- Selective Dehydration of Mannitol to Isomannide over Hβ Zeolite
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Isomannide is a potential feedstock for the production of super engineering plastics. A prospective route to obtain isomannide is dehydration of mannitol derived from lignocellulosic biomass, but homogeneous acid catalysts reported in the literature produce a large amount of 2,5-sorbitan as a byproduct in the dehydration reaction. In this work, we initially studied the mechanism of proton-induced dehydration of mannitol by density functional theory calculations, which suggested that local steric hindrance around acid sites designed at the angstrom level can tune the selectivity toward isomannide formation. Based on this prediction, we found that the precisely defined microporous confinement offered by Hβ provides improved selectivity and high catalytic activity for the production of isomannide, where 1,4-dehydration is favored by 20 kJ mol-1 of activation energy. The optimization of the Si/Al ratio of Hβ to balance the acid amount and hydrophobicity improved the catalytic activity and achieved 63% yield of isomannide, far exceeding the best result reported previously (35% yield).
- Yokoyama, Haruka,Kobayashi, Hirokazu,Hasegawa, Jun-Ya,Fukuoka, Atsushi
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- Kinetic analyses of intramolecular dehydration of hexitols in high-temperature water
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Intramolecular dehydration of the biomass-derived hexitols D-sorbitol, D-mannitol, and galactitol was investigated. These reactions were performed in high-temperature water at 523–573 K without added acid catalyst. The rate constants for the dehydration steps in the reaction networks were determined at various reaction temperatures, and the activation energies and pre-exponential factors were calculated from Arrhenius plots. The yield of each product was estimated as a function of reaction time and temperature using the calculated rate constants and activation energies. The maximum yield of each product from the dehydration reactions was predicted over a range of reaction time and temperature, allowing the selective production of these important platform chemicals.
- Yamaguchi, Aritomo,Mimura, Naoki,Shirai, Masayuki,Sato, Osamu
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- Selective C?O Bond Cleavage of Sugars with Hydrosilanes Catalyzed by Piers’ Borane Generated In Situ
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Described herein is the selective reduction of sugars with hydrosilanes catalyzed by using Piers’ borane [(C6F5)2BH] generated in situ. The hydrosilylative C?O bond cleavage of silyl-protected mono- and disaccharides in the presence of a (C6F5)2BH catalyst, generated in situ from (C6F5)2BOH, takes place with excellent chemo- and regioselectivities to provide a range of polyols. A study of the substituent effects of sugars on the catalytic activity and selectivity revealed that the steric environment around the anomeric carbon (C1) is crucial.
- Zhang, Jianbo,Park, Sehoon,Chang, Sukbok
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supporting information
p. 13757 - 13761
(2017/10/09)
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- Enhanced catalytic performance in dehydration of sorbitol to isosorbide over a superhydrophobic mesoporous acid catalyst
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A superhydrophobic mesoporous polymer-based acid catalyst (P-SO3H) was synthesized from solvothermal co-polymerization. The N2 sorption isotherms indicate the rich porosity of P-SO3H, confirmed by the TEM image. The IR spectra indicate the presence of sulfonic acid groups. Interestingly, P-SO3H gives contact angle of water droplet on the sample surface at 154°, suggesting its superhydrophobicity. More importantly, P-SO3H is highly efficient catalyst for dehydration of sorbitol to isosorbide, giving sorbitol conversion higher than 99.0% and isosorbide yield at 87.9%. In addition, P-SO3H exhibits excellent recyclability. After recycles for 5 times, the isosorbide yield is still 77.7%. In contrast, conventional acid catalyst of Amberlyst-15 shows the yield at only 15.4% after recycles for 3 times. The unique catalytic properties are reasonably related to the superhydrophobicity and porosity of P-SO3H. The sample large porosity offers a high degree of the exposed acidic sites to the reactants, and the sample superhydrophobicity would keep the water formed in the dehydration away from the catalyst, promoting the reaction equilibrium. As a result, the catalytic performance in dehydration of sorbitol to isosorbide over the superhydrophobic P-SO3H catalyst is significantly enhanced, compared with conventional acid catalyst of Amberlyst-15.
- Zhang, Jian,Wang, Liang,Liu, Fujian,Meng, Xiangju,Mao, Jianxin,Xiao, Feng-Shou
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p. 249 - 254
(2015/02/19)
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- Intramolecular dehydration of mannitol in high-temperature liquid water without acid catalysts
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Intramolecular dehydration of mannitol in high-temperature liquid water without adding any hazardous acid catalysts and its kinetic analyses were carried out. The dehydration behavior of mannitol was compared with that of sorbitol. 2,5-Anhydromannitol and 1,4-anhydromannitol were major products from the mannitol monomolecular dehydration in contrast with the only major product, 1,4-anhydrosorbitol, from the sorbitol monomolecular dehydration.
- Yamaguchi, Aritomo,Sato, Osamu,Mimura, Naoki,Shirai, Masayuki
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p. 45575 - 45578
(2014/12/12)
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- Preparation of anhydroalditols from commodity carbohydrates
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A practical process for the preparation of anhydroalditols from commodity carbohydrates has been described. Reductive cleavage of the glycosidic linkage in perallylated carbohydrates with triethylsilane gave the protected anhydroalditols, which were then deallylated using a PdCl2-CuCl2-Activated Charcoal system. Valuable anhydroalditols, such as 1,5-anhydro-D-glucitol, 1,5-anhydro-D-mannitol, 2,5-anhydro-D-glucitol, 2,5-anhydro-D-mannitol and 1,4-anhydro-Dribitol, were prepared in high yields and purity from carbohydrates, such as glucose, mannose, ribose, sucrose, cellulose, starch and levan.
- Yuan, Changyou,Hollingsworth, Rawle I.
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- PROCESS FOR MAKING SUGAR AND/OR SUGAR ALCOHOL DEHYDRATION PRODUCTS
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A process is disclosed for making dehydration products from an aqueous sugars solution including pentoses, hexoses or both, for example, an aqeous high fructose corn syrup solution, or from an aqueous solution of one or more of the alcohols of such pentoses and hexoses, for example, from an aqueous sorbitol solution, by an acid-catalyzed dehydration using substituted sulfonic acids solubilized in the aqueous sugars or sugar alcohols solution.
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Paragraph 00129-00130
(2013/09/26)
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- The solvent-free thermal dehydration of hexitols on zeolites.
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Dehydration of galactitol, D-glucitol and D-mannitol at high temperature in the presence of molecular sieves without solvent under an argon atmosphere is described. Cyclodehydration products with retention or inversion of the configuration at asymmetric carbon atoms, were observed. Reaction of galactitol yielded racemic 1,4-anhydrogalactitol in a first step and then racemic 1,4:3,6-dianhydroiditol. Complete analytical separations of exhaustively O-acetylated reaction products were achieved by GC and structures were assigned using co-injection with standards.
- Kurszewska, Maria,Skorupowa, Eugenia,Madaj, Janusz,Konitz, Antoni,Wojnowski, Wieslaw,Wisniewski, Andrzej
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p. 1261 - 1268
(2007/10/03)
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- Acyloxonium ions in the high-yielding synthesis of oxolanes from alditols, hexoses, and hexonolactones catalysed by carboxylic acids in anhydrous hydrogen fluoride
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Treatment of D-glucono-1,5- or D-mannono-1,4-lactone with anhydrous hydrogen fluoride catalysed by formic or acetic acid yields 3,6-anhydro-D-glucono- and -D-mannono-1,4-lactone, respectively.Similarly, D-mannitol is converted into 1,4-anhydro-D-mannitol and subsequently into the 1,4:3,6-dianhydride, whereas D-glucitol forms exclusively the 3,6-anhydride and, on further reaction, 1,4:3,6-dianhydro-D-glucitol.D-Glucose and 2-acetamido-2-deoxy-D-glucose are also converted into the corresponding 3,6-anhydrides by reaction with hydrogen fluoride and formic acid.13C-N.m.r. spectroscopy indicates that the reactions involve intermediate dioxolanyium ions.
- Defaye, Jacques,Gadelle, Andree,Pedersen, Christian
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p. 191 - 202
(2007/10/02)
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- An Efficient Synthesis of Anhydroalditols and Allyl C-Glycosides
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Efforts to expedite production of anhydroalditols have led to a new, efficient synthesis of these compounds from alkyl glycosides.Silylation of the glycoside followed by reductive cleavage in the presence of triethylsilane and trimethylsilyl trifluoromethanesulfonate were carried out in the same reaction flask.Subsequent aqueous workup gave excellent yields of anhydroalditol(s).In some cases ring contraction was observed, but the use of bulkier silyl protecting groups gave greater yields of the expected product.This method was also shown to be an efficient means to prepare allyl C-glycosides, without any independent protecting or activating step, by simply replacing triethylsilane with allyltrimethylsilane in the synthetic scheme.
- Bennek, John A.,Gray, Gary R.
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p. 892 - 897
(2007/10/02)
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- THE CHEMICAL-TRANSFORMATION PRODUCTS OF 1,6-DIBROMO-1,6-DIDEOXYGALACTITOL AND 1,2:5,6-DIANHYDROGALACTITOL IN AQUEOUS SOLUTION
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After hydrolysis of 1,6-dibromo-1,6-dideoxygalactitol (1) and 1,2:5,6-dianhydrogalactitol (2), 11 compounds were isolated, three of them as tritylated derivatives.Their structures were established on the basis of chemical evidence and, for four compounds, by X-ray diffraction.The main product of the hydrolysis of 1 was 3,6-anhydro-1-bromo-1-deoxy-DL-galactitol; the end-products of the hydrolysis of 2 were 1,5-anhydro-DL-galactitol, 2,5-anhydro-DL-altriol and galactiotol.
- Vidra, Ildiko,Simon, Kalman,Institoris, Laszlo,Csoeregh, Ingeborg,Czugler, Matyas
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- Acid Catalyzed Dehydration of Alditols. Part I. D-Glucitol and D-Mannitol
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The acid catalyzed dehydration of D-glucitol and D-mannitol has been studied using 13C NMR spectroscopy to monitor the reactions.The products formed were identified and rate constants were measured.Dehydration of (1S)-1-2H-D-mannitol with 3 M sulfuric acid was shown to yield (1R)-1-2H-1,4:3,6-dianhydro-D-mannitol, showing that dehydration of D-mannitol to 1,4-anhydro-D-mannitol and, subsequently, to the 1,4:3,6-dianhydride takes place with inversion at the primary carbon atom.
- Bock, Klaus,Pedersen, Christian,Thoegersen, Henning
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p. 441 - 450
(2007/10/02)
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