Oxidation of aldehydes using silica-supported Co(II)-substituted heteropolyacid

Selective oxidation of aldehydes by oxygen over macroporous alkaline resin

In this reaction, the oxidation of aldehydes is selectively catalyzed by basic resin D201-OH for the first time. Moreover, mild and high-yield oxidation of aldehydes can be achieved without any cocatalyst.

A biocatalytic method for the chemoselective aerobic oxidation of aldehydes to carboxylic acids

Herein, we present a study on the oxidation of aldehydes to carboxylic acids using three recombinant aldehyde dehydrogenases (ALDHs). The ALDHs were used in purified form with a nicotinamide oxidase (NOx), which recycles the catalytic NAD+ at the expense of dioxygen (air at atmospheric pressure). The reaction was studied also with lyophilised whole cell as well as resting cell biocatalysts for more convenient practical application. The optimised biocatalytic oxidation runs in phosphate buffer at pH 8.5 and at 40 °C. From a set of sixty-one aliphatic, aryl-aliphatic, benzylic, hetero-aromatic and bicyclic aldehydes, fifty were converted with elevated yield (up to >99%). The exceptions were a few ortho-substituted benzaldehydes, bicyclic heteroaromatic aldehydes and 2-phenylpropanal. In all cases, the expected carboxylic acid was shown to be the only product (>99% chemoselectivity). Other oxidisable functionalities within the same molecule (e.g. hydroxyl, alkene, and heteroaromatic nitrogen or sulphur atoms) remained untouched. The reaction was scaled for the oxidation of 5-(hydroxymethyl)furfural (2 g), a bio-based starting material, to afford 5-(hydroxymethyl)furoic acid in 61% isolated yield. The new biocatalytic method avoids the use of toxic or unsafe oxidants, strong acids or bases, or undesired solvents. It shows applicability across a wide range of substrates, and retains perfect chemoselectivity. Alternative oxidisable groups were not converted, and other classical side-reactions (e.g. halogenation of unsaturated functionalities, Dakin-type oxidation) did not occur. In comparison to other established enzymatic methods such as the use of oxidases (where the concomitant oxidation of alcohols and aldehydes is common), ALDHs offer greatly improved selectivity.

Heterogenization of heteropoly compounds: a review of their structure and synthesis

The heterogenization of different types of heteropoly compoundsviasix popular methods from those published over the past recent 15 years is reviewed.

Highly efficient conversion of aldehydes to carboxylic acid in the presence of platinum porphyrin sensitizers, air and sunlight

A variety of aromatic and aliphatic aldehydes were oxidized to the corresponding carboxylic acids in the presence of platinum porphyrin, sunlight and air in acetonitrile solvent under mild conditions. Nitrobenzaldehydes were found to be very efficient 1O2 scavengers that quench the formation of acids from any aldehyde in the presence of free-base porphyrin sensitizers. However, nitrobenzaldehydes were converted to the corresponding acids in the presence of platinum porphyrins. The platinum porphyrins are very good and efficient catalysts for a wide range of applications in the aerobic conversion of aldehydes to acids.

Improved oxygen reduction cathodes using polyoxometalate cocatalysts

We report on the influence of a series of transition-metal-substituted Wells-Dawson (P2W17MnO62(12-n)-; M = WVI, FeII, CoII, RuII) and Keggin (PW12O40(3-) and PCoW11O39(5-) anions on the oxygen reduction reaction (ORR) at Au, Pd, and Pt. Wells-Dawson POMs adsorbed on Au lead to large positive shifts of the ORR potential. The magnitude of the shift depends on the transition metal and is explained using a simple thermodynamic model. The best cathode performance was achieved using a PCoW11O39(5-) cocatalyst and a Pt cathode. The +54 mV positive shift in the ORR potential that we observed is comparable to the performance of the best-known bimetallic catalysts.

Photo-Oxidation of Aldehydes with Molecular Oxygen in the Presence of Catalytic Bromine or Hydrobromic Acid

Aldehydes were found to be oxidized with molecular oxygen to the corresponding carboxylic acid in the presence of catalytic hydrobromic acid or bromine under photo-irradiation.

[γ-1,2-H2SiV2W10O40] Immobilized on Surface-Modified SiO2 as a Heterogeneous Catalyst for Liquid-Phase Oxidation with H2O2

An organic-inorganic hybrid support has been synthesized by covalently anchoring an N-octyldihydroimidazolium cation fragment onto SiO2 (denoted as 1-SiO2). This modified support was characterized by solid-state 13C, 29Si, and 31P NMR spectroscopy, IR spectroscopy, and elemental analysis. The results showed that the structure of the dihydroimidazolium skeleton is preserved on the surface of SiO2. The modified support can act as a good anion exchanger, which allows the catalytically active polyoxometalate anion [gamma-1,2-H2SiV2W10O40]4- (I) to be immobilized onto the support by a stoichiometric anion exchange (denoted as I/1-SiO2). The structure of anion I is preserved after the anion exchange, as confirmed by IR and 51V NMR spectroscopy. The catalytic performance for the oxidation of olefins and sulfides, with hydrogen peroxide (only one equivalent with respect to substrate) as the sole oxidant, was investigated with I/1-SiO2. This supported catalyst shows a high stereospecificity, diastereoselectivity, regioselectivity, and a high efficiency of hydrogen peroxide utilization for the oxidation of various olefins and sulfides without any loss of the intrinsic catalytic nature of the corresponding homogeneous analogue of I (i.e., the tetra-n-butylammonium salt of I, TBA-I), although the rates decreased to about half that with TBA-I. The oxidation can be stopped immediately by removal of the solid catalyst, and vanadium and tungsten species can hardly be found in the filtrate after removal of the catalyst. These results rule out any contribution to the observed catalysis from vanadium and tungsten species that leach into the reaction solution, which means that the observed catalysis is truly heterogeneous in nature. In addition, the catalyst is reusable for both epoxidation and sulfoxidation without any loss of catalytic performance.

Sperm protein 17 is expressed in human nervous system tumours

Background

Human sperm protein 17 (Sp17) is a highly conserved protein that was originally isolated from a rabbit epididymal sperm membrane and testis membrane pellet. It has recently been included in the cancer/testis (CT) antigen family, and shown to be expressed in multiple myeloma and ovarian cancer. We investigated its immunolocalisation in specimens of nervous system (NS) malignancies, in order to establish its usefulness as a target for tumour-vaccine strategies.

Methods

The expression of Sp17 was assessed by means of a standardised immunohistochemical procedure [(mAb/antigen) MF1/Sp17] in formalin-fixed and paraffin embedded surgical specimens of NS malignancies, including 28 neuroectodermal primary tumours (6 astrocytomas, 16 glioblastoma multiforme, 5 oligodendrogliomas, and 1 ependymoma), 25 meningeal tumours, and five peripheral nerve sheath tumours (4 schwannomas, and 1 neurofibroma),.

Results

A number of neuroectodermal (21%) and meningeal tumours (4%) were found heterogeneously immunopositive for Sp17. None of the peripheral nerve sheath tumours was immunopositive for Sp17. The expression pattern was heterogeneous in all of the positive samples, and did not correlate with the degree of malignancy.

Conclusion

The frequency of expression and non-uniform cell distribution of Sp17 suggest that it cannot be used as a unique immunotherapeutic target in NS cancer. However, our results do show the immunolocalisation of Sp17 in a proportion of NS tumour cells, but not in their non-pathological counterparts. The emerging complex function of Sp17 makes further studies necessary to clarify the link between it and immunopositive cells.

Facile Aerobic Photo-Oxidation of Aldehydes in the Presence of Catalytic Lithium Bromide

Aldehydes were found to be oxidized to the corresponding carboxylic acid in the presence of catalytic lithium bromide under photo-irradiation.

Adsorption of Wells–Dawson tungsten heteropolyacid on sol–gel alumina: Structural features and thermal stability

The Wells-Dawson tungsten heteropolyacid, H6P2W18O62 supported on sol-gel and non-sol-gel alumina has been investigated by infrared spectroscopy (IR), thermal analysis (TGA/DSC), and X-ray diffraction (XRD). X-ray diffraction indicates that the heteropolyacid primary structure in bulk form holds up to 350 degrees C and by supporting it on the sol-gel alumina the thermal stability rose to 650 degrees C. UV-vis spectroscopy showed that the sol-gel alumina has a higher tendency to adsorb Wells-Dawson tungsten heteropolyacid than the non-sol-gel alumina. The heteropolyacid showed higher interaction with the sol-gel alumina than with the non-sol-gel. Esterification of propanoic acid with hexanol in the presence of alumina-supported heteropolyacid revealed that the acidic character of the heteropolyacid remains active to some extent.

Kinetics and Mechanism of the Reduction of Enneamolybdonickelate(IV) by Sulfite

The kinetics and mechanism of the reduction of enneamolybdonickelate(IV) by sulfite in acetic acid-ammonium acetate buffer solution was studied by spectrophotometry. The reaction rate law is [Formula: see text]. The rate constants and activation parameters of the rate-determining step were evaluated. A mechanism for this reaction is proposed.