Showing papers in "Chinese Journal of Chemistry in 2011"

Oxygen Evolution in Overcharged LixNi1/3Co1/3Mn1/3O2 Electrode and Its Thermal Analysis Kinetics

Abstract: The oxygen evolution behavior in overcharged LiNi1/3Co1/3Mn1/3O2-based electrode was investigated by differential scanning calorimetry and thermal gravimetric (DSC/TG). Meantime, its thermal kinetic parameters were calculated by Kissinger's and Ozawa's method. As observed by DSC/TG, two exothermic peaks at 239 and 313°C in washed cathode (4.6 V), were attributed to two steps of oxygen evolution. More importantly, the temperature of its oxygen release processes decreased obviously compared with that charged to 2.8 V. Activation energy (E) for the first and second oxygen evolution, both of which were assumed closely to be the first order reaction, between 200 and 350°C in Li0.204Ni1/3Co1/3Mn1/3O2-based electrode were calculated as 113.63 and 158.13 kJ·mol−1, respectively and the corresponding Arrhenius pre-exponential factors (A) of 1.05×1011 and 6.46×1013s−1 were also obtained. The different energy barrier of such two steps of oxygen evolution should probably be ascribed to the different bond energy of M–O (M=Mn, Co, Ni).

Preparation of Hydroxypropyl‐β‐cyclodextrin Cross‐linked Multi‐walled Carbon Nanotubes and Their Application in Enantioseparation of Clenbuterol

Abstract: A method of cross-linking multi-walled carbon nanotubes by a nucleophilic substitution of brominated multi-walled carbon nanotubes using hydroxypropyl-β-cyclodextrin anions was studied. The modified multi-walled carbon nanotube samples were characterized using thermogravimetric analysis, energy-dispersive X-ray spectroscopy, transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and Fourier transform infrared spectroscopy. The hydroxypropyl-β-cyclodextrin modified multi-walled carbon nanotubes were used as a chiral stationary phase additive for thin-layer chromatography to separate clenbuterol enantiomers, and the chiral separation factor was increased.

Difluoromethylation of O-, S-, N-, C-Nucleophiles Using Difluoromethyltri(n-butyl)ammonium Chloride as a New Difluorocarbene Source

Abstract: Difluoromethyltri(n-butyl)ammonium chloride 1 was found to be an effective difluorocarbene reagent for O-, S-, N-, C-difluoromethylation under basic conditions. It is particularly remarkable that, when only 1.2 equivalent of reagent 1 was used, the difluoromethylated products were obtained in moderate to excellent yields.

A Recyclable and Highly Effective ZnO‐beta Zeolite as a Catalyst for One‐pot Three‐Component Synthesis of Tetrahydrobenzo[b]pyrans

Abstract: 4H-Benzo[b]pyrans was synthesized under reflux condition in ethanol via condensation of benzaldehyde, malononitrile and dimedone with ZnO-beta zeolite as an inexpensive and effective catalyst. The key features of the reported protocols are good to excellent yields, short reaction time and recovery and reusability of catalytic material.

Furfural Hydrogenation on Nickel‐promoted Cu‐containing Catalysts Prepared from Hydrotalcite‐Like Precursors

Abstract: The nickel-promoted Cu-containing catalysts (CuxNiy-MgAlO) for furfural (FFR) hydrogenation were prepared from the hydrotalcite-like precursors, and characterized by X-ray powder diffraction, inductively-coupled plasma atomic emission spectroscopy, N2 adsorption-desorption, UV-Vis diffuse reflectance spectra and temperature-programmed reduction with H2 in the present work. The obtained catalysts were observed to exhibit a better catalytic property than the corresponding Cu-MgAlO or Ni-MgAlO samples in FFR hydrogenation, and the CuNi-MgAlO catalyst with the actual Cu and Ni loadings of 12.5 wt% and 4.5 wt%, respectively, could give the highest FFR conversion (93.2%) and furfuryl alcohol selectivity (89.2%). At the same time, Cu0 species from the reduction of Cu2+ ions in spinel phases were deduced to be more active for FFR hydrogenation.

Morpholine Catalyzed One‐pot Multicomponent Synthesis of Compounds Containing Chromene Core in Water

Abstract: A series of dihydropyrano[c]chromene was obtained via condensation of aldehyde, malononitrile and 4-hydroxycoumarin in water catalyzed by morpholine, as a one-pot reaction. The significance of our findings relates to reducing the use of organic solvents, potentially toxic and hazardous materials, as well as its simplicity, good yields, mild conditions, and lower costs.

Synthesis, Structural Characterization, and Antimicrobial Activities of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) Complexes of Triazole‐based Azodyes

Abstract: The synthesis and characterization of new transition metal complexes of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with 3-(2-hydroxynaph-1-ylazo)-1,2,4-triazole (HL1) and 3-(2-hydroxy-3-carboxynaph-1-ylazo)-1,2,4-triazole (HL2) have been carried out. Their structures were confirmed by elemental analyses, thermal analyses, spectral and magnetic data. The IR and 1H NMR spectra indicated that HL1 and HL2 coordinated to the metal ions as bidentate monobasic ligands via the hydroxyl O and azo N atoms. The UV-Vis, ESR spectra and magnetic moment data revealed the formation of octahedral complexes [MnL1(AcO)(H2O)3] (1), [CoL1(AcO)(H2O)3]·H2O (2), [MnL2(AcO)(H2O)3] (6) and [CoL2(AcO)(H2O)3] (7), [NiL1(AcO)(H2O)] (3), [ZnL1(AcO)(H2O)]·H2O (5), [NiL2(AcO)(H2O)] (8), [ZnL2(AcO)(H2O)]·10H2O (10) have tetrahedral geometry, whereas [CuL1(AcO)(H2O)2] (4) and [CuL2(AcO)(H2O)2]·5H2O (9) have square pyramidal geometry.. The mass spectra of the complexes under EI-con- ditions showed the highest peaks corresponding to their molecular weights, based on the atomic weights of 55Mn, 59Co, 58Ni, 63Cu and 64Zn isotopes; besides, other peaks containing other isotopes distribution of the metal. Kinetic and thermodynamic parameters of the thermal decomposition stages were computed from the thermal data using Coats-Redfern method. HL2 and complexes 6–10 were found to have moderate antimicrobial activities against Staphylococcus aureus (gram positive), Escherichia coli (gram negative) and Salmonella sp bacteria, and antifungal activity against Fusarium oxysporum, Aspergillus niger and Candida albicans. Also, in most cases, metallation increased the activity compared with the free ligand.

Palladium‐Catalyzed Intramolecular Aminofluorination of Styrenes

Abstract: A novel palladium-catalyzed intramolecular oxidative aminofluorination of styrenes has been developed by using NFSI as fluorinating reagent. This reaction represented an efficient method for the synthesis of 2-aryl-3-fluoropyrrolidine derivatives.

Silica Gel‐Supported Polyphosphoric Acid (PPA/SiO2): An Efficient and Reusable Heterogeneous Catalyst for Facile Synthesis of 14‐Aryl‐14H‐dibenzo[a,j]xanthenes under Solvent‐free Conditions

Abstract: A simple, efficient and green method for the synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes by a one-pot condensation reaction of β-naphthol and aryl aldehydes using silica gel-supported polyphosphoric acid (PPA/SiO2), an effective and reusable catalyst, under solvent-free conditions is described. The present methodology offers several advantages, such as a simple procedure with an easy work-up, short reaction times, high yields, and the absence of any volatile and hazardous organic solvents.

Silica‐bonded S‐sulfonic Acid as a Recyclable Catalyst for Synthesis of 2,3‐Dihydroquinazolin‐4(1H)‐ones

Abstract: 2,3-Dihydroquinazolin-4(1H)-one derivatives were synthesized via a one-pot, three component reaction of isatoic anhydride and an aromatic aldehyde with ammonium acetate or primary amine catalyzed by silica-bonded S-sulfonic acid in ethanol at 80°C. The reaction work-up is simple and the catalyst is easily separated from the products by filtration. The heterogeneous catalyst was recycled for ten runs upon the condensation reaction of isatoic anhydride and 4-chlorobenzaldehyde with ammonium acetate without losing its catalytic activity.

Thermal Behavior Investigation of LiNi1/3Co1/3Mn1/3O2‐Based Li‐ion Battery under Overcharged Test

Abstract: Thermal behavior of its components such as separator, electrolyte, cathode, anode, and each binder were investigated by differential scanning calorimetry and thermal gravimetric (DSC/TG) to explain thermal runaway mechanism of Li-ion battery under overcharged test. DSC results indicated the decomposition reaction temperature of SEI (solid electrolyte interface) layer in anode was at about 126°C. It was found that heat generation in anode under normal charged state increased obviously with the increasing of charged voltage. When the battery was overcharged to 4.6 V or 5.0 V, the onset temperature and heat generation of thermal reaction in anode changed a little, while those in cathode had large increase. It was proposed that thermal behavior in cathode mainly caused by the reaction of electrolyte with evolutional oxygen played a key role to thermal runaway for the studied Li-ion battery under overcharged test.

Carbon-Based Solid Acid as An Efficient and Reusable Catalyst for One-Pot Synthesis of Tetrasubstituted Imidazoles under Solvent-Free Conditions

Abstract: Carbon-based solid acid catalyst was found to be highly efficient, eco-friendly and recyclable heterogeneous catalyst for the multicomponent reaction of benzil, aromatic aldehyde, primary amine and ammonium acetate, giving rise to 1,2,4,5-tetrasubstituted imidazoles in good to excellent yields. The present methodology offers several advantages, such as high yields, short reaction time, mild reaction condition and a recyclable catalyst with a very easy work up.

Validated Method for the Simultaneous Determination of Lisinopril, Pravastatin, Atorvastatin and Rosuvastatin in API, Formulations and Human Serum by RP‐HPLC

Abstract: Lisinopril is found to be useful in hypertension and statins as cholesterol lowering drug. Present work was de- signed for the simultaneous determination of lisinopril in presence of pravastatin, atorvastatin, and rosuvastatin us- ing RP-HPLC method. A Purospher star C18 (5 µm, 25×0.46 cm) column was used with mobile phase consisting of acetonitrile∶water (60∶40 V/V, pH 3.0) with flow rate of 1.0 mLmin -1 and the quantitative evaluation was performed at 225 nm. The retention time of lisinopril was 2.0 min and for pravastatin, rosuvastatin and atorvastatin was found to be 3.1, 4.5 and 8.3 min respectively. Suitability of this method for the quantitative determination of the drugs was proved by validation in accordance with the requirements laid down by International Conference on Harmonization (ICH) guidelines. Application of the suggested procedures were successfully applied to the determi- nation of these compounds in active pharmaceutical ingredient and in pharmaceutical preparations, with high per- centage of recovery, good accuracy and precision.

Selective Adsorption of Co(II) by Mesoporous Silica SBA-15-Supported Surface Ion Imprinted Polymer: Kinetics, Isotherms, and Thermodynamics Studies

Abstract: A novel surface ion imprinted adsorbent [Co(II)-IIP] using polyethyleneimine (PEI) as function monomer and ordered mesoporous silica SBA-15 as support matrix was prepared for Co(II) analysis with high selectivity. The prepared polymer was characterized by Fourier transmission infrared spectrometry, scanning electron microscopy, X-ray diffraction and nitrogen adsorption-desorption isotherm. Bath experiments of Co(II) adsorption onto Co(II)-IIP were performed under the optimum conditions. The experimental data were analyzed by pseudo-first-order and pseudo-second-order kinetic models. It was found that the pseudo-second-order model best correlated the kinetic data. The intraparticle diffusion and liquid film diffusion were applied to discuss the adsorption mechanism. The results showed that Co(II) adsorption onto IIP was controlled by the intraparticle diffusion mechanism, along with a considerable film diffusion contribution. Langmuir, Freundlich and Dubinin-Radushke- vich adsorption models were applied to determine the isotherm parameters. Langmuir model fitted the experiment data well and the maximum calculated capacity of Co(II) reached 39.26 mg/g under room temperature. The thermodynamic data were indicative of the spontaneousness of the endothermic sorption process of Co(II) onto Co(II)-IIP. Co(II)-IIP showed high affinity and selectivity for template ion compared with non imprinted polymer (NIP).

Facile Synthesis of Boronic Acid-Functionalized Magnetic Mesoporous Silica Nanocomposites for Highly Specific Enrichment of Glycopeptides

Abstract: In the work, aminophenylboronic acid (APB)-functionalized magnetic mesoporous silica, which holds the attractive features of high magnetic responsivity and large surface area, was developed to enrich glycopeptides. At first, magnetic mesoporous silica nanocomposites were prepared. And then, the nanocomposites were functioned with glycidoxypropyltrimethoxysilane (GLYMO) for boronic acid immobilization. Due to that the boronic acid group on the surface of magnetic mesoporous silica nanocomposites can form tight yet reversible covalent bond with glycopeptides containing cis-1,2-diols groups, the magnetic mesoporous silica nanocomposites were successfully applied to selective enrichment of glycopeptides. APB functionalized magnetic mesoporous silica was also demonstrated to have high selectivity for the glycopeptides in the presence of a 10-fold excess bovine serum albumin (BSA) over horseradish peroxidase (HRP) in the tryptic digest. We also find that magnetic mesoporous silica has better sensitivity in HRP digest compared with that of commercial aminophenylboronic acid-functionalized magnetic nanoparticles beads. The limit of detection for glycopeptides from glycoprotein HRP is about 0.01 ng/µL.

Synthesis, Characterization, DNA-binding Properties and DNA Cleavage of a New Ternary Copper(II) Complex with Mixed-ligands of Tridentate Schiff Base and 1,10-Phenanthroline

Abstract: A new copper(II) complex, [Cu(naph-leu)phen]CH3OH·0.5H2O, in which naph-leu is the tridentate Schiff base ligand derived from the condensation of 2-hydroxy-1-naphthaldehyde and L-leucine, phen is phenanthroline, has been synthesized and characterized by elemental analyses, IR spectra and single crystal X-ray diffraction. The DNA-binding properties of this complex have been investigated by absorption spectra, fluorescence spectra and circular dichroism (CD) spectra, as well as viscosity measurement. Results show that this copper(II) complex binds to calf thymus DNA (CT-DNA) in an intercalative mode and its intrinsic binding constant Kb is 4.87×103 L·mol−1. Furthermore, the DNA cleavage activity of this copper(II) complex has also been investigated by submarine gel electrophoresis. Interestingly, it was found that this complex can cleave the supercoiled plasmid pBR322 DNA to both nicked and linear forms.

Synthesis of 1-Aryl-1H-indazoles via a Ligand-Free Copper- Catalyzed Intramolecular Amination Reaction

Abstract: A general synthesis of 1-aryl-1-H-indazoles from o-halogenated aryl aldehydes or ketones and aryl hydrazines was described. This protocol included an intermolecular condensation and a ligand-free copper-catalyzed intramolecular Ullmann-type coupling reaction. This method was applied to a wide range of substrates to produce the indazole products in good yields.

Sensitive Voltammetric Detection of Trace Heavy Metals in Real Water Using Multi‐Wall Carbon Nanotubes/Nafion Composite Film Electrode

Abstract: Multi-wall carbon nanotubes (MWCNTs) and Nafion composite film (MWCNTs/Nafion) were used for fabricating electrochemical sensors for the voltammetric detection of trace lead(II) and cadmium(II) in several water samples. The morphology and structure of MWCNTs/Nafion film were characterized by scanning electron microscopy (SEM) and infrared spectrum (IR). The electron transfer of MWCNTs/Nafion composite film was examined by cyclic voltammetry (CV) and electrochemical impedance spectrum (EIS). Various experimental parameters, which influenced the response of MWCNTs/Nafion/GC to target metals, were optimized. The results showed that the synergistic effect was obtained on the MWCNTs/Nafion/GC whose sensitivity and stability were better than those of Nafion-coated electrode (Nafion/GC) or CNTs/GC. Stability of the Pb(II) and Cd(II) stripping signals was excellent with relative standard deviations (RSD) within 5% (n=10) from one electrode preparation to another, and RSD of 30 µg·L−1 Pb(II) and Cd(II) were 2.8% and 3.2% for 20 repeated analysis on one single CNTs/Nafion/GC. Over 50 runs, the stability of Pb and Cd detection at the MWCNTs/Nafion conposites electrode was still satisfactory with RSD lower than 6.0%. The determination limits (S/N=3) of the proposed method were determined to be 100 ng·L−1 for Pb and 150 ng·L−1 for Cd. Finally, the MWCNTs/Nafion/GC was successfully applied to determine Pb(II) and Cd(II) in different water samples with recoveries of 97%–103% for Pb and 96%–104% for Cd.

Eco‐friendly and Efficient Synthesis of 2,3‐Dihydroquinazolin‐4(1H)‐ones

Abstract: A simple and facile method for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones through the direct cyclocondensation of one-pot three-component cyclocondensation of isatoic anhydride, ammonium acetate (or primary amines) and aldehydes; and anthranilamide and aldehydes using silica supported ferric chloride (SiO2-FeCl3) as catalyst under solvent-free conditions is described.

SO3H-Functionalized Ionic Liquids:Green, Efficient and Reusable Catalysts for the Facile Dehydration of Aldoximes into Nitriles

Abstract: Easily synthesized aldoximes have been converted to the corresponding nitriles under very mild conditions by a simple reaction using two halogen-free SO3H-functionalized ionic liquids, 3-methyl-1-(4-sulfonic acid)butylimi- dazolium hydrogen sulfate [MIM(CH2)4SO3H][HSO4] and 1-(4-sulfonic acid)butylpyridinium hydrogen sulfate [PY(CH2)4SO3H][HSO4], as catalyst and reaction medium without any additional organic solvent. The method was equally effective for aromatic aldoximes bearing electron-donating and electron-withdrawing substituents. Taking into account environmental and economical consideration, the protocol presented here has the merits of environmentally friendly, simple operation, easy work-up and very good yields. The catalysts could be recycled and reused for several times without noticeably decreasing in their catalytic activities.

One‐pot Green Procedure for Synthesis of Tetrahydrobenzo[a]xanthene‐11‐one Catalyzed by Brønsted Ionic Liquids under Solvent‐free Conditions

Abstract: An efficient one-pot condensation of β-naphthol, aldehydes and cyclic 1,3-dicarbonyl compound has been achieved with ionic liquids as catalyst, thus a variety of 8,9,10,12-tetrahydrobenzo[a]xanthen-11-one derivatives were prepared in good yields. The present approach offers several advantages such as shorter reaction times, good yields and mild reaction conditions.

Efficient Multi‐component Synthesis of Highly Substituted Imidazoles Utilizing P2O5/SiO2 as a Reusable Catalyst

Abstract: Phosphorus pentoxide supported on silica gel (P2O5/SiO2) has been used as an efficient and reusable catalyst for the one-pot pseudo four-component synthesis of 2,4,5-trisubstituted imidazoles from benzil or benzoin, aldehydes, and ammonium acetate. It was also used for four-component preparation of 1,2,4,5-tetrasubstituted imidazoles from benzil or benzoin, aldehydes, primary amine, and ammonium acetate under thermal solvent-free conditions. The remarkable features of this new procedure are high conversions, cleaner reaction, simple experimental and work-up procedures and also the catalyst can be easily separated from the reaction mixture and reused several times without any loss of its activity.

Erratum: Synthesis and Characterization of Nano‐sized Zinc Oxide Coating on Cellulosic Fibers: Photoactivity and Flame‐ retardancy Study

Abstract: We have investigated the effect of zinc oxide as a photocatalyst and durable flame-retardant on cellulosic fibers. Zinc oxide nanocrystals were successfully synthesized and deposited onto cellulosic fibers using sol-gel process at low temperature. The samples were characterized by means of several techniques such as scanning electron microscopy, transmission electron microscopy, diffuse reflectance spectroscopy, X-ray diffraction and thermogravimetric analysis. The photocatalytic activity was tested by measuring the photodegradation of methylene blue under UV-Vis illumination. Moreover, flame-retardancy was tested by vertical flame spread test. The optimum add-on value for donating flame-retardancy onto cellulosic fabric was obtained to be in the range of 15.24 to 23.20 g of the ZnO per 100 g of fabric. Thermogravimetric analysis of pure and flame-retarded samples were accomplished and discussed. The results obtained are in agreement with Wall effect theory and Coating theory. The originality of this work on introducing photoactive flame-retarded fibers is highly valuable for industrial implementation.

Fe3O4/ZnS Hollow Nanospheres: A Highly Efficient Magnetic Heterogeneous Catalyst for Synthesis of 5-Substituted 1H-Tetrazoles from Nitriles and Sodium Azide

Abstract: An efficient route for the synthesis of 5-substituted 1H-tetrazole via [2+3] cycloaddition of nitriles and sodium azide is reported using Fe3O4/ZnS hollow nanospheres as a magnetic separable heterogeneous catalyst. The catalyst is very efficient, affording excellent yields and can be reused for several circles. In addition, the Fe3O4 inner shell exhibits magnetism, making the catalyst easily separated by a magnet.

Synthesis of Pyrazolo[3,4‐d]pyrimidin‐4‐ones Catalyzed by Br?nsted‐acidic Ionic Liquids as Highly Efficient and Reusable Catalysts

Abstract: A convenient and efficient method for the synthesis of pyrazolo[3,4-d]pyrimidin-4-ones via heterocyclization reaction of 5-amino-1H-pyrazole-4-carboxamides with triethyl orthoesters using two Br?nsted-acidic ionic liquids, 3-methyl-1-(4-sulfonic acid)butylimidazolium hydrogen sulfate [MIM+(CH2)4SO3H][HSO4−] or N-(4-sulfonic acid)butyl triethylammonium hydrogen sulfate [Et3N+(CH2)4SO3H][HSO4−], as efficient homogeneous catalysts under solvent-free conditions is described.

On Water: Br?nsted Acidic Ionic Liquid [(CH2)4SO3HMIM][HSO4] Catalysed Synthesis of Oxindoles Derivatives

Abstract: Some oxindoles derivatives are synthesized from the condensation of indoles with isatins in the presence of green and recycable catalyst [(CH2)4SO3HMIM][HSO4] in water at room temperature.

A Convenient Method for the Preparation of 1,5-Diaryl-3-(arylamino)-1H-pyrrol-2(5H)-ones

Abstract: A simple and eco-friendly method for the preparation of 1,5-diaryl-3-（arylamino）-lH-pyrrol-2（5H）-ones via the cyclo-condensation reaction of aldehydes, amines and ethyl pyruvate in the presence of silica supported ferric chlo- ride （SiO2-FeCl3） as reusable heterogeneous catalyst is described. The present methodology offers several advantages such as excellent yields, simple procedure and short reaction times.

Synthesis, Characterization and Thermal Properties of Energetic Compounds Derived from 3-Amino-4-(tetrazol-5-yl)furazan

Abstract: Five energetic compounds, 3,3-bis(tetrazol-5-yl)-4,4-azofurazan (DTZAF), 3-nitro-4-(tetrazol-5-yl)furazan (NTZF), hydrazinium 3-amino-4-(tetrazol-5-yl)furazan (HATZF), triaminoguanidinium 3-amino-4-(tetrazol- 5-yl)furazan (TAGATZF) and guanylureaium 3-amino-4-(tetrazol-5-yl)furazan (MATZF), were prepared using 3-amino-4-(tetrazol-5-yl)furazan (ATZF) as starting material and their structures were characterized by FT-IR, 1H NMR, 13C NMR and elemental analysis. The properties of NTZF were estimated:density is 1.67 g/cm3, enthalpy of formation +415.41 kJ/mol and detonation velocity 8257.83 m/s. The main thermal properties of four compounds, DTZAF, HATZF, TAGATZF and MATZF, were analyzed by TG and DSC techniques and the results showed that their melting points are 251.9, 159.7, 205.4 and 211.4°C, respectively, and their first decomposition temperatures are 256.7, 258.6, 231.7 and 268.6°C, respectively. The fact that their decomposition temperatures were over 230°C showed that they exhibit better thermal stability.

Effect of Organic Additives on the Performance of Nano-sized Ru-Zn Catalyst

Abstract: A novel Ru-Zn catalyst was prepared by coprecipitation. The catalyst was characterized by XRF, XRD and TEM. The effects of organic additives on the performance of the Ru-Zn catalyst for benzene selective hydrogenation to cyclohexene were investigated. The results showed that the catalyst was composed of Ru and Zn in molar ratio of 33.8:1, and the most probable value of the Ru crystallite size in the catalyst was 5.1 nm. The modification of Ru with Zn and the small size effect were the main cause why the catalyst exhibited the high activity and the excellent cyclohexene selectivity. When PEG (polyethylene glycol) was used as an additive, the activity of the catalyst decreased, and the cyclohexene selectivity increased with the increase of the PEG molecular weight. With the addition of PEG-20000, a cyclohexene selectivity of 78.9% at a benzene conversion of 68.7% and a maximum cyclohexene yield of 61.4% were obtained. With diethanolamine and triethanolamine as additives, cyclohexene yields were as high as 58.9% and 58.2%, respectively.

An Efficient Synthesis of 2‐Substituted Benzoxazoles via RuCl3·3H2O Catalyzed Tandem Reactions in Ionic Liquid

Abstract: An efficient synthesis of 2-substituted benzoxazoles through RuCl3·3H2O catalyzed, air oxidized tandem reactions of 2-aminophenols and aldehydes in [bmim]BF4 was developed. This synthetic strategy has such advantages as mild reaction conditions, cost-free oxidant, readily available starting materials, and recyclable catalyst and solvent. As an application, it was successfully used in the synthesis of the unreported 5-(benzoxazol-2-yl)-2′-deoxyuridines with potential biological activities.