Catalytic oxidation of furan and hydrofuran compounds 8. Synthesis of 5-ethoxycarbonyl-4-hydroxy-3-oxo-2(3H)-furanone by the oxidation of furfural in the system aqueous H2O2-VOSO4-ethanol

The special features of the oxidation of furfural by aqueous hydrogen peroxide in the presence of vanadyl sulfate and ethanol has been studied for the first time. It has been established that this reaction proceeds with the formation of previously unknown oxidation products of furan compounds, one of which was isolated from the reaction mixture as the ethyl ester. It was established by spectral methods and qualitative reactions that this product is 5-ethoxycarbonyl-4-hydroxy-3-oxo-2(3H)-furanone. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 386–392, March, 2008.     

Metal nature effect on catalytic reactions in furfural-H2O2-H2O-group V or VI d-metal salt systems in acid media

Homogeneous catalytic reactions of furfural oxidation by hydrogen peroxide in an aqueous medium in the presence of catalytic amounts of a vanadium, niobium, molybdenum, or chromium salt have been studied to compare them with the acid-autocatalytic reaction. The formation of peroxo complexes of the corresponding metals has been established. The interaction of these peroxo complexes with the carbonyl group of furfural affords organic metal-containing peroxides. The subsequent transformations of these peroxides in the presence of the indicated catalysts lead to different dominant final products. This is explained by different mechanisms of the oxidation of the key intermediates, namely, 2-formyloxy- and 2-hydroxyfurans. In the presence of the vanadium and molybdenum salts, the catalytic role of the resuting carboxylic acids is insignificant, as distinct from what is observed in the acid-autocatalyzed reaction.

     

Catalytic oxidation reactions of furan and hydrofuran compounds 9.* characteristics and synthetic possibilities of the reaction of furan with aqueous hydrogen peroxide in the presence of compounds of niobium (ii) and (v)

The effect of the catalytic characteristics of compounds of niobium(II) and (V) on the duration and the composition of the products during the oxidation of furfural by aqueous hydrogen peroxide was studied. It was established that the process is intermediate in its main characteristics between reactions of the compounds taking place under the conditions of autocatalysis by the acids that are formed and in the presence of the vanadium compounds. The main product of the reaction is 2(5H)-furanone. A method is proposed for its production with yields of up to 60%.     

Catalytic Oxidation of Furan and Hydrofuran Compounds. 7. Production of 2(5H)-Furanone by Oxidation of Furfural with Hydrogen Peroxide and Some of Its Transformations in Aqueous Solutions

Data on the synthesis of 2(5H)-furanone by the oxidation of furfural with aqueous hydrogen peroxide under the conditions of autocatalysis by the accumulating acids and also in the presence of catalytic amounts of Cr(VI) and Mo(VI) compounds are presented. Some transformations of 2(5H)-furanone in aqueous solutions are studied: hydrolysis, oxidation by potassium permanganate, complex formation with the ions of certain d-metals.     

Structural diversity of peroxidase-catalyzed oxidation products of o-methoxyphenols

[reaction: see text] The biocatalytic oxidation of o-methoxyphenolic compounds led to a variety of oligophenols (dimers to pentamers) and some of their oxidation products. The reaction was carried out in an aqueous medium at room temperature with hydrogen peroxide as the terminal oxidant in a facile and green route to potentially bioactive compounds. Detailed structural information on the products of peroxidase-catalyzed oxidation of o-methoxyphenols is presented for the first time.     

Efficiency of phase-transfer catalysis in cyclopentene epoxidation with hydrogen peroxide

The effect of the structure and amount of the phase-transfer catalyst (quaternary ammonium salts) and the solvent effect on cyclopentene oxidation with an aqueous hydrogen peroxide solution in the liquid-liquid two-phase system was studied. The phase-transfer catalyst and solvent ensuring high reaction rate and high selectivity with respect to target products were chosen.     

Comparison of the reactivities of ketones and aldehydes of the furan series during oxidation with hydrogen peroxide

The rates of oxidation of 2-acetylfuran, 5-methyl-2-acetylfuran, furfural, and 5-methyl-furfural with hydrogen peroxide were compared. The intermediate and final oxidation products were determined. The possibility of identical reaction mechanisms for furan aldehydes and ketones is demonstrated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 443–446, April, 1972     

Kinetics and mechanism of the furan peroxide formation in the reaction of furfural with hydrogen peroxide in the presence or absence of sodium molybdate

The kinetics of the initial stage of the furfural reaction with hydrogen peroxide was studied in water in the presence of Na₂MoO₄ and in n-butanol without a catalyst. The mechanisms of furfural conversion in the Na₂MoO₄-H₂O₂ system and oxidation by hydrogen peroxide in the absence of sodium molybdate are discussed. Based on kinetic studies, the mechanism of furan peroxide formation is proposed. Proceedings of X International Conference on Chemistry of Organic and Organoelement Peroxides (Moscow, June 16–18, 1998).     

Influence of the reaction conditions on the nature of the hydrogen peroxide oxidation products of furfural

UV irradiation causes no acceleration of the oxidation of furfural by hydrogen peroxide but maintains its occurrence at a uniform rate. Both with UV irradiation and without it, the oxidation of furfural by hydrogen peroxide takes place via the formation of intermediate peroxide compounds, with their subsequent conversion mainly into a mixture of -formylacrylic, maleic, and succinic acids. The ratio between the acids depends on the reaction conditions. The possibility has been shown of a directed oxidation to -formylacrylic acid.     

ToF‐SIMS characterization of glyoxal surface oxidation products by hydrogen peroxide: A comparison between dry and liquid samples

As one of the simplest volatile organic compounds, glyoxal and its oxidation products were considered to be important precursors to aqueous secondary organic aerosol formation. Herein, we analyzed products from glyoxal oxidation by hydrogen peroxide in dry and liquid samples using time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). ToF‐SIMS spectra and spectral principal component analysis (PCA) were used to investigate surface oxidation products. Dry samples were prepared on clean silicon wafers. Liquid samples consisting of glyoxal and hydrogen peroxide (H₂O₂) were introduced to a vacuum compatible microfluidic reactor prior to UV illumination or dark aging followed by in situ liquid SIMS analysis. A number of reaction products were observed in both dry and liquid samples; different oligomers and carboxylic acids could be formed depending on reaction conditions. In addition, hydrolyzed products were observed in the liquid samples, but not in the dry samples. Although dry samples reveal some products of the aqueous process, they are not fully representative as results from those of the aqueous samples. Our findings suggest that the ability to characterize the liquid surface reaction products provides more realistic information of the reaction products associated with aqueous secondary organic aerosol formation in the atmosphere. Meanwhile, the high mass resolution spectra from the dry sample SIMS measurement are helpful to identify oxidation products in the liquid samples.     

Reactions of catalytic oxidation of furan and hydrofuran compounds. I. General principles of the oxidation of furan in the system hydrogen peroxide-vanadium(IV) compounds depending on the type of solvent and catalyst

The oxidation of furan by aqueous hydrogen peroxide catalyzed by vanadium(IV) compounds was studied in homogeneous aqueous alcohol medium and a heterogeneous system in the presence of tridecylmethylammonium chloride. The optimum conditions of the process were determined for both versions. It was shown that they are similar in direction, duration, and degree of conversion of furan. At the same time, the composition and total yield of the products, as well as their yields in the organic and aqueous phases, depend on the type of solvent and vanadium catalyst.Kuban State Technological University, Krasnodar 350072. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 633–638, May, 1996. Original article submitted January 29, 1996.     

A water-soluble and "self-assembled" polyoxometalate as a recyclable catalyst for oxidation of alcohols in water with hydrogen peroxide

We have demonstrated that a simply prepared water-soluble polyoxometalate, Na12[WZnZn2(H2O)2(ZnW9O34)2], synthesized from readily available zinc and tungsten salts in the presence of nitric acid, is an effective catalyst for selective alcohol oxidation with hydrogen peroxide in biphasic (water-alcohol) reaction media. Experiments have shown that the "self-assembled" catalyst in its mother liquor was as active as the isolated catalyst. The aqueous catalyst solution is easily separated from the water-insoluble products and can be recycled without loss in activity or selectivity.     

Photometric and Gas-Chromatographic Determination of Hydrogen Peroxide and Peroxybutanoic Acid in Oxidized Butanoic Acid

Procedures were developed for determining hydrogen peroxide and peroxy acids mixed with peroxide compounds of other classes in the oxidation products of butanoic acid with atmospheric oxygen and hydrogen peroxide. Conditions were found for the selective decomposition of hydrogen peroxide with catalase in the presence of an excess of the carboxylic acid deactivating the enzyme. The errors introduced by the acylation of hydrogen peroxide with the carboxylic acid in the course of sample treatment with the enzyme were eliminated by adding diphenyl sulfide or dimethyl sulfoxide, which selectively reduced the peroxy acids. The concentrations of hydrogen peroxide and the peroxy acid were found from the difference between the total concentration of the peroxide compounds before and after treating a sample with catalase and a sulfur-containing reagent by the photometric method using a reagent containing Fe²⁺ ions and N, N-dimethyl-p-phenylenediamine. Peroxy acids were determined by GLC from the yields of the oxidation products of diphenyl sulfide with the peroxy acid (diphenyl sulfoxide and diphenyl sulfones).     

Stationary Kinetics of Light Olefin Oxidation by Hydrogen Peroxide in Aqueous Alkali Solutions in the Presence of Fe(III) Oxide

The steady-state kinetics of ethylene and propylene oxidation by hydrogen peroxide in the presence of Fe(III) oxide in aqueous solutions with the permanent adding of H₂O₂ to the reaction medium was studied. The use of an original method for the study of the steady-state reaction kinetics with gas chromatographic detection of substrate consumption from the gas phase made it possible to estimate the apparent rate constants of ethylene oxidation, the ratio of the rate constants of propylene and ethylene oxidation, the reaction orders with respect to the substrate and oxidant concentration, the dependence of the apparent rate constant of ethylene oxidation on the catalyst weight and on the pH of solution, and the apparent activation energy of the process under condition of substrate distribution between the gas and liquid phases. It was found that the kinetic isotope effect in ethylene oxidation is almost absent when completely deuterated ethylene is used.     

Oxidative dihydroxylation of alicyclic unsaturated hydrocarbons with vinyl- and norbornene fragments in pseudohomogenic system

Oxidation of alicyclic unsaturated hydrocarbons (4-vinylcyclohexene, 5-vinylnorbornene, 5-cyclohexenylnorbornene, and 5-vinylbicyclooctene) with 30% hydrogen peroxide solutions and percarbamide is studied. Reaction was carried out at 40–70°C in the presence of heterogenized peroxocomplex compounds of molybdenum and tungsten formed “in situ” in the reaction of metal oxohalides with H₃PO₄, nano-dimensional particles of carbon material, and hydrogen peroxide. Main oxidation products of alicyclic diene hydro-carbons are the corresponding unsaturated epoxides and diols. Depending on the reaction condition their ratio varies in a wide range.     

过氧化氢水溶液催化氧化环戊烯制备戊二醛

用过氧化氢水溶液氧化环戊烯制得戊二醛。对多种催化剂-溶剂体系进行了试验, 在钨酸-叔丁醇体系中得到了最高的戊二醛得率: 近60%(30%过氧化氢水溶液为氧化剂)或80%(50%过氧化氢水溶液为氧化剂)。同时, 对该反应的机理进行了初步研究, 提出环戊烯被过氧化氢氧化为戊二醛是经过环氧化物中间产物的观点。     

Catalysis by heteropolyacid—VII. catalytic oxidation of cyclohexanol by dodecamolybdate

In the oxidation of cyclohexanol to cyclohexanone and the further oxidation to adipic acid, a dodecamolybdo-heteropolyanion (HPA) functions catalytically in the presence of aqueous hydrogen peroxide, whereas the HPA without hydrogen peroxide reacts only stoichiometrically. Air- or oxygen-passing through the refluxing system of cyclohexanone and the HPA in the presence of active charcoal, without hydrogen peroxide, has also promoted the oxidation catalytically. Since both hydrogen peroxide and aeration in the presence of active charcoal convert the reduced-form (blue) of the HPA produced by the oxidation of substrate to the oxidized-form (yellow), they play a role as a promoter or a reoxidizing reagent for the oxidation by the HPA. The reoxidizing effect of the aqueous hydrogen peroxide is much the more effective.     

Vanadium haloperoxidase-catalyzed bromination and cyclization of terpenes

Marine red algae (Rhodophyta) are a rich source of bioactive halogenated natural products, including cyclic terpenes. The biogenesis of certain cyclic halogenated marine natural products is thought to involve marine haloperoxidase enzymes. Evidence is presented that vanadium bromoperoxidase (V-BrPO) isolated and cloned from marine red algae that produce halogenated compounds (e.g., Plocamium cartilagineum, Laurencia pacifica, Corallina officinalis) can catalyze the bromination and cyclization of terpenes and terpene analogues. The V-BrPO-catalyzed reaction with the monoterpene nerol in the presence of bromide ion and hydrogen peroxide produces a monobromo eight-membered cyclic ether similar to laurencin, a brominated C15 acetogenin, from Laurencia glandulifera, along with noncyclic bromohydrin, epoxide, and dibromoproducts; however, reaction of aqueous bromine with nerol produced only noncyclic bromohydrin, epoxide, and dibromoproducts. The V-BrPO-catalyzed reaction with geraniol in the presence of bromide ion and hydrogen peroxide produces two singly brominated six-membered cyclic products, analogous to the ring structures of alpha and beta snyderols, brominated sesquiterpenes from Laurencia, spp., along with noncyclic bromohydrin, epoxide, and dibromoproducts; again, reaction of geraniol with aqueous bromine produces only noncyclic bromohydrin, epoxide, and dibromoproducts. Thus, V-BrPO can direct the electrophilic bromination and cyclization of terpenes.     

Specific features of formyl- and acetylferrocene oxidation with peroxides in water and organic solvents

Specific features of formyl- and acetylferrocene oxidation with peroxides ROOR (R = H, tert-C₄H₉) in different solvents are studied. It is shown that despite of the presence in complexes of strong electronacceptor substituents they can be oxidized with hydrogen peroxide in the absence of strong Brønsted acids. Dilution of water with organic solvent leads to deceleration and complete standstill of the reaction. In the absence of acids the second order of the process with respect to peroxide and first one with respect to the metal complex was evaluated. In the presence of perchloric or trifluoroacetic acid the order with respect to peroxide decreases to the first one. The dependence of the reaction rate on the concentration of acid has an extremum point. The activity of other peroxides in the reaction with the above-mentioned compounds is significantly lower than the activity of hydrogen peroxide. Probable alternative mechanisms of oxidation of the abovementioned ferrocenes with hydrogen peroxide in the presence and in the absence of acids differing in the way of coordination of reagents with one another and considering direct participation of substituent in the oxidation is suggested.