Pd-catalyzed carbonylation of diazo compounds at atmospheric pressure: a catalytic approach to ketenes

The carbonylation of carbenes through catalytic cycles is highly desirable due to the importance of ketene-mediated reactions in organic synthesis. In this investigation, a highly efficient and mild catalytic approach toward ketene intermediates has been developed based on Pd-catalyzed carbonylation of diazo compounds with CO. When α-diazocarbonyl compounds or N-tosylhydrazone salts are heated in the presence of a palladium catalyst under atmospheric pressure of CO, ketene intermediates are formed in situ, where they undergo further reactions with various nucleophiles such as alcohols, amines, or imines. The Pd-catalyzed tandem carbonylation-Staudinger cycloaddition gives β-lactam derivatives in good yields with excellent trans diastereoselectivity. The results from DFT calculation on the reaction mechanism suggest that Pd is involved in the [2 + 2] cycloaddition process and affects the diastereoselectivity of the β-lactam products by assisting isomerization of the addition intermediate. On the other hand, the acylketenes generated from the Pd-catalyzed carbonylation of α-diazoketones react with imines in a formal [4 + 2] cycloaddition manner to afford 1,3-dioxin-4-one derivatives. This straightforward carbonylation provides a new approach toward highly efficient catalytic generation of ketene species under mild conditions.     

基于液相色谱-质谱联用技术的代谢组学方法用于中药通心络和人参对过度疲劳大鼠干预作用的评价

用代谢组学方法评价了中药通心络和人参对过度疲劳大鼠的干预作用.通过构造大鼠过度疲劳模型,并分别用通心络和人参进行干预,采用快速液相色谱-离子阱飞行时间质谱(UFLC-IT-TOF-MS)获取大鼠血浆代谢轮廓,并用正交偏最小二乘法(OPLS)进行多变量统计分析,分别找出用于区分通心络和人参干预组大鼠同正常对照大鼠、过度疲...     

Copper-mediated chelation-assisted ortho nitration of (hetero)arenes

A novel copper-mediated chelation-assisted ortho C-H nitration of (hetero)arenes has been developed for the first time, which used dioxygen as terminal oxidant and 1,2,3-TCP as solvent, leading to the synthesis of nitroaromatics with excellent regioselectivity and in good yields. Mechanistic investigations indicate a mechanism involving a four-centered transition state, with simultaneous cleavage of an ortho C-H bond and a N-O bond of the nitrate anion on the 2-arylpyridine-coordinated copper(II) complex.     

Solvent-free cross-dehydrogenative coupling reactions under high speed ball-milling conditions applied to the synthesis of functionalized tetrahydroisoquinolines

Solvent-free reaction using a high-speed ball milling technique has been first applied to cross-dehydrogenative coupling (CDC) reactions between tetrahydroisoquinolines and three types of pronucleophiles such as nitroalkanes, alkynes, and indoles. All coupling products were obtained in good yields at short reaction times (no more than 40 min). When alkynes and indoles were used as pronucleophile, the reactions can be catalyzed efficiently by recoverable copper balls without any additional metal catalyst.     

Constrained large-eddy simulation of turbulent flow over inhomogeneous rough surfaces

In this work we extend the method of the constrained large-eddy simulation(CLES) to simulate the turbulent flow over inhomogeneous rough walls. In the original concept of CLES, the subgrid-scale(SGS) stress is constrained so that the mean part and the fluctuation part of the SGS stress can be modelled separately to improve the accuracy of the simulation result. Here in the simulation of the rough-wall flows, we propose to interpret the extra stress terms in the CLES formulation as the roughness-induced stress so that the roughness inhomogeneity can be incorporated by modifying the formulation of the constrained SGS stress. This is examined with the simulations of the channel flow with the spanwise alternating high/low roughness strips. Then the CLES method is employed to investigate the temporal response of the turbulence to the change of the wall condition from rough to smooth. We demonstrate that the temporal development of the internal boundary layer is just similar to that in a spatial rough-tosmooth transition process, and the spanwise roughness inhomogeneity has little impact on the transition process.     

一类流固耦合系统强解的存在性问题

本文主要讨论一类多刚体与粘性系数依赖于密度的不可压缩流体耦合系统的强解存在性问题.首先,利用变量替换建立本文研究对象对应的非线性微分方程,然后,利用Garlerkin逼近方法获得线性化问题的光滑解,从而可以构造出原问题的逼近解.通过估计逼近解的一致有界性,最后证明了一类描述多刚体在不可压缩流体中运动的耦合系统强解的存在性问题.特别要指出的是在初始密度满足相容性条件下,此结论允许流体内部出现真空.     

圆柱螺旋电磁Wiggler的场形分析

 利用载流圆柱螺旋线系统内部的磁标势满足的Laplace方程, 以及系统磁矢势的积分形式, 定出Laplace方程通解的未知系数, 求得左(右)旋单绕圆柱螺旋线的磁标势。应用磁场的叠加原理以及积分法, 给出了各种类型如双绕、双双绕、交叉绕等螺旋形Wiggler的场形分布公式。     

Arrayed waveguide grating multiplexer with high thermal stability on silicon

In this paper, certain important parameters are optimized for a polymer/Si arrayed waveguide grating (AWG) multiplexer by using grating theory. A 32-channel multiplexer is designed and fabricated using newly synthesized fluorinated poly (ether ether ketone) with a high thermal stability. The measured wavelength channel spacing is 0.796 nm, and center wavelength and 3-dB bandwidth are 1548 nm and 0.3 nm, respectively.     

中红外光纤技术用于腮腺肿瘤诊断的研究

采用傅里叶变换红外光谱法与中红外光导纤维联用技术对１１例肿瘤，７例正常腮腺和１例舍格伦综合症的红外光谱进行了对比研究。结果发现正常腮腺和舍格伦综合症的红外光谱很相似，而与肿瘤的光谱存在着明显差别，同时也观察到良性与恶性肿瘤的光谱在若干波段处也有所不同．