Amine- and phosphine-free palladium(II)-catalyzed homocoupling reaction of terminal alkynes

An efficient, amine- and phosphine-free palladium(II)-catalyzed homocoupling of terminal alkynes has been developed. In the presence of PdCl₂, CuI, Me₃NO, and NaOAc, homocoupling of various terminal alkynes underwent smoothly to afford the corresponding diynes in moderate to high yields without any phosphine ligands. In contrast, the presence of a phosphine ligand (PPh₃) disfavored this palladium-catalyzed homocoupling procedure. Bases, solvents, and CuI have fundamental influence on the palladium-catalyzed homocoupling of terminal alkynes.     

超临界二氧化碳介质中钯催化炔烃羰基化反应

研究了以超临界二氧化碳为反应介质实现改善钯催化炔烃羰基化反应绿色性的方法 .研究结果表明 :醇的用量、二氧化碳压力和反应温度等因素均对钯催化炔烃羰基化反应的化学选择性均有影响 ,即存在炔烃的羰基化反应与氧化偶合反应的竞争     

Ginkgo biloba extract preserves pyruvate and enhances ascorbate in the cortex of gerbils during focal cerebral ischemia. A microdialysis-liquid chromatography study

The aim of this study was to evaluate dynamic changes in energy-related metabolites in the cortex of gerbils subjected to focal cerebral ischemia after pretreatment with Ginkgo biloba extract. Focal cerebral ischemia was induced by occlusion of the right common carotid artery and the right middle cerebral artery for 60 min in anesthetized gerbils. A microdialysis probe was inserted into the cortex to monitor extracellular lactate. pyruvate and ascorbate during ischemia and reperfusion. The present study demonstrated a dynamic decrease in pyruvate (25% of baseline) and increases in lactate (160% of baseline) and asorbate (300% of baseline) and a 5-fold increase in the lactate:pyruvate (L:P) ratio during cerebral ischemia in the control group. However. pyruvate levels were preserved and ascorbate levels were enhanced with a chronic pretreatment of Ginkgo biloba extract for 8 days (i.p., 100 mg kg(-1) day(-1)). Preservation of pyruvate and enhancement of ascorbate observed in this study may be associated with the neuroprotective effects of Ginkgo biloba extract.     

Synthesis and Photophysical Properties of Hetero‐Bischelated Complexes of Rhodium(III) Containing Phenyl‐Pyridin‐2‐Ylmethylene‐Amine

Three new hetero‐bischelated rhodium (III) complexes of cis‐[Rh(PA)(L)Cl₂]Cl (where PA = phenylpyridin‐2‐ylmethylene‐amine; L = 2,2′‐bipyridine, 2,2′‐dipyridylamine and 1,10‐phenanthroline) have been successfully prepared and characterized. Each complex shows high intensity bands in the UV region, and these are assigned to spin‐allowed π‐π* transitions. The medium‐intensity absorption band profile in the lower energy region can be explained by convolution of spin‐allowed CT and d‐d* transitions. The emission spectra at low temperature (77 K) of these complexes in EtOH/MeOH (4:1 v/v) are virtually identical. They all exhibit a broad, symmetric, and structureless red emission with a microsecond lifetime and hence are assigned as the d‐d* phosphorescence.     

Quality evaluation of fingerprints of herbal medicine with chromatographic data

In this study, local least squares (LLS) and principal component analysis (PCA) were applied to deal with the disturbances in a data set of chromatographic fingerprints after necessary data transformations. It has been demonstrated that PCA with standard normal variate (SNV) transformation of data led to meaningful classification of 33 different Erigeron breviscapus herbal samples. The result was also corroborated by variance squares discriminant method. The quality of herbal objects was further evaluated, and the causes of this fact have been explained from a chemical point of view. At the same time, it implied an idea for qualitative evaluation of the herbal objects with a common class pattern of chromatographic fingerprints.     

Surface modification studies of edge-oriented molybdenum sulfide nanosheets

We have synthesized edge-oriented MoS2 nanosheets by the evaporation of a single source precursor based on Mo(IV)-tetrakis(diethylaminodithiocarbomato). The surface chemistry of the MoS2 nanosheets has been studied in order to evaluate the chemical reactivities of the basal planes and edges. By irradiating the MoS2 nanosheet with a scanning infrared laser, micron-scale lithographical structures can be created due to laser-induced oxidation of MoS2 to form nanocrystalline MoO3. Preferential reactivities of the MoS2 basal edges in an electrochemical environment and during vapor phase deposition have been demonstrated. Functionalization of the basal plane with 1-pyrene acetic acid allows the immobilization of DNA and immunoglobins on the MoS2 basal plane.     

Structure and Magnetic Properties of a Novel Two‐Dimensional Complex from 1, 3, 5‐Benzenetricarboxylate and Neodymium(III) — {[Nd(1, 3, 5‐benzenetricarboxylate)(H2O)4] · H2O}n

A unique neodymium(III) complex, {[Nd(BTC)(H₂O)₄] · H₂O}_n (BTC = 1, 3, 5‐benzenetricarboxylate), was obtained from the reaction between Nd(ClO₄)₃ · xH₂O and Na₃BTC. Coordination bonds, hydrogen bonds, and π‐π stacking form a supramolecular structure with a novel, two‐dimensional framework. The temperature‐dependent magnetic susceptibilities were analyzed by the Curie‐Weiss law; the following values were found C = 1.32, θ = —18.3 K, respectively.     

Alkaloids from stems of Ervatamia yunnanensis

Six indole alkaloids were isolated from the stems of Ervatamia yunnanensis. Among them, yunnanensine (I) is new. The other five are known alkaloids, namely: 19,20-E-vallesamine (II), 19s-heyneanine (HI), ibogaine (IV), ibogamine (V), coronaridine (VI). The structural elucidation of the alkaloids was based on spectral means.     

新型纤维素衍生物手性固定相的制备及其对几种对映异构体的高效液相色谱分离

合成了一种经环十二烷修饰的纤维素酯，将其涂敷于小粒径的氨丙基化硅胶（APS）上，制备出高效液相色谱手性固定相，以正己烷、异丙醇为流动相拆分了2-对氯苯基丙腈、1-对氟苯基乙醇、1-对叔丁基苯氧基-2-丙醇、2-对氯苯基辛腈及三唑醇等5种外消旋对映体，并考察了流动相中异丙醇含量对分离效果的影响。