- Selective inhibition of bovine plasma amine oxidase by homopropargylamine, a new inactivator motif
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Propargylic and activated allylic amines are known to inactivate the quinone-dependent plasma amine oxidases, possibly through active-site modification by the α,β-unsaturated aldehyde turnover products. Although homopropargylamine (1-amino-3-butyne, 1) is a nonobvious candidate as a mechanism-based inhibitor, 1 was found to be an unusually potent time- and concentration-dependent irreversible inactivator of bovine plasma amine oxidase (BPAO), exhibiting a 30 min IC50 of 2.9 μM at 30 °C ([BPAO] = 1.2 μM). Preserved cofactor redox activity of the denatured inactivated enzyme indicates that inactivation by 1 involves either a cofactor modification that reverses upon enzyme denaturation or a modification of an active-site residue. Because inactivation by 1 may involve enzyme alkylation by the reactive 2,3-butadienal (3) tautomer of the 3-butynal turnover product of 1, aldehyde 3 was prepared and was found to inactivate BPAO, but only at high concentration. In addition, whereas inhibition by 3 was blunted by the presence of mercaptoethanol, no such protection was observed against 1. The amine whose turnover should lead directly to 3 was prepared (1-amino-2,3-butadiene, 4) and was found to be an even more potent inactivator of BPAO than 1, exhibiting a 5 min IC50 of 1.25 μM. Rat liver mitochondrial monoamine oxidase was also inactivated by 4, as expected, but only very weakly by 1. Potential mechanisms explaining the selective inhibition of BPAO by 1 are discussed.
- Qiao, Chunhua,Jeon, Heung-Bae,Sayre, Lawrence M.
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- Substituent effects on the benzene ring. Determination of the intramolecular interactions of substituents in tert-alkyl-substituted catechols from thermochemical measurements
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Chemical equilibria of reactions of transalkylation among tert-butylphenols and tert-butylcatechols in the liquid phase were investigated in the temperature range 373-483 K. The molar enthalpies of fusion ΔcrlH°m of the catechol, 4-tert-butylcatechol, and 3,5-di-tert-butylcatechol were measured by DSC. The standard (p° = 0.1 MPa) molar enthalpies of formation ΔfH°m (cr) at the temperature T = 298.15 K were measured by means of combustion calorimetry for 4-tert-butylcatechol and 3,5-di-tert-butylcatechol. The standard molar enthalpies of sublimation of these compounds, and also the enthalpy of vaporization of 3-tert-butylcatechol, were obtained from the temperature dependence of the vapor pressure measured by the transpiration method. The measured reaction enthalpies were utilized for reconciliation of calorimetrically derived standard molar enthalpies of formation of tert-butyl-substituted phenols and catechols, as a stringent test of thermodynamic consistency of results derived from the diverse techniques employed in this work. Resulting values of ΔfH°m(g) of tert-butylcatechols were obtained at the temperature T = 298.15 K and used to derive their strain enthalpies. The intramolecular interactions of the substituents were discussed in terms of deviations of ΔfH°m(g) from the group additivity rules. No peculiarities in the interaction energy among alkyl groups and the hydroxyl groups in the ortho-, para-, and meta-positions of alkylcatechols in comparison with those of alkyl-substituted phenols were detected. Thus, no new parameters are needed for the prediction of the ΔfH°m(g) values of alkylcatechols by using the group-additive procedure.
- Verevkin, Sergey P.,Schick, Christoph
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- Tyrosinase and catecholase-like activities of a dinuclear Cu(II) complex
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A dinuclear Cu(II) complex was synthesized and crystallographically characterized. The compound was found to have antiferromagnetic interaction in between the Cu(II) centres in the molecule. It had weak intermolecular ferromagnetic interaction. The compound was found to be tyrosinase and catecholase active. In case of tyrosinase activity, the diphenol formed was isolated using thin layer chromatography (TLC) and characterized through 1H NMR as well as mass spectrometry. The o-quinone derivative formed in this reaction was characterized using GC–MS. The latter activity was monitored spectrophotometrically and the product o-quinone derivative was isolated (in MeOH and MeCN) column chromatographically and characterized using melting point determination. These were followed by Michealis–Menten kinetics with turnover numbers 4.95 × 103 and 1.58 × 103 h?1 in MeOH and MeCN, respectively.
- Chatterjee, Arnab,Yadav, Hare Ram,Choudhury, Angshuman Roy,Ali, Anzar,Singh, Yogesh,Ghosh, Rajarshi
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- Three-way cooperativity in d8 metal complexes with ligands displaying chemical and redox non-innocence
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Reversible proton- and electron-transfer steps are crucial for various chemical transformations. The electron-reservoir behavior of redox non-innocent ligands and the proton-reservoir behavior of chemically non-innocent ligands can be cooperatively utilized for substrate bond activation. Although site-decoupled proton- and electron-transfer steps are often found in enzymatic systems, generating model metal complexes with these properties remains challenging. To tackle this issue, we present herein complexes [(cod-H)M(μ-L2-)M(cod-H)] (M=PtII, [1] or PdII, [2], cod=1,5-cyclooctadiene, H2L=2,5-di-[2,6-(diisopropyl)anilino]-1,4-benzoquinone), in which cod acts as a proton reservoir, and L2- as an electron reservoir. Protonation of [2] leads to an unusual tetranuclear complex. However, [1] can be stepwise reversibly protonated with up to two protons on the cod-H ligands, and the protonated forms can be stepwise reversibly reduced with up to two electrons on the L2- ligand. The doubly protonated form of [1] is also shown to react with OMe- leading to an activation of the cod ligands. The site-decoupled proton and electron reservoir sources work in tandem in a three-way cooperative process that results in the transfer of two electrons and two protons to a substrate leading to its double reduction and protonation. These results will possibly provide new insights into developing catalysts for multiple proton- and electron-transfer reactions by using metal complexes of non-innocent ligands.
- Deibel, Naina,Hohloch, Stephan,Schweinfurth, David,Weisser, Fritz,Grupp, Anita,Sarkar, Biprajit
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- SEMI-HINDERED PHENOLS. 1. SYNTHESIS OF 3,5-DI-TERT-BUTYLSALICYLIC ALDEHYDE
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Some differences were observed in the solid- and liquid-phase benzylic oxidation of 2-(hydroxy- or dialkylamino)methyl-4,6-di-tert-butylphenols.Oxidation of these semi-hindered phenols with lead tetraacetate gave a new compound: 3,5-di-tert-butyl-ortho-benzoquinone diacylal.Keywords: semi-hindered phenols, synthesis, aldehyde, benzylic alcohol, oxidation, liquid phase, solid phase.
- Dokukina, M. A.,Vol'eva, V. B.,Belostotskaya, I. S.,Komissarova, N. L.,Karmilov, A. Yu.,Ershov, V. V.
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- Bioinspired copper(I) complexes that exhibit monooxygenase and catechol dioxygenase activity
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New tripodal ligand L2 featuring three different pyridyl/imidazolyl-based N-donor units at a bridgehead C atom, from which one of the imidazolyl units is separated by a phenylene linker, was synthesized and investigated with regards to copper(I) complexation. The resulting complex [(L2)Cu]OTf (2OTf), the known complex [(L1)Cu]OTf (1OTf; L1 differs from L2 in that it lacks the phenylene spacer) and [(L3)Cu]OTf (3OTf), prepared from a known chiral, tripodal, N-donor ligand featuring pyridyl, pyrazolyl, and imidazolyl donors, were tested as catalysts for the oxidation of sodium 2,4-di-tert-butylphenolate (NaDTBP) with O2. Indeed, they mediated NaDTBP oxidation to give mainly the corresponding catecholate and quinone (Q). None of the complexes 1OTf, 2OTf, and 3OTf is superior to the others, as yields were comparable and, if the presence of protons is guaranteed by concomitant addition of the phenol DTBP, the oxidation can also be performed catalytically. For all complexes stoichiometric oxidations under certain conditions (concentrated solutions, high NaDTBP content) were found to also generate products typical for metal-mediated intradiol cleavage of the catecholate with O2. As shown representatively for 1OTf this dioxygenation sets in at a later stage of the reaction. Initially a copper species responsible for the monooxygenation must form from 1OTf/NaDTBP/O2, and only thereafter is the copper species responsible for dioxygenation formed and consumes Q as substrate. Hence, under these circumstances complexes 1OTf-3OTf show both monooxygenase and catechol dioxygenase activity.
- Arnold, Aline,Metzinger, Ramona,Limberg, Christian
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- Reaction of 1,1-Bis(Diphenylphosphino)Methane with O-Quinones and Naphtho[2,1-B]Furan-1,2-Dione. Novel Synthesis of Bis(Diphenylphosphoryl) Derivatives and their Antimicrobial Activity
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The reaction of 1,1-bis(diphenylphosphino)methane with substituted o-quinones afforded the novel 6-[bis(diphenylphosphoryl)methyl]-and 6-bis(diphenyl phosphoryl)methylidene derivatives. Moreover, 1,1-bis(diphenylphosphino)methane reacts with 3,4,5,6-tetrabromo-o-benzoquinone to give only the new 6-[bis(diphenylphosphoryl)methyl] derivative. Mechanisms accounting for the formation of the new products are discussed. The antimicrobial activity of some of the newly synthesized compounds was also examined.
- Boulos, Leila S.,Ewies, Ewies F.,Ibrahim, Nabila M.,Mohram, Maysa E.
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- ORTHO-HYDROXYLATION SELECTIVE DES PHENOLS : I - VERS UN MODELE CHIMIQUE SIMPLE DES TYROSINASES.
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The oxidation of cuprous phenoxides by molecular oxygen gives rise to catechols and ortho-benzoquinones.Such a new reaction provides a mechanistic approach to tyrosinase catalyzed oxidation of phenols.
- Capdevielle, Patrice,Maumy, Michel
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- Etude comparative des reactions par transfert monoelectronique entre les germylamines primaires, secondaires et tertiaires et la 3,5-di-tert-butylorthoquinone
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Several germylamines were treated with 3,5-di-t-butylorthoquinone (1).Competitive 1,2 and 1,4 additions resulted using the tertiary amine Et3GeNPh2.The thermally unstable 1,4 adduct gives 2,2-dialkyl-4,5-(6,8-di-t-butyl)benzo-2-germa-1,3-dioxolanne.The 1,2 adduct leads via intermolecular redistribution to bis(triethylgermyl)oxide ((Et3Ge)2O), and aminal with partial regeneration of the initial quinone.These reations seem to proceed solely via a mono-electron transfer mechanism; the aminyl radical Ph2N and the transitory o-semiquinonic germylated radical formed in the reaction have been characterized by ESR spectroscopy.The o-semiquinonic radical then gives O-germyl-3,5-di-t-butylcatechol by hydrogen abstraction.As ethylene and isobutene have been characterized, these hydrogen abstractions occur from ethyl groups linked to germanium and from t-butyl groups belonging to the organic moieties.In the reaction of the secondary amine Et3GeN(H)Ph, a germylaminyl radical is mainly formed instead of an o-semiquinonic germylated radical, which can explain the lesser amount of germadioxolanne obtained.The quinone 1 is partially transformed in o-diphenol under the action of Mes3GeNH2.No germylated adducts are observed.Aminyl radicals characterized in several reactions between germylamines and 1 were also obtained via monoelectronic transfer between lithium amids and tri-t-butylnitrozobenzene (BNB), thus providing a new, useful method for obtaining such species.
- Riviere-Baudet, Monique,Morere, Alain,Khallaayoun, Abdelhay
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- Solid-Phase ortho-Hydroxylation of 2,4-Di-tert-butylphenol and Its Derivatives
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Abstract: Direct phenol–catechol conversion has been realized as a result of the solid-phase reaction of 2,4-di-tert-butylphenol with cuprous oxide under high pressure and shear deformation on the Bridgman anvils. The yield of 3,5-di-tert-butylcatechol in this reaction was about 85%. When cupric oxide was used in the solid-phase process, oxidative coupling of the starting phenol took place, resulting in quantitative formation of tetra-tert-butyl-ortho-bisphenol. The reaction of 6-substituted derivatives of 2,4-di-tert-butylphenol with cuprous oxide was used as an example to demonstrate the possibility of substitutive ortho-hydroxylation yielding 7–20% of pyrocatechols.
- Kurkovskaya, L. N.,Ovsyannikova, M. N.,Vol’eva, V. B.,Zhorin, V. A.
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- Dual oxidase/oxygenase reactivity and resonance Raman spectra of {Cu3O2} moiety with perfluoro-: T -butoxide ligands
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A Cu(i) fully fluorinated O-donor monodentate alkoxide complex, K[Cu(OC4F9)2], was previously shown to form a trinuclear copper-dioxygen species with a {Cu3(μ3-O)2} core, TOC4F9, upon reactivity with O2 at low temperature. Herein is reported a significantly expanded kinetic and mechanistic study of TOC4F9 formation using stopped-flow spectroscopy. The TOC4F9 complex performs catalytic oxidase conversion of hydroquinone (H2Q) to benzoquinone (Q). TOC4F9 also demonstrated hydroxylation of 2,4-di-tert-butylphenolate (DBP) to catecholate, making TOC4F9 the first trinuclear species to perform tyrosinase (both monooxygenase and oxidase) chemistry. Resonance Raman spectra were also obtained for TOC4F9, to our knowledge, the first such spectra for any T species. The mechanism and substrate reactivity of TOC4F9 are compared to those of its bidentate counterpart, TpinF, formed from K[Cu(pinF)(PR3)]. The monodentate derivative has both faster initial formation and more diverse substrate reactivity.
- Brazeau, Sarah E. N.,Norwine, Emily E.,Hannigan, Steven F.,Orth, Nicole,Ivanovi?-Burmazovi?, Ivana,Rukser, Dieter,Biebl, Florian,Grimm-Lebsanft, Benjamin,Praedel, Gregor,Teubner, Melissa,Rübhausen, Michael,Liebh?user, Patricia,R?sener, Thomas,Stanek, Julia,Hoffmann, Alexander,Herres-Pawlis, Sonja,Doerrer, Linda H.
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- REXTION OF SUPEROXO Co(III) COMPLEX WITH QUINONES FORMATION OF A SEMIQUINONE Co(III) COMPLEX
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The superoxo complex (3-) was found to act as a reducing agent towards quinones.One-electron reduction took place with o-quinone whereas two-electrons reduction with p-quinones. 3,5-Di-t-butyl-o-benzoquinone gave the corresponding semiquinone Co(III) complex quantitatively.
- Nishinaga, A.,Tomita, H.,Matsuura, T.
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- Formation of Hybrid Guanidine-Stabilized Bis(μ-oxo)dicopper Cores in Solution: Electronic and Steric Perturbations
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A series of new hybrid peralkylated amine-guanidine ligands based on a 1,3-propanediamine backbone and their Cu-O2 chemistry is reported. The copper(I) complexes react readily with O2 at low temperatures in aprotic solvents with weakly coordinating anions to form exclusively bis(μ-oxo)dicopper species (O). Variation of the substituents on each side of the hybrid bidentate ligand reveal that less sterically demanding amine and guanidine substituents increase not only the thermal stability of the formed O cores but also enhance inner-sphere phenolate hydroxylation pathways. TD-DFT analysis on selected guanidine-amine O species suggest that the additional visible-wavelength feature observed is a guanidine π? → Cu2O2 LMCT, which appears along with the classic oxo-σu? → CuIII and πσ? → CuIII LMCT transitions. Variation of the substituents on each side of a hybrid bidentate ligand reveals that less sterically demanding amine and guanidine substituents increase not only the thermal stability of the formed O cores but also enhance inner-sphere phenolate hydroxylation pathways.
- Herres-Pawlis, Sonja,Haase, Roxana,Verma, Pratik,Hoffmann, Alexander,Kang, Peng,Stack, T. Daniel P.
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- 1-Methyl-1,4-cyclohexadiene as a Traceless Reducing Agent for the Synthesis of Catechols and Hydroquinones
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Pro-aromatic and volatile 1-methyl-1,4-cyclohexadiene (MeCHD) was used for the first time as a valid H-atom source in an innovative method to reduce ortho or para quinones to obtain the corresponding catechols and hydroquinones in good to excellent yields. Notably, the excess of MeCHD and the toluene formed as the oxidation product can be easily removed by evaporation. In some cases, trifluoroacetic acid as a catalyst was added to obtain the desired products. The reaction proceeds in air and under mild conditions, without metal catalysts and sulfur derivatives, resulting in an excellent and competitive method to reduce quinones. The mechanism is attributed to a radical reaction triggered by a hydrogen atom transfer from MeCHD to quinones, or, in the presence of trifluoroacetic acid, to a hydride transfer process.
- Baschieri, Andrea,Amorati, Riccardo,Valgimigli, Luca,Sambri, Letizia
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- Finding a new pathway for acid-induced nitrite reduction reaction: Formation of nitric oxide with hydrogen peroxide
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Here, we report a new pathway for nitrite reduction chemistry, formation of cobalt-nitrosyl ({CoII-NO}8) with H2O2 in the reaction of a CoII-nitrito complex with a one-fold acid (H+) via the formation of a CoII-nitrous acid intermediate ({CoII-ONOH}). Mechanistic investigations using 15N-labeled-15NO2- revealed that the N-atom in the {CoII-NO}8 complex is derived from the nitrito ligand, and H2O2 came from the homolysis of the ON-OH moiety. Spectral evidence supporting the formation of the CoII-ONOH intermediate and the generation of H2O2 is also presented.
- Puthiyaveetil Yoosaf, Mohammed Ajmal,Ghosh, Somnath,Narayan, Yatheesh,Yadav, Munendra,Sahoo, Subash Chandra,Kumar, Pankaj
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- Electron transfer in complexes of BII cations with organic π-acceptors: A combined experimental and quantum-chemical study
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Due to their combined Lewis acidity and electron-donor capability, BII cations exhibit an interesting reactivity, which is almost unexplored so far. In this work, we compare the reduction in a dicationic diborane of a series of vicinal diones with different redox potentials, namely 3,5-di-tert-butylbenzoquinone, 3,4,5,6-tetrachlorobenzoquinone, 1,2-naphthalene-dione, 9,10-phenanthrene-dione, 2,2′-dichlorobenzil, benzil and 1,2-acenaphthylene-dione. The experimental work is complemented by quantum-chemical calculations, illuminating the electron-transfer step in the reactions.
- Vogler, Daniel,Wolf, Nina,Kaifer, Elisabeth,Himmel, Hans-J?rg
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- Chloroindate(iii) ionic liquids as catalysts for alkylation of phenols and catechol with alkenes
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Chloroindate(iii) ionic liquids are shown to be versatile catalysts for the alkylation of phenols with alkenes, giving high conversions to alkylated phenols with high selectivities.
- Gunaratne, H. Q. Nimal,Lotz, Tobias J.,Seddon, Kenneth R.
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- Synthesis of some [1,3]benzodioxoles via the reaction of o-quinones with phosphorus ylides
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3,5-Di(tert-butyl)benzo-1,2-quinone 1c, phenanthrene-9,10-quinone 11, and 1,2-naphthoquinone 18 react with 1-phenylethylidene(triphenyl)phosphorane 2j, cyclopentylidene(triphenyl)phosphorane 2k, cyclohexylidene(triphenyl) phosphorane 21, and tetrahydro-2-furanyl-methylidene(triphenyl)phosphorane 8 to give the corresponding 2-substituted [1,3]benzodioxoles 5-7, 10, 12-14, 20-22 in low to high yields, instead of Wittig products, with exception of 11, 12-dihydro-10H-cyclopenta[b]phenanthro[9,10-d]furan 17. A possible explanation for these reaction sequences is discussed.
- Gautam, Daman R.,Litinas, Konstantinos E.,Fylaktakidou, Konstantina C.,Nicolaides, Demetrios N.
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- Substituent effects on the photorearrangements of unsymmetrically substituted diazinobarrelenes
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A series of diazinobarrelenes 8-15 engendered with alkyl functionalities at the barrelene skeleton were irradiated with 350 nm light under direct and acetone-sensitized reaction conditions. Under these conditions, all the barrelenes except barrelene 14 afforded semibullvalenes with varying degrees of regioselectivity and product distribution. Dicyanopyrazinobarrelenes 8-10 which furnished semibullvalenes 32-41via the aryl-vinyl initial bridging route were strongly controlled by the nitrile functionalities installed at the aromatic sites. Benzoquinoxalinobarrelenes 11-13 which afforded semibullvalenes 42-49, preferentially underwent photorearrangement via vinyl-vinyl bridging even if the compounds were excited at a wavelength where the quinoxaline moiety absorbed most of the light. Zimmerman's bridging hypothesis and the possibility for quinoxalines to undergo intramolecular triplet energy transfer could reasonably account for the observed regioselectivity. Barrelene 14 was insensitive to photorearrangement whereas benzo[f,h]quinoxalinobarrelene 15 preferentially underwent ADPM rearrangement affording semibullvalenes 50-52. Electronic and steric factors of alkyl substituents overwhelmingly controlled the product forming steps whereas localization and minimization of triplet energies greatly influenced the initial bridging interaction. The Royal Society of Chemistry 2013.
- Hsieh, Hsing-Pang,Chen, Ann-Cheng,Villarante, Nelson R.,Chuang, Gary J.,Liao, Chun-Chen
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- Synthesis and properties of 11-(3,5-di-tert-butyl-2-hydroxyphenylcarbamoyl)undecanoic acid, a new amphiphilic antioxidant
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Based on the membrane addressing concept, designing and synthesis of 11-(3,5-di-tert-butyl-2-hydroxyphenylcarbamoyl)undecanoic acid have been carried out. Antioxidant properties of the prepared compound were investigated in comparison with its non-amphiphilic analogues.
- Lodyato, Vladimir I.,Yurkova, Irina L.,Sorokin, Viktor L.,Shadyro, Oleg I.,Dolgopalets, Vladimir I.,Kisel, Mikhail A.
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- Metal-free reduction of unsaturated carbonyls, quinones, and pyridinium salts with tetrahydroxydiboron/water
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A series of unsaturated carbonyls, quinones, and pyridinium salts have been effectively reduced to the corresponding saturated carbonyls, dihydroxybenzenes, and hydropyridines in moderate to high yields with tetrahydroxydiboron/water as a mild, convenient, and metal-free reduction system. Deuterium-labeling experiments have revealed this protocol to be an exclusive transfer hydrogenation process from water. This journal is
- Li, Tiejun,Peng, Henian,Tang, Wenjun,Tian, Duanshuai,Xu, Guangqing,Yang, He
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p. 4327 - 4337
(2021/05/31)
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- Highly selective conversion of guaiacol to: Tert -butylphenols in supercritical ethanol over a H2WO4 catalyst
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The conversion of guaiacol is examined at 300 °C in supercritical ethanol over a H2WO4 catalyst. Guaiacol is consumed completely, meanwhile, 16.7% aromatic ethers and 80.0% alkylphenols are obtained. Interestingly, tert-butylphenols are produced mainly with a high selectivity of 71.8%, and the overall selectivity of 2,6-di-tert-butylphenol and 2,6-di-tert-butyl-4-ethylphenol is as high as 63.7%. The experimental results indicate that catechol and 2-ethoxyphenol are the intermediates. Meanwhile, the WO3 sites play an important role in the conversion of guaiacol and the Br?nsted acid sites on H2WO4 enhance the conversion and favour a high selectivity of the tert-butylphenols. The recycling tests show that the carbon deposition on the catalyst surface, the dehydration and partial reduction of the catalyst itself are responsible for the decay of the H2WO4 catalyst. Finally, the possible reaction pathways proposed involve the transetherification process and the alkylation process during guaiacol conversion.
- Mai, Fuhang,Cui, Kai,Wen, Zhe,Wu, Kai,Yan, Fei,Chen, Mengmeng,Chen, Hong,Li, Yongdan
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p. 2764 - 2771
(2019/02/01)
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- Synthesis of ortho-Azophenols by Formal Dehydrogenative Coupling of Phenols and Hydrazines or Hydrazides
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Azophenols are important chromophores and reagents in organic synthesis, with applications as pigments and molecular switches. Here, we describe a catalytic aerobic process that couples phenols and hydrazines or hydrazides for their synthesis. The key aromatic C?N bond is formed by condensation between the hydrazine or hydrazide and an ortho-quinone, which triggers a redox-isomerization to install the azo-functionality. Notable features include rapid access to highly functionalized azophenols with a range of electronic configurations, including “push–pull” systems, conditions that employ simple, unactivated substrates, occurrence at room temperature using an earth-abundant and commercially available copper catalyst, and production of water as the only stoichiometric byproduct.
- Esguerra, Kenneth Virgel N.,Lumb, Jean-Philip
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supporting information
p. 8596 - 8600
(2017/06/30)
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- Influence of co-ligands in synthesis, photoluminescence behavior and catalytic activities of zinc complexes of 2-((E)-((pyridin-2-yl)methylimino)methyl)phenol
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Four new zinc(II) complexes of a tridentate Schiff base ligand 2-((E)-((pyridin-2-yl)methylimino)methyl)phenol (HL), namely [Zn2L2Cl2] (1); [Zn2L2Br2] (2); [ZnL(SCN)(MeOH)] (3) and [Zn2L(OAc)3(MeOH)] (4) have been synthesized with the view to investigate the role of co-ligands in controlling the structural diversity, photoluminescence property and catalytic activities. The complexes have been characterized through common physicochemical techniques as well as by X-ray single crystal structural analysis. All of them display interesting co-ligands mediated photoluminescence property the origin of which may be attributed due to ligand to metal charge transfer (LMCT) and the order of photoluminescence efficiency is 3 > 4 > 1~2. Catecholase and phosphatase activities of the complexes have been investigated in DMF medium using 3,5-di-tert-butylcatechol (3,5-DTBC) and 4-nitrophenylphosphate as substrates respectively. Co-ligands have prominent role on phosphatase activity of the complexes where the order of activity in terms of kcat value is 4 > 1 > 2 > 3. Interestingly, only complex 4 is active in catalyzing the aerobic oxidation of 3,5-DTBC. The presence of readily labile solvent molecule in one of the zinc centers of complex 4 perhaps takes the key role for initiating substrate-Zn interaction and thereby the activity. Radical pathway is the probable reason behind the catecholase activity as is evident from EPR study. Solid state thermal analysis suggests that ZnO is the thermally stable end product for complexes 1, 2 and 4, whereas it is ZnS in case of complex 3.
- Kundu, Priyanka,Chakraborty, Prateeti,Adhikary, Jaydeep,Chattopadhyay, Tanmay,Fischer, Roland C.,Mautner, Franz A.,Das, Debasis
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p. 320 - 328
(2015/02/19)
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- Tris(3,5-di-tert-butylcatecholato)molybdenum(VI): Lewis acidity and nonclassical oxygen atom transfer reactions
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In the solid state, tris(3,5-di-tert-butylcatecholato)molybdenum(VI) forms a dimer with seven-coordinate molybdenum and bridging catecholates. NMR spectroscopy indicates that the dimeric structure is retained in solution. The molybdenum center has a high affinity for Lewis bases such as pyridine or pyridine-N-oxide, forming seven-coordinate monomers with a capped octahedral geometry, as illustrated by the solid-state structure of (3,5- tBu2Cat)3Mo(py). Structural data indicate that the complexes are best considered as Mo(VI) with substantial π donation from the nonbridging catecholates to molybdenum. Both the dimeric and the monomeric tris(catecholates) react rapidly with water to form free catechol and oxomolybdenum bis(catecholate) complexes. Monooxomolybdenum complexes are also obtained, more slowly, on reaction with dioxygen, with organic products consisting mostly of 3,5-di-tert-butyl-1,2-benzoquinone with minor amounts of the extradiol oxidation product 4,6-di-tert-butyl-1-oxacyclohepta-4,6-diene-2,3- dione. The pyridine-N-oxide complex reacts on heating (with excess pyO) to form initially (3,5-tBu2Cat)2MoO(Opy) and ultimately MoO3(Opy), with quinone and free pyridine as the only organic products. The decay of (3,5-tBu2Cat)3Mo(Opy) shows an accelerated, autocatalytic profile because the oxidation of its product, (3,5-tBu2Cat)2MoO(Opy), produces an oxo-rich, catecholate-poor intermediate which rapidly conproportionates with (3,5-tBu2Cat)3Mo(Opy), providing an additional pathway for its conversion to the mono-oxo product. The tris(catecholate) fragment Mo(3,5-tBu2Cat)3 deoxygenates Opy in this nonclassical oxygen atom transfer reaction slightly less rapidly than does its oxidized product, MoO(3,5-tBu2Cat)2.
- Randolph, Amanda H.,Seewald, Nicholas J.,Rickert, Karl,Brown, Seth N.
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p. 12587 - 12598
(2013/11/19)
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- On the redox reaction of 1,2-bis(diphenylphosphino) alkanes toward o -, and p-quinones
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The reaction of 1,2-bis(diphenylphosphino)ethane with substituted o-benzo-quinones afforded new bis(6-hydroxycyclohexa-2,4-dienone) derivatives. Treatment of the same reagent with o-naphthoquinone, phenanthrenequinone, and acenaphthenequinone gave the res
- Boulos, Leila S.,Ewies, Ewies F.,Fahmy, Amin F. M.
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p. 726 - 738
(2013/07/26)
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- Synthesis and use of ortho-(branched alkoxy)-tert-butoxybenzenes
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A series of sterically hindered o-(branched alkoxy)-tert-butoxybenzenes was efficiently prepared in good yields owing to a new practical and simple preparation of o-tert-butoxyphenol starting from catechol and isobutene. Use of DMF di-tert-butyl acetal reagent instead of isobutene/H2SO 4 (cat.) for O-tert-butylation was very convenient in case of ortho bulky phenols affording the corresponding tert-butyl ethers in high yield and purity. This general route proved to be useful since no reliable access was available to o-di-t-BuO-substituted arenes. Application to the synthesis of congested phosphorus-based compounds is presented.
- Rast, Slavko,Stephan, Michel,Mohar, Barbara
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supporting information
p. 6815 - 6818
(2013/01/15)
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- Reaction of 1,3,5-tri-tert-butylbenzene with 2,4,6,8-tetraiodo- 2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-dione
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Reactions of 1,3,5-tri-tert-butylbenzene with 2,4,6,8-tetraiodo-2,4,6,8- tetraazabicyclo[3.3.0]octane-3,7-dione in acetic and trifluoroacetic acids involve substitution of one or two tert-butyl groups in the aromatic ring with formation of mono-, di-, and
- Nguen, M.,Chaikovskii, V. K.,Filimonov, V. D.,Funk, A. A.
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p. 780 - 782,3
(2020/08/31)
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- Self-assembly of the oxy-tyrosinase core and the fundamental components of phenolic hydroxylation
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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.
- Citek, Cooper,Lyons, Christopher T.,Wasinger, Erik C.,Stack, T. Daniel P.
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experimental part
p. 317 - 322
(2012/06/30)
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- Alkylation of pyrocatechol in tert-butyl alcohol-sulfuric acid-benzene
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Alkylation of pyrocatechol with tert-butyl alcohol in benzene in the presence of sulfuric acid gave 3,5-di-tert-butylbenzene-1,2-diol in a higher yield than in analogous reaction with tert-butyl alcohol. This result was rationalized by reduction of inhibitory effect of liberated water, formation of heterogeneous system, and occurrence of the alkylation process in nonpolar organic phase. Intermediate products were identified and found to undergo intra- and intermolecular tert-butyl group transfer with formation of more stable 3,5-di-tert-butylbenzene-1,2-diol. The formation of p-di-tert-butylbenzene indicated participation of benzene in crossalkylation processes. Pleiades Publishing, Ltd., 2011.
- Vol'eva,Prokof'eva,Belostotskaya,Komissarova,Gorbunov,Kurkovskaya
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experimental part
p. 1310 - 1312
(2011/12/05)
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- Nitrone cycloaddition to quinones: A novel strategy for the synthesis of benzisoxazolidenes
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(Chemical Equation Presented) 1,3-Dipolar cycloaddition reaction involving nitrones and benzoquinones resulting in the formation of benzisoxazolidene is described. As the nitrone is selectively added to carbon-carbon double bond of the benzoquinone, the quinone-nitrone reaction is considered as a special case among quinone-1,3-dipole cycloaddition reactions. Molecular orbital calculation was performed to examine the electronic effects involved in the regioselectivity of the reaction.
- Paul, Rony Rajan,Varghese, Vimal,Beneesh,Sinu,Suresh,Anabha
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scheme or table
p. 396 - 399
(2010/06/16)
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- The first catalytic tyrosinase model system based on a mononuclear copper(I) complex: Kinetics and mechanism
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Ready... steady... go! The copper(I) complex 1 not only catalyzes the oxygenation of di-tertbutylphenol (DTBP-H) to di-tert-butylquinone (DTBQ) in a tyrosinase-like fashion, but also allows the reactive cycle to be studied in a stepwise and controlled manner. This feature opens new insights into the individual stages of the tyrosinase reaction, phenol hydroxylation, and release of the product as quinone. The implications for the enzymatic reaction are discussed. Copyright
- Rolff, Malte,Schottenheim, Julia,Peters, Gerhard,Tuczek, Felix
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supporting information; experimental part
p. 6438 - 6442
(2010/11/18)
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- Efficient ortho-oxidation of phenols with diacyl peroxides
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A stable symmetric diacyl peroxide, m-chlorobenzoyl peroxide (mCBPO), and an asymmetric diacyl peroxide, chloroacetyl m-chlorobenzoyl peroxide (CAMCBPO), were synthesized from m-chloroperbenzoic acid. Both peroxides oxidized phenols selectively at the ortho position predoninantly. CAMCBPO gave para-oxidized compounds as minor products from some phenols. The improvement of the yield of ortho-oxidation of phenols with mCBPO was also reported.
- Tada, Masahiro,Ishiguro, Risa,Izumi, Ryohei
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p. 239 - 242
(2008/09/21)
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- New chiral ligands from myrtenal and caryophyllene for asymmetric oxydation of sulfides catalyzed by metal complexes
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From myrtenal and caryophyllene, widespread terpene compounds, three new chiral Schiff bases were prepared suitable for ligands in vanadium ions catalyzed sulfides oxidation to chiral sulfoxides.
- Khomenko,Salomatina,Kurbakova,Il'ina,Volcho,Komarova,Korchagina,Salakhutdinov,Tolstikov
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p. 1653 - 1661
(2007/10/03)
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- ALKYLATION OF HYDROXYARENES WITH OLEFINS, ALCOHOLS AND ETHERS IN IONIC LIQUIDS
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Hydroxyarenes are alkylated using an ionic liquid catalyst system with olefins, alcohols, or ethers as alkylating agents. The ionic liquid catalyst system comprises chloroindate (III) anions. The reactions may be conducted at moderate temperatures and pressures to yield commercially relevant alkylated hydroxyarene compounds.
- -
-
Page/Page column 25-26
(2008/06/13)
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- o-benzoquinone photoreduction products in the presence of N,N-dimethylanilines
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Photoreduction of o-benzoquinones in the presence of para-substituted N,N-dimethyl-anilines under irradiation at λ ≥ 500 nm affords pyrocatechol monoethers of the 2-(amino-methoxy)phenol type. In the subsequent dark reaction, these monoethers undergo quantitative decomposition by a heterolytic mechanism to give the corresponding pyrocatechols and nitrogen-containing compounds. The rate of this decomposition decreases with decreasing size of the substituent at the position adjacent to the ether bond that is formed upon photoreduction. The redox characteristics of such pyrocatechol monoethers can serve as the criterion of their stability. A weakening of the electron-withdrawing properties of quinones and the electron-donating properties of amines leads to an increase in stability of their reaction products.
- Shurygina,Kurskii,Chesnokov,Druzhkov,Fukin,Abakumov,Cherkasov
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p. 1585 - 1592
(2008/02/08)
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- Highly Lipophilic Benzoxazoles with Potential Antibacterial Activity
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A series of lipophilic 2-substituted 5,7-di-tert-butylbenzoxazoles was prepared in average yields by the reaction of 3,5-di-tert-butyl-1,2-benzoquinone with amino acids and dipeptides bearing N-terminal glycine. Dipeptides having other N-terminal amino acids undergo oxidative deamination. 5,7-Di-tert-butylbenzoxazoles have shown activity against Mycobacterium tuberculosis and some nontuberculous strains where isoniazid has been inactive. Antifungal activity was mediocre.
- Vinsova, Jarmila,Horak, Vaclav,Buchta, Vladimir,Kaustova, Jarmila
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p. 760 - 770
(2007/10/03)
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- Photoreduction of o-benzoquinones in the presence of p-bromo-N,N- dimethylaniline
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Photoreduction of o-benzoquinones in the presence of p-bromo-N,N- dimethylaniline under irradiation (λ, > 500 nm) affords the corresponding pyrocatechols and hydroxyphenyl ethers. The latter are unstable and, in turn, decompose in the dark reaction to pyrocatechols. The ratio between pyrocatechol and hydroxyphenyl ether formed upon the photoreaction is determined by the structure of o-quinone, namely, the presence and bulk of substituents in positions 3 and 6 of the ring. The yield of pyrocatechol is maximal (60-65%) if the substituents are the same (H and H, But and But) or insignificantly differ (Pri and But), regardless of its bulk.
- Chesnokov,Cherkasov,Abakumov,Kurskii,Shurygina,Mamysheva,Shavyrin
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p. 718 - 724
(2007/10/03)
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- Synthesis and Antioxidant Properties of Some Derivatives of Alkylated Pyrocatechol
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Alkylated 1,3-benzodioxane, 1,3-benzoxathiole, o-aminophenols, and 2,3-dihydro-1,3-benzoxazoles were obtained from 3,5-di-tert-butylbenzene-1,2-diol. The antiradical and antioxidant activities of these compounds were examined in the model oxidation of hexane, initiated by γ irradation. The antiradical activity of the ortho analog of tocopherol with a five-membered ring, 7-hydroxy-4,6-di-tert-butyl-1,3-benzoxathiole-2-thione, exceeds fourfold that of the six-membered analog, 8-hydroxy-5,7-di-tert-butyl-1,3-benzodioxane.
- Maslovskaya,Petrikevich,Timoshchuk,Shadyro
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p. 1842 - 1846
(2007/10/03)
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- Synthesis of Substituted Benzoxazoles from 3,5-Di-tert-butyl-1,2-benzoquinone and Aldehyde Oximes
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3,5-Di-tert-butyl-1,2-benzoquinone readily reacts with aldehyde oximes with formation of 2-substituted 4,6-di-tert-butyl-7-hydroxybenzoxazoles.
- Komissarov, V. N.
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p. 984 - 986
(2007/10/03)
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- Redox reactions of 3,5-di-tert-butyl-1,2-benzoquinone. Implications for reversal of paper yellowing
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One- and two-electron transfer reactions of 3,5-di-tert-butylcatechol and the corresponding quinone were studied by fast kinetic spectroscopy coupled with laser photolysis and pulse radiolysis, and by cyclic voltammetry in aqueous solutions.Photoionization of catechol yields the same semiquinone radical as the formate-radical-induced quinone reduction in the pulse radiolysis experiment.The neutral semiquinone radical deprotonates at pKr = 6.0 +/- 0.1, as deduced from the pH induced changes in the radical spectra.The two-electron reduction potentials of quinone and catechol were measured by cyclic voltammetry in aqueous solutions containing 25percent methanol in the pH range 3-14.The pH dependence has two linear parts with slopes of 0.056 and 0.03 V/pH, intersecting at pKa = 10.0.This is in excellent agreement with pKa = 10.05 +/- 0.05 obtained spectrophotometrically.The reduction potential of 3,5-di-tert-butyl quinone, E7 = 0.01 +/- 0.04 V, was obtained from the one-electron transfer equilibrium of the quinone with the oxygen/superoxide redox couple by pulse radiolysis.The rate constant of the reaction of quinone with the superoxide radical, k = 1.2 x 109 M-1 s-1, is higher than those of the superoxide reduction by catechols and phenols (typically ca. 105 M-1 s-1); thus, lignin o-quinones could be efficient scavengers of superoxide under the conditions relevant for the photo-induced yellowing of lignin-rich paper.The reaction with O2.- effectively bleaches yellow quinone and generates metastable furanone, which hydrolyses to muconic acid, thus completely eliminating yellow quinone. 3,5-Di-tert-butylquinone also undergoes rapid bleaching with ascorbate, k = 600 +/- 100 M-1 s-1, in methanol.The reaction has a 1:1 stoichiometry and leads to complete reduction of quinone to catechol with concomitant oxidation of ascorbate to dehydroascorbate.This unusual selectivity and the fact that the reaction of the milder oxidant 3,5-di-tert-butylquinone is an order of magnitude faster than that of stronger oxidant p-benzoquinone (k = 60 +/- 10 M-1 s-1) suggest that a nucleophilic attack of quinone at the ascorbate double bond initiates the reaction. - Keywords: superoxide; lignin; photochemistry; quinone
- Jovanovic, S. V.,Konya, K.,Scaiano, J. C.
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p. 1803 - 1810
(2007/10/03)
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- The formation of orthoquinones in the dimethyldioxirane oxidation of phenols
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The dimethyldioxirane oxidation of selected phenols provides the corresponding orthoquinones. This conversion proceeds via the related arenediols, which are cleanly oxidized to the quinones by this oxidant.
- Crandall, Jack K.,Zucco, Martine,Scott Kirsch,Coppert, David M.
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p. 5441 - 5444
(2007/10/02)
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- Etude de la reaction de germyllithiums sur la di-t-butyl-3,5 orthoquinone: mise en evidence d'un mecanisme par transfert monoelectronique
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Reactions between organogermyllithiums R3GeLi and 3,5-di-t-butylorthoquinone mainly give digermanes but also O-germylcatechol and germadioxolanes.It appears that these reactions start after an initial single electron transfer (SET) which is supported by a
- Riviere, P.,Castel, A.,Ko, Y. H.,Desor, D.
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p. 147 - 156
(2007/10/02)
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- Addition 1,4 de divers organo- et organohalogeno-hydrogermanes sur la di-t-butyl-3,5 orthoquinone
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The thermal 1,4-addition of triorganohydrogermanes R3GeH(R=Et, Ph) with 3,5-di-t-butylorthoquinone leads to their corresponding mono-O-germylated catechols in good yields.Similarly, the organohalohydrogermanes give the 2,2-di-organo- (or 2,2-organohalo)(6,8-di-t-butyl)-4,5-benzo-2-germa-1,3-dioxolanes after dehydrochlorination of transient mono-O-chlorogermylated catechols.Since these reactions are only slightly dependent on solvent and radical initiators, the mechanism probably involves monoelectronic transfer with the formation of a radical anion pair in the first step.The ESR measurements show the transient formation of a paramagnetico-semiquinonic species which supports the proposed mechanism.
- Riviere, P.,Castel, A.,Satge, J.,Guyot, D.,Ko, Y. H.
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- SYNTHESIS OF 1,2-BENZOQUINONES FROM 1,4-BENZODIOXINS USING THE REACTION WITH OZONE FOLLOWED BY PHOTOLYSIS
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Ozonolysis followed by photolysis of 1,4-benzodioxins (1) was carried out, and 1,2-benzoquinones (3) and catechols (4) were obtained as products.It was noteworthy that labile 4-chloro-1,2-benzoquinone (3b) was obtained in a moderate yield as much as that of stable 4-tert-1,2-benzoquinone (3c).Mechanistic study was also discussed.
- Kashima, Choji,Tomotake, Atsushi,Omote, Yoshimori
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p. 363 - 366
(2007/10/02)
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- Photolysis of the Ozonide Derived from 1,4-Benzodioxins. Synthesis of Labile o-Benzoquinones
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By the photolysis of the ozonide derived from 1,4-benzodioxins, o-benzoquinones were obtained in moderate yields independent of the stability of o-benzoquinones and of the substituent groups, except the nitro group.Through the mechanistic studies, it was indicated that o-benzoquinones were formed through a radical decomposition pathway, while catechols were formed through an ionic decomposition pathway induced by acidic impurities.
- Kashima, Choji,Tomotake, Atsushi,Omote, Yoshimori
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p. 5616 - 5621
(2007/10/02)
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- ON THE PREPARATION AND PSEUDOROTATION OF CERTAIN MONOCYCLIC PENTAOXYPHOSPHORANES
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The S-bridged pentaoxyphosphorane 2a has been prepared for the first time and its ground-state structure studied on the time scale of NMR (1H, 19F, 31P, and 13C) spectroscopic measurements.Compound 2a was found to show significant barriers to intramolecular ligand rearrangement (pseudorotation).A comparative study on non-bridged pentaoxyphosphoranes of type 14 was also undertaken.
- Abdou, W. M.,Mahran, M. R.
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p. 119 - 128
(2007/10/02)
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- Mechanism of the Oxidation of NADH by Quinones. Energetics of One-Electron and Hydride Routes
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The kinetics of NADH oxidation by 7 o-benzoquinones and 14 p-benzoquinones were studied by using buffered aqueous solutions and UV/vis spectroscopy.For each quinone the rate law was first order in NADH and first order in quinone.The rate constants varied from 0.0745 to 9220 M-1s-1.Variation of the pH from 6 to 8 gave no change in rate.The use of 4-D and 4,4-D2NADH revealed kinetic isotope effects.The dideutero data gave kH/kD in the range 1.6-3.1 for p-quinones and 4.2 for 3,5-di-tert-butyl-o-quinone.When p-quinones were used, the log k was a linear function of Eo for the quinone/hydroquinone monoanion (Q/QH(1-)) couple with a slope of 16.9 V-1. o-Quinones reacted about 100 times more rapidly, but the same linear relationship with a slope of 16.4 V-1 was observed.Comparisons to data for one-electron-transfer reactions indicate that such mechanisms are not involved.A hydride-transfer mechanism accommodates all the data, and rate-limiting hydrogen atom transfer followed by electron transfer cannot be ruled out.
- Carlson, Brian W.,Miller, Larry L.
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p. 479 - 485
(2007/10/02)
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