Green oxidation of 2-imidazolines with tert-butyl hydroperoxide catalyzed by supported manganese(III) porphyrin in water

Green oxidation of 2-substituted imidazolines with tert-butyl hydroperoxide catalyzed by tetraphenylporphyrinatomanganese(III) chloride, [Mn(TPP)Cl], supported on polystyrene and silica bound imidazole is reported. A variety of 2-imidazolines were efficiently converted to their corresponding imidazoles by these catalytic systems in H₂O. Ultrasonic (US) irradiation enhanced the catalytic activity of these catalysts and higher product yields were observed at shorter reaction times. These catalysts were re-used several times without significant loss of their catalytic activities. The effect of reaction parameters such as catalyst amount, reaction temperature, and the effect of US irradiation on the catalytic activity was also investigated.     

Biomimetic epoxidation of alkenes with sodium periodate catalyzed by tetraphenylporphyrinatomanganese(III) chloride supported on multiwall carbon nanotubes

The biomimetic epoxidation of alkenes catalyzed by tetraphenylporphyrinatomanganese(III) chloride, [Mn(TPP)Cl], immobilized on multiwall carbon nanotubes modified with 4-aminopyridine and 4-aminophenol is reported. These heterogenized catalysts were used as efficient and reusable catalysts for epoxidation of a variety of cyclic and linear alkenes with sodium periodate under mild conditions. The catalysts, [Mn(TPP)Cl@amine-MWCNT], were characterized by physico-chemical and spectroscopic methods. The effect of ultrasonic irradiation on these catalytic systems was also investigated. The catalysts were reused several times without loss of their activity.     

Manganese(III) porphyrin supported onto multi-walled carbon nanotubes for heterogeneous oxidation of synthetic textile dyes and 2,6-dimethylphenol by tert-butyl hydroperoxide

Manganese porphyrin has been supported onto multi-walled carbon nanotubes (Mn(TCPP)OAc@MWCNT) and characterized by powder X-ray diffraction, FT-IR, atomic absorption and UV–vis spectroscopy, field emission scanning electron microscopy (FE-SEM) and also thermogravimetric analysis (TGA). The TGA curve shows that the nanocatalyst was thermally stable up to almost 350 °C. This catalyst was found to be able to oxidize different synthetic textile dyes in aqueous media over a wide pH range at ambient temperature with tert-butyl hydroperoxide (TBHP) as the oxygen source. The influence of some important parameters such as the initial pH of the dye solution, temperature and concentration of the catalyst, the oxidant and the co-catalyst were investigated. Also, the ability of this heterogeneous catalyst to oxidize 2,6-dimethylphenol (with excellent selectivity for quinone (86%)) with TBHP in acetonitrile was evaluated. The separation and recycling of the catalyst is simple and the catalyst can be used several successive cycles without significant decrease in catalytic activity.     

Efficient solvent-free iron (III) catalyzed oxidation of alcohols by hydrogen peroxide

Selective oxidation of secondary and benzylic alcohols was efficiently accomplished by H₂O₂ under solvent-free condition catalyzed by FeBr₃. Secondary alcohols are selectively oxidized even in the presence of primary ones. This method is high yielding, safe and operationally simple.     

Efficient and green oxidation of alcohols with tert-butyl hydrogenperoxide catalyzed by a recyclable magnetic core-shell nanoparticle-supported oxo-vanadium ephedrine complex

A novel method for the oxidation of alcohols to the corresponding carbonyl compounds has been successfully developed using tert-butyl hydrogenperoxide (TBHP) in the presence of a catalytic amount of recyclable magnetic nanoparticle-supported oxo-vanadium ephedrine complex (VO(ephedrine)₂@MNPs) in PEG as a green solvent at 80 °C. The catalyst can be magnetically recycled and successfully reused in six subsequent reaction cycles with only slight decreases of its catalytic activity.     

Cu-Co-Fe oxide catalysts supported on carbon nanotubes for the oxidation of CO

The catalytic activity and adsorption characteristics of the surface of catalysts in the form of carbon nanotubes produced on nickel and cobalt oxides with the Cu-Co-Fe oxide system as supported active phase were studied. At carbon nanotubes produced on nickel oxide with (10 + 10) wt.% of the catalytically active phase total conversion of CO to CO₂ is realized at 47 °C. This sample has high specific surface area and a large volume of mesopores. It was shown that the increase in catalytic activity correlates with the increase in the amount of the α₂ form of CO₂. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 4, pp. 222–226, July–August, 2006.     

Epoxidation of olefin with alkyl hydroperoxide catalyzed by molybdenum complex supported on activated carbon

The catalytic activities of unsupported molybdenum compounds and those supported on activated carbon were compared for the epoxidation of cyclohexene with t-butyl hydroperoxide. Two types of molybdenum compounds were obtained by oxidizing molybdenum powder with hydrogen peroxide. The epoxide was produced without byproducts for both supported and unsupported molybdenum compounds. The reaction was expressed by second order kinetics. By supporting the molybdenum compound on activated carbon, the reactivity was increased ~ six-fold.     

Efficient and selective hydrocarbon oxidation with sodium periodate catalyzed by supported manganese(III) porphyrin

Manganese(III) tetrakis(p-sulfonatophenyl)porphyrin was successfully bound to silica modified with zirconium. The heterogeneous catalyst, MnTPPS-silica, was characterized by SEM, FT-IR and diffuse reflectance UV-Vis spectroscopic techniques. MnTPPS-silica catalyzes alkene epoxidation and alkanes hydroxylation with sodium periodate under agitation with magnetic stirring and ultrasonic irradiation in the presence of imidazole as an axial ligand. This catalytic system shows a good activity in the epoxidation of linear alkenes. Alkyl aromatic and cycloalkanes were efficiently oxidized to their corresponding alcohols and ketones in the presence of this catalyst. This new heterogeneous catalyst is of high stability and reusability in the oxidation reactions and can be reused several times without loss of its activity.     

Solvent-free oxidation of alcohols by t-butyl hydroperoxide catalyzed by water-soluble copper complex

The catalytic system composed of CuCl₂ and 2,2′-biquinoline-4,4′-dicarboxylic acid dipotassium salt (BQC), was found to be highly efficient for the selective oxidation of secondary benzylic, allylic and propargylic alcohols to the corresponding ketones, with aqueous t-butyl hydroperoxide under phase-transfer catalysis conditions. The catalytic system is stable and can be recycled and reused several times without loss of activity.     

埃洛石表面修饰并负载salen钼高效催化烯烃环氧化反应

采用温和的化学表面改性和自组装方法成功制备了埃洛石纳米管负载salen钼(HNTs-SL-Mo)催化剂,运用透射电镜、X射线衍射、红外光谱、诱导偶合等离子体谱和X射线光电子能谱表征了催化剂的形态、大小和分散性等性质。结果证明了salen结构的存在和埃洛石配位钼催化剂的成功制备。制备的催化剂在各种烯烃的环氧化反应中均有很好的活性,且活性高于均相催化剂。对比实验表明,在固定MoO(O2)2(DMF)2时, salen结构发挥了重要作用,不能用N原子作为单一配体来代替。本文还推测了钼和salen配体可能的连接方式和该催化剂催化烯烃环氧化反应的机理。该催化剂在重复使用8次后其活性未见明显下降,表现出优异的重复使用性能。由于埃洛石是一种廉价易得的材料,因此它可为设计效果独特的催化剂提供一个选择。     

埃洛石表面修饰并负载salen钼高效催化烯烃环氧化反应

采用温和的化学表面改性和自组装方法成功制备了埃洛石纳米管负载salen钼(HNTs-SL-Mo)催化剂,运用透射电镜、X射线衍射、红外光谱、诱导偶合等离子体谱和X射线光电子能谱表征了催化剂的形态、大小和分散性等性质。结果证明了salen结构的存在和埃洛石配位钼催化剂的成功制备。制备的催化剂在各种烯烃的环氧化反应中均有很好的活性,且活性高于均相催化剂。对比实验表明,在固定MoO(O2)2(DMF)2时, salen结构发挥了重要作用,不能用N原子作为单一配体来代替。本文还推测了钼和salen配体可能的连接方式和该催化剂催化烯烃环氧化反应的机理。该催化剂在重复使用8次后其活性未见明显下降,表现出优异的重复使用性能。由于埃洛石是一种廉价易得的材料,因此它可为设计效果独特的催化剂提供一个选择。     

Co(salen) catalyzed oxidation of oximes with t-butyl hydroperoxide

Co(salen) catalyzed the oxidation of oximes with t-butyl hydroperoxide to give the parent carbonyl compounds, providing a new convenient route to deoximation reaction. A plausible mechanism involves a substrate radical intermediate.

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Co() -, . . .

     

A polymer-supported diacetatobis(2-quinolylbenzimidazole)copper(II) complex as an efficient catalyst for oxidation of alcohols with tert-butyl hydroperoxide

A polymer-supported diacetatobis(2-quinolylbenzimidazole)copper(II) complex [PS–(QBIM)₂Cu(II)] was synthesized by functionalization of chloromethylated polystyrene cross-linked with 6.5 % divinyl benzene with 2-(2′-quinolyl)benzimidazole and subsequent treatment with Cu(OAc)₂ in methanol. The complex was characterized by physical, analytical and spectroscopic techniques. Electronic and ESR spectra, together with magnetic susceptibility measurements, indicated that the complex was paramagnetic with distorted octahedral geometry around the copper. The complex was found to be active toward oxidation of various alcohols including phenol, benzyl alcohol and cyclohexanol using 70 % aqueous tert-butyl hydroperoxide under mild conditions. Under the optimized reaction conditions, cyclohexanol gave 100 % conversion to cyclohexanone, benzyl alcohol gave 98 % yield of benzaldehyde and phenol gave 89 % yield of catechol and 4 % of hydroquinone. The complex was recycled five times without much loss in catalytic activity.     

Epoxidation of cyclohexene with tert-butyl hydroperoxide catalyzed by polymer anchored molybdenum complexes

Catalytic activity of molybdenum hexacarbonyl anchored on various polymers was investigated for the epoxidation of cyclohexene with tert-butyl hydroperoxide. The activity was increased by anchoring on the polymer. The catalyst on polystyrene showed much higher activity than Mo(CO)₆ used under homogeneous conditions.

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, , .— . . ]qt, Mo(CO)₆, .

     

Oxidation of alcohols with sodium periodate catalyzed by supported Mn(III) porphyrins

The mild and efficient oxidation of alcohols with sodium periodate catalyzed by manganese(III) tetrakis(p-sulfonatophenylporphyrinato) acetate, [Mn(TPPS)], supported on polyvinylpyridine, [Mn(TPPS)-PVP], and Amberlite IRA-400, [Mn (TPPS)-Ad IRA-400], at room temperature is reported. The catalysts used in this study showed high activity not only in the oxidation of benzylic and linear alcohols but also in the oxidation of secondary alcohols at room temperature. These catalysts can be reused several times without significant loss of their activity.     

Selective catalytic oxidation of organosulfur compounds with tert-butyl hydroperoxide

Rates and selectivities for the oxidation of various organosulfur compounds with tert-butyl hydroperoxide were measured on CoAPO-5 (APO = aluminophosphate; Co/P = 0.05), Co/H-Y (Co/Al = 0.15), and MoO(x)/Al2O3 (15 % wt MoO3). Rates increased with increasing electron density at the sulfur atom (methyl phenyl sulfide>diphenyl sulfide>4-methyldibenzothiophene>2,5-dimethyl thiophene). Rates (per metal atom) were significantly higher on CoAPO-5 than on Co/H-Y, MoO(x)/Al2O3, or homogeneous Co acetate catalysts. Small amounts of sulfoxides (1-oxide) were detected on all catalysts at low reactant conversions, together with their corresponding sulfones; at higher conversions, only sulfones (1,1-dioxide) were detected, indicating that the oxidation of sulfoxides is much faster than for organosulfur reactants in the sequential oxidation pathways prevalent on these catalysts. Framework Co cations were not leached from CoAPO-5 during the oxidation of 4-methyldibenzothiophene, but most exchanged Co cations in H-Y and >20 % of Mo cations in MoO(x)/Al2O3 were extracted during these reactions. The fraction of redox-active Co cations in CoAPO-5 and Co/H-Y was measured by reduction-oxidation cycles using H2 and O2 and by UV-visible spectroscopy. This fraction was much larger in CoAPO-5 (0.35) than in Co/H-Y (0.01), consistent with the higher oxidation rates measured on CoAPO-5 and with the involvement of redox-active species in kinetically-relevant steps in catalytic oxidation sequences. Redox-active Co cations at framework positions within accessible channels are required for catalytic activity and structural stability during oxidative desulfurization, whether hydroperoxides are used as reactants or as intermediates (when O2 is used as the oxidant).