Beckmann rearrangement of several oximes catalyzed by metaboric acid was studied in room temperature ionic liquids. Especially for conversion of cyclohexanone oxime into e-caprolactam, excellent conversion and selectivity were obtained.

★★★☆☆ Keywords: Beckmann rearrangement; Oxime; Metaboric acid; Ionic liquid

★★★☆☆ S. Guo, Y. Deng / Catalysis Communications 6 (2005) 225–228.

Four non-chloroaluminate acidic ionic liquids have been used as catalysts for Pechmann condensations of phenols under solvent-free conditions. SO3H-functionalized trifluoromethanesulfonate imidazolium ionic liquid has proved to be the most active catalyst. Ionic liquid loads as low as 5 mol % can be used leading to high yields with activated phenols at an oil bath temperature of 80 degrees C. The acidities of the four ionic liquids have also been tested using the Hammett method in dichloromethane. The results are consistent with their catalytic activities as observed in the Pechmann reaction of resorcinol. This methodology offers significant improvements for the synthesis of coumarins with regard to yield of products, simplicity in operation, and green aspects by avoiding toxic catalysts and solvents.

★★★☆☆ Keywords: acid catalysis; coumarins; determination of acidity; ionic liquids; Pechmann condensation

★★★☆☆ Adv. Synth. Catal. 2005, 347, 512– 516.

Several novel sulfonyl chloride functionalized ionic materials were used as media and catalysts for Beckmann rearrangement of cyclohexanone oxime and satisfactory results were achieved under mild conditions. The effects of all parameters were discussed. Moreover, the deactivation of ionic liquid catalytic system during the recycle was investigated by using FTIR spectroscopy and mass balance calculation. The trapping of acidic ionic material with basic product is proved to be mainly responsible for the difficulties encountered in the reuse of this type of material. A possible mechanism was conjectured.

★★★☆☆ Keywords: Beckmann rearrangement; Cyclohexanone oxime; Caprolactam; Sulfonyl chloride functionalized ionic materials; IR investigation

★★★☆☆ Z. Du et al. / Journal of Molecular Catalysis A: Chemical 237 (2005) 80–85.

The carbonylation of amines with propargylic alcohol using CO2 as carbonyl source to yield N-substituted 4-methylene-2-oxazolidinones could efficiently proceed in ionic liquids, and various 4-methylene oxazolidinones with high yields could be obtained under relatively mild conditions. This result showed that ionic liquid might be an effective catalyst and reaction medium for the activation of CO2, which also offered a new way to the chemical fixation of CO2.

★★★★☆ Q. Zhang et al. / Tetrahedron Letters 46 (2005) 5907–5911.

The reactions of propargylic alcohols, aliphatic primary amines, and CO2 were conducted in CuCl/[BMIm]BF4 system to produce the corresponding 5-methylene-1,3-oxazolidin-2-ones under relatively mild conditions. The products could be conveniently isolated by means of liquid-liquid extraction. The solvent ionic liquid as well as CuCl catalyst can be recovered and reused three times without appreciable loss of activity. By this green approach, several new 5-methylene-1,3-oxazolidin-2-ones were prepared in excellent yields and purity and were well-characterized.

★★★★☆ J. Org. Chem. 2005, 70, 7376-7380.

A new concept of designing and synthesizing highly dispersed ionic-liquid catalysts was developed through physical confinement or encapsulation of ionic liquids (with or without metal complex) in a silica-gel matrix through a sol-gel process. We studied ionic liquids such as EMImBF4, BuMImBF4, DMImBF4, CMImBF4, BuMImPF6, either with or without [Pd(PPh3)2Cl2] and [Rh(PPh3)3Cl], in a silica-gel matrix (E=ethyl, Bu=butyl M=methyl, D=decyl, C=cetyl and Im=imidazolium). The contents of ionic liquids and loadings of Pd or Rh were 8-53 wt % and 0.10.15 wt %, respectively. Analyses of FT-Raman spectra showed that abnormal Raman spectra of the confined ionic liquids were observed in comparison with the bulk and pure ionic liquids. EMImBF4 and BuMImBF4 ionic liquids could be completely washed out from the silica-gel matrix under vigorous reflux conditions, but ionic liquids with larger molecular size, for example, DMImBF4 or CMImBF4, could be confined into the silica-gel nanopores relatively firmly. These results suggested that the ionic liquids were physically confined or encapsulated into the silica gel. The N2 adsorption measurements indicated that the silica-gel skeleton was mesoporous with 50-110 ? pore size after the BuMImBF4 ionic liquid was removed completely. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis showed that the silica-gel matrix was amorphous and non-uniformly mesoporous. Carbonylation of aniline and nitrobenzene for synthesis of diphenyl urea, carbonylation of aniline for synthesis of carbamates, and oxime transformation between cyclohexanone oxime and acetone were used as test reactions for these catalysts. Catalytic activities were remarkably enhanced with much lower amounts of ionic liquids needed with respect to bulk ionic-liquid catalysts or silica-supported ionic-liquid catalysts prepared with simple impregnation, in which the ionic liquid may be deposited as a thin layer on the support. Such unusual enhancement in catalytic activities may be attributed to the formation of nanoscale and high-concentration ionic liquids due to the confinement of the ionic liquid in silica gel; this results in unusual changes in the symmetry and coordination geometry of the ionic liquids.

★★★★☆ Keywords: carbonylation · catalysis· ionic liquids · nanotechnology ·synthesis design

★★★★☆ Chem. Eur. J. 2005, 11, 5279 – 5288

Novel lactam-cation-based Bronsted acid ionic liquids (ILs) were prepared through a simple and atom-economic neutralization reaction between a lactam, such as caprolactam and butyrolactam, and a Bronsted acid, HX, where X is BF4-, CF3COO-, phCOO(-), ClCH2COO-, NO3-, or H2PO4-. The density, viscosity, acidic scale, electrochemical window, temperature dependency of ionic conductivity, and thermal property of these ILs were measured and investigated in detail. The results show that protonated caprolactam tetrafluoroborate (CPBF) has a relatively strong acidity with -0.22 of Hammett acidic scale Ho and caprolactam trifluoroacetate (CPTFA) and pyrrolidonium trifluoroacetate (PYTFA) ILs possess very low viscosities, that is, 28 cP and 11 cP, respectively. An investigation of thermal property showed that a wide liquid range (up to -90 degrees C), moderate thermal stability (up to 249 degrees C for 10% of decomposition), and complex polymorphism were observed in these ILs. In comparison to imidazolium-cation-based ILs, the lactam-cation-based Bronsted acid ILs have a relatively lower cost, lower toxicity, and comparable ion conductivity and heat storage density (more than 200 MJ/m(3)). They have wide applicable perspectives for fuel cell devices, thermal transfer fluids, and acid-catalyzed reaction media and catalysts as replacements of conventional inorganic acids.

★★★★☆ Zhengyin Du, Zuopeng Li, Shu Guo, Juan Zhang, Laiying Zhu, and Youquan Deng. J. Phys. Chem. B 2005, 109, 19542-19546

A new concept of designing and synthesizing highly dispersed ionic liquids was developed through physical confinement or encapsulation of them into silica gel matrix with sol–gel process. A series of silica gel confined ionic liquids were synthesized through this process and characterized by diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) and FTRaman analysis, and abnormal FT-IR and FTRaman spectra were observed. The silica gel matrixes confined ionic liquid BMImBF4 were further characterized by BET analysis after the ionic liquid was almost completely washed out by acetone under refluxing conditions and meso-porous silica gel matrixes were obtained according to the N2 adsorption measurements, which suggested that the particle-size of the dispersed ionic liquids was in nano-scale. In consideration of the results obtained together, it could be found that the abnormal FT-IR and FTRaman spectra were changed with the poresize of the silica gel matrix. For example, obvious abnormal FT-IR and FTRaman spectra appeared when the particle-size of ionic liquid BMImBF4 is smaller than 11 nm while they disappeared again if the corresponding particle-size >11 nm. These results indicated that nano-effect, or restriction effect, produced from the nano-pores of silica gel was the reason for the abnormal FT-IR and FTRaman spectra.

★★★☆☆ Keywords: Ionic liquids; Silica gel; Abnormal spectra; Nano-material; Characterization

★★★☆☆ F. Shi, Y. Deng / Spectrochimica Acta Part A 62 (2005) 239–244.

Several acid-functional ionic liquids were physically confined into the silica gel through a sol–gel process and used as effective catalysts for deoximation reactions, which proceeded under ambient temperatures without addition of any co-catalysts or oxidizing and reducing agents.

★★★★☆ D. Li et al. / Tetrahedron Letters 45 (2004) 265–268.

The interactions between heavy metals (vanadium and nickel) and kaolin had been investigated by X-ray diffraction and MAT test. In the process of phase transformation of kaolin containing 1–5% vanadium, vanadium-mullite phase emerged surprisingly at 660–700 ◦C. The unit cell size of the mullite was found to increase with increment of vanadium content. As compared with hydro-kaolin, acid-modified kaolin(AMK) and caustic-modified kaolin (CMK) reacted with vanadium to form much more mullite; CMK could even be reacted with nickel to form a rather stable NiAl10O16 compound, and this compound protected zeolite in fluid catalytic cracking catalyst effectively. The catalyst containing AMK had greaterMAT activity retention than that of the contrastive catalyst with hydro-kaolin in the identical level of heavy metal contamination.

★★★☆☆ Keywords: Kaolin; Nickel; FCC catalyst; Vanadium; Mullite; Eutectic; Unit cell size

★★★☆☆ Conghua Liu, Youquan Deng, Yuanqing Pan, Shygin Zheng, Xionghou Gao. Applied Catalysis A: General 257 (2004) 145–150.