- A convenient two-step synthesis of Coenzyme Q1
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A convenient method for the preparation of Coenzyme Q1 from cheap and readily available 3,4,5-trimethoxytoluene is developed. Coenzyme Q1 is synthesized in a moderate yield by a two-step procedure involving the key reaction of an allyl bromide with Coenzyme Q0 through a redox chain reaction. The reaction is efficient and can be used for the synthesis of other Coenzyme Q compounds.
- Lu, Bin,Qiu, Yong-Fu,Qi, Shi,Wang, Jin
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- Polyoxometalate-based supramolecular porous frameworks with dual-active centers towards highly efficient synthesis of functionalized: P -benzoquinones
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Selective oxidation of substituted phenols is an ideal method for preparing functionalized p-benzoquinones (p-BQs), which serve as versatile raw materials for the synthesis of a variety of biologically active compounds. Herein, two new polyoxometalate-based supramolecular porous frameworks, K3(H2O)4[Cu(tza)2(H2O)]2[Cu(Htza)2(H2O)2][BW12O40]·6H2O (1) and H3K3(H2O)3[Cu(Htza)2(H2O)]3[SiW12O44]·14H2O (2) (Htza = tetrazol-1-ylacetic acid), were synthesized and structurally characterized by elemental analysis, infrared spectroscopy, thermal analysis, UV-vis diffuse reflectance spectroscopy, and single-crystal X-ray and powder diffraction. The single-crystal X-ray diffraction analysis indicates that both compounds possess unique petal-like twelve-nucleated Cu-organic units composed of triangular and hexagonal metal-organic loops. In 1, the Cu-organic units are isolated and [BW12O40]5- polyoxoanions are sandwiched between staggered adjacent triangular channels in the structure. However in 2, the Cu-organic units extend into a two-dimensional layered structure, and the [SiW12O44]12- polyoxoanions occupy the larger hexagonal channels in the stacked structure. Both compounds as heterogeneous catalysts can catalyze the selective oxidation of substituted phenols to high value-added p-BQs under mild conditions (60 °C) with TBHP as the oxidant, particularly in the oxidation of 2,3,6-trimethylphenol to 2,3,5-trimethyl-p-benzoquinone (TMBQ, key intermediate in vitamin E production). Within 8-10 min, the yield of TMBQ is close to 100%, and oxidant utilization efficiency is up to 94.2% for 1 and 90.9% for 2. The turnover frequencies of 1 and 2 are as high as 5000 and 4000 h-1, respectively. No obvious decrease in the yield of TMBQ was observed after five cycles, which indicates the excellent sustainability of both compounds. Our study of the catalytic mechanism suggests that there is a two-site synergetic effect: (i) the copper ion acts as the catalytic site of the homolytic radical pathway; and (ii) the polyoxoanion acts as the active center of the heterolytic oxygen atom transfer pathway. This journal is
- An, Haiyan,Chang, Shenzhen,Chen, Yanhong,Huang, Yaohui,Luo, Huiyun,Zhu, Qingshan
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p. 8591 - 8603
(2021/11/17)
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- Coenzyme Q compound synthesis method
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The invention relates to a coenzyme Q compound synthesis method, which comprises the steps of: dissolving substituted or unsubstituted 3, 4, 5-trimethoxytoluene in an organic solvent, carrying out a reaction on the obtained solution and an oxidant aqueous solution for 1-2h at a temperature of 20-80 DEG C under the catalysis of an acid, and carrying out extraction, water washing, reduced pressure distillation and recrystallization on the obtained crude product to obtain a coenzyme Q compound. Raw materials used in the method are cheap and easy to obtain, and no toxic or harmful waste gas or waste residue is generated in the reaction process; and reaction steps are few, the operation is easy and convenient, the product yield is high, and the method is suitable for industrial large-scale production.
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Paragraph 0025-0032
(2020/11/01)
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- Regiodivergent oxidation of alkoxyarenes by hypervalent iodine/oxone system
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We have found that the combination of Oxone with an organoiodine compound, i.e., 2-iodobenzoic acid (2-IB), selectively yields p-quinones from monomethoxyarenes under mild conditions. In this reaction system, an organoiodine compound is immediately oxidized by Oxone to generate cyclic hypervalent iodine (III) species in situ, which serves as the specific mediator for the selective p-quinone synthesis, preventing o-quinone formation.
- China, Hideyasu,Tanihara, Kokoro,Sasa, Hirotaka,Kikushima, Kotaro,Dohi, Toshifumi
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- Synthesis of coenzyme Q0 through divanadium-catalyzed oxidation of 3,4,5-trimethoxytoluene with hydrogen peroxide
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The selective oxidation of methoxy/methyl-substituted arenes to the corresponding benzoquinones has been first realized using aqueous hydrogen peroxide as a green oxidant, acid tetrabutylammonium salts of the γ-Keggin divanadium-substituted phosphotungstate [γ-PW10O38V2(μ-O)2]5- (I) as a catalyst, and MeCN as a solvent. The presence of the dioxovanadium core in the catalyst is crucial for the catalytic performance. The reaction requires an acid co-catalyst or, alternatively, a highly protonated form of I can be prepared and employed. The industrially relevant oxidation of 3,4,5-trimethoxytoluene gives 2,3-dimethoxy-5-methyl-1,4-benzoquinone (ubiquinone 0 or coenzyme Q0, the key intermediate for coenzyme Q10 and other essential biologically active compounds) with 73% selectivity at 76% arene conversion. The catalyst retains its structure under turnover conditions and can be easily recycled and reused without significant loss of activity and selectivity.
- Zalomaeva, Olga V.,Evtushok, Vasilii Yu.,Maksimov, Gennadii M.,Maksimovskaya, Raisa I.,Kholdeeva, Oxana A.
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p. 5202 - 5209
(2017/04/27)
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- A preparation method of idebenone (by machine translation)
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The invention relates to a preparation method of idebenone, the method comprises: to coenzyme Q0 and 11 - hydroxy undecanoic acid as the raw material, the choice of copper chloride, copper sulfate, copper acetate, silver carbonate, silver oxide, palladium chloride or palladium acetate in a metal salt as a catalyst, in the protection of the next adds oxygen oxidizing agent hydrogen peroxide, alkylation of the free radical reaction. The reaction system by extraction, water washing, drying, reduced pressure distillation, column chromatography, get the yellow needle-like crystal, 6 - (10 - hydroxyl decyl) - 2, 3 - dimethoxy - 5 - methyl - 1, 4 - benzoquinone, namely idebenone. This preparation method has a simple operation, low cost, and the yield and the like, suitable for large-scale industrial production of idebenone. (by machine translation)
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Paragraph 0020; 0023; 0025; 0027; 0029; 0031; 0033
(2017/09/01)
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- ONO-pincer ruthenium complex-bound norvaline for efficient catalytic oxidation of methoxybenzenes with hydrogen peroxide
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The enhanced catalytic activity of ruthenium complex-bound norvaline Boc-l-[Ru]Nva-OMe 1, in which the ONO-pincer ruthenium complex Ru(pydc)(terpy) 2 is tethered to the α-side chain of norvaline, has been demonstrated for the oxidation of methoxybenzenes to p-benzoquinones with a wide scope of substrates and unique chemoselectivity.
- Yoshida, Ryota,Isozaki, Katsuhiro,Yokoi, Tomoya,Yasuda, Nobuhiro,Sadakane, Koichiro,Iwamoto, Takahiro,Takaya, Hikaru,Nakamura, Masaharu
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supporting information
p. 7468 - 7479
(2016/08/16)
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- Catalytic formation of hydrogen peroxide from coenzyme NADH and dioxygen with a water-soluble iridium complex and a ubiquinone coenzyme analogue
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A ubiquinone coenzyme analogue (Q0: 2,3-dimethoxy-5-methyl-1,4-benzoquinone) was reduced by coenzyme NADH to yield the corresponding reduced form of Q0 (Q0H2) in the presence of a catalytic amount of a [C,N] cyclometalated organoiridium complex (1: [IrIII(Cp?)(4-(1H-pyrazol-1-yl-κN2)benzoic acid-κC3)(H2O)]2SO4) in water at ambient temperature as observed in the respiratory chain complex I (Complex I). In the catalytic cycle, the reduction of 1 by NADH produces the corresponding iridium hydride complex that in turn reduces Q0 to produce Q0H2. Q0H2 reduced dioxygen to yield hydrogen peroxide (H2O2) under slightly basic conditions. Catalytic generation of H2O2 was made possible in the reaction of O2 with NADH as the functional expression of NADH oxidase in white blood cells utilizing the redox cycle of Q0 as well as 1 for the first time in a nonenzymatic homogeneous reaction system.
- Suenobu, Tomoyoshi,Shibata, Satoshi,Fukuzumi, Shunichi
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supporting information
p. 7747 - 7754
(2016/08/06)
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- Synthesis and antioxidant activities of Coenzyme Q analogues
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A series of 2,3-dimethoxy-5-methyl-1,4-benzoquinones (Coenzyme Q) substituted at the C-6 position with various groups were designed and synthesized based on the Coenzyme Q10 as potent antioxidant. In vitro antioxidant activities of these compounds were evaluated and compared with commercial antioxidant Coenzyme Q10 employing DPPH assay. All these synthesized Coenzyme Q analogues are found to exhibit good antioxidant activities. Of which Compound 8b bearing a N-benzoylpiperazine group at the C-6 position showed more potent inhibition of DPPH radical than Coenzyme Q10. All these results suggested the applicability of the Coenzyme Q analogues as potent antioxidants for combating oxidative stress.
- Wang, Jin,Li, Shuo,Yang, Tao,Yang, Jian
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p. 710 - 713
(2015/02/19)
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- Two-step synthesis of 2-(9-Hydroxynonyl)-5,6-dimethoxy-3-methyl-1,4- benzoquinone
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2-(9-Hydroxynonyl)-5,6-dimethoxy-3-methyl-1,4-benzoquinone was readily synthesized from commercially available 3,4,5-trimethoxytoluene in two steps. First, 2,3-dimethoxy-5-methyl-1,4-benzoquinone (coenzyme Q0) was obtained in one step by treatment of 3,4,5-trimethoxytoluene with hydrogen peroxide under metal-free conditions, followed by free-radical alkylation with 10-hydroxydecanoic acid in the presence of potassium peroxodisulfate and silver nitrate in a mixed solvent (MeCN-H2O, 1:1) to afford the title compound in good yields (60%, based on coenzyme Q0). Georg Thieme Verlag Stuttgart. New York.
- Wang, Jin,Hu, Xiao,Yang, Jian
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p. 2371 - 2375
(2014/11/08)
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- A switchable oxidation process leading to two various versatile pharmaceutical intermediates
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An efficient high-yielding and environmentally benign switchable oxidation process that can selectively produce two different versatile synthetic intermediates is disclosed. One of the two intermediates, 2,3-dimethoxy-5- methylcyclohexa-2,5-diene-1,4-dione (coenzyme Q0), is obtained by means of a telescoped two-step synthetic protocol that in the first step involves treatment of the substrate (1,2,3-trimethoxy-5-methylbenzene) with hydrogen peroxide in acetic acid with p-toluene sulphonic acid present as a Bronsted acid catalyst, succeeded by a telescoped second step that entails treatment with fuming nitric acid to achieve the target molecule in an excellent isolated yield (88%). If the substrate is treated directly with nitric acid (65%) in glacial acetic acid two different products can be obtained, namely acetic acid 3,4,5-trimethoxybenzyl ester in a superb isolated yield (93%) or, under slightly altered reaction conditions, 1,2,3-trimethoxy-5- (nitromethyl)benzene in a moderate to low yield (35%) and low selectivity. The two pathways leading to the two different products in the nitric acid oxidation protocol were investigated by means of DFT calculations as an aid to elaborate a proposal for the reaction mechanism.
- Occhipinti, Giovanni,Liguori, Lucia,Tsoukala, Anna,Bjorsvik, Hans-Rene
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supporting information; experimental part
p. 1379 - 1384
(2011/09/20)
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- Novel intermediates, process for their preparation and synthesis of 1, 4-benzoquiones
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The present invention discloses a new process for the preparation of 1,4-benzoquiones of formula (II) wherein R1, R2, R3 and R4 are independently selected from the group consisting of branched or unbranched C1-C6 alkyl, phenyl and benzyl, wherein phenyl and benzyl is optionally substituted by one or more substituent independently selected from the group consisting of C1-C6 alkyl and halogen, and wherein C1-C6 alkyl is optionally substituted with one or more halogen susbstituents, and wherein R2 and R3 together can form a C1-C6-alkylene radical, optionally substituted by one or more susbstituents independently selected from the group comprising C1-C6, benzyl, phenyl and halogen. One preferred compound is 2,3-dimethoxy-5-methyl-[1,4]benzoquinone, also known as coenzyme Q0 (CoQ0). Also disclosed are novel compounds and intermediates, and a method for the preparation of coenzyme Qn, preferable the coenzyme Q10. Also disclosed is a method for continuous synthesis of 1,4-benzoquiones in a continuous flow reactor.
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Page/Page column 3; 4-5
(2008/12/09)
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- Convenient oxidation of alkylated phenols and methoxytoluenes to antifungal 1,4-benzoquinones with hydrogen peroxide (H2O2)/methyltrioxorhenium (CH3ReO3) catalytic system in neutral ionic liquid
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Alkylated phenol and methoxytoluene derivatives were catalytically and selectively oxidized to the corresponding 1,4-benzoquinones in good conversions and yields. Reactions were performed with hydrogen peroxide (H2O2)/methyltrioxorhenium (CH3ReO3) in 1-butyl-3-methylimidazolium tetrafluoroborate [bmim]BF4, a neutral ionic liquid. Compounds were tested in vitro for their antifungal activity against the growth of several widespread soil fungi. Some of them were proved to be potent inhibitors of Fusarium sp. than ketoconazole, a commercially available and expensive antifungal agent.
- Bernini, Roberta,Mincione, Enrico,Barontini, Maurizio,Fabrizi, Giancarlo,Pasqualetti, Marcella,Tempesta, Sabrina
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p. 7733 - 7737
(2007/10/03)
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- A PRACTICAL, COST-EFFECTIVE SYNTHESIS OF CHLOROMETHYLATED 1,4-BENZOQUINONES
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The present invention relates to a practical and cost-effective method for the synthesis of 5-chloromethylated 2,3-dialkoxy-6-alkyl-1,4-benzoquinones by direct chloromethylation of the corresponding 2,3-dialkoxy-6-alkyl-1,4-benzoquinones. The invention further relates to a method for the preparation of 5-chloromethylated 2,3-dialkoxy-6-alkyl-1,4-benzoquinones starting from a 3,4,5-trialkoxy-1-alkyl-benzene. The invention also relates to a method for the production of Coenzymes Qn, especially coenzyme Q10.
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Page/Page column 10
(2008/06/13)
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- Titanium superoxide catalyzed selective oxidation of phenols to p-quinones with aq. H2O2
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Titanium superoxide, a novel heterogeneous and readily accessible catalyst, is found to catalyze the selective oxidation of phenols to the corresponding 1,4-benzoquinones in preparative yields with aq. 30% H2O2 as oxidant under mild reaction conditions.
- Dewkar, Gajanan K.,Shaikh, Tanveer M.,Pardhy,Kulkarni, Swati S.,Sudalai, Arumugam
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p. 1530 - 1532
(2007/10/03)
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- New convenient synthesis of iridol. An approach to the synthesis of ubiquinones
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A strategy for the synthesis of ubiquinones, in which iridol is the key intermediate, has been developed, together with a new convenient synthesis of iridol (2,3-dimethoxy-5-methylphenol) starting from the easily available 4-methylphenol and using mild conditions and friendly and high-yielding reactions.
- Bovicelli, Paolo,Antonioletti, Roberto,Barontini, Maurizio,Borioni, Giorgio,Bernini, Roberta,Mincione, Enrico
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p. 1255 - 1257
(2007/10/03)
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- A novel and convenient synthesis of coenzyme Q1
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A convenient and efficient synthetic route to Coenzyme Q1 (6) starting from 3,4,5-trimethoxytoluene (1) is described. The key features of this synthesis include the Diels-Alder reaction of 2,3-dimethoxy-1,4-benzoquinone (3) with cyclopentadiene and the introduction of a C5 side chain to 4,5-dimethoxy-2-methyltricyclo[6.2.1.02,7]undeca-4,9-diene-3,6-dione (4) under mild conditions, (6) was obtained in overall 60% yield.
- Lu, Liang,Chen, Fener
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p. 4049 - 4053
(2007/10/03)
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- Synthesis and spectroscopic characterization of [5-13C]- and [6-13C]ubiquinone-10 for studies of bacterial photosynthetic reaction centers
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This paper presents the synthesis and characterization by mass spectrometry and NMR spectroscopy of [2-13C]- and [3-13C]ubiquinone-0 and of [5-13C]- and [6-13C]ubiquinone-10. A scheme based on the synthetic approach to [5-13C]ubiquinone-10 has been worked out for the synthesis of ubiquinones 13C-labeled at any individual position and at every combination of positions in the quinone ring. The [5-13C]- and [6-13C]ubiquinone-10 isotopomers were incorporated into the QA-site of the photosynthetic reaction center of Rhodobacter sphaeroides R-26. Magic angle spinning NMR subsequently revealed an unperturbed 6-position, while the signal of the 5-position was absent. These results corroborate the recently reported detection of an asymmetric binding of QA with a dynamic perturbation involving the 4-carbonyl functionality.
- Boers, Rutger B.,Gast, Peter,Hoff, Arnold J.,De Groot, Huub J. M.,Lugtenburg, Johan
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p. 189 - 202
(2007/10/03)
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- Synthesis of 2,3-dimethoxy-5-methyl-1,4-benzoquinone: A key fragment in coenzyme-q series
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Preparation of the title compound by a reaction sequence starting from gallic acid present in mango kernel is described.
- Chida,Vani,Chandrasekharam,Srinivasan,Singh
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p. 657 - 660
(2007/10/03)
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- Synthesis of [3-D3]-, [3-13C]-, and [1,2-13C2]propynes and their use for the synthesis of [5-D3-methyl]-, [5-13C-methyl]-, and [5,6- 13,C2-2,5-cyclohexadienyl]ubiquinones 3
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Three selectively labeled propynes were prepared either with deuterium or carbon-13 at position 3 and doubly labeled with carbon-13 at positions 1 and 2 by an alkylation reaction from the corresponding labeled or unlabeled monolithio acetylides and dimethylsulfates. Their lithiation with nBuLi gave the corresponding propynyllithium derivatives which reacted with dimethyl squarate to afford the corresponding propargylic alcohols. These were thermolysed in p-xylene to furnish [5-D3-methyl]-, [5-13C-methyl]-, and [5,6-13C2-2,5-cyclohexadienyl]ubiquinone. The farnesyl side chain was introduced onto the labeled quinones with farnesyl trimethyltin under BF3 catalysis to provide [5-D3-methyl]-, [5-13C-methyl]-, and [5,6-13C2- 2,5-cyclohexadienyl]ubiquinone 3 (6c, 6b, 6a, respectively).
- Boullais, Claude,Rannou, Christelle,Reveillere, Emmanuel,Mioskowski, Charles
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p. 723 - 727
(2007/10/03)
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- Oxidation of marchantin A trimethyl ether and related aromatic compounds with m-chloroperbenzoic acid
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Marchantin A trimethyl ether was subjected to react with m-chloroperbenzoic acid to yield hydroxylated derivatives as well as ring C degraded esters. This reaction was confirmed by application to catechol dimethyl ether and dihydroeugenol dimethyl ether.
- Tori, Motoo,Sono, Masakazu,Toyota, Masao,Asakawa, Yoshinori
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p. 647 - 650
(2007/10/03)
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- Ring expansion of 4-alkynylcyclobutenones. Synthesis of piperidinoquinones, highly substituted dihydrophenanthridines, benzophenanthridines, and the naturally occurring pyrrolophenanthridine, assoanine
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New synthetic routes to a variety of N-heterocyclic quinones and hydroquinones are described. These include thermolyses of 4-hydroxy-4-[4-N-(benzenesulfonyl)-4-aza-1,6-dialkynyl]cyclobutenones to piperidinoquinones and 4-hydroxy-4-[3-(N-phenylamino)-1-propynyl]cyclobutenones to dihydrophenanthridinediols. Included in the array of products available by this method are benzophenanthridines, indolophenanthridines, isoindoloindoles, and pyrrolophenanthridines. The methodology was employed in a five-step synthesis of the alkaloid assoanine starting with dimethyl squarate and indoline. The key step in all of these transformations is the ring expansion of appropriately substituted 4-hydroxy-4-alkynylcyclobutenones. These are envisaged to undergo electrocyclic ring opening to the corresponding enynylketenes which ring close to diradical intermediates that then lead to products via either radical additions to proximal alkyne moieties or undergo homolytic aromatic substitution to appropriately placed aryl groups. The synthetic scope and mechanism of the ring expansion reactions are discussed.
- Xiong, Yifeng,Moore, Harold W.
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p. 9168 - 9177
(2007/10/03)
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- SPECTROSCOPIC STUDY OF THE PHOTOCHEMICAL AND CHEMICAL GENERATION OF RADICAL MOIETIES IN A SOLUTION OF UBIQUINONE-0
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Key words: laser flash photolysis; absorption spectrum; anion-radical; ubiquinone-0.
- Plyusnin, V. F.,Samoilova, R. I.,Grivin, V. P.
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p. 240 - 245
(2007/10/03)
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- Synthesis and spectroscopic characterisation of 13C-labelled ubiquinone-0 and ubiquinone-10
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(1-13C)-, (2-13C)-, (3-13C)-, (3-13CH3)-, (4-13C)-, and (13CH3O)2-ubiquinone-10 and the corresponding (1-13C)-, (6-13C)-, (5-13C)-, (5-13CH3)-, (4-13C)-, and (13CH3O)2-ubiquinone-0 have been synthesised from simple labelled starting materials via a single reaction scheme.The ubiquinones have been characterised using mass spectrometry, 1H NMR and 13C NMR.The spectroscopic results indicate that, within experimental error, the syntheses have been accomplished without scrambling or dilution of label.All labelled ubiquinones have been synthesised on a decigram scale.
- Liemt, W. B. S. van,Steggerda, W. F.,Esmeijer, R.,Lugtenburg, J.
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p. 153 - 162
(2007/10/02)
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- The acid-catalyzed oxidation of methoxybenzenes to p-benzoquinones by dimethyldioxirane
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Methoxybenzenes 1 were oxidized to phenols and/or p-benzoquinones by dimethyldioxirane; in the presence of strong acids, the intermediate phenols were effectively converted to the p-benzoquinones 3.
- Adam,Shimizu
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p. 560 - 562
(2007/10/02)
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- Synthesis of crown ethers related to ubiquinones
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Crown ethers in which the two methoxy groups of ubiquinone-0 (2,3-dimethoxy-5-methyl-1,4-benzoquinone) are replaced by oligoethylene glycol bridges have been obtained in five straightforward steps in 35-40% overall yield from 5-methylpyrogallol. A Fremy salt oxidation of a phenolic precursor is used in the final step. The further elaboration of crown ether analogues of ubiquinone-2 was achieved by enol geranylation of cyclopentadiene adducts of the former quinones and subsequent retro-Diels-Alder reaction. The Claisen rearrangement of 2,2-dimethoxy-5-methylphenyl allyl ethers and related crown ethers affords ortho- and para-allyl-substituted phenols (3:1) that are oxidized to give bisnorubiquinone derivatives and their ortho-quinone isomers. All new compounds are characterized by high resolution NMR and mass spectrometry.
- Merz,Rauschel
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p. 797 - 802
(2007/10/02)
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- Reactive dyestuffs
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Triphendioxazine reactive dyestuffs of the general formula STR1 with the substituent definition given in the description, are outstandingly suitable for dyeing and printing materials containing hydroxyl groups or amide groups. They give red dyeings with high wet- and light-fastnesses.
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- STRUCTURES OF PRODUCTS OF THE REACTION OF 2,3-DIMETHOXY-5-METHYLHYDROQUINONE WITH NONYL ALCOHOL OVER A HIGH-SILICON ALUMINOSILICATE
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By the reaction of 2,3-dimethoxy-5-methylhydroquinone with nonyl alcohol in presence of a high-silicon aluminosilicate 2,3-dimethoxy-6-methyl-4-(nonyloxy)phenol and 2,3-dimethoxy-6-methyl-5-nonylphenol are formed.
- Kozhukhova, A. I.,Filippova, T. M.,Obol'nikova, E. A.,Samokhvalov, G. I.,Margulis, M. A.
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p. 533 - 535
(2007/10/02)
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- Electron Paramagnetic Resonance, ENDOR and TRIPLE Resonance Studies on Substitution Reactions of 2-Methyl-1,4-benzoquinone and 2,3-Dimethoxy-5-methyl-1,4-benzoquinone in Alkaline Methanol
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Substitution of 2-methyl-1,4-benzoquinone wih methanol takes place in alkaline methanol, giving rise to methoxy-substituted methyl-1,4-benzoquinone radical anions.The relative signs and absolute values of the hyperfine coupling constants (hfcs) of the various mono-, di- and tri-substituted methoxymethyl-1,4-benzoquinones have been measured by EPR, ENDOR and TRIPLE resonance spectroscopy.The hfcs of OCH3 and CH3 protons had the same positive sign, except in the 3,5-dimethoxy-2-methyl-1,4-benzoquinone radical anion.The ENDOR signals of the methoxy protons could be distinguished from the methyl proton signals by using perdeuterated methanol as solvent.Partial optimization of the geometry of the radicals were performed by using the unrestricted MNDO method.In the most stable conformers the methoxyl groups had twisted out of the aromatic plane.INDO calculations were performed by using optimized structures, and the hfcs were compared with those obtained using standard bond lengths and angles.The hfcs of the ring protons were assigned by McLachian calculations and support of the assignment was provided by the additivity relationship method.The general TRIPLE technique allowed identification of the methyl, methoxy and ring protons of the different methoxy-substituted methyl-1,4-benzoquinone radical anions.
- Kasa, S.,Maekelae, R.,Salo, E.,Hannonen, K.,Joela, H.
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p. 3163 - 3170
(2007/10/02)
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- A new synthetic route to ubiquinones
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Ubiquinones 11 have been prepared employing a new strategy: as key step, the Diels-Alder reaction of 1,1,2-trichloroethene 3 with 2,5-bis[(trimethylsilyl)oxy]-3- methylfuran (2) has been used for the construction of the quinone part. After methanolysis of the [4 + 2] adducts 4a/4b, further reaction with cyclopentadiene and substitution of the Cl-atoms by MeO groups, the intermediate 7 is obtained. Diketone 7 can easily be alkylated with the desired polyprenyl side chain 9 (X = Br) using a strong base to yield, after a retro-Diels-Alder reaction, the corresponding ubiquinones 11 in high yields.
- Ruttimann,Lorenz
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p. 790 - 796
(2007/10/02)
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- Rearrangements of cyclobutenones. Synthesis of benzoquinones from 4-alkenyl-4-hydroxycyclobutenones
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The rearrangement of 4-alkenyl-4-hydroxycyclobutenones to quinones and related aromatic compounds is described. This rearrangement is complimentary to the previously reported ring expansions of 4-aryl- and 4-alkynyl-4-hydroxycyclobutenones. The synthetic scope and utility of the reaction are discussed. It is employed as a key step in the synthesis of a number of benzoquinones as well as in the total synthesis of the natural product, (±)-O-methylperezone and its regioisomer, (±)-O-methylisoperezone as well as coenzyme Q0 and aurantiogliocladin.
- Perri, Steven T.,Moore, Harold W.
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p. 1897 - 1905
(2007/10/02)
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- Oxidation of Methoxy- and/or Methyl-Substituted Benzenes and Naphthalenes to Quinones and Phenols by H2O2 in HCOOH
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The oxidation of a number of arenes (methoxybenzenes, methylbenzenes, and naphthalenes) to quinones and phenols by H2O2 in HCOOH has been examined.Methoxybenzenes were much more easily oxidized to p-benzoquinones than methylbenzenes (e.g., 1,3,5-trimethoxybenzene was oxidized to 2,6-dimethoxy-p-benzoquinone in a 75percent yield and 1,2,4-trimethylbenzene to 2,3,5-trimethyl-p-benzoquinone in a 16percent yield).Electron-withdrawing substituents, such as nitro, cyano, and chloro groups, lowered the conversion of reactants and changed the product selectivity from quinones to phenols.Methoxybenzonitriles were oxidized to corresponding phenols in a moder ate yield (e.g., 2,6-dimethoxybenzonitrile to 3-hydroxy-2,6-dimethoxybenzonitrile in a 39percent yield and a 64percent selectivity).
- Orita, Hideo,Shimizu, Masao,Hayakawa, Takashi,Takehira, Katsuomi
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p. 1652 - 1657
(2007/10/02)
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- Reductive Lactonization of Strategically Methylated Quinone Propionic Acid Esters and Amides
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It has been shown that the reduction of quinone propionic acid esters or amides bearing three methyl groups in the so-called "trialkyl lock" positions (o-, β-, β-positions) is accompanied by spontaneous lactonization with the release of alcohol or amine, respectively.A new convenient method is reported for introducing the β,β-dimethylpropionic acid side chain onto an appropriate hydroquinone nucleus via alkylative cyclization in methanesulfonic acid.Oxidation of the resulting lactone gives the quinone propionic acid, which can be converted by normal techniques to the corresponding ester or amide derivative.Initial model studies were carried out on pentamethylated systems 6 and 7.In order to make available quinones of varying redox potential or enhanced solubility in physiological media, methoxy- and amino-substituted quinones 10a, 10b, and 17a,b were synthesized.Upon reduction under mild conditions (Na2S2O4), all model esters or amides underwent reductive cyclization with loss of alcohol or amine.In the case of 7a the intermediate hydroquinone 19 could be isolated and its conversion to 4 with ejection of diethylamine followed by NMR techniques
- Carpino, Louis A.,Triolo, Salvatore A,Berglund, Richard A
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p. 3303 - 3310
(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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- Total Synthesis of Linear Polyprenoids. 2. Improved preparation of the Aromatic Nucleus of Ubiquinone
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Highly efficient copper-catalyzed polymethoxylation of tribromocresol is the key process in a three-step, practical approach to obtain ubiquinone 0 from p-cresol.Short syntheses of several ubiquinones were achieved via direct, copper-mediated coupling of 2-lithio-3,4,5,6-tetramethoxytoluene to the appropriate polyprenyl bromide.
- Keinan, Ehud,Eren, Doron
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p. 3872 - 3875
(2007/10/02)
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- Triphendioxazine dyestuffs
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Triphendioxazine dyestuffs of the formula STR1 having the substituent meanings specified in the descriptive part, are highly suitable for dyeing and printing hydroxyl- or amido-containing materials, in particular fibre materials, and produce wash-fast dyeings and prints.
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- COPPER-CATALYZED AEROBIC OXIDATION OF METHOXYPHENOLS
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A variety of methoxyphenols were selectively converted methoxy-p-benzoquinones by the use of copper-catalyzed aerobic oxidation.
- Matsumoto, Masakatsu,Kobayashi, Hisako,Hotta, Yasushi
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p. 515 - 520
(2007/10/02)
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- An Efficient Stereoselective Synthesis of Co-enzyme Q10
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Co-enzyme Q10 was efficiently synthesised by stereo- and regio-selective prenylation of the protected hydroquinone (2) with isoprene epoxide and solanesyl p-tolyl sulphone in a good overall yield.
- Sato, Kikumasa,Miyamoto, Osamu,Inoue, Seiichi,Yamamoto, Tomoya,Hirasawa, Yukihiko
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p. 153 - 154
(2007/10/02)
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- Ubiquinones and Related Compounds, XXXV. On Peracid Oxidation of 1-(Methoxy)-2,3-dimethoxy-5-methylbenzene
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The mechanism of the peracid oxidation of 1,2,3-trimethoxy-5-methylbenzene leading to 2,3-dimethoxy-5-methyl-1,4-benzoquinones has been investigated using 18O.The oxygen at the 1-position in the benzoquinone obtained originates from the oxidizing agent.
- Morimoto, Hiroshi,Hayashi, Nobuyoshi,Kawakami, Takeo
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p. 1963 - 1966
(2007/10/02)
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- A Novel Synthesis of 2,3-Dimethoxy-5-methyl-p-benzoquinone
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2,3-Dimethoxy-5-methyl-p-benzoquinone (3), an important intermediate in the synthesis of ubiquinones (1), was synthesized from 3,4,5-trimethoxysalicylic acid (6) or 2,3,4-trimethoxybenzaldehyde (9). 6 was reduced via the ethoxycarbonyl derivative (7) to 6-methyl-2,3,4-trimethoxyphenol (8) with sodium borohydride, and then 8 was oxidized to 3 in high yield with ferric chloride.On the other hand, 2,3,4-trimethoxyphenol (10) was obtained from 9 by the Baeyer-Villiger reaction or treatment with hydrogen peroxide under acidic or basic conditions, and then converted into 8 by reductive methylation.Sodium borohydride reduction of the Mannich base (11) of 10 also gave 8.Keywords - 2,3-dimethoxy-5-methyl-p-benzoquinone; ubiquinones; 3,4,5-trimethoxysalicylic acid; 2,3,4-trimethoxybenzaldehyde; 6-methyl-2,3,4-trimethoxyphenol; 2,3,4-trimethoxyphenol; 6-(N,N-dimethylamino)methyl-2,3,4-trimethoxyphenol; sodium borohydride reduction; reductive methylation
- Minami, Norio,Kijima, Shizumasa
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p. 1648 - 1650
(2007/10/02)
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