Reactivity of t-butyl chromate resins with substituted α-phenylethanols: A kinetic study

Polystyrene and polyacenaphthylene supports were functionalized to generate a t-butyl chromate function and the resulting polymer-supported reagents were used for the oxidation of alcohols. They were found to oxidize primary and secondary alcohols to the corresponding carbonyl compounds in quantitative yields. Oxidation of differently substituted α-phenylethanols was attempted for this purpose and the kinetics of oxidation reactions was studied. The reaction was found to be first order with respect to the substrate, the reaction being carried out with an excess of the t-butyl chromate reagent. The rate of oxidation was also found to be dependent on the nature of the substrate, concentration of the reagent function, and the nature and concentration of the acid catalyst used. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 799–804, 1998     

Evaluation of poly(butyl acrylate-co-ethylene glycol dimethacrylate) sorbents for chromatographic separation of biomolecules

Copolymers of butyl acrylate (BA) crosslinked with ethylene glycol dimethacrylate (EGDMA) were evaluated as potential chromatographic packings. It was found that slightly crosslinked copolymers (up to 30 wt.-% EGDMA) did not provide porous material, while for matrices which exceeded 40 wt.-% of EGDMA the porous structure remained unchangeable. The increase of crosslinker content mostly affected the surface hydrophobicity. Two methods of measurement of this property were discussed: Sorption of alkyl alcohols and amino acids. Taking the latter for testing, a polymer matrix hydrophobicity index was calculated as the slope of dependence of column capacity vs. amino acid hydrophobicity parameter. The indices were verified against well-established interaction energies of ? CH₂? groups of alkyl alcohols and polymer surfaces. Some benefits of the use of the hydrophobicity index in evaluation of polymer sorbents were demonstrated.     

Polymer-supported analogues of t-butyl hypohalites. Preparation and applications in synthetic organic chemistry

Crosslinked polymer-supported analogues of t-butyl hypochlorite and t-butyl hypobromite were prepared and developed as a new class of recyclable solid-phase oxidizing and halogenating reagents. The preparation of these new reagents involved a three-step polymer-analogous reaction starting from styrene-divinylbenzene crosslinked polymer. A ketone functional group was introduced into the copolystyrene-2% divinylbenzene resin beads by a Friedel-Crafts reaction with bromoacetone. This functional group was then converted to a tertiary alcoholic function on the polymer support by a Grignard reaction with methylmagnesium iodide. The treatment of this tertiary alcohol resin with sodium hypochlorite or sodium hypobromite yielded the polymeric t-butyl hypochlorite or hypobromite. These hypohalites were estimated iodometrically. These reagents were found to oxidize primary and secondary alcohols to the corresponding carbonyl compounds in high yields. They were also found to be suitable for halogenation of carbonyl compounds and amides. The spent polymeric reagent after the oxidation or halogenation step can be easily removed by filtration and can be regenerated many times by treating with the sodium hypohalite without any loss of capacity.     

Polyacenaphthylene supported t-butyl chromates: a new class of solid phase oxidizing reagents

Copolymers of acenaphthylene with divinylbenzene were functionalized by incorporating t-butyl chromate groups, and the resulting polymeric reagents were used to oxidize alcohols to carbonyl compounds. Primary and secondary alcohols were oxidized to the corresponding carbonyl compounds in quantitative yields. The extent of oxidation was found to depend on the various reaction parameters including the temperature, nature of the solvent, concentration of the reagent functions, duration of the reaction and the presence of catalyst. © 1998 SCI.     

Oxidation of alcohols mediated by a polymer supported potassium ferrate as an effective mild oxidant

The use of polymeric oxidizing agents simplifies routine oxidation of reactions because it eliminates the traditional purification. In this article, the use of the cross‐linked poly (4‐vinylpyridine)‐supported potassium ferrate as an effective mild polymeric oxidizing agent is described. This reagent is capable of oxidizing organic compounds and can be used as a versatile reagent in organic synthesis. Primary and secondary benzylic and allylic alcohols are converted selectively to their carbonyl compounds, and hydroquinone to the 1, 4‐benzoquinone. This polymeric reagent seems to be nontoxic and nonpollutant. Based on our observation during the study, the polymeric reagent is stable and can be stored for months without losing its activity. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

氯铬酸吡啶/硅胶载体氧化剂的制备及其对醇的氧化研究

利用二氧化硅作载体，负载氯铬酸吡啶制备了一种新的载体氧化剂，研究了该氧化剂的氧化性。该试剂制备简单，性质稳定，应用于各种醇的氧化，能高收率得到相应的醛（酮），反应操作简单，提纯方便。     

Selective oxidation of steroidal allylic alcohols using pyrazole and pyridinium chlorochoromate

Abastract This paper presents a modified method for the selective oxidation of allylic alchols. Pyrazole, when used with pyridinium chlorochromate, is a mild and useful reagent system for the rapid and selective oxidation of steroidal allylic alcohols to the corresponding α, β-unsaturated ketones. The reaction of each substrate was carried out by adding the oxidant to a dry methylene chloride solution containing pyrazole and an allylic alchol. This report is the first on the use of pyrazole to augment selective oxidation by a chronium (VI) reagent.     

A comparison of the oxidizing ability of polystyrene‐supported linear and cyclic polyoxyethylene bound permanganates

The grafting of linear and cyclic polyoxyethylenes into DVB‐crosslinked chloromethylpolystyrene was carried out by treating with polyethyleneglycol (PEG₆₀₀). The complexations of crosslinked polystyrene‐supported linear and cyclic polyoxyethylene with permanganate functions were carried out. With this reagent, primary alcohols and secondry alcohols were converted to aldehydes and ketones and aldehyde to acid. The polymer acts as a reservoir of permanganate functions and releases them slowly as the substrates are being used up. The effect of solvent, molar excess of reagent, time, and temperature on oxidation behavior were investigated by choosing benzoin to benzil conversion as the model reaction. The linear polymeric reagent has greater reactivity than the cyclic polymer due to the greater availability of the reactive sites in the linear polymer than the cyclic polymer. Polymeric reagent could be used in excess to get a good yield without causing any separation problems and over oxidation products. The reagents have advantages of easy separation, regeneration and reuse. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1897–1905, 2005     

Oxidation of primary and secondary alcohols to the corresponding carbonyl compounds with molecular oxygen using 1,1-diphenyl-2-picrylhydrazyl and WO3/Al2O3 as catalysts

The oxidation of primary and secondary alcohols to their corresponding carbonyl compounds proceeds with high efficiency under molecular oxygen in the presence of 1,1-diphenyl-2-picrylhydrazyl (DPPH) and tungsten oxide/alumina (WO₃/Al₂O₃). The method is environmentally benign, because the reaction requires only molecular oxygen as the terminal oxidant and gives water as a side product. Various aromatic, alicyclic, and aliphatic alcohols can be converted to their corresponding carbonyl compounds in excellent yields. It is noteworthy that the oxidative transformation of the alcohols proceeds chemoselectively in the presence of other functional groups. In addition, a plausible catalytic pathway is proposed.     

TEMPO‐Copper(II) Diimine‐Catalysed Oxidation of Benzylic Alcohols in Aqueous Media

In situ generated copper(II)‐diimine complexes combined with TEMPO (2,2,6,6‐tetramethylpiperidinyl‐1‐oxyl radical) were studied in the oxidation of benzylic alcohols, the focus being on enviromentally benign reaction conditions. In this respect, reactions were studied in aqueous alkaline solutions and dioxygen was used as an end oxidant. This simple catalytic system turned out to be highly efficient and selective in the oxidation of primary and secondary benzylic alcohols to their corresponding carbonyl compounds. Under optimised reaction conditions [5 mol % of TEMPO, 3 mol % of copper(II ) diimine, pH 12.6–13.5, 80 °C, 10 bar O₂] benzyl alcohol was quantitatively and selectively oxidised to benzaldehyde. According to ESI‐MS studies, coordination of TEMPO, as well as deprotonated benzyl alcohol to the parent copper‐diimine complex in aqueous solutions is feasible. Supported by these observations a plausible reaction mechanism is proposed for the oxidation reaction.     

Design and applications of a solid-phase oxidizing reagent consisting of a crosslinked polystyrene matrix and a t-butyl hypochlorite function separated by a trimethylene spacer

A crosslinked polystyrene–supported solid-phase analogue of t-butyl hypochlorite containing a trimethylene spacer group between the polymer matrix and the t-butyl hypochlorite function was prepared and used as a recyclable oxidizing reagent for alcohols. The synthetic route to this new polymeric reagent involved a seven-step polymer-analogous reaction starting from styrene-divinyl benzene 2%-crosslinked polymer. A β-ketopropionic acid function was introduced into the polystyrene matrix by Friedel–Crafts reaction with succinic anhydride. The keto function in the resulting polymer (2) (capacity, 3.57 meq of COCH₂CH₂COOH/g) was converted to the methylene group by Clemmensen reduction using zinc amalgam and HCl. The carboxyl function in the product polymer (3) was converted to the acylmalonic ester function by malonic ester synthesis through the reaction of the polymeric acid chloride (4) with ethoxymagnesium diethylmalonate. The polymeric acyl malonic ester (5) was decarboxylated to yield the 2-oxopentyl polystyrene resin (6). This on Grignard reaction with methyl magnesium iodide followed by hydrolysis afforded the polystyrene derivative with the t-butyl alcohol function separated by three methylene groups (7) . The t-butyl alcohol resin (7) was converted to the corresponding hypochlorite resin (8) by reaction with sodium hypochlorite. The resin was found to have a capacity of 2.84 mmol Cl/g by iodometric analysis. The capacities of the resins 2–8 were determined from the weight changes in the corresponding conversions and verified by quantitative determination of the functional groups. This new hypochlorite was found to oxidize alcohols to carbonyl compounds in 85–98% yield. The oxidizing efficiency of this new reagent was found to be significantly greater than those of the reagents containing only one spacer and no spacer between the reagent function and the polymer support. The presence of a 3-methylene spacer also facilitated the hypochlorite formation step significantly.     

Anchoring of Copper(II) Schiff Base Complex into Aminopropyl-Functionalised MCM-41: A Novel,Efficient and Reusable Catalyst for Selective Oxidation of Alcohols

A copper(II) complex containing tetradentate N₂O₂ Schiff base ligand immobilized into aminopropyl-functionalised MCM-41 (mobile crystalline material number 41), was prepared and characterized by Fourier-transform infrared, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, N₂ adsorption–desorption and inductively coupled plasma analysis techniques. The novel heterogeneous catalyst, MCM-41-pr-NH₂-CuL, can be successfully applied for efficient and selective oxidation of different primary and secondary alcohols to the corresponding carbonyl compounds using hydrogen peroxide as an oxidant in acetonitrile at 60 °C. The effect of reaction parameters such as solvent, amount of catalyst, temperature and kind of oxidant on the oxidation of benzyl alcohol was also studied. The prepared catalyst could be recovered and reused four times without important loss of its catalytic performance. The heterogeneous MCM-41-pr-NH₂-CuL catalyst was found to be catalytically more active in the oxidation of alcohols compared to the similar type of copper(II) Schiff base complex in homogeneous media under the same reaction conditions.     

Catalytic oxidation of alcohols by a double functional ionic liquid [bmim]BF4

A selective oxidation of alcohols to corresponding carbonyl compounds in room temperature ionic liquid [bmim]BF₄ was achieved by using sodium hypochlorite as the oxygen source. The catalytic system can be recycled and reused for five runs without any significant loss of catalytic activity.     

Reduction and hydroboration with borane and haloborane complexes of poly(propylene sulfide) grafted on crosslinked polystyrene

Preparation of borane and haloborane complexes of poly(propylene sulfide) grafted on crosslinked polystyrene was investigated. Graft polymer–borane was prepared by reaction of graft polymer with B₂H₆ and BH₃–THF. Graft polymer–haloborane was prepared by reaction with haloborane–tetrahydrofuran and by reaction of borane-bound graft polymer with halogen. Graft polymers with high borane (2.44 mmol/g) and haloborane (163 mmol/g) content were reached. The use of these graft polymers as polymeric reagents for reduction of carbonyl compounds and hydroboration was investigated. Aldehydes, ketones, carboxylic acids, and esters were reduced in high yields to the corresponding alcohols by borane-bound graft polymer. The graft polymer showed good chemoselectivity in competative reduction of cyclohexanone and other ketones and aldehydes, as well as in competative reduction of acetophenone and benzaldehyde. Reactivity of graft and homopolymer–borane was similar to that of borane–methyl sulfide. Hydroboration of alkenes with these graft polymers, followed by alkaline oxidation, led to the formation of the corresponding alcohols in high yields. Hydroboration was highly regioselective. Stability of the graft polymer–borane and recycling of that graft polymer were investigated. Cleavage of the poly(propylene sulfide) by the borane bound polymer took place to some extent. At 0°C no borane loss was found over a 5-week period. When recycled, 85% of the original borane content could be regenerated at the end of the fourth cycle.     

A Highly Selective Pd(OAc)<Subscript>2</Subscript>/Pyridine/K<Subscript>2</Subscript>CO<Subscript>3</Subscript> System for Oxidation of Terpenic Alcohols by Dioxygen

Abstract  

Molecular sieves, complex organic bases and radical oxidants are commonly used in alcohols oxidation reactions. In this work, we have evaluated the beneficial effects of addition of K₂CO₃ to Pd(II)-catalyzed oxidation alcohols, which resulted in a remarkable increase in the oxidation reaction rates without selectivity losses. Herein, in a metallic reoxidant-free system, terpenic alcohols (β-citronellol, nerol and geraniol) were selectively converted into respective aldehydes from Pd(II)-catalyzed oxidation reactions in presence of dioxygen. High conversions and selectivities (greater than 90%) were achieved in the presence of the Pd(OAc)₂/K₂CO₃ catalyst and pyridine excess. The exogenous role of others auxiliary anionic and nitrogen compounds was appraised.     

Polyhalide Derivatives of Polystyrene-based Benzyltriethylammonium Resins as Oxidizing Reagents: Synthetic and Reactivity Correlations

The oxidation of alcohols using polystyrene-based benzyltriethylammonium dichloroiodate, tetrachloroiodate and dichlorobromate reagents is described. On reaction with different alcohols, the polymeric polyhalide reagents afforded the respective carbonyl compounds in high yields. The insoluble spent reagents could be regenerated and reused without significant loss in reactivity. The reactivities of the polymeric polyhalides were investigated as a function of the nature of solvents, effective molar concentration of the reagent, temperature and by varying the polarity of the macromolecular support, and the results are discussed. © of SCI.     

Green and reusable heteropolyacid catalyzed oxidation of benzylic,allylic and aliphatic alcohols to carbonyl compounds

Benzylic, allylic and aliphatic alcohols were transformed into the corresponding carbonyl compounds by catalytic oxidation of preyssler type heteropolyacid supported onto silica gel, H₁₄[NaP₅W₃₀O₁₁₀]/SiO₂, in a heterogeneous system. The catalyst can be recovered and reused.     

Study on quantitative analyses of hydroperoxides and alcohols by NMR shift reagent

Recently, much literature concerning the effects of NMR shift reagents upon compounds with Lewis’s basic functional groups have been reported. These literatures have shown the effects of NMR shift reagents upon hydroxyl, amino, carbonyl, ether, ester carbonyl, cyano, and epoxy compounds but not hydroperoxyl compounds. Chemical and paramagnetic shifts of protons in t-butyl and cumene hydroperoxides, t-butyl and 2-phenyl-2-propyl alcohols, and autoxidized methyl linoleate with incremental additions of an NMR shift reagent were determined. These experimental results indicated that each alcohol and hydroperoxide could be determined separately and quantitatively even in their mixtures. Moreover, this method can be recommended to obtain information about the structures of hydroperoxides, as well as alcohols.     

Polystyrene‐supported polyoxyethylene bound potassium permanganate as a heterogeneous oxidizing agent

Oxidation behavior of a 2 mol % divinylbenzene (DVB)‐crosslinked polystyrene‐supported permanganate function was investigated toward low molecular weight primary and secondary alcohols and aldehydes. The permanganate function was attached to a polystyrene support through cyclic polyoxyethylene (POE) units immobilized on the support. Contrary to the oxidations catalyzed by low molecular weight permanganate reagents, the oxidation of primary alcohol terminated in the aldehyde stage. The secondary alcohols were converted to the respective ketone and aldehyde to acid. The effect of the variable parameters similar to solvent, temperature, and reagent to substrate ratio was followed. Nonpolar cyclohexane was found to be the best solvent for the present study. Also the reactivity increased with increasing temperature. The oxidizing reagent possesses a long shelf life and could be recycled several times without reduction of capacity and mechanical stability. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3708–3717, 2003