Copper‐Catalyzed Three‐Component Azidotrifluoromethylation/Difunctionalization of Alkenes

A novel three‐component strategy for the azidotrifluoromethylation of alkenes has been presented here. The reaction proceeded smoothly under gentle temperature and gave the bifunctional olefins in high yields. Furthermore, 1,3‐dipolar reactions between azide‐containing products and phenylacetylene revealed great potential in molecular modification by using this method.     

Cycloaddition reactions of benzyne with olefins

Some novel cycloaddition reactions based on benzyne and olefins have been developed.These reactions were performed in the absence of a transition metal catalyst,and they displayed good yields.These cycloaddition reactions of benzyne with olefins provide effective routes for synthesizing benzocyclobutenes,biaryl compounds and 9,10-dihydrophenanthrene derivatives.     

Synthesis of binuclear palladium complexes with a rigid phenylene bridge linker

The complexes [PdX₂Py]₂(di-NHC) (X = Br or Cl) in which di-NHC represents a di-N-heterocyclic carbene, featuring a rigid phenylene spacer between the carbene units, have been prepared from reactions of the corresponding diimidazolium halide salts with PdCl₂ in pyridine. The molecular structures of three of the complexes were determined by X-ray diffraction studies. The influences of different substitutions and of the halide ligand (Br or Cl) on the structure and reactivity of the complexes have been studied. The catalytic activity of the binuclear palladium complexes was tested in the Mizoroki–Heck reaction of styrene with bromobenzene.     

Synthesis of macrocyclic polystyrene-polydimethylsiloxane block copolymers

A series of macrocyclic polystyrene (PS)-polydimethylsiloxane (PDMS) block copolymers and similar block copolymers was synthesized by sequential polymerization of styrene and hexamethyl cyclotrisiloxane (D₃) initiated by a difunctional anionic initiator in THF at −78° followed by coupling with Cl₂SiMe₂ in very dilute (10⁻⁵ – 10⁻⁶ M) solutions. Total molecular weights ranged from about 2–85 × 10³. The formation of monodisperse macrocyclic block copolymers was indicated by the lower (15–30%) hydrodynamic volume of the rings compared to that of the linear block copolymers. Carbon-13 and ²⁹Si NMR likewise supported the absence of linear polymer in the macrocyclic block copolymer. The behavior of second virial coefficient A₂ of the rings and the linears versus temperature was examined by static light scattering in cyclohexane. Below 20° the A₂ for the linear polymer goes negative while that for the cycle remains positive. Dynamic light scattering (DLS) as a function of temperature also reflects that the cyclic polymers remain well solvated even down to 12°C. The DLS autocorrelation functions for the linear triblock however demonstrate the onset of aggregation and phase separation as the temperature is reduced below 20°C.     

Trace gas detect based on spectral analysis and harmonic ratio

Optical Review - A novel method of gas concentration calibration for tunable diode laser absorption spectroscopy, in which spectral analysis and harmonic signal intensity ratio measurement are...     

Mechanistic Studies on Propargyl Alcohol-Tethered Alkylidenecyclopropane with Aryldiazonium Salt Initiated by Visible Light

This paper discloses the reaction mechanism of two consecutive but different visible light photo-induced chain processes for the rapid construction of spirobi[indene]skeletons.The first process is triggered by a photo-induced single-electron-transfer(SET)of an electron donor-accepter(EDA)complex.The second process is initiated by a direct SET process between aryldiazonium salt and the excited allenic intermediate.In these two processes,another SET took place respectively on the in situ formed radical intermediate to realize a redox-neutral outcome.The mechanistic studies have been carried out by control experiments,kinetic and spectroscopic analyses,deuterium labeling experiments to support these two chain processes.     

动态压缩下Zr基非晶合金失效释能机理

为研究Zr 基非晶合金动态压缩条件下的失效释能机理,采用力学试验机、霍普金森杆、高速摄影、差示扫描量热分析(differential scanning calorimetry, DSC)、扫描电镜(scanning electron microscope, SEM)等,得到了材料应力应变曲线、高速摄影图像、失效式样微观形貌及DSC 曲线,根据实验数据计算了材料的晶化激活能,并拟合了材料的JH-2(Johnson-Holmquist Ⅱ)模型,对材料动态失效过程进行有限元数值模拟。实验结果表明,压缩条件下材料为脆性断裂,断口处观察到典型的脉状纹样及液滴状结构,材料失效过程伴随着释能现象;数值模拟结果表明,材料裂纹局部的瞬时内能大于材料晶化激活能。动态压缩下材料的失效释能机理即为材料破碎释放储存的弹性势能,并导致材料局部晶化释能,释能强度与应变率成正相关。     

IVSPlat 1.0: an integrated virtual screening platform with a molecular graphical interface

Background  

The virtual screening (VS) of lead compounds using molecular docking and pharmacophore detection is now an important tool in drug discovery. VS tasks typically require a combination of several software tools and a molecular graphics system. Thus, the integration of all the requisite tools in a single operating environment could reduce the complexity of running VS experiments. However, only a few freely available integrated software platforms have been developed.     

Construction of aromatic [5,5] spiroketals via hypoiodite-catalyzed etherification combined in relay cascades

An approach is developed for the synthesis of bisbenzannelated spiro[5,5]ketals via a catalytic relay reaction cascade involving a new cyclo-etherification, which is prompted by fluoride and catalyzed by the hypoiodite species generated in situ from irradiative aerobic oxidation of an iodide ion formed in the former step of the reaction cascade.     

3D-structured carbon-coated MnO/graphene nanocomposites with exceptional electrochemical performance for Li-ion battery anodes

MnO has a high theoretical capacity, moderate discharge plateau, and low polarization when it is used as the anode material in lithium battery. However, the issues that limit its application are its poor conductivity and large volume changes, which can easily result in the collapse of electrode structure during long-term cycling. In the present work, a carbon-coated MnO/graphene 3D-network anode material is synthesized by an electrostatic adsorption of dispersed precipitates precipitation method. The MnO nanoparticles coated by carbon are uniformly distributed on the surface of graphene nanosheets and form a 3D sandwich-like nanostructure. A carbon layer is coated on the surface of MnO nanoparticles, which slows down the volume expansion in the process of lithium intercalation. The graphene nanosheets are cross-linked through carbons in this 3D nanostructure, which provides mechanical support and effective electron conduction pathways during the charge-discharge. The electrochemical tests indicate that the prepared 3D carbon-coated MnO/graphene electrode exhibits an excellent rate capacity of 1247.3 and 713.2 mAh g^?1 at 100 and 1000 mA g^?1, respectively. The capacity is 792.2 mAh g^?1 after long cycle at a current density of 1000 mA g^?1. The specific capacity is higher than that of MnO-based composite lithium anode materials currently reported. The superior rate and cycling performances are attributed to the unique 3D-network structure, which provides an effectively conductive network, buffers volume expansion, and prevents falling and aggregation of MnO in the charge and discharge process of the electrode materials. The 3D-structured carbon-coated MnO/graphene anode material will have an excellent application prospect.

Open image in new window

Graphical abstract Cyclic performance at 1 A g^?1 and SEM images (inset) of the 3D-structured carbon-coated MnO/graphene nanocomposite.