An unprecedented highly efficient solvent-free oxidation of alkynes to α,β-acetylenic ketones with tert-butyl hydroperoxide catalyzed by water-soluble copper complex

The catalytic system composed of CuCl₂ and 2,2′-biquinoline-4,4′-dicarboxylic acid dipotassium salt (BQC) was found to be highly efficient for the selective α-oxidation of internal alkynes to the corresponding α,β-acetylenic ketones, with aqueous tert-butyl hydroperoxide under mild conditions. For the first time, full conversions of alkynes were reached with excellent selectivities, and propargylic tert-butylperoxy ethers were observed and suggested as the reaction intermediates. In the case of terminal alkynes, the oxidations are sluggish and low yields ranging from 32% to 40% were obtained.     

Enantioselective separation in capillary electrophoresis using a novel mono-6-propylammonium-β-cyclodextrin as chiral selector

The chiral resolving ability of a novel single-isomer cationic β-cyclodextrin (CD), mono-6^A-propylammonium-6^A-deoxy-β-cyclodextrin chloride (PrAMCD), as a chiral selector in capillary electrophoresis (CE) is reported in this work for the enantioseparation of hydroxy, carboxylic acids and amphoteric analytes. The effect of chiral selector concentration on the resolution was studied. Good resolutions were achieved for hydroxy acids. Optimum resolutions were obtained even at 3.5 mM CD concentration for carboxylic acids. The electrophoretic method showed good linearity and reproducibility in terms of migration times and peak areas, which should make it suitable for routine analysis. In addition, baseline chiral separation of a six-acid mixture was achieved within 20 min. PrAMCD proved to be an effective chiral selector for acidic analytes.     

First iodocyclization of β-allenic phosphonates: a novel synthesis of α-difluoromethylenephostones

Six-membered α-difluoromethylenephostones were prepared in moderate to good yields with high regioselectivities under mild conditions from the iodocyclization reaction of diethyl β-allenic α,α-difluorophosphonates using I₂ or ICl as the electrophile.     

Preparation of enantiomerically pure (E)-β-sulfinylenones from β-ketoesters

Enantiomerically pure (E)-β-sulfinylenones are smoothly prepared from β-ketoesters in three steps with good overall yield. Since they can be the substrates of many diastereoselective reactions, they represent versatile precursors of a wide range of chiral building blocks. We propose a rationale to explain the formation of (E)-β-sulfinylenones from the corresponding δ-enol-methylethers.     

手性β-氨基醇的合成及其催化二乙基锌与醛的不对称加成反应

以烯烃为原料通过Sharpless不对称双羟化等多步反应合成7种手性β-氨基醇, 并将该类化合物用于催化二乙基锌和醛的不对称加成反应. 分别考察了影响对映选择性的催化剂结构、催化剂用量、溶剂、反应温度等各种因素. 当催化剂用量为5%、甲苯溶剂、在－10 ℃下、以(1S,2R)-(＋)-2-氨基-1,2-二苯基乙醇(1b)作催化剂时, 所得仲醇的对映体过量最高为85% ee, 产率高达100%.     

Neutron powder diffraction study of A2BeF4 (A=K, Rb, Cs): Structure refinement and analysis of background

The crystal structure of potassium, rubidium and caesium fluoroberyllates have been re-examined by neutron powder diffraction at room temperature and at 1.5 K. Previously, their structures, obtained from X-ray data, were described in the Pn2₁a space group. However, the results obtained from Rietveld refinements, using powder neutron diffraction, at both temperatures, indicated that all structures are orthorhombic with space group Pnma. The known phase transition at high temperature is probably related to the appearance of a hexagonal pseudo-symmetry instead of the elimination of the mirror plane between the above mentioned orthorhombic space groups. A possible phase transition, at very low temperature, was discarded considering the stereochemical criteria concerning the structural stability of A₂BX₄ compounds. This was confirmed by thermal analysis. On the other hand, a modulated background has been detected in all samples during the refinements. This is compatible with the presence of an amorphous phase, coexisting with the crystalline phase, or with a disordered component within the main crystalline phase. Instead of using a polynomial function, the background was modelled by Fourier filtering improving the fit for all patterns. The radial distribution function (RDF) was obtained from the analysis of the calculated background and compared with the RDF from the average crystal structure. The advantages of neutron with respect to X-ray diffraction were evidenced for this type of compound with β-K₂SO₄-type structure.     

Chemoselective and stereoselective synthesis of gem-difluoro-β-aminoesters or gem-difluoro-β-lactams from ethylbromodifluoroacetate and imines during Reformatsky reaction

The chemoselective and stereoselective synthesis of gem-difluoro-β-aminoesters or gem-difluoro-β-lactams was investigated from ethylbromodifluoroacetate and imines during Reformatsky reaction. Influence of various reaction parameters, such as nature of the amine part, nature of the chiral auxiliary, was evaluated. High levels of stereoselectivity (up to 98%) were obtained for gem-difluoro-β-aminoesters and gem-difluoro-β-lactams using either (R)-phenylglycinol or (R)-methoxyphenylglycinol.     

A stereoselective synthesis of (2R,3S)-2-amino-3,4-dihydroxybutyric acid using an ether directed aza-Claisen rearrangement

A new approach for the stereoselective synthesis of (2R,3S)-2-amino-3,4-dihydroxybutyric acid, an α-amino acid from Lyophyllum ulmarium, has been accomplished using an ether directed aza-Claisen rearrangement. On investigation of optimal conditions for this key step it was shown for the first time that Au(I) can be used to catalyse this transformation.     

β-D-核糖（ RI）与一价、二价金属离子相互作用的理论研究

在HF和MP2水平用全电子(AE)和相对论有效芯势(RECP)方法研究了Ⅰa、Ⅰb、Ⅱa和Ⅱb族金属离子与β D 核糖(RI)的相互作用. 结果表明, RECP能可靠地用于重金属离子;二价金属离子(M2＋)比一价金属离子(M＋)更易使β D 核糖(RI)变形;二价金属离子络合物(RI M2＋)比一价金属离子络合物(RI M＋)稳定. 电荷布居分析的结果支持上述结论.     

β-胺基丙烯酸酯衍生物的不对称催化氢化反应研究进展

综述了近年来β-胺基丙烯酸酯衍生物的不对称催化氢化反应的研究工作, 并讨论了影响氢化反应活性与对映选择性的各种因素.