Catalytic, asymmetric, "interrupted" Feist-Bénary reactions

Pyrimidine derivatives of the cinchona alkaloids function as excellent asymmetric catalysts for the "Interrupted" Feist-Bénary Reaction. This reaction produces highly substituted hydroxydihydrofurans from simple starting materials under mild conditions. The asymmetric reaction gives high enantioselectivities with unsubstituted bromoketones, and high enantio- and diastereoselectivities with substituted substrates. Mechanistic experiments suggest that the hydrobromide salt of the alkaloid derivative is the active catalyst for the reaction.     

更新"医用化学"的教学理念,努力提高教学质量

在“医用化学”教学中，更新教学理念，灵活运用多种教学手段，强化学生对课程重要性的认识，调动学生的主动性、积极性，启发诱导他们从常识入手去理解复杂问题，归纳总结获取重要结论，可以使课堂教学变得生动有趣，确保提高了教学质量。     

以"人才培养"为中心,全面推进一流专业建设

专业是本科教育的"四梁八柱"。专业建设是一项系统工程,涉及教师、学生以及进行教育教学活动的条件和保障等多方面内容,专业建设的水平和质量直接影响人才培养的质量。本文以湖南大学化学专业为例,分析了专业建设的现状,指明了限制专业发展的问题,同时立足"人才培养"这一中心任务,针对专业建设的短板和不足,从专业建设的软硬件方面提出了改革举措,为一流专业建设提供了借鉴和思路。     

Sterically congested, "roofed" β-iminodisulfides as new chiral ligands for palladium-catalyzed, asymmetric allylic alkylation

The preparation of a new class of "roofed" β-iminodisulfides from sterically congested, conformationally rigid chiral 2-thiazolidinones is described. A functional survey of palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate proved that symmetrical "roofed" β-iminodisulfides are efficient chiral ligands, showing enantioselectivity opposite that associated with chiral "roofed" β-iminothioether ligands.     

"继承唐敖庆先生遗志,展现当代中国化学风采"征文

我国著名的理论化学家、教育家和世界知名的量子化学家,中国科学院资深院士(原学部委员),原国家自然科学基金委员会主任(1986~1990年)、名誉主任(1991~2008年),原吉林大学副校长、校长(1956~1986年)、名誉校长(1986~2008年),《高等学校化学学报》和《Chemical Research in Chin     

Are N-heterocyclic carbenes "better" ligands than phosphines in main group chemistry? A theoretical case study of ligand-stabilized E2 molecules, L-E-E-L (L = NHC, phosphine; E = C, Si, Ge, Sn, Pb, N, P, As, Sb, Bi)

A theoretical examination of the L-E-E-L class of molecules has been carried out (E = group 14, group 15 element; L = N-heterocyclic carbene, phosphine), for which Si, Ge, P, and As-NHC complexes have recently been synthesized. The focus of this study is to predict whether it is possible to stabilize the elusive E(2) molecule via formation of L-E-E-L beyond the few known examples, and if the ligand set for this class of compounds can be extended from the NHC to the phosphine class of ligands. It is predicted that thermodynamically stable L-E-E-L complexes are possible for all group 14 and 15 elements, with the exception of nitrogen. The unknown ligand-stabilized Sn(2) and Pb(2) complexes may be considered attractive synthetic targets. In all cases the NHC complexes are more stable than the phosphines, however several of the phosphine derivatives may be isolable. The root of the extra stability conferred by the NHC ligands over the phosphines is determined to be a combination of the NHCs greater donating ability, and for the group 15 complexes, superior π acceptor capability from the E-E core. This later factor is the opposite as to what is normally observed in transition metal chemistry when comparing NHC and phosphine ligands, and may be an important consideration in the ongoing "renaissance" of low-valent main group compounds supported by ligands.     

Total Synthesis of Several 3, 3"-Biflavones

BiflavonesareamorecomPlicatedclass0fflavonoids.MostofthemareusefulcomPonentsoftraditionalmedicinetocurediseases.Sincechamaejasminel,anewtoeofbiflavonoidpossessingaC-3/C-3"linkage,wasisolatedfromSteUerachamaejasmaeL.byHuangetal',especiallyafterthebiologicalactivityofani-cancerwasdiscovered',thestUdyof3,3"-biflavonoidshasattfactCdmuchattention.3-5ButtherehasbeennoprogressmentionedonthesynthesisofthiskindofcomPoundsinrecentdecades.AsaresultofoursystematicresearchonthesynthesisofchamaejasInin…     

A NEW CHILOTHERE SKULL FROM HEZHENG,GANSU, CHINA——WITH SPECIAL REFERENCE TO THE CHINESE "DICERATHERIUM"

In this paper a new chilothere species, Acerorhinus hezhengensis represented by associated skull andlower jaw from Late Miocene deposits of Hezheng, Gansu, is described. The Chinese "Diceratherium"problem is reviewed and analysed. Systematically, the Chinese "Diccratherium" has scarcely any direct rela-tion with the true Diceratherium of North America. Heissig's referral of the Chinese "Diceratherium" toChilotherium as a subgenus is here disputed. A series of distinctive characters warrant the Chinese "Di-ceratherium" a generic rank, for which Acerorhinus created by Kretzoi in 1942 is adopted. Acerorhinusshares common apomorphic features exclusively with Chilotherium. They may represent a separate tribein the subfamily Acerotheriinae: Chilotherini.     

γ-Alumina: The Essential and Unexpected Role of Water for the Structure, Stability, and Reactivity of "Defect" Sites

Combining experiments and DFT calculations, we show that tricoordinate Al(III) Lewis acid sites, which are present as metastable species exclusively on the major (110) termination of γ- and δ-Al(2)O(3) particles, correspond to the "defect" sites, which are held responsible for the unique properties of "activated" (thermally pretreated) alumina. These "defects" are, in fact, largely responsible for the adsorption of N(2) and the splitting of CH(4) and H(2). In contrast, five-coordinate Al surface sites of the minor (100) termination cannot account for the observed reactivity. The Al(III) sites, which are formed upon partial dehydroxylation of the surface (the optimal pretreatment temperature being 700 °C for all probes), can coordinate N(2) selectively. In combination with specific O atoms, they form extremely reactive Al,O Lewis acid-base pairs that trigger the low-temperature heterolytic splitting of CH(4) and H(2) to yield Al-CH(3) and Al-H species, respectively. H(2) is found overall more reactive than CH(4) because of its higher acidity, hence it also reacts on four-coordinate sites of the (110) termination. Water has the dual role of stabilizing the (110) termination and modifying (often increasing) both the Lewis acidity of the aluminum and the basicity of nearby oxygens, hence the high reactivity of partially dehyxdroxylated alumina surfaces. In addition, we demonstrate that the presence of water enhances the acidity of certain four-coordinate Al atoms, which leads to strong coordination of the CO molecule with a spectroscopic signature similar to that on Al(III) sites, thus showing the limits of this widely used probe for the acidity of oxides. Overall, the dual role of water translates into optimal water coverage, and this probably explains why in many catalyst preparations, optimal pretreatment temperatures are typically observed in the "activation" step of alumina.     

Synthesis of novel O,O"-dialkyl α-aminoalkylphosphonothioates

O,O"-Dialkyl -amino(cyclohexyl)phosphonothioates were synthesized by the reactions of O,O"-dialkyl phosphonothioites with [2-(N-cyclohexylideneamino)ethyl] vinyl ether.     

Colloidal interactions: contact limiting laws,double-layer dissociation,and "non-DLVO" (Derjaguin–Landau–Verwey–Overbeek) forces

The conceptual basis and main results of a new model of the dissociative electrical double layer augmented with Lubetkin-Middleton-Ottewill (LMO) dissociative law are summarized. The main results are: the derivation of fundamental limiting laws of planar repulsions in the limit of surface contact, and their transition to the Debye-Hückel limiting laws at infinite separation; the prediction of stronger and longer-range electrostatic forces, quantitatively and consistently accounting for repulsions in colloidal montmorillonites; the discovery of the classical Debye-Hückel interionic effect being operative in increasing double-layer dissociation by lowering the activities of diffuse ions via the LMO law; the prediction of maxima of Stern potentials in spherical symmetry without any further assumptions, and the prediction of no maxima for platelike montmorillonites. In the light of these new insights, the concepts of "hydration forces" and other close-range "non-DLVO" forces may need to be revised, as well as the origin of the maxima of electrophoretic mobilities (Stern potentials) for spherical colloids.     

润物无声,启迪创新——从"冷冻聚合制备高分子量聚合物"综合实验谈起

冷冻聚合是一种新发展的聚合反应实施方法,其聚合温度低于反应介质的凝固点,聚合场所为冻结聚合体系中的液相微区,液相微区的体积百分数约为10％.因为聚合温度低、液相微区的单体浓度很高,所以冷冻聚合是制备高/超高分子量聚合物的有效方法.本实验分别实施丙烯酰胺和丙烯酸的冷冻聚合,通过改变冷冻聚合条件调控聚合物的分子量,使用稀溶液黏度法测定所得聚合物的分子量.通过该实验,帮助学生理解自由基聚合分子量控制的基本原理,学会灵活运用Mayo方程,引导学生关注实验细节、掌握实验技巧、学会实验设计.     

"一锅法"合成N-链烯基-(2R,3R)-O,O-二乙酰酒石酰亚胺

本文报导一种由(2R,3R)-二乙酰酒石酸酐合成N-ω-链烯基二乙酰酒石酰亚胺的简单有效的"一锅合成法", 并使总产率有大幅度的提高。     

尿酸和叶酸存在下改性碳纳米管糊电极上多巴胺电催化氧化MohammadMazloum-Ardakani,MahboobeAbolhasani,Bibi-FatemehMirjalili,MohammadAliSheikh-Mohseni,AfsanehDehghani-Firouzabadi,AlirezaKhoshroo简

A chemically modified carbon paste electrode (CPE), consisting of 2,2''-[(1E)-(1,2-phenylenebis(azanylylidene)] bis(methanylylidene)]bis(benzene-1,4-diol) (PBD) and multiwalled carbon nanotubes (CNTs), was used to study the electrocatalytic oxidation of dopamine using cyclic voltammetry, chronoamperometry, and differential pulse voltammetry (DPV). First, the electrochemical behavior of the modified electrode was investigated in buffer solution. Then the diffusion coefficient, electrocatalytic rate constant, and electron-transfer coefficient for dopamine oxidation at the surface of the PBD-modified CNT paste electrode were determined using electrochemical approaches. It was found that under optimum conditions (pH = 7.0), the oxidation of dopamine at the surface of such an electrode occurred at about 200 mV, lower than that of an unmodified CPE. DPV of dopamine at the modified electrode exhibited two linear dynamic ranges, with a detection limit of 1.0 μmol/L. Finally, DPV was used successfully for the simultaneous determination of dopamine, uric acid, and folic acid at the modified electrode, and detection limits of 1.0, 1.2, and 2.7 μmol/L were obtained for dopamine, uric acid, and folic acid, respectively. This method was also used for the determination of dopamine in a pharmaceutical preparation using the standard addition method.