Catalysis In Ionic Liquids Research Articles

Gold(III) Catalysis in Ionic Liquids: The Case Study of Coumarin Synthesis

AbstractWell‐defined (P,C)‐cyclometalated Au(III) complexes proved to be able to catalyze the synthesis of coumarins by intramolecular hydroarylation of a broad range of aryl propiolates under mild and practical conditions (0.1–2 mol% catalyst, 25–40 °C, 1–24 hours). The use of an ionic liquid as reaction solvent allowed to drastically decrease the amount of Brönsted acid used to unlock the catalyst regeneration step. The effect of the nature of the acid additive and of the ionic liquid anion have been assessed. Preliminary results on the extension of this methodology to the cyclization of aryl propargyl ethers are also presented.

Ionic Liquid Catalysis in Cyclic Carbonate Synthesis for the Development of Soybean Oil-Based Non-Isocyanate Polyurethane Foams.

A method for obtaining non-isocyanate polyurethane (NIPU) foams from cyclic carbonate (CC) based on soybean oil was developed. For this purpose, cyclic carbonate was synthesized from epoxidized soybean oil and CO2 using various ionic liquids (ILs) as catalysts. Among the tested ILs, the highest selectivity (100%) and CC yield (98%) were achieved for 1-ethyl-3-methylimidazolium ([emim]Br). Without any purification, the resulting cyclic carbonate was reacted directly with diethylenetriamine as a model crosslinking agent to produce NIPU foams. It was found that the soybean oil-based CC synthesized with bromide imidazolium ionic liquids exhibited significantly shorter gelling times (8 min 50 s for [emim]Br and 9 min 35 s for [bmim]Br) compared to those obtained with the conventional TBAB catalyst (26 min 15 s). A shorter gelling time is a crucial parameter for the crosslinking process in foams. The obtained foams were subjected to mechanical tests and a morphology analysis.

Acceptorless dehydrogenation of biomass-derived aromatic alcohols to aromatic ketones synergistically catalysed by Pd/C and ionic liquids

Acceptorless dehydrogenation of alcohols is a promising pathway for biomass resource utilization and hydrogen supply, but still lacking for simple and effective catalysts. Herein, we report a metal-ionic liquids (ILs) catalyst for synergistical catalytic dehydrogenation of aromatic alcohols to aromatic ketones under mild conditions without any acid/base additives. It is found that the combination of Pd/C with 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF4]) displays high activity for the dehydrogenation of biomass-derived alcohols including 1-phenyl-1-ethanol, 1-phenyl-1-propanol and 1-(4-methoxyphenyl)ethanol. Mechanistic studies reveal that the Pd/C can be anchored and stabilized by the IL via interacting with [BMIm]+ cation, and the [BF4]- anion plays vital role in the activation of hydroxyl-H and α-H protons via hydrogen bonding interactions. These interactions create an effective microenvironmental for Pd/C catalyzing the cleavage of the hydroxyl-H and α-CH bonds of α-hydroxyl aromatic alcohols to generate aromatic ketones and H2. Moreover, the Pd/C-[BMIm][BF4] catalyst could be recovered and reused for 5 runs without obvious activity loss. This strategy provides more evidences for the synergetic catalysis of metal and ionic liquids and exhibits potential application prospects for hydrogen supply from renewable biomass-derived alcohols.

A Schiff base chemical sensor for selective detection of hexavalent chromium ions: Real sample application

In this study, a straightforward Schiff base (2-(phenylmethyl-1-hydrazine formamide)) was synthesized via ionic liquid catalysis using benzaldehyde and aminourea hydrochloride. This approach represents a simple, efficient, and environmentally friendly synthesis method, with the added benefit of recyclability and reusability of the ionic liquid catalyst. Additionally, the Schiff base exhibits considerable capability for anion detection and demonstrates selective identification of CrO42− and Cr2O72− across different pH environments. The stoichiometric ratio was determined to be 2:1 through UV–vis absorption titration, with detection limits for CrO42− and Cr2O72− measured at 6 × 10−5 M and 7 × 10−5 M, respectively. To assess the probe's complexation mechanism with hexavalent chromium ions, infrared spectroscopy, and hydrogen nuclear magnetic resonance spectroscopy were employed.

Synergistic catalysis of ionic liquids and metal salts for facile PET glycolysis

Polyethylene terephthalate (PET), a thermoplastic engineering polyester, is one of the most widely used polymers today. However, PET can be recycled and difficult to degrade under atmospheric conditions due to high chemical stability, causing problems such as environmental pollution and waste of resources. Through comparative experiments, it was found that protic ionic liquids (PIL) and transition metal salts have a synergistic catalytic effect, under optimal reaction conditions, PET was subjected to glycolysis at 180 °C for 20 min by using PIL-Zn(OAc)2 as a catalyst, PET was almost completely converted and the yield of monomeric BHET reached a peak of 91.25 %, this is much higher than the yield using ionic liquids or metal salts alone. In this paper, protic ionic liquids were synthesized and compounded with transition metal salts as catalysts for PET glycolysis. Through FT-IR, NMR, TG and SEM analysis of the experimental product, it can be determined that the target product is bis-hydroxyethyl terephthalate (BHET). The composite catalyst still exhibited excellent catalytic activity after 8 cycles. Further, this study explored the reaction kinetics of PIL-Zn(OAc)2 catalyzed PET glycolysis to obtain an apparent activation energy Ea = 120.59 kJ/mol of the reaction. Finally, this paper also discussed the possible reaction pathway of the composite catalyst, hoping this composite catalyst can provide a reference for the industrialization of PET recycling.

In situ XPS of competitive CO2/H2O absorption in an ionic liquid

Superbasic ionic liquids (SBILs) are being investigated as potential carbon dioxide (CO2) gas capture agents, however, the presence of H2O in the flue stream can inhibit the uptake of CO2. In this study a thin film of the SBIL trihexyltetradecylphosphonium 1,2,4-triazolide ([P66614][124Triz]) was deposited onto rutile TiO2 (110) using in situ electrospray deposition and studied upon exposure to CO2 and H2O using in situ near-ambient pressure x-ray photoelectron spectroscopy (NAP-XPS). The molar uptake ratio of gas in the electrosprayed SBIL (n gas :n IL) was calculated to be 0.3:1 for CO2, 0.7:1 for H2O, and 0.9:1 for a CO2/H2O mixture. NAP-XPS taken at two different depths reveals that the competitive absorption of CO2 and H2O in [P66614][124Triz] varies with sampling depth. A greater concentration of CO2 absorbs in the bulk layers, while more H2O adsorbs/absorbs at the surface. The presence of H2O in the gas mixture does not inhibit the absorption of CO2. Measurements taken during exposure and after the removal of gas indicate that CO2 absorbed in the bulk does so reversibly, whilst CO2 adsorbed/absorbed at the surface does so irreversibly. This is contrary to the fully reversible CO2 reaction shown for bulk ionic liquids (ILs) in literature and suggests that irreversible absorption of CO2 in our highly-structured thin films is largely attributed to reactions at the surface. This has potential implications on IL gas capture and thin film IL catalysis applications.

Advances in Pyrazoles Rings’ Syntheses by Heterogeneous Catalysts, Ionic Liquids, and Multicomponent Reactions - A Review

Abstract: Nitrogen heterocycles represent one of the most important units in modern organic chemistry besides their wide existence broadly in natural products, pharmaceuticals, and functional materials. Among these heterocycles, pyrazole, the molecule of the present work, received much attention in organic synthesis because it delivers significant therapeutic and biological values as it was found to be the core unit of many drugs, agrochemicals, and related candidates. Due to this fact, the development of practical methodologies for the preparation of pyrazoles has attracted the long-standing interest of synthetic chemists. Synthetic heterocyclic chemistry using green methods has captivated many researchers in the recent past due to its easy operation and environmentally friendliness. In this review, we summarized systematic approaches for the synthesis of pyrazole derivatives via heterogeneous catalysis, ionic liquid catalysis, and multicomponent reactions.

One-step DMC synthesis from CO2 under catalysis of ionic liquids prepared with 1,2-propylene glycol

Three quaternary ammonium ionic liquids with strong nucleophilicity and distinctive structures were synthesized with high yield and purity based on the 1,2-propylene glycol anion (CH3CH2OHCH2O-) derived from transesterification products. Dimethyl carbonate (DMC) was in turn produced via a one-step reaction among propylene oxide (PO), CO2, and methanol (MeOH) by using the synthesized ionic liquids. The involved two-stage catalytic reaction of PO-CO2 cycloaddition and PC-MeOH transesterification was implemented without catalyst separation. Under mild conditions, the PO conversion reached 99.0%, with a PC yield of 99.0%, and a TON value of 119.5. Following the cycloaddition, MeOH was immediately introduced to achieve a PC conversion of 71.2%, a selectivity to DMC above 99%, and a TON value of 57.4 for the transesterification reaction. The influences of temperature as well as time for cycloaddition and transesterification were investigated. Cycloaddition of CO2 with various epoxides was also examined and all showed good performance. By taking advantage of the decomposability of as-prepared ionic liquids and the recyclability of decomposition products, a new catalyst circulation process was designed to complete the full cycle without introduction of any impurities into the product system.

Ionic Liquid Mediated Triple Catalysis for Alkylation and Methylation of Acyl Chlorides with Mechanistic Insight

Here we report a seminal triple catalysis strategy with the assistance of catalytic ionic liquid. DFT calculations reveal the detailed effect of ionic liquid in this triple catalysis mediated C(sp3)-H functionalizations and a very different mechanism has been established in contrast to all previous dual catalysis research. Based on it, direct coupling between acyl chlorides and very strong or polar C(sp3)-H bonds has been realized in high yields as well as unexpected methylation of acyl chlorides first using just 1.2 equivalent tetramethylsilane as methyl source via successive C(sp3)-H and C(sp3)-Si cleavage. One pot methylation strategy has been developed in this research. This is the first report of that ionic liquid is used for very strong C(sp3)-H bonds functionalization and the first report of that tetramethylsilane is used as methyl source.

Structures, properties and applications of bimetallic composite ionic liquids

The bimetallic composite ionic liquids show excellent catalytic performances. The key lies in the synergy effect of the bimetallic centers. The interactions between bimetallic centers in metallic composite ionic liquids were studied on the basis of literature research. The relative molecular polarity index (MPIr) was proposed to quantitatively evaluate the interaction strength between bimetallic centers, and the three metal salts (CuCl, AgCl, ZrCl4) most likely to form bimetallic composite anions were screened out. X-ray absorption fine structure (XAFS) and density functional theory (DFT) were combined to reveal the structures of the bimetallic composite anions and the aggregation mechanism. The physical and chemical properties (density, viscosity, conductivity, glass transition temperature, acidity) of bimetallic composite ionic liquids were investigated, and the mechanism of the transition behaviors was discussed from the micro perspective. This study can provide reference for the further utilization of bimetallic composite ionic liquids in catalysis, separation and preparation of high-performance materials.

Quantitative Control Factors of Double Salt Ionic Liquids Catalysis in the Coupling Reaction of Epoxied and Methanol

Quantitative Control Factors of Double Salt Ionic Liquids Catalysis in the Coupling Reaction of Epoxied and Methanol

Ionic liquids in catalysis: A review

Abstract The organic salts that show melting points less than 100 °C (i.e. under the boiling temperature of water) are referred to as Ionic liquids/fluids (ILs), they describe a fascinating class of liquid materials distinguished by exceptionally low vapor pressure. Ionic liquids (ILs) have originated from volatile organic solvents as an environmentally friendly alternative. ILs comprising of components, both cationic and anionic, having certain properties that can be produced. The ability of such environmentally friendly ILs in chemical reactions is described by referring to them as “designer solvents”. They are moldable to match the conditions of the reaction and thus become “task-specific ILs.” Their ability to dissolve transition metal complexes makes them useful in increasing, reaction rates and selectivity in many catalytic organic reactions. Some of the characteristic physical properties of room temperature organic ionic liquids (RTILs) are low hydrophobicity, low volatility, and low lipophilicity, which makes their nature independent among other liquids. This nature supports homogeneous as well as heterogeneous catalysts thus, making reactions economically and environmentally friendly. This review discusses the applications of ILs in organic catalytic transformation.

Synergistic catalysis of metalloporphyrins and phosphonium ionic liquids for the efficient transformation of CO2 under ambient conditions

Synergistic effect between different functional groups is of significant influence on the activity of catalysts, especially for bi- or multi-component catalysts. Herein, a binary catalyst composing of metalloporphyrin (MPP) and phosphonium ionic liquid (PIL) is developed. The influence of substitution groups in both MPP and PIL on the cycloaddition addition of carbon dioxide and epoxides was comprehensively studied. The results demonstrated that the introduction of both electron-donating and electron-withdrawing functional groups in 5,10,15,20-tetraphenylporphyrin (TPP) framework was unfavorable to CO2 transformation. Moreover, PIL cocatalyst with longer alkyl group could enhance the catalytic activity obviously. When Co3+ was used as the metal active center, the binary catalyst system (TPP/Ph3PHexBr) could endow cyclic carbonate with a quantitative yield under the ambient condition of 50 °C and 1 atm CO2 pressure. The turnover frequency (TOF) value could also be as high as 191.3 h–1. Our founding thus provides an insight into the design of binary catalysts for efficient transformation of CO2.

Ionic Liquids in Catalysis

Ionic liquids play a larger and larger as well as more and more diversified role in catalysis [...]

Synergistic catalysis of imidazole acetate ionic liquids for the methanolysis of spiral poly(ethylene 2,5-furandicarboxylate) under a mild condition

Methanolysis of PEF which has weak crystallization induced by the inherent angle of 129.4° between the carboxylates on the furan ring, can proceed under a mild condition through the synergistic catalysis of [BMIm][OAc].

A correlation on ultrasonication with nanocrystalline cellulose characteristics

Catalytic ionic liquid hydrolysis of cellulosic material have been considered as a green and highly efficient dissolution process. However, application of a pre-treatment process, i.e; ultrasonication enhances the hydrolysis of cellulose in ionic liquid by providing mechanical force. In this paper, we describe the impact of both chemical and mechanical approaches to produce nanocrytalline cellulose (NCC) with anticipated particle size, and crystallinity with improved yields. The ultrasonication treatment was evaluated in terms of treatment time and vibration amplitude. It was found that the lowest ultrasonication time (5 min) produced the NCC of highest crystallinity (73 %), but the lowest yield (84 %). In contrary, the highest ultrasonication vibration amplitude at 90 % produced NCC with highest crystallinity value (67 %) as well as yields (90 %). It concludes that ultrasonic pre-treatment improves the hydrolysis process of cellulose in ionic liquid with increasing yield and crystallinity of NCC.

Expedient synthesis of novel antibacterial hydrazono-4-thiazolidinones under catalysis of a natural-based binary ionic liquid.

A library of pyran-2H-one-3-ylmethylidene and chromene-2H-one-3-ylmethylidene derivatives of the titled heterocyclic framework was synthesized from 3-acyl-4-hydroxypyran/chromene-2H-one via sequential reaction with thiosemicarbazide and dialkyl acetylenedicarboxylates. The syntheses were carried out under efficient catalysis of a new binary ionic liquid mixture [L-prolinium chloride][1-methylimidazolium-3-sulfonate] in one pot and solvent-free conditions. Calculations based on density functional theory displayed that the barrier energy for interconversion of the two possible diastereomeric isomers of each product is less than the thermal energy of molecules at room temperature, as only one product can be resolved from a given reaction mixture. This seems to be the case for the previously reported hydrazonothiazolidines. The binary ionic liquid mixture melts at near room temperature and can be considered as a solution of HCl in 1:1 mixture of two zwitterionic species. It proved to be more efficient than its constituents in catalyzing the above synthesis in one-pot operation. Some of the synthesized products have shown pronounced antibacterial activities. The ionic liquid is virtually stable in air and moisture, as can be retrieved several times without appreciable decrease in its catalytic activity.

Selective conversion of chitin to levulinic acid catalyzed by ionic liquids: distinctive effect of N-acetyl groups

Selective and green conversion of chitin to levulinic acid has been realized by catalysis of ionic liquids up to a yield of 67.0%. Two-approach mechanism was proposed in the presence of H-bonding networks mainly contributed by the N-acetyl groups.

Experimental and DFT mechanistic insights into one-pot synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-diones under catalysis of DBU-based ionic liquids

Kinetic impacts of two DBU-based ionic liquids in the three-component synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-diones and the mechanism of the reaction were investigated by DFT calculations.

The molecular structure and multifunctionality of the cryptic plant polymer suberin.

Suberin, a plant polyester, consists of polyfunctional long-chain fatty acids and glycerol and is an intriguing candidate as a novel antimicrobial material. We purified suberin from cork using ionic-liquid catalysis during which the glycerol bonds that ensure the polymeric nature of suberin remained intact or were only partially cleaved—yielding the closest to a native configuration reported to date.The chemistry of suberin, both in situ (in cryogenically ground cork) and ex situ (ionic-liquid extracted), was elucidated using high-resolution one- and two-dimensional solution-state NMR analyses. Centrifugation was used to isolate suberin particles of distinct densities and their monomeric composition, assembly, and bactericidal effect, inter alia, were assessed.Analysis of the molecular structure of suberin revealed the relative abundance of linear aliphatic vs. acylglycerol esters, comprising all acylglycerol configurations and the amounts of total carbonyls (C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O), free acid end groups (COOH), OH aliphatics, and OH aromatics. Suberin centrifuged fractions revealed generic physiochemical properties and monomeric composition ​and self-assemble into polygonal structures that display distinct degrees of compactness when lyophilized. Suberin particles—suberinsomes—display bactericidal activity against major human pathogenic bacteria.Fingerprinting the multifunctionality of complex (plant) polyesters such as suberin allows for the identification of novel polymer assemblies with significant value-added properties.