排序方式: 共有19条查询结果,搜索用时 15 毫秒
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Yuehai ShenJianxun Wen 《Journal of fluorine chemistry》2002,113(1):13-15
A new and efficient route has been developed to synthesize 17β-(1-methyl-3-perfluoroalkyl)propyl-3β-androsterol (1) in nine steps from hyodeoxycholic acid via selective addition of 1-perfluoroalkyl iodide to 24-norchola-5,22-dien-3β-ol. From (1), the first series of steroidal liquid crystalline aliphatic esters (smectic A) with fluorocarbon side chains has been prepared. 相似文献
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The C1–8 fragment of autolytimycin was synthesized via a reliable 10-step route capable of delivering 41% overall yield at multi-gram scale. As a key step, a chelation-controlled isopropenylation of α-oxygenated aldehydes was established with a reagent combination of diisopropenylzinc, magnesium halide, and a dichloromethane/toluene mixed solvent. Cram-chelate isopropenylation products dominated for aldehydes with a small α-substituents, such as –OMe and –OBn groups, while the Felkin product could be obtained with a bulky –OTBS group. 相似文献
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A novel metal-free oxidative arylphosphination of activated N-substituted-N-arylacrylamide derivatives by phosphorylation and C–H functionalization cascade process has been developed. This methodology provides an efficient way to construct a variety of phosphorus-containing oxindole moieties. 相似文献
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Yuehai Liang B. Dabrowski C. W. Kimball Weimin Peng
B. D. Dunlap
《Physica C: Superconductivity and its Applications》1992,190(4):415-426Mössbauer studies on 57Fe-doped superconducting REBa2Cu3O7+δ (RE=Er, Dy) were made as a function of temperature for x=0.15 and 0.30. The magnetic behavior of the 3d dopants, which mainly occupy Cu(1) sites, undergoes antiferromagnetic ordering which is coexistent with superconductivity at low temperature. The dimensionality of the magnetic interaction changes from 2D to 3D when the rare earth changes from Er to Dy. the line-widths of the Mössbauer subspectra are characteristic of magnetic fluctuation behavior in the vicinity of a phase transition. Combining these results with those of Fe-doped Y-123 (pseudo 1D) and Gd (3D), the magnitude of the rare earth moments appears to be strongly correlated with the dimensionality of the magnetic interaction of Fe dopants in these compounds. However, the Mössbauer spectrum for 155Gd in GdBa2Cu2.85Fe0.15O7+δ (TN(Fe) 14 K) shows no magnetic order at 4.9 K. 相似文献
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A novel arylnitration of alkenes by nitration and C–H functionalization cascade process has been developed. This methodology provides an efficient way to construct a variety of nitro-containing oxindoles and dihydroquinolin-2(1H)-ones. In addition, the process exhibits significant functional group tolerance. Moreover, the use of inexpensive and readily available starting materials makes this practical and atom-economical approach particularly attractive. 相似文献
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Two series of steryl di- and tri-fluorobenzoate liquid crystal materials were synthesized and their phase transition behaviours studied by DSC and thermal polarizing microscopy. The results show that para-fluorine substituents stabilize the mesogenicity whilst meta-fluorines depress it to a weak degree. 相似文献
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A series of cholesteryl p-perfluoroalkylphenyl carbonate (CPC) [C27H45OCO2C6H4(CF2)nF, n=1,4,6,8] liquid crystals was synthesized and their phase transition behaviours were studied. The results show that the compounds containing a not too long perfluoroalkyl chain (n=6,8) have monotropic chiral smectic C phases. 相似文献
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Zhu Jiaping Jin Shaohua Yu Yuehai Li Lijie Chen Shusen Shu Qinghai 《Research on Chemical Intermediates》2016,42(5):4333-4340
Research on Chemical Intermediates - 4,4-azo-bis(1,2,4-triazol-5-one) (ZTO) and its solvent adducts have been reported, and the single crystal X-ray measurements indicated that the ZTO crystals... 相似文献