30876-55-2Relevant articles and documents
RUTHENIUM-CATALYZED OXIDATION OF PHENOLS WITH HYDROGEN PEROXIDE
Ito, Satoru,Aihara, Kazuhisa,Matsumoto, Masakatsu
, p. 5249 - 5252 (1983)
RuCl3 catalyzed the oxidation of trimethylphenol with 30percent H2O2 in acidic medium to give the corresponding p-bezoquinone in high yield.
Bromination of tocopherols: Oxidative halogenations and rearrangements
Boehmdorfer, Stefan,Patel, Anjan,Hofinger, Andreas,Netscher, Thomas,Gille, Lars,Rosenau, Thomas
experimental part, p. 3036 - 3049 (2011/06/28)
The bromination behaviour of all four tocopherols and the corresponding model compounds in acidic and basic aqueous media was studied. Acidic conditions resulted in quinones and brominated quinones, with the bromination of the tocopherol preceeding the oxidation to the quinone. Buffer type and concentration did not influence the reaction results, whereas pH and the ratio of buffer and ethanol used as a co-solvent strongly affected the reaction rates. In alkaline media, two or three major products and a multitude of minor byproducts were obtained, because the combination of oxidizing hypobromite and alkaline conditions allowed for more complex reaction pathways (oxidation, substitution, condensation, elimination than the acidic conditions did. The para-quinones were major reaction products observed for all four tocopherols. Interestingly, if the quinone was substituted at C-5, it rearranged in a Michael-type addition process followed by substitution with a bromonium ion. The absence of a substituent at C-5, the presence of a bromine atom at C-7, or the absence of bromine in the reaction medium were all able to prevent this reaction. The rearrangement products could react further by substitution of the newly acquired bromine group for a hydroxy group. In the cases of γ- and δ-tocopherol, further rearrangement led to the formation of trioxo compounds. Bromination of all four tocopherols under alkaline conditions was compared, and the products were characterized to provide standard compounds for study of the interplay of tocopherols with halogenativeenzymes. Brominated para-quinones and rearrangement products were the major products. A "reactivity pairing" between α- and β-tocopherol on one hand and γ- and δ-tocopherol on the other was observed.
Investigation into phenoxonium cations produced during the electrochemical oxidation of chroman-6-ol and dihydrobenzofuran-5-ol substituted compounds
Hong, Mei Peng,Webster, Richard D.
, p. 2169 - 2175 (2008/09/19)
(Chemical Equation Presented) A series of chroman-6-ol and dihydrobenzofuran-5-ol based compounds with structures similar to vitamin E were examined by cyclic voltammetry and controlled potential electrolysis. The compounds displayed characteristic voltammetric features that enabled their electrochemical behavior to be interpreted in relation to the oxidation mechanism for vitamin E. The electrochemical experiments indicated the presence of several oxidized species: cation radicals, phenoxyl radicals, phenoxonium ions, hemiketals, and p-quinones, whose lifetimes varied depending on the extent of methylation of the aromatic ring (R1, R2, R3) and the nature of substituents R4 and R5.
Novel tocopheryl compounds XXV: synthesis and comparison of the para-quinones of all four homologous tocopherol model compounds and their 3,4-dehydro derivatives
Patel, Anjan,Netscher, Thomas,Gille, Lars,Mereiter, Kurt,Rosenau, Thomas
, p. 5312 - 5318 (2008/02/01)
Four tocopherol model compounds, the chroman-6-ols (1-4) having the typical substitution pattern of α-, β-, γ-, and δ-tocopherol (vitamin E), were oxidized to the corresponding para-quinones (5-8), and dehydrogenated to the 2H-chromen-6-ols (17-20) involving initial acetyl protection of the phenolic OH and deprotection as the last step. The chromenols were also converted into the para-quinones (21-24), which existed in the bicyclic hemiketal form, in contrast to the chromanol-derived, monocyclic quinones 5-8, the ketalization behavior agreeing well with computations on the DFT level.
Reaction of 2,2,5,7,8-pentamethyl-6-chromanol, an α-tocopherol analogue, with NO in the presence of oxygen
Nagata, Yoshiko,Nishio, Tamamo,Matsumoto, Shigenobu,Kanazawa, Hideko,Mochizuki, Masataka,Matsushima, Yoshikazu
, p. 2709 - 2712 (2007/10/03)
An α-tocopherol model compound, 2,2,5,7,8-pentamethyl-6-chromanol, reacted with nitric oxide (NO) in the presence of various amounts of oxygen to afford four major products. Distribution of the products was varied depending on the ratio of NO and O2
Reactions of a Hydroperoxide, 8a-Hydroperoxy-2,2,5,7,8-pentamethylchroman-6(8aH)-one, Derived from a Vitamine E Model Compound: Dimerization and X-Ray Crystal Structure
Matsumoto, Shigenobu,Matsuo, Mitsuyoshi,Iitaka, Yoichi
, p. 601 - 641 (2007/10/02)
A hydroperoxide, 8a-hydroperoxy-2,2,5,7,8-pentamethylchroman-6(8aH)-one, was obtained from the reaction of a vitamin E model compound, 2,2,5,7,8-pentamethylchroman-6-ol, with singlet oxygen, and was dimerized in toluene in the presence of lead tetraacetate to give bis(2,2,5,7,8-pentamethyl-6-oxo-6,8a-dihydrochroman-8a-yl) peroxide.The structures of the hydroperoxide and peroxide were confirmed by X-ray crystallographic analysis, and their properties were examined.
Oxygenations of Vitamin E (α-Tocopherol) and Its Model Compound 2,2,5,7,8-Pentamethylchroman-6-ol in the Presence of the Superoxide Radical Solubilized in Aprotic Solvents: Unique Epoxidations and Recyclizations
Matsuo, Mitsuyoshi,Matsumoto, Shigenobu
, p. 3514 - 3520 (2007/10/02)
Vitamin E (1a, α-tocopherol) and its model compound 2,2,5,7,8-pentamethylchroman-6-ol (1b) were oxygenated in aprotic solvents in the presence of the solubilized superoxide radical under an oxygen atmosphere to give diepoxides 2a and 2b as main products, respectively.The reactions proceeded only slighty under anaerobic conditions.Extensive product analysis was carried out on the oxygenation of 1b, revealing that it gave rise to the products 2b, 3b, 4b, 5b, 6b and 7b.The novel compounds were determined to be 4a,5;7,8-diepoxy-4a,7,8,8a-tetrahydro-8a-hydroxy-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)chroman-6(5H)-one (2a), 4a,5;7,8- diepoxy-4a,7,8,8a-tetrahydro 8a-hydroxy-2,2,5,7,8-pentamethylchroman-6(5H)-one (2b), 1,1-dimethyl-3-(2,3-epoxy-2,3,5-trimethylbenzoquinon-6-yl)propanol (5b), 6-acetyl-7,8-epoxy-6-hydroxy-2,2,7,8-tetramethyl-1-oxaspirononan-9-one (6b), and 6-acetyl-6-hydroxy-2,2,7,8-tetramethyl-1-oxaspironon-7-en-9-one (7b); the previously suggested structures of 6b and 7b should be revised.Compounds 6b and 7b are unique spiro compounds containing two five-membered rings..The structures 2b, 5b, and 6b were confirmed by X-ray crystallography.The reactions are suggested to be superoxide-catalyzed oxygenations, being characteristic of epoxidations and recyclizations, in which hydroperoxides 9a and 9b may be key intermediates.Possible reaction pathways for the formation of the products are discussed.
