- Regarding the mechanism of olefin metathesis with sol-gel-supported Ru-based complexes bearing a bidentate carbene ligand. Spectroscopic evidence for return of the propagating Ru carbene
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Two isotopically and structurally labeled Ru-based carbenes (2-d 4 and 13) have been prepared and attached to the surface of monolithic sol-gel glass. The resulting glass-supported complexes (18-d n and 19) exhibit significant catalytic activity in promoting olefin metathesis reactions and provide products of high purity. Through analysis of the derivatized glass pellets used in a sequence of catalytic ring-closing metathesis reactions mediated by various supported Ru carbenes, it is demonstrated that free Ru carbene intermediates in solution can be scavenged by support-bound styrene ether ligands prior to the onset of competing transition metal decomposition. The observations detailed herein provide rigorous evidence that the initially proposed release/return mechanism is, at least partially, operative. The present investigations shed light on a critical aspect of the mechanism of an important class of Ru-based metathesis complexes (those bearing a bidentate styrene ether ligand).
- Kingsbury, Jason S.,Hoveyda, Amir H.
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Read Online
- Synthesis of pentafluorobenzene-based NHC adducts and their catalytic activity in the microwave-assisted reactions of aldehydes
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N-Heterocyclic carbenes (NHCs) have been widely used in organometallic chemistry as ligands, as well as standalone organocatalysts in various reactions, mostly using aromatic aldehydes as substrates. We have previously demonstrated the efficiency of azolium-2-carboxylate zwitterions in the hydroxymethylation of aldehydes, especially aliphatic aldehydes, under microwave irradiation. In the present work, we report a series of pentafluorobenzene-based NHC adducts and their efficiency in the hydroxymethylation and self-condensation of aliphatic and aromatic aldehydes using microwave irradiation. The free carbenes are released under the reaction conditions and 1,3-dimesityl-2-(perfluorophenyl)imidazolidine and 1,3-bis(2,6-dimethylphenyl)-2-(perfluorophenyl)imidazolidine proved to be the most potent precatalysts.
- Papadaki, Evanthia,Magrioti, Victoria
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supporting information
(2019/12/24)
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- BIS-IMINE TITANIUM COMPLEX, CATALYTIC SYSTEM COMPRISING SAID BIS-IMINE TITANIUM COMPLEX AND PROCESS FOR THE (CO)POLYMERIZATION OF CONJUGATED DIENES
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Bis-imine titanium complex having general formula (I): wherein: R1 and R2, mutually identical or different, represent a hydrogen atom; or are selected from linear or branched, optionally halogenated, C1-C20 alky
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Page/Page column 31; 32
(2019/04/26)
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- Carboxylate ionic liquid as well as preparation method and application thereof
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The invention provides carboxylate ionic liquid as well as a preparation method and application thereof. According to the carboxylate ionic liquid provided by the invention, an imidazole group or a pyridine group is introduced into the cationic part of the carboxylate ionic liquid and a carboxylic acid group is introduced into the anionic part of the carboxylate ionic liquid; and the ionic liquidcatalyst provided by the invention is simple and convenient in synthesis route, high in yield and easy to recover. Anion carboxylate radical in the carboxylate ionic liquid provided by the invention serves as an active site, so that synthesis of diol can be realized through high-efficiency and high-selectivity catalysis of hydration reaction of epoxy compounds under the condition of not adding other catalysts.
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Paragraph 0090-0097
(2019/10/23)
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- Steric demands in the formation of heteroleptic Cu(I) complexes with α-diimines and triphenylphosphine
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The synthesis and the study of the molecular structure of a series of heteroleptic copper(I) compounds with triphenylphosphine and α-diimines presenting a varying degree of bulk at their chelating cite is reported. The most sterically crowded diimine acts as a monodentate ligand towards copper(I) promoting bridging of the halogen atom present in the metal coordination sphere and formation of a dimer. Evidence for this behavior is obtained from the electronic spectra and semiempirical quantum chemical calculations with MOPAC. Steric demands in all the studied compounds preclude coordination of silver(I) under similar reaction conditions.
- Tseriotou, Eleni,Tzimopoulos, Dimitris,Hatzidimitriou, Antonis,Akrivos, Pericles
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p. 152 - 157
(2018/07/29)
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- Synthesis, Antitumor Activity, and Docking Study of 1,3-Disubstituted Imidazolium Derivatives
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A series of 1,3-disubstituted imidazolium salts were synthesized through a convenient synthetic approach based on the reaction of 1,4-diazabuta-1,3-dienes with HClO4. Their antitumor activity was evaluated in vitro against a number of human cancer cells. 1,3-Bis[(3,5-bis(trifluoromethyl)phenyl]imidazolium perchlorate turned out to be the most active against A549 and MCF-7 cancer cell lines with IC50 values of 5.24 and 4.21 μM, respectively. The results of structure–activity relationship study indicated that substituents on the imidazole derivatives play an important role in their cytotoxic activities. Finally, molecular docking of some tested compounds was carried out in order to investigate their binding pattern with the CDK2.
- Fan,Zhong,Yan
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p. 3023 - 3028
(2018/02/21)
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- New fluorinated catalysts for olefin metathesis
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New olefin metathesis catalysts, analogues of Grubbs II ones, bearing hexafluoroisopropylmethoxy groups in NHC ligand, provide high conversions in model ring closing metathesis of diallylmalonate and cross metathesis of allylbenzene with 1,3-diacetoxybut-
- Masoud, Salekh M.,Mailyan, Artur K.,Peregudov, Alexander S.,Bruneau, Christian,Osipov, Sergey N.
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p. 474 - 476
(2016/11/30)
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- Synthesis and characterization of new ruthenium N-heterocyclic carbene Hoveyda II-type complexes. Study of reactivity in ring closing metathesis reactions
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This manuscript describes the synthesis and structural study of new second generation Hoveyda-Grubbs catalysts: 1,3-dimesityl-acenaphthylenyl-4,5- imidazolin-2-ylidene (BIAN-NHC) ruthenium isopropoxybenzylidene dichloride 3 and 1,3-bis(2,6-dimethylphenyl)
- Merino, Estibaliz,Poli, Evelyne,Diaz, Urbano,Brunel, Daniel
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supporting information
p. 10913 - 10918
(2012/10/29)
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- Synthesis of 1,4-diazabutadienes (=N,N′-ethane-1,2- diylidenebis[amines]) by grinding
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A simple and convenient method for the synthesis of 1,4-diazabutadienes (=N,N′-ethane-1,2-diylidenebis[amines]) by grinding glyoxal (=ethanedial) or an α-diketone and anilines (=benzenamines) in the presence of TsOH in a mortar with a pestle is described.
- He, Jingyu,Xin, Hongxing,Yan, Hong,Song, Xiuqing,Zhong, Rugang
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experimental part
p. 159 - 162
(2011/03/16)
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- Effect of ligand substituents in olefin polymerisation by half-sandwich titanium complexes containing monoanionic iminoimidazolidide ligands-MAO catalyst systems
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Various half-sandwich titanium complexes containing iminoimidazolidide ligands, CpTiCl2[1,3-R2(CH2N)2CN] (1a-d) [R = Ph (a), 2,6-Me2C6H3 (b), cyclohexyl (c), tBu (d)], have been employed as the catalyst precursors for ethylene polymerisation, syndiospecific styrene polymerisation, and copolymerisation of ethylene with 1-hexene in the presence of MAO cocatalyst; 1d showed the highest catalytic activity for ethylene polymerisation whereas 1b showed the highest activity for syndiospecific styrene polymerisation.
- Nomura, Kotohiro,Fukuda, Hiroya,Katao, Shohei,Fujiki, Michiya,Kim, Hyun Joon,Kim, Dong-Hyun,Zhang, Shu
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scheme or table
p. 7842 - 7849
(2011/09/20)
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- Synthesis of chromium N-heterocyclic carbene complexes using chromium Fischer carbenes as a source of chromium carbonyls
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Chromium Fischer carbene complexes, [Cr{{double bond, long}OMe(R)}(CO)5] have been utilized as a source of chromium carbonyls in the synthesis of chromium NHC complexes. Using the synthetic method, chromium complexes of various NHC ligands were isolated in reasonable yields. Moreover, the method can be employed for the synthesis of molybdenum and tungsten NHC compounds.
- Kim, Seongjin,Choi, Soo Young,Lee, Young Tak,Park, Kang Hyun,Sitzmann, Helmut,Chung, Young Keun
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p. 5390 - 5394
(2008/03/12)
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