Oxidation of 2-imidazolines to 2-imidazoles with sodium periodate catalyzed by polystyrene-bound manganese(III) porphyrin

In the present work, the dehydrogenation of 2-substituted imidazolines with sodium periodate in the presence of tetraphenylporphyrinatomanganese(III) chloride supported on polystyrene-bound imidazole, [Mn(TPP)Cl@PSI] is reported. A wide variety of 2-imidazolines were efficiently converted to their corresponding imidazoles by the [Mn(TPP)Cl@PSI]/NaIO₄ catalytic system in a 1:2 CH₃CN/H₂O mixture under agitation with magnetic stirring. Ultrasonic irradiation enhanced the catalytic activity of this catalyst in the oxidation of 2-imidazolines and this led to shorter reaction times and higher product yields. This catalyst could be reused several times without significant loss of its catalytic activity.     

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.     

负载型金基催化剂Au/Fe(OH)3催化苯乙烯环氧化反应

用共沉淀法制备了Au/Fe(OH)3催化剂, 以叔丁基过氧化氢为氧化剂, 考察焙烧温度和金担载量等对苯乙烯环氧化反应的影响. 结果表明, 催化剂的焙烧温度、金担载量对苯乙烯环氧化反应有较大影响. 在室温下直接合成的质量分数为4.67%的Au/Fe(OH)3催化剂对苯乙烯环氧化反应显示了很好的催化活性, 于80 ℃反应3 h苯乙烯的转化率达到84.1%, 环氧苯乙烷的选择性达到71.5%. 通过X射线粉末衍射(XRD)、X射线光电子能谱(XPS)和Mössbauer分析, 发现催化剂的催化活性与金的价态及铁的化学存在状态有很大关系. 离子态Au3+与载体Fe(OH)3的协同作用对苯乙烯环氧化反应显示出很好的催化活性.     

Epoxidation of styrene catalyzed by manganese (III) porphyrins supported on chloromethylated polystyrene resin bearing crown ether groups,

Metalloporphyrins and crown ether groups were simultaneously supported on chloromethylated polystyrene resin to produce a series of polymer-supported catalysts. The synthesis of these catalysts has been studied. The influence of pH, concentrations of NaOCl and phase transfer catalysts on the epoxidation of styrene catalyzed by these catalysts has also been investigated. The experimental results show that manganese(III) porphyrin bound to chloromethylated polystyrene which bears crown ether groups is effective catalysts for the epoxidation of styrene by sodium hypochlorite. The introduction of crown ether groups increases the catalytic efficiency of supported metalloporphyrins. The kinetics of epoxidation catalyzed by supported manganese(III) porphyrins obeys Michaelis-Menten equation—the characteristic of enzyme-driven reaction.     

Silica supported Ru(salophen)Cl: An efficient and robust heterogeneous catalyst for epoxidation of alkenes with sodium periodate

In the present work, heterogenization of Ru(salophen)Cl via its axial ligation to silica-bound imidazole, SiIm, is reported. The heterogeneous catalyst, [Ru(salophen)Cl–SiIm], was characterized by elemental analysis, SEM, TEM, FT-IR and diffuse reflectance UV–Vis spectroscopic techniques. The catalyst, which is not soluble in water and common organic solvents, was used for efficient epoxidation of cyclic and linear alkenes with NaIO₄ under agitation with magnetic stirring. This new heterogenized catalyst is of high stability and reusability in the oxidation reactions. The effect of reaction parameters such as solvent and oxidant in the epoxidation of cis-cyclooctene were also investigated.     

单核Mn(III)-Shiff碱配合物的晶体结构与性质

报导了两个Schiff碱配体的单核Mn（Ⅲ）配合物（[Mn（Ⅲ）（L1）（H2O）］4CIO。·ZH。O（1）和［Mn（ffi）（LZ）厂Ic。·ZH。O（2》的合成、晶体结构及性反X一衍射晶体结构分析证实：配合物1的晶体属于正交晶系，Pna21空间群．其晶胞参数为α＝10．932（7）A，b＝22．393（5）A，c＝8．960（3）A，V=2193（1）A3，Z＝4．2的晶体属于正交晶系，P212121空间群，α＝17．345（3）A，b＝17．905（2）A，c=7．789（1）A，V＝2418．9（6）A3，Z=4．电化学研究结果显示：配合2是稳定的电化学产物，而1在电场作用下容易歧化．由此说明配位环境是影响化合物稳定性的重要因素．     

Epoxidation reactions with urea–hydrogen peroxide catalyzed by methyltrioxorhenium(VII) on niobia

Soybean oils (oleic, linoleic, and linolenic acids and their methyl esters) are epoxidized readily with urea–hydrogen peroxide (UHP) when methyltrioxorhenium(VII) supported on niobia is used as the catalyst in chloroform. Simple alkenes are epoxidized by the same method. The epoxide and not a diol is produced.     

Homogeneous and heterogeneous olefin epoxidation catalyzed by a binuclear Mn(II)Mn(III) complex

The synthesis and characterization of a binuclear carboxylated bridged manganese complex containing the heptadentate ligand N,N′-bis(2-hydroxybenzyl)-N,N′-bis(2-methylpyridyl)-2-ol-1,3-propanediamine (H₃bbppnol) is reported. This complex was characterized by elemental analysis; infrared, electronic (UV–vis) and EPR spectroscopy; and conductivity measurements. The complex was immobilized on silica by either adsorption or entrapment via a sol–gel route. The obtained solids were characterized by thermogravimetric analyses (TG and DSC), UV–vis and infrared spectroscopy, and X-ray diffraction. The catalytic performance of the binuclear manganese complex in epoxidation reactions was evaluated for both homogeneous and heterogeneous systems. The catalytic investigation revealed that the complex performs well as an epoxidation catalyst for the substrates cyclohexene (26–39%) and cyclooctene (29–74%). The solids containing the immobilized complex can be recovered from the reaction medium and reused, maintaining good catalytic activity.     

Diphenylmethane Oxidation Catalyzed by Mononuclear Mn(III) Complexes

Catalytic property of a series of manganese(III) complexes with tetradentate phenol‐ and pyridinebased ligands on the oxidation of the C‐H bond of diphenylmethane in the presence of hydrogen peroxide as an oxidant at ambient conditions were investigated. In this process, diphenylmethane was oxidized to the corresponding keton and alcohol. The catalytic selectivity of the complexes was evaluated.     

Revisiting Alkane Hydroxylation with m-CPBA (m-Chloroperbenzoic Acid) Catalyzed by Nickel(II) Complexes

Mechanistic studies are performed on the alkane hydroxylation with m-CPBA (m-chloroperbenzoic acid) catalyzed by nickel(II) complexes, Ni^II(L). In the oxidation of cycloalkanes, Ni^II(TPA) acts as an efficient catalyst with a high yield and a high alcohol selectivity. In the oxidation of adamantane, the tertiary carbon is predominantly oxidized. The reaction rate shows first-order dependence on [substrate] and [Ni^II(L)] but is independent on [m-CPBA]; v_obs=k₂[substrate][Ni^II(L)]. The reaction exhibited a relatively large kinetic deuterium isotope effect (KIE) of 6.7, demonstrating that the hydrogen atom abstraction is involved in the rate-limiting step of the catalytic cycle. Furthermore, Ni^II(L) supported by related tetradentate ligands exhibit apparently different catalytic activity, suggesting contribution of the Ni^II(L) in the catalytic cycle. Based on the kinetic analysis and the significant effects of O₂ and CCl₄ on the product distribution pattern, possible contributions of (L)Ni^II−O^. and the aroyloxyl radical as the reactive oxidants are discussed.     

Kinetic method for the determination of traces of thyroxine by its catalytic effect on the Mn(III) metaphosphate-As(III) reaction

A new, highly sensitive and simple kinetic method for the determination of thyroxine was proposed. The method was based on the catalytic effect of thyroxine on the oxidation of As(III) by Mn(III) metaphosphate. The kinetics of the reaction was studied in the presence of orthophosphoric acid. The reaction rate was followed spectrophotometrically at 516 nm. It was established that orthophosphoric acid increased the reaction rate and that the extent of the non-catalytic reaction was extremely small. A kinetic equation was postulated and the apparent rate constant was calculated. The dependence of the reaction rate on temperature was investigated and the energy of activation and other kinetic parameters were determined.

Thyroxine was determined under the optimal experimental conditions in the range 7.0 × 10⁻⁹ to 3.0 × 10⁻⁸ mol L⁻¹ with a relative standard deviation up to 6.7% and a detection limit of 2.7 × 10⁻⁹ mol L⁻¹. In the presence of 0.08 mol L⁻¹ chloride, the detection limit decreased to 6.6 × 10⁻¹⁰ mol L⁻¹. The proposed method was applied for the determination of thyroxine in tablets. The accuracy of the method was evaluated by comparison with the HPLC method.     

龙脑基β-二酮铁配合物催化的苯乙烯类化合物的不对称环氧化反应

合成了四个龙脑基β-二酮Fe(III)络合物, 并用它来催化苯乙烯类化合物在氧气和2-乙基丁醛作用下的不对称环氧化反应. 在25～30 ℃下, 反应获得较高的化学产率, 得到的手性环氧化合物的ee范围为47.5%～91.6%. 考察了催化剂结构、底物结构、反应温度等因素对反应的化学产率和光学收率的影响.     

Mild and Efficient Synthesis of Benzoxazoles, Benzothiazoles, Benzimidazoles, and Oxazolo[4,5-b]pyridines Catalyzed by Bi(III) Salts Under Solvent-Free Conditions

Summary. A series of benzoxazoles, benzothiazoles, benzimidazoles, and oxazolo[4,5-b]pyridines was efficiently synthesized from the reactions of o-aminophenols, o-aminothiophenol, o-phenylenediamines, and 2-amino-3-hydroxypyridine with orthoesters in the presence of catalytic amounts of Bi(III) salts, such as Bi(TFA)₃, Bi(OTf)₃, and BiOClO₄ · xH₂O under solvent-free conditions. The remarkable features of this new protocol are high conversion, very short reaction times, cleaner reaction profiles under solvent-free conditions, straightforward procedure, and use of relatively non-toxic catalysts.     

Biomimetic Decarboxylation of Carboxylic Acids with PhI（OAc）2 Catalyzed by Manganese Porphyrin [Mn（TPP）OAc]

Manganese（Ⅲ） meso-tetraphenylporphyrin acetate [Mn（TPP）OAc] served as an effective catalyst for the oxidative decarboxylation of carboxylic acids with （diacetoxyiodo）benzene [PhI（OAc）2] in CH2CI2-H2O（95：5, volume ratio）. The aryl substituted acetic acids are more reactive than the less electron rich linear carboxylic acids in the presence of catalyst Mn（TPP）OAc. In the former case, the formation of carbonyl products was complete within just a few minutes with 〉97% selectivities, and no further oxidation of the produced aldehydes was achieved under these catalytic conditions. This method provides a benign procedure owing to the utilization of low toxic（diacetoxyiodo） benzene, biologically relevant manganese porphyrins, and carboxylic acids.     

Kinetics and Mechanism of Oxidation of Chromium(III)‐guanosine 5‐Monophosphate Complex by Periodate

The kinetics of oxidation of the chromium(III)‐guanosine 5‐monophosphate complex, [Cr^III(L)(H₂O)₄]³⁺(L = guanosine 5‐monophosphate) by periodate in aqueous solution to Cr^VI have been studied spectrophotometrically over the 25–45 °C range. The reaction is first order with respect to both [IO₄^?] and [Cr^III], and increases with pH over the 2.38–3.68 range. Thermodynamic activation parameters have been calculated. It is proposed that electron transfer proceeds through an inner‐sphere mechanism via coordination of IO₄^? to chromium(III).     

Direct Esterification of Carboxylic Acids with Alcohols Catalyzed by Iron(III) Acetylacetonate Complex

Direct condensation of carboxylic acids and alcohols with electronic, steric, and functional group variations was carried out using the environmentally benign, moisture-stable, inexpensive, and recoverable iron(III) acetylacetonate [Fe(acac)₃] as catalyst (5 mol%). This iron salt efficiently catalyzed the esterification of several primary and secondary alcohols in refluxing xylene, without the need for a dehydration reagent. The chemoselectivity of the proposed protocol was demonstrated by the selective esterification of primary alcohol functionality in racemic 1-phenylethane-1,2-diol with benzoic acid. The esterification was also applicable to unmasked α -hydroxyacid, guasiaromatic, heterocyclic, and N-protected amino acids.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

A new hydrogen-bonded pseudo-dimer Mn(III) Schiff base complex. The synthesis, X-ray structure and spectroscopic studies

A new hydrogen-bonded pseudo-dimer, [Mn(III)L1(CH₃CH₂OH)]₂(ClO₄) (1) (L1 = N,N′-bis(2-hydroxy-1-naphthalidenato)-1,2-diaminopropane) has been synthesized and characterized by UV–vis, IR, elemental analysis and crystal structure analysis. The single crystal X-ray diffraction reveals that the structure affords an elongated octahedral MnN₂O₄ coordination environment, geometry with the four donor atoms of the tetradentate Schiff base in the equatorial plane and with two ethanol molecule in axial positions with Mn–O = 2.265(2) and 2.266(2) Å.     

Some novel manganese(III) porphyrins with catalytic properties

Abstract

A series of manganese(III) porphyrins with 4-methylimidazole have been prepared. These are high-spin complexes having general formula [Mn^III(THMPP)X(4-MeIm)], where THMP?=?5,10,15,20-tetra(4-hydroxy-3-methoxyphenyl)porphine ligand, X?=?Cl^?, Br^?, NCS^?, or N₃^? and 4-MeIm?=?4-methylimidazole. All the complexes have been characterized by UV-visible, FT-IR, ESI-MS spectra, elemental analyses and magnetic susceptibility measurements. These manganese(III) porphyrins oxidize aromatic alcohols to aldehydes. The oxidation reactions have been carried out at room temperature in the presence of oxidants such as NaIO₄, H₂O₂, and NaOCl. The comparative studies proved that NaIO₄ behaves as the most efficient oxidant in these oxidative transformation reactions.     

Comparative Study of Aerobic Alkene Epoxidations Catalyzed by Optically Active Manganese(iii) and Cobalt(ii) Salen Complexes

A comparative study of aerobic alkene epoxidations in the presence of pivalaldehyde catalyzed by the optically active Mn(III)Salen and Co(II)Salen complexes has been performed. The nature of the asymmetric induction is discussed.     

The Thermokinetics of the Formation Reactions of Cerium(III) n-dodecylbenzene Sulfonate and Cerium(III) Stearate

The thermokinetics of the formation reactions of cerium(III) n-dodecylbenzene sulfonate and cerium(III) stearate are studied by using a microcalorimeter. On the basis of experimental and calculated results, three thermodynamics parameters (the activation enthalpies, the activation entropies, the activation free energies), the rate constant, three kinetic parameters (the activation energies, the pre-exponential constant and the reaction order) and the enthalpies of the reaction of preparing cerium(III) n-dodecylbenzene sulfonate in the temperature range of 20–35°C and cerium(III) stearate in the temperature range of44.6–62.8°C are obtained. The results showed that the title reactions easily took place in the studied temperature. This revised version was published online in July 2006 with corrections to the Cover Date.