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971.
S. K. Chattopadhyay 《合成通讯》2013,43(24):3033-3078
1,2- and 2,1-benzothiazines, for example, 1,2-benzothiazine-1,1-dioxides. 2,benzothiazine-2,2-dioxides, 1-alkyl/aryl-1,2-/2,1-benzothiazine-S-oxides, dibenzothiazine and polyheterocycle containing benzothiazine moiety are considered to be one of the privileged heterocyclic scaffolds with huge importances both in synthetic organic chemistry and medicinal chemistry especially in the drug industry. Numerous pioneering methodologies for asymmetric and non-asymmetric scaffold constructions have been developed. Comprehensive visions of different powerful methodologies for the synthesis of these scaffolds have been presented in this review. 相似文献
972.
Silvia Pérez‐Silanes Goutham Devarapally Enrique Torres Elsa Moreno‐Viguri Ignacio Aldana Antonio Monge Philip W. Crawford 《Helvetica chimica acta》2013,96(2):217-227
The electrochemical properties of 24 1,4‐dioxidoquinoxalin‐2‐yl ketone derivatives with varying degrees of anti‐Chagas activity were investigated in the aprotic solvent dimethylformamide (DMF) by cyclic voltammetry and first‐derivative cyclic voltammetry. For this group of compounds, the first reduction in DMF was either reversible or quasireversible and consistent with reduction of the N‐oxide functionality to form the radical anion. The second reduction process for these compounds was irreversible under the conditions used. The reduction potentials correlated well with molecular structure. Substitution in the 3‐, 6‐, and 7‐ positions of the quinoxaline ring by electron‐withdrawing substituents directly affected the ease of reduction and improved the biological activities of these compounds, whereas substitution by electron‐donating groups had the opposite effect. The electrochemical results, when combined with previous work on their mechanism of action against Chagas disease and their measured anti‐Chagas activities, indicated that the quinoxaline 1,4‐dioxide system serves as a promising starting point for chemical modifications aimed at improving the T. cruzi activity via a possible bioreduction mechanism. 相似文献
973.
Yuan‐Yuan Li Ping Liu Yang Tang Hong‐Mei Li Ya‐Ling Tang Xin‐Hua Liang Ya‐Jie Tang 《Helvetica chimica acta》2013,96(4):702-709
The four new cerebrosides 1 – 4 possessing a unique C18 9‐methylsphinga‐4,8‐dienine‐related moiety and a cyclic octapeptide, 5 , possessing alternating proline and glycine moietes were isolated from the Tuber indicum fermentation mycelium. Their structures were established on the basis of a spectroscopic analysis including NMR and HR‐ESI‐MS, as well as an acidic methanolysis experiment. To the best of our knowledge, the cerebrosides identified in the present study are quite different from those isolated from Tuber indicum fruiting bodies. Additionally, it was the first time that a cyclic peptide was isolated from the Tuber genus. 相似文献
974.
Cyclopropyl ester (8a-f) were synthesized by the cyclopropanation of chalcones (7a-e) in dry benzene using powdered sodium in 80-85% yield. Preparation of tetralone ester (4a-e), an intermediate for the synthesis of podophyllotoxin derivatives by Lewis acid (SnCl4) catalyzed cyclization of (8a-e) is also described here. 相似文献
975.
用量子理论计算柠檬黄、日落黄、胭脂红的相对焓(Hm)、相对熵(Sm),计算柠檬黄、日落黄、胭脂红的还原电位分别为-0.969,-0.901,-0.854V(vs.Ag/AgCl/Cl)。探讨了琼脂对色素的电催化机理,采用循环伏安法在玻碳琼脂电极上研究了食用色素柠檬黄、日落黄、胭脂红的电化学行为,分别于-1.064,-0.910,-0.882V(vs.Ag/AgCl/Cl)产生还原峰,理论预测与试验结果基本一致。 相似文献
976.
The paper combines a self-adaptive precise algorithm in the time domain with Meshless Element Free Galerkin Method (EFGM)
for solving viscoelastic problems with rotationally periodic symmetry. By expanding variables at a discretized time interval,
the variations of variables can be described more precisely, and iteration is not required for non-linear cases. A space-time
domain coupled problem with initial and boundary values can be converted into a series of linear recursive boundary value
problems, which are solved by a group theory based on EFGM. It has been proved that the coefficient matrix of the global EFG
equation for a rotationally periodic system is block-circulant so long as a kind of symmetry-adapted reference coordinate
system is adopted, and then a partitioning algorithm for facilitating parallel processing was proposed via a completely orthogonal
group transformation. Therefore instead of solving the original system, only a series of independent small sub-problems need
to be solved, leading to computational convenience and a higher computing efficiency. Numerical examples are given to illustrate
the full advantages of the proposed algorithm.
The project supported by the National Natural Science Foundation of China ((10421002, 10472019 and 10172024); NKBRSF (2005CB321704)
and the Fund of Disciplines Leaders of Young and Middle Age Faculty in Colleges of Liaoning Province. The English text was
polished by Yunming Chen. 相似文献
977.
Dr. Jia Tang Fen Wei Prof. Dr. Shujiang Ding Prof. Dr. Xiaoxia Wang Dr. Guanqun Xie Prof. Dr. Hongbo Fan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(50):12890-12899
Chemical fixation of CO2 as C1 source at ambient temperature and low pressure is an energy-saving way to make use of the green-house gas, but it still remains a challenge since efficient catalyst with high catalytic active sites is required. Here, a novel monoclinic azo-functionalized Zr-based metal−organic polyhedron (Zr-AZDA) has been prepared and applied in CO2 fixation with epoxides. The inherent azo groups not only endow Zr-AZDA with good solubilization, but also act as basic sites to enrich CO2 showing efficient synergistic catalysis as confirmed by TPD-CO2 analysis. XPS results demonstrate that the Zr active sites in Zr-AZDA possess suitable Lewis acidity, which satisfies both substrates activation and products desorption. DFT calculation indicates the energy barrier of the rate-determining step in CO2 cycloaddition could be reduced remarkably (by ca. 60.9 %) in the presence of Zr-AZDA, which may rationalize the mild and efficient reaction condition employed (80 °C and 1 atm of CO2). The work provides an effective multi-functional cooperative method for improvement of CO2 cycloaddition. 相似文献
978.
与二茂铁酰基相连的螺噁嗪的合成、结构及性质 总被引:3,自引:1,他引:2
在二环已基碳二亚胺(DCC)存在下, 将9′-羟基螺噁嗪与二茂铁甲酸进行酯化缩合, 合成了一种与二茂铁酰基相连的螺噁嗪衍生物2, 用核磁共振氢谱、碳谱、红外光谱、高分辨质谱和X射线单晶衍射对其结构进行了表征. 化合物2在几种有机溶剂中都表现出了良好的光致变色性质; 通过实验证明了在无冰水浴冷却条件下, 用高压汞灯照射时化合物2在二氯甲烷中表现出的特殊变色性是酸致变色的结果; 同时还研究了化合物2在固体PMMA薄膜中的光致变色性质. 在高压汞灯照射下,化合物2在二氯甲烷溶液中显示了良好的荧光性. 循环伏安法测定结果表明化合物2具有良好的氧化还原可逆性. 相似文献
979.
980.
A. I. Mikaya E. A. Trusova V. G. Zaikin L. A. Zegel'man A. B. Urin N. P. Volinsky 《Journal of separation science》1984,7(11):625-628
This article describes a method that assists in structure determination of cyclic sulfides mixtures by GC/MS. The method involves the use of a gas-phase hydrodesulfurization microreactor (AP-56 catalyst, reaction temperture 300-315°C, hydrogen as a carrier and reagent gas) located between the capillary column (OV-17) and the mass spectrometer. The presence of a microreactor in such a position does not essentially affect the chromatographic separation achieved by using the capillary column. Combined analysis of the mass spectra registered for the original sulfides and the hydrodesulfurization products permits the structure determination of each effluent to be made more reliably. This is illustrated by the investigation of a reaction mixture containing the structural and geometric isomers of methyl-substituted thiabicyclononanes. 相似文献