Well-posedness and generalized metric subregularity with respect to an admissible function

Science China Mathematics - In the framework of complete metric spaces, this paper provides several sufficient conditions for the well-posedness with respect to an admissible function, which...     

Pt/ZrO2-Al2O3催化剂催化氧化C3H6和CO性能

采用共沉淀法合成了ZrO₂与Al₂O₃的不同质量比的ZrO₂-Al₂O₃复合氧化物,并以此为载体通过等体积浸渍法制备了1.5% Pt/ZrO₂-Al₂O₃（w/w）催化剂。以C₃H₆和CO为反应物的催化性能评价显示,在系列催化剂中以Pt/Zr（0.4）-Al催化剂催化氧化活性最为优异,其C₃H₆和CO的起燃温度（T₅₀）小于125℃,完全转化温度（T₉₀）小于150℃。采用XRD、低温N₂吸附、H₂-TPR、CO脉冲吸附等分析表征技术探索了催化剂物相结构、比表面积、颗粒尺寸等对催化活性的影响规律。结果发现,ZrO₂-Al₂O₃复合氧化物具有Al₂O₃材料的介孔织构和大比表面积特性,且产生了Al_xZr_1-xO_y固溶体新物相。适当的ZrO₂与Al₂O₃的质量比,是改善Pt与ZrO₂-Al₂O₃的相互作用强度,促进贵金属Pt的分散,提升Pt/ZrO₂-Al₂O₃催化剂的低温氧化活性的关键。     

Preparation of walnut shell-based activated carbon and its properties for simultaneous removal of H2S,COS and CS2 from yellow phosphorus tail gas at low temperature

Research on Chemical Intermediates - Walnut shell-based activated carbon (WSBAC) was prepared used to simultaneously remove H2S, COS and CS2 from yellow phosphorus tail gas and closed carbide...     

Scalable total synthesis of horsfiequinone A

Starting from two commercially available substrates, methoxyhydroquinone and piperonyl alcohol, a scalable four-step total synthesis of horsfiequinone A was developed. The notable feature of the synthesis is the application of two continuous sequential transformations. Namely, the key aldehyde 9 and horsfiequinone A were prepared via scalable Wittig/hydrolysis and Wittig/catalytic hydrogenation/oxidation sequences, respectively. Importantly, the synthetic route required only three recrystallizations and one column chromatography purification step.     

Synergistic Pd/Cu-catalyzed regio- and stereoselective cascade Heck cyclization/borylation/cross-coupling

A cooperative Pd/Cu-catalyzed three-component cross-coupling reaction of alkynes, B₂Pin₂ and alkene-tethered aryl halides is reported. This reaction proceeds under mild conditions and shows broad substrate scope, providing a variety of heterocycles containing tetrasubstituted alkenylboronate moieties in synthetically useful yields with excellent chemoselectivity and regioselectivity. This transformation features the catalytic generation of β-borylalkenylcopper intermediates and their use in Pd-catalyzed Heck cyclization/cross-couplings. An enantioselective cascade cyclization/cross-coupling process has also been developed for the synthesis of enantiomerically enriched oxindole bearing a tetrasubstituted alkenylboronate moiety.     

B(C6F5)3-Catalyzed Aza-Friedel–Crafts Reaction of Indolizines with 2-Aryl-3H-indol-3-ones

A Friedel–Crafts reaction of indolizines with 2-aryl-3H-indol-3-ones catalyzed by B(C₆F₅)₃ is described. This protocol gives access to indolizine derivatives that are valuable building blocks in synthetic and pharmaceutical chemistry. The reaction proceeds under mild conditions, affording various C2-quaternary indolin-3-ones based on indolizine with high yields and regioselectivities. Moreover, the synthetic transformations of the target products were realized by N-methylation and trifluoromethane sulfonation.     

镍系非晶态合金催化剂的研究进展

镍系非晶态合金催化剂作为一类以镍为主要活性组分的环境友好型催化剂,具有高活性、高选择性和价格低廉等特性,被广泛应用于不饱和化合物的催化加氢、化合物脱硫、硼氢化物水解和燃料电池中的电催化氧化等方面。本文概述了镍系非晶态合金催化剂的结构特点,综述了镍系非晶态合金催化剂近年来国内外的研究状况,重点总结金属助剂、载体、制备方法对镍系非晶态合金催化剂的性能的影响,并对镍系非晶态催化剂的未来研究方向进行了分析展望。     

Inclusion Complex of Podophyllotoxin with γ‐Cyclodextrin: Preparation,Characterization, Anticancer Activity,Water‐Solubility and Toxicity

An inclusion complex of podophyllotoxin (PPT) with γ‐cyclodextrin (γ‐CD) was prepared. The behavior, characterization, and water solubility of the inclusion complex were carefully investigated via fluorescence spectroscopy, thermogravimetry, differential scanning calorimetry, X‐ray diffraction analysis, and ¹H and 2D nuclear magnetic resonance spectroscopy. Furthermore, antitumor activity to human cancer lines and toxicity in mice were studied. Results showed that the inclusion complex formed in a 1:1 ratio with a considerable apparent stability constant K_s (4245.5 L·mol^?1). Water solubility was considerably improved. In addition, the anticancer activity of the inclusion complex was better than that of cis‐platinum (DDP, positive control). Most importantly, the toxicity of podophyllotoxin inclusion complex reduced and became more safety to mice which will be great valuable to research its applications as a kind of antitumor drug to human in the further.     

One-pot synthesis of 1,4-disubstituted 1,2,3-triazoles from nitrobenzenes

A facile synthesis of 1,4-disubstituted 1,2,3-triazoles was achieved from nitrobenzenes and terminal alkynes under mild conditions. The reactions were successful for nitrobenzenes and terminal alkynes bearing various functionalities, from which the 1,2,3-triazole derivatives were smoothly synthesized through a four-step one-pot sequence.     

有关不能全含于半球中的一些曲面的性质讨论

本文主要研究了不能全含于开半球中的一些特殊曲面.利用Lr算子的相关性质,证明了对S~(n+1)中紧致r-极小超曲面,如果第二基本形式的秩rank(h_(ij))r,则其不全含在S~(n+1)的一个开半球中.