Catalytic Oxidation of Alcohols with Hydrogen Peroxide

Catalytic Oxidation of Alcohols with Hydrogen Peroxide 

In the aerobic oxidations discussed in the preceding sections, the most effective catalysts tend to be late transition elements, for example, Ru and Pd, that operate via oxometal or hydridometal mechanisms. In contrast, the most effective catalysts with H2O2 (or RO2H) as the oxidant tend to be early transition metal ions with a d° configuration, for example, Mo(VI), W(VI), and Re(VII), which operate via perox-ometal pathways. Ruthenium and palladium are generally not effective with H2O2 

Unsaturated alcohols generally undergo selective oxidation of the alcohol moiety (Eqs. (5.23) and (5.24)), but, when an allylic alcohol contained a reactive trisub-stituted double bond, selective epoxidation of the double bond was observed (Eq. (5.25)). 

Molybdenum- and tungsten-containing heteropolyanions are also effective catalysts for alcohol oxidations with H2O2 (134-136]. For example, H3PM012O40 or H3 PW12O40, in combination with cetylpyridinium chloride as a phase transfer agent, were shown by Ishii and coworkers [137] to be effective catalysts for alcohol oxidations with H2O2 in a biphasic, chloroform/water system. 

Methyltrioxorhenium (MTO) also catalyzes the oxidation of alcohols with H2O2 via a peroxometal pathway [137,138]. Primary benzyhc and secondary aliphatic alcohols afforded the corresponding aldehydes and ketones, respectively, albeit using two equivalents of H2O2. In the presence of bromide ion the rate was increased by a factor 1000 [137]. In this case the active oxidant could be hypobromite (HOBr), formed by MTO-catalyzed oxidation of bromide ion by H2O2. 

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Catalytic Oxidation of Alcohols with Hydrogen Peroxide 1177... 

CATALYTIC OXIDATION OF ALCOHOLS WITH HYDROGEN PEROXIDE AND ALKYL HYDROPEROXIDES... 

The activity of some heterogeneous catalytic systems based on iron- and titanium-supported catalysts and hydrogen peroxide as oxidant was recently improved by utilization of MW irradiation. Thus, the MW-assisted oxidation of alcohols with hydrogen peroxide in water-acetonitrile media in the presence of various iron-, aluminum-, mixed iron/aluminum-, titanium-, and cobalt-supported (on MCM-41[26] and SBA-15 [27]) catalysts was reported recently [10b, 28], The supported iron nanoparticles (Fe-NPs) were prepared from a suspension of iron(II) chloride in ethanol under MW [28a], The preparation of Fe/Al-MCM-41 was similar, but with the use of the Al-derived support. The Ti- B-MCM-41 catalyst was prepared from... 

Oxidation and Bromination of Alcohols. Although the oxidation of alcohols by hydrogen peroxide alone is negligible, catalytic amounts of bromide ions greatly enhance the rate of MTO-catalyzed oxidation of alcohols with hydrogen peroxide. Interestingly, a secondary alcohol has been selectively oxidized in the presence of a primary alcohol (eq 24). ... 

Farsani MR, YadoUahi B. Synthesis, characterization and catalytic performance of a Fe polyoxometalate/silica composite in the oxidation of alcohols with hydrogen peroxide. J Mol Catal A Chem. 2014 392 8-15. 

Also, oxidation of primary and secondary alcohols with hydrogen peroxide in the presence of catalytic amounts of MTO and NaBr in [bmim][BF ] has been reported by Sain and coworkers [4]. The results obtained from ionic liquid as solvent were better than those obtained from some organic solvents (Scheme 14.4). 

The oxidation of cyclohexene using hydrogen peroxide was chosen as a test reaction for the catalytic evaluation of the titanium modified hexagonal NaY sanq)les. Scheme I illustrates some of the typical products of cyclohexene oxidation. The epoxide and the diol which is a hydrolysis product of the epoxide, generally reflect a concerted process. In contrast the allylic alcohol and ketone are often ascribed to an autoxidation or radical process. We anticipated that some homolytic decomposition of the peroxide may be observed with these acidic zeolites. In fact, there was -74% conversion of H2O2 over calcined hexagonal NaY after heating at 55 C for 24 hours. This resulted in only a 1% conversion of... 

Catalytic systems based on gold clusters confined within mesoporous silica were used for oxidation of primary and secondary alcohols with hydrogen peroxide in aqueous media in the presence of a base under MW irradiation, giving mainly the corresponding ketones and/or aldehydes and/or carboxylic acids (Scheme 18.13, Table 18.9) [30]. 

Tetrabutylammonium decatungstate(VI) was reported to possess a catalytic activity in the oxidation of selected alcohols with hydrogen peroxide as oxidant, in 1,2-dichloroethane/water or acetonitrile/water solvent systems. A pronounced accelerating effect on the reaction rate was observed when a MW conditions were used. ... 

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