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81.
The enantioselective O-allylic alkylation of acetophenone oxime with various Morita-Baylis-Hillman (MBH) carbonates has been accomplished by the catalysis of a commercially available cinchona alkaloid (DHQD)2PHAL. The corresponding O-allylic products were obtained in moderate to excellent yields up to 96% ee. 相似文献
82.
考察了系列氧化剂、催化剂和溶剂对环己胺液相氧化制备环己酮肟的影响,发现以乙腈为溶剂,过氧化氢为氧化剂,NaY型沸石分子筛对该反应具有优良的催化性能。 对该反应体系进行了五因素四水平的正交实验,确定了适宜的催化剂用量、溶剂用量、反应时间、反应温度和氧化剂用量,比较分析了各因素对环己胺转化率和环己酮肟选择性的影响。 确定了环己胺液相氧化反应的最佳工艺条件为:环己胺为3 mL,催化剂为03 g,环己胺、溶剂和氧化剂的体积比为1∶3∶3,65 ℃反应2 h。 讨论了环己胺液相催化氧化的反应机理。 相似文献
83.
84.
苯乙酮肟醚α碳负离子在添加 HMPA 的条件下,顺利实现了对单取代和环状氮杂环丙烷的开环,取得中等到良好的收率。四氢萘酮肟醚 α 碳负离子在该条件下也可以对部分氮杂环丙烷开环。反应中 HMPA 起到对锂离子的络合作用,可以在一定程度上增加碳负离子的亲核性。 相似文献
85.
86.
Somasekhar Bondalapati Emil Ruvinov Olga Kryukov Smadar Cohen Ashraf Brik 《Macromolecular rapid communications》2014,35(20):1754-1762
Polysaccharides have emerged as important functional materials because of their unique properties such as biocompatibility, biodegradability, and availability of reactive sites for chemical modifications to optimize their properties. The overwhelming majority of the methods to modify polysaccharides employ random chemical modifications, which often improve certain properties while compromising others. On the other hand, the employed methods for selective modifications often require excess of coupling partners, long reaction times and are limited in their scope and wide applicability. To circumvent these drawbacks, aniline‐catalyzed oxime formation is developed for selective modification of a variety of polysaccharides through their reducing end. Notably, it is found that for efficient oxime formation, different conditions are required depending on the composition of the specific polysaccharide. It is also shown how our strategy can be applied to improve the physical and functional properties of alginate hydrogels, which are widely used in tissue engineering and regenerative medicine applications. While the randomly and selectively modified alginate exhibits similar viscoelastic properties, the latter forms significantly more stable hydrogel and superior cell adhesive and functional properties. Our results show that the developed conjugation reaction is robust and should open new opportunities for preparing polysaccharide‐based functional materials with unique properties.
87.
The electron paramagnetic resonance (EPR) spectra of gamma irradiated single crystals of alpha-benzoinoxime (ABO) have been examined between 120 and 440 K. Considering the dependence on temperature and the orientation of the spectra of single crystals in the magnetic field, we identified two different radicals formed in irradiated ABO single crystals. To theoretically determine the types of radicals, the most stable structure of ABO was obtained by molecular mechanic and B3LYP/6-31G(d,p) calculations. Four possible radicals were modeled and EPR parameters were calculated for the modeled radicals using the B3LYP method and the TZVP basis set. Calculated values of two modeled radicals were in strong agreement with experimental EPR parameters determined from the spectra. Additional simulated spectra of the modeled radicals, where calculated hyperfine coupling constants were used as starting points for simulations, were well matched with experimental spectra. 相似文献
88.
89.
《Journal of Coordination Chemistry》2012,65(1-3):159-169
The synthesis and characterization of a new series of iron(II) clathrochelate complexes, including the first example of a binuclear covalently linked c1athrochelate complex, is reported. The ligand system is based on the bifunctional chelate 2,3-butanedione oxime hydrazone which forms a tris-complex with iron(II). The c1athrochelate is completed by capping the complex with both a boronic acid/oxime capping reaction and a formaldehyde/hydrazone capping reaction. Electrochemical and spectroscopic characterizations of the complexes are discussed. 相似文献
90.
《Analytical letters》2012,45(12):2351-2359
Abstract Amperometric biosensors containing enzymes butyrylcholinesterase or acetylcholinesterase were prepared. The biosensors were employed for studying of cholinesterase reactivator: HI‐6. Competitions between HI‐6 and acetylthiocholine as enzyme substrate were used for determination of IC50 value. Biosensors with butyrylcholinesterase from human serum determined IC50 as (1.00±0.02)×10?6 M; the biosensor with acetylcholinesterase from human erythrocytes performance provided IC50 (3.31±0.13)×10?6 M, the one with human recombinant acetylcholinesterase (2.00±0.06)×10?6 M and finally biosensor with acetylcholinesterase from electric eel (6.17±0.17)×10?6 M when 5 mM acetylthiocholine as substrate was used. We are encouraged to consider presented biosensors as a very useful for evaluation of newly prepared cholinesterase reactivators. 相似文献