First-generation Grubbs Catalyst Research Articles

Design and Preparation of Ethylene Fluorescence Probes Based on Arylolefins and Grubbs Catalysts.

To detect the plant hormone ethylene, three arylolefins were employed to react with ethylene based on olefin metathesis. In this study, three fluorescence probes were successfully prepared using a first-generation Grubbs catalyst (G-1) and arylolefin with terminal vinyl groups. The probes were characterized using various techniques, including UV-vis, fluorescence, FT-IR, 1H NMR, 13C NMR, and 31P NMR spectroscopies and HRMS. The probes exhibited an emission maximum at 394 nm and showed excellent ethylene response. The detection limits for the probes were calculated to be 0.128, 0.074, and 0.188 μL/mL (3σ), respectively, based on fluorescence stimulation by ethylene gas. Additionally, the YGTZ-2 probe was used to detect ethylene gas during the storage process of tomatoes. This work expands the application of arylolefin in ethylene detection and provides a foundation for the development of economic, rapid, and convenient photosensitive sensors for ethylene in the future.

ESTUDO ONE-POT DA APLICAÇÃO DO CATALISADOR DE GRUBBS DE PRIMEIRA GERAÇÃO EM REAÇÕES DE METÁTESE DA PIPERINA E EUGENOL: A INFLUÊNCIA DA LIGAÇÃO DUPLA TERMINAL

ONE-POT STUDY OF THE APPLICATION OF CATALYST FIRST-GENERATION GRUBBS IN METATHESIS REACTIONS OF PIPERINE AND EUGENOL: THE INFLUENCE OF THE DOUBLE- BOND TERMINAL. In this paper, the piperine (PIP) and eugenol (EUG) organic compounds were used as substrates in olefin metathesis reactions catalyzed by first-generation Grubbs catalyst (G1) – [RuCl2(PCy3)2(=CHPh)], Cy is cyclohexyl and Ph is phenyl, in a one-pot system. The reactions occurred at 50 ºC, for 24, 48, or 96 h using the two substrates simultaneously in the ratio Ru:PIP:EUG of 1:1:1 and 1:10:10 mol. The results were evaluated by GC-MS, discussed in terms of the electronic and steric characteristics of the G1, and the structural proprieties of the substrates. In the Ru:PIP:EUG ratio of 1:1:1 mol, a dimeric species was observed for the olefin metathesis of EUG, in all time studied and in an additional experiment at 70 ºC for 48 h. When the Ru:PIP:EUG ratio was 1:10:10 mol, this dimer was not observed. Isomerization processes also were observed at all temperatures and catalyst:substrates ratio. The reaction yield increased with the raise of substrates amount. There was no cross-metathesis reaction. This fact was attributed to the chelating effect of the double coordination of the PIP to the catalyst.

Multiblock Copolymers of Norbornene and Cyclododecene: Chain Structure and Properties.

We investigate the structure–property relations of the multiblock copolymers of norbornene with cyclododecene synthesized via the macromolecular cross-metathesis reaction between amorphous polynorbornene and semicrystalline polydodecenamer in the presence of the first-generation Grubbs catalyst. By adjusting the reaction time, catalyst amount, and composition of the initial system, we obtain a set of statistical multiblock copolymers that differ in the composition and average length of norbornene and dodecenylene unit sequences. Structural, thermal, and mechanical characterization of the copolymers with NMR, XRD, DSC (including thermal fractionation by successive self-nucleation and annealing), and rotational rheology allows us to relate the reaction conditions to the average length of crystallizable unit sequences, thicknesses of corresponding lamellas, and temperatures of their melting. We demonstrate that isolated dodecenylene units can be incorporated into crystalline lamellas so that even nearly random copolymers should retain crystallinity. Weak high-temperature endotherms observed in the multiblock copolymers of norbornene with cyclododecene and other cycloolefins could indicate that the corresponding systems are microphase-separated in the melt state.

Stereospecific Synthesis of Poly(methylene-E-vinylene) by Ring Opening Metathesis Polymerization of Substituted Cyclopropene Using Grubbs Catalysts

A first-generation Grubbs catalyst has been shown to not only catalyze the ring opening metathesis polymerization (ROMP) of cyclopropene derivatives but also differentiate E- and Z-double bonds in ...

Cross-Metathesis between Polynorbornene and Poly(5,6-epoxy-1-octenamer)

The macromolecular reaction of interchain cross-metathesis between polynorbornene and poly(5,6-epoxy-1-octenamer) in the presence of the first-generation Grubbs catalyst is studied. Chemically stable poly(5,6-epoxy-1-octenamer) is obtained through metathesis polymerization of 5,6-epoxycyclooct-1-ene with the second-generation Grubbs ruthenium catalyst. New random multiblock copolymers of norbornene and 5,6-epoxycyclooct-1-ene with different average block lengths determined by the reaction time, solvent type, and concentrations of the catalyst and initial homopolymers are synthesized and characterized by NMR, GPC, and DSC. Despite a distance between the epoxy substituent and the reaction center (double bond), poly(5,6-epoxy-1-octenamer) shows a lower activity in the cross-metathesis reaction with polynorbornene compared to unsubstituted polyoctenamer. The influence of epoxy groups present in the backbones of homopolymer and norbornene–cyclooctene multiblock copolymers on their thermal characteristics is studied. It is shown that the glass transition and melting temperatures increase with the concentration of epoxy groups upon the incorporation of an oxirane fragment into both homopolymers and copolymers. The crystallinity of poly(5,6-epoxy-1-octenamer) increases with the content of trans-С=С bonds in the polymer.

Synthesis and Gas-Separation Properties of New Silacyclopentane-Containing Polynorbornenes

Previously, it was shown that the presence of bulky silicon-containing substituents in the monomer unit of metathesis polynorbornenes hinders the postmodification and, in particular, exhaustive gem-difluorocyclopropanation of main-chain double bonds. In order to reduce the double bonds shielding by substituents, a new polynorbornene with a dimethylsilacyclopentane fragment in the monomer unit, poly(4,4-dimethyltricyclo[5.2.1.02,6]-4-siladec-8-ene) (PNBCP), is synthesized, in which the silylmethyl group is moved further from the double bonds. In order to achieve this, the monomer 4,4-dimethyltricyclo[5.2.1.02,6]-4-siladec-8-ene (NBCP) is first obtained via the diene condensation of 1,3-cyclopentadiene and 1,1-dichlorosilacyclopent-3-ene with following methylation of Si-Cl bonds. NBCP is polymerized by the ring-opening metathesis scheme in the presence of the first-generation Grubbs catalyst, Cl2(PCy3)2Ru=CHPh. The new polymer PNBCP is obtained in a yield of 99–100% and characterized. The gem-difluorocyclopropanation of PNBCP with difluorocarbene, generated during the thermolysis of sodium chlorofluoroacetate, is studied; the conditions for exhaustive replacement of double bonds by gem-difluorocyclopropane are found. It is shown that PNBCP is more active in postmodification compared to poly(5-trimethylsilyl)norbornene but is less active than unsubstituted polynorbornene. It is demonstrated that the introduction of the silacyclopentane fragment into the monomer unit of the metathesis polynorbornene and its subsequent difluorocyclopropanation lead to increase in gas permeability and diffusion and cause a slight decrease in ideal separation selectivities. It is found that gem-difluorocyclopropanation increases the glass transition temperature of PNBCP by 60°C and makes its films stable when stored in air.

Palladium- and Ruthenium-Catalyzed Intramolecular Carbene CAr -H Functionalization of γ-Amino-α-diazoesters for the Synthesis of Tetrahydroquinolines.

A synthetic method to prepare tetrahydroquinoline-4-carboxylic acid esters has been developed through the transition-metal-catalyzed intramolecular aromatic C-H functionalization of α-diazoesters. Both [{Pd(IMes)(NQ)}2 ] (IMes=1,3-dimesitylimidazol-2-ylidene, NQ=1,4-naphthoquinone) and the first-generation Grubbs catalyst proved effective for this purpose. The ruthenium catalyst was found to be the most versatile, although in a few cases the palladium complex afforded better yields or selectivities. According to DFT calculations, Pd0 - and RuII -catalyzed sp2 -CAr -H functionalization proceeds through different reaction mechanisms. Thus, the Pd0 -catalyzed reaction involves a Pd-mediated 1,6-H migration from the sp2 -CAr -H bond to the carbene carbon atom, followed by a reductive elimination process. In contrast, electrophilic addition of the ruthenacarbene intermediate to the aromatic ring and subsequent 1,2-proton migration are operative in the Grubbs catalyst promoted reaction.

Synthesis and Metathesis Polymerization of Cycloadduct Based on Quadricyclane and Perfluoro-1-octene

Previously undescribed norbornene monomer 3,3,4-trifluoro-4-perfluorohexyltricyclononene-7 is synthesized by the [2+2+2] cycloaddition reaction. The monomer is involved in the ring-opening polymerization metathesis in the presence of the first-generation Grubbs catalyst to give rise to the amorphous, glassy unsaturated polymer. The gas-transport properties of the metathesis polymer is studied, the gas permeability and diffusion coefficients for a wide range of gases (He, H2, O2, N2, CO2, CH4) are determined, and the solubility coefficients of gases in this polymer are calculated.

New Adhesive Materials Based on Silicon-Substituted Polynorbornenes

Two metathesis homopolymers with tri(n-propoxy)silyl and tri(n-butoxy)silyl side substituents are synthesized, and their adhesive properties are investigated. High-molecular-weight polymers are prepared in the presence of the first-generation Grubbs catalyst in a good yield. Adhesive properties are studied by the probe tack method at different temperatures. Using the example of the studied polymers, for the first time, it is shown that pressure-sensitive adhesives can be obtained on the basis of polynorbornenes. The effect of the length of the side silicon substituent on the work of adhesion is evaluated.

Epoxidation of Multiblock Copolymers of Norbornene and Cyclooctene

The epoxidation of double bonds in random multiblock copolymers of norbornene and cyclooctene is studied for the first time. The initial copolymers with different composition and average block length are synthesized via the cross-metathesis reaction between polynorbornene and polycyclooctene in the presence of the first-generation Grubbs catalyst. New multiblock copolymers containing oxirane fragments in the backbone are obtained with a yield of 85–92% through epoxidation conducted under the action of m-chloroperbenzoic acid in toluene. The kinetics of epoxidation of polynorbornene, polycyclooctene, and their multiblock copolymers in deuterochloroform and deuterobenzene is investigated via the in situ monitoring of transformation of double bonds using 1Н NMR spectroscopy. It is shown that on the whole the modification of cyclooctene units occurs more easily in copolymers than that in the homopolymer. The thermal properties of epoxidized homo- and copolymers are examined. It is found that upon epoxidation the glass-transition temperature and the melting temperature of multiblock copolymers increase by 40–50 and 20–30°С, respectively, wherein the degree of crystallinity and the temperature of melting grow with the length of the cyclooctene block.

Synthesis and Properties of Metathesis Polymer Based on 3-Silatranyltricyclo[4.2.1.02.5]non-7-ene

A new metathesis polynorbornene containing bulky and reactive silatrane side groups is synthesized, and its gas-transport properties are investigated. The metathesis polymerization of 3-silatranyltricyclo[ 4.2.1.02.5]non-7-ene is conducted in the presence of the first-generation Grubbs catalyst. The homopolymer is obtained with a nearly quantitative yield of 98% and a molecular mass of Mw = 1.3 × 106 (Ð = 3.7). According to X-ray phase analysis, the homopolymer is amorphous and its glass-transition temperature is 232°С (DSC). The gas permeability of the metathesis polymer for a set of gases, including He, H2, O2, N2, CO2, and CH4, is investigated, and the corresponding diffusion and solubility coefficients are determined.

Unusual Superior Activity of the First Generation Grubbs Catalyst in Cascade Olefin Metathesis Polymerization.

Recently, we reported a new cascade ring-opening/closing metathesis polymerization of monomers containing two cyclopentene moieties. Several Ru catalysts were tested, but the best polymerization results were unexpectedly obtained using the first-generation Grubbs catalyst (G1). This was puzzling since the second- and third-generation Grubbs catalysts are well-known for their higher activities compared to G1. In order to explain the unique and superior activity of G1, we conducted a series of kinetics experiments for the polymerization of 3,3'-oxydicyclopent-1-ene, a representative monomer of this cascade polymerization, as well as the competition polymerization with cycloheptene using the various Grubbs catalysts. Based on our results, we propose a model in which the differences in the steric hindrance between the different ligands and the monomer determine the selectivity of the catalyst approach to the monomer and, therefore, the extent to which the productive pathway leads to successful cascade polymerization. In short, G1 with the smaller ligand showed a high preference for the productive pathway.

Successful Cyclopolymerization of 1,6-Heptadiynes Using First-Generation Grubbs Catalyst Twenty Years after Its Invention: Revealing a Comprehensive Picture of Cyclopolymerization Using Grubbs Catalysts

Cyclopolymerization (CP) of 1,6-heptadiynes using olefin metathesis catalysts is a useful method for producing various conjugated polyenes. Unfortunately, commercially available user-friendly Grubbs catalysts have long been known to be inactive toward CP. However, recent mechanistic studies revealed that the problem did not lie with the intrinsic activities of Grubbs catalysts but the stability of the propagating carbenes, as decomposed carbene species catalyzed a [2 + 2 + 2] cycloaddition side reaction instead of CP. Fortunately, by adding weakly coordinating ligands such as pyridines as stabilizers, a highly active and fast-initiating third-generation Grubbs catalyst could successfully promote living CP. However, there was no report of CP using the much cheaper but less active first-generation Grubbs catalyst (G1), which has been widely used for more than 20 years. Believing that G1 should also be able to catalyze CP, we came up with three strategies to enhance the activity of G1 toward CP. By categoriz...

Synthesis and dynamic behaviour of a dimeric ruthenium benzylidene complex bearing a truncated N-heterocyclic carbene ligand

Described herein is the reaction of the first-generation Grubbs catalyst RuCl2(PCy3)2(=CHPh) (GI) with free IMe4 (1,3,4,5-tetramethylimidazol-2-ylidene), in which the N-mesityl groups commonly present in Ru-NHC metathesis catalysts are truncated to N-Me (NHC = N-heterocyclic carbene). Treatment of GI with IMe4 (1–2.1 equiv) effects displacement of both PCy3 ligands, but does not terminate at the mono-ruthenium species RuCl2(IMe4)2(=CHPh) Ru-3. Instead, dimerization occurs to afford [Ru2(μ-Cl)3(IMe4)4(=CHPh)2]Cl Ru-4, the structure of which was confirmed by crystallographic analysis. A molecular dynamics study of Ru-4 indicated rapid rotation of both the NHC and the benzylidene ligands, accounting for the observation of multiple benzylidene signals in the solution 1H NMR spectrum of Ru-4.

Ring-opening metathesis polymerization (ROMP) of fullerene-containing monomers in the presence of a first-generation Grubbs catalyst

New norbornene-type monomers containing covalently bound C60 fullerene have been obtained. In the presence of the 1st generation Grubbs catalyst [(PCy3)2Cl2RuCHPh] (Cy is cyclohexyl), these monomers smoothly undergo homopolymerization and copolymerization with parent fullerene-free monomers. The homopolymers are insoluble in common organic solvents, while the copolymers obtained at different molar ratios to their fullerene-free analogues are very soluble in organic solvents and can be suitable for the preparation of thin films.

Donor-Induced Decomposition of the Grubbs Catalysts: An Intercepted Intermediate

The σ-alkyl species RuCl2(CH2PCy3)(py)3 (3a) is intercepted on adding pyridine to the first-generation Grubbs catalyst 1a during RCM or to the isolated resting-state species RuCl2(PCy3)2(═CH2) (2a). Complex 3a is formed by pyridine-induced displacement of PCy3 and nucleophilic attack of the liberated PCy3 on the methylidene carbon. The rapid, near-quantitative conversion of 2a into 3a indicates that nucleophilic attack by PCy3 is the primary deactivating event. Once formed, 3a decomposes more slowly via several competing pathways. One such pathway involves elimination of the σ-alkyl ligand as [CH3PCy3]Cl (A), following proton and chloride abstraction. Observation of nearly 80% 3a during RCM by 1a in the presence of pyridine confirms the relevance of this behavior to metathesis and implicates the resting-state methylidene 2a as the vulnerable species, rather than the metallacyclobutane intermediate. Any donor capable of displacing PCy3 and stabilizing a five-coordinate methylidene adduct is predicted to tr...

On the Compatibility of Ruthenium Metathesis Catalysts with Secondary Phosphines

While attempts to incorporate secondary phosphine ligands into the first-generation Grubbs catalyst RuCl2(PR3)2(═CHPh) (GI, R = Cy) were frustrated by decomposition (for HPCy2) or bulk (for HPtBu2)...

On the Stereoselectivity of Ring-Opening Metathesis Polymerization (ROMP) of N-Arylpyrrolidine-Fused Cyclobutenes with Molybdenum– and Ruthenium–Alkylidene Catalyst

Ring-opening metathesis polymerization (ROMP) of cyclobutenes fused with N-arylpyrrolidene with Schrock–Hoveyda catalyst containing a racemic biphenolate ligand [Mo(N-2,6-i-Pr2C6H3)(CHCMe2Ph)(biphenolate)] gives polycyclobutenes with homogeneous tacticity and predominantly double bonds in Z-configuration. Reactions of the same substrates with the first-generation Grubbs catalyst [(Cy3P)2Cl2Ru═CHPh] or Schrock molybdenum carbene with monodendate alkoxy ligands [Mo(N-2,6-i-Pr2C6H3)(CHCMe2Ph)(OCMe(CF3)2] yield the corresponding polycyclobutene containing a mixture of Z- and E-double bonds. Upon diimide reduction, all these polycyclobutenes give the same tactic hydrogenated polymers, indicating that the stereochemistry at the asymmetric carbons remains the same in all these reactions. The stereoselectivities of ROMP with cyclobutenes and with norbornenes are compared, and the plausible mechanisms are proposed.

Synthesis of Well-Defined Unsaturated Polyesters by Transition-Metal-Catalyzed Polycondensation of Bis(diazoacetate)s

A variety of aliphatic- and aromatic-type unsaturated polyesters (UPs) were prepared by transition-metal-catalyzed single-component polycondensation of bis(diazoacetate)s under a mild condition. With the second-generation Grubbs catalyst, the polycondensation proceeded exclusively through an intermolecular highly cis-selective C═C forming coupling of diazo-bearing carbons with N2 release, giving well-defined UPs. The cis-C═Cs of the resulting polymers could be isomerized quantitatively into trans-C═Cs with a catalytic amount of diethylamine. Additionally, other metal complexes, the first-generation Grubbs catalyst, rhodium(II) acetate, and copper(II) acetylacetonate, also produced UPs from the bis(diazoacetate)s, with lower stereoselectivities, although an unexpected carbene oligomerization of the monomers partially occurred along with the C═C bond-forming coupling.

Calixarene-based molecular capsule from olefin metathesis

The reaction of tetra­kis­(all­yloxy)calix[4]arene with the first-generation Grubbs catalyst, followed by catalytic hydrogenation, gave the novel bis-calixarene 15,20,46,51,64,69,74,79-octa­oxatridecacyclo[32.28.8.83,28.113,53.122,44.09,14.021,26.038,70.040,45.052,57.059,63.07,80.032,73]octa­conta-1(63),3,5,7(80),9(14),10,12,21,23,25,28(73),29,31,34,36,38(70),40,42,44,52,54,56,59,61-tetra­cosa­ene benzene monosolvate, C72H72O8·C6H6. The structure consists of two calix[4]arene units connected by four-carbon chains at each of the four O atoms on their narrow rims, to form a cage. Each of the calix[4]arene units has a flattened cone conformation in which two of the opposite aryl groups are closer together and nearly parallel [dihedral angle between planes = 7.35 (16)°], and the other two aryl groups are splayed outward [dihedral angle between planes = 72.20 (8)°]. While the cavity contains no solvent or other guest mol­ecule, there is benzene solvent mol­ecule in the lattice. Two of the alkyl linking arms were disordered over two conformations with occupancies of 0.582 (3)/0.418 (3) and 0.33 (4)/0.467 (4). They were constrained to have similar metrical and thermal parameters.