共查询到20条相似文献,搜索用时 15 毫秒
1.
A stereoselective total synthesis of leiocarpin C ( 2 ) and (+)‐Goniodiol ( 1 ) by applying olefin cross‐metathesis and substrate directed dihydroxylation as the key steps is reported (Scheme 3). 相似文献
2.
Tzu‐Wei Tsai Eng‐Chi Wang Sie‐Rong Li Yung‐Hua Chen Yu‐Li Lin You‐Feng Wang Keng‐Shiang Huang 《中国化学会会志》2004,51(6):1307-1318
Based on Claisen rearrangement, the double bond isomerization of O‐allyl function together with the formation of O‐vinyl function in one pot, and ring‐closing metathesis (RCM), various phenols were transformed into various benzofurans in good yields. 相似文献
3.
A stereoselective synthesis of (5S,6S)‐6‐[(2S,5S,7R,8E,10E)‐5‐(benzyloxy)‐7‐{[(tert‐butyl)dimethylsilyl]oxy}‐11‐phenylundeca‐8,10‐dien‐2‐yl]‐5‐ethyl‐5,6‐dihydro‐2H‐pyran‐2‐one (=(+)‐9‐O‐benzyl‐11‐O‐[(tert‐butyl)dimethylsilyl]bitungolide F) is reported. The strategy involves Gilman reaction, olefin cross‐metathesis, and Horner? Wadsworth? Emmons olefination as key steps. 相似文献
4.
Jui‐Chi Tsai Sie‐Rong Li Liang‐Yeu Chen Po‐Yuan Chen Jia‐Ying Joung Chung‐Jung Shu Yu‐Fuan Lo Chun‐Nan Lin Eng‐Chi Wang 《中国化学会会志》2008,55(6):1317-1321
In this paper, the synthesis of 3‐aryl‐2,5‐dihydro‐1‐benzoxepines is described. While the reaction was started from phenol and based on the sequential reactions such as Claisen rearrangement, O‐alkylation, Wittig reaction, and ring‐closing metathesis (RCM), a series of new 3‐aryl‐1‐benzoxepines were prepared in good overall yields. 相似文献
5.
A pentamodule assembly approach has been established for total synthesis of the naturally occurring (–)‐palmyrolide A and (+)‐5,7‐epi‐palmyrolide A. By using the racemic tert‐butyl carbinol‐containing alkyl iodide, the two diastereoisomeric macrolides could be obtained from the same sequence of reactions, demonstrating the flexibility of the multimodule assembly strategy for diverted total synthesis. 相似文献
6.
Ruifang Guan Chuanjian Zhou Shengyu Feng David J. Berg Stephen R. Stobart 《中国化学会会志》2005,52(1):113-118
Grubbs' catalyst was used to prepare a series of carbosilane dendrimers with silacyclopentene peripheral groups, suitable for further elaboration to functional dendrimers. The efficiency of the ring closing metathesis reaction was found to be strongly dependent on the reaction temperature and the amount of catalyst used, as shown by 1H NMR monitoring. 相似文献
7.
Chang‐Ching Lin Thangaiah Subramanian Tzu‐Sui Hsu Gang‐Ting Fan Chun‐Cheng Lin 《中国化学会会志》2001,48(1):55-58
Several C‐butenyl linked disaccharides were pre pared in high yields by olefin cross‐metathesis. 相似文献
8.
《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(1):51-62
Asymmetric oxyallylation reactions and ring‐closing metathesis have been used to synthesize compound 3 , a key advanced intermediate used in the total synthesis of eleutherobin reported by Danishefsky and co‐workers. The aldehyde 6 , which is readily prepared from commercially available R‐(?)‐carvone in six steps in 30 % overall yield on multigram quantities, was converted into the diene 5 utilizing two stereoselective titanium‐mediated Hafner–Duthaler oxyallylation reactions. The reactions gave the desired products ( 8 and 12 ) in high yields (73 and 83 %, respectively) as single diastereoisomers, with the allylic alcohol already protected as the p‐methoxyphenyl (PMP) ether, which previous work has demonstrated actually aids ring‐closing metathesis compared to other protective groups and the corresponding free alcohol. Cyclization under forcing conditions, using Grubbs' second‐generation catalyst 13 , gave the ten‐membered carbocycle (E)‐ 14 in 64 % yield. This result is in sharp contrast to similar, but less functionalized, dienes, which have all undergone cyclization to give the Z stereoisomers exclusively. A detailed investigation of this unusual cyclization stereochemistry by computational methods has shown that the E isomer of the ten‐membered carbocycle is indeed less thermodynamically stable than the corresponding Z isomer. In fact, the selectivity is believed to be due to the dense functionality around the ruthenacyclobutane intermediate that favors the trans‐ruthenacycle, which ultimately leads to the less stable E isomer of the ten‐membered carbocycle under kinetic control. During the final synthetic manipulations the double bond of enedione (E)‐ 16 isomerized to the more thermodynamically stable enedione (Z)‐ 4 , giving access to the advanced key‐intermediate 3 , which was spectroscopically and analytically identical to the data reported by Danishefsky and co‐workers, and thereby completing the formal synthesis of eleutherobin. 相似文献
9.
10.
Enantioselective Synthesis of Macrocyclic Heterobiaryl Derivatives of Molecular Asymmetry by Molybdenum‐Catalyzed Asymmetric Ring‐Closing Metathesis 下载免费PDF全文
Yoichi Okayama Satoru Tsuji Yuka Toyomori Prof. Dr. Atsunori Mori Dr. Sachie Arae Dr. Wei‐Yi Wu Prof. Dr. Tamotsu Takahashi Prof. Dr. Masamichi Ogasawara 《Angewandte Chemie (International ed. in English)》2015,54(16):4927-4931
Winding vine‐shaped molecular asymmetry is induced by enantioselective ring‐closing metathesis with a chiral molybdenum catalyst. The reaction proceeds under mild conditions through an E‐selective ring‐closing metathesis leading to macrocyclic bisazoles with enantioselectivities of up to 96 % ee. 相似文献
11.
Kazuhiro Yoshida Fumihiro Kawagoe Noriyuki Iwadate Hidetoshi Takahashi Tsuneo Imamoto 《化学:亚洲杂志》2006,1(4):611-613
Benzene derivatives were synthesized in excellent yield from 1,4,7‐trien‐3‐ols by tandem ruthenium‐catalyzed ring‐closing olefin metathesis (RCM)/dehydration. The method was extended to the tandem RCM/oxidation process to obtain phenol and aniline derivatives. This method displays many advantages over aromatic‐substitution‐based classical routes. 相似文献
12.
Divergent Dendrimer Synthesis via the Passerini Three‐Component Reaction and Olefin Cross‐Metathesis
Oliver Kreye Dennis Kugele Lorenz Faust Michael A. R. Meier 《Macromolecular rapid communications》2014,35(3):317-322
The combination of the Passerini reaction and olefin cross‐metathesis is shown to be a very useful approach for the divergent synthesis of dendrimers. Castor oil‐derived platform chemicals, such as 10‐undecenoic acid and 10‐undecenal, are reacted in a Passerini reaction with an unsaturated isocyanide to obtain a core unit having three terminal double bonds. Subsequent olefin cross‐metathesis with tert‐butyl acrylate, followed by hydrogenation of the double bonds and hydrolysis of the tert‐butyl ester, leads to an active core unit bearing three carboxylic acid groups as reactive sites. Iterative steps of the Passerini reaction with 10‐undecenal and 10‐isocyanodec‐1‐ene for branching, and olefin cross‐metathesis with tert‐butyl acrylate, followed by hydrogenation and hydrolysis allow the synthesis of a third‐generation dendrimer. All steps of the synthesis are carefully characterized by NMR, GPC, MS, and IR.
13.
A simple and efficient route for the synthesis of oxepine‐, oxocine‐, oxepinone‐, and dioxocine‐angularly annulated flavone skeletons has been developed. The combined Claisen rearrangement and the ring‐closing metathesis are used as key steps for the construction of C7/C8–C6–C6 tricyclic core structures. 相似文献
14.
Lina Ma Wenjuan Li Hui Xi Xiaohui Bai Enlu Ma Dr. Xiaoyu Yan Prof. Dr. Zhiping Li 《Angewandte Chemie (International ed. in English)》2016,55(35):10410-10413
Exploiting catalytic carbonyl–olefin metathesis is an ongoing challenge in organic synthesis. Reported herein is an FeCl3‐catalyzed ring‐closing carbonyl–olefin metathesis. The protocol allows access to a range of carbo‐/heterocyclic alkenes with good efficiency and excellent trans diastereoselectivity. The methodology presents one of the rare examples of catalytic ring‐closing carbonyl–olefin metathesis. This process is proposed to take place by FeCl3‐catalyzed oxetane formation followed by retro‐ring‐opening to deliver metathesis products. 相似文献
15.
Synthesis of Carbazole Alkaloids by Ring‐Closing Metathesis and Ring Rearrangement–Aromatization 下载免费PDF全文
Joydeb Das Prof. Dr. Jyotirmayee Dash 《Angewandte Chemie (International ed. in English)》2015,54(52):15831-15835
Aprocess for the assembly of carbazole alkaloids has been developed on the basis of ring‐closing metathesis (RCM) and ringrearrangement–aromatization (RRA) as the key steps. This method is based on allyl Grignard addition to isatin derivatives to provide smooth access to 2,2‐diallyl 3‐oxindole derivatives through a 1,2‐allyl shift. The diallyl derivatives were used as RCM precursors to afford a novel class of spirocyclopentene‐3‐oxindole derivatives, which underwent a novel RRA reaction to afford carbazole derivatives. The synthetic sequence to carbazoles was shortened by combining the RCM and RRA steps in an orthogonal tandem catalytic process. The utility of this methodology was further demonstrated by the straightforward synthesis of carbazole alkaloids, including amukonal derivative, girinimbilol, heptaphylline, and bis(2‐hydroxy‐3‐methylcarbazole). 相似文献
16.
Synergy in synthesis : Strategic consideration of metathesis and Suzuki–Miyaura (SM) cross‐coupling for C? C bond‐formation processes has opened up new and “green” synthetic routes to various complex targets. The use of this synergistic combination for the synthesis of supramolecular ligands, polyaromatic compounds, and complex natural products is covered in this Focus Review.
17.
The stereoselective formal synthesis of (?)‐cyclaradine from the inexpensively available starting material L ‐glutamic acid is described, using Eschenmoser's reagent, and applying Luche reduction, Grignard reaction, and ring closing metathesis (RCM) as the key steps. 相似文献
18.
Chin‐Yang Yu James W. Kingsley David G. Lidzey Michael L. Turner 《Macromolecular rapid communications》2009,30(22):1889-1892
Fully conjugated block copolymers containing 1,4‐ and 1,3‐phenylenevinylene repeating units can be prepared by the sequential ring opening metathesis polymerization of strained cyclophanedienes, initiated by ruthenium carbene complexes (Grubbs metathesis catalysts). The molecular weight of the constituent blocks can be tightly controlled by changing the catalyst to monomer ratio and the volume fraction of the block copolymers independently tailored by the ratio of the monomers employed. Extensive phase separation between the constituent blocks is observed in thin films of these polymers by atomic force microscopy and efficient energy transfer between blocks containing 1,4‐ and 1,3‐phenylenevinylene units can be seen in the photoluminescence of these materials.
19.
20.
Lucas Montero de Espinosa Kristian Kempe Ulrich S. Schubert Richard Hoogenboom Michael A. R. Meier 《Macromolecular rapid communications》2012,33(23):2023-2028
Olefin cross‐metathesis is introduced as a versatile polymer side‐chain modification technique. The reaction of a poly(2‐oxazoline) featuring terminal double bonds in the side chains with a variety of functional acrylates has been successfully performed in the presence of Hoveyda–Grubbs second‐generation catalyst. Self‐metathesis, which would lead to polymer–polymer coupling, can be avoided by using an excess of the cross‐metathesis partner and a catalyst loading of 5 mol%. The results suggest that bulky acrylates reduce chain–chain coupling due to self‐metathesis. Moreover, different functional groups such as alkyl chains, hydroxyl, and allyl acetate groups, as well as an oligomeric poly(ethylene glycol) and a perfluorinated alkyl chain have been grafted with quantitative conversions. 相似文献