共查询到18条相似文献,搜索用时 234 毫秒
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杯[4]芳烃的上端和下端通过金属复分解闭环反应以较高产率合成一系列新型杯[4]冠醚衍生物(8a-c),目标产物结构经元素分析、IR、MS、1H NMR及13C NMR证实。 相似文献
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为了得到稳定性更好、活性更高的烯烃复分解催化剂,本文采用有机合成的方法,以钌卡宾烯烃复分解催化剂为主体,用锌卟啉进行修饰,得到锌卟啉修饰的Grubbs-Hoveyda型双核钌卡宾烯烃复分解反应催化剂,产物结构使用核磁共振方法进行表征。 用0.1%化学计量催化剂催化几种代表性底物闭环复分解(RCM)反应产率能达到95%,对于特定的交叉烯烃复分解反应(CM),延长反应时间也能得到93%的较高产率。 研究结果为Grubbs-Hoveyda催化剂的修饰提供了新方法和理论依据。 相似文献
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综述了过渡金属均相催化的炔烃复分解反应进展,主要分为两部分:一是炔烃复分解反应在炔烃合成中的应用,即从六、七十年代Mortreux催化剂的发现能均相催化炔烃的歧化反应,经过一系列的条件改造,合成了炔醚和二芳基乙炔等化合物,并提出了可能的两种机理:金属卡宾和金属卡拜机理;金属钼和钨的卡拜络合物相继合成,发现此类络合物能够催化官能化的二炔的复分解反应,合成一系列的大环化合物。二是炔烃复分解反应在合成高聚物中的应用,即钙和钨的卡拜络合物被用来催化ROMP和ADIMET反应合成高聚物,改良了的Mortreux催化剂也能催化高聚物的生成,这些高聚物在发光器件、有机"塑料"激光、液晶显示器上都有应用。 相似文献
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2005年诺贝尔化学奖授予在烯烃复分解合成转换方面做出重要贡献的3位科学家:Y ves Chauvin,Richard R.Schrock和Robert H.Grubbs.简要介绍了3位获奖者的主要贡献,烯烃复分解反应的分类和催化反应机理,金属卡宾催化剂及烯烃复分解反应的一些应用.另外,介绍了此领域目前研究的主要科学问题. 相似文献
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核苷类似物可以参与并干扰细菌(病毒)的DNA或RNA过程,抑制其生长和繁殖,从而有希望发展为抗肿瘤抗病毒药物。一些天然的核苷化合物虽然表现出一定的生理活性,在体内缺乏酶稳定性和靶向选择性却限制了其在医药领域的应用,合成具有生物活性的化学修饰的核苷及其衍生物是核酸药物化学中的重要课题。一类在金属卡宾复合物催化下的分子内或分子间烯烃重组反应-----复分解反应的发展使核苷类似物的合成进入了新阶段, 烯烃复分解反应成为核苷类似物合成的主要途径之一。随着施洛克催化剂、格拉布催化剂等复分解反应催化剂的发现和不断改进,烯烃复分解反应,尤其是关环复分解和交叉复分解反应被广泛应用于构建核苷类似物的糖环(或伪糖)结构或连接核苷类似物单体而形成核苷多聚物。本文对烯烃复分解反应在核苷类似物包括碳环核苷,2’,3’-双脱氧核苷,无环核苷,多环核苷及核苷二聚体或三聚体的合成中的应用进行了综述。 相似文献
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过渡金属催化活化C―H键来构建新共价键因具有原子经济和合成简捷的特点,已成为合成化学中最为有效策略之一。本文中,我们总结了过渡金属参与的C―H键切断的理论研究进展,并系统性提出了C―H键切断的相关模式,包括:C―H键对金属的氧化加成、碱协助的去质子化、σ-复分解、Friedel-Crafts型亲电芳香取代、α-或β-氢消除以及夺氢活化等。理论计算表明,当使用还原性较强的零价金属催化剂时,反应可按照氧化加成模式进行。当使用金属羧酸盐作为催化剂时,通常以协同金属化-去质子化机理模式实现C―H键切断。当使用阳离子金属催化剂,富电子芳烃比缺电子芳烃优先反应时,C―H键切断则会经历碱协助的内部亲电取代模式。σ-复分解是协同金属化-去质子化机理的另一种模式。如果亲电体对芳烃进行加成时,则可按照Friedel-Crafts型亲电芳香取代方式活化C―H键。α-或β-氢消除也是比较常见的活化C―H键模式。此外,夺氢活化可通过自由基过程实现C―H键活化。本文通过对过渡金属参与的C―H键活化模式的论述旨在为实验提供理论指导。 相似文献
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Kwanruthai Tadpetch Laksamee Jeanmard Vatcharin Rukachaisirikul 《Tetrahedron letters》2017,58(35):3453-3456
The first total synthesis of greensporone C, a cytotoxic 14-membered resorcylic acid lactone, has been accomplished via a longest linear sequence of 16 steps in 3.3% overall yield. The key features of the synthesis include Mitsunobu esterification and ring-closing metathesis to construct the macrocycle and establish the (E)-olefin geometry, respectively. Our synthesis also confirmed the absolute stereochemistry of the natural product. 相似文献
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The stereoselective synthesis of the C10–C24 fragment of (+)-cannabisativine has been achieved. The key steps involved in this strategy are the Sharpless asymmetric dihydroxylation, the diastereoselective allylation of an imine, and the ring closing metathesis (RCM). 相似文献
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The enantioselective synthesis of the natural products cladospolide B, cladospolide C, and iso-cladospolide B has been accomplished from tartaric acid. Key reactions in the synthetic sequence include the elaboration of a γ-hydroxy amide derived from tartaric acid via alkene cross metathesis, Yamaguchi lactonization, and ring closing metathesis. 相似文献
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Enantioselective Total Synthesis of Terreumols A and C from the Mushroom Tricholoma terreum 下载免费PDF全文
M. Sc. Alex Frichert Prof. Dr. Peter G. Jones Prof. Dr. Thomas Lindel 《Angewandte Chemie (International ed. in English)》2016,55(8):2916-2919
The cytotoxic meroterpenoids terreumol A and C from the grey knight mushroom Tricholoma terreum were synthesized for the first time. The key step of the enantioselective total synthesis of terreumol C is a ring‐closing metathesis to form a trisubstituted Z double bond embedded in the 10‐membered ring of the [8.4.0] bicycle. Interestingly, the presence of a free hydroxy group in the metathesis precursor prevents cyclization and favors cross metathesis. (?)‐Terreumol C was converted into (?)‐terreumol A by diastereoselective epoxidation. Starting from 2‐bromo‐3,5‐dimethoxybenzaldehyde, 14 steps with an overall yield of 23 % are needed for the synthesis of (?)‐terreumol A. X‐ray analysis of the benzoquinone analogue of terreumol A provides independent proof of the absolute configuration. 相似文献
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Jhillu S. Yadav Nimmakayala Mallikarjuna Reddy N. Venkateswar Rao Md. Ataur Rahman Attaluri R. Prasad 《Helvetica chimica acta》2012,95(2):227-234
A convergent and efficient total synthesis of stagonolide C ( 1 ), a phytotoxic metabolite, was achieved (Schemes 2 and 3) The synthesis exploited the high configuration control in the Prins cyclization along with alkene rearrangement and ring‐closing metathesis as key steps. 相似文献
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Punlop Kuntiyong Sunisa AkkarasamiyoNuanpan Piboonsrinakara Chitlada HemmaraPoramate Songthammawat 《Tetrahedron》2011,67(41):8034-8040
A formal synthesis of schulzeines B and C, marine natural products with inhibitory effect against α-glucosidase, has been achieved. The key reactions of the synthesis are N-acyliminium ion cyclization, Sharpless asymmetric dihydroxylation, olefin cross metathesis, and asymmetric allylboration. 相似文献
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Venkata Naresh Vema Y. Bharathi kumari Sridhar Musulla RamaKrishnam Raju Addada Srinivasa Rao Alapati 《Tetrahedron letters》2018,59(47):4165-4167
Greensporone C, a new 14-membered resorcylic acid lactone, has been synthesized from inexpensive and commercially available starting materials. This convergent synthesis utilizes Cross metathesis using the Grubbs Hoveyda catalyst, alkylation of 1,3-dithiane and Yamaguchi macrolactonization as key steps. 相似文献
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Sudina Purushotham Reddy Baggu Chinnababu Yenamandra Venkateswarlu 《Helvetica chimica acta》2014,97(7):999-1003
The first concise stereoselective total synthesis of diarylheptanoid rhoiptelol C ( 1 ) was achieved from readily available vanillin. The synthesis involves Keck's asymmetric allylation, olefin cross metathesis, and Sharpless asymmetric dihydroxylation reaction as key steps. 相似文献