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We show that the coating of choline chloride on silica-supported AlCl3 allows the dehydration of carbohydrates to successfully proceed in low boiling point organic solvents. The concept is based on the in situ formation of a deep eutectic liquid phase on the catalyst surface, thus facilitating the interaction between the solid catalyst and insoluble carbohydrate., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The one-pot production of industrially valuable diketone derivatives from carbohydrates is achieved through a bifunctional catalytic process. In particular, Pd/C-catalyzed hydrogenation of HMF in water and under CO2 affords 1-hydroxypentane-2,5-dione with up to 77% yield. The process is also eligible starting from fructose and inulin, affording 1-hydroxyhexane-2,5-dione with 36% and 15% yield, respectively. The key of the process is reversible in situ formation of carbonic acid, which is capable of assisting Pd/C during the hydrogenation reaction by promoting the dehydration of carbohydrates and the ring-opening of furanic intermediates. Interestingly, by changing the reaction medium from H2 O to a H2 O/THF mixture (1:9), it is possible to switch the selectivity of the reaction and to produce 2,5-hexanadione with 83% yield. Within the framework of sustainable chemistry, reactions presented in this report show 100% carbon economy, involve CO2 to generate acidity, require water as a solvent, and are conducted under rather low hydrogen pressures (10 bar)., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

1‐(5‐(Hydroxymethyl)furan‐2‐yl)‐5‐methylhex‐1‐en‐3‐one was prepared from cellulose or glucose by a sequence of depolymerization/dehydration/aldol condensation reactions. The synthesis of HMF was first performed starting from a highly concentrated feed of glucose and cellulose (31 wt.%) using choline chloride in MIBK/water biphasic media via the formation of a glucoside intermediate. Next, the aldol condensation of HMF with MIBK was investigated over alkaline metal oxides. Among the catalysts used, commercial BaO was highly efficient with a yield of aldol product above 90 %. Under air, BaO instantaneously transformed into Ba(OH)2, H2O and BaO2 which are regarded as active phases for the reaction. The catalyst basicity and solvent were key parameters to govern the selectivity of the reaction by limiting secondary reactions. [ABSTRACT FROM AUTHOR]

An efficient method has been developed to synthesize end-functionalized oligosaccharides from unprotected monosaccharides in a one-pot/two-step approach. In the first step, mannose (and glucose) was functionalized with an alkyne group at the anomeric position through the Fisher-glycosylation reaction with propargyl alcohol as a glycosyl acceptor. In the second step, the functionalized monosaccharides were oligomerized and the experimental conditions were optimized by varying the temperature, time and the molar ratio between alcohol and sugar to reach a up to 8. The obtained oligosaccharides showed complete propargylation at their reducing chain-end and were successfully coupled to oleic acid via the Huisgen reaction, affording bio-based surfactants. [ABSTRACT FROM AUTHOR]

Abstract: The irradiation of concentrated feeds of carbohydrates in alcoholic solution by high‐frequency ultrasound (550 kHz) induces the formation of alkylpolyglycosides (APGs). This work is distinct from previous reports in that it does not involve any (bio)catalyst or activating agent, it takes place at only 40 °C, thus avoiding degradation of carbohydrates, and it selectively yields APGs with a degree of polymerization in a window of 2–7, an important limitation of the popular Fischer glycosylation. This ultrasound‐based technology proved successful with a range of different valuable carbohydrates and alkyl alcohols. The elucidation of the structure of all the produced glycosides strongly suggests that 1,6‐anhydrosugars formed in situ are key intermediate species. [ABSTRACT FROM AUTHOR]

The synthesis of furanic derivatives (5-hydroxymethylfurfural (HMF), furfural . . .) from carbohydrates is of high interest for a wide range of applications. These reactions are carried out in the presence of various solvents, and among them choline chloride can be used. It is a salt that can form a low melting mixture with a carbohydrate (fructose, glucose . . .) or a deep eutectic mixture with carboxylic acid. A review of the studies performed in the conversion of carbohydrates to furanic derivatives in the presence of choline chloride is presented here with the advantages and drawbacks of this solvent. Choline chloride can enhance the selectivity to HMF by stabilizing effect and allows the conversion of highly concentrated feed. However, the extraction of the products from these solvents still needs improvement. [ABSTRACT FROM AUTHOR]

Non-thermal atmospheric plasma (NTAP) is a physical technology that has been previously employed for surface treatment (cleaning, coating, erosion, etc.) and water or air depollution. We show here that, beyond surface effects, NTAP is capable of enabling the complete and fast polymerization of various mono- and disaccharides in the solid state within only a few minutes and at low temperature (40–80 °C). NTAP-induced polymerization involves a radical mechanism and yields water soluble polysaccharides with a mean molar mass of up to 100 000 g mol−1 and a mean hydrodynamic radius of 3 nm. Although polymerization reactions promoted by NTAP occurs in a random manner, the α-1,6 and β-1,6 linkages are however dominant. Furthermore, we discovered that NTAP is highly selective, strongly favoring glycosylation over other chemical transformations in the bulk. Under our working conditions, glycosyl units are preserved that constitute the repeating units of the polysaccharide product. No chemical degradation (e.g. intramolecular dehydration reactions) was observed, allowing a white powder to be recovered with a yield higher than 93 wt%. From a practical point of view, NTAP has great potential for breakthrough in the production of polysaccharides, notably because it does not require the use of a solvent or catalyst, thus by-passing the traditional post-treatment of aqueous effluents and catalyst recycling characteristic of biotechnological polysaccharide production. Its efficiency at low temperature also prevents carbohydrates from degradation. Finally, NTAP proceeds on an on/off switch basis, allowing the polymerization reaction to be started and stopped quasi instantaneously. [ABSTRACT FROM AUTHOR]

Since their introduction in 2004, deep eutectic solvents (DESs) have attracted interest in different fields of chemistry. In the case of biomass, DESs are particularly interesting, not only because of their low cost and biodegradability, but also due to their unique property to interact with hydrogen-bond donors such as renewably sourced polyols or carboxylic acids. Through selected examples, we report the contribution of DESs for the dissolution of biomass, the extraction/purification of bioderived chemicals, and the conversion of carbohydrates to furanic derivatives. In all examples, we discuss how the DES can impact the selectivity of a chemical process and the limitations associated with the use of DES. In particular, impact of the DES viscosity on extraction, the recovery and recycling of DES, and the stabilization of chemical intermediates in DES are among the key aspects that are discussed. [ABSTRACT FROM AUTHOR]

We show that the coating of choline chloride on silica-supported AlCl3 allows the dehydration of carbohydrates to successfully proceed in low boiling point organic solvents. The concept is based on the in situ formation of a deep eutectic liquid phase on the catalyst surface, thus facilitating the interaction between the solid catalyst and insoluble carbohydrate. [ABSTRACT FROM AUTHOR]

Here we show that combination of Pd/C and Amberlyst-15 in a single reactor allowed fructose and inulin to be converted to 5-hydroxy-2-5-hexanedione, a valuable chemical platform, in a one-pot process. [ABSTRACT FROM AUTHOR]

BRIEFS Sulfonated mesoposous carbons efficiently catalyze the glycosylation of various monosaccharides with alkyl alcohols. [Display omitted] • Sulfonated mesoporous carbons exhibit high catalytic performances in the glycosylation of glucose with fatty alcohols. • Mesoporous channel improved the glycosylation rate of carbohydrates, thus limiting the side formation of humins. • Limiting the formation of humins concomitantly limit the deactivation rate of the catalyst which was successfully recycled. • Sulfonated mesoporous carbons was found applicable from different carbohydrates and different alkyl alcohols. • Space time yields of the Fischer glycosylation reactions are in line with the industrial requirements of the field. Herein we investigated the catalytic performances of sulfonated mesoporous carbons in the glycosylation of carbohydrates with alkyl alcohols. Catalytic performances were compared to common solid acid catalysts previously reported for this reaction. Under optimized conditions, the targeted alkyl glycosides were obtained in 85% yield, together with a turn over frequency and a space time yield higher than those of the best heterogeneous catalysts reported so far in such reaction. Furthermore, the presence of mesoporous channels significantly lowered the deactivation rate of the catalyst in comparison to a non-porous sulfonated carbon. [ABSTRACT FROM AUTHOR]