2940-63-8Relevant academic research and scientific papers
IBS-catalyzed regioselective oxidation of phenols to 1,2-quinones with oxone
Uyanik, Muhammet,Mutsuga, Tatsuya,Ishihara, Kazuaki
experimental part, p. 8604 - 8616 (2012/10/07)
We have developed the first example of hypervalent iodine(V)-catalyzed regioselective oxidation of phenols to o-quinones. Various phenols could be oxidized to the corresponding o-quinones in good to excellent yields using catalytic amounts of sodium salts of 2-iodobenzenesulfonic acids (pre-IBSes) and stoichiometric amounts of Oxone as a co-oxidant under mild conditions. The reaction rate of IBS-catalyzed oxidation under nonaqueous conditions was further accelerated in the presence of an inorganic base such as potassium carbonate (K2CO3), a phase transfer catalyst such as tetrabutylammonium hydrogen sulfate (nBu4NHSO4), and a dehydrating agent such as anhydrous sodium sulfate (Na2SO4).
Self-assembly of the oxy-tyrosinase core and the fundamental components of phenolic hydroxylation
Citek, Cooper,Lyons, Christopher T.,Wasinger, Erik C.,Stack, T. Daniel P.
experimental part, p. 317 - 322 (2012/06/30)
The enzyme tyrosinase contains two CuI centres, trigonally coordinated by imidazole nitrogens of six conserved histidine residues. The enzyme activates O2 to form a μ-η2: η2-peroxo-dicopper(II) core, which hydroxylates tyrosine to a catechol in the first committed step of melanin biosynthesis. Here, we report a family of synthetic peroxo complexes, with spectroscopic and chemical features consistent with those of oxygenated tyrosinase, formed through the self-assembly of monodentate imidazole ligands, CuI and O2 at-125 °C. An extensively studied complex reproduces the enzymatic electrophilic oxidation of exogenous phenolic substrates to catechols in good stoichiometric yields. The self-assembly and subsequent reactivity support the intrinsic stability of the Cu2O2 core with imidazole ligation, in the absence of a polypeptide framework, and the innate capacity to effect hydroxylation of phenolic substrates. These observations suggest that a foundational role of the protein matrix is to facilitate expression of properties native to the core by bearing the entropic costs of assembly and precluding undesired oxidative degradation pathways.
Evaluation of the cytotoxic potential of catechols and quinones structurally related to butylated hydroxyanisole
Lam,Garg,Swanson,Pezzuto
, p. 393 - 395 (2007/10/02)
The cytotoxicity of 2- and 3-butylated hydroxyanisole (BHA) and 18 related aromatic compounds has been determined employing cultured P388 and KB cells. The phenolic compounds, 3-BHA and 2-BHA, had moderately low cytotoxic activity. Their corresponding catechols had ED50 values that were much lower than those of the parent compounds. This substantial increase in the cytotoxic activity is attributed to the presence of the catechol group, which is known to undergo one-electron oxidation readily to give the corresponding semiquinone radical. Other related catechols had similar cytotoxic activity. In general, derivatization of the catechol functionality resulted in a decrease of the cytotoxic potential of the compounds. Monoacetylation or monomethylation of the catechols gave products that were less potent cytotoxic agents than the parent compounds. Further loss of activity was observed when both hydroxy groups of the catechol function were blocked. Substitution of a methoxy group in place of a hydrogen atom in these compounds resulted in a significant increase of cytotoxicity, whereas the replacement of a methoxy group with a methyl group reduced the cytotoxicity. The catechols and quinones derived from 2-BHA were more active when compared with those derived from 3-BHA. The t-butyl group adjacent to the catechol or quinone moiety in the 3-BHA derivatives appeared to exert a significant steric effect toward the cytotoxic potential of these compounds. These results suggest the potential use of o-quinones and catechols as cytotoxic and antitumor agents.
Studies on the Antioxidants. XX. The Effect of Butylated Hydroxytoluene on tert-Butylhydroperoxide-Induced Oxidation of Butylated Hydroxyanisole
Kurechi, Tsutao,Kato, Tetsuta
, p. 1772 - 1776 (2007/10/02)
Hydrogen donation from butylated hydroxyanisole (BHA) and/or butylated hydroxytoluene (BHT) to the peroxyl radical prepared by cobalt-catalyzed cleavage of tert-butylhydroperoxide was investigated, and the relation of this process to synergism in the antioxidative effect was discussed.BHA initially donated a hydrogen to the peroxyl radical to form its phenoxyl radical to form its phenoxyl radical, and this radical reacted with either the peroxyl radical or another phenoxyl radical to form its adduct.In the combination of BHA and BHT, BHA donated a hydrogen to the peroxyl radical initially, and its phenoxyl radical accepted hydrogen from BHT to regenerate BHA, with enhanced oxidation of BHT to quinone methide.This hydrogen acceptance of the phenoxyl radical of BHA from BHT may be closely correlated with the synergism in the antioxidative effect of the mixture of BHA and BHT.
