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171.
Ze-Shui Liu Guangyin Qian Qianwen Gao Peng Wang Hong-Gang Cheng Yu Hua Qianghui Zhou 《Tetrahedron》2019,75(12):1774-1780
Mediators play a central role in Catellani-type reactions. Herein we reported the discovery of inexpensive 5-norbornene-2-carboxylic acid (N4) as a general catalytic mediator (20?mol%) to facilitate ortho C–H activation and the following C–C bond formation of aryl iodides. Firstly, a cooperative catalytic system comprising N4 and a palladium/XPhos complex was developed for the novel Catellani/redox-relay Heck cascade to construct tetrahydronaphthalenes and indanes that contain a quaternary carbon stereogenic center. The striking feature of this work was the avoidance of stoichiometric NBE mediator that are usually required for Catellani-type reactions. Then, preliminary results demonstrated that N4 could act as a general catalytic mediator to replace NBE for other Catellani-type reactions, which will undoubtedly inspire future developments in the field of cooperative catalysis. Finally, control experiments indicated that the carboxylic acid moiety of N4 plays an essential role in its ability to serve as a superior mediator. 相似文献
172.
Zong‐Yun Li Hui‐Min Gao Jian Sun Liang‐Mian Chen Zhi‐Min Wang Qi‐Wei Zhang 《Helvetica chimica acta》2012,95(7):1144-1151
The new secoiridoid sulfonates 1 – 3 were isolated from the 50% EtOH/H2O extract of the sulfiting‐processed Lonicera japonica Flos (LJF) by semi‐prep. HPLC, and their structures were identified on the basis of mass spectrometry and NMR spectroscopy. HPLC and LC‐DAD‐MS/MS analyses of the different samples of LJF obtained by various process techniques suggested that the sulfur fumigation led to the decrease of secologanic acid ( 4 ) and the formation of secologanic acid‐derived sulfonate 1 and its derivatives 2, 2a , and 3 in the crude materials, which revealed that sulfur fumigation, the traditional process technique, could alter the phytochemical profiles of some Chinese herbal medicines. 相似文献
173.
采用相溶解度法,通过测定丹皮酚在不同温度不同浓度的β-环糊精(β-CD)、羟丙基-β-环糊精(HP-β-CD)、羟乙基-β-环糊精(HE-β-CD)、取代度为4的磺丁基醚-β-环糊精(SBE4-β-CD)以及取代度为7的磺丁基醚-β-环糊精(SBE7-β-CD)中的溶解度,绘制相溶解度曲线,丹皮酚的溶解度均随5种环糊精浓度的增加而成线性增加,相溶解度曲线为AL型,说明丹皮酚与环糊精以1∶1包合,实验结果表明,5种环糊精对丹皮酚均有增溶作用且SBE7-β-CD的增溶效果最佳. 相似文献
174.
175.
In this work, the use of mini cantilever beams for characterization of rheological properties of viscous materials is demonstrated. The dynamic response of a mini cantilever beam partially submerged in air and water is measured experimentally using a duel channel PolyTec scanning vibrometer. The changes in dynamic response of the beam such as resonant frequency, and frequency amplitude are compared as functions of the rheological properties (density and viscosity) of fluid media. Next, finite element analysis (FEA) method is adopted to predict the dynamic response of the same cantilever beam. The numerical prediction is then compared with experimental results already performed to validate the FEA modeling scheme. Once the model is validated, further numerical analysis was conducted to investigate the variation in vibration response with changing fluid properties. Results obtained from this parametric study can be used to measure the rheological properties of any unknown viscous fluid. 相似文献
176.
177.
Hongxia Liu Lin Gao Mian Liu Qin Li Yuyang Jiang Shusheng Zhang 《Microchemical Journal》2006,84(1-2):38-43
A practical method for the analysis of genipin-1-β-gentiobioside in gardenia fruit was developed by high-performance liquid chromatography with ultraviolet monitoring and electrospray ionization mass spectrometry characterization (HPLC/UV/ESI-MS). Efficiency of ultrasonic extraction (UE), accelerated solvent extraction (ASE) and high-speed homogenizer extraction (HHE) on genipin-1-β-gentiobioside in gardenia fruit was compared. UE gave higher extraction efficiency and lower matrix interference, and it was employed. Analysis of genipin-1-β-gentiobioside was performed using a Supelco C18 column with methanol–20 mM NH4Ac (30:70, v/v) as the eluent. Flow rate was at 0.8 ml/min, and the detection was at 240 nm. The limit of detection (LOD), using HPLC/UV, was about 0.25 μg/ml, whereas the overall recovery was better than 96.0%. Both full scan MS and MS2 of genipin-1-β-gentiobioside with positive polarity were obtained and elucidated. The specific ions were chosen to characterize genipin-1-β-gentiobioside in gardenia fruit sample. The proposed method has been successfully applied to measure the real samples and the content profiles of genipin-1-β-gentiobioside in gardenia fruit samples were obtained and evaluated. 相似文献
178.
In this paper, a straightforward and valid three-component Michael/cyclization reaction of (E)-1-methyl-3-(arylidene)piperidin-4-ones, 2-(sulfonyl)acetonitriles, and aromatic aldehydes was explored for the preparation of potentially biologically active 3-(sulfonyl)-5,6,7,8-tetrahydro-4H-pyrano[3,2-c]pyridines under mild reaction conditions. More diverse 3-(sulfonyl)-5,6,7,8-tetrahydro-4H-pyrano[3,2-c]pyridine derivatives were constructed in satisfactory yields (up to 97%). The chemical structure of newly synthesized 3-(sulfonyl)-5,6,7,8-tetrahydro-4H-pyrano[3,2-c]pyridines were identified with 1H-NMR, 13C-NMR, and mass spectrometry analysis. The recommendable method features a simple and direct workup, easy access to initial materials, high atom utilization efficiency, high final product yields, and a wide range of substrate adaptability. 相似文献
179.
Chi Zhang Yan‐Min Wang Feng‐Chun Zhao Liang‐Mian Chen Qi‐Wei Zhang Hui‐Min Gao Zhi‐Min Wang 《Helvetica chimica acta》2014,97(11):1516-1525
Two new compounds, (?)‐(6aR,11aR)‐4‐methoxy‐8,9‐(methylenedioxy)pterocarpan 3‐O‐β‐D ‐glucopyranoside ( 1 ) and 5‐hydroxy‐7‐methoxyisoflavone 4′‐O‐β‐D ‐xylopyranosyl‐(1→6)‐β‐D ‐glucopyranoside ( 2 ), were isolated, together with 30 known compounds from the stems and leaves of Sophora flavescens Aition . Their structures were elucidated by extensive spectroscopic analysis, including HR‐ESI‐MS data. A preliminary comparison of phenolic metabolite profiles, based on the qualitative HPLC analysis, indicated that the composition of the roots and the aerial parts were significantly different. 相似文献
180.
为研究滇产玉米须中的化学成分,采用硅胶柱层析和Sephadex LH-20柱层析进行化合物分离和纯化,采用EI-MS、HR-ESI-MS、1D-和2D-NMR以及化学方法对化合物结构进行鉴定。从滇产玉米须中分离得到了4个化合物,分别鉴定为:(2S,3S,4R)-2-[(2’R)-2’-hydroxydocosanoylamino]-1,3,4-octadecanetriol(1),ent-rosa-ne-5β,15,16-triol(2),麦角甾-7,22-二烯-3β,5α,6β-三醇(3),豆甾-5-烯-3β,7α-二醇(4)。化合物1和2为首次从玉米须中分离得到,并采用化学方法对化合物1进行结构确证,采用2D-NMR对这化合物2和3的碳氢数据进行准确归属。 相似文献