Acceleration of Baylis-Hillman Reaction using Ionic Liquid Supported Organocatalyst

Various functional ionic liquids (ILs) composed of different cations and anions were activated with carbonyldiimidazole and then covalently linked onto porcine pancreatic lipase (PPL) through lysine coupling. Catalytic performances, such as activity, thermostability, and enantioselectivity were improved successfully, as was investigated in p-nitrophenyl palmitate (pNPP) hydrolysis and racemic 1-phenethyl acetate hydrolysis reaction. The correlation between catalytic performance and modification of IL was studied by catalytic and spectroscopic data, which showed improvement of catalytic performances to a different extent. Hydrolytic activity was enhanced by ILs with chaotropic cations and kosmotropic anions (e.g., more than 4-fold with [choline][H2PO4]). Modifications by ILs bearing kosmotropic cations and chaotropic anions contribute to lipase thermostability and enantioselectivity (e.g., modification with [HOOCBMIm][Cl] showed a 12-fold thermostability increase at 60 °C and more than 7-fold enantioselectivity enhancement than native enzyme). The Matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry experiments suggest that ILs bind with lipase protein. Conformation changes were confirmed by fluorescence spectroscopy, and circular dichroism spectroscopy.

Methyl glycolate (MG) was synthesized as a precursor to ethylene glycol from the catalytic carbonylation of formaldehyde followed by esterification with methanol by using metal-free, efficient and recyclable SO3H-functionalized ionic liquids (BAILs) as catalysts. Among the studied BAILs, N-butyl-N-(3-sulfonylpropyl) thiomorpholine-1,1-dioxide triflate showed excellent activity and MG selectivity. The effects of reaction parameters such as reactant, solvent, catalyst loading, molar ratio of H2O to H2CO, temperature, pressure, and reaction time were studied. MG was obtained in high yield under mild conditions. At 160 °C, 5.0 MPa, and reactant mole ratio of BAIL:H2CO:H2O = l:40:80, 98 % conversion of formaldehyde was achieved with 94 % selectivities of MG. Catalysts did not show any significant deterioration in performance in repeated use up to eight batches. Methyl glycolate (MG) was synthesized from the carbonylation of formaldehyde followed by esterification with methanol using metal-free, efficient and recyclable SO3H-functionalized ionic liquids (BAILs) as catalysts. MG was obtained in excellent yield under mild conditions. The catalyst was reused up to eight consecutive recycles without apparent loss in its catalytic activity.

Rare earth elements (REEs) are widely used in high-tech industries and are important basic raw materials. Bastnaesite is one of the most important minerals used in the rare earth extraction industry, and the efficient development of it is the key guarantee for the safe supply of rare earth raw materials. In this study, a novel method for dissolving bastnaesite using a carboxyl-functionalized ionic liquid ([Hbet][Tf2N]) is proposed. This innovative method provides a collaborative model with the dissolution and synchronous extraction of rare earth elements during the heating and cooling of the [Hbet][Tf2N]–H2O system. In the heating process, rare earth elements can be dissolved in a weakly acidic environment of ionic liquid without the trouble of HF escaping, and the leaching efficiencies of rare earth elements are above 95%. During the cooling of the leaching system, the rare earth ions in the dissolved state are extracted into the ionic liquid phase due to the two-phase stratification of [Hbet][Tf2N] and aqueous solution. It has been proved that rare earth ions recovery and ionic liquid regeneration can be achieved by back extraction using oxalic acid for the REEs-loaded ionic liquid.

Ionic liquids for advanced materials

Aims: In search of a ligand-free, recyclable, selective, and stable catalytic system, we engineered both Pd/GO and Pd/rGO composites and tested them as catalysts for Heck and Suzuki reactions in [bmim] NTf2 ionic liquid medium. Background: Various reports and reviews have been published on exploring the application of ionic liquids as a reaction medium for different organic transformations. Recently, graphene-supported Pt nanoparticles have immobilized with the 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene bis(trifluoromethylsulfonyl) imide ionic liquid [MTBD][bmsi] and further tested to study the oxygen reduction reaction. Surprisingly, [MTBD][bmsi] immobilized system was found highly active towards electrocatalytic reaction. Objective: In various reports, palladium nanoparticles were immobilized with graphene oxide (GO) or with reduced graphene oxide (rGO), and these two types of graphene were further tested as a catalyst for different coupling reactions such as Suzuki-Miyaura, Heck, and Suzuki reaction. Both Pd/- GO and Pd/rGO were found attractive concerning catalyst specific property, i.e., high surface area, and because of that, graphene immobilized palladium was found to be similar to other commercially available palladium catalysts (e.g., Pd on charcoal), but collectively, both hybrid materials (Pd/- GO and Pd/rGO) possess various drawbacks, like high catalyst loading, catalyst leaching (via agglomeration of Pd metals into the clusters) during the recycling test (especially in case of Pd/GO), limited substrate scope, and the requirement of polar solvents, etc. Methods: All the chemicals were purchased from Sigma Aldrich, Acros, or Fluka. NMR spectra were recorded on a standard Bruker 300WB spectrometer with an Avance console at 300 and 75 MHz for 1H and 13C NMR, respectively. Pd/O and Pd/rGO were synthesized as per the reported procedure. The residue was purified by flash chromatography (FC) with hexane/ethyl acetate. The detailed 1H and 13C NMR of each Heck and Suzuki reaction product were found similar to the reported analytical data. 1-butyl-3-methylimidazolium bis (trifluoromethyl sulfonyl) imide ([bmim]NTf2) was synthesized as per the reported procedure. Results and Conclusion: We have successfully developed a highly efficient ligand-free method for Heck and Suzuki reaction, using Pd/rGO catalysts in an ionic liquid medium which afforded the coupling products with excellent yield. One of the major advantages of the proposed protocol is that the catalyst system can be easily re-usable without the loss of catalytic activity, thereby multiplying catalyst turnover. Another advantage is that the reaction proceeds without phosphine ligands, which are expensive, toxic, and contaminants of the product. The green nature of ionic liquid and the simplicity of its operation make the present Heck and Suzuki reactions more attractive.

In order to reduce the pollution and toxicity of current coal fire fighting materials used in underground mines, this paper proposes that the functional ionic liquid, a kind of green material, may be utilized to suppress the spontaneous fire based on coal's chemistry structures. According to the Fourier Transform Infrared (FTIR) spectroscopy experiment in low-temperature oxidation of coal, we found that the aliphatics active groups, decreasing with rising temperatures, react with oxygen with stable and unstable oxygen-containing groups produced such as aromatic ketone and aldehyde. If the aliphatics active groups can be destroyed, then the oxidation of coal would be restricted and prevented essentially. According to the active structures of coal, this environment-friendly fire-fighting functional ionic liquid should be hydrophilic and stable in water, and be effective in dissolving active groups and the produced dangerous gases, inhibiting oxidation and conducting reaction heat, thus it can be possible to be applied in suppressing spontaneous combustion in the underground coal mine goaf. Using environment-friendly functional ionic liquid to fight mine spontaneous fire will provide a possible research direction for safety technologies in mining.

Solvent extraction of americium(III) and europium(III) from nitric acid medium is carried by the solution of a functionalized ionic liquid (FIL), 1-butyl-3-methylimidazolium hexafluoro 1,3-diketonate ([C4mim][hfac]) present in 1–butyl–3–methylimidazolium bis(trifluoromethane-sulfonyl)imide, ([C4mim][NTf2]) diluent. The distribution ratio of Am(III) and Eu(III) was measured as a function of pH, concentration of FIL, nature of diluent and temperature. The D values increases with increase in pH. The slope analysis method revealed involvement of three FILs in the complexation. Complete removal of metal ion from extracted phase using the nitric acid. A separation factor of 25 was achieved for Am(III) over Eu(III) using polycarboxylic acid (DTPA) solution.

Chapter 6 - Ionic liquids as scavenger

Environmentally friendly iron(II) catalysts for atom-transfer radical polymerization (ATRP) were synthesized by careful selection of the nitrogen substituents of N,N,N-trialkylated-1,4,9-triazacyclononane (R3 TACN) ligands. Two types of structures were confirmed by crystallography: "[(R3 TACN)FeX2 ]" complexes with relatively small R groups have ionic and dinuclear structures including a [(R3 TACN)Fe(μ-X)3 Fe(R3 TACN)](+) moiety, whereas those with more bulky R groups are neutral and mononuclear. The twelve [(R3 TACN)FeX2 ]n complexes that were synthesized were subjected to bulk ATRP of styrene, methyl methacrylate (MMA), and butyl acrylate (BA). Among the iron complexes examined, [{(cyclopentyl)3 TACN}FeBr2 ] (4 b) was the best catalyst for the well-controlled ATRP of all three monomers. This species allowed easy catalyst separation and recycling, a lowering of the catalyst concentration needed for the reaction, and the absence of additional reducing reagents. The lowest catalyst loading was accomplished in the ATRP of MMA with 4 b (59 ppm of Fe based on the charged monomer). Catalyst recycling in ATRP with low catalyst loadings was also successful. The ATRP of styrene with 4 b (117 ppm Fe atom) was followed by precipitation from methanol to give polystyrene that contained residual iron below the calculated detection limit (0.28 ppm). Mechanisms that involve equilibria between the multinuclear and mononuclear species were also examined.

The Baylis–Hillman reaction is a general and multifaceted method for CC bond formation in organic synthesis. Using electrospray ionization mass spectrometry in both the positive and negative ion modes, we performed on‐line monitoring of the reaction in the presence of imidazolium ionic liquids. Loosely bonded supramolecular species formed by coordination of neutral reagents, products and the protonated forms of zwitterionic Baylis–Hillman intermediates with cations and anions of ionic liquids were gently and efficiently transferred directly from the solution to the gas phase. Mass measurements and structural characterization of these unprecedented species via collision‐induced dissociation in tandem mass spectrometry experiments were performed. The interception of several supramolecular species indicates that ionic liquids co‐catalyze Baylis–Hillman reactions by activating the aldehyde toward nucleophilic enolate attack and by stabilizing the zwitterionic species that act as the main BH intermediates. Copyright © 2006 John Wiley & Sons, Ltd.

A label-free electrochemical immunosensor for cardiac troponin I was prepared by using a helical carbon nanotube-supported aldehyde-functionalized ionic liquid. Because of the good conductivity of ionic liquid and helical carbon nanotubes, high sensitivity of the immunosensor was obtained. Functionalized ionic liquid provided binding sites for antibody, which simplified the process of sensor construction. Cardiac troponin I was detected by this immunosensor with a linear range of 0.05–30 ng/mL and a detection limit of 0.03 ng/mL. The electrochemical immunosensor had satisfactory reproducibility, high sensitivity, and acceptable specificity.

Probing the coordination of europium(III) in a functionalized ionic liquid using luminescence spectroscopy

The purpose of this investigation was the synthesis of functionalized ionic liquids with long chain of carbon in order to increase their lipophilicity starting from imidazole. Synthesis of some ionic liquids ILs 3 a-b is described starting from imidazole 1. The starting material is converted under microwave irradiation to N-alkyl imidazole (1a-b) which reacted with allylbromide to give functionalized N-alkyl, N’-allyl imidazolium bromide (2a-b). Hydroboration followed by methanolysis and acid hydrolysis applied to these give the target compounds 3 a-b in good yields. In comparison to the conventional method, we synthesised some functionalized acid ionic liquids starting from imidazole with high yield using microwave irradiation, avoiding the long reaction time and the risk of product degradation.

Highly ordered mesoporous functionalized pyridinium protic ionic liquid framework as a highly efficient catalytic system in chemoselective thioacetalization of carbonyl compounds under solvent-free conditions

Recent advances in the application of ionic liquid-modified silica gel in solid-phase extraction