Showing papers on "Ring-opening metathesis polymerisation published in 2006"
TL;DR: One example that achieves selectivity with respect to the distribution of product molecular weights is reported, in which n-decane is the predominant high-molecular-weight product of the metathesis of two moles of n-hexane.
Abstract: With petroleum supplies dwindling, there is increasing interest in selective methods for transforming other carbon feedstocks into hydrocarbons suitable for transportation fuel. We report the development of highly productive, well-defined, tandem catalytic systems for the metathesis of n-alkanes. Each system comprises one molecular catalyst (a "pincer"-ligated iridium complex) that effects alkane dehydrogenation and olefin hydrogenation, plus a second catalyst (molecular or solid-phase) for olefin metathesis. The systems all show complete selectivity for linear (n-alkane) product. We report one example that achieves selectivity with respect to the distribution of product molecular weights, in which n-decane is the predominant high-molecular-weight product of the metathesis of two moles of n-hexane.
485 citations
TL;DR: A novel water-soluble ruthenium olefin metathesis catalyst supported by a poly(ethylene glycol) conjugated saturated 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene ligand shows improved activity in ring-opening meetingathesis polymerization, ring-closing metatheses, and cross-metathesis reactions in aqueous media.
Abstract: A novel water-soluble ruthenium olefin metathesis catalyst supported by a poly(ethylene glycol) conjugated saturated 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene ligand is reported. The catalyst displays improved activity in ring-opening metathesis polymerization, ring-closing metathesis, and cross-metathesis reactions in aqueous media.
289 citations
TL;DR: In this paper, the authors introduce a set of six reactions with specific reaction conditions to establish a standard for catalyst comparison in olefin metathesis, and evaluate seven of the most widely used ruthenium-based OO-metathesis catalysts.
286 citations
TL;DR: Mechanistic explanations for the large sodium iodide effect as well as possible mechanistic pathways leading to the observed products are discussed.
Abstract: The synthesis of olefin metathesis catalysts containing chiral, monodentate N-heterocyclic carbenes and their application to asymmetric ring-closing metathesis (ARCM) are reported. These catalysts retain the high levels of reactivity found in the related achiral variants (1a and 1b). Using the parent chiral catalysts 2a and 2b and derivatives that contain steric bulk in the meta positions of the N-bound aryl rings (catalysts 3−5), five- through seven-membered rings were formed in up to 92% ee. The addition of sodium iodide to catalysts 2a−4a (to form 2b−4b in situ) caused a dramatic increase in enantioselectivity for many substrates. Catalyst 5a, which gave high enantiomeric excesses for certain substrates without the addition of NaI, could be used in loadings of ≤1 mol %. Mechanistic explanations for the large sodium iodide effect as well as possible mechanistic pathways leading to the observed products are discussed.
217 citations
TL;DR: Structural investigations suggest that a fluorine-ruthenium interaction is responsible for this increased activity of new rut henium-based olefin metathesis catalysts, featuring fluorinated NHC ligands.
Abstract: The synthesis, structure, and performance of new ruthenium-based olefin metathesis catalysts, featuring fluorinated NHC ligands are presented. The introduction of halogen atoms into the N-heterocyclic carbene ligand profoundly alters the catalytic activity and can afford a more efficient catalyst. Structural investigations suggest that a fluorine−ruthenium interaction is responsible for this increased activity.
170 citations
TL;DR: In this novel strategy for the immobilization of ruthenium-based metathesis catalysts, the amino group plays a two-fold role, being first an active anchor for immobilization and second, after protonation, activating the catalysts (electron donating to electron withdrawing activity switch).
Abstract: A new concept for noncovalent immobilization of a ruthenium olefin metathesis catalyst is presented. The 2-isopropoxybenzylidene ligand of a Hoveyda−Grubbs carbene is further modified by an additional amino group (7) and immobilization is achieved by treatment with sulfonated polystyrene forming the corresponding ammonium salt. In this novel strategy for the immobilization of ruthenium-based metathesis catalysts, the amino group plays a two-fold role, being first an active anchor for immobilization and second, after protonation, activating the catalysts (electron donating to electron withdrawing activity switch). The polymeric support was prepared by precipitation polymerization which led to small bead sizes (0.2−2 μm) and large surface areas. Compared to commercial resins this tailor-made phase showed superior properties in immobilization of complex 7. This concept of immobilization was applied to glass−polymer composite megaporous Raschig rings. Ru catalyst 7 on Raschig rings was used under batch condit...
131 citations
TL;DR: In this article, five imidazol(in)ium-2-carboxylates bearing cyclohexyl, mesityl, or 2,6-diisopropylphenyl substituents on their nitrogen atoms were prepared from the corresponding N-heterocyclic carbenes by reaction with carbon dioxide.
127 citations
TL;DR: The phoban-indenylidene complex is a robust catalyst for self-metathesis and ethenolysis reactions of methyl oleate as mentioned in this paper, which can be accessed from simple precursors and should give rise to more economical metathesis processes.
92 citations
TL;DR: The ring-opening metathesis polymerization (ROMP) of functional norbornenes was performed in the absence of any cosolvent in this paper, and the results showed that it is possible to obtain a polymeric polymerization in a variety of pure ionic liquids (ILs).
Abstract: The ring-opening metathesis polymerization (ROMP) of functional norbornenes, ie, exo,endo-5-norbornene-2-carbonitrile (3), methyl (exo,endo-5-norbornene-2-carboxylate) (4), norborn-5-ene-2-yl acetate (5), 2-propyl exo,endo-5-norbornene-2-carboxylate (6), norborn-5-ene-2-carboxylic acid (7), exo,endo-5-norbornene-2-methanol (8), exo,endo-5-norbornene-2-ylmethyl bromide (9), exo,endo-5-norbornene-2-ylmethylamine (10), exo,endo-5-norbornene-2-triethoxysilane (11), dimethyl exo,endo-5-norbornene-2-yl phosphonate (12), exo,endo-5-norbornene-2-ylcarboxyethyl-3-ethylimidazolium bis(trifluoromethylsulfonyl)imide (13), exo,endo-5-norbornene-2-ylcarboxyethyl-3-ethylimidazolium tetrafluoroborate (14), 7-oxanorborn-5-ene-2,3-dicarboxylic anhydride (15), was performed in a variety of pure ionic liquids (ILs) in the absence of any cosolvent Both imidazolium, ie, [1-butyl-3-methylIM]+X- and [1-butyl-2,3-dimethylIM]+X- (IM+ = imidazolium, X- = PF6-, CF3SO3-, (CF3SO2)2N-, CF3COO-, NO3-, BF4-, Br-), and phosphonium-ba
90 citations
TL;DR: In this article, the synthesis and screening of catalytic activity of two ruthenium carbene complexes 9 and 10 bearing substituents in 2-isopropoxybenzylidene ligand is described.
Abstract: Synthesis and screening of catalytic activity of two novel ruthenium carbene complexes 9 and 10 bearing substituents in 2-isopropoxybenzylidene ligand is described. These precatalysts constitute excellent tools for RCM and enyne metathesis by combining high stability with a possibility of their on-demand activation by heat and Bronsted (9) or Lewis acids (10).
86 citations
TL;DR: Various symmetrically and asymmetrically substituted N-heterocyclic carbene (NHC) ligands bearing aliphatic nitrogen-containing side groups have been synthesised, and attempts to isolate the corresponding second-generation Grubbs catalysts were unsuccessful when using the symmetricalAliphatic NHC ligands.
Abstract: Various symmetrically and asymmetrically substituted N-heterocyclic carbene (NHC) ligands bearing aliphatic nitrogen-containing side groups have been synthesised. In our attempts to isolate the corresponding second-generation Grubbs catalysts, we were unsuccessful when using the symmetrical aliphatic NHC ligands. For the asymmetrical ligands bearing an aliphatic moiety on one side and an aromatic mesityl group on the other side, substitution of a phosphine ligand was achieved. The performance of a so-formed series of Ru-based metathesis initiators has been evaluated for the ring-opening metathesis polymerisation (ROMP) of cycloocta-1,5-diene and the ring-closing metathesis (RCM) of diethyl diallylmalonate.
TL;DR: In this paper, the ring opening of substituted cyclophanedienes by ruthenium-based metathesis catalysts gives sol. phenylenevinylene homopolymers of well-defined mol. wt. with an alternating cis-trans microstructure.
Abstract: Ring opening of substituted cyclophanedienes by ruthenium-based metathesis catalysts gives sol. phenylenevinylene homopolymers of well-defined mol. wt. with an alternating cis-trans microstructure. The living character of this polymn. is demonstrated by controlled chain extension. [on SciFinder (R)]
TL;DR: The utility of Grubbs' 2nd generation metathesis catalyst has been expanded by the development of two tandem olefin meetingathesis/oxidation protocols that provide cis-diols or alpha-hydroxy ketones from simple oleFinic starting materials.
TL;DR: In this paper, the mechanism of alkyne metathesis catalyzed by W/Mo alkylidyne complexes has been theoretically investigated with the aid of density functional theory calculations.
TL;DR: In this paper, a series of synthesized block copolymers that allow conclusions to be drawn how to design micelles by ring opening metathesis polymerization (ROMP) with defined core−shell geometry and controlled size are presented.
Abstract: Self-assembly of well-defined block copolymers in solution has gained attention not only for its scientific value but also for its potential application in nanotechnology. In this study, we present a comprehensive series of synthesized block copolymers that allows conclusions to be drawn how to design micelles by ROMP with defined core−shell geometry and controlled size. We used a general route for the preparation of well-defined block copolymers by ring opening metathesis polymerization (ROMP) with “Grubbs first generation catalyst” RuCl2(PCy3)2(CHPh) (Cy = cyclohexyl). In a first step, we sequentially polymerized endo,exo[2.2.1]bicyclo-2-ene-5,6-dicarboxylic acid dimethylester with endo,exo[2.2.1]bicyclo-2-ene-5,6-dicarboxylic acid di-tert-butyl ester, to obtain a high control of polymerization and complete characterization of the block copolymers. The polymers were characterized by 1H- and 13C NMR spectroscopy, FT-IR spectroscopy, by GPC, and by DSC. By cleavage of the tert-butyl group, the polymer was...
TL;DR: From certain substrates, the direct annulation is observed in the titanium-mediated step, which is likely to occur through an olefin metathesis-intramolecular olefination sequence.
Abstract: The dimethyltitanocene methylenation of N-acylamides derived from ortho-vinylanilines, ortho-allylaniline, and ortho-vinylbenzylamine provides the corresponding enamides, which upon exposure to the second generation Grubbs ruthenium catalyst give access to indoles, 1,4-dihydroquinolines, and 1,2-dihydroisoquinolines, respectively. This sequential protocol also allows the synthesis of dihydrobenzoazepines, although the ring-closing metathesis (RCM) step is complicated by the alkene isomerization processes. From certain substrates, the direct annulation is observed in the titanium-mediated step, which is likely to occur through an olefin metathesis−intramolecular olefination sequence.
TL;DR: The preparation and characterization of a series of first to fourth generation dendronized poly-(norbornenes)s are presented and the monomers were synthesized in a divergent fashion from 5-norbornene-2.
Abstract: The preparation and characterization of a series of first to fourth generation dendronized poly-(norbornene)s are presented. The monomers were synthesized in a divergent fashion from 5-norbornene-2 ...
TL;DR: The functionalized ABC ring system of micrandilactone A was successfully constructed in 14 steps and the key reactions are the intermolecular Diels-Alder reaction (IMDA) and the eneyne ring-closing metathesis (RCM) reaction.
TL;DR: In this paper, the authors highlight some tandem sequences that rely on the conver- sion of the metathesis catalyst to Ru-hydrides, with special emphasis on the tandem ring-closing metatonhesis (RCM)-double-bond isomerization sequence.
Abstract: Tandem sequences consisting of an olefin metathesis step and a subsequent non- metathesis reaction become accessible by organometallic transformations of the Ru-carbene species in situ. This contribution highlights some tandem sequences that rely on the conver- sion of the metathesis catalyst to Ru-hydrides, with special emphasis on the tandem ring- closing metathesis (RCM)-double-bond isomerization sequence.
TL;DR: In this article, the cross-metathesis of methyl maleate (2 ) and ethylene (10 ) using second generation Grubbs catalyst; (1,3-dimesityl-4,5-dihydroimidazol-2-ylidene) (PCy 3 )CI 2 Ru CHPh has been modeled at B3LYP/LACVP ∗ and MPW1K/LCP ∗ levels of theory.
TL;DR: A monomer for ring-opening metathesis polymerization (ROMP) has been developed that also functions as a portion of a GdIII chelating moiety for a magnetic resonance imaging contrast agent, the basis for a new class of highly sensitive, targeted imaging agents.
Abstract: A monomer for ring-opening metathesis polymerization (ROMP) has been developed that also functions as a portion of a GdIII chelating moiety for a magnetic resonance imaging contrast agent. An increase in per GdIII relaxivity was shown upon transition from monomer to polymer. Additionally, extremely large molecular relaxivities were achieved through incorporation of multiple GdIII ions per polymer. The nature of ROMP-derived polymers allows for functionalization of the monomer units and termini through orthogonal chemistry. This strategy is the basis for a new class of highly sensitive, targeted imaging agents.
TL;DR: In this article, the synthesis of bis-silylated Hoveyda-type monomer is described as well as the preparation of several organic-inorganic hybrid materials derived from it by a sol-gel process (with and without tetraethyl orthosilicate) and by anchoring to MCM-41.
Abstract: The synthesis of a bis-silylated Hoveyda-type monomer is described as well as the preparation of several organic-inorganic hybrid materials derived from it by a sol-gel process (with and without tetraethyl orthosilicate) and by anchoring to MCM-41. The resulting materials were treated with second generation Grubbs' catalyst to generate second generation Hoveyda-Grubbs-type alkylideneruthenium complexes covalently bonded to the silica matrix. These materials are recyclable catalysts for the ring-closing metathesis reaction of dienes and enynes.
Patent•
02 Jun 2006
TL;DR: In this paper, a cross-metathesis process for preparing an.alpha.,.omega.-functionalized olefin, such as methyl 9-decenoate, and an ODE having three or more carbon atoms was presented.
Abstract: A cross-metathesis process for preparing an .alpha., .omega.-functionalized olefin, such as methyl 9-decenoate, and an .alpha.-olefin having three or more carbon atoms, such as 1-decene. The process involves contacting in a first reaction zone an .alpha.-functionalized internal olefin, such as methyl oleate, and an .alpha.-olefinic monomer having three or more carbon atoms, such as 1-decene, with a first metathesis catalyst to prepare an effluent stream containing the .alpha., .omega.-functionalized olefin, such as methyl 9-decenoate, an unfunctionalized internal olefin, such as 9-octadecene, unconverted reactant olefins, and optionally, an .alpha., .omega.-difunctionalized internal olefinic dimer, such as dimethyl 9-octadecen-1,18-dioate; separating said effluent streams; then contacting in a second reaction zone the unfunctionalized internal olefin with ethylene in the presence of a second metathesis catalyst to obtain a second product effluent containing the .alpha.-olefinic monomer having three or more carbon atoms; and cycling a portion of the .alpha.-olefinic monomer stream(s) to the first reaction zone.
TL;DR: In this article, the reaction of Cl2Ru(PCy3)2(3-phenylindenylidene) with excess pyridine leads to the new pyridine-containing ruthenium-based complex: Cl 2Ru(Pcy3) 2(Py) 2 (3-PNYLID) in good yield, which has been fully characterized and tested in ring closing metathesis.
TL;DR: Terminal alkyne metathesis has been improved by addition of quinuclidine as an external ligand to the (t-BuO) 3 W≡CBu-t carbyne complex, giving a yield of 80% during hept-1-yne meetathesis.
Abstract: Terminal alkyne metathesis has been improved by addition of quinuclidine as an external ligand to the (t-BuO) 3 W≡CBu-t carbyne complex, giving a yield of 80% during hept-1-yne metathesis. Extension of this system to the co-metathesis of terminal and disubstituted alkynes affords the expected cross-reaction products.