共查询到20条相似文献,搜索用时 15 毫秒
1.
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
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Thomas Weskamp Wolfgang C. Schattenmann Michael Spiegler Wolfgang A. Herrmann 《Angewandte Chemie (International ed. in English)》1998,37(18):2490-2493
The different nature of carbene ligands is clearly demonstrated by the first ruthenium-based complexes 1 , which contain both alkylidene and N-heterocyclic carbene moieties. The latter exhibit a pronounced Lewis base behavior. Moreover, this difference forms the basis of the high catalytic activities of these compounds in olefin metathesis reactions. 相似文献
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S. Michael Hansen Martin A. O. Volland Frank Rominger Frank Eisentrger Peter Hofmann 《Angewandte Chemie (International ed. in English)》1999,38(9):1273-1276
Cationic RuII carbene complexes with tBu2PCH2PtBu2 (dtbpm) as a chelating ligand, which are accessible by chloride abstraction from neutral precursors [(κ2-dtbpm)Cl2Ru=CHR] with trimethylsilyl triflate, are established as highly efficient ring opening metathesis polymerization catalysts (see scheme). Solv=solvent. 相似文献
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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.
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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
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Gowravaram Sabitha Bhaskar Vangala S. Siva Sankara Reddy Jhillu S. Yadav 《Helvetica chimica acta》2010,93(2):329-338
Ring‐closing metathesis (RCM) and olefin cross‐metathesis (CM) reactions were used as the key steps for the synthesis of (+)‐cryptocaryalactone ( 1 ) and the first synthesis of the diastereoisomer 3 of (+)‐strictifolione, starting from the commercially available L ‐malic acid (=(2S)‐2‐hydroxybutanedioic acid). 相似文献
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The first total synthesis of sphingolipid (2S,3R,4E)‐N2‐octadecanoyl‐4‐tetradecasphingenine ( 1a ), a natural sphingolipid isolated from Bombycis Corpus 101A, and of its styryl analogue 1b was achieved in good overall yield (Schemes 1 and 2). The key step involved the installation with (E) stereoselectivity of a long lipophilic chain or phenyl group on allyl alcohol derivative 3 via a cross‐metathesis reaction (→ 5a or 5b ). The N‐Boc protected 3 was easily accessible from (S)‐Garner aldehyde. 相似文献
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Catalyst‐Controlled Stereoselective Olefin Metathesis as a Principal Strategy in Multistep Synthesis Design: A Concise Route to (+)‐Neopeltolide 下载免费PDF全文
Miao Yu Prof. Richard R. Schrock Prof. Amir H. Hoveyda 《Angewandte Chemie (International ed. in English)》2015,54(1):215-220
Molybdenum‐, tungsten‐, and ruthenium‐based complexes that control the stereochemical outcome of olefin metathesis reactions have been recently introduced. However, the complementary nature of these systems through their combined use in multistep complex molecule synthesis has not been illustrated. A concise diastereo‐ and enantioselective route that furnishes the anti‐proliferative natural product neopeltolide is now disclosed. Catalytic transformations are employed to address every stereochemical issue. Among the featured processes are an enantioselective ring‐opening/cross‐metathesis promoted by a Mo monoaryloxide pyrrolide (MAP) complex and a macrocyclic ring‐closing metathesis that affords a trisubstituted alkene and is catalyzed by a Mo bis(aryloxide) species. Furthermore, Z‐selective cross‐metathesis reactions, facilitated by Mo and Ru complexes, have been employed in the stereoselective synthesis of the acyclic dienyl moiety of the target molecule. 相似文献
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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
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Dr. Rudy Lhermet Prof. Dr. Alois Fürstner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(41):13188-13193
Terminal acetylenes are amongst the most problematic substrates for alkyne metathesis because they tend to undergo rapid polymerization on contact with a metal alkylidyne. The molybdenum complex 3 endowed with triphenylsilanolate ligands, however, is capable of inducing surprisingly effective cross‐metathesis reactions of terminal alkyl acetylenes with propynyl(trimethyl)silane to give products of type R1?C?CSiMe . This unconventional way of introducing a silyl substituent onto an alkyne terminus complements the conventional tactics of deprotonation/silylation and excels as an orthogonal way of alkyne protecting group chemistry for substrates bearing base‐sensitive functionalities. Moreover, it is shown that even terminal aryl acetylenes can be cross‐metathesized with internal alkyne partners. These unprecedented transformations are compatible with various functional groups. The need to suppress acetylene formation, which seems to be a particularly effective catalyst poison, is also discussed. 相似文献
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Dirk Schoeps Dipl.‐Ing. Kristian Buhr Dipl.‐Ing. Marga Dijkstra Dr. Katrin Ebert Dr. Herbert Plenio Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(12):2960-2965
Retained : An N‐heterocyclic carbene with eight cyclohexyl groups (see figure) provides increased electron density for a highly active olefin metathesis catalyst as well as sufficient steric bulk to allow the efficient separation of such a complex from the organic products in the solvent‐resistant nanofiltration.
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Michaël Raymond Michael Holtz‐Mulholland Prof. Shawn K. Collins 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(40):12763-12767
Macrocyclic olefin metathesis has seen advances in the areas of stereochemistry, chemoselectivity, and catalyst stability, but strategies aimed at controlling dilution effects in macrocyclizations are rare. Herein, a protocol to promote macrocyclic olefin metathesis, one of the most common synthetic tools used to prepare macrocycles, at relatively high concentrations (up to 60 mM ) is described by exploitation of a phase‐separation strategy. A variety of macrocyclic skeletons could be prepared having either different alkyl, aryl, or amino acids spacers. 相似文献
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Catalytic,Enantioselective Synthesis of 1,2‐anti‐Diols by Asymmetric Ring‐Opening/Cross‐Metathesis 下载免费PDF全文
Dr. John Hartung Prof. Robert H. Grubbs 《Angewandte Chemie (International ed. in English)》2014,53(15):3885-3888
An enantioselective method for the synthesis of 1,2‐anti‐diols has been developed. A cyclometalated chiral‐at‐ruthenium complex catalyzes the asymmetric ring‐opening/cross‐metathesis of dioxygenated cyclobutenes, thus resulting in functionally rich synthetic building blocks. Syntheses of the insect pheromone (+)‐endo‐brevicomin and monosaccharide ribose demonstrate the synthetic utility of the 1,2‐anti‐diol fragments generated in the title reaction. 相似文献
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Erin M. Leitao Stuart R. Dubberley Dr. Warren E. Piers Prof. Qiao Wu Dr. Robert McDonald Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(36):11565-11572
The four‐coordinate ruthenium phosphonium alkylidenes 1‐Cy and 1‐iPr , differing in the substituent on the phosphorus center, were observed to decompose thermally in the presence of 1,1‐dichloroethylene to produce [H3CPR3][Cl]. The major ruthenium‐containing product was a trichloro‐bridged ruthenium dimer that incorporates the elements of the 1,1‐dichloroethylene as a dichlorocarbene ligand and a styrenic vinyl group on the supporting NHC ligand. Spectroscopic, kinetic, and deuterium‐labeling experiments probed the mechanism of this process, which involves a rate‐limiting C–H activation of an NHC mesityl ortho methyl group. These studies provide insight into intrinsic decomposition processes of active Grubbs type olefin metathesis catalysts, pointing the way to new catalyst design directions. 相似文献
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A series of ruthenium carbene catalysts containing 2‐sulfidophenolate bidentate ligand with an ortho‐substituent next to the oxygen atom were synthesized. The molecular structure of ruthenium carbene complex containing 2‐isopropyl‐6‐sulfidophenolate ligand was confirmed through single crystal X‐ray diffraction. An oxygen atom can be found in the opposite position of the N‐heterocyclic carbene (NHC) based on the steric hindrance and strong trans‐effects of the NHC ligand. The ruthenium carbene catalyst can catalyze ring‐opening metathesis polymerization (ROMP) reaction of norbornene with high activity and Z‐selectivity and cross metathesis (CM) reactions of terminal alkenes with (Z)‐but‐2‐ene‐1,4‐diol to give Z‐olefin products (Z/E ratios, 70:30–89:11) in low yields (13%–38%). When AlCl3 was added into the CM reactions, yields (51%–88%) were considerably improved and process becomes highly selective for E‐olefin products (E/Z ratios, 79:21–96:4). Similar to other ruthenium carbene catalysts, these new complexes can tolerate different functional groups. 相似文献