- Cu(II)-catalyzed oxidation of thiols by superoxide ligated to Co III2
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Copper(II) dramatically catalyzes the oxidation of thiols by a superoxide bridging two CoIII ions. The catalyzed path overwhelmingly dominates over the uncatalysed path and is first order in the superoxo complex concentration. The first-order rate constants show a first-order dependence in [Cu2+], a second-order dependence in [thiol] and linearly varies with [H+]-3. On the basis of observed kinetics reported here, it is proposed that Cu(II) reacts with two thiol molecules to form a Cu II(thiol)2 complex, an electron is transferred from one ligated thiol to the CuII center to form CuI(thiol) and a thiyl radical. The copper(I)-thiol complex is oxidized by the conjugate base of the title complex to regenerate CuII(thiol). A CuII/I catalytic cycle is thus believed to be responsible for the observed catalysis. Copyright
- Mishra, Ritu,Banerjee, Rupendranath,Mukhopadhyay, Subrata
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- Improvement of a process for synthesis of thioglycolic acid
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An environmentally clean process was proposed for synthesis of thioglycolic acid by condensation of monochloroacetic acid with sodium disulfide, followed by electrochemical reduction of the resulting mixture.
- Islamgulova,Shitova,Akhmerova,Tomilov
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- Cu(II) catalyzed oxidation of mercaptoacetic acid by methylene blue in acidic medium: Influence of solvent and morphology
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Kinetic studies on the Cu(II) catalyzed oxidation of mercaptoacetic acid (thioglycolic acid, TGA) by the model electron receptor methylene blue in acidic medium show that the reaction follows a second order kinetics in TGA. The order in methylene blue is unity but at higher [TGA], the order is 3/4. The rate shows an inverse relationship with [H+] and a second order dependence on [Cu(II)]. The reaction conforms to Arrhenius behavior in aqueous medium but resorts to anti-Arrhenius behavior in aqueous methanol and in aqueous acetone media. The reaction involves the in situ participation of nanoparticles which has been confirmed by SEM, XRD, and FTIR techniques. In aqueous medium, cauliflower shaped nanoparticles (44.21-74.33 nm) are obtained but in the presence of acetone and methanol, nanogranules (38.96-70.73 nm) and nanodisks (47.30-72.16 nm), respectively, are produced at 35°C as revealed by SEM images and XRD data. The reaction is characterized by the participation of two transition states in aqueous acetone medium and the kinetics of the reaction, especially the temperature dependence, is governed by the adsorption of methylene blue on copper nanoparticles as influenced by morphology inter alia dielectric constant of the reaction medium.
- Sharma, Ranjana,Pal, Mahender,Mishra
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- Determination of Thioglycolic Acid and Dithiodiglycolic Acid in Mineral Flotation Systems
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When aqueous solution of thioglycolic acid are equilibrated with sphalerite, a zinc sulfide mineral, a large fraction of the thioglycolic acid is either adsorbed on the sphalerite surface or oxidized ot dithiodiglycolic acid.The total concentration of thioglycolic and dithioglycolic acid in solution has been determined by molecular emission cavity analysis (MECA).The fraction of the thioglycolic acid that is not adsorbed on the mineral surface and remains in solution has been determined by a coulometric titration in which iodine is electrogenerated in situ and the endpoint located by an amperometric method.Attempts to determine the thioglycolic acid that was adsorbed on the mineral surface directly by MECA gave unreliable results.This has been attributed to the wide variation in the surface area as well as the surface chemical composition of small samples (1-2 mg) of the mineral that must be useed in the sample cup in MECA.Thioglycolic acid also leaches traces of metal ions from the mineral surface.The concentration of zinc(II) in solution reflects the extent of leaching that has occurred.
- McLean, McLean,Wagenen, Stan Van,Wiedemann, Donna,Fernando, Quintus,Raghavan, Srini
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- Soft template induced phase selective synthesis of Fe2O3 nanomagnets: One step towards peroxidase-mimic activity allowing colorimetric sensing of thioglycolic acid
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Different Schiff's base (SB) templates have been obtained to mediate phase selective synthesis of α- or γ-Fe2O3 from the same temperature condition. The inherent phase transformation tendency (γ-Fe2O3 to α-Fe2O3) is found to be inhibited. Again, the phase selective evolution emerges out of the binding modes of SBs which has been illustrated here. The nature of SBs governs the shape and size distribution of Fe2O3 NPs. As both the phases are magenetically active, easy magnetic separation of them widens their applicability in catalysis. Magnetically active both α- and γ-Fe2O3 mimic interesting peroxidase like activity by oxidising colourless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue coloured oxidised product (Ox-TMB) in aqueous H2O2. These results prompted us to improvise further to detect thioglycolic acid (TGA) at a micromolar level which provides commercial applicability.
- Roy, Anindita,Sahoo, Ramkrishna,Ray, Chaiti,Dutta, Soumen,Pal, Tarasankar
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- l-Arginine complex of copper on modified core–shell magnetic nanoparticles as reusable and organic–inorganic hybrid nanocatalyst for the chemoselective oxidation of organosulfur compounds
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In this paper, we report the fabrication and characterization of a stable heterogeneous nanostructure catalyst of copper immobilized on Fe3O4@SiO2@l-Arginine, for the oxidation of sulfides and oxidative coupling of thiols. The prepared nanocatalyst has been characterized by different techniques such as FTIR, XRD, SEM, TEM and TGA. These nanoparticles were the effective catalyst for selective oxidation of sulfides and oxidative coupling of thiols using 30% H2O2. The suggested method offers several prominent advantages such as mild condition, use of magnetically reusable catalyst, simple workup procedure, good to high yields of products and great selectivity.
- Nikoorazm, Mohsen,Moradi, Parisa,Noori, Nourolah,Azadi, Gouhar
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p. 467 - 478
(2020/09/01)
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- Synthesis and Characterization of Magnetic Functionalized Ni and Cu Nano Catalysts and Their Application in Oxidation, Oxidative Coupling and Various Multi-Component Reactions
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Abstract: Two magnetic nano catalysts of nickel and copper, Fe3O4@SiO2@DOP-BenPyr-M(II), (M=Ni and Cu) have been synthesized. These catalysts were applied as recoverable, efficient and new heterogeneous catalysts for the high yielding and room temperature one-pot procedure of selective oxidation of sulfides to sulfoxides and oxidative coupling of thiols to disulfides. In addition, the catalytic activity of Fe3O4@SiO2@DOP-BenPyr-Ni(II) was investigated as heterogeneous nanocatalyst for synthesis of 2,3-dihydroquinazolin-4(1H)-ones, 5-substituted 1H-tetrazoles and polyhydroquinolines. The synthesized catalysts were characterized by FT-IR, TGA, XRD, VSM, EDX, ICP and SEM techniques. These catalysts were recovered by an external magnet and reused several times without significant loss of catalytic efficiency. Graphic Abstract: [Figure not available: see fulltext.]
- Hajjami, Maryam,Sheikhaei, Shiva,Gholamian, Fatemeh,Yousofvand, Zakieh
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p. 2420 - 2435
(2021/01/04)
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- Fe3O4@MCM-41@Zn-Arg: as a novel, magnetically recoverable and ecofriendly nanocatalyst for the synthesis of disulfides, sulfoxides and 2,3-dihydroquinazolin?4(1H)?ones
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The direct supporting of Zn-arginine complex on magnetic core-shell nanostructures (Fe3O4@MCM-41@Zn-Arg) was reported as a novel, heterogeneous and excellent nanocatalyst, which applied for the oxidation reaction of sulfides to sulfoxides, oxidative coupling of thiols to their corresponding disulfides and the synthesis of 2,3-dihydroquinazolin-4(1H)-one derivatives under mild conditions. The structure of the catalyst was studied by X-Ray diffraction, Fourier transform-infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, atomic absorption spectroscopy, and vibrating sample magnetometry techniques. The simple experimental procedure, very good catalytic activity, low cost, and excellent recycling are the noteworthy features of the currently employed heterogeneous catalytic system.
- Nikoorazm, Mohsen,Erfani, Zahra
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p. 642 - 655
(2020/08/19)
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- Synthesis and characterization of VO–vanillin complex immobilized on MCM-41 and its facile catalytic application in the sulfoxidation reaction, and synthesis of 2,3-dihydroquinazolin-4(1H)-ones and disulfides in green media
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In this work, a vanillin complex is immobilized onto MCM-41 and characterized by FT-IR, X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, thermogravimetric analysis, and BET techniques. This supported Schiff base complex was found to be an efficient and recoverable catalyst for the chemoselective oxidation of sulfides into sulfoxides and thiols into their corresponding disulfides (using hydrogen peroxide as a green oxidant) and also a suitable catalyst for the preparation of 2,3-dihydroquinazolin-4(1H)-one derivatives in water at 90°C. Using this protocol, we show that a variety of disulfides, sulfoxides, and 2,3-dihydroquinazolin-4(1H)-one derivatives can be synthesized in green conditions. The catalyst can be recovered and recycled for further reactions without appreciable loss of catalytic performance.
- Nikoorazm, Mohsen,Khanmoradi, Maryam
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p. 1477 - 1489
(2020/03/11)
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- SUPER-HYDROPHOBIC ELECTROTHERMAL EPOXY RESIN COMPOSITE MATERIAL AND PREPARATION AND SELF-REPAIRING METHOD THEREFOR
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Superhydrophobic electrothermal epoxy composites, their preparation and a self-healing method are disclosed. 1,4,5-oxadithiepane-2,7-dione and methylhexahydrophthalic anhydride were mixed and cured with epoxides to get self-healable epoxy resins; carbon nanotube/self-healable epoxy resin prepolymers were coated on self-healable epoxy resins and cured to get electrothermal epoxy composites; modified superhydrophobic copper powders were adhered on electrothermal epoxy composites and cured to get a kind of superhydrophobic electrothermal epoxy composites. The thermal resistance of superhydrophobic electrothermal epoxy composites is superior to existed technical solutions and they can simultaneously repair cracking and delamination and the healed samples still exhibit excellent superhydrophobicity. These merits of superhydrophobic electrothermal epoxy composites provided in this invention can meet the harsh requirements of self-healing and removing ice on surfaces of wind turbine blades, suggesting good abilities of guaranteeing service safety and lifespan of wind turbine blades.
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- Mild and highly efficient method for the oxidation of sulfides and oxidative coupling of thiols catalyzed by Fe3O4@MCM-41@VO-SPATB as efficient and magnetically recoverable nanocatalyst
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The use of oxo vanadium complex with s-propyl-2-aminobenzothioate ligand immobilized onto functionalized magnetic nanoporous MCM-41(Fe3O4@MCM-41@VO-SPATB) as efficient and magnetically recoverable nanocatalyst for oxidation of sulfides into sulfoxides and oxidative coupling of thiols into disulfides using H2O2 as green oxidant is presented. This method provides much improved modification of oxidation reactions in terms of mild reaction conditions, short reaction time and good-to-excellent yields of products. Another important feature of this method is the ability to reuse the magnetite nanocatalyst for several times with no loss of its catalytic activity.
- Nikoorazm, Mohsen,Ghorbani, Farshid,Ghorbani-Choghamarani, Arash,Erfani, Zahra
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p. 553 - 562
(2019/02/17)
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- An efficient clean methodology for the C-S coupling to aryl thioethers and S-S homocoupling to aromatic disulfides catalyzed over a Ce(IV)-leucine complex immobilized on mesoporous MCM-41
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A novel Ce(iv)-anchored l-leucine covalently bonded to mesoporous MCM-41 has been synthesized by a non-hydrothermal post-functionalization approach. It has been thoroughly characterized by sophisticated physicochemical techniques. The material was applied in the efficient green synthesis of aromatic sulfides by C-S coupling using molecular sulfur and haloarenes. Another catalytic application was in the synthesis of symmetric disulfides by the homocoupling of aromatic thiols in the presence of H2O2 as an oxidant. The ligand-free protocol is simple, clean and free from hazardous chemicals. Moreover, the catalyst is reusable for several times, thus making the methodology sustainably viable.
- Veisi, Hojat,Tamoradi, Taibeh,Karmakar, Bikash
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p. 10343 - 10351
(2019/07/09)
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- Immobilization of Gd(III) complex on Fe3O4: A novel and recyclable catalyst for synthesis of tetrazole and S–S coupling
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In the present work, a novel catalysts prepared by the anchoring of Gd(III) complex with OH groups on the surface of Fe3O4 in which characterized by FT-IR, TGA, XRD, EDX, VSM, and ICP-OES techniques and tested in the synthesis of tetrazoles and S–S coupling. This designed methods indicated several advantages including easily recovered from the reaction mixture by magnetic field, several consecutive cycles without noticeable change in its catalytic activity, the use of green solvent, the use of aspartic acid as green ligand, chemical and physical stability of obtained catalyst, short time reaction and good to excellent isolated yields of all product. Also, up to date, Gd(III) complex don't used for the synthesis of tetrazoles and S–S coupling.
- Nemati, Mohammad,Tamoradi, Taiebeh,Veisi, Hojat
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- Nickel Schiff base complex anchored on Fe3O4@MCM-41 as a novel and reusable magnetic nanocatalyst and its application in the oxidation of sulfides and oxidative coupling of thiols using H2O2
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A novel and reusable nanocatalyst was synthesized by anchoring a nickel Schiff base complex onto Fe3O4@MCM-41 (Fe3O4@MCM-41@Ni-P2C) and characterization was accomplished with Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), powder X-ray diffraction (XRD), vibrating sample magnetometry (VSM), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic absorption spectroscopy (AAS) techniques. This catalytic system was efficiently used for oxidation of sulfides to sulfoxides and oxidative coupling of thiols to corresponding disulfides using H2O2 as green oxidant at room temperature. These reactions were carried out in a green solvent (ethanol) and/or under solvent-free conditions with short reaction time, complete selectivity and very high conversion under mild reaction conditions. More importantly, separation and recycling of this magnetic catalyst can be easily done through a simple and low cost magnetic separation process.
- Nikoorazm, Mohsen,Ghorbani, Farshid,Ghorbani-Choghamarani, Arash,Erfani, Zahra
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p. 552 - 561
(2018/04/26)
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- Ni(II)-Adenine complex coated Fe3O4 nanoparticles as high reusable nanocatalyst for the synthesis of polyhydroquinoline derivatives and oxidation reactions
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In the present study, Fe3O4 nanoparticles were prepared via simple and versatile procedure. Then, a novel and green catalyst was synthesized by the immobilization of Ni on Fe3O4 nanoparticles coated with adenine. The activity of this nanostructure compound was examined for the oxidation of sulfides, oxidative coupling of thiols and synthesis of polyhydroquinolines. The prepared catalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray Diffraction (XRD), thermal gravimetric analysis (TGA), and vibrating sample magnetometer (VSM) measurements. This organometallic catalyst was recovered by the assistance of an external magnetic field from the reaction mixture and reused for seven continuous cycles without noticeable change in its catalytic activity.
- Tamoradi, Taiebeh,Ghadermazi, Mohammad,Ghorbani-Choghamarani, Arash
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- Synthesis and characterization of sulfamic acid supported on Fe3O4 nanoparticles: A green, versatile and magnetically separable acidic catalyst for oxidation reactions and Knoevenagel condensation
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Sulfamic acid immobilized on diethylenetriamine functionalized Fe3O4 nanoparticles (SA-DETA-Fe3O4) was successfully prepared and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM), thermo gravimetric analysis (TGA), X-Ray diffraction (XRD) and scanning electron microscopy (SEM). The sulfamic acid was found as a magnetically separable and highly active catalyst for the oxidative coupling thiols, oxidation of sulfides. Furthermore, the SA-DETA-Fe3O4 showed the high catalytic activity in Knoevenagel condensation of aromatic aldehydes with active methylene compounds (malononitrile and ethyl cynoacetate). The nanosolid catalyst could be easily recovered by a simple magnetic separation and reused for many cycles without deterioration in catalytic activity.
- Shiri, Lotfi,Narimani, Hojatollah,Kazemi, Mosstafa
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- Synthesis and characterization of oxo-vanadium complex anchored onto SBA-15 as a green, novel and reusable nanocatalyst for the oxidation of sulfides and oxidative coupling of thiols
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Abstract: The present work describes the synthesis of a new oxo-vanadium complex immobilized on SBA-15 nanostructure as an efficient catalyst for oxidation of sulfides and oxidative coupling of thiols. Characterization of the resultant AMPD@SBA-15 nanostructure was performed by various physico-chemical techniques such as Fourier transform infrared spectroscopy, transmission and scanning electron microscopies, energy-dispersive X-ray spectroscopy, inductively coupled plasma optical emission spectroscopy, X-ray diffraction, thermal gravimetric analysis, and N2 adsorption and desorption. The results of the developed procedure bring several benefits such as the use of commercially available, ecologically benign, operational simplicity, and cheap and chemically inert reagents. It shows good reaction times, practicability and high efficiency, and is easily recovered from the reaction mixture by simple filtration and reused for several consecutive cycles without noticeable change in its catalytic activity. More importantly, high efficiency, simple and an inexpensive procedure, commercially available materials, easy separation, and an eco-friendly procedure are the several advantages of the currently employed heterogeneous catalytic system.
- Tamoradi, Taiebeh,Ghadermazi, Mohammad,Ghorbani-Choghamarani, Arash,Molaei, Somayeh
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p. 4259 - 4276
(2018/03/21)
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- Highly efficient, green, rapid, and chemoselective oxidation of sulfur-containing compounds in the presence of an MCM-41@creatinine@M (M = la and Pr) mesostructured catalyst under neat conditions
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In the present study, we report the synthesis of two green recoverable catalysts by covalent linking of the creatinine La and Pr complexes on an MCM-41 mesostructure with the commercially available materials and via a simple and inexpensive procedure. These heterogeneous catalysts were characterized by Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, N2 adsorption and desorption, inductively coupled plasma optical emission spectroscopy, and thermogravimetric analysis. The obtained mesostructures act as active and reusable catalysts for the oxidation of sulfides and oxidative coupling of thiols under neat conditions. More importantly, significant practical advantages of this environmentally friendly process include high efficiency, good reaction times, and convenient recovery and reusability for several times without any significant loss of activity of the catalyst.
- Tamoradi, Taiebeh,Ghadermazi, Mohammad,Ghorbani-Choghamarani, Arash
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p. 5479 - 5488
(2018/03/30)
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- Anchoring Ni (II) on Fe3O4@tryptophan: A recyclable, green and extremely efficient magnetic nanocatalyst for one-pot synthesis of 5-substituted 1H-tetrazoles and chemoselective oxidation of sulfides and thiols
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A green, novel and extremely efficient nanocatalyst was successfully synthesized by the immobilization of Ni as a transition metal on Fe3O4 nanoparticles coated with tryptophan. This nanostructured material was characterized using Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, thermogravimetric analysis, inductively coupled plasma optical emission spectroscopy, vibrating sample magnetometry and X-ray diffraction. The prepared nanocatalyst was applied for the oxidation of sulfides, oxidative coupling of thiols and synthesis of 5-substituted 1H-tetrazoles. The use of non-toxic, green and inexpensive materials, easy separation of magnetic nanoparticles from a reaction mixture using a magnetic field, efficient and one-pot synthesis, and high yields of products are the most important advantages of this nanocatalyst.
- Moeini, Nazanin,Tamoradi, Taiebeh,Ghadermazi, Mohammad,Ghorbani-Choghamarani, Arash
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- Cu(II) immobilized on Fe3O4–diethylenetriamine: A new magnetically recoverable catalyst for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones and oxidative coupling of thiols
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Cu(II) immobilized on Fe3O4–diethylenetriamine was designed as a new, inexpensive and efficient heterogeneous catalyst for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones and the oxidative coupling of thiols. The structure of the nanomagnetic catalyst was comprehensively characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, vibrating sample magnetometry, thermogravimetric analysis, X-ray diffraction and atomic absorption spectroscopy. Simple preparation of the catalyst from commercially available materials, high catalytic activity, simple operation, high yields, use of green solvents, easy magnetic separation and reusability of the catalyst with unaltered activity make our protocol a green and feasible synthetic strategy.
- Shiri, Lotfi,Ghorbani-Choghamarani, Arash,Kazemi, Mosstafa
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- Synthesis of Fe3O4@SiO2@DOPisatin-Ni(II) and Cu(II) nanoparticles: Highly efficient catalyst for the synthesis of sulfoxides and disulfides
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The catalytic activity of two magnetic catalysts Fe3O4@SiO2@DOPisatin-M(II) (M?=?Ni, Cu) was investigated in the environmentally green H2O2 oxidant-based oxidation of sulfides to sulfoxides and oxidative coupling of thiols to disulfides. By using these catalysts, various substrates were successfully converted into their corresponding product. These catalysts could also be reused multiple time without significant loss of activity. The physical and chemical properties of the catalysts were determined using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), energy dispersive X-ray spectroscopy (EDX) and atomic absorption spectroscopy (AAS).
- Hajjami, Maryam,Sharifirad, Fatemeh,Gholamian, Fatemeh
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- Synthesis and characterization of tribenzyl ammonium-tribromide supported on magnetic Fe3O4 nanoparticles: a robust magnetically recoverable catalyst for the oxidative coupling of thiols and oxidation of sulfides
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Abstract: Taking into account the principles of green chemistry, magnetic nanoparticles, especially Fe3O4 nanoparticles, open up a new chapter in modern organic synthesis to inset a fascinating, stupendous and efficient catalytic strategy for facilitating catalyst recovery in various chemical reactions. Inspired by this topic, tribenzyl ammonium-tribromide immobilized on magnetic nanoparticles (Fe3O4–TBA-Br3) as a bromine source was successfully synthesized and its catalytic activity in the oxidative coupling of thiols and oxidation of sulfides was investigated. It is the first report on the use of the immobilized bromine source on Fe3O4 nanoparticles as a nanomagnetic recyclable catalyst for the oxidative coupling of thiols. The nanosolid catalyst could be easily recovered by a simple magnetic separation and reused for several cycles without significant degradation in catalytic activity. Graphical Abstract: [Figure not available: see fulltext.]
- Shiri, Lotfi,Ghorbani-Choghamarani, Arash,Kazemi, Mosstafa
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p. 2707 - 2724
(2017/04/18)
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- Fe3O4 MNPs-DETA/Benzyl-Br3: A new magnetically reusable catalyst for the oxidative coupling of thiols
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We report a new strategy to immobilize a bromine source on the surface of magnetic Fe3O4 nanoparticles (Fe3O4 MNPs-DETA/Benzyl-Br3) leading to amagnetically recoverable catalyst, which exhibits high catalytic efficiency in oxidative coupling of thiols to the disulfides (89–98%). The Fe3O4 MNPs-DETA/Benzyl-Br3 catalyst was fabricated by anchoring 3-chloropropyltrimethoxysilane (CPTMS) onmagnetic Fe3O4 nanoparticles, followed with N-benzylation and reaction with bromine in tetrachloridecarbon. The resulting nanocomposite was analyzed by a series of characterization techniques such as FT-IR, SEM, TGA, VSM and XRD. The catalyst could be recovered viamagnetic attraction and could be recycled at least 5 times without appreciable decrease in activity.
- Shiri, Lotfi,Kazemi, Mosstafa
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p. 1171 - 1176
(2017/09/27)
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- Dynamic covalent chemistry in aqueous solution by photoinduced radical disulfide metathesis
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Photoinduced radical disulfide metathesis (PRDM) is a dynamic covalent reaction that requires UV light to induce the homolytic cleavage of the disulfide bond, thus offering the opportunity to construct dynamic covalent systems that are dormant and can be photo-Activated on demand. In this work, we showcase how PRDM can be utilized in aqueous solution and demonstrate its potential by generating a UV responsive hydrogel from an asymmetrical disulfide precursor.
- Klepel, Florian,Ravoo, Bart Jan
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supporting information
p. 3840 - 3842
(2017/07/11)
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- 3,6-Di(pyridin-2-yl)-1,2,4,5-tetrazine (pytz) mediated metal-free mild oxidation of thiols to disulfides in aqueous medium
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Thiols are efficiently oxidized to disulfides (RSSR) in the presence of 3,6-di(pyridin-2-yl)-1,2,4,5-tetrazine (pytz) in aqueous medium, as well as in the absence of a solvent under mild and metal-free conditions. A broad range of alkyl, aryl and heterocyclic symmetrical disulfides can be easily obtained in almost quantitative yields. The X-ray single crystal structure of 2-aminocyclopent-1-ene-1-carbothioic dithioperoxyanhydride (disulfide obtained from 2-aminocyclopentene-1-dithiocarboxylic acid, ACDA) is reported. The reaction mechanism has been studied thoroughly. It is shown that the reaction proceeds through the formation of an organosulphur radical. Pytz interacts with thiol to accept one electron and produces an organosulphur radical. Pytz ultimately accepts two electrons to form H2pytz and is capable of oxidizing 2 equivalents of thiols.
- Samanta, Suvendu,Ray, Shounak,Ghosh, Abhisek Brata,Biswas, Papu
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p. 39356 - 39363
(2016/06/01)
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- Sulfamic acid-functionalized nano-titanium dioxide as an efficient, mild and highly recyclable solid acid nanocatalyst for chemoselective oxidation of sulfides and thiols
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A highly efficient and retrievable titanium dioxide-based nanocatalyst has been synthesized by covalent grafting of chlorosulfonic acid on amine-functionalized titania as a novel inorganic-organic hybrid heterogeneous nanocatalyst, which was characterized by Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The acid strength of the catalyst was determined by pH analysis and the Hammett acidity function. The potential of the resultant nanocatalyst was effectively evaluated for the chemoselective oxidation of sulfides to sulfoxides and thiols to disulfides using 30% H2O2 as an oxidant at room temperature under solvent-free conditions, which led to high conversion rates and yields. Optimization of the reaction conditions was studied by central composite design (CCD), which is one of the most widely used response surface methodologies. The catalyst can be easily recycled up to 10 times without significant decrease in catalytic activity, which makes it a promising catalyst for practical and large-scale applications. This work is the first report that uses 2,4-toluene diisocyanate as a linker for immobilizing liquid acid on a support.
- Tabrizian, Elham,Amoozadeh, Ali,Rahmani, Salman
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p. 21854 - 21864
(2016/03/08)
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- Efficient preparation of boehmite silica dopamine sulfamic acid as a novel nanostructured compound and its application as a catalyst in some organic reactions
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A novel type of recoverable boehmite nanocatalyst was prepared via immobilization of dopamine on the surface of boehmite followed by coating with silica and reacting with chlorosulfunic acid to obtain boehmite silica dopamine sulfamic acid (boehmite-Si-DSA). This compound was characterized by FT-IR spectroscopy, TGA, XRD, TEM and SEM techniques. Boehmite-Si-DSA was used as an efficient, recoverable and thermally stable heterogeneous nanocatalyst for the preparation of 2,3-dihydroquinazolin-4(1H)-one, sulfoxides and disulfides. The catalyst was recovered by simple filtration and reused several times without significant loss of catalytic efficiency.
- Hajjami, Maryam,Ghorbani-Choghamarani, Arash,Ghafouri-Nejad, Raziyeh,Tahmasbi, Bahman
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p. 3066 - 3074
(2016/05/09)
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- Synthesis and characterization of Co (II) and Fe (III) Schiff base complexes grafted onto mesoporous MCM-41: A heterogeneous and recyclable nanocatalysts for the selective oxidation of sulfides and oxidative coupling of thiols
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Novel organic–inorganic hybrid heterogeneous catalysts containing cobalt(II) and iron(III) Schiff base complexes, grafted on the internal surface of MCM-41 pores were prepared by introducing a metal salt into a mesoporous silica functionalized with a Schiff base ligand. The chemical and physical properties of the catalysts were investigated by BET, TGA, XRD, FT-IR, and TEM techniques. These complexes were found to be efficient, selective catalysts for the oxidation of various sulfides to sulfoxides and oxidative coupling of thiols to their corresponding disulfides with urea hydrogen peroxide in excellent yield at room temperature. The designed catalytic system prevents effectively the overoxidation of sulfides and thiols to sulfoxides and sulfones, respectively. Also the heterogeneous catalysts can be recovered easily and reused many times without significant loss of activity and selectivity.
- Noori, Nourolah,Nikoorazm, Mohsen,Ghorbani-Choghamarani, Arash
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p. 1388 - 1395
(2016/09/28)
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- Synthesis, characterization, and catalytic application of Cr and Mn Schiff base complexes immobilized on modified nanoporous MCM-41
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Immobilization of chromium and manganese Schiff base complexes by postgrafting of ligand then metal salts on the walls of mesoporous MCM-41 functionalized with (3-aminopropyl)triethoxysilane is described. Characterization of the resulting heterogeneous catalysts by Fourier-transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, and Brunauer–Emmett–Teller (BET) techniques indicated successful grafting of these two complexes inside the nanochannels of MCM-41. The complexes were found to be efficient, selective catalysts for oxidation of various sulfides to sulfoxides and oxidative coupling of thiols to corresponding disulfides using H2O2 as oxidant at room temperature. The recycling results of these heterogeneous catalysts showed good recyclability without significant loss of activity or selectivity in successive runs, indicating that the Cr and Mn Schiff base complexes supported on nanoporous MCM-41 remained intact and the coordination environments were not altered during the reaction.
- Nikoorazm, Mohsen,Ghorbani-Choghamarani, Arash,Noori, Nourolah
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p. 4621 - 4640
(2016/07/06)
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- Ni-SMTU@boehmite: As an efficient and recyclable nanocatalyst for oxidation reactions
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Boehmite nanoparticles were prepared via a simple and inexpensive procedure in water using commercially available materials, and furthermore a novel type of recoverable nanocatalyst was prepared via immobilization of the S-methylisothiourea complex of nickel on the surface of boehmite nanoparticles (Ni-SMTU@boehmite). This organometallic catalyst was characterized by FT-IR spectroscopy, TGA, XRD, ICP-OES, EDS and SEM techniques. Ni-SMTU@boehmite was applied as an efficient, recoverable and stable heterogeneous organometallic catalyst for the selective oxidation of sulfides to sulfoxides and oxidative coupling of thiols to corresponding disulfides. Metal leaching and heterogeneity test of this catalyst was examined by the ICP-OES technique, which showed that this catalyst can be recovered and reused for several times without significant loss of its catalytic efficiency or nickel leaching.
- Ghorbani-Choghamarani, Arash,Moradi, Parisa,Tahmasbi, Bahman
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p. 56458 - 56466
(2016/07/06)
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- Oxidative dehydrogenation of thiols to disulfides at room temperature using silica supported iron oxide as an efficient solid catalyst
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Selective transformation of thiols to disulfides by means of oxidative dehydrogenation has been described using silica supported iron oxide under base- and solvent-free reaction conditions at room temperature in an open atmosphere. The easiness of catalyst preparation, green reaction conditions, easy separation of the formed products and catalyst from the reaction mixture, and recyclability of the catalyst, are the most attractive facets of our synthetic procedure which, being ecofriendly, will find immense applications in academic and industrial sectors.
- Paul, Susmita,Islam
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p. 95753 - 95759
(2016/10/22)
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- Preparation of DSA@MNPs and application as heterogeneous and recyclable nanocatalyst for oxidation of sulfides and oxidative coupling of thiols
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Abstract: 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. Graphical abstract: [Figure not available: see fulltext.]
- Ghorbani-Choghamarani, Arash,Rabiei, Hossein,Tahmasbi, Bahman,Ghasemi, Banoo,Mardi, Farideh
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p. 5723 - 5737
(2016/06/01)
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- Schiff base complex coated Fe3O4 nanoparticles: A highly reusable nanocatalyst for the selective oxidation of sulfides and oxidative coupling of thiols
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In this work, a new nanomagnetic complex of Cu(II) has been synthesized. The prepared catalyst was characterized by TG/DTG, FT-IR, TEM, VSM, ICP, AAS, XRD, EDS and SEM analyses. It was found to be an efficient catalyst for the oxidation of sulfides and oxidative coupling of thiols. High catalytic activity, ease of recovery from the reaction mixture using an external magnet, and several reuse times without significant losses in performance are additional eco-friendly attributes of this catalytic system.
- Ghorbani-Choghamarani, Arash,Ghasemi, Banoo,Safari, Zohre,Azadi, Gouhar
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- Preparation and characterization of organically modified MCM-48 as heterogonous catalyst for oxidation of sulfides and thiols
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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.
- Hajjami, Maryam,Yousofvand, Zakieh
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p. 1733 - 1740
(2019/11/28)
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- Schiff base complexes of Ni, Co, Cr, Cd and Zn supported on magnetic nanoparticles: As efficient and recyclable catalysts for the oxidation of sulfides and oxidative coupling of thiols
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Abstract Oxidation of sulfides to sulfoxides and oxidative coupling of thiols into their corresponding disulfides were carried out using hydrogen peroxide (H2O2) as oxidizing agent in the presence of immobilized Ni, Co, Cr, Zn or Cd complexes on Fe3O4 magnetic nanoparticles (M-Salen-MNPs) as stable, heterogeneous, efficient and magnetically recoverable nanocatalysts under mild reaction conditions. These supported complexes were characterized by FT-IR spectroscopy, thermogravimetric analysis (TGA), powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). A variety of aromatic and aliphatic sulfides and thiols with different functional groups were successfully oxidized with short reaction times in good to excellent yields. Recovery of the catalyst is easily achieved by magnetic decantation and reused for several consecutive runs without significant loss of its catalytic efficiency.
- Ghorbani-Choghamarani, Arash,Darvishnejad, Zahra,Tahmasbi, Bahman
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p. 223 - 231
(2015/08/03)
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- Nickel Schiff-base complexes immobilized on boehmite nanoparticles and their application in the oxidation of sulfides and oxidative coupling of thiols as novel and reusable nano organometal catalysts
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Boehmite nanoparticles were prepared by very simple and inexpensive procedure in water at room temperature using commercially available materials. Two Schiff-base complexes of nickel have been immobilized on the boehmite nanoparticles. These catalysts were characterized by FT-IR spectroscopy, TGA, XRD, BET, UV-DRS, TEM, SEM, EDS and ICP-OES techniques. These compounds were applied as catalysts for the oxidation of sulfides to sulfoxides and oxidative coupling of thiols to disulfides under mild reaction conditions at room temperature. These catalysts were recovered by simple filtration and reused several times without significant loss of their catalytic efficiency.
- Ghorbani-Choghamarani, Arash,Tahmasbi, Bahman,Arghand, Fatemeh,Faryadi, Sara
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p. 92174 - 92183
(2015/11/17)
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- Oxo-vanadium(IV) Schiff base complex supported on modified MCM-41: A reusable and efficient catalyst for the oxidation of sulfides and oxidative S-S coupling of thiols
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Oxo-vanadium(IV) Schiff base complex supported on MCM-41 as an organic-inorganic hybrid heterogeneous catalyst was synthesized with post-grafting of MCM-41 with 3-aminoropropyltrimethoxysilane and subsequent reaction with 3,4-dihydroxybenzaldehyde and then complexation with oxo-vanadium acetylacetonate salt. The catalyst was analysed using a series of characterization techniques such as Fourier transform infrared spectroscopy, small-angle X-ray diffraction, nitrogen absorption isotherm, transmission electron microscopy and thermogravimetric analysis. The data collected provided evidence that the vanadium complex was anchored onto MCM-41. High catalytic activity of this catalyst was observed in the oxidation of various sulfides and thiols (into sulfoxides and disulfides, respectively) with urea hydrogen peroxide as oxidant in high to excellent yields and selectivity under mild conditions. The heterogeneous catalyst could be recovered easily and reused several times without significant loss in catalytic activity and selectivity.
- Nikoorazm, Mohsen,Ghorbani-Choghamarani, Arash,Noori, Nourolah
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p. 328 - 333
(2015/04/27)
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- Mechanistic insights into the interface-directed transformation of thiols into disulfides and molecular hydrogen by visible-light irradiation of quantum dots
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Quantum dots (QDs) offer new and versatile ways to harvest light energy. However, there are few examples involving the utilization of QDs in organic synthesis. Visible-light irradiation of CdSe QDs was found to result in virtually quantitative coupling of a variety of thiols to give disulfides and H2 without the need for sacrificial reagents or external oxidants. The addition of small amounts of nickel(II) salts dramatically improved the efficiency and conversion through facilitating the formation of hydrogen atoms, thereby leading to faster regeneration of the ground-state QDs. Mechanistic studies reveal that the coupling reaction occurs on the QD surfaces rather than in solution and offer a blueprint for how these QDs may be used in other photocatalytic applications. Because no sacrificial agent or oxidant is necessary and the catalyst is reusable, this method may be useful for the formation of disulfide bonds in proteins as well as in other systems sensitive to the presence of oxidants. Copyright
- Li, Xu-Bing,Li, Zhi-Jun,Gao, Yu-Ji,Meng, Qing-Yuan,Yu, Shan,Weiss, Richard G.,Tung, Chen-Ho,Wu, Li-Zhu
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supporting information
p. 2085 - 2089
(2014/03/21)
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- Cu(II)-Schiff base complex-functionalized magnetic Fe3O4 nanoparticles: A heterogeneous catalyst for various oxidation reactions
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Cu(II)-Schiff base complex-functionalized magnetic Fe3O4 nanoparticles were prepared and characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy techniques. This compound acts as a highly active and selective catalyst for the oxidation of sulfides and thiols. These reactions can be carried out in ethanol or solvent-free conditions in the presence of hydrogen peroxide with complete selectivity and very high conversion under mild reaction conditions. The designed catalytic system prevents effectively the over-oxidation of sulfides to sulfones. Separation and recycling can also be easily done using a simple magnetic separation process.
- Ghorbani-Choghamarani, Arash,Darvishnejad, Zahra,Norouzi, Masoomeh
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p. 170 - 175
(2015/03/30)
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- Practical and versatile oxidation of sulfides into sulfoxides and oxidative coupling of thiols using polyvinylpolypyrrolidonium tribromide
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A simple and highly selective oxidation of sulfides to sulfoxides and an oxidative coupling of thiols with polyvinylpolypyrrolidoniume tribromide has been developed. A series of sulfides and thiols was oxidized selectively at room temperature in good to excellent yields.
- Ghorbani-Choghamarani, Arash,Azadi, Gouhar,Tahmasbi, Bahman,Hadizadeh-Hafshejani, Mojtaba,Abdi, Zainab
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p. 433 - 439
(2014/04/03)
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- Synthesis of hierarchical mesoporous Mn-MFi zeolite nanoparticles: A unique architecture of heterogeneous catalyst for the aerobic oxidation of thiols to disulfides
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An efficient procedure for aerobic oxidation of thiols to disulfides catalyzed by new self-assembled hierarchical mesoporous Mn-MFI in the presence of air under solvent-free conditions as well as in aqueous medium is reported. The mesoporosity and Mn4+ loading, together with a highly crystalline microporous pore wall structure of the MFI framework were achieved through a newly designed hydrothermal process. This hydrothermal approach leads to hierarchical self-assembled mesoporous zeolite structures through isomorphous substitution of Si by Mn and Al. It is shown that Mn-containing mesoporous zeolites are capable to form disulfide bonds from thiols in the presence of air. The zeolitic materials were characterized by XRD, field-emission scanning electron microscopy, high-resolution TEM, X-ray photoelectron spectroscopy, 29Si NMR, 27Al NMR, and EPR spectroscopy, as well as AAS analysis and N2 sorption studies. N2 sorption analysis revealed high surface areas and narrow pore size distributions (1.2-6.0 nm) for different samples. The mesoporous Mn-ZSM-5 acted as an efficient heterogeneous catalyst with maximum catalytic activity in the benzenethiol conversion to diphenyldithiol. Copyright
- Patra, Astam K.,Dutta, Arghya,Pramanik, Malay,Nandi, Mahasweta,Uyama, Hiroshi,Bhaumik, Asim
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p. 220 - 229
(2014/01/23)
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- In situ generated hypoiodous acid in an efficient and heterogeneous catalytic system for the homo-oxidative coupling of thiols
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Supported hydrogen peroxide on polyvinylpolypyrrolidone (PVPP- -H 2O2), silica sulfuric acid (SiO2-OSO 3H) and catalytic amounts of potassium iodide (KI) was developed as a heterogeneous medium for the rapid oxidative coupling of thiols into symmetrical homodisulfides. This oxidizing system proceeds under extremely mild conditions and gives no other oxidized side products.
- Ghorbani-Choghamarani, Arash,Nikoorazm, Mohsen,Azadi, Gouhar
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p. 173 - 178
(2013/08/25)
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- Selective oxidation of thiols and alcohols by physically encapsulated nickel schiff-base complex prepared via sol-gel method as nano-catalyst
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A heterogeneous catalyst was prepared by direct physical encapsulation of nickel Schiff-base complex into the silicon dioxide matrix via sol-gel method. The compounds were characterized by FT-IR, SEM, TEM, XRD, CHNS, and AAS. The catalytic performance in the alcohols and thiols oxidation was investigated in the presence of H2O2 (10 mmol, 30%) as oxidant. After five recycle runs, the catalyst showed 13% reduction in activity with slightly Ni(II)-complex leached to the solvent. Varieties of primary and secondary alcohols were efficiently oxidized to the corresponding ketones. Thiols were oxidized in coupling reaction to disulfides in excellent yields using nano-catalyst with H2O2.
- Eshtiagh-Hosseini, Hossein,Tabari, Taymaz,Takjoo, Reza,Eshghi, Hossein
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p. 264 - 272
(2013/04/10)
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- Rapid and convenient method for the synthesis of symmetrical disulfides
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We present here the results on the use of 1,3,5-triazo-2,4,6- triphosphorine-2,2,4,4,6,6-hexachloride as an efficient promoter in the conversion of thiols to the corresponding symmetrical disulfides under solvent-free conditions. Aromatic thiols bearing electron donating and electron withdrawing groups, heteroaromatic, and alkyl thiols reacted efficiently to afford excellent yields of disulfides in short reaction times after easy work-up. Different functional groups including carboxyl, methoxy, methylthio, and halogen are tolerated. Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental files: Additional figures and tables.
- Bahrami, Kiumars,Khodaei, Mohammad M.,Shakibaian, Vida,Targhan, Homa
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p. 981 - 988
(2013/09/02)
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- A simple and practical method for the oxidation of thiols to disulfides at mild conditions without solvents
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A green, straightforward, and novel method for the oxidation of thiols to the corresponding disulfides is reported using hydrogen peroxide catalyzed by tetrabutylammonium iodide (TBAI) without solvents at room temperature. The corresponding disulfides were obtained with excellent yields and short reaction times. Copyright
- He, Ying,Hang, Dongliang,Lu, Ming
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experimental part
p. 1118 - 1124
(2012/08/14)
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- Microwave assisted oxidative coupling of thiols to symmetrical disulfides with tripropylammonium fluorochromate(VI) (TPAFC)
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Tripropylammonium fluorochromate(VI) (TPAFC) is an efficient and novel reagent, which can be prepared easily and oxidizes thiols to the corresponding disulfides, quickly. The reactions are performed cleanly and are controlled to stop at the disulfide stage, without over-oxidation or side products. Coupling of thiols to their corresponding disulfides, was studied in solution at room temperature and under conditions using a minimal amount of solvent under microwave irradiation. The easy procedure, simple work-up, short reaction times, and excellent yields are other advantages of this reagent.
- Mohammadi, Mohammad Kazem,Ghammamy, Shahriare
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experimental part
p. 139 - 144
(2012/04/23)
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- Trimethylphenylammonium tribromide as a new and efficient oxidizing agent for the oxidative coupling of thiols into disulfides and chemoselective oxidation of sulfides into sulfoxides
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Trimethylphenylammonium tribromide has been introduced as a versatile and new oxidizing agent for the preparation of disulfides and sulfoxides from thiols and sulfides, respectively. The reaction progress is simple, and proceeds under mild and homogenous conditions in ambient temperature. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. Copyright Taylor &Francis Group, LLC.
- Ghorbani-Choghamarani, Arash,Soleiman-Beigi, Mohammad,Noormohammadi, Farid
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scheme or table
p. 1665 - 1672
(2011/10/05)
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- Green preparation of disulfides from corresponding thiols by poly(4-vinylpyridinium nitrate) as recoverable and new polymeric reagent
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Poly(4-vinylpyridinium nitrate) was found to be a recyclable and highly efficient oxidizing polymer for the oxidative coupling of a variety of aliphatic or aromatic thiols to the corresponding disulfides. Poly(4-vinylpyridinium nitrate) is an extremely mild agent, which gave no other oxidized side products.
- Ghorbani-Choghamarani, Arash,Sardari, Sara
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experimental part
p. 63 - 69
(2011/12/05)
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- Metal-free oxidative coupling of thiols to disulfides using guanidinium nitrate or nitro urea in the presence of silica sulfuric acid
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Efficient combination of nitro urea or guanidinium nitrate and silica sulfuric acid (SiO2OSO3H) as a new oxidizing system is able to oxidize a variety of aliphatic or aromatic thiols to the corresponding disulfides. The process reported here is operationally simple, environmentally benign and reactions have been mildly and heterogeneously performed in dichloromethane at room temperature. Indian Academy of Sciences.
- Ghorbani-Choghamarani, Arash,Nikoorazm, Mohsen,Goudarziafshar, Hamid,Shokr, Alireza,Almasi, Hosein
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experimental part
p. 453 - 457
(2012/03/26)
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- Tributylammonium halochromates/silica gel: Simple reagents for oxidative coupling of thiols to symmetrical disulfides
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New orange solid tributylammonium halochromates, (C4H 9)3N+CrO3X-, TBAXC (X=F, Cl) are easily synthesized by the reaction of tributylammonium fluoride and chloride with CrO3 in a 1:1 molar ratio in the presence of HF and HCl. Tributylammonium halochromates(VI) are versatile reagent for the effective and selective oxidation of organic substrates. Silica gel supported TBAFC and TBACC are versatile reagents for the effective and selective oxidation of organic substrates, in particular, thiols, under mild conditions. Considerable improvements are observed in the presence of the absorbent, making the work-up much more convenient. New orange solid tributylammonium halochromates, (C 4H9)3N+CrO3X -, TBAXC (X=F, Cl) are easily synthesized by the reaction of tributylammonium fluoride and chloride with CrO3 in a 1:1 molar ratio in the presence of HF and HCl. Tributylammonium halochromates(VI) are versatile reagent for the effective and selective oxidation of organic substrates. Copyright
- Mohammadi, Mohammad Kazem,Ghammamy, Shahriare,Zarrinabadi, Soroush,Farjam, Mohammad Hossein,Sabayan, Behrang
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experimental part
p. 2199 - 2203
(2011/10/09)
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- Reduction mechanism of a coordinated superoxide by thiols in acidic media
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In weakly acidic media ([H+], 0.01-0.06 M), 2-mercaptoethanol (mercap, RSH), thioglycolic acid (tga, R′SH) and l-cysteine (cys, R′′SH) reduce the superoxo ligand of the complex ion, {μ-amido-μ-superoxo-bis[tetraamminecobalt(iii)]}4+ (1) to its corresponding hydroperoxo complex, {μ-amido-μ-hydroperoxo- bis[tetraamminecobalt(iii)]}3+ (2). During this act, RSH and R′SH are quantitatively oxidized to their respective disulfides. However, cysteine (R′′SH) is converted to a mixture of ～80% of the disulfide, cystine and ～20% to cystine sulfinic acid. Cystine itself is not a source of the sulfinic acid. Dissolved copper, even at the impurity level, dramatically catalyzes the reaction such that the direct reactions are inaccessible. Nevertheless, the catalyzed path can be masked completely with 0.20 mM dipicolinic acid and it can be determined for the first time that, the direct reactions are first-order in [1], in [total thiol] and in basicity. Rate decreases linearly with increasing mol% of D2O in the solvent. H-atom (H+ + e) transfer from thiols to superoxide in 1 seems logical for the conversion of 1 to 2. The Royal Society of Chemistry 2010.
- Mishra, Ritu,Mukhopadhyay, Subrata,Banerjee, Rupendranath
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supporting information; experimental part
p. 2692 - 2696
(2010/06/14)
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