Solvent-catalyst Systems Research Articles

Knoevenagel reaction promoted by functional ionic liquids with primary and tertiary amines

ABSTRACT Functional ionic liquids have been widely used in the fields of synthetic chemistry, analytical chemistry, electrochemistry and material chemistry owing to their excellent properties such as easy structure modification and adjustable properties. In this work, a series of basic functionalized ionic liquids were prepared from 1, 4-diazabicyclo [2.2.2] octane (DABCO) or hexamethylenetetramine (HMTA) with various halogenated hydrocarbons, then these functional ionic liquids and water were used as solvent-catalyst system in the Knoevenagel reaction of various aldehydes with ethyl cyanoacetate or malononitrile, the influence of the structure of the ionic liquid and the content of water was investigated. The results showed that the composite solvent-catalyst system mixed by the functional ionic liquid N-(3-aminopropyl)-1,4-diazabicyclo [2.2.2] octane bromide with water can effectively promote the Knoevenagel reaction and the alkalinity of amine and hydrogen bond play an important role. Aromatic aldehydes with electron-donating or electron-withdrawing groups can obtain the target product at an excellent yield (79-99%). It is worth noting that the polycyclic aromatic aldehydes with high steric hindrance, 86%-95% yields of the object products were also obtained after 15 h-25 h. Furthermore, the catalyst could be reused for 6 times without any loss in its catalytic activity. The composite solvent-catalyst system mixed by the Functional ionic liquid N-(3-aminopropyl)-1,4-diazabicyclo[2.2.2]octane bromide with water can effectively promote the Knoevenagel reaction, even for the electron-rich aromatic aldehydes with poor reactivity, high yields of the target products and fast reaction rate were also obtained at room temperature.

Acid-Catalyzed Atmospheric Organosolv Treatment By Using gamma-Valerolactone and Ethylene Glycol For The Delignification of Hazelnut Shell and Precipitation of Lignin

Lignin-based biorefineries are gaining importance day by day to obtain many value-added products from lignin. One of the most important processes that allow the recovery of both cellulose and lignin in those biorefineries is organosolv pretreatment. In this study, organosolv pretreatment was applied to the hazelnut shell at 130 °C for 60 min with ethylene glycol and γ-valerolactone solvents in the presence of a catalyst (either phosphoric acid or acetic acid). The success of solvent-catalyst systems was assessed by delignification efficiency and lignin recovery. Lignins obtained by precipitation were also analyzed by FTIR, TGA, DSC and Py-GC/MS. Highest delignification efficiency (33.9%) was detected for ethylene glycol- phosphoric acid solvent-catalyst pair. It was observed that acetic acid was not an effective catalyst compared to phosphoric acid. The delignification efficiency of γ-valerolactone was low (< 26 %) under atmospheric conditions, and in the presence of acetic acid, lignin was not precipitated from GVL system.

Solvent-catalyst optimization of ionic liquid-based CO2 conversion to propylene carbonate: Laboratory validation and techno-economic analysis

Ionic liquids (ILs) have been widely suggested as efficient catalysts to produce propylene carbonate (PC) from CO2 and propylene oxide (PO). Recently, the use of liquid-liquid extraction (LLE) has been proposed to efficiently separate ILs from PC since it reduces energy consumption, with fatty alcohols when selecting hydrophobic ILs. However, the study of this reaction-separation system at experimental level is scarce. In addition, the solvent-catalyst system design to improve the global process performance is a current challenge. This work develops an integrated experimental-computational multiscale approach to improve the PC production process by CO2 cycloaddition to PO using the IL [P66614][Br] as catalyst. Reaction yield and liquid-liquid equilibrium measurements were carried out for the experimental validation of the proposed catalytic/separation systems using different solvents (fatty alcohol and water). Process modelling and techno-economic analysis were performed using Aspen Plus for solvent-catalyst optimization, proceeding with an integrated iterative experimental-computational approach to decrease energy requirements and operating costs. It was found that the presence of solvents in the reaction affects conversion and selectivity of the reaction, with fatty alcohols increasing PC yield and enabling IL/PC separation, while water reduces PC selectivity. On the other hand, the presence of water in the process allows reducing electricity demands as well as vacuum requirements. It was possible to modulate fatty alcohol and water dosages to minimize energy consumption, vacuum requirements and utility costs. Optimal configurations have an energy consumption of approximately 0.6 kWh/kgPC and utility costs of 6.6 $/tPC.

Environment-friendly recycling of CFRP composites via gentle solvent system at atmospheric pressure

The recovery of high-value carbon fibers from carbon fiber-reinforced polymer (CFRP) composites is essential for ensuring a sustainable future. In this work, a simple and eco-friendly approach was presented for the chemical recycling of anhydride-cured epoxy-based CFRP composites with a mixed solution of monoethanolamine (MEA) and potassium hydroxide (KOH). In this solvent catalyst system, the resin matrix was decomposed by cleaving the ester bonds. Thus, a high CFRP composite decomposition ratio of 99% was achieved at ∼160 °C within 60 min under ambient pressure. The recovered carbon fibers (CFs) had a clean surface and retained more than 95% of their original stiffness and strength. Moreover, one of the highlights of this process was that the excess MEA solvent and degraded epoxy resin (DER) were recovered from the degraded organic products (DOP) by simple distillation. The DER was reused in combination with the original epoxy resin system to prepare new resin material with good mechanical properties, forming a closed-loop chemical recycling route. The advantages of this method include facile reaction conditions, near-complete recovery of CFs and solvent, and the absence of harmful solid waste, demonstrating that this recycling process has a high degree of environmental friendliness.

Glucose conversion to 5-hydroxymethylfurfural with chromium exchanged bentonite and montmorillonite catalysts in different solvents

Synthesis of 5-hydroxymethylfurfural (HMF) was studied using Cr-montmorillonite and Cr-bentonite catalysts. Catalysts were characterized by Brunauer–Emmett–Teller surface area analyzer, X-ray diffraction (XRD), infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The effects of temperature and time on the conversion of glucose to HMF were investigated with different solvent-catalyst systems. HMF yield (45%) was obtained at 140 °C for 20 min using Cr-montmorillonite in 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) ionic liquid. The 62.6% HMF yield was efficiently achieved at 150 °C for 10 min in [BMIM]Cl using Cr-bentonite. Cr-bentonite catalyst has good reusable properties in dimethyl sulfoxide (DMSO). The 94% of catalytic efficiency was maintained at the end of fifth use in DMSO.

Ionic Liquid Binary Mixtures, Zeolites, and Ultrasound Irradiation: A Combination to Promote Carbohydrate Conversion into 5-Hydroxymethylfurfural

The efficient conversion of biomass into value-added compounds under mild and safer conditions is a cornerstone of present research efforts to meet the needs of the chemical industry with sustainable development. In this work, we studied the dehydration of fructose, glucose, and sucrose into 5-hydroxymethylfurfural (5-HMF), catalyzed by HY zeolite, in three ionic liquid mixtures differing for the cation, aromatic, or aliphatic. We investigated the effect of several operational parameters such as temperature, catalyst loading, zeolite counterion, solvent mixture, and added chloride. In the optimal experimental conditions, we obtained good conversions to 5-HMF especially for fructose and sucrose, 73% and 62%, using the relatively low temperatures of 80 and 120 °C, respectively. Interestingly, in the used experimental conditions, the solvent–catalyst systems can be reused for at least 6 cycles without loss in performance. We also investigated the dehydration of fructose under sonochemical activation, obtaini...

DABCO-catalyzed Knoevenagel condensation of aldehydes with ethyl cyanoacetate using hydroxy ionic liquid as a promoter.

N-(2-Hydroxy-ethyl)-pyridinium chloride ([HyEtPy]Cl) was synthesized and explored as a novel promoter for 1,4-diazabicyclo [2.2.2] octane (DABCO)-catalyzed Knoevenagel condensation reactions, which showed better catalytic activity compared to other ionic liquid (IL) that had no hydroxyl group attached to the IL scaffold. The effect of hydrogen bond formation between the hydroxyl group of [HyEtPy]Cl and the carbonyl group of aldehyde played an important role in the Knoevenagel condensation reaction. In the [HyEtPy]Cl–H2O–DABCO composite system, Knoevenagel condensation reactions proceeded smoothly and cleanly, and the corresponding Knoevenagel condensation products were obtained in good to excellent yields in all cases examined. This protocol provides a versatile solvent–catalyst system, which has notable advantages such as being eco-friendly, ease of work-up and convenient reuse of the ionic liquid.

Morita–Baylis–Hillman reaction in eutectic solvent under aqueous medium

Aqueous solvent-catalyst system formed by DES (1ChCl/2Gly) and DABCO is more useful and practical to the Morita–Baylis–Hillman reaction.

ChemInform Abstract: [HyEtPy]Cl—H2O: An Efficient and Versatile Solvent System for the DABCO‐Catalyzed Morita—Baylis—Hillman Reaction.

An efficient and versatile solvent–catalyst system, [HyEtPy]Cl–H2O-DABCO, has been developed and used in the Morita–Baylis–Hillman reaction. Under the mild reaction conditions, Morita–Baylis–Hillman proceeds very quickly and efficiently. This protocol has notable advantages such as eco-friendliness, ease of work-up and reuse of ionic liquid conveniently, which could help reduce disposal costs and contribute to the development of a new solvent–catalyst system for use in green and continuous chemical processes.

New Pyridinium-Based Ionic Liquid as an Excellent Solvent–Catalyst System for the One-Pot Three-Component Synthesis of 2,3-Disubstituted Quinolines

The synthesis of a variety of 2,3-disubstituted quinolines has been achieved successfully via a one-pot three-component reaction of arylamines, arylaldehydes and aliphatic aldehydes in the presence of butylpyridinium tetrachloroindate(III), [bpy][InCl4], ionic liquid as a green catalyst and solvent. Mild conditions with excellent conversions, and simple product isolation procedure are noteworthy advantages of this method. The recyclability of the ionic liquid makes this protocol environmentally benign.

Electrolysis of Ionic Liquids. A Possible Keystone for the Achievement of Green Solvent-Catalyst Systems

Electrolysis of Ionic Liquids. A Possible Keystone for the Achievement of Green Solvent-Catalyst Systems

ChemInform Abstract: Tunable Protic Ionic Liquids as Solvent‐Catalysts for Improved Synthesis of Multiply Substituted 1,2,4‐Triazoles from Oxadiazoles and Organoamines.

Abstract More than green alternatives to traditional volatile molecular organic solvents, protic ionic liquids as dual solvent-catalysts have been successfully used to promote reactions of organoamines with oxadiazoles to afford sterically hindered 1,2,4-triazoles. Among the tested protic ionic liquids, pyridinium trifluoroacetate and acetate showed the highest efficiency for the reactions of arylamines and alkylamines, respectively, indicating that tunable catalysis could be readily effected with protic ionic liquid solvent-catalysts by simply tuning their cation and anion counterparts. A general and efficient approach has been developed for synthesis of multiply substituted 1,2,4-triazoles based on the tunable protic ionic liquid solvent-catalyst systems.

Tunable protic ionic liquids as solvent-catalysts for improved synthesis of multiply substituted 1,2,4-triazoles from oxadiazoles and organoamines

More than green alternatives to traditional volatile molecular organic solvents, protic ionic liquids as dual solvent-catalysts have been successfully used to promote reactions of organoamines with oxadiazoles to afford sterically hindered 1,2,4-triazoles. Among the tested protic ionic liquids, pyridinium trifluoroacetate and acetate showed the highest efficiency for the reactions of arylamines and alkylamines, respectively, indicating that tunable catalysis could be readily effected with protic ionic liquid solvent-catalysts by simply tuning their cation and anion counterparts. A general and efficient approach has been developed for synthesis of multiply substituted 1,2,4-triazoles based on the tunable protic ionic liquid solvent-catalyst systems.

Tandem catalysis in ionic liquids: a recyclable catalytic synthesis of benzofuran derivatives

A convenient, recyclable catalytic synthesis of benzofuran-2-acetic esters 2 by sequential Pd(0)-catalyzed deallylation—Pd(II)-catalyzed carbonylative heterocyclization of 1-(2-allyloxyphenyl)-2-yn-1-ols 1 in ionic liquids is presented. Reactions were typically carried out in BmimBF 4 as the solvent at 100 °C and under 30 atm of CO, in the presence of catalytic amounts (1 mol %) of PdI 2 in conjunction with KI (1 equiv), PPh 3 (4 mol %), MeOH (28 equiv), and H 2O (2 equiv). The solvent-catalyst system could be recycled several times without appreciable loss of catalytic activity.

ChemInform Abstract: Baylis—Hillman Reaction Promoted by a Recyclable Protic—Ionic—Liquid Solvent—Catalyst System: DABCO—AcOH—H2O.

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Baylis–Hillman reaction promoted by a recyclable protic-ionic-liquid solvent–catalyst system: DABCO–AcOH–H 2O

A recyclable protic-ionic-liquid solvent–catalyst system, DABCO–AcOH–H 2O, has been developed and used in the Baylis–Hillman reaction of aromatic aldehydes, aliphatic aldehydes, and cinnamaldehydes with acrylates and acrylonitrile, showing comparable performance to free DABCO in traditional solvents. The DABCO–AcOH–H 2O solvent–catalyst system could be reused for at least five times without significant loss of activity.

Recyclable catalytic synthesis of substituted quinolines: copper-catalyzed heterocyclization of 1-(2-aminoaryl)-2-yn-1-ols in ionic liquids

A convenient and simple approach for the recyclable catalytic synthesis of substituted quinolines is presented. The method is based on CuCl 2-catalyzed heterocyclization of readily available 1-(2-aminoaryl)-2-yn-1-ols in BmimBF 4 as the solvent at 100 °C for 15–24 h. The solvent–catalyst system could be successfully recycled up to six times without significant loss of activity.

Ytterbium(III) Triflate–Catalyzed Stereoselective Synthesis of β‐Lactams via [2+2] Cyclocondensation in Ionic Liquid

Catalyzed by ytterbium(III) triflate [Yb(OTf)3], β‐lactams were stereoselectively synthesized from imines and acetyl chlorides in ionic liquid under mild conditions. The ionic liquid and catalyst could be recycled and reused as opposed to traditional solvent–catalyst systems.

Friedel–Crafts alkylation reactions in pyridinium-based ionic liquids

The Friedel–Crafts alkylations of benzene in pyridinium-based ionic liquids (ILs) were investigated. The effects of catalyst–IL composition, reactant composition, quantity of catalyst and reaction temperature on this reaction were studied. The reactions were found to proceed under mild conditions with conversion; a simple product isolation procedure was achieved. The ILs rendered this reaction green characteristics. The ILs could also be recycled and reused as opposed to traditional solvent–catalyst systems.

Enantioselective Chemo‐ and Bio‐Catalysis in Ionic Liquids

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