共查询到20条相似文献,搜索用时 62 毫秒
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自从Talbott[’j申请了第~个制备二氧环烷的专利以来,二氧环烷的制备与性能研究受到愈来愈多有机化学家的重视[‘-‘j.这种新型氧化剂与传统氧化剂相比,具有许多优越性.它不仅具有较强的氧传递功能,而且反应条件极其温和,操作相当方便,产物不需要复杂的纯化过程,能够给出很高的反应产率,为药物及其活性天然产物的结构改造与修饰提供了更加适用的途径.为了探索这种氧化剂与不饱和天然产物双键之间的反应行为,我们在成功地制备二甲二氧环烷丙酮溶液的基础上,将所得溶液用于一些不同类型双键环氧化反应,不仅方便、快速和高产… 相似文献
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在无有机溶剂做介质的条件下,用硅胶吸附的高锰酸钾氧化6种难溶于水的液态烯烃,得到了双键发生断裂的氧化产物。该反应操作简便,反应快,收率好。此外,对硅胶的活化作用机制进行了浅要。 相似文献
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碳碳双键是有机化学中最基本的官能团之一 ,在众多构筑碳碳双键的方法中Ramberg B cklund反应占有很重要的地位 .该方法的关键步骤是α 卤代砜在碱性条件下 ,发生 1,3 消除反应 ,得到环状砜 ,然后重排失去SO2 形成双键 ,这样形成的双键位置确定 ,即具有良好的区域选择性 ,并且在不同的反应条件下可得到不同构型的产物 ,因而在有机合成中有很好的应用前景 .对Ramberg B cklund反应进行了较为详细的综述 ,并对我们实验室所进行的反应条件的改进和优化以及目前的研究进展作了总结 . 相似文献
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Cu3/2PMo12O40改性骨架镍催化剂上羰基和碳-碳双键的加氢反应 总被引:5,自引:0,他引:5
研究了Cu3/2PMo12O40表面改性的骨架镍催化剂上含羰基化合物(正丁醛、异丁醛、丙酮、丁酮和环己酮)及含碳-碳双键化合物(苯、糠醇和1-辛烯)的加氢反应.结果表明,随着骨架镍催化剂上Cu3/2PMo12O40附着量的增加,含羰基化合物的加氢反应速率上升,而含碳-碳双键化合物的加氢反应速率下降.与未改性的骨架镍催化剂相比,当骨架镍催化剂上Cu3/2PMo12O40附着量为6.3%时,羰基的加氢活性提高2倍以上,碳-碳双键的加氢活性下降30%以上.计算了各种化合物在催化剂上的表观活化能.结果表明,Cu3/2PMo12O40表面改性的骨架镍催化剂上,羰基加氢反应的表观活化能降低,而碳-碳双键加氢反应的表现活化能升高.从动力学角度讨论了Cu3/2PMo12O40对骨架镍催化剂的影响.用XPS对骨架镍表面的Cu3/2PMo12O40进行了研究,发现杂多酸盐的Keggin型结构已被破坏,Cu3/2PMo12O40分子中的Cu2+被还原为Cu0,而Mo6+被部分还原为Mo5+和Mo4+;Cu2+和Mo6+价态的变化是由骨架镍表面吸附的活泼氢所引起的.羰基加氢选择性的提高是Cu0和混合价态Mo共同作用的结果. 相似文献
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Ghanashyam BezCong-Gui Zhao 《Tetrahedron letters》2003,44(40):7403-7406
Optically active aldehydes have been successfully used as catalysts for asymmetric epoxidations of unfunctionalized alkenes (ee up to 94%) by using Oxone® as the oxygen source. Experimental results indicate that the in-situ-generated aldehyde dioxirane is responsible for this catalytic activity. 相似文献
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D. A. Bykov A. N. Zaderko A. M. Datsyuk V. E. Diyuk V. K. Yatsimirskii V. V. Lobanov 《Theoretical and Experimental Chemistry》2008,44(1):32-36
LCAO MO SCF calculations using the 3-21G basis were used to study the electronic and three-dimensional structure of several
polycyclic aromatic hydrocarbons as models for the surface of activated charcoal. Localized carbon-carbon double bonds capable
of adding electrophilic reagents were found on the periphery of these molecules. The reactivity of the peripheral C=C bonds
was evaluated relative to consecutive bromination reactions of the C54H18 molecule.
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Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 1, pp. 30–34, January–February, 2008. 相似文献
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Yu-Mei Shen 《Tetrahedron letters》2006,47(31):5455-5458
This letter describes a highly enantioselective epoxidation of tetrasubstituted benzylidenecyclobutanes using glucose-derived ketone as catalyst and oxone as oxidant. The Et2AlCl promoted rearrangement of the resulting epoxides provides 2-alkyl-2-aryl cyclopentanones with high ees. 相似文献
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《Journal of organometallic chemistry》2004,689(11):1919-1929
Reduction of methyl-substituted titanocene dichlorides bearing pendant double bonds [TiCl2{η5-C5Me4(CH2CMeCH2)}2] (1) and [TiCl2{η5-C5Me4(SiMe2(CH2)2CHCH2)}2] (2) with magnesium yielded diamagnetic Ti(IV) compound [Ti{η1:η1:η5-C5Me3(CH2)(CH2CH(Me)CH2)}{η5-C5Me4(CH2C(Me)CH2)}] (4) and paramagnetic Ti(III) compound [Ti{η5-C5Me4(SiMe2CH2CHCHMe)}(μ-η3,η1:η5,η1(Ti:Mg){C5Me3(CH2)(SiMe2CHCHCMe)})Mg(OC4H8)2] (6), respectively. The reluctance of titanocene intermediates to undergo intramolecular cyclization to cyclopentadienyl-ring-tethered titanacycles (as typically observed) can be explained by a shortness of the 2-methylallyl group and steric hindrance of its double bond in the former case and, in the latter case, by an attack of magnesium on the titanocene intermediate, faster than cyclization reactions. The crystal structures of 4 and 6 were determined by single-crystal X-ray diffraction. 相似文献
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The enantioselective total syntheses of (+)-decursin (1) and related natural dihydropyranocoumarins (−)-prantschimgin (3), (+)-decursinol (4), and (+)-marmesin (5) were achieved for the first time using catalytic asymmetric epoxidation of an enone as the key step. Catalytic asymmetric epoxidation of the enone was effectively promoted by the novel multifunctional asymmetric catalyst generated from La(O-i-Pr)3, BINOL, and Ph3AsO in a 1:1:1 ratio to afford epoxide in 94% yield and 96% ee, which was recrystallized to give optically pure epoxide. After conversion to the common key intermediate (−)-peucedanol (7), all natural dihydropyranocoumarins were synthesized through palladium-catalyzed intramolecular C-O coupling reactions. A possible reaction mechanism of the catalytic asymmetric epoxidation of enones is also described based on X-ray analysis, laser desorption/ionization time-of-flight mass spectrometry, kinetic studies, and asymmetric amplification studies. 相似文献
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选择性地向有机物中引入氟原子越来越受到重视,近年来通过碳碳不饱和键的 氟化加成来引入氟原子发展迅速。综述了碳碳不饱和键氟化加成反应的研究进展。 相似文献
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钯催化下有机锡化合物的偶联反应在碳-碳键形成过程中的应用 总被引:2,自引:0,他引:2
本文述评了最近几年来钯催化的有机锡化合物与有机亲电试剂的交叉偶联反应在有机合成中用于碳-碳键形成的主要研究成果。主要讨论了直接交叉偶联反应,CO或烯键插入的交叉偶联反应和机理。 相似文献
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Xishan Bai Mattia Cettolin Giulia Mazzoccanti Marco Pierini Umberto Piarulli Valentina Colombo Alberto Dal Corso Luca Pignataro Cesare Gennari 《Tetrahedron》2019,75(10):1415-1424
In this paper, we describe a small library of easy-to-prepare chiral (cyclopentadienone)iron pre-catalysts for enantioselective CO and CN hydrogenations. Starting from readily accessible achiral materials, six chiral (cyclopentadienone)iron complexes (1a-f) possessing a stereogenic plane were synthesized in racemic form. Based on the screening of pre-catalysts (±)-1a-f in the hydrogenation of ketones and ketimines, we selected two complexes (1a and 1d) for resolution by semipreparative enantioselective HPLC. The absolute configuration of the separated enantiomers of 1a and 1d was assigned by XRD analysis (1a) and by comparison between experimental and DFT-calculated ECD and ORD spectra (1d). The enantiopure pre-catalysts (S)-1a and (R)-1d were tested in the asymmetric hydrogenation of several ketones and ketimines and showed good activity and modest enantioselectivity, the e.e. values ranging from very low to moderate (54%). 相似文献