7433-56-9Relevant academic research and scientific papers
Effect of the nature of carbene fragments in the tungsten complexes PhMe2E-CH=W(NAr)(OR')2 and Me3E-CH=W(NAr)(OR') 2 (E = C, Si) on their catalytic properties in olefin metathesis reactions
Bochkarev,Begantsova,Platonova,Basova,Grigor'eva,Stolyarova,Malysheva,Fukin,Baranov,Kurskii,Bochkarev,Abakumov
, p. 1874 - 1879 (2008)
Catalytic properties of the silicon-containing carbene complexes of tungsten Me3Si-CH=W(NAr)(OR')2(1) and PhMe 2Si-CH=W(NAr)(OR')2 (2) and their hydrocarbon analogs Me3C-CH=W(NAr)(OR')2 (3) and PhMe2C-CH=W(NAr) (OR')2 (4) (Ar = 2,6-Pri 2C6H 3, R' = CMe2CF3) were studied in homometathesis of hex-1-ene, metathesis polycondensation of deca-1,9-diene, and ring opening metathesis polymerization of cyclooctene. The nature of the carbene fragment in the tungsten catalysts substantially affects their catalytic activity. Silicon-containing catalysts 1 and 2 were found to be 3-5 times less active than their hydrocarbon analogs 3 and 4. Metathesis polymerization of cyclooctene in the bulk with initiators 1-4 completed within a few minutes to form a block. Stereoregularity of the formed polyoctenamers depends to a considerable extent on the nature of the carbene fragments in the starting initiators. Initiators 1-2 lead to polyoctenamers mainly containing the cis-units, whereas the use of complexes 3 and 4 affords polyoctenamers mainly containing the trans-units. The structures of novel compound 2 and known complexes 1, 3, and 4 were determined by X-ray diffraction analysis.
Dinuclear cobalt complex-catalyzed stereodivergent semireduction of alkynes: Switchable selectivities controlled by H2O
Chen, Ke,Zhu, Hongdan,Li, Yuling,Peng, Qian,Guo, Yinlong,Wang, Xiaoming
, p. 13696 - 13705 (2021/11/16)
Catalytic semireduction of internal alkynes to alkenes is very important for organic synthesis. Although great success has been achieved in this area, switchable Z/E stereoselectivity based on a single catalyst for the semireduction of internal alkynes is a longstanding challenge due to the multichemo- and stereoselectivity, especially based on less-expensive earth-abundant metals. Herein, we describe a switchable semireduction of alkynes to (Z)- or (E)-alkenes catalyzed by a dinuclear cobalt complex supported by a macrocyclic bis pyridyl diimine (PDI) ligand. It was found that cis-reduction of the alkyne occurs first and the Z-E alkene stereoisomerization process is formally controlled by the amount of H2O, since the concentration of H2O may influence the catalytic activity of the catalyst for isomerization. Therefore, this protocol provides a facile way to switch to either the (Z)- or (E)-olefin isomer in a single transformation by adjusting the amount of water.
Enantiopure 2,9-Dideuterodecane – Preparation and Proof of Enantiopurity
Christoffers, Jens,Eru?ar, Gülsera,Fsadni, Miriam H.,Golding, Bernard T.,Mitschke, Nico,Roberts, Amy R.,Sadeghi, Majid M.,Wilkes, Heinz
, p. 3854 - 3863 (2021/08/24)
(R,R)- and (S,S)-(2,9-2H2)-n-Decane were prepared regio- and stereospecifically in 25–26 % yield over five steps from commercially available enantiopure (R)- and (S)-propylene oxide, respectively. The synthetic procedure involved nucleophilic displacement of (R)- and (S)-4-toluenesulfonic acid 1-methyl-4-pentenyl ester with LiAlD4 to furnish the respective (5-2H)-1-hexenes. Subsequent olefin metathesis and reduction of the double bond furnished the title compounds. The optical purity of (R,R)- and (S,S)-(2,9-2H2)-n-decane could not be determined by chromatography or polarimetry. Therefore, (R,R)- and (R,S)-(5-2H)-3-hydroxy-2-hexanone were prepared from their respective hexenes by Wacker oxidation, followed by enantioselective α-hydroxylation. The enantiopurity could then be determined by NMR spectroscopy because the stereospecifically deuterated hydroxyketones showed separated signals for the subterminal carbon atom (C-5) in the 13C NMR spectrum.
SYNTHESIS OF PHEROMONE DERIVATIVES VIA Z-SELECTIVE OLEFIN METATHESIS
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Paragraph 0222; 0226-0229, (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.
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.
An Annelated Mesoionic Carbene (MIC) Based Ru(II) Catalyst for Chemo- And Stereoselective Semihydrogenation of Internal and Terminal Alkynes
Bera, Jitendra K.,Choudhury, Joyanta,Das, Shubhajit,Dutta, Indranil,Pati, Swapan K.,Saha, Sayantani,Yadav, Suman
, p. 3212 - 3223 (2020/10/02)
The catalytic utility of [RuL1(CO)2I2] (1), containing an annelated π-conjugated imidazo-naphthyridine-based mesoionic carbene (MIC) ligand (L1), is evaluated for E-selective alkyne semihydrogenation. The precatalyst 1, in combination with 2 equiv of AgBArF, semihydrogenates a broad range of internal alkynes with molecular hydrogen (5 bar) in water. (E)-Alkenes are accessed in high yields, and a number of reducible functional groups are tolerated. A chelate MIC ligand and two cis carbonyls provide a well-defined platform at the Ru center for hydrogenation and isomerization. The loss of two iodides and the presence of two carbonyls render the Ru center electron deficient and thus the formation of metal vinylidenes with terminal alkynes is avoided. This is leveraged for the semihydrogenation of terminal alkynes by the same catalytic system in isopropyl alcohol. Reaction profile, isomerization, kinetic, and DFT studies reveal initial alkyne hydrogenation to a (Z)-alkene, which further isomerizes to an (E)-alkene via metal-catalyzed Z → E isomerization.
Activation of Low-Valent, Multiply M-M Bonded Group VI Dimers toward Catalytic Olefin Metathesis via Surface Organometallic Chemistry
Celik, Gokhan,Chapovetsky, Alon,Delferro, Massimiliano,Dogan, Fulya,Ferrandon, Magali S.,Kaphan, David M.,Khetrapal, Navneet,Kim, Hacksung,Kropf, A. Jeremy,Langeslay, Ryan R.,Perras, Frédéric A.,Pruski, Marek,Sattelberger, Alfred P.,Sharma, Prachi,Wegener, Evan C.,Wen, Jianguo,White, Jacob
supporting information, p. 1035 - 1045 (2020/05/04)
Olefin metathesis is a broadly employed reaction with applications that range from fine chemicals to materials and petrochemicals. The design and investigation of olefin metathesis catalysts have been ongoing for over half a century, with advancements made in terms of activity, stability, and selectivity. Immobilization of organometallic complexes onto solid supports such as silica or alumina is a promising strategy for catalyst heterogenization, often resulting in increased activity and stability. Consequently, a broad range of early transition metal catalysts bearing alkyl, oxide/alkoxide, and amide ligands have been grafted onto silica and their reactivities investigated. Herein, we report a series of silica-supported tungsten and molybdenum dimers (X3MMX3, where M = W and Mo; X = neopentyl, tert-butoxide, and dimethyl amide) and their reactivities toward catalytic olefin metathesis. Dynamic nuclear polarization (DNP)-enhanced solid-state nuclear magnetic resonance (SSNMR), diffuse reflectance infrared Fourier transform (DRIFT), UV resonance Raman, and X-ray absorption (XAS) spectroscopies suggest that upon heterogenization the dimers bind to the surface in a monopodal fashion, with the MM triple bond remaining intact. These structural assignments were further corroborated by density functional theory (DFT) calculations. While the homogeneous dimer counterparts are inert, the supported low-valent alkyl W and Mo dimers become active for the disproportionative self-metathesis of propylene to ethylene and butenes and 4-nonene to 4-octene and 5-decene under mild conditions. The lack of activity observed for the free and supported tert-butoxide and dimethyl amide dimers likely suggests that the neopentyl groups are necessary for the formation of a putative alkylidene active species. The difference in reactivity between the free and supported dimers could be explained either by the lowering of the activation barrier of the complex through the electronic effects of the surface or by site isolation of catalytically relevant reactive intermediates.
Silica-supported Z-selective Ru olefin metathesis catalysts
Renom-Carrasco, Marc,Mania, Philipp,Sayah, Reine,Veyre, Laurent,Occhipinti, Giovanni,Jensen, Vidar R.,Thieuleux, Chloé
, (2020/01/21)
Recently reported thiolate-coordinated ruthenium alkylidene complexes show promise in Z-selective and stereoretentive olefin metathesis reactions. Herein we describe the immobilization of three Ru complexes containing a bulky aryl thiolate on mesostructured silica via surface organometallic chemistry. The applied methodology gives isolated catalytic sites homogeneously distributed on the silica surface. The catalytic results with two model substrates show comparable Z-selectivities to those of the homogeneous counterparts.
Molybdenum Benzylidyne Complexes for Olefin Metathesis Reactions
Acosta, Carlos M.,Bukhryakov, Konstantin V.,Chuprun, Sergey,Mathivathanan, Logesh
supporting information, p. 3453 - 3457 (2020/11/02)
The molybdenum benzylidynes [ArCMo(OC(CF3)2CH3)3(1,2-dimethoxyethane)], where Ar = Ph (2a), p-(OCH3)C6H4 (2b), p-(CF3)C6H4 (2c), p-(NO2)C6H4 (2d), or 4-(NO2)-3-(CF3)C6H3 (2e), and [p-(NO2)C6H4CMo(OC(CF3)2CH3)3] (2f) catalyze the ring-closing metathesis (RCM) reaction of diallyl N-tosylamide (3) to produce 1-tosyl-2,5-dihydro-1H-pyrrole (4) and ethylene. The scope of RCM catalytic activity of 2e, cross-metathesis of 1-hexene, and ring-opening metathesis polymerization of cyclooctene were explored. The X-ray crystal structure of 2e was determined. Variable-temperature 1H NMR spectra revealed the formation of intermediates during the reaction of 3 with 2f and the reforming of 2f after completion of the reaction. The use of 13C-labeled Mo benzylidyne did not show transfer of the carbon atom next to Mo to any of the products.
Method for selective synthesis of cis-olefins and trans-olefins by semi-reduction of alcohol hydrogen supply palladium-catalyzed alkynes
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Paragraph 0174-0176, (2019/06/07)
The invention provides a method for selective synthesis of cis-olefins and trans-olefins by semi-reduction of alcohol hydrogen supply palladium-catalyzed alkynes. The method comprises the following steps: performing alkyne reduction reaction with TEOA, NaOAc, a catalyst, alcohol and alkynes in an organic solvent and generating the cis-olefins after reaction; performing alkyne reduction reaction with a ligand, a catalyst, alcohol and alkynes in an organic solvent and generating the trans-olefins after reaction; a reactor for the reduction reaction is a sealed pressure-resistant reactor, the reduction reaction temperature is 120-150 DEG C, and the reduction reaction time is 20-48 hours; the dosage of the catalyst is 5-20 percent of the molar dosage of the alkynes, and the dosage of the alcohol is 10-100 times of the molar dosage of the alkynes; the dosage of R, R-DIPAMP is 0.5-5 times of the molar dosage of the alkynes. According to the method provided by the invention, a catalyst systemhas extremely-high chemical reaction and stereo-selectivity and can synthesize cis-olefin products or trans-olefin products with high yield; the catalyst system is good universality to a substrate, and the alkynes containing various functional groups can be efficiently subjected to the highly-selective reduction reactions.
