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2-吡喃酮是一种含有共轭二烯的杂环化合物,它可以作为一种特殊的双烯体参与Diels-Alder反应.经过几十年的发展,2-吡喃酮的Diels-Alder反应在复杂天然产物的合成中得到了广泛地应用.近年来,2-吡喃酮的催化不对称Diels-Alder反应也引起了合成化学家的关注.对2-吡喃酮参与的不对称正电子需求和反电子需求的Diels-Alder反应的发展,以及它们在天然产物全合成中的应用进行了总结. 相似文献
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钯催化的交叉偶联反应是非常实用的合成新方法.文章给出了Heck反应、Negishi反应和Suzuki反应的概念,对其反应机理作了详细的说明,并对其在复杂化合物和天然产物全合成中的应用作了评价. 相似文献
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综述了包括五种带电荷中间体通过碳-碳键形成杂环的反应:(1)亚胺翁离子-乙烯基硅烷的环化反应,(2)亲核试剂引发的亚胺翁离子-炔的环化反应,(3)缩醛-烯烃的环化反应,(4)aza-Cope-Mannich反应,(5)通过Prins-pinacol重排合成环醚的反应;以及这些反应在有机合成特别是在天然产物全合成研究的进展。 相似文献
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二芳基次甲基结构单元广泛存在于具有重要生理和药理活性的天然产物和药物当中. 同时, 该结构单元中所特有的二芳基次甲基立体中心的对映选择性构筑往往也是天然产物全合成的难点和挑战性所在. 因此, 引起了众多有机合成化学家的研究兴趣. 近年来, 该手性立体中心的构建方法发展迅速, 新方法和新反应的报道也层出不穷; 开发出来的一些高效催化剂, 展示出独特的催化活性和选择性. 本文根据反应类型的不同, 将其分为不对称共轭加成反应和不对称氢化反应等六类, 综述近十年来二芳基次甲基立体中心的不对称构建方法及相关方法在天然产物全合成中的应用. 最后, 从全合成的角度进一步总结和分析未来构建二芳基次甲基手性立体中心的发展趋势, 力求发展更加高效、避免贵金属的催化剂及环境友好型的新方法和新试剂. 相似文献
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V. I. Bol'shakova L. I. Demenkova É. N. Shmidt V. A. Pentegova 《Chemistry of Natural Compounds》1989,24(6):691-694
The compositions of the neutral diterpenoids of the oleoresins of five species of conifers growing in the Transcarpathia have been studied. It has been found that the oleoresins ofAbies alba M.,Larix decidua M., andPicea excelsa L. contain more than 50% of neutral diterpenoids. The group and qualitative compositions of the oxygen-containing diterpenoids have been determined. In the oleoresins ofAbies alba,Picea excelsa, andPicea abies tertiary alcohols — cis-abienol and isocembrol — predominate, while inLarix decidua the main component is the hydroxy ester larixyl acetate. Primary alcohols related to the resin acids have been found in all the oleoresins investigated. Features of the distribution of diterpenoids according to the species of conifers have been revealed. The results obtained are necessary for the chemotaxonomy of conifers of the family Pinceae.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Khimiya Prirodynkh Soedinenii, No. 6, pp. 812–816, November–December, 1988. 相似文献
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利用手持技术改进测定乙醇分子结构实验 总被引:1,自引:0,他引:1
利用压强传感器代替排水集气法,改进测定乙醇分子结构实验的仪器装置,并探索最佳反应条件。另外,设计两个空白实验,结合压强变化曲线对实验误差进行相关讨论。 相似文献
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由于石化行业的生产需要,其材质的使用具有多样性和广泛性,经常会出现顾客委托的测试样品的一个或几个元素跨越光谱仪现有测试程序测量范围的情况。本法通过对光谱仪测试原理的认识,根据光谱仪的测试能力及标样的采集,实现了一个或几个元素测量范围的扩展,并对其测量的影响因素进行了研究。 相似文献
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Effect of the Method of Modification of Zeolite X on Selectivity of Catalytic Methylation of Toluene
Voloshyna Yu. G. Pertko O. P. Patrylak L. K. 《Theoretical and Experimental Chemistry》2019,54(6):395-400
Theoretical and Experimental Chemistry - The effect of the method of modification of catalysts based on zeolite X by cesium and magnesium cations (ion exchange and impregnation) on the selectivity... 相似文献
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Influence of viscosity of medium on processes of oxygen quenching of excited states of mesoporphyrin
E. I. Kapinus V. A. Ganzha B. M. Dzhagarov E. I. Sagun V. B. Pavlenko 《Theoretical and Experimental Chemistry》1989,25(2):146-151
The oxygen quenching rate constants for singlet and triplet excited states of the dimethyl ester of mesoporphyrin IX increase with decreasing viscosity of the medium and reach a maximum at a viscosity of approximately 0.4 mPa·sec, after which the rate constants begin to decrease. The drop in rate constant with increasing fluidity of the medium may be related to a nonequilibrium character of the elementary act in the interaction of the reactants in the solvent cage. In viscous media such as isopropyl alcohol, isobutyl alcohol, and isoamyl alcohol, the reaction radius is greater than the sum of the radii of the reacting particles. The long-range character of these processes is due to the relatively weak dependence of the quenching probability on distance.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 161–167, March–April, 1989. 相似文献
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The spectral-polarization characteristics of absorption and phosphorescence of molecules of the initial form of nitro-substituted
indolinospirobenzothiopyran were studied in oriented polyethylene films and in solutions with different polarity. An oscillator
model of the electron transitions responsible for the formation of absorption and luminescence spectra was suggested. It was
established that the principal differences in the spectral and photophysical properties of the compound studied and its oxygen-containing
analog are associated with the fact that the electronegativity of the S atom is lower than that of the O atom.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1146, June, 1997. 相似文献
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Kopranenkov V. N. Makarova E. A. Dashkevich S. N. Luk'yanets E. A. 《Chemistry of Heterocyclic Compounds》1982,18(11):1218-1218
Chemistry of Heterocyclic Compounds - 相似文献