19689-19-1Relevant articles and documents
Effects of boron-containing Lewis acids on olefin metathesis
Simocko, Chester,Wagener, Kenneth B.
, p. 2513 - 2516 (2013)
Boron-containing Lewis acids have shown a profound effect on the cross-metathesis reaction of 1-hexene. Grubbs first-generation catalyst shows over 100% improvement in conversion in some cases, while the yields increase by up to 50% with Grubbs second-generation catalyst. With the inclusion of boron-containing Lewis acids, compounds prepared using Grubbs second-generation-type catalysts display significantly reduced levels of isomerization.
N-chelate ruthenium carbene complexes in olefin metathesis and isomerization
Shcheglova,Kolesnik,Ashirov,Krasnokutskaya
, p. 907 - 909 (2015)
The catalytic activity of N-chelate ruthenium carbene complexes in the metathesis of hex-1-ene has been studied in comparison to the second generation Grubbs catalyst.
Activation of Methyltrioxorhenium for Olefin Metathesis in a Zirconium-Based Metal-Organic Framework
Korzyński, Maciej D.,Consoli, Daniel F.,Zhang, Shiran,Román-Leshkov, Yuriy,Dincǎ, Mircea
, p. 6956 - 6960 (2018)
The zirconium nodes of the metal-organic framework (MOF) known as NU-1000 serve as competent supports for the activation of methyltrioxorhenium (MTO) toward olefin metathesis. Itself inactive for olefin metathesis, MTO becomes an active catalyst only when immobilized on the strongly acidic Lewis acid sites of dehydrated NU-1000. Uptake of MTO at the dehydrated secondary building units (SBUs) occurs rapidly and quantitatively to produce a catalyst active in both gas- and liquid-phase processes. These results demonstrate for the first time the utility of MOF SBUs for olefin metathesis, an academically and industrially relevant transformation.
From Resting State to the Steady State: Mechanistic Studies of Ene-Yne Metathesis Promoted by the Hoveyda Complex
Griffiths, Justin R.,Keister, Jerome B.,Diver, Steven T.
, p. 5380 - 5391 (2016)
The kinetics of intermolecular ene-yne metathesis (EYM) with the Hoveyda precatalyst (Ru1) has been studied. For 1-hexene metathesis with 2-benzoyloxy-3-butyne, the experimental rate law was determined to be first-order in 1-hexene (0.3-4 M), first-order in initial catalyst concentration, and zero-order for the terminal alkyne. At low catalyst concentrations (0.1 mM), the rate of precatalyst initiation was observed by UV-vis and the alkyne disappearance was observed by in situ FT-IR. Comparison of the rate of precatalyst initiation and the rate of EYM shows that a low, steady-state concentration of active catalyst is rapidly produced. Application of steady-state conditions to the carbene intermediates provided a rate treatment that fit the experimental rate law. Starting from a ruthenium alkylidene complex, competition between 2-isopropoxystyrene and 1-hexene gave a mixture of 2-isopropoxyarylidene and pentylidene species, which were trappable by the Buchner reaction. By varying the relative concentration of these alkenes, 2-isopropoxystyrene was found to be 80 times more effective than 1-hexene in production of their respective Ru complexes. Buchner-trapping of the initiation of Ru1 with excess 1-hexene after 50% loss of Ru1 gave 99% of the Buchner-trapping product derived from precatalyst Ru1. For the initiation process, this shows that there is an alkene-dependent loss of precatalyst Ru1, but this does not directly produce the active catalyst. A faster initiating precatalyst for alkene metathesis gave similar rates of EYM. Buchner-trapping of ene-yne metathesis failed to deliver any products derived from Buchner insertion, consistent with rapid decomposition of carbene intermediates under ene-yne conditions. An internal alkyne, 1,4-diacetoxy-2-butyne, was found to obey a different rate law. Finally, the second-order rate constant for ene-yne metathesis was compared to that previously determined by the Grubbs second-generation carbene complex: Ru1 was found to promote ene-yne metathesis 62 times faster at the same initial precatalyst concentration.
Synthesis and some properties of 14 group element-containing alkylidene complexes of molybdenum and tungsten
Bochkarev, Leonid N.,Begantsova, Yulia E.,Shcherbakov, Vladislav I.,Stolyarova, Natalia E.,Grigorieva, Irina K.,Malysheva, Irina P.,Basova, Galina V.,Bochkarev, Andrey L.,Barinova, Yulia P.,Fukin, Georgii K.,Baranov, Evgenii V.,Kurskii, Yurii A.,Abakumov, Gleb A.
, p. 5720 - 5727 (2005)
Alkylidene complex of molybdenum Ph3Si-CHMo(NAr)(OCMe 2CF3)2 (1) (Ar=2,6-Pr2iC6H3) has been prepared by the reaction of Ph3SiCHCH2 with known alkylidene compounds Alkyl-CHMo(NAr)(OCMe2CF3)2 (Alkyl = But, PhMe2C). According to X-ray diffraction studies the geometry of the Mo atom in (1) can be described as a distorted tetrahedron. Reactions of heteroelement-containing imido alkyl compounds of molybdenum and tungsten (ArN)2M(CH2EMe3)2 (Ar=2,6-Pr2iC6H3; M = Mo. W; E = Si, Ge, Sn) with triflic acid were shown to yield a complex mixture of products among which carbene complexes have not been observed. The formation of carbene complexes of tungsten in low yields was observed by 1H NMR spectroscopy in the reactions of (ArN) 2W(CH2EMe3)2 (E = Si, Ge, Sn) with hydrogen chloride in THF-d8. Catalytic properties of heteroelement-containing alkylidene complexes of molybdenum R 3E-CHMo(NAr)(OCMe2CF3)2 (E = Si, Ge; R = Me, Ph) and also hydrocarbon analogs Alkyl-CHMo(NAr)(OCMe 2CF3)2 (Alkyl = But, PhMe 2C) in metathesis of 1-hexene were investigated. The catalytic activity of alkylidene complexes was shown to depend essentially on the nature of substituent bonded to carbene carbon atom.
Olefin metathesis catalyst systems based on molybdenum halides and organosilicon compounds
Bykov,Belyaev,Butenko,Finkel'shtein
, p. 121 - 124 (2016)
The catalytic activity of heterogeneous catalytic systems based on molybdenum halides immobilized onto the silica gel surface in combination with organosilicon cocatalysts has been studied in a model reaction of hexene-1 metathesis at 27 and 50°C. It has been established that quite active catalysts are formed when using 1,1,3,3-tetramethyl-1,3-disilacyclobutane or triethylsilane as cocatalysts. Tetramethylsilane has exhibited no marked activity, while tetramethyltin has turned out to be the most effective cocatalyst. Possible routes of formation of active centers have been proposed for organosilicon cocatalysts.
Continuous Flow Z-Stereoselective Olefin Metathesis: Development and Applications in the Synthesis of Pheromones and Macrocyclic Odorant Molecules**
Browne, Duncan L.,Colombel-Rouen, Sophie,Crévisy, Christophe,Curbet, Idriss,Mauduit, Marc,McBride, Tom,Morvan, Jennifer,Roisnel, Thierry
supporting information, p. 19685 - 19690 (2021/08/06)
The first continuous flow Z-selective olefin metathesis process is reported. Key to realizing this process was the adequate choice of stereoselective catalysts combined with the design of an appropriate continuous reactor setup. The designed continuous process permits various self-, cross- and macro-ring-closing-metathesis reactions, delivering products in high selectivity and short residence times. This technique is exemplified by direct application to the preparation of a range of pheromones and macrocyclic odorant molecules and culminates in a telescoped Z-selective cross-metathesis/ Dieckmann cyclisation sequence to access (Z)-Civetone, incorporating a serial array of continually stirred tank reactors.
Boosting the Metathesis Activity of Molybdenum Oxo Alkylidenes by Tuning the Anionic Ligand σ Donation
De Jesus Silva, Jordan,Pucino, Margherita,Zhai, Feng,Mance, Deni,Berkson, Zachariah J.,Nater, Darryl F.,Hoveyda, Amir H.,Copéret, Christophe,Schrock, Richard R.
supporting information, p. 6875 - 6880 (2021/02/06)
The catalytic performances of molecular and silica-supported molybdenum oxo alkylidene species bearing anionic O ligands [ORF9, OTPP, OHMT - where ORF9 = OC(CF3)3, OTPP = 2,3,5,6-tetraphenylphenoxy, OHMT = hexamethylterphenoxy] with different σ-donation a
Increasing Olefin Metathesis Activity of Silica-Supported Molybdenum Imido Adamantylidene Complexes through E Ligand σ-Donation
Nater, Darryl F.,Paul, Bhaskar,L?tsch, Lukas,Schrock, Richard R.,Copéret, Christophe
, (2021/09/29)
Molybdenum imido adamantylidene complexes with different substituents on the imido ligand (dipp=2,6-diisopropylphenyl, ArF5=C6F5, and tBu) having distinct electron donating abilities were investigated for the metathesis of internal and terminal olefins, for both molecular and silica-supported species using standardized protocols. Here we show that surface immobilization of these compounds results in dramatically increased activity compared to their molecular counterparts. Additionally, we show that electron withdrawing imido groups increase the activity of the compound towards terminal olefins while they simultaneously decrease the ability to metathesize internal olefins. Furthermore, these systems also show high stability when used as initiators in olefin metathesis, although the species that display higher initial activity deactivate faster than those that show more a more moderate reaction rate at first. Our catalytic studies, augmented by DFT calculations, show that all investigated compounds have a remarkably small energy difference between the trigonal bipyramidal (TBP) and square planar (SP) configurations of the metallacyclobutane intermediates, which has previously been linked to high activity.
A Macrocyclic Ruthenium Carbene for Size-Selective Alkene Metathesis
Diver, Steven T.,Zhang, Yutong
supporting information, (2020/02/22)
The synthesis of a macrocyclic Ru carbene catalyst for selective cross alkene metathesis is reported. The new catalyst showed different reactivity for various type 1 alkenes in homodimerization which correlated with the aggregrate size of the allylic substituent. The altered reactivity profile allowed for selective product formation in competition cross alkene metathesis between two different type 1 alkenes and tert-butyl acrylate. Selectivity in these reactions is attributed to the ability of the macrocyclic catalyst to differentiate alkenes based on their size. Two preparative examples of cross metathesis with the macrocyclic catalyst are also provided.
