14850-23-8Relevant articles and documents
A well-defined silica-supported tungsten oxo alkylidene is a highly active alkene metathesis catalyst
Conley, Matthew P.,Mougel, Victor,Peryshkov, Dmitry V.,Forrest, William P.,Gajan, David,Lesage, Anne,Emsley, Lyndon,Coperet, Christophe,Schrock, Richard R.
, p. 19068 - 19070 (2013)
Grafting (ArO)2W(i=O)(i=CHtBu) (ArO = 2,6-mesitylphenoxide) on partially dehydroxylated silica forms mostly [(i - SiO)W(i=O)(i=CHtBu) (OAr)] along with minor amounts of [(i - SiO)W(i=O)(CH2tBu) (OAr)2] (20%), both fully ch
Benchmarked Intrinsic Olefin Metathesis Activity: Mo vs. W
Zhizhko, Pavel A.,Mougel, Victor,De Jesus Silva, Jordan,Copéret, Christophe
, (2018)
Combining Surface Organometallic Chemistry with rigorous olefin purification protocol allows evaluating and comparing the intrinsic activities of Mo and W olefin metathesis catalysts towards different types of olefin substrates. While well-defined silica-supported Mo and W imido-alkylidenes show very similar activities in metathesis of internal olefins, Mo catalysts systematically outperform their W analogs in metathesis of terminal olefins, consistent with the formation of stable unsubstituted W metallacyclobutanes in the presence of ethylene. However, Mo catalysts are more prone to induce olefin isomerization, in particular when ethylene is present, probably because of their propensity to undergo more easily reduction processes.
Bulky aryloxide ligand stabilizes a heterogeneous metathesis catalyst
Conley, Matthew P.,Forrest, William P.,Mougel, Victor,Copret, Christophe,Schrock, Richard R.
, p. 14221 - 14224 (2014)
The reaction of [W(=O)(=CHCMe2Ph)(dAdPO)2], containing bulky 2,6-diadamantyl aryloxide ligands, with partially dehydroxylated silica selectively yields a well-defined silica-supported alkylidene complex, [(≡SiO)W(=O)(= CHCMe2Ph)(dAdPO)]. This fully characterized material is a very active and stable alkene metathesis catalyst, thus allowing loadings as low as 50 ppm in the metathesis of internal alkenes. [(≡SiO)W(=O)(=CHCMe2Ph)(dAdPO)] also efficiently catalyzes the homocoupling of terminal alkenes, with turnover numbers exceeding 75 000 when ethylene is constantly removed to avoid the formation of the less reactive square-based pyramidal metallacycle resting state.
Quantitatively Analyzing Metathesis Catalyst Activity and Structural Features in Silica-Supported Tungsten Imido-Alkylidene Complexes
Mougel, Victor,Santiago, Celine B.,Zhizhko, Pavel A.,Bess, Elizabeth N.,Varga, Jeno,Frater, Georg,Sigman, Matthew S.,Copéret, Christophe
, p. 6699 - 6704 (2015)
A broad series of fully characterized, well-defined silica-supported W metathesis catalysts with the general formula [(≡SiO)W(=NAr)(=CHCMe2R)(X)] (Ar = 2,6-iPr2C6H3 (AriPr), 2,6-Cl2C6H3 (ArCl), 2-CF3C6H4 (ArCF3), and C6F5 (ArF5); X = OC(CF3)3 (OtBuF9), OCMe(CF3)2 (OtBuF6), OtBu, OSi(OtBu)3, 2,5-dimethylpyrrolyl (Me2Pyr) and R = Me or Ph) was prepared by grafting bis-X substituted complexes [W(NAr)(=CHCMe2R)(X)2] on silica partially dehydroxylated at 700 C (SiO2-(700)), and their activity was evaluated with the goal to obtain detailed structure-activity relationships. Quantitative influence of the ligand set on the activity (turnover frequency, TOF) in self-metathesis of cis-4-nonene was investigated using multivariate linear regression analysis tools. The TOF of these catalysts (activity) can be well predicted from simple steric and electronic parameters of the parent protonated ligands; it is described by the mutual contribution of the NBO charge of the nitrogen or the IR intensity of the symmetric N-H stretch of the ArNH2, corresponding to the imido ligand, together with the Sterimol B5 and pKa of HX, representing the X ligand. This quantitative and predictive structure-activity relationship analysis of well-defined heterogeneous catalysts shows that high activity is associated with the combination of X and NAr ligands of opposite electronic character and paves the way toward rational development of metathesis catalysts.
Synthesis of erythromycin derivatives via the olefin cross-metathesis reaction
Hsu, Margaret C.,Junia, Adam J.,Haight, Anthony R.,Zhang, Weijiang
, p. 3907 - 3911 (2004)
Olefin cross metathesis (CM) was applied to the synthesis of 6-O-substituted erythromycin derivatives. The reactions were catalyzed by transition metal alkylidene complexes, particularly bis(tricyclohexylphosphine)benzylidine ruthenium (IV) dichloride (Grubbs' first-generation catalyst). This approach allowed for the elaboration of the 6-O-allyl group of highly functionalized macrolides at various stages of the synthetic sequence, affording 6-O-3-aryl-propenyl products with excellent E-selectivity. Little or no self-dimerization of the reacting components was found in the crude mixtures. Preliminary kinetic data accounts for the observed cross-selectivity based on substrate reactivity and steric factors.
Metathesis of hex-1-ene in ionic liquids
Vasnev, Alexander V.,Greish, Alexander A.,Kustov, Leonid M.
, p. 59 - 61 (2004)
The WCl6 + BMIMBF4 and NaReO4 + BMIMCl-AICl3 (BMIM is l-butyl-3-methylimidazolium) systems are effective catalysts for the metathesis of hex-1-ene to form oct-4-ene.
Photochemistry of trivinylboranes: Preparation of anti-adducts of hydroboranes and alkynes
Gano,Srebnik
, p. 4889 - 4892 (1993)
Trivinylboranes, which are conveniently prepared from the addition of diborane to acetylenes, are found to readily undergo photochemical Z/E isomerization. Since the chromaphore of the E-isomer is highly twisted by steric strain, photochemical conditions can completely convert the Z-isomer to the E-isomer. This high yield, two step process, provides an efficient procedure to bring about an anti-addition of hydroboranes to acetylenes.
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)
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.
Reactions of α,β-Epoxysilanes with Grignard Reagents. Generation and Trapping of α-Trimethylsilyl Aldehydes and Ketones
Hudrlik, Paul F.,Hudrlik Anne M.,Misra, Raj N.,Peterson, David,Withers, Gregory P.,Kulkarni, Ashok K.
, p. 4444 - 4448 (1980)
α,β-Epoxysilanes react with Grignard reagents via initial rearrangement to generate α-silyl carbonyl compounds, which are trapped by the Grignard reagent to give β-hydroxysilanes. The reactions of epoxides 8 and 11 take place with very high stereoselectivity to form predominantly erythro β-hydroxysilanes 9 and 12, respectively, which undergo stereospecific β-elimination reactions to give either cis or trans olefins in 96-98percent isomeric purity.
Magnitude and consequences of or ligand σ-donation on alkene metathesis activity in d0 silica supported (≡SiO)W(NAr)(=CHtBu) (OR) catalysts
Mougel,Coperet
, p. 2475 - 2481 (2014)
Well-defined silica supported W catalysts with the general formula [(SiO)W(NAr)(CHtBu)(OR)] (OR = OtBuF9, OtBuF6, OtBu F3, OtBu and OSi(OtBu)3), prepared by grafting bis-alkoxide complexes [W(NAr)(CHtBu)(OR)2] on silica dehydroxylated at 700 °C (SiO2(700)), display unexpectedly high activity in comparison to their Mo homologues. In this series, the activity of the self-metathesis of cis-4-nonene increases as a function of the OR ligand as follows: OtBu F3 3 F6 F9. In addition, the ratio of the two parent metallacyclobutane intermediates, trigonal bipyramidal (TBP)/square pyramidal (SP), which were formed by the metathesis of ethylene and observed by solid-state NMR, follows the same order: OtBu F3 3 F6 F9. This provides clear evidence of the decreasing σ-donating ability of the OR ligand with an increasing number of fluorine atoms and the positioning of a siloxy ligand in between OtBuF3 and OtBuF6. This study provides the first detailed structure-activity relationship analysis of a series of well-defined heterogeneous catalysts, showing that weaker σ-donor OR ligands lead to higher activity, and that the surface siloxy ligand is a rather small and weak σ-donor ligand overall, thus providing highly active yet stable catalysts. This journal is the Partner Organisations 2014.
