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.     

Oxidation of methyl phenyl sulfide with hydrogen peroxide catalyzed by Ti(IV)-substituted heteropolytungstate

Alkylammonium salts of Ti(IV)-substituted heteropolytungstate, PW₁₁TiO ₁₀ ⁵⁻ , catalyze the oxidation of methyl phenyl sulfide with hydrogen peroxide. The yield of the corresponding sulfoxide and sulfone is practically quantitative. A³¹P NMR study confirms the formation and reactivity of the PW₁₁O₃₉TiO ₂ ⁵⁻ peroxo complex in organic media.     

Oxidation of triethylamine by molecular oxygen catalyzed by Ru(III)-ion

The kinetics of Ru(III) catalyzed oxidation of triethylamine by molecular oxygen has been investigated in the pH range 1.5 to 2.5 at 35°C and I=0.1 M KCl. The reaction is first order with respect to substrate, catalyst and molecular oxygen concentrations. The rate of the reaction increases with the increase of pH from 1.5 to 2.5 and then there is a slight decrease in the rate above pH 2.5. Based on the kinetic data, a mechanism for the catalytic oxidation of triethylamine is proposed. The major products in the oxidation of triethylamine are the N-oxide, diethylamine and acetaldehyde.

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, Ru(III), pH=1,5+2,5 35°C I=0,1M KCl. , . pH 1,5 2,5, pH 2,5. , . N-, .

     

模拟细胞色素P-450和仿生氧化反应研究III. 有关用TPPFe(III)Cl及TPPMn(III)Cl催化的环己烷充氧化反应机理的初步探讨

本文研究了ArIO充氧化环己烷的反应体系。在TPPFe(III)Cl及TPPMn(III)Cl催化下进行了动态UV-Vis谱和ESR分析,提出了二种催化体系可能由二种不同递氧中间体的反应机理。     

Oxidation of olefins and sulfides with different oxidants catalyzed by meso-tetra(n-propyl)porphyrinatomanganese(III) acetate: comparison with meso-tetra(phenyl)porphyrinatomanganese(III) acetate

In this study, the catalytic activity of meso-tetra(n-propyl)porphyrinatomanganese(III) acetate, MnT(n-pr)(OAc) in oxidation of olefins and sulfides with tetra-n-butylammonium Oxone (TBAO), tetra-n-butylammonium periodate (TBAP), aqueous hydrogen peroxide, sodium periodate and Oxone in the presence of imidazole (ImH) has been studied. The comparison of catalytic performance of MnT(n-pr)P(OAc) and MnTPP(OAc) in oxidation of olefins with TBAP shows that while the latter is four times more efficient than the former, the extent of oxidative degradation of the former is ca. 3.5 times greater than the latter. The use of excess amount of styrene resulted in only a ca. 10 % increase in the catalyst stability, suggesting a mainly intramolecular mechanism for the catalyst degradation. On the other hand, in the case of TBAO, the oxidative degradation of the former is four times greater than the latter, but the catalytic performance of the latter for the oxidation of cyclohexene was only ca. 2 times larger than the former. This observation shows that the decreased catalytic performance of MnT(n-pr)P(OAc) relative to MnTPP(OAc) is essentially due to the high degree of degradation of the former. Due to the high degree of catalyst degradation, oxidation of olefins with periodate and Oxone in the presence of the two manganese porphyrins in aqueous solution (or with hydrogen peroxide in dichloromethane) gave little or no product. Oxidation of sulfides with TBAO and TBAP in the presence of MnT(n-pr)P(OAc) showed a conversion of ca. 15 % for the catalytic oxidation of sulfides to sulfones.     

Cr(III)(salen)Cl catalyzed asymmetric epoxidations: insight into the catalytic cycle

Intermediates of chromium-salen catalyzed alkene epoxidations were studied in situ by EPR, (1)H and (2)H NMR, and UV-vis/NIR spectroscopy (where chromium-salens were (S,S)-(+)-N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamino chromium(III) chloride (1) and racemic N,N'-bis(3,4,5,6-tetra-deuterosalicylidene)-1,2-cyclohexanediamino chromium(III) chloride (2)). High-valence chromium complexes, intermediates of epoxidation reactions, were detected and characterized by EPR and NMR. They are the reactive mononuclear oxochromium(V) intermediate (A) Cr(V)O(salen)L (where L = Cl(-) or a solvent molecule) and an inactive chromium-salen binuclear complex (B) which acts as a reservoir of the active species. The latter complex demonstrates an EPR signal characteristic of oxochromium(V)-salen species and (1)H NMR spectra typical for chromium(III)-salen complexes, and it is identified as mixed-valence binuclear L(1)(salen)Cr(III)OCr(V)(salen)L(2) (L(1), L(2) = Cl(-) or solvent molecules). The intermediates Cr(V)O(salen)L and L(1)(salen)Cr(III)OCr(V)(salen)L(2) exist in equilibrium, and their ratio can be affected by addition of donor ligands (DMSO, DMF, H(2)O, pyridine). Addition of donor additives increases the fraction of A over that of B. The same two complexes can be obtained with m-CPBA as oxidant. Reactivities of the Cr(V)O(salen)L complexes toward E-beta-methylstyrene were measured in DMF. The L(1)(salen)Cr(III)OCr(V)(salen)L(2) intermediate has been proposed to be a reservoir of the true reactive chromium(V) species. The chromium-salen catalysts demonstrate low turnover numbers (ca. 5), probably due to ligand degradation processes.     

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.     

Oxidation of selected sugars with Mn(III)

Glucose, fructose, xylose, arabinose, and sucrose have been determined titrimetrically using manganese(III) sulfate as an oxidant. On reaction in the dark, glucose consumes 5, fructose 7, xylose and arabinose 6 each, and sucrose after hydrolysis 12 equivalents of Mn(III) per mole, respectively. Sucrose has also been estimated following other methods and the results have been compared. Two leaf sample extracts are analyzed for the determination of reducing sugar and total reducing matter and the results are compared with those obtained by the other method.     

Oxidation of some sugars with copper(III)

The titrimetric determination of glucose, fructose, mannose, galactose, arabinose, xylose and sucrose with potassium ditelluratocuprate(III) is described. On heating, pentoses and hexoses consume 20 and 24 equivalents of copper(III) per mole respectively, and sucrose consumes 48 equivalents.     

Oxidation of americium(III) with sodium bismuthate

The oxidation of americium(III) with sodium bismuthate has been investigated in a nitric acid solution. The lower the acidity, the more rapidly the oxidation of americium(III) to americium(VI) proceeds, especially at higher temperatures. Based on this finding, a procedure was developed to oxidize americium(III) completely at low concentrations. The americium(VI) free from the excess oxidant has been found to be stable only at 0°C, irrespective of the acidity, but to be more unstable at the temperature higher than 10°C, especially at lower acidities.     

Oxidation of chromium(III) by alkaline hexacyanoferrate(III)

Alkaline hexacyanoferrate(III) oxidation of freshly prepared solutions of Cr^III (pH>12) at 27°C follows the rate law, Equation 1:

Oxidation of 4-chromanones with thallium(III) nitrate

Treatment of 4-chromanones 1a-g with thallium(III) nitrate in acidic methanol results mainly in dehydrogenation, whereas α-methoxylation and/or Taylor-McKillop rearrangement predominate in trimethyl orthoformate. The mechanistic features of these oxidations are briefly discussed.     

Oxidation of alkanes catalyzed by manganese(III) porphyrin in an ionic liquid at room temperature

Efficient oxidation of alkanes is achieved by using an electron-deficient manganese(III) porphyrin catalyst in combination with iodobenzene diacetate in an ionic liquid at room temperature; a high-valent manganese-oxo porphyrin complex (Mn^VO) was considered as the reactive oxidation intermediate.     

Gold(III) sorption with copolymers derived from divinyl sulfide

Sorption recovery of gold(III) from aqueous mineral acids with copolymers of 4-vinylpyridine and 2-methyl-5-vinylpyridine with divinyl sulfide was studied.     

Rhodium(III) catalyzed oxidation of cyclic ketones by alkaline hexacyanoferrate(III)

The kinetics of the oxidation of 2-methyl cyclohexanone and cycloheptanone with Fe(CN)₆ ³⁻ catalyzed by RhCl₃ in alkaline medium was investigated at four temperatures. The rate follows direct proportionality with respect to lower concentrations of hexacyanoferrate(III) ion, but tends to become zero order at higher concentrations of the oxidant, while the reaction shows first-order kinetics with respect to hydroxide ion and cyclic ketone concentrations. The rate shows a peculiar nature with respect to RhCl₃ concentrations in that it increases with increase in catalyst at low catalyst concentrations but after reaching a maximum, further increase in concentration retards the rate. An increase in the ionic strength of the medium increases the rate, while increase in the Fe(CN)₆ ⁴⁻ concentration decreases the rate.     

Samarium(III) catalyzed one-pot construction of coumarins

Samarium(III) nitrate hexahydrate as a catalyst is used as an alternative to conventional acid catalysts in the von Pechmann condensation of phenols with ethyl acetoacetate leading to the formation of coumarin derivatives.     

Oxidation of symmetric disulfides with hydrogen peroxide catalyzed by Methyltrioxorhenium(VII)

Organic disulfides with both alkyl and aryl substituents are oxidized by hydrogen peroxide when CH(3)ReO(3) (MTO) is used as a catalyst. The first step of the reaction is complete usually in about an hour, at which point the thiosulfinate, RS(O)SR, can be detected in nearly quantitative yield. The thiosulfinate is then converted, also by MTO-catalyzed oxidation under these conditions, to the thiosulfonate and, over long periods, to sulfonic acids, RSO(3)H. In the absence of excess peroxide, RS(O)SR (R = p-tolyl), underwent disproportionation to RS(O)(2)SR and RSSR. Kinetics studies of the first oxidation reaction established that two peroxorhenium compounds are the active forms of the catalyst, CH(3)ReO(2)(eta(2)-O(2)) (A) and CH(3)ReO(eta(2)-O(2))(2).(OH(2)) (B). Their reactivities are similar; typical rate constants (L mol(-)(1) s(-)(1), 25 degrees C, aqueous acetonitrile) are k(A) = 22, k(B) = 150 (Bu(2)S(2)) and k(A) = 1.4, k(B) = 11 (Tol(2)S(2)). An analysis of the data for (p-XC(6)H(4))(2)S(2) by a plot of log k(B) against the Hammett sigma constant gave rho = -1.89, supporting a mechanism in which the electron-rich sulfur attacks a peroxo oxygen of intermediates A and B.     

Oxidation of methyl α-acylaminocrotonates with thallium (III) acetate

The reaction of methyl α-acylaminocrotonates with thallium(III) acetate in methanol results in the formation of a mixture of diastereomeric α,β-dimethoxy derivatives. The mechanism and stereochemistry are discussed.