etc., to form sulfoxides with good yields and high selectivity. Oxidation reactions were performed in both batch and microfluidic reactors, where the microfluidic reactor can significantly promote the conversion of photocatalytic oxidation reaction to over 98% in about 8 min. Further studies of the photocatalytic oxidation of the antitumor drug ricobendazole in the microfluidic reactor demonstrate the potential application of the polymer material in organic reactions given its high selectivity, good efficiency, and operation convenience.

Oxidation of sulfides in aqueous media catalyzed by pyrazole-oxidoperoxido-molybdenum(VI) complexes

The complex [MoO(O2)2(pyrazole)2] (1) is an effective catalyst for the oxidation of organic sulfides (methylphenylsulfide and diphenylsulfide). Reactions can be run in water as the only medium, at low temperature (25 °C), with low catalyst loadings (0.2 mol%) and excellent H2O2 efficiency with no significant non-productive decomposition of the oxidant. Under conditions that favor sulfone formation, the overall process, including isolation of the precipitated product (by filtration or centrifugation) and recycling of the aqueous phase containing the catalyst, can be performed in the absence of organic or ionic liquid solvents. Catalytic results with the recycled aqueous phase were the same as those obtained in the first cycle. With water as the sole solvent, 1 is a superior catalyst to the 3,5-dimethylpyrazole complexes [MoO(O2)2(dmpz)2] (2) and [Hdmpz]4[Mo8O25.8(O2)0.2(dmpz)2]·4H2O (3). Crystal structures for 1 and 3 are presented.

Study of Organic Sulfide Oxidation on the Modified Graphite Electrodes by Co, Fe and Ni Nano Particles

Electro-oxidation of methyl phenyl sulfide with the aim of producing sulfoxide and sulfone was investigated over Ni, Co, Fe, and their alloys on graphite electrodes in the acetic acid as a non-toxic solvent. The modified electrodes were prepared by cyclic voltammetry technique. The surface morphology of electrodes was investigated by scanning electron microscopy and the presence of metal nanoparticles on the graphite was investigated by X-ray diffraction. The catalytic treatment and synergistic effects of the modified electrodes were studied by electrochemical techniques such as cyclic voltammetry (CV) and chronoamperometry (CA). It was found the performance of all the modified electrodes is successful. In the attendance of methyl phenyl sulfide, the graphite/CoFe modified electrode (G/CoFe) showed the highest performance for electro-oxidation also there was a linear relationship between the square root of the scan rate and anodic current in low scan rates, that indicates a diffusion controlled process. The diffusion coefficient, heterogeneous electron transfer rate constant and electron transfer coefficient were determined for methyl phenyl sulfide electrochemical oxidation. Electro-oxidation of methyl phenyl sulfide by electrolysis method was investigated and its results were studied by gas chromatograph (GC). Based on GC studies, the electro-oxidation of methyl phenyl sulfide by electrolysis produced methyl phenyl sulfoxide and methyl phenyl sulfone. Also, a mechanism for electro-oxidation of sulfide was proposed. The using of non-noble metals as the electrocatalyst for the first time for the organic sulfide electro-oxidation, the very easy, affordable and fast preparation of the modified electrode, high performance of the modified electrode, no need of using oxidant and co-catalyst and designing a homogeneous media with proper conductivity for oxidation of insoluble in water compounds demonstrate important items for the use of this procedure and electrode in the subsequent investigation of sulfides.

Selective and solventless oxidation of organic sulfides and alcohols using new supported molybdenum (VI) complex in microwave and conventional methods

A new dioxo‐molybdenum (VI) complex supported on functionalized Merrifield resin (MR‐Mo) has been synthesized and characterized by elemental, scanning electron mcroscopy, energy‐dispersive X‐ray analysis, TGA, Brunauer–Emmett–Teller method, powder‐X‐ray diffraction, Fourier transform infrared, X‐ray photoelectron spectroscopy and DRS–UV–vis analysis. The virgin Merrifield resin (MR) was functionalized by carbonylation followed by Schiff base formation with ethanolamine (MR‐SB). Experimental data showed that the Schiff base coordinated with the MoO22+ moiety via O‐ and N‐atoms. The catalytic activity of MR‐Mo was explored under solventless conditions toward the oxidation of organic sulfides and alcohols using 30% aqueous H2O2 as oxidant. The oxidation reactions were conducted under microwave and conventional methods. The microwave‐assisted oxidation reactions were found to be many times faster than the conventional methods. The oxidation reactions were selective and formed sulfoxides or aldehydes as the sole product with superior TOF values among the molybdenum (VI)‐based complexes. Besides these, the MR‐Mo was purely heterogeneous in nature and can be recycled for at least five reaction cycles without the loss of catalytic efficiency and product selectivity.

Catalytic oxidation of organic sulfides by H2O2 in the presence of titanosilicate zeolites

Titanosilicate ferrierite zeolite (FER) and its delaminated form (ITQ-6), with various Si/Ti molar ratios, were synthetized and tested as catalysts for diphenyl sulfide (Ph 2 S) and dimethyl sulfide (DMS) oxidation with H 2 O 2 . The zeolites were characterized with respect to their chemical composition (ICP-OES), structure (XRD, UV–vis DRS) and texture (low-temperature N 2 adsorption-desorption). Titanium in the FER and ITQ-6 samples was present mainly in the zeolite framework with a significant contribution of titanium in the extraframework positions. Titanosilicate zeolites of FER and ITQ-6 series were found to be active catalysts of diphenyl and dimethyl sulfides oxidation by H 2 O 2 to sulfoxides (Ph 2 SO/DMSO) and sulfones (Ph 2 SO 2 /DMSO 2 ). The efficiency of these reactions depends on the porous structure of the zeolite catalysts – conversion of larger molecules of diphenyl sulfide was significantly higher in the presence of delaminated zeolite Ti-ITQ-6 due to the possibility of the interlayer mesopores penetration by reactants. On the other side diphenyl sulfide molecules are too large to be accommodated into micropores of FER zeolite. The efficiency of dimethyl sulfide conversion, due to relatively small size of this molecule, was similar in the presence of Ti-FER and Ti-ITQ-6 zeolites. For all catalysts, the organic sulfide conversion was significantly intensified under UV irradiation. It was suggested that Ti cations in the zeolite framework, as well as in the extraframework, species play a role of the single site photocatalysts active in the formation of hydroxyl radicals, which are known to be effective oxidants of the organic sulfides. ⁃ Ti-FER and Ti-ITQ-6 are active catalysts of Ph 2 S and DMS oxidation with H 2 O 2 . ⁃ Delaminated structure of Ti-ITQ-6 is more effective in oxidation of Ph 2 S molecules. ⁃ UV irradiation increases efficiency of diphenyl and dimethyl sulfides oxidation.

Selective Catalytic Oxidation of Organic Sulfides to Sulfoxides without Forming Sulfones over Solid Molybdenum Blue: Kinetic and Thermodynamic Studies

The present investigation reports studies on the selective catalytic oxidation of organic sulfide substrates over molybdenum blue catalyst supported on boron phosphate. The catalyst was synthesized through partial precipitation method and characterized by XRD, FTIR and SEM techniques. The sulfoxidation was carried out in a batch reactor using benzyl phenyl sulfide as the substrate over the present catalyst and the reaction parameters were varied and optimized. The results were compared with the MoO3 impregnated boron phosphate. The catalyst was also studied for its performance over other sulfide substrates and the results were compared with available studies in literature. The reaction followed pseudo first-order kinetics and rate of the reaction under optimized condition was 10.1 × 10-3 min-1, with energy of activation of 29.3 kJ/mol. The Mo-O-Mo bridging and -Mo=O bonds present in molybdenum blue were participating in the reaction and possible mechanism has been proposed. The 100% selectivity of the product towards sulfoxide has been attributed to the big-wheel structure of molybdenum blue as it sterically hinders further reaction of sulfoxides formed to sulfones.