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排序方式: 共有167条查询结果,搜索用时 187 毫秒
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We demonstrate that molecules with a moderate permanent dipole moment can be oriented with combined electrostatic and pulsed, nonresonant laser fields. We use OCS molecules as a sample. The degree of orientation can be increased by increasing the magnitude of electrostatic field and the peak intensity of the laser field or by decreasing the rotational temperature of the molecules. 相似文献
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Sho Inagaki Akari Sato Haruka Sato Satoru Tamura Tomikazu Kawano 《Tetrahedron letters》2017,58(52):4872-4875
A simple and efficient synthesis of 4,5-dihydro-4-oxo-3-furancarboxylates using an acylative intramolecular cyclization of sulfonium salts is described. The reaction involved the efficient formation of a mixed anhydride between a linear carboxylic acid and trifluoroacetic anhydride in the presence of N-methylimidazole, followed by the sequential conversion into a highly reactive acylammonium species in situ. This procedure is easily handled, uses readily available inexpensive reagents, and provides a variety of 2-substituted 4,5-dihydro-4-oxo-3-furancarboxylates. 相似文献
14.
Kotaro Nagatani Yunosuke Hoshino Haruka Tezuka Masahisa Nakada 《Tetrahedron letters》2017,58(10):959-962
A synthetic pathway to the C-ring fragment of cotylenin A which emerged from our retrosynthetic analysis of cotylenin A is described. The catalytic asymmetric intramolecular cyclopropanation (CAIMCP) of the α-diazo-β-keto ester bearing 2,4,6-trimethylphenyl group as the ester part has been found to afford the crystalline product with high ee, which allowed to establish the approach to the C-ring fragment which required ten-pot operations. The developed approach would be beneficial to a large scale synthesis of the C-ring fragment for the total synthesis of cotylenin A. 相似文献
15.
Haruka Baba 《Tetrahedron letters》2010,51(15):2063-4307
Treatment of alkylbenzenes with p-toluenesulfonamide and 1,3-diiodo-5,5-dimethylhydantoin (DIH) in a small amount of carbon tetrachloride at 60 °C gave the corresponding α-p-toluenesulfonylamido)alkylbenzenes in good to moderate yields. The present reaction is a simple method for the α-sulfonylamidation of the benzylic position in alkylbenzenes. 相似文献
16.
Tomoyuki Miyazawa Haruka Abe Takayuki Suzuki Yosuke Togashi Kazuhiro Koshiji Yuki Nonaka 《Journal of carbohydrate chemistry》2013,32(5):252-266
We evaluated the potential of a linear β-1,3-glucan (curdlan) as a starting material to access C6-modified glucose derivatives and found that 6-bromo-6-deoxyglucose, 6-azide-6-deoxyglucose, and 6-acetamido-6-deoxyglucose could be readily prepared from curdlan through its C6-selective and quantitative modifications and subsequent acid-catalyzed hydrolysis. 相似文献
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Salt‐Free Reduction of Nonprecious Transition‐Metal Compounds: Generation of Amorphous Ni Nanoparticles for Catalytic C–C Bond Formation
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Dr. Taiga Yurino Yohei Ueda Dr. Yoshiki Shimizu Dr. Shinji Tanaka Haruka Nishiyama Prof. Dr. Hayato Tsurugi Prof. Dr. Kazuhiko Sato Prof. Dr. Kazushi Mashima 《Angewandte Chemie (International ed. in English)》2015,54(48):14437-14441
A salt‐free procedure for the generation of a wide variety of metal(0) particles, including Fe, Co, Ni, and Cu, was achieved using 2,3,5,6‐tetramethyl‐1,4‐bis(trimethylsilyl)‐1,4‐diaza‐2,5‐cyclohexadiene ( 1 ), which reduced the corresponding metal precursors under mild conditions. Notably, Ni particles formed in situ from the treatment of Ni(acac)2 (acac=acetylacetonate) with 1 in toluene exhibited significant catalytic activity for reductive C? C bond‐forming reactions of aryl halides in the presence of excess amounts of 1 . By examination of high‐magnification transmission electron microscopy images and electron diffraction patterns, we concluded that amorphous Ni nanoparticles (Ni aNPs) were essential for the high catalytic activity. 相似文献
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This paper presents a low-capacity cation-exchange chromatography method for the analysis of UV-absorbing dipeptides and amino acids. A newly marketed low-capacity cation-exchange column packed with sulfo-functionalized highly cross-linked macroreticular poly(ethylstyrene-divinylbenzene) copolymer was used for the simultaneous determination of imidazole amino acids, aromatic amino acids, and creatinine in urine samples. A dual-mode binary gradient chromatography method was established using two solvents, A: 15 mM H3PO4/5 mM ethylenediamine and B: 15 mM H3PO4/5 mM ethylenediamine/40 (v/v) % CH3CN at 40 °C, with an optimized time program for changing the delivery ratio of A/B and the flow rate. Good chromatograms were obtained within an acceptable cycle time of 25 min. The quantification data were satisfactory for all analytes, showing the relative standard deviations (RSD) of retention times between 0.08 and 1.68 %; RSDs of area intensities between 0.23 and 2.60 %; and linear regression lines with r 2 more than 0.9994. The method could determine the creatinine ratios of the diagnostic markers on the single chromatographic run, which enabled to discriminate disease from health. For example, the creatinine ratios for phenylketonuria were significantly higher than those for controls. The method can provide highly cost-efficient information or useful knowledge for clinical and pharmaceutical studies. 相似文献