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DMSO can improve the selectivity of 5-hydroxymethylfurfural (HMF) in the conversion of carbohydrates. However, one of the bottlenecks in its application is product separation. Thus a one-pot synthesis of 5-ethoxymethylfurfural (EMF) rather than HMF from fructose in ethanol-DMSO was investigated. Phosphotungstic acid was used as an effective catalyst. The yield of EMF can be reached as high as 64% in the mixed solvent system of DMSO and ethanol within 130 min at 140 °C. Ethyl levulinate (LAE) was detected as the main by-product, the yield of which increased with the reaction time, temperature and the amount of catalyst. In addition, the existence of water could significantly reduce the yield of EMF and increased the yield of LAE. Most importantly, it was discovered that EMF could be much more efficiently extracted from the reaction solvent system by some organic solvents than HMF., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

The direct synthesis of 2,5-diformylfuran (DFF) from fructose is a tandem reaction that typically involves two steps catalyzed by two different catalysts, including fructose dehydration to 5-hydroxymethylfurfural (HMF) catalyzed by an acid catalyst and subsequent HMF oxidation to DFF catalyzed by a redox catalyst. In this study, graphene oxide, a metal-free carbon based material, was demonstrated to be an efficient and recyclable bifunctional catalyst in the direct synthesis of DFF from fructose. A DFF yield of 53.0% was achieved in a one pot and one-step reaction (O2, 24 h) and the DFF yield could be further increased to 72.5% in a one pot and two-step reaction (N2, 2 h and O2 22 h). [ABSTRACT FROM AUTHOR]

The design of green heterogeneous catalysts for the efficient conversion of biomass into platform molecules is a key aim of sustainable chemistry. Graphene oxide prepared from Hummers oxidation of graphite was proven to be a green and efficient carbocatalyst for the dehydration of fructose into 5-hydroxymethylfurfural (HMF) in some three-carbon and four-carbon alcohol mediated solvent systems. HMF was obtained in up to 87 % yield in 90 vol % isopropanol-mediated DMSO solvent. Some control experiments and analytical data showed that a small number of sulfonic groups and abundance of oxygen-containing groups (alcohols, epoxides, carboxylates) have an important synergic effect in maintaining the high performance of graphene oxide. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The solid acid catalyst was prepared with waste polyurethane elastomer as precursor. • The tetrahydrofuran was reclaimed in preparation process of the catalyst. • The highest HMF yield of 70.1% was obtained in low-boiling solvent. • The 66.0% yield of EMF was observed when the solvent ratio of ethanol/1,4-dioxane equal to 70:30. Abstract Catalytic conversion of various carbohydrates into 5-hydroxymethylfurfural (HMF) and 5-ethoxymethylfurfural (EMF) was efficiently conducted by sulfonated carbon material (polyurethane based catalyst, abbreviated as PU-Cat). In the preparation process of catalyst, the tetrahydrofuran was reclaimed. PU-Cat exhibited excellent performance in the synthesis of HMF and EMF from fructose-based carbohydrates. Firstly, the dehydration of fructose into HMF was smoothly carried out in the low-boiling solvent (1, 4-dioxane), which was catalyzed by PU-Cat at 140 °C. The highest yield of HMF was up to 70.1% with full conversion of fructose in 1, 4-dioxane for 2 h. Then, the one-pot conversion of fructose into EMF was also successfully performed in the ethanol/1, 4-dioxane (V/V=70:30) at 140 °C for 2 h, and 66.0% yield of EMF was obtained. Finally, PU-Cat can be recycled five times without significant reduction in catalytic activity. [ABSTRACT FROM AUTHOR]

As counter parts of ILs, DESs have received general interest because of their comparable physicochemical properties to ILs and facile preparation from readily available chemicals. In this work, the isomeric distributions of fructose, glucose, xylose and GlcNAc in CCU, CCG and CCO, i.e. basic, neutral and acidic DES, have been determined by 13 C NMR. Higher furanose fraction of fructose was observed in CCO compared to CCG and CCU. The glucose was chosen as model compound to reveal the effect of DES on the mutarotation behavior with DMSO‑ d 6 as co-solvents. The experimental results showed that a high ratio of CCU to glucose speed up the mutarotation rate of glucose in DMSO‑ d 6 , but have little influence on the anomeric distribution. Furthermore, the mutarotation of glucose in DESs is mainly driven by the HBD, whereas HBA provides little influence. However, HBD and HBA display a synergistic effect on the glucose mutarotation process. Hydrogen bonding between hydrogen of amino in urea and oxygen of hydroxyl in glucose is the driving force for the interconversion of anomers. [ABSTRACT FROM AUTHOR]

The dehydration of fructose in aqueous and biphasic system was studied using heteropolyacids, immobilized in silica, as catalyst. The catalysts were characterized by ICP-AES, nitrogen sorption, NH 3 -TPD, TEM, FT-IR, XRD, and TGA. The effect of different parameters, such as reaction temperature, reaction time, catalyst loading and volume ratio of water with methyl isobutyl ketone (MIBK) was studied. Silica included tungstosilisic acid (HSiW) was found to function as an efficient catalyst for the transformation of fructose into 5-hydroxymethylfurfural in aqueous phase. Addition of MIBK into the reaction system can increase both of fructose conversion and HMF selectivity. Besides, MIBK showed a positive effect in increasing the stability of the catalyst by suppressing the formation and deposition of humins over catalyst surface. After the third catalysis cycles, a stabilization of the catalytic activity was observed. [ABSTRACT FROM AUTHOR]

In situ NMR, selective 1D TOCSY spectra and DFT have been used for analyzing reactive intermediates in fructose reactions, where fructose with diammonium hydrogen phosphate [(NH 4) 2 HPO 4 ] is consumed via a glucosamine intermediate (GlcNH 2) which is subsequently converted into deoxyfrutosazine (2,5-DOF). • In situ NMR and TOCSY spectra have been used for analyzing reactive intermediates. • Investigation discloses nitrogen firstly maps onto GlcNH 2 and then to DOF. • Calculations show the formation of GlcNH 2 is thermodynamics and kinetics feasible. In situ 13C and 1H NMR and selective 1D TOCSY spectra have been used for analyzing reactive intermediates in fructose conversion, where fructose with diammonium hydrogen phosphate [(NH 4) 2 HPO 4 ] is consumed via a glucosamine (GlcNH 2) intermediate. Our data indicate that the nitrogen in (NH 4) 2 HPO 4 maps onto the intermediate GlcNH 2 and subsequent to the corresponding product deoxyfructosazine (DOF). Pathways leading to isomerization of fructose have furthermore been identified through DFT calculations. The inclusion of solvent effects results in substantial reduction of the fructose ring-opening free energy barrier (19.4 kcal/mol). Interestingly, lower free energy barrier (21.0 kcal/mol) indicating that the formation of intermediate GlcNH 2 is both thermodynamically and kinetically accessible in agreement with the experimental results. Yield of DOF reaches 46% under the optimized conditions. [ABSTRACT FROM AUTHOR]

A chemical formula showing graphene oxide catalyzed dehydration of fructose into 5-hydroxymethylfulfural with isopropanol as cosolvent is presented.