41446-63-3Relevant academic research and scientific papers
Cationic Tungsten Imido Alkylidene N-Heterocyclic Carbene Complexes That Contain Bulky Ligands
Buchmeiser, Michael R.,Frey, Wolfgang,Musso, Janis V.,Schowner, Roman
, p. 3145 - 3157 (2021/09/30)
Neutral and cationic tungsten imido alkylidene complexes of the general formulas W(NtBu)(CHR1)(OR2)Cl(NHC), W(N-2,6-bis(2,4,6-tri-iPr-C6H4)phenyl)(CHR1)Cl2(NHC), [W(NtBu)(CHR1)(OR2)(NHC)][B(ArF)4] and [W(N-2,6-bis(2,4,6-tri-iPr-C6H4)phenyl)(CHR1)Cl(NHC)][B(ArF)4] (R1= CMe3, CMe2Ph; R2= sterically demanding alkoxide; B(ArF)4= tetrakis(3,5-(CF3)2-C6H3)borate; NHC = N-heterocyclic carbene) were prepared. Two electronically different NHCs, namely 1,3-dimethylimidazol-2-ylidene (IMe) and 1,3-dimethyl-4,5-dichloroimidazol-2-ylidene (IMeCl), as well as a variety of terphenolates and a chiral biphenolate were employed.Z-selective homometathesis (HM) of unfunctionalized olefins was achieved with a selectivity of up to 90% and decent turnover numbers (TON) of up to 480 in the HM of 1-dodecene. Additionally, the reactivity of the cationic tungstentert-butylimido complexes in the reaction with vinyltrimethylsilane and ethylene was investigated, which yielded the corresponding silyl-alkylidene complex and, for the first time, a fully characterized cationic tungsten(IV) NHC ethylene complex.
SYNTHESIS OF PHEROMONE DERIVATIVES VIA Z-SELECTIVE OLEFIN METATHESIS
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Paragraph 0222; 0233, (2021/12/28)
Disclosed herein are methods for synthesizing fatty olefin metathesis products of high Z-isomeric purity from olefin feedstocks of low Z-isomeric purity. The methods include contacting a contacting an olefin metathesis reaction partner, such as acylated alkenol or an alkenal acetal, with an internal olefin in the presence of a Z-selective metathesis catalyst to form the fatty olefin metathesis product. In various embodiments, the fatty olefin metathesis products are insect pheromones. Pheromone compositions and methods of using them are also described.
Z-Selective Monothiolate Ruthenium Indenylidene Olefin Metathesis Catalysts
Smit, Wietse,Ekeli, Jonas B.,Occhipinti, Giovanni,Wo?niak, Bartosz,T?rnroos, Karl W.,Jensen, Vidar R.
, p. 397 - 407 (2020/02/13)
Ru-alkylidenes bearing sterically demanding arylthiolate ligands (SAr) constitute one of only two classes of catalyst that are Z-selective in metathesis of 1-alkenes. Of particular interest are complexes bearing pyridine as a stabilizing donor ligand, [RuCl(SAr)(a? CHR)(NHC)(py)] (R = phenyl or 2-thienyl, NHC = N-heterocyclic carbene, py = pyridine), which initiate catalysis rapidly and give appreciable yields combined with moderate to high Z-selectivity within minutes at room temperature. Here, we extend this chemistry by synthesizing and testing the first two such complexes (5a and 5b) bearing 3-phenylindenylidene, a ligand known to promote stability in other ruthenium-based olefin metathesis catalysts. The steric pressure resulting from the three bulky ligands (the NHC, the arylthiolate, and the indenylidene) forces the thiolate ligand to position itself trans to the NHC ligand, a configuration different from that of the corresponding alkylidenes. Surprisingly, although this configuration is incompatible with Z-selectivity and slows down pyridine dissociation, the two new complexes initiate readily at room temperature. Although their thermal stability is lower than that of typical indenylidene-bearing catalysts, 5a and 5b are fairly stable in catalysis (TONs up to 2200) and offer up to ca. 80% of the Z-isomer in prototypical metathesis homocoupling reactions. Density functional theory (DFT) calculations confirm the energetic cost of dissociating pyridine from 5a (= M1-Py) to generate 14-electron complex M1. Whereas the latter isomer does not give a metathesis-potent allylbenzene ?-complex, it may isomerize to M1-trans and M2, which both form ?-complexes in which the olefin is correctly oriented for cycloaddition. The olefin orientation in these complexes is also indicative of Z-selectivity.
Extension of surface organometallic chemistry to metal?organic frameworks: Development of a well-defined single site [(≡Zr? O?)W(=O)(CH2TBu)3] olefin metathesis catalyst
Thiam, Zeynabou,Abou-Hamad, Edy,Dereli, Busra,Liu, Lingmei,Emwas, Abdul-Hamid,Ahmad, Rafia,Jiang, Hao,Isah, Abdulrahman Adamu,Ndiaye, Papa Birame,Taoufik, Mostafa,Han, Yu,Cavallo, Luigi,Basset, Jean-Marie,Eddaoudi, Mohamed
supporting information, p. 16690 - 16703 (2020/11/09)
We report here the first step by step anchoring of a W(≡CtBu)(CH2tBu)3 complex on a highly crystalline and mesoporous MOF, namely Zr-NU-1000, using a Surface Organometallic Chemistry (SOMC) concept and methodology. SOMC allowed us to selectively graft the complex on the Zr6 clusters and characterize the obtained single site material using state of the art experimental methods including extensive solid-state NMR techniques and HAADF-STEM imaging. Further FT?IR spectroscopy revealed the presence of a W=O moiety arising from the in situ reaction of the W≡CtBu functionality with the coordinated water coming from the 8-connected hexanuclear Zr6 clusters. All the steps leading to the final grafted molecular complex have been identified by DFT. The obtained material was tested for gas phase and liquid phase olefin metathesis and exhibited higher catalytic activity than the corresponding catalysts synthesized by different grafting methods. This contribution establishes the importance of applying SOMC to MOF chemistry to get well-defined single site catalyst on MOF inorganic secondary building units, in particular the in situ synthesis of W=O alkyl complexes from their W carbyne analogues.
Specialized ruthenium olefin metathesis catalysts bearing bulky unsymmetrical NHC Ligands: Computations, synthesis, and application
Ma?ecki, Pawe?,Gajda, Katarzyna,Gajda, Roman,Wo?niak, Krzysztof,Trzaskowski, Bartosz,Kajetanowicz, Anna,Grela, Karol
, p. 587 - 598 (2019/01/08)
Second-generation ruthenium olefin metathesis catalysts were investigated with systematic variation of the unsymmetrical uNHC ligands. Depending on the uNHC steric bulk, the catalysts exhibited different activity and selectivity in metathesis reactions. DFT calculations and X-ray crystallographic data were used to understand the influence of uNHC ligand structure on the catalyst properties. Furthermore, the catalysts were examined in the context of reactions that are problematic for general-purpose Ru catalysts, including industrially important self-cross metathesis of α-olefins and ethenolysis of ethyl oleate.
Catalytic Chemoselective and Stereoselective Semihydrogenation of Alkynes to E-Alkenes Using the Combination of Pd Catalyst and ZnI2
Maazaoui, Radhouan,Abderrahim, Raoudha,Chemla, Fabrice,Ferreira, Franck,Perez-Luna, Alejandro,Jackowski, Olivier
supporting information, p. 7544 - 7549 (2019/01/03)
An efficient E-selective semihydrogenation of internal alkynes was developed under low dihydrogen pressure and low reaction temperature from commercially available reagents: Cl2Pd(PPh3)2, Zn0, and ZnI2. Kinetic studies and control experiments underline the significant role of ZnI2 in this process under H2 atmosphere, establishing that the transformation involves syn-hydrogenation followed by isomerization. This simple and easy-to-handle system provides a route to E-alkenes under mild conditions.
Olefin metathesis in air using latent ruthenium catalysts: Imidazole substituted amphiphilic hydrogenated ROMP polymers providing nano-sized reaction spaces in water
?ztürk, Bengi ?zgün,Durmu?, Burcu,Karabulut ?ehito?lu, Solmaz
, p. 5807 - 5815 (2018/11/24)
Imidazole substituted hydrogenated amphiphilic ROMP polymers were used as both surfactants and ligand precursors for olefin metathesis reactions in water. Amphiphilic ROMP polymers were synthesized using a two-step procedure. Firstly, dimethyl-5-norbornene-2,3-dicarboxylate was polymerized using ring-opening metathesis polymerization (ROMP)/cross-metathesis (CM) in the presence of allyl-PEG5000 methyl ether and a Grubbs 3rd generation (G3) catalyst. Secondly, a one-pot hydrogenation/aminolysis protocol was used for the post-polymerization modification of PEG end-capped polynorbornene derivatives. Hydrogenation reactions were carried out using residual G3 in the presence of formic acid/sodium formate in THF at 70 °C. The aminolysis reaction was carried out without isolation of the hydrogenated polymer, using triazabicyclodecene (TBD) and 1-(3-aminopropyl)-imidazole, forming imidazole substituted hydrogenated amphiphilic ROMP polymers (mod-Amph1) in an efficient manner. G1-mod-Amph1 formed micelle structures in water with an average particle size of 85.95 (±35) nm as determined by transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis. The diffusion of Grubbs 1st generation (G1) catalyst into the micelle structure has led to the formation of nano-sized catalysts which exhibited a latent characteristic. The diffusion of hydrophobic olefinic substrates into the nano-reaction spaces, followed by activation of the catalyst with HCl led to a very efficient catalytic system for ring-closing metathesis reactions. RCM reactions of various hydrophobic dienes can run in non-degassed water under an air atmosphere. The catalyst system exhibits similar performance under an air atmosphere even in tap water, reaching a conversion value of 90% for RCM of diethyl diallylmalonate with a catalytic loading of 1% Ru.
Au-Catalyzed Intermolecular [2+2] Cycloadditions between Chloroalkynes and Unactivated Alkenes
Bai, Yu-Bin,Luo, Zaigang,Wang, Yuguang,Gao, Jin-Ming,Zhang, Liming
, p. 5860 - 5865 (2018/05/14)
The [2+2] cycloaddition is a versatile strategy for the synthesis of strained cyclobutenes of high synthetic value. In this study, two efficient intermolecular [2+2] cycloadditions between two different types of chloroalkynes and unactivated alkene are realized with gold catalysis. Of significance is that the reaction works with challenging monosubstituted unactivated alkenes, which is unprecedented in gold catalysis and scarcely documented in other metal-catalyzed/promoted reactions; moreover, the reaction exhibits excellent regioselectivities, which are much better than those reported in literature. With 1,2-disubstituted unactivated alkenes, the reaction is largely stereospecific. The cyclobutene products can be prepared in nearly gram scale and readily undergo further reactions including various cross-coupling reactions using the C(sp2)-Cl and/or C(sp2)-SPh bond, which in turn substantially broaden the scope of accessible cyclobutenes and enhance the synthetic utility of this bimolecular reaction.
IMPROVED OLEFIN METATHESIS CATALYSTS
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Page/Page column 40; 41, (2017/02/09)
The present invention refers to novel ruthenium-based catalysts for olefin metathesis reactions, particularly to fast initiating catalysts having stereoselective properties. In olefin metathesis reactions, the disclosed catalysts provide a high catalytic activity combined with the capability to generate higher yields of the olefin metathesis product.
N-Heterocyclic Carbene Complexes Of Metal Imido Alkylidenes And Metal OXO Alkylidenes, And The Use Of Same
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Paragraph 0154, (2017/03/21)
The invention relates to an N-heterocyclic carbene complex of general formulas I to IV (I) (II) (III) (IV), according to which A1 stands for NR2 or PR2, A2 stands for CR2 R2′, NR2, PR2, 0 or S, A3 stands for N or P, and C stands for a carbene carbon atom, ring B is an unsubstituted or a mono or poly-substituted 5 to 7-membered ring, substituents R2 and R2′ stand, inter alia, for a linear or branched C1-Cw-alkyl group and, if N and N each stand for NR2 or PR2, are the same or different, M in formulas I, II, III or IV stands for Cr, Mo or W, X 1 or X2 in formulas I to IV are the same or different and represent, inter alia, C1-C1s carboxylates and C1-C1s-alkoxides, Y is inter alia oxygen or sulphur, Z is inter alia a linear or branched C1-Cw-alkylenoxy group, and R 1 and R1′ in formulas I to IV are, inter alia, an aliphatic or aromatic group. These compounds are particularly suitable for use as catalysts for olefin metathesis reactions and have the advantage, compared to known Schrock carbene complexes, of displaying clearly increased tolerance to functional groups such as, in particular, aldehydes, secondary amines, nitriles, carboxylic acids and alcohols.
