Palladium and Copper Cocatalyzed Intermolecular Cyclization Reaction: Synthesis of 5‐Aminopyrazole Derivatives

A novel and efficient palladium and copper co‐catalyzed intermolecular cyclization of acetonitriles with hydrazones has been developed for the synthesis of 5‐aminopyrazoles through C C and C N bond formation. The reaction has the advantages of easily available starting materials, simple manipulation and mild reaction conditions. The reaction involving various substituted acetonitriles and hydrazones proceeds smoothly and 5‐aminopyrazoles are synthesized in good yields. In contrast to the aliphatic and heteroaromatic substrates, the aromatic substrates tend to have a higher degree of reactivity.

     

Synthesis of [60]Fullerene‐Fused Tetralones via Palladium‐ Catalyzed Ketone‐Directed sp2 C?H Activation and sp3 C?H Functionalization

The palladium‐catalyzed ketone‐directed dual sp² C H activation and sp³ C H functionalization has been applied for fullerene functionalization for the first time. The sec‐alkyl aryl ketones have been exploited to react with [60]fullerene (C₆₀) to provide the novel and scarce C₆₀‐fused tetralones. The combined use of a highly active cationic palladium(II) catalyst and trifluoromethanesulfonic acid is crucial for the improvement of the reaction yield. A plausible reaction mechanism leading to the observed products has been proposed, and the electrochemistry of the fullerene products has also been investigated.

     

Palladium‐Catalyzed Oxidative Carbonylation of Aromatic C−H Bonds with Alcohols using Molybdenum Hexacarbonyl as the Carbon Monoxide Source

With molybdenum hexacarbonyl as the carbon monoxide source, a general palladium‐catalyzed carbonylative transformation of the C−H bond on aromatic rings to produce esters has been developed. Good yields of the corresponding products have been obtained with wide functional group tolerance and excellent regioselectivity. A variety of aliphatic alcohols are suitable reactants here.

     

Enantioselective One‐Pot Reaction: Organocatalyzed Synthesis of Fully Functionalized Oxabicyclo[2.2.2]octanes with Seven Contiguous Stereocenters

An enantioselective one‐pot Michael/Michael/Henry/hemiacetalization reaction between α,β‐unsaturated aldehydes, α‐ketoamides, and nitroalkenes under mild conditions catalyzed by a diarylprolinol silyl ether has been developed. The sequential methodology provides a direct approach to a wide range of fully substituted chiral oxabicyclo[2.2.2]octanes with seven contiguous stereocenters in moderate to excellent yields (up to 99%), high to excellent diastereoselectivities (up to >25:1 dr), and high to excellent enantioselectivities (up to 99% ee).

     

Catalyst-Controlled Selectivity in Oxidation of Olefins: Highly Facile Success to Functionalized Aldehydes and Ketones

Catalysis Letters - The attractive challenge in green chemistry is exploring novel heterogeneous catalyst system for catalyst-controlled product selectivity for oxidation of olefins. Hence, we...     

Influences of internal erosion on infiltration and slope stability

Bulletin of Engineering Geology and the Environment - Rainfall-induced slope failures in natural terrains are destructive natural disasters. Transport of fine particles may be induced by the...     

Fabrication of shish-kebab-structured carbon nanotube/poly(ε-caprolactone) composite nanofibers for potential tissue engineering applications

The electrospinning process was applied to fabricate the nanofibers of biodegradable poly(ε-caprolactone)(PCL) in which different contents of multiwalled carbon nanotubes(MWCNTs) were embedded. Afterward,the electrospun nanofibers were successfully decorated with shish-kebab structure via a self-induced crystallization technique. The topographical features and the mechanical properties of the composite scaffolds were characterized,and the biocompatibility of the material was assessed by using human osteogenic sarcoma osteoblasts(MG-63 cells). The carbon nanotube(CNT) concentration is found to affect the fiber diameter and mechanical properties of electrospun nanofibers and the periodic distance of the shish-kebab architecture. Cellular attachment and proliferation assays reveal that 0.5 wt% CNT-embedded PCL scaffold shows enhanced biocompatibility with MG-63 cells than their counterparts made of neat PCL, and the collagen-like nanotopology provided by the shish-kebab structure further facilitates the cell adhesion and proliferation. The superior interactions between cells and scaffolds demonstrate that the shish-kebab-structured CNTs/PCL nanofibers may be promising candidate for tissue engineering scaffold application.     

新形势、新条件下金工实习教学改革

本文讲述了新形势、新条件下金工实习的性质、目的和教学的基本要求。分析了职教金工实习的教学现状。并从金工实习的顺序、教学模式、教学计划、教学内容等多方面讲述了如何适应新的人才培养方案,改革金工实习教学模式。如何加强教学管理,提高实习效果。最后讲述了改革金工实习教学管理模式,提高师资队伍人员素质的方法。     

Powder Size Influence on Tensile Properties and Porosity for PM Ti_2AlNb Alloy Prepared by Hot Isostatic Pressing

Pre-alloyed powder of Ti_2AlNb alloy was prepared by electrode induction gas atomization method, and the powder was screened into fi ve kinds of powder size distribution. Fully dense Ti_2AlNb alloy was prepared by powder metallurgy(PM) using hot isostatic pressing. The properties of pre-alloyed powder and PM Ti_2AlNb alloy were tested. Results show that mean grain size of PM Ti_2AlNb alloy is infl uenced by powder particle size, but particle size has no signifi cant infl uence on tensile properties. Finer Ti_2AlNb powder has low Argon gas bubble ratio and high oxygen content, and poor fl owability of fi ner powder increases the degree of diffculty during degassing. As a result, big pores( 50 μm) are observed in PM Ti_2AlNb alloy prepared by fi ner powder and cause plasticity loss of tensile properties. In order to get a better comprehensive properties of PM Ti_2AlNb alloy, powder with an average size(～ 100 μm) is suggested.