- Fe(III) Protoporphyrin IX Encapsulated in a Zinc Metal-Organic Framework Shows Dramatically Enhanced Peroxidatic Activity
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Two MOFs, [H2N(CH3)2][Zn3(TATB)2(HCOO)]·HN(CH3)2·DMF·6H2O (1) and Zn-HKUST-1 (2), were investigated as potential hosts to encapsulate Fe(III) heme (Fe(III) protoporphyrin IX = Fe(III)PPIX). Methyl orange (MO) adsorption was used as an initial model for substrate uptake. MOF 1 showed good adsorption of MO (10.3 ± 0.8 mg g-1) which could undergo in situ protonation upon exposure to aqueous HCl vapor. By contrast, MO uptake by 2 was much lower (2 ± 1 mg g-1), and PXRD indicated that structural instability on exposure to water was the likely cause. Two methods for Fe(III)PPIX-1 preparation were investigated: soaking and encapsulation. Encapsulation was verified by SEM-EDS and showed comparable concentrations of Fe(III)PPIX on exposed interior surfaces and on the original surface of fractured crystals. SEM-EDS results were consistent with ICP-OES data on bulk material (1.2 ± 0.1 mass % Fe). PXRD data showed that the framework in 1 was unchanged after encapsulation of Fe(III)PPIX. MO adsorption (5.8 ± 1.2 mg g-1) by Fe(III)PPIX-1 confirmed there is space for substrate diffusion into the framework, while the UV-vis spectrum of solubilized crystals confirmed that Fe(III)PPIX retained its integrity. A solid-state UV-vis spectrum of Fe(III)PPIX-1 indicated that Fe(III)PPIX was not in a μ-oxo dimeric form. Although single-crystal XRD data did not allow for full refinement of the encapsulated Fe(III)PPIX molecule owing to disorder of the metalloporphyrin, the Fe atom and pyrrole N atoms were located, enabling rigid-body modeling of the porphine core. Reaction of 2,2′-azino-bis(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS) with H2O2, catalyzed by Fe(III)PPIX-1 and -2, showed that Fe(III)PPIX-1 is significantly more efficient than Fe(III)PPIX-2 and is superior to solid Fe(III)PPIX-Cl. Fe(III)PPIX-1 was used to catalyze the oxidation of hydroquinone, thymol, benzyl alcohol, and phenyl ethanol by tert-butyl-hydroperoxide with t1/2 values that increase with increasing substrate molecular volume.
- Dare, Nicola A.,Brammer, Lee,Bourne, Susan A.,Egan, Timothy J.
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- Oxidation of Thymol and Carvacrol to Thymoquinone with KHSO5 Catalyzed by Iron Phthalocyanine Tetrasulfonate in a Methanol–Water Mixture
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Abstract: The oxidation of thymol and carvacrol to thymoquinone with potassium peroxymonosulfate (KHSO5) catalyzed by iron phthalocyanine tetrasulfonate (FePcTS) in a methanol (4.0?mL)–water (0.5?mL) mixture has been carried out. In a typical reaction, the amounts of the substrate, oxidant, and catalyst were 0.300, 0.600, and 1 × 10?3 millimoles, respectively. Ninety-nine percent conversions of thymol in 1?h and of carvacrol in 30?min were achieved at ambient temperature. The major product of both oxidation reactions was thymoquinone (2-isopropyl-5-methylbenzoquinone, TQ) and the reactions also yielded polymeric products poly(2-isopropyl-5-methyl-1,4-phenylene oxide) and poly(5-isopropyl-2-methyl-1,3-phenylene oxide). These polymers are novel and not reported before. When H2O2 or ButOOH was used as the oxidant, the yield of TQ was 1 %. Graphical Abstract: [Figure not available: see fulltext.]
- Günay, Tu??e,?imen, Yasemin,Karabacak, R. Bengü,Türk, Hayrettin
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- Hydrothermal synthesis, crystal structure and heterogeneous catalytic activity of a novel inorganic-organic hybrid complex, possessing infinite La-O-La linkages
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In this paper, a novel lanthanum coordination polymer formulated as {[La2(Hpdc)3(H2O)4]·2H 2O}n (1, H3pdc = 3,5-pyrazoledicarboxylic acid) has been synthesized by the reaction of H3pdc with chloride salt of La(III) under hydrothermal conditions and characterized by elemental analysis, FT-IR, TGA and single-crystal X-ray diffraction. The complex crystallized in the monoclinic system Cc space group. The single-crystal X-ray structural analysis revealed that central metal La atoms are nine-coordinate and linked by bridging μ2-OCOO- groups to form [La(1)- (μ2-OCOO-)2-La(2)]n inorganic-organic chains that produce a supramolecular polymeric framework structure. The three-dimensional structure of 1 is accompanied by non-coordinating water molecules. Thermal behavior and catalytic performance of 1 have also been studied. The complex 1 showed 100% selectivity and a conversion rate of 24% on the oxidation of thymol (T) to thymoquinone (TQ).
- Ay, Burak,Yildiz, Emel,Protasiewicz, John D.,Rheingold, Arnold L.
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- Oxidation of Monoterpenes Catalysed by a Water-Soluble MnIII PEG-Porphyrin in a Biphasic Medium
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It is well established that the transformation of abundant and cheap natural products, such as terpenoids, can produce other more valuable compounds. Thymoquinone, which has a commercial value significantly higher than that of its precursors, can be obtained by oxidation of carvacrol and thymol. In this work, a new water-soluble MnIII PEG-porphyrin is reported as catalyst in a water/hexane (1:1) biphasic medium for the oxidation of carvacrol and thymol into thymoquinone. The reactions were performed using tert-butyl hydroperoxide as oxidant in the presence of ammonium acetate as co-catalyst, reaching 94 and 78 % of conversion after 5 h of reaction for thymol and carvacrol, respectively. Experiments with oregano essential oil as substrate revealed selective transformation of thymol and carvacrol into thymoquinone. The main advantage of this biphasic system based on a water-soluble catalyst and on substrates and products soluble in hexane, is the straightforward isolation, recovery and recycling of the catalyst by simple phase separation. Recycling studies of the MnIII PEG-porphyrin using thymol as substrate showed high conversion values throughout four catalytic cycles.
- Neves, Cláudia M. B.,Tomé, Jo?o P. C.,Hou, Zhanyao,Dehaen, Wim,Hoogenboom, Richard,Neves, M. Gra?a P. M. S.,Sim?es, Mário M. Q.
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- Hydrothermal synthesis, structure, heterogeneous catalytic activity and photoluminescent properties of a novel homoleptic Sm(III)-organic framework
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A novel metal-organic framework, (H2pip)n[Sm2(pydc)4(H2O)2]n (1) (H2pydc=2,6-pyridinedicarboxylic acid, H2pip=piperazine) has been synthesized under hydrothermal conditions and characterized by the elemental analysis, inductively coupled plasma (ICP) spectrometer, fourier transform infrared (FT-IR) spectra, thermogravimetric analysis (TGA), single crystal X-ray diffraction analysis and powder X-ray diffraction (PXRD). The structure of 1 was determined to be three-dimensional, linked along Sm-O-Sm chains. The asymmetric unit consisted of one singly anionic fragment consisting of Sm(III) coordinated to two H2pydc ligands and one water, and one half of a protonated H2pip, which sits on an inversion center. 1 exhibited luminescence emission bands at 534?nm at room temperature when excited at 440?nm. Its thermal behavior and catalytic performance were investigated and the selectivity was measured as 100% for the oxidation of thymol to thymoquinone.
- Ay, Burak,Yildiz, Emel,Felts, Ashley C.,Abboud, Khalil A.
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- Hydrothermal synthesis of a novel μ-dihydroxo-bis(2,6- pyridinedicarboxylatoaquachromium(III)) complex and investigation of its catalytic activity
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A new chromium(III) compound [Cr(H2O)(OH)(C7H 3NO4)]2, μ-dihydroxo-bis(2,6- pyridinedicarboxylatoaquachromium(III)), has been successfully synthesized by the hydrothermal reaction of 2,6-pyridinedicarboxylic acid (H2pydc) and CrCl3·6H2O in the alkali medium. This metal complex was characterized by elemental analysis, IR spectroscopy, thermal analysis and single-crystal X-ray diffraction. The X-ray analysis showed that the structure is molecular and consists of units of two Cr(H2O)(OH) (C7H3NO4) groups linked through two OH groups. In the complex, each Cr centre is in a distorted octahedral environment, defined by two hydroxyl bridges, an aqua ligand and a tridentate pyridinedicarboxylate anion. The thermal stability and catalytic properties of the complex were also investigated. The complex affected the oxidation of thymol to thymoquinone with 100% selectivity and a conversion rate of 20.25%.
- Ay, Burak,Yildiz, Emel,Jones, Stephanie,Zubieta, Jon
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- Two novel isostructural and heteroleptic Nd(III) and Dy(III)-organic frameworks constructed by 2,5-pyridinedicarboxylic acid and in situ generated 2-pyridinecarboxylic acid: Hydrothermal synthesis, characterization, photoluminescence properties and heterogeneous catalytic activities
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The crystal structures, heterogeneous catalytic activities and photoluminescent properties of two novel three dimensional (3D) metal organic frameworks (MOFs), [Nd(pyc)(pydc)(H2O)]n (1) and [Dy(pyc)(pydc)(H2O)]n (2) (H2pydc?=?pyridine-2,5-dicarboxylic acid, Hpyc?=?2-pyridinecarboxylic acid) are presented. The synthesized complexes under hydrothermal conditions were characterized by the elemental analysis, inductively coupled plasma (ICP), fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), single crystal X-ray diffraction and powder X-ray diffraction (PXRD) analysis. For morphological analysis, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) were used. The compounds are isostructural and each Ln3+ (Nd(III) and Dy(III)) centers are eight-coordinated. MOFs have the distinct 3D open-framework architectures due to the presence of Hpyc ligands, which are converted from H2pydc ligands in-situ decarboxylation under the hydrothermal conditions. Photoluminescence properties and thermal stabilities of the compounds have been investigated. Their heterogeneous catalytic activities have also been examined on the oxidation of the thymol (T) to thymoquinone (TQ). The structures of the MOFs were stable after three catalytic cycles. The maximum T conversion values, 40.37% and 36.45% were recorded with nearly 100% selectivities by using 1 and 2, respectively.
- Ay, Burak,Yildiz, Emel,Kani, ?brahim
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- Organophotocatalytic Aerobic Oxygenation of Phenols in a Visible-Light Continuous-Flow Photoreactor
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A mild photocatalytic phenol oxygenation enabled by a continuous-flow photoreactor using visible light and pressurized air is described herein. Products for wide-ranging applications, including the synthesis of vitamins, were obtained in high yields by precisely controlling principal process parameters. The reactor design permits low organophotocatalyst loadings to generate singlet oxygen. It is anticipated that the efficient aerobic phenol oxygenation to benzoquinones and p-quinols contributes to sustainable synthesis.
- Wellauer, Jo?l,Miladinov, Dragan,Buchholz, Thomas,Schütz, Jan,Stemmler, René T.,Medlock, Jonathan A.,Bonrath, Werner,Sparr, Christof
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supporting information
p. 9748 - 9752
(2021/05/27)
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- PHOTOOXIDATION OF 2,3,6-TRIMETHYLPHENOL
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The present invention relates to the photooxidation of 2,3,6-trimethyl- phenol to yield 2,3,5-trimethylbenzoquinone using methylene blue as photo- sensitizer in a solvent mixture of water and alcohols using light of the high wave- length range of the visible spectrum.
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Page/Page column 14-15
(2021/11/26)
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- PHOTOOXIDATION OF PHENOLIC COMPOUNDS
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The present invention relates to the photooxidation of phenolic compounds to the respective quinoid compounds using methylene blue as photosensitizer in a solvent mixture of water and alcohols using light of the high wavelength range of the visible spectrum.
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Page/Page column 17-18
(2021/11/26)
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- PHOTOOXIDATION OF 2,3,5-TRIMETHYLPHENOL
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The present invention relates to the photooxidation of 2,3,5-trimethyl- phenol to yield 2,3,5-trimethylbenzoquinone using methylene blue as photo- sensitizer in a solvent mixture of water and alcohols using light of the high wavelength range of the visible spectrum.
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Page/Page column 14-17
(2021/11/26)
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- Distribution of Spin Density on Phenoxyl Radicals Affects the Selectivity of Aerobic Oxygenation of Phenols
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Phenoxyl radical was generally suggested as the intermediate during copper-catalyzed aerobic oxygenation of phenols. However, the substrate-dependent selectivity has not been well interpreted, due to insufficient characterization of the radical intermediate under reaction conditions. When studying the CuCl-LiCl-catalyzed aerobic phenol oxidation, we obtained EPR spectra of phenoxyl radicals generated by oxidizing phenols with the preactivated catalyst. Upon correlation to the selectivity of benzoquinone, the hyperfine coupling constant of para-site proton (aH, para) was found to be better than the Hammett constant. The catalysis mechanism was studied based on EPR detection and the reaction results of phenoxyl radicals under N2 or O2 atmosphere. It appeared that the chemoselectivity depended on the attack of activated dioxygen on phenoxyl radicals, and the activation of dioxygen by [CunCln+1]- (n = 1, 2, 3) was suggested as the rate-determining step. Understanding of the substrate-dependent selectivity contributed to predicting the chemoselectivity in the aerobic oxidation of phenols.
- Chen, Kaizhou,Du, Renfeng,Fan, Mengtian,Guan, Jun,Jiang, Zheng,Li, Haoran,Lu, Rui,Mei, Bingbao,Wang, Yongtao,Yao, Jia
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- Thymoquinone derivative, intermediate, as well as preparation method and application of thymoquinone derivative
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The invention discloses a thymoquinone derivative, an intermediate, as well as a preparation method and application of the thymoquinone derivative. The structure of the thymoquinone derivative disclosed by the invention is shown as a formula (I). The preparation method of the thymoquinone derivative provided by the invention has the advantages of use of cheap and readily-available raw materials, less reaction steps and high yield, is suitable for industrial production, and has a better prospect.
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Paragraph 0033-0037
(2019/08/03)
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- Thymoquinone derivative, and preparation method and applications thereof
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The invention relates to a thymoquinone derivative, and a preparation method and applications thereof, and belongs to the technical field of organic synthesis. The molecular general formula of the novel thymoquinone derivative is disclosed in the invention. The novel thymoquinone derivative possesses obvious inhibition effect on cancer cells; the adopted raw materials are cheap; preparation is simple and convenient; reaction steps are few; yield is high; the preparation method is suitable for industrialized production; and the thymoquinone derivative is a medicine with promising prospect.
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Paragraph 0049; 0052; 0053; 0054; 0063; 0066; 0071; 0074
(2019/11/13)
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- Quinone C-H Alkylations via Oxidative Radical Processes
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A brief survey of radical additions to quinones is reported. Carboxylic acids, aldehydes, and unprotected amino acids are compared as alkyl radical precursors for the mono- or bis- C-H alkylation of several quinones. Two methods for radical initiation are discussed comparing inorganic persulfates and Selectfluor as stoichiometric oxidants. Kinetic analysis reveals dramatic differences in the rate of radical initiation depending on the identity of the radical precursor and oxidant. Synthetic strategies for efficiently producing alkyl-quinones are discussed in the context of selecting optimum radical precursors and initiators depending on quinone identity and functional groups present.
- Hamsath, Akil,Galloway, Jordan D.,Baxter, Ryan D.
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p. 2915 - 2923
(2018/06/12)
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- Silver-Catalyzed Minisci Reactions Using Selectfluor as a Mild Oxidant
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A new method for silver-catalyzed Minisci reactions using Selectfluor as a mild oxidant is reported. Heteroarenes and quinones both participate in radical C-H alkylation and arylation from a variety of carboxylic and boronic acid radical precursors. Several oxidatively sensitive and highly reactive radical species are successful, providing structures that are challenging to access by other means.
- Galloway, Jordan D.,Mai, Duy N.,Baxter, Ryan D.
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supporting information
p. 5772 - 5775
(2017/11/10)
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- Hydrothermal synthesis and characterization of {[Ni2(NA)4(μ-H2O)]·2H2O}n (HNA = nicotinic acid) and its heterogeneous catalytic effect
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A carboxylate-bridged metal-organic coordination polymer {[Ni2(NA)4(μ-H2O)]·2H2O}n (1, HNA = nicotinic acid) has been synthesized under hydrothermal conditions and characterized by FT-IR, TG/DTA, micro analysis and single-crystal X-ray diffraction. 1 has an interesting 3D network structure and adjacent networks are further connected together via strong π-π packing interactions. The thermal behavior and catalytic performance of 1 were investigated and its selectivity was measured as 100% for the oxidation of thymol (T) to thymoquinone (TQ).
- Ay, Burak,Ya?, G?zde,Yildiz, Emel,Rheingold, Arnold L.
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p. 164 - 169
(2015/02/05)
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- Thymol Bromination - A Comparison between Enzymatic and Chemical Catalysis
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The catalytic activity of the vanadium-dependent bromoperoxidase isolated from the brown alga Ascophyllum nodosum is compared with the activity of a cheap, commercially available V-catalyst precursor in the bromination of thymol. Organic solvents have been avoided to make the system appealing from a sustainable chemistry point of view. It is noteworthy that, notwithstanding the low solubility of the substrate, the thymol bromination reactions were performed in water, with a safe brominating source, under mild conditions, and with relatively inexpensive reagents. In this regard, the greenness of the systems was evaluated by the estimation of the E-factor value; the result is that the chemical reaction has a lower environmental impact than the enzymatic process, with an E-factor in the range of eco-friendly processes. Catalysis of thymol bromination by vanadium derivatives is directly compared to catalysis by a V-dependent bromoperoxidase. All reactions were performed under mild and sustainable conditions with relatively inexpensive reagents. Appealing results were obtained in terms of selectivity and sustainability.
- Sabuzi, Federica,Churakova, Ekaterina,Galloni, Pierluca,Wever, Ron,Hollmann, Frank,Floris, Barbara,Conte, Valeria
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p. 3519 - 3525
(2015/03/30)
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- The Diels-Alder reactions of para-benzoquinone nitrogen-derivatives: An experimental and theoretical study
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An experimental and theoretical study of the comparative reactivity and selectivity of the Diels-Alder reactions of para-benzoquinones and three nitrogen derivatives have been performed. The mono-oximes derivatives do not react under the tested reaction conditions, whereas the tosylated mono-oximes react slowly. However, the mono N-tosyl imines show excellent reactivity, and superior to the parent parabenzoquinones. DFT calculations support these experimental results.
- Uliana, Marciana P.,Servilha, Bruno M.,Alexopoulos, Olga,De Oliveira, Kleber T.,Tormena, Cláudio F.,Ferreira, Marco A.B.,Brocksom, Timothy J.
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p. 6963 - 6973
(2015/11/09)
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- Rapid conversion of phenols to p-benzoquinones under acidic conditions with lead dioxide
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Treatment of 4-unsubstituted and 4-halogenated phenols with PbO2 and 70% HClO4 in AcOH afforded the corresponding p-benzoquinones in fair to high yields. The oxidation of 4-substituted 2,6-di-tertbutylphenols 6 with PbO2 and 70% HClO4 in acetone gave 2,6-di-tert-butyl-p-benzoquinone (2).
- Omura, Kanji
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p. 1145 - 1148
(2007/10/03)
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- Comparative pulse radiolysis studies of alkyl- and methoxy-substituted semiquinones formed from quinones and hydroquinones
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Absorption spectra and rate constants for the disproportionate of 12 alkyl- and methoxy-substituted semiquinone anion free radicals (Q?-) produced by the one-electron reduction (using CO2?- as a reductant) of 1,4-benzoquinones and 1,4-naphthoquinone (Q) as well the oxidation (using N3? as an oxidant) of the corresponding hydroquinones (QH2) were determined by pulse radiolysis in 50 mM sodium phosphate buffer, pH 7.40 at room temperature. Both spectral and kinetic characteristics of Q?- only moderately depended on whether Q?- was produced from Q or QH2. Spectra of benzosemiquinones display two peaks with maximum at 310-320 nm and ca. 430 nm with the ratio of about 2-2.5. Molar absorption coefficients were determined. Rate constants for Q?- disproportionation (2k1) were correlated with the nature of substituents. While 2k1 was scarcely affected by methyl substitution, Q?- containing isopropyl, tert-butyl and methoxy substituents were visibly more stable than non-substituted and methyl-substituted Q?-.
- Roginsky, Vitaly A.,Pisarenko, Leonid M.,Bors, Wolf,Michel, Christa,Saran, Manfred
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p. 1835 - 1840
(2007/10/03)
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- Electrochemical Methoxylation of Thymol and Carvacrol
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Anodic oxidation of methanolic solutions of thymol and carvacrol, each in a single cell at constant current intensity, afforded substitution and addition products in the former case and only a nucleophilic-addition product in the latter.
- Barba, Isidoro,Banon, Jorge
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- Radical Anion Reactions of Cyclobutane Derivatives: Electron-Transfer Cleavage of Dithymoquinone
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One-electron reduction of dithymoquinone, a quinone cyclobutane dimer, results in its cleavage to the monomeric quinone with a rate constant of 3.0 s-1.
- Robbins, Rebecca J.,Falvey, Daniel E.
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p. 3616 - 3618
(2007/10/02)
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- A Strategy for Generalization of the Regiospecific Synthesis of Substituted Quinones from Cyclobutenediones
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Documented within is a straightforward protocol for the synthesis of generally substituted benzoquinones and ring-fused quinones.Previously, the crucial issue of quinone substituent regiochemistry was resolved at the stage of addition of an unsaturated carbon nucleophile to a cyclobutenedione by using either symmetrically substituted cyclobutenediones or 3-alkoxy (or amino)-4-substituted-3-cyclobutenediones.In the former case there are no regioisomeric quinones formed, while in the latter, through resonance delocalization, the alkoxy (or amino) substituent renders one of the two carbonyl groups less reactive and directs the incoming nucleophile to the other.The placement of a wide variety of substituents about the quinone ring periphery has now been solved by the less restrictive strategy of sequential introduction of substituents onto a cyclobutenedione core.The chemistry commences with 3-isopropoxy-4-substituted-3-cyclobutene-1,2-diones.Addition of an aromatic, heteroaromatic, or alkenyl nucleophile to the more reactive carbonyl group provides 4-hydroxy-4-Runsat-2-cyclobutenones, which are protected as the methyl ethers by treatment with MeI/Ag2O/K2CO3 in MeCN.A second nucleophile is added, again in a 1,2-sense, providing highly substituted 3-isopropoxy-2-cyclobutenols that are arranged to cyclobutenones under acidic conditions.The resulting cyclobutenones are converted into substituted quinones by thermolysis at 140 deg C in o-xylene followed by oxidative workup with ceric ammonium nitrate.The substitution pattern about the quinone core is rigorously controlled by the sequence of introduction of the substituents.
- Liebeskind, Lanny S.,Granberg, Kenneth L.,Zhang, Jing
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p. 4345 - 4352
(2007/10/02)
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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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- A CONVENIENT SYNTHESIS OF ALKYL-SUBSTITUTED p-BENZOQUINONES FROM PHENOLS BY A H2O2/HETEROPOLYACID SYSTEM
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Alkyl-substituted p-benzoquinones were easily synthesized in good yields by the oxidation of the corresponding phenols with a hydrogen peroxide/heteropolyacid couple in acetic acid
- Shimizu, Masao,Orita, Hideo,Hayakawa, Takashi,Takehira, Katsuomi
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p. 471 - 474
(2007/10/02)
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- Efficient Preparation of Some Biologically Active Substances from Natural and Nonnatural Aromatic Compounds by m-Chloroperbenzoic Acid Oxidation
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Six naturally occurring aromatic terpenoids and six nonnatural aromatic compounds were oxidized by m-chloroperbenzoic acid in chloroform to give 1,2- and 1,4-quinones or hydroxylated products in which vitamin K1, insecticidal, piscicidal, and antifungal compounds were included.The present method is advantageous for obtaining different types of natural or nonnatural aromatic products having biological activity from the starting aromatic compounds in a one-step reaction.
- Asakawa, Yoshinori,Matsuda, Reiko,Tori, Motoo,Sono, Masakazu
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p. 5453 - 5457
(2007/10/02)
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- COMPARATIVE OXIDATION OF PHENOLS WITH BENZENESELENINIC ANHYDRIDE AND WITH BENZENESELENINIC ACID
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Oxidation of phenols by benzeneseleninic acid 2 in methylene dichloride leads to the para-quinones, whereas oxidation by benzeneseleninic anhydride 1 is confirmed to afford the corresponding ortho-quinones.Addition of indole, as a phenylselenium (II) trapping agent, inhibits the formation of phenylselenoquinones in the oxidation with 1 or 2.
- Barton, Derek H. R.,Finet, Jean-Pierre,Thomas, Martial
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p. 6397 - 6406
(2007/10/02)
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- A SIMPLE AND EFFICIENT SYNTHESIS OF THYMOQUINONE AND METHYL P-BENZOQUINONE
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The Co(II) (salen) catalyzed oxidations of thymol (1), carvacol (2), o- and m-cresol, with molecular oxygen give high yields of the corresponding p-benzoquinones.
- Dockal, Edward R.,Cass, Quezia B.,Brocksom, Timothy J.,Brocksom, Ursula,Correa, Arlene G.
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p. 1033 - 1036
(2007/10/02)
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- PHELLANDRENE ENDOPEROXIDES FROM THE ESSENTIAL OIL OF CHENOPODIUM MULTIFIDUM
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Key Word Index - Chenopodium multifidum; Chenopodiaceae; essential oil; p-menthanic monoterpenes; phellandrne endoperoxides. The ssential oil of Chenopodium multifidum does not contain ascaridole, but does contain two isomeric endoperoxides related to α-phellandrene, besides other structurally and biogenetically related p-menthanic monoterpenes.
- Pascual-T., J. de,Bellido, I. S.,Torres, C.,Sastre, B. A.,Grande, M.
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p. 163 - 165
(2007/10/02)
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