Direct conversion of glucose and cellulose to 5-hydroxymethylfurfural in ionic liquid under microwave irradiation

An efficient strategy for CrCl₃-mediated production of 5-hydroxymethylfurfural (HMF) in ca. 60% and 90% isolated yields from cellulose and glucose, respectively, in ionic liquid under microwave irradiation is presented.     

Hydrolysis of chitosan under microwave irradiation in ionic liquids promoted by sulfonic acid-functionalized ionic liquids

Hydrolysis of chitosan in ionic liquids was carried out under microwave irradiation (MW) using sulfonic acid-functionalized ionic liquids (SFILs) as catalysts. The effect of microwave power, irradiation time, dosage of SFILs and DMSO was investigated by orthogonal tests. Under the optimal reaction conditions, the yield of total reducing sugars (TRS) reached over 90% within 2 min. The viscosity-average molecular weight of degraded chitosan was determined by viscosity method. The structures of the original and degraded chitosan were characterized by Fourier-transform infrared (FTIR) spectra, X-ray powder diffraction (XRD) analysis and carbon-13 nuclear magnetic resonance spectroscopy (¹³C NMR). The influence of microwave power and irradiation time on the TRS and M_v was further studied. This method can dramatically reduce reaction time.     

I_2/离子液体作为可回收均相催化剂在微波条件下高效制备全乙酰糖(英文)

以可回收的I2/PEG400型离子液体(I2/IL400)为催化体系,发展了一种高效、实用的合成全乙酰糖衍生物的方法.结果表明,以糖与乙酸酐为原料,在微波辐射、无溶剂条件以及I2/IL400体系中,数分钟之内可以非常高的产率(90%–99%)和数十毫摩尔规模(50.0 mmol)制备出全乙酰糖.通过简单的甲苯萃取,可以从I2/IL400体系中分离出全乙酰糖,I2/IL400体系可循环使用6次,且产率均在90%以上.当反应规模扩大到50.0 mmol时,该体系依然能高效快速地催化糖的全乙酰化,并且可以循环使用5次,产率依然维持在90%左右.     

Immobilized ionic liquid on superparamagnetic nanoparticles as an effective catalyst for the synthesis of tetrasubstituted imidazoles under solvent-free conditions and microwave irradiation

The ionic liquid 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium chloride was immobilized on superparamagnetic Fe₃O₄ nanoparticles (IL-MNPs) and used as an efficient heterogeneous catalyst for the one-pot synthesis of 1,2,4,5-tetrasubstituted imidazoles under solvent-free conditions using microwave irradiation. The reactions in conventional heating conditions were compared with the microwave-assisted reactions. The combined merits of microwave irradiation and immobilized ionic liquid on superparamagnetic nanoparticles make the four-component condensation with safe operation, low pollution, and rapid access to products and simple work-up.     

Sulfuric acid immobilized on silica: an efficient reusable catalyst for selective hydrolysis of the terminal O-isopropylidene group of sugar derivatives

Sulfuric acid immobilized on silica proved to be an efficient catalyst for selective hydrolysis of the terminal O-isopropylidene group of sugar derivatives. The method is very simple and economic for large-scale synthesis in which the catalyst is recovered and reused for several runs. Reactions with di-O-isopropylidene derivatives of d-glucose, d-mannose, d-fructose and l-sorbose led to the formation of the corresponding mono-O-isopropylidene derivatives in good to excellent yields.     

[Amim]Cl离子液体中微波辐射加热促进稻草秸秆酸水解制备还原糖

在1-烯丙基-3-甲基咪唑氯盐([Amim]Cl)离子液体介质中,用微波辐射加热促进稻草秸秆纤维素的酸水解,探讨了微波辐射加热及离子液体对酸催化植物纤维素水解的促进作用;并对水解产物中的还原糖进行了测定,着重考察了离子液体用量、硫酸浓度、微波功率、反应温度、反应时间等因素对还原糖收率的影响.结果表明,在[Amim]Cl...     

SBA-15-functionalized sulfonic acid confined acidic ionic liquid: a powerful and water-tolerant catalyst for solvent-free esterifications

Incorporating a hydrophobic Br?nsted acid ionic liquid (HBAIL) inside the nanospaces of SBA-15-Pr-SO(3)H led to a hydrophobic super Br?nsted acid catalyst, which showed excellent catalytic performance in direct esterification of alcohols and carboxylic acids at ambient temperature under solvent-free conditions.     

Immobilized sulfonic acid functionalized ionic liquid on magnetic cellulose as a novel catalyst for the synthesis of triazolo[4,3-a]pyrimidines

The Brønsted acidic ionic liquid 1-(propyl-3-sulfonate) vinyl imidazolium hydrogen sulfate [IL] was supported on modified magnetic cellulose. The physical structure, composition, and functional groups of the novel supported ionic liquid catalyst were characterized via XRD, FT-IR, EDS, SEM, VSM, TGA, TEM, and BET techniques. Owing to the combination of nano-support features and flexible imidazolium linkers, it acted as a “quasi-homogeneous” catalyst to catalyze the preparation of triazolo[4,3-a]pyrimidine derivatives by a one-pot three-component reaction of active methylene compounds (ethyl cyanoacetate or malononitrile), aminotriazole and aryl aldehydes. The catalyst shows good catalytic activity for the synthesis of triazolo pyrimidines after six times of recycling.     

Green synthesis of benzimidazole derivatives catalyzed by ionic liquid under microwave irradiation

An efficient synthesis of benzimidazole derivatives from o-phenylene diamine and substituted aromatic aldehyde catalyzed by ionic liquid under microwave irradiation was reported. The synthesis conditions were first optimized by single factor experiments. Then, a central composite design combined with response surface methodology was used to study the most effective factors. Optimal conditions were synthesis time 1 h, the reactant/catalyst molar ratio 1:1:0.200, the temperature 50 °C and the microwave power 500 W. Under optimized conditions, the yields of benzimidazole derivatives were 78.55–97.66 %. This method offered the outstanding advantages, such as faster reaction rate, higher yields, recyclable catalyst, environmental friendliness, and simple workup procedure.     

Consecutive preparation of hydrochar catalyst functionalized in situ with sulfonic groups for efficient cellulose hydrolysis

Hydrochars in situ functionalized with –SO₃H groups were generated from kenaf core via a low-temperature hydrothermal carbonization process of 105 °C with a consecutive catalysis of H₂SO₄. The micro-morphology of the hydrochars was strongly affected by the sulfuric acid concentration. Sphere-like particles with size varying between 200 nm and 1 μm were obtained when the acid concentration was 52 wt%. Acid density of the hydrochar increased with the H₂SO₄ concentration increasing. The presence of considerable acidic groups of –SO₃H, –COOH, and –OH on the surface of hydrochars was evidenced by Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. The hydrochar obtained can be used directly for effective catalytic hydrolysis of cellulose without any post-modification. This study proposed a promising sustainable and cost-effective route for facile production of acidic hydrochar from crude plant with tunable properties.     

Molybdate sulfonic acid: preparation, characterization, and application as an effective and reusable catalyst for octahydroxanthene-1,8-dione synthesis

Molybdate sulfonic acid (MSA) as a highly efficient catalyst was synthesized and employed for the synthesis of octahydroxanthene-1,8-dione derivatives. MSA efficiently catalyzed condensation of a wide range of aryl aldehydes and cyclohexane-1,3-diones to obtain octahydroxanthene-1,8-diones. It was characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), and FT-IR spectroscopy. This catalyst can be recovered and reused several times in other reactions maintaining its high activity. This novel and green method is very cheap and has many advantages such as excellent yields, the use of recoverable and eco-friendly catalysts, and a simple work-up procedure.     

新型磺酸功能化吡啶盐酸盐离子液体催化剂用于六氢喹啉合成(英文)

Sulfonic acid functionalized pyridinium chloride [pyridine-SO3 H]Cl has been synthesized as a novel Brnsted acidic ionic liquid and characterized on the basis of its FT-IR,1H and 13C NMR,MS,ther-mogravimetry,and derivative thermogravimetry data.The material has also been used as a highly efficient,homogeneous,and reusable catalyst for the preparation of hexahydroquinolines according to the one-pot multi-component condensation of arylaldehydes,dimedone(5,5-dimethylcyclohexane-1,3-dione),β-ketoesters,and ammonium acetate under solvent-free conditions.     

A green approach for efficient synthesis of N-substituted pyrroles in ionic liquid under microwave irradiation

A rapid synthesis of N-substituted pyrroles has been described by the reaction of 4-hydroxyproline with isatins in ionic liquid under microwave irradiation. The recovered ionic liquid was reused for six cycles. The reaction proceeds without the addition of any acid promoter     

Green synthesis of 3,4-dihydropyrimidinones using nano Fe3O4@meglumine sulfonic acid as a new efficient solid acid catalyst under microwave irradiation

Design, synthesis and characterization of nano Fe₃O₄@meglumine sulfonic acid as a new solid acid catalyst for the simple and green one pot multicomponent synthesis of 3,4-dihydropyrimidin-2(1H)-ones/thiones was studied. New solid acid catalyst was prepared through a clean and simple protocol and characterized using FTIR, VSM, TGA, SEM, elemental analysis (CHN) and XRD techniques. Heterogenization of homogeneous catalyst as a green approach is a useful method for enhancing the efficiency of catalyst. Presented study was a new method for attachment of homogeneous highly soluble catalyst (meglumine sulfate) to the magnetite nanoparticle surfaces for preparing a heterogeneous and effective catalyst. Obtained heterogeneous and reusable solid acid catalyst has high performance in the synthesis of Biginelli compounds. The reaction was performed under microwave irradiation as a rapid and green condition. Easy work up as well as excellent yield (90–98%) of products in short reaction times (40–200 s) and reusable catalyst are the main advantages of presented procedure. Reaction products were characterized in details using physical and chemical techniques such as melting point, ¹H NMR, ¹³C NMR and FTIR.     

Sulfuric acid immobilized on silica: an efficient reusable catalyst for the synthesis of O-isopropylidene sugar derivatives

Sulfuric acid immobilized on silica proved to be an efficient catalyst for the synthesis of O-isopropylidene sugar derivatives from reducing sugars. The method is very simple and economic for large-scale synthesis in which the catalyst is recovered and reused several times. Reactions with d-glucose, d-galactose, d-mannose, l-rhamnose, l-arabinose, d-xylose and l-sorbose led to the formation of the corresponding thermodynamically stable di-O- and/or mono-O-isopropylidene derivatives in good to excellent yields.     

Synthesis of cellulose benzoates under homogeneous conditions in an ionic liquid

The ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl) as a reaction medium was studied for the synthesis of cellulose benzoates by homogeneous acylation of dissolved cellulose with benzoyl chlorides in the absence of any catalysts. Cellulose benzoates with a degree of substitution (DS) in the range from about 1 to 3.0 were accessible under mild conditions. The DS of cellulose derivatives increased with the increase of the molar ratio of benzoyl chloride/anhydroglucose unit (AGU) in cellulose, reaction time, and reaction temperature. Benzoylation of cellulose with some 4-substituted benzoyl chlorides including 4-toluoyl chloride, 4-chlorobenzoyl chloride and 4-nitrobenzoyl chloride was also readily carried out under mild conditions. Furthermore, regioselectively substituted mixed cellulose esters were synthesized in this work. All products were characterized by means of FT-IR, ¹H-NMR, and ¹³C-NMR spectroscopy. In addition, at the end of benzoylation of cellulose, the ionic liquid AmimCl was easily recycled. When the recycled AmimCl was used as the reaction media, the cellulose benzoate with a similar DS was obtained under comparable reaction conditions.     

离子液体作用下微波辐照生物质快速热解制备生物质油(英文)

以离子液体1-丁基-3-甲基咪唑氯([Bmim]Cl)和1-丁基-3甲基咪唑四氟化硼([Bmim]BF4)为催化剂,在微波加热作用下,研究了稻草和锯屑的热解。微波加热20 min,稻草和锯屑的生物油产率分别为38%和34%。考察了微波加热时间、微波功率和离子液体用量对生物质油产率的影响。当以相同的离子液体为催化剂时,稻草微波热解得到的生物质油产率大于锯屑的。生物油成分主要有糠醛、醋酸和1-羟基-2-丁酮等,其含量主要取决于生物质原料和加入的离子液体的类型。     

One-pot synthesis of various xanthene derivatives using ionic liquid 1, 3-disulfonic acid imidazolium hydrogen sulfate as an efficient and reusable catalyst under solvent-free conditions

In this study, 1,3-disulfonic acid imidazolium hydrogen sulfate （DSIMHS） is used as an efficient and reusable ionic liquid for the green, mild, and efficient synthesis of xanthenes under solvent-free conditions. Simple and easy work-up, low cost, green process, short reaction times and excellent yields of the products are the advantages of this procedure. Further, the catalyst can be recycled and reused at least for four times without a noticeably decrease in its catalytic activity.