- New heterogeneous catalysts for greener routes in the synthesis of fine chemicals
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New strong Lewis acid SnTf-MCM-41 and SnTf-UVM-7 catalysts with unimodal and bimodal pore systems were prepared in a two-step synthesis in which the triflic acid (Tf) was incorporated to previously synthesized mesoporous tin-containing silicas. The Sn incorporation inside the pore walls was carried out through the Atrane method. The SnTf-UVM-7 catalysts were prepared by aggregating nanometric mesoporous particles defining a hierarchic textural-type additional pore system. Following these procedures, catalysts with different Si/Sn ratios-21.8 to 50.8 for SnTf-MCM-41 and 18.4 for SnTf-UVM-7-were prepared. These new materials were tested in the acylation of aromatic sulfonamides using acetic acid as the acylating agent and in the synthesis of (dl)-[α]-tocopherol through the condensation of 2,3,6-trimethylhydroquinone (TMHQ) with isophytol (IP). The activity data indicate that these heterogeneous catalysts are very active, corresponding to high yields in acylated compounds as 65.5% and very high selectivity to (dl)-[α]-tocopherol (94%, for a conversion of 98%).
- Coman, Simona M.,Pop, Georgeta,Stere, Cristina,Parvulescu, Vasile I.,El Haskouri, Jamal,Beltrán, Daniel,Amorós, Pedro
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- Structure-activity relationship and mechanism of the tocopherol- regenerating activity of resveratrol and its analogues
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The present study investigated the mechanism of the synergistic antioxidant activity of α-tocopherol with resveratrol (3,5,4′-trihydroxy-trans- stilbene, 3,5,4′-THS) and its synthetic analogues, that is, 3,4-dihydroxy-trans-stilbene (3,4-DHS), 4,4′-dihydroxy-trans-stilbene (4,4′-DHS), 4-hydroxy-trans-stilbene (4-HS), and 3,5-dihydroxy-trans- stilbene (3,5-DHS). The reaction kinetics of α-tocopheroxyl radical with resveratrol and its analogues were studied in sodium dodecyl sulfate (SDS) and cetyl trimethylammonium bromide (CTAB) micelles using the stopped-flow electron paramagnetic resonance (EPR) technique. It was found that resveratrol and its analogues could regenerate α-tocopherol with rate constants (k REG) in the order of 3,4-DHS > 4,4′-DHS > resveratrol ≥ 4-HS ≥ 3,5-DHS in SDS and CTAB micelles. It was found that the analogues bearing o-dihydroxyl groups (3,4-DHS) and p-dihydroxyl groups (4,4′-HS) exhibited remarkably higher α-tocopherol-regenerating activity than those bearing no such groups (resveratrol, 4-HS, and 3,5-DHS). In addition, the α-tocopherol-regenerating activity of resveratrol and its analogues was correlated with their electrochemical behaviors, suggesting that electron transfer might play a critical role during the regeneration reaction.
- Fang, Jian-Guo,Bo, Zhou
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- Synthesis of (all-rac)-α-tocopherol in supercritical carbon dioxide: Tuning of the product selectivity in batch and continuous-flow reactors
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α-Tocopherol was synthesized using a condensation reaction of 2,3,6-trimethylhydroquinone with isophytol in supercritical CO2 using batch and continuous-flow reactors. In the batch reaction catalyzed by a fluorinated molecular catalyst bearing strong Bronsted acidity, C 6F5CHTf2 (Tf=SO2CF3), an increase in the CO2 pressure causes a marked increase in the product selectivity for α-tocopherol, albeit with a slight decrease in the product yield. The solubility measurements by extraction experiments and the supercritical fluid NMR (scNMR) indicate that the homogeneous and non-polar reaction phase in scCO2 is crucial to obtain α-tocopherol with high selectivity. A continuous flow scCO2 process for the condensation reaction can be performed with a strong acid resin, Amberlyst 15, as a solid acid catalyst to give the desired product with high selectivity.
- Kokubo, Yoshiaki,Hasegawa, Aiko,Kuwata, Shigeki,Ishihara, Kazuaki,Yamamoto, Hisashi,Ikariya, Takao
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- SYNTHESIS OF CHROMANOL DERIVATIVES
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The present invention relates to a process for the production of chromanol derivatives, more specifically to a process for preparing a compound of the general formula I wherein R1, R2 and R3 independently of each other are selected from hydrogen and methyl, R4 is selected from C-1-C6-alkyl, and X is selected from C1-C20-alkyl and C2-C20-alkenyl.
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Page/Page column 40-41
(2020/03/05)
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- SYNTHESIS OF CHROMANOL DERIVATIVES
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The present invention relates to a process for the production of chromanol derivatives, more specifically to a process for preparing a compound of the general formula (I) wherein R1, R2 and R3 independently of each other are selected from hydrogen and methyl, R4 is selected from hydrogen and C1-C6-alkanoyl, and X is selected from C1-C20-alkyl and C2-C20-alkenyl.
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Page/Page column 42
(2020/03/05)
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- Process of separating chiral isomers of chroman compounds and their derivatives and precursors
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The present invention relates to a process of separating chiral isomers of chroman compounds, particularly tocopherols and tocotrienols as well as the esters and intermediates thereof. It has been found that this process allows a separation of the desired isomer with a higher yield and enables the use of the non-desired isomers in a very efficient way. Said process is particularly useful when implemented in an industrial process. Furthermore, it has been found that this process allows using isomer mixtures as they result from traditional industrial synthesis.
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Page/Page column 14
(2012/12/13)
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- MANUFACTURE OF α-TOCOPHEROL
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A process for the manufacture of (all- rac)-α-tocopherol by the acid-catalyzed reaction of trimethylhydroquinone with isophytol or phytol is characterized by carrying out the reaction in the presence of methane trisulphonate as the catalyst in an organic solvent. The product of the process is the most active and industrially most important member of the vitamin E group.
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- Preparation and reactions of 5-nitromethyl-γ-tocopherol acetate
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Nitration of α-tocopherol acetate 1b yielded 5-nitromethyl-γ-tocopherol acetate 2b. The acetate 2b was converted to free phenol 2a by transesterification in methanol. Reduction of 2b by NaBH4 in ethyl acetate and methanol gave 5-(2-hydroxypropyl)-γ-tocopherol 5a and 5-methoxymethyl-γ-tocopherol 6 respectively.
- Witkowski,Markowska,Walejko
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p. 449 - 453
(2007/10/03)
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- Electron-transfer reactions of alkyl peroxy radicals
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One-electron-transfer reactions of alkyl peroxy radicals were studied by pulse radiolysis of aqueous solutions. At pH 13, the methyl peroxy radical was found to rapidly, k = 1 × 105-4.9 × 107 s-1, and quantitatively oxidize various organic substrates with E13 = 0.13-0.76 V vs NHE. On the other hand, this radical was unreactive with compounds with E13 ≥ 0.85 V. Consequently, E13 of the methyl peroxy radical is higher than 0.76 V and lower than 0.85 V, which means that E7 is in the range 1.02-1.11 V. At pH 8, the rate constants of the oxidation of four ferrocene derivatives by the alkyl peroxy radicals ranged from 7.1 × 104 M-1 s-1 for ferrocenedicarboxylate (E8 = 0.66 V) to 2.3 × 106 M-1 s-1 for (hydroxymethyl)ferrocene (E8 = 0.42 V). These rate constants were used to evaluate the reduction potential and self-exchange rate of alkyl peroxy radicals in neutral media from the Marcus equation. The calculated E7 = 1.05 V is in excellent agreement with the estimated E7 = 1.02-1.11 V and with one of the perviously published values E7 = 1.0 V, but the value is in excellent agreement higher than the other E7 ～ 0.6 V. It is suggested that the high reorganization energy, λ = 72 kcal mol-1 redox couple originates from the requirement for solvent reorganization due to the solvation of hydroperoxide anion in the transition state. In support of this are the activation parameters of the reaction of the methyl peroxy radical with uric acid. The activation entropy is 9 eu lower at pH 7.3 than it is at pH 13.2, whereas the activation enthalpies are unchanged. The importance of entropy control was verified in the reactions of cyclohexyl peroxy radicals with α- and δ-tocopherol in aerated cyclohexane (ΔH+ ≈ 0 kcal/mol, and ΔS+ = -25 and -26 eu). The implications of these findings on the inactivation of alkyl peroxy radicals in general are discussed.
- Jovanovic, Slobodan V.,Jankovic, Ivana,Josimovic, Ljubica
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p. 9018 - 9021
(2007/10/02)
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- Addition of Diazomethane to α-Tocopherolquinone
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The reaction of α-tocopherolquinone (3a) and its derivatives (3c,d) with diazomethane was investigated.As the result of its addition to the >C1=O group the spiroepoxycyclohexadienones 5a, b, and c were formed.By catalytic reduction (Pd/C) compound 5a was transformed into the phenol 7.In the presence of BF3*Et2O, compound 5a was cyclized to α-tocopherol (2a).
- Witkowski, Stanislaw,Poplawski, Janusz
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p. 205 - 211
(2007/10/02)
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- Electron Transfer Reactions of Halothane-derived Peroxyl Free Radicals, CF3CHClO2.: Measurement of Absolute Rate Constants by Pulse Radiolysis
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The halothane-derived peroxyl radical CF3CHClO2. has been generated in aqueous solutions by pulse radiolysis.Absolute rate constants for the reduction of halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) by hydrated electrons, hydrogen atoms, and propan-2-ol free radicals have been determined to be k 1.4E10, 3.8E8, and 7.6E7 l mol-1 s-1, respectively.The predominant product radical CF3CHCl rapidly adds O2, and an estimate of k 1.3E9 l mol-1 s-1, has been obtained for the absolute rate constant of this reaction.The resulting peroxyl radical CF3CHClO2. has been found to react rapidly with a variety of nucleophilic compounds such as 2,2'-azinobis(3-ethylbenzthiazoline-6-sulphonate), the phenothiazines promethazine, chlorpromazine, and metiazinic acid, the vitamins C and E, and propyl gallate.The absolute rate constants for these reactions are found to be generally lower than for corresponding reactions of the carbon tetrachloride-derived radical, CCl3O2..
- Moenig, Joerg,Asmus, Klaus-Dieter,Schaeffer, Michel,Slater, Trevor F.,Willson, Robin L.
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p. 1133 - 1138
(2007/10/02)
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