Grubbs Initiator Research Articles

Ring‐Opening Metathesis Polymerization‐Derived Poly(dicyclopentadiene)/Fiber Composites Using Latent Pre‐Catalysts

AbstractThe preparation of basalt and S‐glass fiber‐reinforced poly(dicyclopentadiene) via ring‐opening metathesis polymerization using a thermally latent pre‐catalyst, that is, Mo(N‐3,5‐Me2‐C6H3)(= CH‐(2‐MeO‐C6H4))(IMes)(OTf)2 (1, IMes = 1,3‐dimesitylimidazol‐2‐ylidene; OTf = SO3CF3) is reported. Complementarily, the non‐latent first‐generation Grubbs initiator RuCl2(PPh3)2(CHPh) (2) is used. 2 can be rendered latent by the addition of ppm amounts of triphenylphosphine (PPh3). Both 1 and 2/PPh3 allow the realization of thermally latent single‐component systems with sufficient pot life that do not require pre‐mixing of the individual components shortly before use. The prepared fiber matrix composites are characterized in terms of mechanical, thermal, and chemical stability.

A Hard Templating Approach to Functional Mesoporous Poly(norborn‐2‐ene)‐Based Monolithic Supports

AbstractA hard‐templating method is presented for the synthesis of functional ring‐opening metathesis polymerization (ROMP) derived, poly(norborn‐2‐ene)‐based monolithic supports prepared under solvent‐induced phase separation conditions using the first‐generation Grubbs initiator RuCl2(PCy3)2(CHPh) (1, Cy = cyclohexyl). Norborn‐2‐ene (NBE), 1,4,4a,5,8,8a‐hexahydro‐1,4,5,8‐exo,endo‐dimethanonaphthalene (DMN‐H6) and trimethylolpropane‐tris‐(5‐norbornene‐2‐yl‐carboxylate (TMPTNC) are used as monomers and crosslinkers, respectively. 2‐Propanol and toluene are used as macro‐ and microporogen. Silica (SiO2) nanowires (SNWs) surface‐modified with NBE are used as hard templates. exo,endo‐Norborn‐5‐ene‐2‐ylmethanol (NBE‐CH2OH) is used as functional comonomer. The tailored porogenic system together with the surface‐functionalized SNWs allows for a full dispersion of the SNWs in the polymerization mixture and their incorporation into the monolithic structure during the phase separation process. This way, ROMP‐derived monoliths with pore dimensions of 10–15 nm, specific surface areas up to 3.7 m2 g−1, and pore porosities up to 33% are obtained after removal of the SNWs by chemical etching at room temperature.

Degradable Polyphosphoramidate via Ring-Opening Metathesis Polymerization.

We report the synthesis of a degradable polyphosphoramidate via ring-opening metathesis polymerization (ROMP) with the Grubbs initiator (IMesH2)(C5H5N)2(Cl)2Ru═CHPh. Controlled ROMP of a low ring strain diazaphosphepine-based cyclic olefin was achieved at low temperatures to afford well-defined polymers that readily undergo degradation in acidic conditions via the cleavage of the acid-labile phosphoramidate linkages. The diazaphosphepine monomer was compatible in random and block copolymerizations with phenyl and oligo(ethylene glycol) bearing norbornenes. This approach introduced partial or complete degradability into the polymer backbones. With this chemistry, we accessed amphiphilic poly(diazaphosphepine-norbornene) copolymers that could be used to prepare micellar nanoparticles.

Pulsed-addition ring-opening metathesis polymerization with functional enyne reagents

Functional enyne reagents enable the synthesis of low dispersity heterotelechelic polymers using catalytic quantities of ruthenium initiator.

An Efficient Ring-Closure Method for Preparing Well-Defined Cyclic Polynorbornenes.

An efficient bimolecular ring-closure method is developed to prepare the well-defined cyclic polynorbornenes by combining the living ring-opening metathesis polymerization (ROMP) with the self-accelerating double strain-promoted azide-alkyne cycloaddition (DSPAAC) reaction. In this method, ROMP is used to synthesize the well-defined linear polynorbornenes with both azide terminals by virtue of a N-hydroxysuccinimide-ester-functionalized Grubbs initiator following the modification of polymer end groups. DSPAAC click reaction is then used to ring-close the linear polymer precursors and prepare the corresponding well-defined cyclic polynorbornenes using the sym-dibenzo-1,5-cyclooctadiene-3,7-diyne (DIBOD) as small linkers. The self-accelerating DSPAAC ring-closing reaction facilitates this method to efficiently prepare pure cyclic polynorbornenes in the presence of a molar excess of DIBOD small linkers to the linear polynorbornene precursors. This is the first report to prepare well-defined polynorbornenes with cyclic topology based on the ring-closure strategy for cyclic polymers.

Synthesis, characterization and nanoaggregates of alkyl and triethylene glycol substituted 3,6-carbazolevinylenes homopolymers and block copolymers

Ring strained carbazolephanedienes containing octyl and triethylene glycol chains have been prepared by the McMurry coupling reaction of their corresponding dialdehydes. A series of well-defined carbazolevinylene homopolymers and block polymers containing octyl and triethylene glycol chains have been synthesized through ring-opening metathesis polymerization of the corresponding carbazolephanedienes using the third generation Grubbs initiator. The optical and electrochemical properties and morphologies of the homopolymers and block copolymers with different block ratios such as 1:1, 3:1 and 1:3 have been investigated. The bandgap of the polymers is relatively low (2.64–2.79 eV) and is strongly dependent on the side chains. The carbazolevinylene block copolymers with higher composition of the triethylene glycol substituted carbazolevinylene block showed sphere-like nanoaggregates due to the highly disorder and flexibility of the triethylene glycol chains. This work demonstrated well control of the polymer microstructures with specific nanoaggregates in solid state.

Comparative Reactivity of Me3Si-substituted Norbornene Derivatives in Ring-Opening Metathesis Polymerization

Silyl substituted norbornenes and their derivatives are effective monomers in the synthesis of new prospective polymer materials for gas separation membranes by metathesis and addition polymerization. Comparative activity of norbornenes (NB), norbornadienes (NBD) and tricyclononenes (TCN) with different spatial arrangement of one or two Me3Si substituents in ring-opening metathesis polymerization (ROMP) in the presence of Grubbs initiator Cl2(PCy3)2Ru =CHPh were studied by NMR and GC. It was shown that the rate of the initiation was lower than the propagation for all monomers and the highest activity was inherent to the exo-5-trimethylsilylnorbornene (5-NBSi) and 3-trimethylsilyltricyclononene (3-TCNSi). Disubstituted TCN turned out to be more active than NB having the same number and position of the substituents. The latter were more active than the corresponding NBD. It was found that syn- and anti-isomers of 3-TCNSi polymerized with close rates in contrast to exo- and endo-substituted 5-NBSi, for which polymerization rates were substantially different. Special behavior of monomers with bulky substituents in the geminal position was observed: 5,5-NBSi2 was inactive in the presence of the 1st generation Grubbs initiator, whereas it was polymerized in the presence of the 2nd generation one. Quantum-chemical calculations were in agreement with experimental data and evidenced the influence of energy, electronic and structural properties of the norbornene-type monomers studied on their activity in ROMP.

Alkynol polymerization catalysed by Grubbs-type and Hoveyda–Grubbs ruthenium alkylidene complexes: A computational study

Density functional theory has been applied to study the mechanism of alkynol (3-butyn-2-ol) polymerization by the third generation Grubbs catalyst and the second generation Hoveyda–Grubbs catalyst. Besides typical linear products that can immediately undergo the next insertion step, cyclic products can be also formed, by oxygen-chelation to the ruthenium centre or as less stable rutenacyclobutene species. The initiation stage is predicted to be faster for the Grubbs-type catalyst, compared to the Hoveyda–Grubbs initiator. It is shown that α-insertion is always kinetically preferred over the β-insertion path. On the other hand, the NMR calculations indicate that the experimentally observed 1H NMR signals can be assigned to alkylidene protons of ruthenium species formed in minor amounts by β-insertion. The choice of the DFT method affects significantly the theoretical values of the 1H NMR chemical shifts. The general conclusions about the kinetic preferences do not depend on the density functional used, although the calculated energy profiles are strongly influenced. The simulation of the solvent effect is less significant.

Ring‐opening metathesis polymerization‐derived, lectin‐functionalized monolithic supports for affinity separation of glycoproteins

Lectin-functionalized monolithic columns were prepared within polyether ether ketone (PEEK) columns (150 × 4.6 mm id) via transition metal-catalyzed ring-opening metathesis polymerization of norborn-2-ene (NBE) and trimethylolpropane-tris(5-norbornene-2-carboxylate) (CL) using the first-generation Grubbs initiator RuCl2 (PCy3 )2 (CHPh) (1, Cy = cyclohexyl) in the presence of a macro- and microporogen, i.e. of 2-propanol and toluene. Postsynthesis functionalization was accomplished via in situ grafting of 2,5-dioxopyrrolidin-1-yl-bicyclo[2.2.1]hept-5-ene-2-carboxylate to the surface of the monoliths followed by reaction with α,ω-diamino-poly(ethyleneglycol). The pore structure of the poly(ethyleneglycol)- derivatized monoliths was investigated by electron microscopy and inverse-size exclusion chromatography, respectively. The amino-poly(ethyleneglycol) functionalized monolithic columns were then successfully used for the immobilization of lectin from Lens culinaris hemagglutinin. The thus prepared lectin-functionalized monoliths were applied to the affinity chromatography-based purification of glucose oxidase. The binding capacity of Lens culinaris hemagglutinin-immobilized monolithic column for glucose oxidase was found to be 2.2 mg/column.

Ring-opening metathesis polymerization-derived large-volume monolithic supports for reversed-phase and anion-exchange chromatography of biomolecules

Preparative-scale monolithic columns up to 433.5 mL in volume were prepared via transition metal-catalyzed ring-opening metathesis polymerization (ROMP) from norborn-2-ene (NBE) and trimethylolpropane-tris(5-norbornene-2-carboxylate) (CL) using the 1(st)-generation Grubbs initiator RuCl(2)(PCy(3))(2)(CHPh) (Cy = cyclohexyl) (1) in the presence of a macro- and microporogen, i.e. of 2-propanol and toluene. To prepare large-volume monoliths, bulk polymerizations were completed within borosilicate or PEEK column formats with diameters in the range of 3 to 49 mm. The pore structure of the large-volume monoliths was investigated by electron microscopy and inverse-size exclusion chromatography (ISEC), respectively. Monolithic columns with inner diameters (I.D.s) in the range of 10-49 mm were tested for the separation of a mixture of five proteins, i.e., insulin, cytochrome C, lysozyme, conalbumin, and β-lactoglobulin. Preparative separation of these proteins was achieved within less than 12 min in a 433.5 mL monolithic column by applying gradient elution in the RP-HPLC mode. Furthermore, weak and strong anion exchangers were prepared via post-synthesis grafting of bicyclo[2.2.1]hept-5-en-2-yl-methyl-N,N-dimethylammonium hydrochloride (4) and bicyclo[2.2.1]hept-5-en-2-ylmethyl-N,N,N-trimethylammonium iodide (5), respectively. The weak and strong anion exchangers were used for the preparative-scale separation of 5'-phosphorylated oligodeoxythymidylic acid fragments of d[pT](12-18) at pH values ranging from 5 to 9.

UV‐ and thermally triggered ring‐opening metathesis polymerization for the spatially resolved functionalization of polymeric monolithic devices

AbstractPorous polymeric monolithic supports were prepared via electron beam‐triggered free radical polymerization using a mixture of ethyl methacrylate and trimethylolpropane triacrylate in 2‐propanol, 1‐dodecanol and toluene. Bicyclo[2.2.1]hept‐5‐en‐2‐ylmethyl acrylate (1) was grafted onto these monolithic supports in a spatially resolved way with the aid of masks using both electron beam‐ (EB) and UV‐triggered free radical polymerization. The thus immobilized norborn‐2‐ene‐containing graft polymers were further treated with the 2nd‐generation Grubbs initiator, i.e., RuCl2(PCy3)(IMesH2)(CHPh) (4) (IMesH2 = 1,3‐dimesitylimidazolin‐2‐ylidene), and then reacted with bicyclo[2.2.1]hept‐5‐en‐2‐ylmethyl pyrene‐1‐carboxylate (2). Alternatively, monoliths completely grafted with poly‐1 were surface grafted with 2 in a spatially resolved way in the presence of a latent, UV‐triggerable precatalyst, i.e., [Ru(IMesH2)(CF3COO)(t‐BuCN)4+ CF3COO−] (5). Finally, to demonstrate the utility of this chemistry, a 2nd‐generation Grubbs initiator‐based approach was used to prepare a trypsin‐functionalized monolith‐containing chip device that allowed for the online digestion of N‐α‐benzoyl‐L‐argininethylester hydrochloride. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

ROMP-Derived cyclooctene-based monolithic polymeric materials reinforced with inorganic nanoparticles for applications in tissue engineering.

Porous monolithic inorganic/polymeric hybrid materials have been prepared via ring-opening metathesis copolymerization starting from a highly polar monomer, i.e., cis-5-cyclooctene-trans-1,2-diol and a 7-oxanorborn-2-ene-derived cross-linker in the presence of porogenic solvents and two types of inorganic nanoparticles (i.e., CaCO3 and calcium hydroxyapatite, respectively) using the third-generation Grubbs initiator RuCl2(Py)2(IMesH2)(CHPh). The physico-chemical properties of the monolithic materials, such as pore size distribution and microhardness were studied with regard to the nanoparticle type and content. Moreover, the reinforced monoliths were tested for the possible use as scaffold materials in tissue engineering, by carrying out cell cultivation experiments with human adipose tissue-derived stromal cells.

Ring‐Opening Metathesis Polymerization Based Pore‐Size‐Selective Functionalization of Glycidyl Methacrylate Based Monolithic Media: Access to Size‐Stable Nanoparticles for Ligand‐Free Metal Catalysis

Monolithic polymeric supports have been prepared by electron-beam-triggered free-radical polymerization using a mixture of glycidyl methacrylate and trimethylolpropane triacrylate in 2-propanol, 1-dodecanol, and toluene. Under appropriate conditions, phase separation occurred, which resulted in the formation of a porous monolithic matrix that was characterized by large (convective) pores in the 30 μm range as well as pores of <600 nm. The epoxy groups in pores of >7 nm were hydrolyzed by using poly(styrenesulfonic acid) (Mw = 69,400 g mol(-1), PDI=2.4). The remaining epoxy groups inside pores of <7 nm were subjected to aminolysis with norborn-5-en-2-ylmethylamine (2) and provided covalently bound norborn-2-ene (NBE) groups inside these pores. These NBE groups were then treated with the first-generation Grubbs initiator [RuCl2 (PCy3 )2 (CHPh)]. These immobilized Ru-alkylidenes were further used for the surface modification of the small pores by a grafting approach. A series of monomers, that is, 7-oxanorborn-5-ene-2,3-dicarboxylic anhydride (3), norborn-5-ene-2,3-dicarboxylic anhydride (4), N,N-di-2-pyridyl-7-oxanorborn-5-ene-2-carboxylic amide (5), N,N-di-2-pyridylnorborn-5-ene-2-carboxamide (6), N-[2-(dimethylamino)ethyl]bicyclo[2.2.1]hept-5-ene-2-carboxamide (7), and dimethyl bicyclo[2.2.1]hept-5-en-2-ylphosphonate (8), were used for this purpose. Finally, monoliths functionalized with poly-5 graft polymers were used to permanently immobilize Pd(2+) and Pt(4+), respectively, inside the pores. After reduction, metal nanoparticles 2 nm in diameter were formed. The palladium-nanoparticle-loaded monoliths were used in both Heck- and Suzuki-type coupling reactions achieving turnover numbers of up to 167,000 and 63,000, respectively.

Total Synthesis of Amphidinolide X and Its 12Z-Isomer by Formation of the C12-C13 Trisubstituted Double Bond via Ring-Closing Metathesis

Amphidinolide X, a 16-membered cytotoxic macro-diolide, and its 12 Z-isomer have been synthesized via ring-closing metathesis (RCM) for assembling the C12-C13 trisubstituted double bond. A 29:71 E/ Z mixture was obtained from the SECO substrate appended with a bulky C8-ODPS group in 50-65% combined yields by using 20 mol% of the second-generation Grubbs initiator and the corresponding indenylidene ruthenium complex. Amphidinolide X and 12 Z-isomer exhibit similar cytotoxicity (IC 50 : 7.6-13.9 μg/mL) against A549, KB, and HL60 cell lines.

Remarkable alternating effect in metathesis copolymerization of norbornene and cyclopentene using modified Grubbs ruthenium initiators

Abstract High trans and mainly cis directing Grubbs Ru initiators, I–III, and IV, respectively have been investigated as catalysts for metathesis copolymerization of norbornene and cyclopentene. When the Lewis acid, MoCl5 or WCl6, is added to these Lewis bases initiators, I–III, a cage effect develops such that the polymers become alternating caused by the severe or almost total denial of access of norbornene to the propagating metallacarbenes. Addition of ethers destroys the cages and removes the effect. In marked contrast the N-heterocyclic ligand Grubbs initiator, IV, does not show the effect, as addition of MoCl5 only seems to retard the overall reaction, but does not change the copolymer composition.

A New and Highly Efficient Grubbs Initiator for Ring-Opening Metathesis Polymerization

A New and Highly Efficient Grubbs Initiator for Ring-Opening Metathesis Polymerization

An Enyne Metathesis/(4 + 2)- Dimerization Route to (±)-Differolide

[formula: see text] A concise total synthesis of (+/-)-differolide (1) has been achieved. 2-Vinylbutenolide (2) was prepared by enyne metathesis of allyl propynoate (3) using the Grubbs initiator 4. This reaction was examined by 1H NMR spectroscopy, which led to the hypothesis that low concentration of ruthenium species and high concentration of enyne substrate would be advantageous. Accordingly, slow addition of 4 to solutions of enyne 3 was found to be beneficial. Spontaneous dimerization of 2 gave (+/-)-differolide (1) and an isomer.

Synthesis of a C(1)-C(14)-containing fragment of callipeltoside A.

[formula: see text] A C(1)-C(14)-containing fragment of callipeltoside A (1, Scheme 1) was synthesized efficiently via a dianion aldol coupling reaction between aldehyde 2 and ketoester 3. A surprising lack of reactivity between the alkenes in 13 and the Grubbs initiator 15 was encountered. An equally surprising rate acceleration of the reaction between 15 and allylic alcohols (alk-1-en-3-ols) as well as their subsequent cleavage to methyl ketones was discovered. In situ 1H NMR analysis has proven to be a very useful tool for monitoring RCM reactions of complex substrates such as 13.