- 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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- Total synthesis of (±)-antroquinonol D
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Total synthesis of (±)-antroquinonol D, which is isolated from very expensive and rarely found Antrodia camphorata and which has potential anticancer properties, was achieved from 4-methoxyphenol. In addition, a Michael addition to dimethoxy cyclohexadien
- Sulake, Rohidas S.,Jiang, Yan-Feng,Lin, Hsiao-Han,Chen, Chinpiao
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p. 10820 - 10828
(2015/01/08)
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- Synthesis of coenzyme Q10
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A practical synthesis of coenzyme Q10 has been developed. The route features an improved Friedel-Crafts allylation of tetramethoxytoluene with a para-chlorobenzenesulfonyl-substituted C5 allylic chloride at 40 °C. Replacement of the methyl ether protecting groups of the para-hydroquinone by methoxymethyl groups at Q1 stage proceeded efficiently, and allowed the facile final oxidation to coenzyme Q10 to occur under mild acidic conditions. The overall yield of coenzyme Q 10 from commercially available tetramethoxytoluene reached 53 % in this improved procedure. An improved synthesis gave CoQ10 in 53 % overall yield from tetramethoxytoluene through Friedel-Crafts allylation with a para-chlorobenzenesulfonyl-substituted C5 allylic chloride and a modified oxidation procedure. Copyright
- Oh, Eun-Taek,Taek Oh, Jung,Koo, Sangho,Jin Kim, Hee,Su, Liang,Yun, Inkyun,Nam, Kyunggu,Min, Jae-Hong,Woo Kim, Joon
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p. 4954 - 4962,9
(2020/08/24)
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- Alternative synthesis of 5-chloromethyl-2,3-dimethoxy-6-methyl-1, 4-benzoquinone: A key intermediate for preparing coenzyme Q analogues
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The title compound, a key intermediate for preparing Coenzyme Qn family, was prepared in high yield by a reaction sequence starting from the commercially available 3, 4, 5-trimethoxy-benzadehyde via Wolff-Kishner reduction, Vilsmeier-Haack reaction, Blanc chloromethylation reaction, Dakin reaction and oxidation.
- Wang, Jin,Yang, Jian,Yang, Bo,Sun, Jia-Qiang,Yang, Tao
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p. 724 - 725
(2011/04/24)
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- An alternative route for the synthesis of 2,3,4,5-tetramethoxytoluene
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The transformation of the commercially available 2,3,4- trimetho×ybenzaldehyde to 2,3,4,5-tetrametho×ytoluene using a Dakin reaction to insert the extra oxygen, formylation, reduction and methylation of the phenolic hydro×yl group is described.
- Vera, William J.,Chinea, Kimberly,Banerjee, Ajoy K.
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experimental part
p. 186 - 187
(2009/10/15)
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- Reaction of phenols with the 2,2-diphenyl-1-picrylhydrazyl radical. Kinetics and DFT calculations applied to determine ArO-H bond dissociation enthalpies and reaction mechanism
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(Figure Presented) The formal H-atom abstraction by the 2,2-diphenyl-1-picrylhydrazyl (dpph?) radical from 27 phenols and two unsaturated hydrocarbons has been investigated by a combination of kinetic measurements in apolar solvents and density functional theory (DFT). The computed minimum energy structure of dpph? shows that the access to its divalent N is strongly hindered by an ortho H atom on each of the phenyl rings and by the o-NO2 groups of the picryl ring. Remarkably small Arrhenius pre-exponential factors for the phenols [range (1.3-19) × 105 M-1 s-1] are attributed to steric effects. Indeed, the entropy barrier accounts for up to ca. 70% of the free-energy barrier to reaction. Nevertheless, rate differences for different phenols are largely due to differences in the activation energy, Ea,1 (range 2 to 10 kcal/mol). In phenols, electronic effects of the substituents and intramolecular H-bonds have a large influence on the activation energies and on the ArO-H BDEs. There is a linear Evans-Polanyi relationship between E a,1 and the ArO-H BDEs: Ea,1/kcal x mol-1 = 0.918 BDE(ArO-H)/kcal x mol-1 - 70.273. The proportionality constant, 0.918, is large and implies a "late" or "product-like" transition state (TS), a conclusion that is congruent with the small deuterium kinetic isotope effects (range 1.3-3.3). This Evans-Polanyi relationship, though questionable on theoretical grounds, has profitably been used to estimate several ArO-H BDEs. Experimental ArO-H BDEs are generally in good agreement with the DFT calculations. Significant deviations between experimental and DFT calculated ArO-H BDEs were found, however, when an intramolecular H-bond to the O? center was present in the phenoxyl radical, e.g., in ortho semiquinone radicals. In these cases, the coupled cluster with single and double excitations correlated wave function technique with complete basis set extrapolation gave excellent results. The TSs for the reactions of dpph ? with phenol, 3- and 4-methoxyphenol, and 1,4-cyclohexadiene were also computed. Surprisingly, these TS structures for the phenols show that the reactions cannot be described as occurring exclusively by either a HAT or a PCET mechanism, while with 1,4-cyclohexadiene the PCET character in the reaction coordinate is much better defined and shows a strong π-π stacking interaction between the incipient cyclohexadienyl radical and a phenyl ring of the dpph? radical.
- Foti, Mario C.,Daquino, Carmelo,Mackie, Iain D.,DiLabio, Gino A.,Ingold
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experimental part
p. 9270 - 9282
(2009/04/07)
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- New efficient synthesis of ubiquinones
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A strategy for the ecofriendly and high-yielding synthesis of ubiquinones starting from simple materials and using mild conditions is reported. CoQ1, CoQ2, CoQ3, and CoQ9 were prepared. Copyright Taylor & Francis Group, LLC.
- Bovicelli, Paolo,Borioni, Giorgio,Fabbrini, Danilo,Barontini, Maurizio
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p. 391 - 400
(2008/04/01)
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- Radical-scavenging polyphenols: New strategies for their synthesis
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New strategies for the synthesis of polyphenols, compounds with antioxidant properties contained in every kind of plants, are discussed. Syntheses of different classes of polyphenols, namely ubiquinones, present in many natural systems in which electron-transfer mechanisms are involved, hydroxytyrosol, one of the main components of the phenol fraction in olives, and flavonoids, widespread in the plant kingdom, were approached by simple and environmentally sustainable methods.
- Bovicelli, Paolo
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p. 1703 - 1710
(2008/03/11)
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- Practical synthesis of 2,3,4,5-tetramethoxytoluene
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The title compound, a key material for synthesis of coenzyme Q 10 , was effectively prepared in high yield by a reaction sequence starting from 3,4,5-trimethoxybenzadehyde via Wolff-Kishner reduction, Vilsmeier-Haack reaction, Dakin reaction, and methylation. Copyright Taylor & Francis Group, LLC.
- Ji, Yafei,Xu, Wanmei,Jin, Wenhu,Weimin, Yue
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p. 1961 - 1965
(2007/10/03)
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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 1-METHYL ETHERS OF UBIQUINOLS
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A two-stage method was developed for the synthesis of 1-methyl ethers of ubiquinols, having various isoprenoid chain lengths, from 2,3-dimethoxy-5-methylhydroquinone.
- Kozhukhova, A. I.,Obol'nikova, E. A.,Kozlova, I. V.,Bekker, A. R.,Filippova, T. M.,Samokhvalov, G. I.
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p. 2024 - 2026
(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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