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1.
Fritz E. Kühn Jin Zhao Wei Sun Luis C. Branco Isabel S. Gonçalves Carlos C. Romão 《Tetrahedron letters》2005,46(1):47-52
Complexes of the type (η5-C5R5)Mo(CO)3X (X = Me, Cl; R = H, Me), being efficient homogeneous catalysts for the epoxidation of olefins, have been examined for their catalytic performance at 55 °C in systems containing room temperature ionic liquids (RTILs) of composition [BMIM]NTf2, [BMIM]PF6, [C8MIM]PF6 and [BMIM]BF4. The catalytic performance for cyclooctene epoxidation depends strongly on the water content of the system, the catalyst solubility in the RTIL, and the reaction behaviour of the RTIL under the applied reaction conditions. The catalysts can be recycled without significant loss of activity when a reaction system containing [BMIM]NTf2 and [BMIM]PF6 in a 4:1 relationship is used. High proportions of [BMIM]PF6 lead to a ring opening reaction (diol formation), due to HF formation and the presence of residual water. 相似文献
2.
《Comptes Rendus Chimie》2014,17(1):18-22
A series of novel protic ionic liquids were immobilized on alanine, a cheap readily available amino acid. These short aliphatic chain ionic liquids have a low cost of preparation, a low toxicity, and need simple synthesis/purification processes. Their catalytic activity was tested for citral–acetone and benzaldehyde–acetone condensations, two reactions with an interest for pharmacological as well as flavor and fragrance industry. Good results were obtained in terms of conversion and selectivity; moreover, the catalysts can be recycled and reused for several consecutive cycles without significant loss of activity. 相似文献
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4.
Olefin self-cross-metathesis (CM) reactions catalyzed by the second-generation Grubbs carbene complex have been compared in dichloromethane and two kinds of selected room temperature ionic liquids (RTILs). Both the catalyst and the ionic liquids could be simply recovered and reused for at least four cycles just with a little drop in activity. Significant enhancements in the reactivity, yield and reaction rate were achieved. 相似文献
5.
《Journal of Coordination Chemistry》2012,65(3):548-559
A new cis-dioxo molybdenum(VI) complex was obtained by reaction of 2,4-dihydroxybenzylidene(5-N,N-methylphenylamino-1,3,4-thiadiazol-2-yl)hydrazone as ligand and [MoO2(acac)2] in methanol and was characterized by elemental analyses, 1H NMR, IR, and electronic spectroscopic studies. The complex was also analyzed by single-crystal X-ray diffraction. The structure determination revealed a distorted octahedral coordination geometry around molybdenum in which the tridentate NNO donor (L2–) is bonded to [MoO2]2+ through phenolic oxygen, hydrazinic nitrogen, and thiadiazole nitrogen. The sixth coordination site is occupied by a weakly bonded methanol. The complex was tested as a catalyst for homogeneous epoxidation of olefins using tert-butyl hydrogen peroxide as an oxidant. In the homogeneous catalytic system, the reactions are efficiently carried out with high yields and selectivity. 相似文献
6.
《Physics and Chemistry of Liquids》2012,50(3):257-268
The formation constants of species formed in the systems H+?+?W(VI)?+?nitrilotriacetic acid (NTA) and H+?+?NTA have been determined in aqueous solution for pH?=?4–9 at 25°C and different ionic strengths ranging from 0.1 to 1.0?mol?dm?3 NaClO4, using potentiometric and spectrophotometric techniques. It was shown that tungsten(VI) forms a mononuclear 1?:?1 complex with NTA of the type WO3L3? at pH?=?7.5. The composition of the complex was determined by the continuous variations method. The complexation of molybdenum(VI) with glutamic acid was investigated in aqueous solution ranging in pH from 4 to 9, using polarimetric, potentiometric and spectrophotometric techniques. The composition of the complex was determined by the continuous variations method. It was shown that molybdenum(VI) forms a mononuclear 1?:?1 complex with glutamic acid of the type MoO3L2? at pH?=?6.0. The dissociation constants of glutamic acid and the stability constants of the complex were determined at 25°C and at ionic strengths ranging from 0.1 to 1.0?mol?dm?3 sodium perchlorate. In both complex formation reactions the dependence of the dissociation and stability constants on ionic strength is described by a Debye-Huckel type equation. Finally, a comparison has been made between the patterns of ionic strength dependence for the two complexes and the results have been compared with data previously reported. 相似文献
7.
Priyabrat Dash Nicole A. Dehm Robert W.J. Scott 《Journal of molecular catalysis. A, Chemical》2008,286(1-2):114-119
Metallic and bimetallic PdAu nanoparticles were solubilized in 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid (IL) by a phase-transfer method using poly(vinylpyrrolidone) (PVP) as a stabilizer. Nanoparticles were characterized by UV–vis spectroscopy and transmission electron microscopy. The bimetallic PdAu nanoparticles in the IL-phase were examined as catalysts for hydrogenation reactions; both the activity and selectivity of the hydrogenation reactions could be tuned by varying the composition of the bimetallic nanoparticles, with maximum activities seen at 1:3 Au:Pd ratios. These nanoparticles/IL catalysts were recycled and then reused for further catalytic reactions with minimal loss in activity. 相似文献
8.
Roberta Bernini Enrico Mincione Giancarlo Fabrizi Gianfranco Battistuzzi 《Tetrahedron》2004,60(4):967-971
A convenient and efficient procedure for the epoxidation of chromone, isoflavone, and chalcone derivatives using 1-butyl-3-methyl imidazolium tetrafluoroborate [bmim]BF4 as solvent and alkaline hydrogen peroxide as oxidant is described. All reactions proceed in good yields and faster than in conventional solvents. No evidence of formation of compounds derived from the opening of the epoxide ring was attained. 相似文献
9.
Jin Zhao 《Journal of organometallic chemistry》2006,691(10):2199-2206
Ansa-bridged η5-cyclopentadienyl carbonyl molybdenum complexes were synthesized with stereogenic centers located in the side chain. An exemplary X-ray crystal structure and the catalytic activity for asymmetric olefin epoxidation are reported. In non-chiral epoxidation the compounds show a good catalytic activity, comparable to activities observed for the related non-chiral complexes of composition CpMo(CO)3X (X = Cl, CH3). For the asymmetric epoxidation of trans-β-methylstyrene the chiral induction is up to ca. 20%. The high ring strain of the ansa-bridged system hampers, unfortunately, its stability under oxidative condition. 相似文献
10.
Joachim E. Dengler 《Journal of organometallic chemistry》2011,696(24):3831-3835
HCo(CO)4 is known to be the active species in the cobalt-catalyzed hydroformylation reaction. Although it is known that the anion [Co(CO)4]− is catalytically inactive, some cobalt carbonyl-containing ionic liquids are surprisingly able to catalyze hydroformylation reactions. However, only ionic liquids with protic cations demonstrate activity, whilst aprotic cations such as BMIM+ result in a completely inactive compound. The four applied cobalt-containing ionic liquids differ only by the cation component. Their different performance in catalytic activity allows the presumption of cooperative effects between the cation and the anion. These fundamental influences of the cation on the hydroformylation kinetics give hints for the reaction mechanism of biphasic hydroformylation reactions as well as on the reaction pathways of the conventional hydroformylation reaction under different reaction conditions. 相似文献
11.
Ana C. Gomes Rita P. Lopes Isabel S. Gonçalves 《Journal of organometallic chemistry》2011,696(22):3543-3550
The ligand N-(n-propyl)-2-pyridylmethanimine (pyim) and an immobilised analogue of this ligand (MCM-41-pyim) were prepared by the condensation reaction of 2-pyridinecarboxaldehyde with either propylamine or aminopropyl groups covalently attached to the ordered mesoporous silica MCM-41. Free and immobilised tetracarbonyl complexes of the type cis-[Mo(CO)4(L)] (L = pyim (1), MCM-41-pyim) were then prepared by microwave-assisted heating of a mixture of Mo(CO)6 and the organic ligand or ligand-silica in toluene at 110 °C for 30-45 min. The products were characterised by NMR spectroscopy (1H, 13C and 29Si, in solution and in the solid state), elemental analysis, N2 adsorption, and FT-IR spectroscopy. When used as catalyst precursors for the epoxidation of cis-cyclooctene by tert-butylhydroperoxide at 55 °C (1 mol% catalyst (Mo), no additional co-solvent), 1,2-epoxy-cyclooctane was obtained as the only reaction product in quantitative yield after 5 h for 1 and 36% yield after 24 h for the supported complex. The use of the ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate as co-solvent led to lower catalytic activities (epoxide selectivity was always 100%) but allowed the catalyst/IL mixtures (homogeneous mixture for IL+1 and a biphasic solid + IL system for IL+MCM-41-pyim/Mo) to be easily recovered and reused in subsequent runs without loss of catalytic performance. 相似文献
12.
Jacek CybulskiAnna Wi?niewska Anna Kulig-AdamiakZbigniew D?browski Tadeusz PraczykAlicja Michalczyk Filip WalkiewiczKatarzyna Materna Juliusz Pernak 《Tetrahedron letters》2011,52(12):1325-1328
A group of quaternary ammonium mandelates and l-prolinates, as ionic liquids, were synthesized and characterized. The prepared salts were soluble in water and showed high surface activity. The described synthesis of l-prolinate was simple and the obtained ionic liquid contained a chiral anion. l-Prolinate in CH2Cl2 was employed for the asymmetric Michael addition of a ketone to nitrostyrene. A yield of 60%, enantioselectivity (upto 50% ee), and good diastereoselectivity (syn/anti ratio of up to 90:10) were obtained for the asymmetric addition of cyclohexanone. These novel ionic liquids proved to be very effective anti-microbial and anti-fungal agents, especially didecyldimethylammonium l-prolinate. Additionally, it was found that phytotoxicity can be a useful tool in assessing the optical forms of ionic liquids. 相似文献
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Hydrogen peroxide was generated in room temperature ionic liquids by electrolysis, which was then used for the epoxidation of lipophilic alkenes under a carbon dioxide-saturated environment and in the presence of catalytic amount of manganese salt. 13C NMR showed that the active peroxymonocarbonate (HCO4−) was generated from the mixture of H2O2, CO2, and water in the ionic liquids. Most lipophilic alkenes were selectively epoxidized within 4-5 h. The ionic liquids can be recovered and reused without any deterioration in the performance. 相似文献
15.
New room-temperature ionic liquids were synthesized from natural and easily available feedstocks (choline hydroxide and amino acids) following an economical and green route in which the only by-product was water. They were successfully applied as catalysts for the Knoevenagel test reaction between benzaldehyde and different active methylene compounds, at room temperature and under solvent-free conditions, to produce α,β-unsaturated carbonyl compounds, exhibiting good conversions and high selectivities. The catalytic role of cholinium and aminoacetate ions in the Knoevenagel condensation is discussed. 相似文献
16.
The effect of four ionic liquids on the porous texture of silica aerogels synthesized from mixed tetramethoxysilane and methyltrimethoxysilane
and dried by the CO2 supercritical method, was studied. Two of these ionic liquids were composed of BF4
− anions while the other two included Cl− anions. The synthesis of gels from ionic liquids did not require another acidic catalyst for silica hydrolysis, nor a basic
catalyst for silica condensation. These aerogels were compared with traditional aerogels made according to a double step catalysis,
which first involved hydrolysis with HCl followed by condensation with pH 9 Tris HCl buffer. Gel mass analysis and thermogravimetric
data showed that, when the initial molar of ionic liquid to Si was 1.58, only ~2% (by mass) of the initial ionic liquids consisting
of BF4
− anions and ~10% (by mass) of ionic liquids containing Cl− anions, remained in the aerogels after supercritical drying. Moreover, X-ray diffraction confirmed that in ionic liquids
based on BF4
− anions, evaporation of the volatile components before supercritical CO2 drying led to the formation of regularly ordered mesopores. 相似文献
17.
Kevin D. ClarkAuthor Vitae Omprakash NachamAuthor VitaeJeffrey A. PurslowAuthor Vitae Stephen A. PiersonAuthor VitaeJared L. Anderson 《Analytica chimica acta》2016
Magnetic ionic liquids (MILs) have recently generated a cascade of innovative applications in numerous areas of analytical chemistry. By incorporating a paramagnetic component within the cation or anion, MILs exhibit a strong response toward external magnetic fields. Careful design of the MIL structure has yielded magnetoactive compounds with unique physicochemical properties including high magnetic moments, enhanced hydrophobicity, and the ability to solvate a broad range of molecules. The structural tunability and paramagnetic properties of MILs have enabled magnet-based technologies that can easily be added to the analytical method workflow, complement needed extraction requirements, or target specific analytes. This review highlights the application of MILs in analytical chemistry and examines the important structural features of MILs that largely influence their physicochemical and magnetic properties. 相似文献
18.
The reactivity of E- and Z-phenylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole in the presence of CuCl2 and Cu(ClO4)2·6H2O has been studied in four imidazolium ionic liquids [bmim][X] (X=BF4−, PF6−, SbF6− and CF3SO3−). The reaction may follow different mechanistic patterns, depending on the nature of the ionic liquid anion, accounting for both qualitative and kinetic data. In the presence of CuCl2, two processes take place at the same time, i.e., the E?Z isomerization and the rearrangement of Z-isomer into the relevant 4-benzoylamino-2,5-diphenyl-1,2,3-triazole. In contrast, in the presence of Cu(ClO4)2·6H2O, the rearrangement occurs only in solution of [bmim][BF4] and [bmim][CF3SO3]. Collected data show that the effect of the ionic liquid on the isomerization and the rearrangement is different. In particular, a higher cross-linking degree seems to favour the triazole, but disfavour the E?Z isomerization. 相似文献
19.
The present work explores in detail the Diels-Alder reaction between cyclopentadiene and a series of dienophiles, performed in an innovative medium such as an ionic liquid. The potential activation of different Lewis acid catalysts and their load effect when used in combination with this solvent have been explored, in order to settle the improvement on rates and selectivities. 相似文献
20.
Poly(ethylene terephthalate) (PET) from an industrial manufacturer was depolymerized by ethylene glycol in the presence of a novel catalyst: ionic liquids. It was found that the purification process of the products in the glycolysis catalyzed by ionic liquids was simpler than that catalyzed by traditional compounds, such as metal acetate. Qualitative analysis showed that the main product in the glycolysis process was the bis(hydroxyethyl) terephthalate (BHET) monomer. Thermal analysis of the glycolysis products was carried out by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The influences of experimental parameters, such as the amount of catalyst, glycolysis time, reaction temperature, and water content in the catalyst on the conversion of PET, selectivity of BHET, and distribution of the products were investigated. Results show that reaction temperature is a critical factor in this process. In addition, a detailed reaction mechanism of the glycolysis of PET was proposed. 相似文献