Catechols catalytic oxidative

Fukuzumi and co-workers described spectroscopic evidence for a ix-rf- ] -peroxo-(Cu )2 species stabilized with a fcidentate nitrogen ligand, but no (catalytic) oxidation behavior towards catechol was noted (a related trinu-clear copper species converted 2,4-di-ferf-butylphenol stoichiometrically towards the biphenol derivative) [224], Stack et al. have described a similar ] -peroxo-(Cu )2 species (28, vide supra) that could be considered a structural and functional model for tyrosinase-activity, as it efficiently reacted with catechol, benzyl alcohol and benzylamine to yield quinone (95%), benzaldehyde (80%) and benzonitrile (70%) [172,173]. This dinuclear per-0X0 species is generated by association of two monomeric copper centers, in contrast to the systems based on dinucleating Ugand scaffolds described above. 

A number of copper) I) and copper) 11) complexes with [22]py4pz and [22]pr4pz have been isolated and structurally characterized [47—49]. Their structural and catalytic properties, as well as studies on the mechanism of the catalytic oxidation of catechol performed by some of these compounds, are discussed below. 

The complexes obtained can be considered as structural models of two states of catechol oxidase the native met state and the reduced deoocy state. In order to investigate whether the dicopper(II) complex also possesses the functionality of the natural enzyme, for example, if it can perform the catalytic oxidation of cate-... 

L.G., and Johansson, G. (1981) Catalytic-oxidation of reduced nicotonamide adenine-dinucleotide by graphite electrodes modified with adsorbed aromatics containing catechol functionalities. Analytical Chemistry, 53 (13). 1979-1982. 

Jaegfeldt, H., Kuwana, T., Johansson, G., Electrochemical Stability of Catechols with a Pyrene Side Chain Strongly Adsorbed on Graphite Electrodes for Catalytic Oxidation of Dihydronicotinamide Adenine Dinucleotide , J. Am. Chem. Soc. 105 (1983) 1805-1814. 

Scheme 17. Pathways of the catalytic oxidations of catechols at dicopper(II) centers. Inhibition at high substrate concentration is also shown.

A second copper-enzyme which has demonstrated large potential in the catalytic oxidation of alcohols is laccase (15). This blue-copper, one-electron transfer, enzyme requires mediators to extend its catalytic action. Significant progress in its use has been made in the last five years and an overview thereof will be given as well. Finally the class of dinuclear-copper oxidases, catechol oxidases and tyrosinases, and mimics thereof, have shown to be of limited use in the oxidation of aliphatic and aromatic alcohols. Their potential lies in the oxidation of ort/io-diphenols to the corresponding... 

Mimmi MC, Gullotti M, Santagostini L (2004) Models for biological trinuclear copper clusters. Characterization and enantioselective catalytic oxidation of catechols by the cop-per(I) complexes of a chiral ligand derived from (5)-(—)-l,l binaphthyl-2,2 -diamine. Dalton Trans 2192-2201... 

Similar TS-1 films have been applied for phenol hydroxyl-ation reaction to dihydroxybenzenes (hydroquinone and catechol) [354] and catalytic oxidation of styrene to benzaldehyde and phenylacetaldehyde [355] with hydrogen peroxide as oxidant in batch-type membrane reactors. The dihydroxybenzenes and phenylacetaldehyde selectivity values increased with in-framework Ti content. In order to reduce the TS-1 membrane costs, Chen et al. [356] have successMly synthesized TS-1 on mullite tubes by replacing TPAOH with TPABr/EtjNH system (4% of the initial cost). The catalytic activity was tested in the probe reaction of isopropyl alcohol oxidation with hydrogen peroxide under pervaporation condition at 60°C. In general, future work on TS-1 film catalysts is required to improve mass transfer resistances and reaction conversion without compromising selectivity. 

Catalytic oxidative cleavage of catechols 6.3.1. Base catalyzed oxidations... 

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