In-situ synchrotron X-ray absorption studies of LiMn0.25Fe0.75PO4 as a cathode material for lithium ion batteries

Recently, lithium bi-metal phosphates (LiM′M″PO₄) have been synthesized for use as cathode materials in order to increase cell voltages and electrical performances. In this work, we have substituted Mn²⁺ at the 4c site of LiFePO₄ to prepare the lithium bi-metal phosphate LiMn_0.25Fe_0.75PO₄ and have found that it greatly enhances the cell voltage. At a 0.05 C discharge rate, the cell capacity was about 153 mAhg^− 1 and the average working voltage rose to 3.53 V due to the Mn substitution. However, the capacity and working voltage both decrease as the discharge rate increases. By in-situ metal K-edge absorption analysis, it reveals that the substituted metal Mn²⁺ does not work completely at a higher discharge rate, due to poor electrical conductivity and a serious Jahn–Teller effect.     

A Diels-Alder route to angularly functionalized bicyclic structures

A Diels-Alder-based route to trans-fused angularly functionalized bicyclic structures has been developed. This transformation features the use of a tetrasubstituted dienophile in the cycloaddition step.     

An efficient large-scale synthesis of gemcitabine employing a crystalline 2,2-difluoro-α-ribofuranosyl bromide

An efficient large-scale synthesis of gemcitabine was achieved without chromatography or fractional crystallization. The key steps include stereospecific conversion of a novel β-ribofuranosyl phosphate into a highly crystalline α-ribofuranosyl bromide and coupling of the α-ribofuranosyl bromide and trimethylsilyl cytosine to produce a β-nucleoside. p-Phenylbenzoyl group was introduced for the protection of one of hydroxy groups in order to enhance the crystallinity of intermediates. Continuous removal of trimethylsilyl bromide, generated during the coupling reaction, by distillation from the reaction medium substantially enhanced the β-selectivity of the crucial coupling reaction.     

Efficient and library-friendly synthesis of furo- and thieno[2,3-d] pyrimidin-4-amine derivatives by microwave irradiation

A new, divergent, efficient, and selective synthesis of furo- and thieno[2,3-d]pyrimidin-4-amine derivatives by microwave irradiation has been developed starting from readily available amines and substituted 2-aminofuran-3-carbonitrile or 2-aminothiophene-3-carbonitrile, which are converted into corresponding formamidines in DMF using benzenesulfonyl chloride.     

Highly Efficient Oxidative Bromination of Alkanes with the HBr-H2O2 System in the Presence of Catalyst

Various cycloalkanes and straight‐chain alkanes were efficiently brominated with an aqueous HBr‐H₂O₂ system. This oxidative brominating process was promoted by catalysis and irradiation with light. The cycloalkanes were converted to the corresponding bromo‐cycloalkanes in moderate yields and the straight‐chain alkanes produced dominantly secondary bromides. This simple but effective bromination method of alkanes is characterized by high atom efficiency, inexpensive reagents and the absence of organic waste, which make it a good alternative to the existing method for C? H activation through bromination.     

Multi-scales association modeling of membrane water resistance indexes

In order to quantify and predict the water resistance of membrane, a multi-scales association model was built up based on the Fick’s second law. Two water resistance indexes, balance time and seepage velocity, were put forward and calculated by the model for measuring the property of membrane water resistance. The association model linked macro-scale factors and micro-scale parameters together. The influence of macro-scale factors, environmental temperature and membrane thickness, and micro-scale parameters, water molecules diffusivity, membrane saturated water absorption rate and water escape concentration, were discussed. The properties of water resistances for two groups including 10 waterborne acrylate membranes samples were measured for validating the indexes calculated by the model. The well consistency between the results of calculations and experiments proved that the method of multi-scales association modeling for quantifying and predicting the membrane water resistance was feasible.     

A New ent-Kaurane Diterpenoid from Isodon enanderianus

Isodon enanderianus (Hand. -Mazz.) H. W. Li, has been used in folk medicine as anti-inflammatory and detoxified agent1. The Isodon genus is known to be rich in ent-kaurane diterpenoids, a series of new ent-kaurane diterpenoids have been isolated from the dried leaves of I. enanderianus2-4. In order to find more biologically active substances, we have carefully investigated the chemical constituents of I. enanderianus collected in Shiping county of Yunnan province, and as a result, enanderi…