Presence Of Grubbs Catalyst Research Articles

Synthesis of high-molecular weight poly(1,1-dimethyl-1-silapentene) by olefin metathesis polymerization in the presence of Grubbs catalysts

Heterochain polycarbosilanes are well-known materials possessed important properties. Some of their applications, such as gas separation membranes, require polymers with high molecular weight that provide good film-forming and mechanical properties. In this research, the synthesis of poly(1,1-dimethyl-1-silapentene) via the ring-opening metathesis polymerization (ROMP) of 1,1-dimethyl-1-silacyclopentene and the acyclic dienes metathesis (ADMET) of diallyldimethylsilane mediated by Ru-carbene Grubbs complexes 1st - 3rd generations as well as Hoveyda-Grubbs 2nd generation catalyst were studied for the first time. High molecular weight poly(1,1-dimethyl-1-silapentene) was synthesized by ROMP of 1,1-dimethyl-1-silacyclopentene. Varying the type and loading catalyst, temperature and monomer concentration, we obtained poly(1,1-dimethyl-1-silapentene) with Mw = 100–143 kDa, which is significantly higher (5–7 times) than that reached previously by olefin metathesis polymerization. The activities of 1,1-dimethyl-1-silacyclopentene and cyclopentene in ROMP were compared using 1H NMR monitoring the conversion of their double bonds. The ADMET polymerization of diallyldimethylsilane led to oligomers with the average polymerization degree not exceeded 4.4.

Reversible Activity Modulation of Surface-Attached Grubbs Second Generation Type Catalysts Using Redox-Responsive Polymers

Redox-responsive polyvinylferrocene-grafted silica nanoparticles have been used for modulating the catalytic activity of surface-attached Grubbs second generation type catalysts for the ring-opening metathesis polymerization (ROMP) of norbornene monomer. A facile and very efficient protocol for the modification of living polyvinylferrocene chains was developed to introduce a suitable functional group for the intended “grafting onto” approach. Grafted particles were characterized by using TEM, SEM/energy dispersive X-ray spectroscopy (EDS), XPS, small-angle X-ray scattering (SAXS), dynamic light scattering (DLS), and cyclic voltammetry, revealing both the presence of redox-responsive polymers and the presence of Grubbs catalyst in the particle exterior. Chemical oxidation protocols for immobilized polymers were applied to deactivate surface-attached catalysts in ROMP protocols, while chemical in situ reduction immediately led to catalyst’s reactivation.

5-{5-(bicyclo[2.2.1]hept-2-enyl)hydroxymethyl}-3,6-di-tert-butylo-benzoquinone and related polymers. Synthesis and some properties

A norbornene-containing ortho-quinone, 5-{5-(bicyclo[2.2.1]hept-2-enyl)hydroxymethyl)-3,6-ditert-butyl-o-benzoquinone, was synthesized by the nucleophilic addition of 5-(hydroxymethyl)bicyclo[2.2.1] hept-2-ene to 3,6-di-tert-butyl-o-benzoquinone. The structure of the compound was established by the X-ray analysis. The monomer obtained undergoes metathesis polymerization in the presence of Grubbs catalyst of the third generation with the formation of polynorbornene containing quinone fragments in the side chains.

Metathesis transformations of unsaturated derivatives of β-diketones

Abstract Selected β-diketones bearing unsaturated derivatives have been demonstrated to undergo homo-metathesis and cross-metathesis with selected olefins in the presence of Grubbs catalysts. The reactions led to respective homo- and cross-metathesis products mainly with good yields and selectivities.

Highly efficient synthesis of [3]rotaxane assisted by preorganisation of pseudorotaxane using bis(crown ether)s

The tether-assisted synthesis of [3]rotaxane by olefin metathesis has been studied in detail. Bis(crown ether)s, in which two crown ethers are connected by a linker, were threaded onto ammonium salts bearing a terminal olefin to form pseudorotaxanes. The pseudorotaxanes were converted into tethered rotaxanes in the presence of Grubbs catalyst, followed by removal of the linkers to produce [3]rotaxanes in excellent yields. Preorganisation of the two reactive ends has led to a great improvement in the yield of [3]rotaxanes. The ring strain of the tethered rotaxanes and the flexibility of the pseudorotaxanes were responsible for the formation of the tethered rotaxanes.

Efficient synthesis of 19–31 membered macrocyclic tetralactones via ring closing metathesis in ionic liquids

The ring closing metathesis reaction in the presence of Grubbs catalyst was demonstrated using several ionic liquids to synthesize a range of macrocyclic tetralactones having ring size of 19 to 31 membered with different spacers. The ionic liquid [mmim][PF 6 ] was found to be an excellent solvent and the recovery of the catalyst was demonstrated. X-ray analysis of a representative macrocyclic tetralactone was also reported.

ChemInform Abstract: Cross‐Metathesis of Vinylsubstituted Organosilicon Derivatives with Olefins and Dienes in the Presence of Grubbs Catalysts

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ATRP−RCM Synthesis of Cyclic Diblock Copolymers

A versatile synthetic means for cyclic diblock copolymers has been developed by the combination of atom transfer radical polymerization (ATRP) and ring-closing metathesis (RCM) techniques. Thus, first, an A−B type allyl-telechelic diblock copolymer comprised of two different acrylate ester segments, i.e., poly(methyl acrylate)-b-poly(n-butyl acrylate), poly(MA)-b-poly(BA), was prepared via the ATRP of MA, followed by the addition of the second monomer, BA, with allyl bromide as an initiator and with allyltributylstannane as an end-capping reagent, respectively. Alternatively, an A−B−A type allyl-telechelic triblock copolymer comprised of poly(BA) and poly(ethylene oxide), poly(EO), segments was prepared via the ATRP of BA using a poly(EO) macroinitiator having 2-bromoisobutyryl end groups, followed by the end-capping reaction with allyltributylstannane. The subsequent RCM of the allyl-telechelic block copolymers under dilution in the presence of Grubbs catalyst could afford the corresponding A−B type cyclic diblock copolymers.

Regioselective Synthesis of Oxepin and Oxocin Annulated Quinoline Heterocycles by Ring-Closing Metathesis

Regioselective synthesis of oxepin and oxocin annulated quinoline heterocycles by the combination of Claisen rearrangement and ring-closing metathesis reaction is described. The ring-closing metathesis (RCM) and ring-closing enyne metathesis (RCEM) proceeded smoothly in the presence of Grubbs catalyst A or B in toluene under nitrogen atmosphere without deactivation of the basic quinoline nitrogen. Keywords: Ring-closing metathesis, oxepine, oxocine, quinoline derivatives, Grubb's catalyst

Cross-metathesis of vinyl-substituted linear and cyclic siloxanes with olefins in the presence of Grubbs catalysts

Efficient cross-metathesis (CM) of linear and cyclic vinyl-substituted oligosiloxanes with selected olefins in the presence of Grubbs type ruthenium alkylidene complexes is described. Treatment of styrene or 4-substituted styrenes with vinyl group at siloxane skeleton results in the formation of respective cross-metathesis products with good yields and selectivities.

Ru-catalyzed metathesis of octadienylether xyloside

The reaction of the octadienylether of xylosyle and of its peracetylated form in the presence of Grubbs catalysts has led to O-allyl carbohydrates, and from the protected carbohydrate, to the bolaform with a C4 tether. The concomitant formation of cyclopentene, highlighted from analysis of the crude reaction by mass spectroscopy, led to propose a mechanistic scheme involving both double bonds of the substrate.

Thermal analysis of ring‐opening metathesis polymerized healing agents

AbstractDicyclopentadiene (DCPD) and 5‐ethylidene‐2‐norbornene (ENB) and their mixtures were analyzed after ring‐opening metathesis polymerization (ROMP) in the presence of Grubbs catalyst as potential candidate healing agents for self‐healing composite materials using two complementary methods, rotational dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). Following isothermal DMA measurements at room temperature (RT = 25 °C) for 120 min, two consecutive dynamic temperature scan experiments were performed for each system. In the first dynamic temperature scans, there was an initial downward peak slightly above RT in the storage modulus versus temperature curve for samples with relatively slower reaction rates (i.e., DCPD and DCPD‐rich mixtures or low catalyst loadings) due to a combination of the glass transition followed by further residual reaction. However, no or negligible downward peaks were observed for the highly reactive ENB and ENB‐rich samples even at much lower catalyst loadings. Implications of the substantial decrease in storage modulus just above RT for the slowly reacting systems are discussed for healing of damage in composite materials at elevated temperatures. The maximum glass transition temperatures (Tg∞) from DMA of the fully cured samples were determined to be approximately 160 °C for DCPD and 120 °C for ENB, decreasing linearly with increased ENB in the blends. The glass transitions and further residual reactions above the glass transitions were confirmed by DSC. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1771–1780, 2007

Long Chain‐Substituted and Triply Functionalized Molecular Knots – Synthesis, Topological Chirality and Monolayer Formation

AbstractNew topological chiral molecular knots (knotanes) 3a–6 of the amide type were substituted with long aliphatic side chains (butyloxy, hexyloxy, octenyloxy, decyloxy) and with p‐bromobenzyloxy and oligoethylene glycol ether units, which resulted in improved solubility and enhanced potential for racemate separation. In consequence, the knotanes with longer substituted chains could be separated even on commercially available noncovalently bound chiral stationary phases. The (p‐bromobenzyloxy)‐knotane 6 and the octenyloxy‐knotane 4 were synthesized with the intention of using their functional sidechains in further reactions, 6 being used in Suzuki‐type reactions, while 4 was consequently allowed to react in the presence of Grubbs catalyst in metathesis reactions. The achieved solubility allowed us to test the abilities of the alkyl chain‐substituted knotanes 3a–c and the (p‐bromobenzyloxy)‐knotane 6 to form Langmuir–Blodgett films. The assemblies were investigated on mica by AFM technique. A key point of focus was the (topological) chirality of the long chain‐substituted knotanes. To address this point, the racemates were enantioseparated by HPLC on various chiral phases, and the obtained pure enantiomers were found to exhibit pronounced Cotton effects in their circular dichroism spectra. The absolute configurations of all new knots were derived by comparison with the unsubstituted knot. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

A Convenient Synthesis of Medium‐Sized Lactams Through RCM Reaction of Oxyoxazolidinones.

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Cross-metathesis of divinylsubstituted silanes and disiloxanes in the presence of Grubbs catalysts

Efficient cross-metathesis of divinylsilanes and divinyldisiloxanes, carrying different electron-withdrawing substituents at silicon, with selected olefins in the presence of the first and second generation Grubbs catalyst and Hoveyda–Grubbs catalyst is described. The reaction was proved to be a valuable method for synthesis of unsaturated organosilicon derivatives and a model for the study of synthesis of oligo- and polymeric products via ADMET copolymerization of divinylsubstituted silanes and disiloxanes with dienes.

Stereoselective Syntheses of (E)-1-Boryl-3-(silyl)propenes via Ruthenium-­Catalyzed Cross-Metathesis and Cross-Coupling Reactions

A general and mostly highly stereoselective method for effective synthesis of 1-boryl-3-(silyl)propenes via one-step ­catalytic processes, i.e. silylative coupling of vinylsilanes with allyl boronates, borylative coupling of vinyl boronates with allylsilanes catalysed by [RuHCl(CO)(PCy3)2] and cross-metathesis of respective derivatives in the presence of Grubbs catalysts, is described.

Characterization of diene monomers as healing agents for autonomic damage repair

AbstractFor effective autonomic healing of damaged polymers and composites, it is essential to understand how the encapsulated healing agent behaves during and after cure. In this study, two different diene monomers [dicyclopentadiene (DCPD), 5‐ethylidene‐2‐norbornene (ENB)] and their blends were investigated as candidate self‐healing agents, using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). DSC experiments for samples showed that DCPD has a melting transition while the blends and ENB have no melting in the temperature range measured. Samples for DMA were prepared and tested by two different methods in the presence of Grubbs catalyst. In the first case (method I), monomers were mixed with the catalyst directly. In the second case (method II), the catalyst was mixed with an epoxy/amine system and cured into a film that was polished to expose the catalyst. The cure behavior of monomer samples was examined on the epoxy/catalyst film. Method II is considered to be a simulative experiment, which can occur in a real situation for damaged epoxy matrix composite. It was found that acceleration of cure reaction and reduction of catalyst concentration is possible by blending DCPD with ENB from method I. Storage modulus (G′) value after cure in method II showed that a DCPD : ENB blend ratio of 1 : 3 reached the highest G′ value at shorter cure time and lower catalyst levels than other monomer combinations. DCPD and ENB are presumably responsible for increases in rigidity and reactivity, respectively. This may improve the healing efficiency in autonomic damage repairing applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1266–1272, 2006

Synthesis and structural characterization of trans-tactic siloxylene-vinylene- p-phenylene polymers via ADMET copolymerization and silylative coupling (SC) polycondensation

The first trans-tactic stereo-regular vinylene-siloxylene- p-phenylene copolymer 1 with perfect vinylsiloxane linkage was obtained via acyclic diene metathesis copolymerization of divinyltetraethoxydisiloxane with 1,4-divinylbenzene (DVB) in the presence of Grubbs catalyst. The similar trans-tactic copolymers 2 and 3 but with no consecutive vinylsiloxane linkage was also prepared by silylative coupling copolycondensation of DVB with divinyltetra(methyl,ethoxy)disiloxane catalyzed by [Ru(H)(Cl)(CO)(PCy 3) 2].