Search

We report herein an efficient approach for the enantioselective synthesis of inherently chiral calix[4]arenes via palladium-catalyzed asymmetric intramolecular C-H arylations. Using a chiral bifunctional phosphine-carboxylate ligand, the inherent chirality on macrocyclic scaffolds was induced successfully, from which a wide range of calix[4]arenes with fluorenone motifs were obtained with good yields and excellent enantioselectivities (up to99% ee). The synthetic utility of this method was demonstrated by diverse transformations of the products, thus substantially expanding the chemical space of chiral calix[4]arenes. Further investigations of photophysical and chiroptical properties revealed that calix[4]arenes bearing two fluorenone moieties displayed remarkable

The enantioselective synthesis of axially chiral biaryls by a copper-catalyzed Diels-Alder/retro-Diels-Alder reaction of 2-pyrones with alkynes is reported herein. Using electron-deficient 2-pyrones and electron-rich 1-naphthyl acetylenes as the reaction partners, a broad range of axially chiral biaryl esters are obtained in excellent yields (up to 97% yield) and enantioselectivities (up to >99% ee). DFT calculations reveal the reaction mechanism and provide insights into the origins of the stereoselectivities. The practicality and robustness of this reaction are showcased by gram-scale synthesis. The synthetic utilizations are demonstrated by the amenable transformations of the products.

In this work, a modified pretreatment method using magnetic molecularly imprinted polymers (MMIPs) was successfully applied to study the metabolites of an important botanical with ultraperformance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS). The MMIPs for glucoside-specific adsorption was used to identify metabolites of Pulsatilla chinensis in rat feces. Polymers were prepared by using Fe3O4 nanoparticles as the supporting matrix, d-glucose as fragment template, and dopamine as the functional monomer and cross-linker. Results showed that MMIPs exhibited excellent extraction performance, large adsorption capacity (5.65 mg/g), fast kinetics (60 min), and magnetic separation. Furthermore, the MMIPs coupled with UPLC-Q-TOF-MS were successfully utilized for the identification of 17 compounds including 15 metabolites from the Pulsatilla saponin metabolic pool. This study provides a reliable protocol for the separation and identification of saponin metabolites in a complex biological sample, including those from herbal medicines.

A sonoelectrochemical synthetic method is reported for rapidly preparing and dispersing reduced graphene nanosheets (RGNSECM) stabilized in an aqueous electrolyte. The X-ray photoelectron and Raman results demonstrate that the defects on RGNSECM are predominantly physical and not similar to the chemical defects on reduced graphene nanosheets (RGNCM) synthesized via chemical reduction of graphene oxide nanosheets based on the Hummer's method. The in-plane crystallite size (La) of RGNSECM is 26.8 nm, larger than the 18.2 nm of RGNCM. The RGNs prepared using the sonoelectrochemical method (RGNSECM) were successfully applied as nonenzymatic H2O2 sensors and alkaline oxygen reduction reaction (ORR) catalysts. Using electrochemical analysis, a fair comparison of the performances of RGNSECM and RGNCM as H2O2 sensors and ORR catalysts has been performed.

To develop economical and phosphorus-free catalysts for hydrogenation of ketones, three new complexes, [Ni(1R,2R-dpen)2(H2O)Cl]2Cl2· 2Et2O (1), [Ni(1R,2R-dpen)(phen)(CH3OH)2]Cl2·2CH3OH (2) and [Ni(1,8-dan)2(DMF)Cl]2Cl2· 3H2O (3), and three reported compounds, [Ni(opda)(phen)Cl2]·CH3OH (4), [Ni(opda)2Cl2] (5) and [Ni(1,2-dach)2]Cl2 (6), were prepared and the structures of new compounds were determined by single crystal X-ray diffraction analysis, in which 1R,2R-dpen, phen, 1,8-dan, opda and 1,2-dach denote 1R,2R-1,2-diphenylethylenediamine, 1,10-phenanthroline, 1,8-diaminonaphthalene, o-phenylenediamine and 1,2-diaminocyclohexane, respectively. The catalytic effects for hydrogenation of acetophenone of these compounds were tested. This revealed very poor or no catalytic effects of these complexes in transfer hydrogenation of acetophenone using isopropanol or HCOOHNEt3 as hydrogen source. However, they presented much better catalytic effects in ionic hydrogenation of acetophenone using H2 gas as hydrogen source with a dependence of the catalytic effects on the base used in the hydrogenation reactions. The complexes represent a kind of green hydrogenation catalyst, although the conversion in the hydrogenation reactions is not as high as expected. Copyright © 2010 John Wiley & Sons, Ltd.

Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (1H-NMR), carbon-13 nuclear magnetic resonance (13C-NMR), and group compositional analysis were used to characterize the synthesis reaction of fluidized catalytic cracking (FCC) slurry before and after solvent extraction treatment. This investigation provided a great deal of critical information for use in future process development. Before solvent extraction, the FCC slurry is extremely complex. Saturates content is relatively high, and there are a variety of aromatic ring substituents. In addition, molecular uniformity is poor and chemical steric hindrance is strong. On the contrary, the composition of a fraction enriched in aromatics is relatively simple with excellent uniformity and homogeneous molecular alkyl-substituents. The aromatic enriched fraction (FCCRF) from the FCC slurry has weak chemical steric hindrance and, consequently, is more reactive than the original FCC slurry.

This paper briefly reviews several chromatographic separation methods for analysis of asphalt, and recommends the supercritical fluid extraction as one of the most effective methods for separation and analysis of asphalt. Several different kinds of asphalt have been used as samples. The experimental results are discussed.

The NiII ion of the title compound, [Ni(C2H8N2)(C10H8N2)(H2O)2]Cl2, is coordinated by four N atoms and two water mol­ecules in a distorted octa­hedral geometry. π–π Stacking of pyridine rings from adjacent complexes leads to a one-dimensional supra­molecular ribbon along the b axis. The chloride anions are hydrogen bonded with complex cations, resulting in a three-dimensional supra­molecular architecture.

The manganese(II) coordination polymer, poly[bis­(2,2′-bipyridine)tris­(μ-1,4-phenyl­enediacetato-κ4O,O′:O′′,O′′′)­tri­manganese(II)], [Mn3(C10H8O4)3(C10H8N2)2]n, consists of linear trinuclear building blocks with two crystallographically unique Mn atoms. One MnII ion and the geometric centre of one 1,4-phenyl­enediacetate ligand in the trinuclear unit both lie on inversion centres. Trinuclear units are bridged by 1,4-phenyl­enediacetate ligands to yield a two-dimensional network which stacks into a three-dimensional supra­molecular structure via π–π stacking inter­actions.

In the title compound, [Ni(C2H8N2)(C6H16N2)(H2O)2]Cl2·2H2O, the NiII ion, located on a twofold axis, is coordinated by four N atoms of the ethyl­enediamine and N,N,N′,N′-tetra­methyl­ethylenediamine ligands and two water mol­ecules in a distorted octa­hedral geometry. Hydrogen bonds between ethyl­enediamine, water mol­ecules and chloride ions help to construct a three-dimensional supra­molecular architecture.

The title compound, C2H10N2 2+·2Cl−·2C12H8N2·4H2O, has an inversion centre located midway between the two C atoms of the ethylenediammonium cation. The 1,10-phenanthroline molecules stack along the a axis, and are linked by π–π stacking interactions to form one-dimensional chains. These are bridged by ethylenediammonium cations, via hydrogen bonds, forming two-dimensional supramolecular sheets parallel to the ac plane. Hydrogen bonds to chloride anions and water molecules connect these two-dimensional sheets, resulting in the formation of a three-dimensional supramolecular network.

In the title compound, [Gd(C7H6NO2)3(H2O)] n , a two-dimensional coordination polymer, the eight-coordinate GdIII ions are bridged by two carboxylate groups from two μ2-p-aminobenzoate ligands, forming a centrosymmetric dinuclear block. These blocks are further connected by μ3-p-aminobenzoate ligands, yielding a two-dimensional network. The coordination polymers thus formed are connected via hydrogen bonds, producing a three-dimensional supramolecular structure.

A new thermosetting pitch resin consisting of condensed aromatic nuclei cross-linked with methylene bridges was prepared by polymerization of a mixture of an aromatic rich fraction from fluid catalytic cracking oils and 1,4-benzenedimethanol at 120℃ with p-toluenesulfonic acid as catalyst.Carbon fiber/resin(CFR)and carbon fiber paper/resin(CFPR)composites were prepared by the hot-pressing method.No remarkable changes in mechanical properties were found when the composites were heated at 250℃ for 10h and 300℃ for 2h and soaked in strong acids or bases for 1 to 70h at room temperature,suggesting that the composites had good thermal stability and resistance to chemical attack.The CFR and CFPR specimens were converted into C/C composites without fissures or cleavages between the pitch resin carbon and carbon fibers by further heat treatment from 950 to 1000℃ under N2 atmosphere.The length of carbon fiber pulled out from the matrix during fracture was of the order of 10μm as seen in SEM photos,indicating that the pitch resin adhered well to the carbon fibers and the CFR and CFPR composites had good mechanical strength.

The complex mol­ecule of the title compound, [NiCl2(C6H8N2)(C12H8N2)]·CH4O, has twofold rotation symmetry. The complex has a distorted octa­hedral NiCl2N4 coordination. Hydrogen-bonding and π–π stacking inter­actions help to stabilize the crystal structure.

Porous carbon prepared by KOH chemical activation was doped with boron using B 4 C as an additive (mass fraction of 10%) by heat treatment at 850 °C for 5 h to increase its antioxidative ability. This effect is a result of a decrease in the number of active sites on the surface of the carbon after heat treatment, which inhibits its reaction with the oxidizing gas. The volume of micro and mesopores and BET surface area decreased after the doping. Although the activity of the doped porous carbon in catalytic cracking evaluated in a microreactor decreased after the doping, it still reached a higher value (70%) than that of porous carbon.

In the title compound, [Ni(C6H14N2)(C6H16N2)(H2O)2]Cl2·2H2O, the cation lies about a twofold rotation axis. The octa­hedral complex cation is linked to the Cl− anions by hydrogen bonds to form a layer structure.

In the title compound, [Ni(C6H16N2)2(H2O)2]Cl2, the NiII cation (site symmetry \overline{1}) is coordinated by two N,N-bidentate ligands and two water mol­ecules, resulting in a slightly distorted trans-NiO2N4 octa­hedron. The complex cations and chloride anions are linked by N—H⋯Cl and O—H⋯Cl hydrogen bonds into a chain.