Showing papers on "Ring-opening metathesis polymerisation published in 1998"

Ring-Closing Metathesis of Functionalized Acetylene Derivatives: A New Entry into Cycloalkynes.

Abstract: A tungsten alkylidyne catalyst is the key to achieving ring-closing metatheses of diynes to form functionalized macrocycles [Eq. (a)]. Partial reduction of the cycloalkynes provides stereoselective Z-configured cycloalkenes, which are currently inaccessible by conventional alkene metathesis.

Dipyridyl Amide-Functionalized Polymers Prepared by Ring-Opening-Metathesis Polymerization (ROMP) for the Selective Extraction of Mercury and Palladium

Abstract: Ring-opening-metathesis polymerization (ROMP) was used for the preparation of a dipyridylcarbamide-functionalized polymer suitable for solid-phase extraction of metal ions from aqueous solutions. Resins were prepared by the copolymerization of the functional monomer N,N-di-2-pyridyl-endo-norborn-2-ene-5-carboxamide (I) with 1,4,4a,5,8,8a-hexahydro-1,4,5,8-exo-endo-dimethanonaphthalene (II), using the well-defined Schrock catalyst Mo(N-2,6-i-Pr2C6H3)CHCMe2Ph(OCMe(CF3)2)2 (III). The polymerization proceeds in a living manner, allowing the stoichiometric buildup of polymers. NMR investigations proved the expected backbone structure of the resulting polymers, where the binding site of the monomer remains unaffected in course of the polymerization. The new materials were investigated in terms of their complexation behavior versus a large variety of mono-, di-, tri-, and tetravalent metal ions employing UV−vis spectroscopy as well as AAS and ICP−OES techniques. The polymer-bound dipyridylamide ligand showed exc...

Colloid-Bound Catalysts for Ring-Opening Metathesis Polymerization: A Combination of Homogenous and Heterogeneous Properties.

Abstract: Tailor-made thiols allow a ruthenium-based catalyst for ring-opening metathesis polymerization (ROMP) to be tethered to bulk gold surfaces and to gold colloids (see picture). The functionalized gold colloids combine the properties of homogeneous and heterogeneous catalyst systems. Tethering of the catalyst leads to a pronounced increase in its catalytic activity.

Olefin Metathesis by Well-Defined Complexes of Molybdenum and Tungsten

Abstract: Olefin metathesis is a catalytic process whose key step consists of a reaction between an olefin and a transition metal alkylidene complex. Some of the best understood alkylidene catalysts contain Mo or W in its highest possible oxidation state, along with “supporting” alkoxide ligands and an imido ligand. Recent advances in our understanding of these catalysts from a fundamental perspective, and in ring opening metathesis polymerization (ROMP) and ring closing metathesis (RCM), in particular, are reviewed.

Ruthenium Trichloride, Tricyclohexyl‐ phosphane, 1‐Alkynes, Magnesium, Hydrogen, and Water—Ingredients of an Efficient One‐Pot Synthesis of Ruthenium Catalysts for Olefin Metathesis

Abstract: An active role is played by MgCl2 during the conversion of the vinylidene precursor 2 into carbenes 3 (R=H, Ph; L=P(C6 H11 )3 ). These complexes can be prepared in a convenient and very efficient one-pot synthesis and have a catalytic activity in metathesis comparable to that of Grubbs compound (Ph instead of CH2 R).

The polymerization of dicyclopentadiene: an investigation of mechanism

Abstract: This contribution presents further information about the mechanism of the cross-linking reaction which occurs during the polymerization of dicyclopentadiene with the classical catalyst, WCl6/Et2AlCl (1), and the well-defined preformed alkylidene, Mo(N-2,6-C6H3-i-Pr)(CHC(CH3)2Ph)(OCCH3(CF3)2)2 (2). When the classical system 1 was used as a catalyst, insoluble polymer was formed in all cases. However, when molybdenum catalyst 2 is employed, solution concentration determines whether soluble or insoluble polymer will form. The formation of insoluble material is attributed to an olefin addition process catalyzed by the heat released upon ring-opening metathesis polymerization of the norbornene subunit of the monomer. If the heat is removed from the polymerization system through dilution or by cooling the solution, soluble linear polymer is formed. These results suggest that an olefin addition process is at least partly responsible for the cross-linking reaction that occurs during the polymerization of dicyclopentadiene. All attempts to cross-link oligomers of linear polydicyclopentadiene with the well-defined molybdenum alkylidene 2 resulted in only the recovery of soluble polymer. With the classical catalyst system 1, insoluble material was obtained, which was assumed to be cross-linked through olefin addition. These results disprove the idea that metathesis cross-linking can be induced by a critical chain length or concentration of polydicyclopentadiene. On the contrary, no indication of metathesis cross-linking was observed whatsoever for these polymerization systems.

Acid activation of ruthenium metathesis catalysts and living romp metathesis polymerization in water

Abstract: Activation of ruthenium based catalyst compounds with acid to improve reaction rates and yields of olefin metathesis reactions, including ROMP, RCM, ADMET and cross-methasis reactions is disclosed. The ruthenium catalyst compounds are ruthenium carbene complexes of the general formula AxLyXzRu=CHR' where x = 0, 1 or 2, y = 0, 1 or 2, and z = 1 or 2 and where R' is hydrogen or a substituted or unsubstituted alkyl or aryl, L is any neutral electron donor, X is any anionic ligand, and A is a ligand having a covalent structure connecting a neutral electron donor and an anionic ligand. The use of acid with these catalysts allows for reactions with a wide range of olefins in a variety of solvents, including acid-initiated RIM processes and living ROMP reactions of water-soluble monomers in water.

Schiff base derivatives of ruthenium and osmium olefin metathesis catalysts

Abstract: The present invention generally relates to ruthenium and osmium carbene catalysts for use in olefin metathesis reactions. More particularly, the present invention relates to Schiff base derivatives of ruthenium and osmium carbene catalysts and methods for makig the same. The inventive catalyst are generally prepared by the treatment of unmodified catalysts with the salts of the desired Schiff base ligands, in which an anionic and a neutral electron donating ligands of the unmodified catalysts are simultaneously replaced. The Schiff base derivatives of the ruthenium and osmium carbene catalysts show unexpectedly improved thermal stability while maintaining high metathesis activity, even in polar protic solvents. Although the inventive catalysts may be used in all metathesis reactions, use of these catalysts for ring-closing metathesis ("RCM") reactions is particularly preferred.

Metathesis polymerization of olefins and polymerization of alkynes

Abstract: Part I: Metathesis Polymerization of Olefins: Romp and Admet. Ring-Opening Metathesis Polymerization by Molybdenum Imido Alkylidene Complexes R.R. Schrock. Metathesis of Low-Strain Olefins and Functionalized Olefins with New Ruthenium-Based Catalyst Systems A.F. Noels, A. Demonceau. Synthesis of Aryloxide Tungsten (VI) Complexes and Their Application in Olefin Metathesis F. Lefebvre, et al. Novel Catalysts for Addition Polymerization of Norbornene and its Derivatives K.L. Makovetsky, et al. The Use of Non-Traditional Catalysts in the ROMP of Cycloolefins K.L. Makovetsky. Correlation between Catalyst Nature and Polymer Selectivity in ROMP of Cycloolefins with WCl6-Based Catalytic Systems V. Dragutan, et al. Ring-Opening Metathesis Polymerization of Cycloolefins Using Tungsten-Tetraphenylporphyrinate Catalysts V. Dragutan, et al. Metathesis Ring-Chain Equilibrium in Cyclobutene and 1-Methylcyclobutene Systems E. Thorn- Csanyi. Olefin Cyclopropanation or Olefin Metathesis with Late Transition Metal Complexes? A.F. Noels, A. Demonceau. Initiation, Propagation and Termination of Olefin Metathesis Reactions L. Bencze, et al. Synthesis of Membrane Materials by ROMP of Norbornenes E.Sh. Finkelshtein, et al. Olefin Metathesis in Organosilicon Chemistry E.Sh. Finkelshtein. Side Chain Liquid Crystalline Polymers via ROMP. Influence of Content of Mesogenic Groups and Tacticity on the LC Behaviour M. Ungerank, et al. Optically Active Polymers via ROMP of Enantiomerically Pure Monomers F. Stelzer, et al. Synthesis of Well-Defined Graft Copolymers via Coupled Living Anionic and Living Ring Opening Metathesis Polymerisation E. Khosravi. Recent Developments in the Synthesis of Fluorinated Homopolymers and Block Copolymers via Living Ring Opening Metathesis Polymerisation E. Khosravi. Formation of Hydrocarbon and Functionalized Polymers by Acyclic Diene Metathesis (ADMET) Polymerization K.B. Wagener, P.S. Wolfe. A New Synthetic Route to Soluble Conjugated Polymers with Valuable Optical Properties P. Kraxner, E. Thorn-Csanyi. Metathesis Depolymerization Chemistry as a Means of Recycling Polymers to Telechelics and Fine Organic Chemicals K.B. Wagener, et al. Quantitative Determination of the Microstructure and Composition of Crosslinked Rubber Blends H.-D. Luginsland, E. Thorn-Csanyi. Industrial Applications of the Olefin Metathesis Reaction F. Lefebvre, J.-M. Basset. Part II: Alkyne Polymerization. Living Polymerization of Alkynes by Molybdenum Imido Alkylidene Complexes R.R. Schrock. Catalytic Transformation of Alkenes and Alkynes in the Presence of Group 6 Metal Carbonyls T. Szymaska-Buzar. Part III: Molecular Modeling and Alkene Polymerization. Derivatives of Chromocene in Ethylene Polymerisation B.R. Messere, et al. A Possible Mechanism of Polymer Formation from a,b-Unsaturated Carbonyl Compounds under the Influence of Metathesis Catalytic Systems Ch. Jossifov.

Ruthenium-Catalyzed Metathesis Reactions in Organic Synthesis

Abstract: Well-defined ruthenium carbene complexes of type 1 introduced by Grubbs et al. are among the most popular and useful metathesis catalysts known to date. They combine a high activity with an excellent tolerance towards polar functional groups and provide access to carbo- and heterocycles of almost any ring size by ring closing metathesis (RCM) of diene substrates. This includes even medium-sized and macrocyclic rings. The design and mode of action of these and related catalysts will be outlined and their performance will be illustrated by some selected applications to the synthesis of complex natural products. Moreover, some promising developments concerning a new generation of ruthenium-based catalysts (i.a. the allenylidene complexes 2), as well as recent advancements related to the use of supercritical carbon dioxide (scCO2) as reaction medium for RCM, will be discussed.

Metathesis polymerized olefin composites including sized reinforcement material

Abstract: A reinforced polyolefin article is provided which includes a sized reinforcement material incorporated in the article. The article may be prepared by polymerizing a cyclic olefin monomer in the presence of the sizing agent and a metathesis polymerization catalyst which includes ruthenium or osmium.

Synthesis of polymers

Abstract: Repetitive Synthesis of Oligomers (Moore) Transition Metal-Catalyzed Polycondensation and Polyaddition (Heitz) Ring Opening Metathesis Polymerization (Grubbs) Acyclic Diene Metathesis(ADMET) Polymerization (Wagener) Ziegler-Natta Catalysis (Okuda) Living Radical Polymerization (Sawamoto) Anionic Polymerization (Dubois) Cationic Polymerization (Cramail) Emulsion-Dispersion Polymerization (German) Organic-Inorganic Hybrid Polymers (Rehahn) Chiral Polymers (Wulff) Dendrimers and Hyperbranched Polymers (Meijer) Double-Stranded Polymers (Schlueter) Polyrotaxanes (Harada) Polymerization in Organized Media (Stupp) Biocatalytic Routes to Polymers (Kobayashi) Molecular Biological Approach to Biomaterials (Tirrell) The Concept of Modular Chemistry (Antonietti) Synthesis of Cyclic Macromolecules (Lutz)

Cyclic olefin polymerization and relationships between addition and ring opening metathesis polymerization

Abstract: Results of our work concerning: (i) the elucidation of the role of the ionic species [Cp2Ti13CH3]+[Cl·MAO]− and of precursors of alkylidene Cp2TiCH2 species in addition alkene polymerization, (ii) the synthetical strategies for converting the living active titanacyclobutanes into σ-titanocene complexes, and (iii) the evidence for the synthesis of polyethylene polynorbornene di-block copolymer are briefly summarized. 13 C NMR spectra of ethylene–norbornene copolymers, prepared with addition catalysts based on ansa-zirconocenes and methylaluminoxane as cocatalyst, and assignments of comonomer pentads in ethylene–norbornene (EN) copolymers are reported.

An olefin metathesis approach to 36- and 72-membered archaeal macrocyclic membrane lipids

Abstract: An olefin metathesis approach, which has been successfully applied to an efficient synthesis of archaeal 36- and 72-membered macrocyclic membrane lipids (1, 2a, and 2b), is reported. In the presence of a Grubbs' ruthenium−alkylidene complex, RuCl2(CHPh)(PCy3)2 (3), a ring-closing metathesis (RCM) reaction of α,ω-diene 5 efficiently proceeded in 79% yield under high dilution conditions to give 36-membered 6. By changing the reaction conditions, a acyclic diene metathesis (ADM) product 7 was predominantly formed from the same substrate 5. The acyclic product 7 was subsequently subjected to the RCM reaction under high dilution conditions to provide 72-membered compound 8 in 45% yield. Final catalytic hydrogenation of 6 and 8 afforded the 36-membered lipid 1 and a mixture of the 72-membered lipid 2a and 2b, respectively. The present synthetic method appears to be of significant advantage for the synthesis of such giant ring structures of the 36- and 72-membered lipids, because both of the macrocylic lipids ca...

Synthesis of soluble all‐trans oligomers of 2,5‐diheptyloxy‐p‐phenylenevinylene via olefin metathesis

Abstract: In this paper we report on the synthesis of all-trans oligomers of 2,5-diheptyloxy-p-phenylenevinylene (2,5-diheptyloxy-PV) via olefin metathesis condensation of 2,5-diheptyloxy-1,4-divinylbenzene1 (2,5-diheptyloxy-DVB). The preparation of the monomer is also described. The Schrock type molybdenum alkylidene complex Mo(NPhMe2)(CHCMe2Ph)(OCMe[CF3]2)2 was used as metathesis catalyst. The oligomer product obtained was characterized by means of 1H NMR, IR and UV/Vis spectroscopy and gel permeation chromatography.

Effect of alcohols and epoxides on the rate of ROMP of norbornene by a ruthenium trichloride catalyst

Abstract: RuCl3·xH2O has been used commercially in butanol as a solvent for several decades for the ring-opening metathesis polymerization (ROMP) of norbornene. Different alcohols have now been tested as solvents and the effect of added epoxides studied. The systems using benzyl alcohol or its derivatives with RuCl3·xH2O are up to 50 times more active than RuCl3·xH2O/n-butanol. It has been shown that benzyl alcohol reacts with RuCl3 to yield quantitatively benzaldehyde and a ruthenium hydride, which, by reaction with the monomer leads to the ruthenium carbene initiating species. In the case of added epoxides or using tertiary alcohols as solvent, an increase in the rate of polymerization is observed which is attributed to the formation of a ruthenium carbene via an oxaruthenacycle intermediate. Such simple catalytic systems can be used with functionalized norbornenes.