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1.
Switching on the Metathesis Activity of Re Oxo Alkylidene Surface Sites through a Tailor‐Made Silica–Alumina Support
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Maxence Valla David Stadler Dr. Victor Mougel Prof. Dr. Christophe Copéret 《Angewandte Chemie (International ed. in English)》2016,55(3):1124-1127
Re oxo alkylidene surface species are putative active sites in classical heterogeneous Re‐based alkene‐metathesis catalysts. However, the lack of evidence for such species questions their existence and/or relevance as reaction intermediates. Using Re(O)(=CH‐CH=CPh2)(OtBuF6)3(THF), the corresponding well‐defined Re oxo alkylidene surface species can be generated on both silica and silica–alumina supports. While inactive on the silica support, it displays very good activity, even for functionalized olefins, on the silica–alumina support. 相似文献
2.
Certain dienynes give cyclorearrangement by tandem cyclopropanation/ring-closing alkene metathesis, triggered by either a ruthenium carbene or noncarbene ruthenium(II) precatalyst. The process represents a variation of enyne metathesis where presumed cyclopropyl carbene intermediates undergo a consecutive ring-closing metathesis. A mechanistic proposal is offered, and sequential use of catalysts provided a tandem ring-closing enyne/alkene metathesis product. 相似文献
3.
Copéret C 《Dalton transactions (Cambridge, England : 2003)》2007,(47):5498-5504
This review outlines the molecular insights provided by surface organometallic chemistry in the area of alkene metathesis, and particularly in the development and the understanding of heterogeneous catalysts. 相似文献
4.
Miguel ngel Rivero‐Crespo María Tejeda‐Serrano Horacio Prez‐Snchez Jos Pedro Cern‐Carrasco Antonio Leyva‐Prez 《Angewandte Chemie (International ed. in English)》2020,59(10):3846-3849
The carbonyl–olefin metathesis reaction has experienced significant advances in the last seven years with new catalysts and reaction protocols. However, most of these procedures involve soluble catalysts for intramolecular reactions in batch. Herein, we show that recoverable, inexpensive, easy to handle, non‐toxic, and widely available simple solid acids, such as the aluminosilicate montmorillonite, can catalyze the intermolecular carbonyl–olefin metathesis of aromatic ketones and aldehydes with vinyl ethers in‐flow, to give alkenes with complete trans stereoselectivity on multi‐gram scale and high yields. Experimental and computational data support a mechanism based on a carbocation‐induced Grob fragmentation. These results open the way for the industrial implementation of carbonyl–olefin metathesis over solid catalysts in continuous mode, which is still the origin and main application of the parent alkene–alkene cross‐metathesis. 相似文献
5.
Strained nitroso Diels–Alder bicyclo[2.2.1] or [2.2.2] adducts functionalized with alkene side chains of diverse length undergo a ring‐rearrangement metathesis process with external alkenes and Grubbs II or Hoveyda–Grubbs II ruthenium catalysts, under microwave irradiation or classical heating, to deliver cis‐fused bicycles of various ring sizes, which contain a N? O bond. These scaffolds are of synthetic relevance for the generation of molecular diversity and to the total synthesis of alkaloids. The observation of unexpected reactions, such as epimerization or one‐carbon homologation of the alkene side chain, is also reported. 相似文献
6.
Vaneet Saini Dr. Benjamin J. Stokes Prof. Matthew S. Sigman 《Angewandte Chemie (International ed. in English)》2013,52(43):11206-11220
Ethylene, the simplest alkene, is the most abundantly synthesized organic molecule by volume. It is readily incorporated into transition‐metal‐catalyzed carbon–carbon bond‐forming reactions through migratory insertions into alkylmetal intermediates. Because of its D2h symmetry, only one insertion outcome is possible. This limits byproduct formation and greatly simplifies analysis. As described within this Minireview, many carbon–carbon bond‐forming reactions incorporate a molecule (or more) of ethylene at ambient pressure and temperature. In many cases, a useful substituted alkene is incorporated into the product. 相似文献
7.
Yu Xie Ye Yuan Bibimaryam Mousavi Yuan Cai Cheng Kai Yin Lu Mehman Yusubov Francis Verpoort 《应用有机金属化学》2015,29(9):573-579
Olefin metathesis is a transition metal‐mediated transformation that rearranges the carbon atoms of the carbon–carbon double bond of olefins. This reaction has become one of the most important and powerful reactions. Therefore development of new, well‐defined, highly active and selective catalysts is very desirable and a valuable goal. This mini‐review mainly introduces the development of ruthenium catalysts in olefin metathesis highlighting oxygen‐chelated indenylidene ruthenium catalysts. Applying an alkoxyl group on the indenylidene ligand fragment can generate the Ru ? O chelating bond. Additionally, various modifications of the ligand as well as the catalytic activity for ring‐closing metathesis reaction and selectivity of cross metathesis reaction are overviewed. Finally, the perspectives on the development of new catalysts are summarized. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
8.
Blanc F Thivolle-Cazat J Basset JM Copéret C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(29):9030-9037
Alkane metathesis can be performed by using well-defined silica-supported alkene metathesis catalyst precursors as long as the coordination sphere of the metal centre contains both alkyl and alkylidene groups, such as in [([triple chemical bond]SiO)Mo([triple chemical bond]NAr)(=CHtBu)(CH2tBu)]. This system transforms mainly linear alkanes, from propane to hexane, into their lower and higher homologues. Mechanistic studies clearly show that alkene metathesis is a key step of this reaction and also suggest that this system is a single-site single-component system, namely, alkenes are formed and transformed on one site, which is in contrast to that observed with a mixture of catalysts. 相似文献
9.
Cationic Silica‐Supported N‐Heterocyclic Carbene Tungsten Oxo Alkylidene Sites: Highly Active and Stable Catalysts for Olefin Metathesis
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Margherita Pucino Dr. Victor Mougel Roman Schowner Dr. Alexey Fedorov Prof. Dr. Michael R. Buchmeiser Prof. Dr. Christophe Copéret 《Angewandte Chemie (International ed. in English)》2016,55(13):4300-4302
Designing supported alkene metathesis catalysts with high activity and stability is still a challenge, despite significant advances in the last years. Described herein is the combination of strong σ‐donating N‐heterocyclic carbene ligands with weak σ‐donating surface silanolates and cationic tungsten sites leading to highly active and stable alkene metathesis catalysts. These well‐defined silica‐supported catalysts, [(≡SiO)W(=O)(=CHCMe2Ph)(IMes)(OTf)] and [(≡SiO)W(=O)(=CHCMe2Ph)(IMes)+][B(ArF)4?] [IMes=1,3‐bis(2,4,6‐trimethylphenyl)‐imidazol‐2‐ylidene, B(ArF)4=B(3,5‐(CF3)2C6H3)4] catalyze alkene metathesis, and the cationic species display unprecedented activity for a broad range of substrates, especially for terminal olefins with turnover numbers above 1.2 million for propene. 相似文献
10.
Tristan Delcaillau Alessandro Bismuto Zhong Lian Bill Morandi 《Angewandte Chemie (International ed. in English)》2020,59(5):2110-2114
A nickel‐catalyzed aryl thioether metathesis has been developed to access high‐value thioethers. 1,2‐Bis(dicyclohexylphosphino)ethane (dcype) is essential to promote this highly functional‐group‐tolerant reaction. Furthermore, synthetically challenging macrocycles could be obtained in good yield in an unusual example of ring‐closing metathesis that does not involve alkene bonds. In‐depth organometallic studies support a reversible Ni0/NiII pathway to product formation. Overall, this work not only provides a more sustainable alternative to previous catalytic systems based on Pd, but also presents new applications and mechanistic information that are highly relevant to the further development and application of unusual single‐bond metathesis reactions. 相似文献
11.
《Angewandte Chemie (International ed. in English)》2017,56(19):5170-5181
Unique features of earth‐abundant transition‐metal catalysts are reviewed in the context of catalytic carbon–carbon bond‐forming reactions. Aryl‐substituted bis(imino)pyridine iron and cobalt dihalide compounds, when activated with alkyl aluminum reagents, form highly active catalysts for the polymerization of ethylene. Open‐shell iron and cobalt alkyl complexes have been synthesized that serve as single‐component olefin polymerization catalysts. Reduced bis(imino)pyridine iron and cobalt dinitrogen compounds have also been discovered that promote the unique [2+2] cycloaddition of unactivated terminal alkenes. Studies of the electronic structure support open‐shell intermediates, a deviation from traditional strong‐field organometallic compounds that promote catalytic C−C bond formation. 相似文献
12.
13.
Roman Schowner Iris Elser Mathis Benedikter Mohasin Momin Wolfgang Frey Tanja Schneck Laura Sthr Michael R. Buchmeiser 《Angewandte Chemie (International ed. in English)》2020,59(2):951-958
The origin of hydroxyl group tolerance in neutral and especially cationic molybdenum imido alkylidene N‐heterocyclic carbene (NHC) complexes has been investigated. A wide range of catalysts was prepared and tested. Most cationic complexes can be handled in air without difficulty and display an unprecedented stability towards water and alcohols. NHC complexes were successfully used with substrates containing the hydroxyl functionality in acyclic diene metathesis polymerization, homo‐, cross and ring‐opening cross metathesis reactions. The catalysts remain active even in 2‐PrOH and are applicable in ring‐opening metathesis polymerization and alkene homometathesis using alcohols as solvent. The use of weakly basic bidentate, hemilabile anionic ligands such as triflate or pentafluorobenzoate and weakly basic aromatic imido ligands in combination with a sterically demanding 1,3‐dimesitylimidazol‐2‐ylidene NHC ligand was found essential for reactive and yet robust catalysts. 相似文献
14.
Dr. Tetsu Tsubogo Takanori Ishiwata Prof. Dr. Shū Kobayashi 《Angewandte Chemie (International ed. in English)》2013,52(26):6590-6604
Catalytic asymmetric carbon–carbon bond‐forming reactions provide one of the most efficient ways to synthesize optically active compounds, and, accordingly, many chiral catalysts for these reactions have been developed in the past two decades. However, the efficiency of the catalysts in terms of turnover number (TON) is often lower than that of some other reactions, such as asymmetric hydrogenation, and this has been one of the obstacles for industrial applications. Although there are some difficulties in increasing the efficiency, the issues might be solved by using continuous flow in the presence of chiral heterogeneous catalysts. Indeed, continuous‐flow systems have several advantages over conventional batch systems. Here we summarize the recent progress in asymmetric C? C bond‐forming reactions under continuous‐flow conditions with chiral heterogeneous catalysts. 相似文献
15.
LeoA. Paquette Kallol Basu JamesC. Eppich JohnE. Hofferberth 《Helvetica chimica acta》2002,85(10):3033-3051
The (alkylidene) ruthenium complexes 1 and 2b were examined as catalysts for the ring‐closing metathesis of the homologous series of ene‐dienes 16 to ascertain the extent to which a divergence in product distribution would be observed. In each case, the levels of cyclic alkene and conjugated diene were determined (see Table 1). Double bond geometric assignments were made on the basis of vinyl proton 1H‐NMR chemical shifts and coupling constants. MM3 Calculations were undertaken to gauge the levels of steric strain in end products of varying ring size. The global ensemble of facts, including key control experiments, demonstrate the striking differences between 1 and 2b . Finally, the steric energies are seen not to correlate with the product distributions, most probably due to the distinctive reactivity patterns of the metathesis reagents. 相似文献
16.
Abbenhuis HC 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(1):25-32
Metal-containing silsesquioxane derivatives provide new catalysts with both homogeneous and heterogeneous applicability. The steric and electronic properties of silsesquioxane silanolate ligands render metal centers more Lewis acidic than conventional alkoxide or siloxide ligands do. This concept has been exploited in newly developed catalysts for alkene metathesis, polymerization, epoxidation, and Diels-Alder reactions of enones. Other applications are envisioned in the near future. 相似文献
17.
Dr. Miguel Ángel Rivero-Crespo María Tejeda-Serrano Dr. Horacio Pérez-Sánchez Dr. José Pedro Cerón-Carrasco Dr. Antonio Leyva-Pérez 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(10):3874-3877
The carbonyl–olefin metathesis reaction has experienced significant advances in the last seven years with new catalysts and reaction protocols. However, most of these procedures involve soluble catalysts for intramolecular reactions in batch. Herein, we show that recoverable, inexpensive, easy to handle, non-toxic, and widely available simple solid acids, such as the aluminosilicate montmorillonite, can catalyze the intermolecular carbonyl–olefin metathesis of aromatic ketones and aldehydes with vinyl ethers in-flow, to give alkenes with complete trans stereoselectivity on multi-gram scale and high yields. Experimental and computational data support a mechanism based on a carbocation-induced Grob fragmentation. These results open the way for the industrial implementation of carbonyl–olefin metathesis over solid catalysts in continuous mode, which is still the origin and main application of the parent alkene–alkene cross-metathesis. 相似文献
18.
Dr. José Cabrera Dr. Robin Padilla Dr. Miriam Bru Dr. Ronald Lindner Dr. Takeharu Kageyama Dr. Kristina Wilckens Dr. Shawna L. Balof Dr. Hans‐Jörg Schanz Dr. Richard Dehn Dr. J. Henrique Teles Dr. Stephan Deuerlein Dr. Kevin Müller Dr. Frank Rominger Dr. Michael Limbach 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(46):14717-14724
A set of heterogenized olefin‐metathesis catalysts, which consisted of Ru complexes with the H2ITap ligand (1,3‐bis(2′,6′‐dimethyl‐4′dimethyl aminophenyl)‐4,5‐dihydroimidazol‐2‐ylidene) that had been adsorbed onto a silica support, has been prepared. These complexes showed strong binding to the solid support without the need for tethering groups on the complex or functionalized silica. The catalysts were tested in the ring‐opening–ring‐closing‐metathesis (RO‐RCM) of cyclooctene (COE) and the self‐metathesis of methyl oleate under continuous‐flow conditions. The best complexes showed a TON>4000, which surpasses the previously reported materials that were either based on the Grubbs–Hoveyda II complex on silica or on the classical heterogeneous Re2O7/B2O3 catalyst. 相似文献
19.
Ring‐rearrangement metathesis (RRM) refers to the combination of several metathesis transformations into a domino process, in which an endocyclic double bond of a cycloolefin reacts with an exocyclic alkene. RRM has proven to be a powerful method for the rapid construction of complex structures. The extension of the basic ring‐opening–ring‐closing metathesis process by further metathesis steps as well as an examination of the driving forces, limits, scope, recent advantages, and future perspectives of these domino sequences is presented with various examples, thus reflecting the high efficiency and utility of RRM in organic synthesis. 相似文献
20.
Timothy P. Moneypenny II Huiying Liu Anna Yang Ian D. Robertson Jeffrey S. Moore 《Journal of polymer science. Part A, Polymer chemistry》2017,55(18):2935-2948
Alkene metathesis has proven to be a powerful method for carbon carbon bond formation, particularly in the field of polymer and materials science. The availability of various tailor-made catalysts not only enables the synthesis of well-defined polymers but facilitates the development of functional, stimuli–responsive materials. This highlight, dedicated to Professor Robert Grubbs on his 75th birthday, focuses on the various research efforts in our group utilizing both alkene and alkyne metatheses and the interesting materials derived from them. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2935–2948 相似文献