Cross- and Multi-Coupling Reactions Using Monofluoroalkanes

Carbon-fluorine bonds are stable and have demonstrated sluggishness against various chemical manipulations. However, selective transformations of C−F bonds can be achieved by developing appropriate conditions as useful synthetic methods in organic chemistry. This review focuses on C−C bond formation at monofluorinated sp³-hybridized carbons via C−F bond cleavage, including cross-coupling and multi-component coupling reactions. The C−F bond cleavage mechanisms on the sp³-hybridized carbon centers can be primarily categorized into three types: Lewis acids promoted F atom elimination to generate carbocation intermediates; nucleophilic substitution with metal or carbon nucleophiles supported by the activation of C−F bonds by coordination of Lewis acids; and the cleavage of C−F bonds via a single electron transfer. The characteristic features of alkyl fluorides, in comparison with other (pseudo)halides as promising electrophilic coupling counterparts, are also discussed.     

Preparation of heterogeneous catalysts

The preparation of heterogeneous catalysts has been for many years a dynamic field of sub-nanotechnology and remains so nowadays. The approach to preparation must be examined in function of the specific demands concerning (i) activity and (ii) selectivity, that both depend on the arrangement of atoms at a scale smaller than 0.02 nm. Adequate access of reactants to the surface must be provided. Most catalysts are used in the form of pellets or cylinders obtained by pressing, extrusion or other techniques. This implies a control of texture at dimension scales extending from a fraction of a nanometer to several millimetres (and sometimes more). A third demand (iii) is resistance to ageing. In particular, stability at relatively high temperatures is necessary.The strategy adopted in the majority of cases is to start from a material that is homogeneous in composition at the Angström scale, generally a liquid or a solid of complex composition, frequently amorphous. A general objective is to locate the different constituting atoms at precise positions. The main difficulty is to transform the starting precursor into a highly porous solid without segregation of different elements that would produce tiny parts with different properties.The specific approach to catalyst preparation is based on the general concepts used for controlling the reactivity of solids. Typical methods of general use will be examined. Chemical bonds of practically any kind can retain the elements constituting the future catalyst at the position they have in the precursor. The so-called ‘citrate process’ and its variants are of wide application. More elaborate approaches start from molecules or polymers associating the necessary elements.     

镁合金用水溶性脱模剂 MK-300、MK-400的研制及其性能评价

研制开发了镁合金压铸用水溶性脱模剂MK-300、MK-400,可在高倍稀释的条件下使用,实验及实用结果显示MK-300、MK-400的脱模性、润滑性、高温附着性、模具保温性、模具残留物、铸件喷涂适应性、废液处理等均取得了满意的效果。     

An investigation of influencing of Sb and Bi contents on surface tensions associated with Pb-free Sn-Zn-Sb-Bi quaternary and sub-quaternary solder alloys

The surface tensions of ternary and quaternary systems of Sn-based Pb-free solder alloys have been calculated using geometric models, such as Muggianu, Kohler, Chou’s general solution model (GSM), Toop, Guggenheim, ideal Butler and Butler models. It is observed from the calculation carried out in the present work that Sb and Bi contents decrease the surface tension of the solder alloys Sn-Zn-Sb-Bi. It is inferred from the statistical analysis that the best agreement between the experimental results and the corresponding calculated values of the surface tensions is generally observed in GSM and Muggianu models among the geometric models. Whereas Muggianu model is the most appropriate. Relatively good agreements have been observed between models considered in this study and experimental data.     

磷酸氢二钾催化多组分一锅法反应合成1,4-二氢吡喃并[2,3-c]吡唑衍生物

绿色、简便、高效的催化四组分反应合成吡喃并[2,3-c]吡唑类杂环化合物是当今有机化学领域的研究热点。 本文发展了在水与聚乙二醇(PEG-200)的混合液中,廉价易得的磷酸氢二钾(K₂HPO₄·3H₂O)催化乙酰乙酸乙酯、水合肼、芳香醛和丙二腈的多组分“一锅法”反应,合成一系列1,4-二氢吡喃并[2,3-c]吡唑-5-腈衍生物,产率为88%~98%。 该方法避免了使用复杂昂贵的催化剂和繁琐的纯化过程。     

碘作为Lewis酸催化剂在合成中的应用

碘催化的有机反应具有价廉易得、操作简单、温和、清洁、高效及高选择性等优点, 广泛应用于亲电反应、亲核反应、多组份反应以及其它涉及复杂官能团化合物的合成反应中, 在环境友好化学合成、复杂化合物合成及选择性合成领域具有应用价值.     

Ga(OTf)3-catalyzed Three-component Mannich Reaction in Water Promoted by Ultrasound Irradiation

Ga(OTf)₃‐catalyzed three‐component Mannich reaction of aromatic aldehydes, aromatic amines and cycloketones in water promoted by ultrasound gave the corresponding β‐amino cycloketones in good to excellent yields and good anti selectivities.