Lewis acid mediated reactions of cyclopropyl aryl ketones with alpha-ketoesters: facile preparation of 5,6-dihydropyran-2-ones

[reaction: see text] A new general method for the synthesis of 5,6-dihydropyran-2-ones from cyclopropyl aryl ketones (monoactivated cyclopropanes) and alpha-ketoesters in good to excellent yields has been developed. The process involves a cascade of reactions, including a nucleophilic ring-opening reaction of monoactivated cyclopropane by H2O, Lewis acid mediated transesterification, and an aldol type reaction.     

金属羰基化合物的结构对氧原子转移反应速率的影响

本文研究了氧化三甲胺Ｍｅ３ＮＯ与羰基簇合物Ｍ４（ＣＯ）１２－ｎＬｎ（Ｍ＝Ｃｏ，Ｉｒ；ｎ＝１，２；Ｌ＝磷配体）的氧转移反应动力学，讨论了反应机理。反应符合二级速率方程：ｒ＝Ｋ２［Ｍｅ３ＮＯ］［Ｍ４（ＣＯ）１２－ｎＬｎ］Ｍ４（ＣＯ）１２－ｎＬｎ的氧转移反应活性呈现如下顺序：中心元素不同时Ｃｏ４（ＣＯ）１２－ｎＬｎ＜Ｉｒ４（ＣＯ）１２－ｎＬｎ；取代配体不同时Ｍ４（ＣＯ）１２－ｎ（Ｐ（ＯＭｅ）３）ｎ＞Ｍ４     

Pressurized hot water extraction of berberine, baicalein and glycyrrhizin in medicinal plants

Pressurized hot water extraction (PHWE) using a laboratory made system was applied for the extraction of thermally labile and reasonably polar components such as berberine in coptidis rhizoma, glycyrrhizin in radix glycyrrhizae/liquorice and baicalein in scutellariae radix. PHWE was carried out dynamically at a flow of 1 ml/min, temperature between 95 and 140 °C, an applied pressure of 10-20 bar and extraction time of 40 min. Extraction by PHWE was found to give efficiencies comparable to Soxhlet extraction for baicalein in scutellariae radix and sonication for berberine in coptidis rhizoma, and glycyrrhizin in radix glycyrrhizae. Effects of ethanol added into the water used in PHWE were explored. Pressurized liquid extraction (PLE) with methanol as solvent was used for extraction of baicalein in scutellariae radix. The marker compounds present in the various medicinal plant extracts were determined by gradient elution HPLC.     

DMF-甲醇体系粘度与核磁共振化学位移的同时关联

提出了一个基于局部组成概念上的核磁共振模型. 利用该模型和以前别人提出的局部组成型粘度方程, 成功地同时关联属于传递性质的粘度数据和属于波谱性质的核磁共振化学位移数据，关联所得到化学位移的平均绝对偏差小于0.0072，粘度的平均绝对偏差小于0.0006 mPa•s，结果表明提出的局部组成模型是合理的.     

Syntheses and characterizations of three-dimensional channel-like polymeric lanthanide complexes constructed by 1,2,4,5-benzenetetracarboxylic acid

The hydrothermal reaction of YbCl(3) small middle dot6H(2)O with 1,2,4,5-benzenetetracarboxylic dianhydride resulted in [[Yb((b)btec)(1/4)((d)btec)(3/6)(H(2)O)(2)](4).6H(2)O](n)() (1) (H(4)btec = 1,2,4,5-benzenetetracarboxylic acid), and the solvothermal reaction of Er(NO(3))(3) small middle dot6H(2)O or TbCl(3).6H(2)O with 1,2,4,5-benzenetetracarboxylic dianhydride in H(2)O/acetic acid gave rise to [[Er(2)((c)btec)(2/4)((e)btec)(2/4)((f)btec)(2/4)(H(2)O)(4)].4H(2)O](n)() (2) and [[Tb(H(2)btec)(2/4)((f)btec)(3/6)(H(2)O)].2H(2)O](n)() (3), respectively. Complex 1 crystallizes in monoclinic space group C2/m with a = 20.8119(5) A, b = 17.6174(1) A, c = 5.7252(2) A, beta = 92.324(1) degrees, and Z = 1. 1 possesses a three-dimensional framework consisting of eight-coordinate ytterbium centers and two kinds of channels along the c axis. Complex 2 crystallizes in triclinic space group P with a = 9.6739(5) A, b = 11.0039(5) A, c = 11.5523 A, alpha = 104.8330(10) degrees, beta = 91.0000(10) degrees, gamma = 114.2570(10) degrees, and Z = 2. 2 has a three-dimensional framework comprising both eight- and nine-coordinate erbium centers and channels along the a axis. Complex 3 crystallizes in monoclinic space group P2(1)/n with a = 10.7246(12) A, b = 7.1693(9) A, c = 17.158(2) A, beta = 97.109(2) degrees, and Z = 4. 3 shows a three-dimensional framework containing nine-coordinate terbium centers and channels along the b axis. Uncoordinated water molecules occupy the channels in the three complexes. TGA and XRPD were determined for the three complexes, and the results illustrate that the framework of 1 is retained upon removal of uncoordinated and coordinated water molecules.     

Ab initio MO-SCF calculation on a model of anomalous water

Ab initio calculations are carried out on the planar hexamer model of anomalous water using a variety of basis sets. The results are compared to results of similar calculations on free water and water in the ice I-like puckered ring configurations.

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Zusammenfassung Es werden ab initio-Rechnungen für das planare Hexamer-Modell von anomalem Wasser unter Verwendung mehrerer BasissÄtze durchgeführt. Die Ergebnisse werden mit Resultaten Ähnlicher Rechnungen über freies Wasser und Wasser in der I-Eis Ähnlichen Konfiguration verzerrter Ringe verglichen.

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Résumé Calculs ab initio sur le modèle hexamérique plan de l'eau anormale en utilisant différentes bases. Les résultats sont comparés à ceux de calculs similaires sur l'eau libre et sur l'eau dans une configuration cyclique compacte analogue à celle de la glace I.

     

Interaction of dextran sulfates with positively and negatively charged silver bromide hydrosols

Summary The effects of dextran sulfates of different molecular weights and charge densities on the stability of positively and negatively charged silver bromide solsin statu nascendi have been studied by means of light scattering.The plots of scattering intensities of a positively charged sol against the concentration of the added dextran sulfates show one pronounced maximum, the position which is independent on the molecular weight of the polyelectrolyte used. The maximum shifts to lower polyion concentrations with dilution of the sol.The effect of polyanions on the stability of silver bromide sols of the same sign of charge were investigated as a function of molecular weight of the polymers, the sol concentration, the charge and the concentration of counterions, and the addition of methanol. Destabilization only occurred if sufficient amount of indifferent electrolyte was present in the system. However, the concentration of counterions necessary to produce a flocculation maximum was lower in the presence of the polyelectrolytes than in their absence. The results obtained were compared with the data on sols containing nonionic dextrans reported earlier.

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Zusammenfassung Der Einfluß der Dextransulfate von verschiedenen Molekulargewichten und Ladungsdichten auf die Stabilität der positiv und negativ geladenen Silberbromid-Solein statu nascendi wurden durch Lichtstreuung untersucht. Wenn die Intensitäten der Lichtstreuung eines positiv geladenen Silberbromid-Sols gegen die Konzentration der zugesetzten DextranSulfate aufgetragen werden, tritt ein ausgeprägtes Maximum auf, dessen Lage von dem Molekulargewicht des angewandten Polyelektrolyten unabhängig ist. Bei Verdünnung des Sols wird das Maximum zur niedrigeren Konzentration des Polyanions verschoben.Der Einfluß der Polyanionen auf die Stabilität der Silberbromid-Sole mit gleichem Ladungsvorzeichen wurde in Abhängigkeit von dem Molekulargewicht des zugesetzten Dextransulfats, der Solkonzentration, der Ladung und Konzentration der Gegenionen und dem Zusatz von Methylalkohol untersucht. Destabilisierung wird nur in Anwesenheit einer genügenden Menge von Neutralelektrolyten in den untersuchten Systemen beobachtet. Die Konzentration der Gegenionen, die ein Flockungsmaximum verursachen, ist immer niedriger als die kritische Koagulationsmenge derselben Ionen für das gleiche Sol in Abwesenheit von Makroionen. Die Resultate wurden mit den Wechselwirkungen der Silberbromid-Sole mit nichtionogenen Dextranen verglichen, und der Mechanismus der Flockung durch Polyelektrolyte wurde diskutiert.

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5 figures and 1 table

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Supported by the NSF Grant GP 42331 X.

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A part of the Ph.D. Thesis by David Lindsay.     

Highly efficient rhodium/monodentate phosphoramidite catalyst and its application in the enantioselective hydrogenation of enamides and alpha-dehydroamino acid derivatives

An easily prepared and highly efficient monodentate phosphoramidite ligand derived from BINOL, (S)-2,2'-O,O-(1,1'-binaphthyl)-dioxo-N,N-diethylphospholidine, was examined in the hydrogenation of both enamides and alpha-dehydroamino acid derivatives. The catalyst provided remarkably high enantioselectivities (up to 99.6% ee for enamides and >99.9% ee for alpha-dehydroamino acid derivatives).     

Synthesis,photophysical and electrochemical studies of di-2-pyridyl ketone complexes of rhodium(III)

Complexes of rhodium(III) with di-2-pyridyl ketone (dpk), Rh(dpk)(MeCN)Cl₃ (1) and cis-[Rh(dpk)₂Cl₂]⁺ (2), have been successfully prepared and characterized. At low temperature (77 K), complex (2) in EtOH/MeOH (4:1, v/v) shows a broad, symmetric and structureless red emission with a microsecond lifetime and, hence, is assigned as the dd* phosphorescence. Electrochemical data, including cyclic voltammetry, normal pulse voltammetry, triple pulse voltammetry and controlled potential electrolysis, have been obtained for the two dpk complexes of rhodium(III) in MeCN. On the basis of analysis of the electrochemical (1,2) and luminescence data (2), electron transfer mechanisms are proposed. For complex (1), two reduction processes occur at the metal-localized orbitals with elimination of chlorides during the first reduction step. This is followed by a one-electron reduction at the metal. For complex (2), three electrons are transferred to the metal in two successive reduction steps accompanied by elimination of two chlorides. After these two reduction steps another one-electron reduction occurs at the dpk ligand.