Radical chemistry in polymer science: an overview and recent advances

• Zixiao Wang,
• Feichen Cui,
• Yang Sui and
• Jiajun Yan

Beilstein J. Org. Chem. 2023, 19, 1580–1603, doi:10.3762/bjoc.19.116

• mechanism (cf. section 3.2) [86]. 2.3 Metal-free ring opening metathesis polymerization (MF-ROMP) ROMP is a powerful and broadly applicable technique for synthesizing polymers. Traditional ROMP systems are initiated by transition-metal complexes and Ru-based alkylidene complexes, which are also known as

• Grubbs catalysts (Scheme 12A), are the most popular ones [87]. However, Ru-based catalysts are expensive making them less attractive for industrial applications. Living ROMP is commonly terminated by adding a special chemical which can remove the transition metal from the chain end and deactivate it from

• propagation. However, removing this residue from the product by traditional chromatographic methods can be a challenging task and limits the application of ROMP-produced polymers in biomedical and microelectronic fields [88]. To avoid such drawbacks, the development of a metal-free (MF) procedures is

Ring-closing metathesis of prochiral oxaenediynes to racemic 4-alkenyl-2-alkynyl-3,6-dihydro-2H-pyrans

• Viola Kolaříková,
• Markéta Rybáčková,
• Martin Svoboda and
• Jaroslav Kvíčala

Beilstein J. Org. Chem. 2020, 16, 2757–2768, doi:10.3762/bjoc.16.226

• reactions of unsaturated compounds, e.g., alkene and enyne cross metathesis (CM [1] and EYCM [2][3][4]), alkene and enyne ring-closing metathesis (RCM and RCEYM) [5][6], ring-opening metathetic polymerization (ROMP) [7], etc., the CM and RCM are the most popular in organic synthesis [8]. Furthermore, the

An overview of the cycloaddition chemistry of fulvenes and emerging applications

• Ellen Swan,
• Kirsten Platts and
• Anton Blencowe

Beilstein J. Org. Chem. 2019, 15, 2113–2132, doi:10.3762/bjoc.15.209

• metathesis polymerisation (ROMP) to generate facially amphiphilic polymers [182][235][237][238]. Ilker et al. employed the DAC between alkyl pentafulvenes and maleic anhydride to initially prepare norbornene anhydride monomers that could be further functionalised to afford norbornene imide monomers (Scheme

•  21) [105][237]. ROMP of the monomers, followed by deprotection yielded facially amphiphilic polynorbornenes that displayed lipid membrane disruption and antimicrobial activities [237][238]. The facially amphiphilic polynorbornenes with pendent ammonium groups were found to disrupt negatively charged

Hoveyda–Grubbs catalysts with an N→Ru coordinate bond in a six-membered ring. Synthesis of stable, industrially scalable, highly efficient ruthenium metathesis catalysts and 2-vinylbenzylamine ligands as their precursors

• Kirill B. Polyanskii,
• Kseniia A. Alekseeva,
• Pavel V. Raspertov,
• Pavel A. Kumandin,
• Eugeniya V. Nikitina,
• Atash V. Gurbanov and
• Fedor I. Zubkov

Beilstein J. Org. Chem. 2019, 15, 769–779, doi:10.3762/bjoc.15.73

• , ring-opening metathesis polymerization – ROMP and acyclic diene metathesis – ADMET. This motivates the investigations into the development of new, efficient, stable, and highly selective catalytic systems based on ruthenium complexes. However, in reality, a limited set of commercially available

• ][26][27][28][29][30][31][32][33][34][35][36][37][38]. Moreover, a small number of patents, which describe the applications of such type of catalysts in ROMP reactions, were published [25][26][27][28]. Among all these applications, the use of the catalysts for the polymerization of dicyclopentadiene

Synthesis of polydicyclopentadiene using the Cp₂TiCl₂/Et₂AlCl catalytic system and thin-layer oxidation of the polymer in air

• Zhargolma B. Bazarova,
• Ludmila S. Soroka,
• Alex A. Lyapkov,
• Мekhman S. Yusubov and
• Francis Verpoort

Beilstein J. Org. Chem. 2019, 15, 733–745, doi:10.3762/bjoc.15.69

• , which reacts with R-olefin and a Lewis base to form stable crystalline titanacyclobutanes. Both titanium carbene and titanacycles are ROMP catalysts (Scheme 4). PDCPD polymers were obtained by precipitation in ethanol, dried and characterized by FTIR, NMR, and GPC. Figure 6 displays a typical infrared

• ratios of adsorption bands at 1620 and 700 cm−1 vs layer exposure time in air at ambient temperature. Mechanism of alkylation of Cp2TiCl2. The structures formed as a result of the cationic polymerization of dicyclopentadiene. The units resulting from ROMP of dicyclopentadiene. Mechanism of ROMP

Aqueous olefin metathesis: recent developments and applications

• Valerio Sabatino and
• Thomas R. Ward

Beilstein J. Org. Chem. 2019, 15, 445–468, doi:10.3762/bjoc.15.39

•  1c). This review focuses on the recent improvements of olefin metathesis in aqueous media and the resulting applications in bioinorganic chemistry and chemical biology. Review Challenges in aqueous metathesis The first examples of aqueous metathesis were reported in the late 1980s [25][26]. ROMP

• Raines reported examples of RCM, CM and ROMP in heterogeneous conditions with hydrophobic catalysts [21][33]. Blechert prepared alkoxy- and cyano-substituted catalysts 19 and 20 from G-II (Scheme 5) [34], while Raines and co-workers employed the conventional catalysts G-II and HG-II [35]. Blechert and

• , the presence of a Brønsted acid led to the protonation of one phosphine ligand rather than reacting with the ruthenium alkylidene moiety. Scavenging of the trialkylphosphine moiety resulted in a more active complex capable of initiating the ROMP of 2,3-difunctionalized norbornadienes and 7-oxo

Application of olefin metathesis in the synthesis of functionalized polyhedral oligomeric silsesquioxanes (POSS) and POSS-containing polymeric materials

• Patrycja Żak and
• Cezary Pietraszuk

Beilstein J. Org. Chem. 2019, 15, 310–332, doi:10.3762/bjoc.15.28

• silsesquioxanes (POSS) and POSS-containing polymeric materials. Three types of processes, i.e., cross metathesis (CM) of vinyl-substituted POSS with terminal olefins, acyclic diene metathesis (ADMET) copolymerization of divinyl-substituted POSS with α,ω-dienes and ring-opening metathesis polymerization (ROMP) of

• POSS-substituted norbornene (or other ROMP susceptible cycloolefins) are discussed. Emphasis was put on the synthetic and catalytic aspects rather than on the properties and applications of synthesized materials. Keywords: olefin metathesis; POSS; silsesquioxanes; Introduction Silsesquioxanes are

• polymerization (ROMP) of POSS-substituted norbornene (or other ROMP susceptible cycloolefins, Scheme 2). Nearly all metathetic transformations described in this review have been performed in the presence of commonly used ruthenium-based catalysts (Figure 3). In contrast, there are only a few examples of

Olefin metathesis in multiblock copolymer synthesis

• Maria L. Gringolts,
• Yulia I. Denisova,
• Eugene Sh. Finkelshtein and
• Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2019, 15, 218–235, doi:10.3762/bjoc.15.21

• . Keywords: ADMET; macromolecular cross metathesis; multiblock copolymers; olefin metathesis; ROMP; Introduction Nowadays, olefin metathesis has become a well-established field of organic and polymer chemistry. The discovery of metallocarbene initiators that are capable of catalyzing metathesis

• -functionalized blocks, and macromolecular cross metathesis. Review Synthesis by sequential ring-opening metathesis polymerization Living ring-opening metathesis polymerization (ROMP) provides an opportunity to use a well-established route to multiblock copolymers based on the repetitive addition of different

• to copolymers with a limited number of blocks, such as tetrablocks or pentablocks [52], because each time a new monomer is added some of the living chains cannot initiate polymerization being terminated with trace impurities. Besides, in the course of ROMP main-chain double bonds are prone to

Catalysis of linear alkene metathesis by Grubbs-type ruthenium alkylidene complexes containing hemilabile α,α-diphenyl-(monosubstituted-pyridin-2-yl)methanolato ligands

• Tegene T. Tole,
• Johan H. L. Jordaan and
• Hermanus C. M. Vosloo

Beilstein J. Org. Chem. 2019, 15, 194–209, doi:10.3762/bjoc.15.19

• (RCM) of dialkenes, ring-opening metathesis polymerisation (ROMP), isomerisation of alkenes and cross-metathesis (CM) of alkenes [7]. The complexes were synthesized by reacting the lithium salts of the corresponding pyridinyl alcohols with [RuCl2(=CHC6H5)(P(iPr3))2]. These complexes catalysed inter

• alia the cyclisation of hex-5-enyl undec-10-enoate to oxacyclohexadec-11-en-2-one (50% at 60 °C in toluene) and the ROMP of dicyclopentadiene. They were also able to immobilise these Grubbs 1-type precatalysts using dendritic pyridinyl alcohols [8]. These complexes catalysed the RCM reaction (at 80 °C

• temperatures in the ROMP of norbornene and cyclooctene. Oligomers were obtained at room temperature in the presence of 4a and 4d, while 4b and 4c yielded polymers. At 60 °C, ROMP was observed with norbornene (98–100%) and cyclooctene (72–80%) in the presence of 4. We investigated a number of Grubbs 1- and

Selective ring-opening metathesis polymerization (ROMP) of cyclobutenes. Unsymmetrical ladderphane containing polycyclobutene and polynorbornene strands

• Yuan-Zhen Ke,
• Shou-Ling Huang,
• Guoqiao Lai and
• Tien-Yau Luh

Beilstein J. Org. Chem. 2019, 15, 44–51, doi:10.3762/bjoc.15.4

• Technology of Ministry of Education, Hangzhou Normal University, Hangzhou, Zhejiang 311121, China 10.3762/bjoc.15.4 Abstract At 0 °C in THF in the presence of Grubbs first generation catalyst, cyclobutene derivatives undergo ROMP readily, whereas norbornene derivatives remain intact. When the substrate

• contains both cyclobutene and norbornene moieties, the conditions using THF as the solvent at 0 °C offer a useful protocol for the selective ROMP of cyclobutene to give norbornene-appended polycyclobutene. Unsymmetrical ladderphane having polycyclobutene and polynorbornene as two strands is obtained by

• further ROMP of the norbornene appended polycyclobutene in the presence of Grubbs first generation catalyst in DCM at ambient temperature. Methanolysis of this unsymmetrical ladderphane gives polycyclobutene methyl ester and insoluble polynorbornene-amide-alcohol. The latter is converted into the

Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands

• Veronica Paradiso,
• Chiara Costabile and
• Fabia Grisi

Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292

• affords an E/Z ratio of ~10 at 79% conversion, whereas catalysts 3–5 gave an E/Z ratio of about 5.5 at the same conversion. As for the ROMP of 16 (Scheme 5), GII-SIMes and 4a displayed the highest activity with similar reactivity. In the attempt to rationalize the catalytic performances of this family of

• -containing unsymmetrical catalysts 31–34 characterized by alkyl N-substituents with variable steric bulk (Figure 8) [22]. The catalytic performances of these complexes and of complex 24a were evaluated for the RCM of diethyl diallylmalonate (7) and the ROMP of cis-1,5-cyclooctadiene (16). In the RCM reaction

• group resulted in a lower catalyst activity. Indeed, complex 24a bearing the small methyl moiety on the nitrogen, revealed as the best performing catalyst, even surpassing the parent complex GII-SIMes. In the ROMP reaction (Scheme 5), carried out in different solvents and monomer/catalyst ratios, the

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• )iridium(III) reported in ref [37] for photocontrolled radical polymerization of methacrylates. The use of a Fe complex or dye (for metal-free PC) is also possible to performed ATRP as described in reference [107]. A ROMP mechanism is also possible thanks to the photoredox catalyst. ROMP stands for ring

• -opening metathesis polymerization. This polymerization is based on cyclic olefins whose ring strain is released during polymerization. This reaction needs a catalyst to occur [108]. Metal-free photoredox catalysts for ROMP were proposed in [109]. For example, pyrylium and acridinium salts can be used as

• good candidates for photooxidation of vinyl ether initiators. A Ru-based ROMP precatalyst: [Ru(IMesH2)(CF3CO2)(t-BuCN)4)]+ CF3CO2– which is a thermally stable photoredox catalyst has been also proposed in [110]. To finish, the RAFT polymerization can be also extended in a photocontrolled polymerization

A tutorial review of stereoretentive olefin metathesis based on ruthenium dithiolate catalysts

• Daniel S. Müller,
• Olivier Baslé and
• Marc Mauduit

Beilstein J. Org. Chem. 2018, 14, 2999–3010, doi:10.3762/bjoc.14.279

• Blechert modification (Ru-6) initiates much faster with (E)-2-hexenyl acetate compared to the parent catalyst Ru-3. 4 Selected applications The synthetic usefulness of ruthenium dithiolate catalysts was demonstrated in numerous synthetic applications such as ring-opening metathesis polymerization (ROMP

• ), ring-opening/cross metathesis (ROCM), cross metathesis (CM), self-metathesis and ring-closing metathesis (RCM) reactions. Scheme 2 and Scheme 3 display selected examples for each of these reactions [1]. ROMP is one of the most facile metathesis reactions, thus allowing for very low catalyst loadings

• (Scheme 2a). Both catalysts Ru-1 and Ru-2 achieved excellent selectivities and good yields for the ROMP of norbornene (1) with catalyst loadings as low as 20 ppm (Scheme 2a) [2]. The ROMP of cyclooctadiene 3 was equally efficient with catalysts Ru-1 and Ru-2 [2]. It should be noted that the ROMP of

Olefin metathesis catalysts embedded in β-barrel proteins: creating artificial metalloproteins for olefin metathesis

• Daniel F. Sauer,
• Johannes Schiffels,
• Takashi Hayashi,
• Ulrich Schwaneberg and
• Jun Okuda

Beilstein J. Org. Chem. 2018, 14, 2861–2871, doi:10.3762/bjoc.14.265

• (ROMP) on the protein surface employing a PEGylated norbornene derivative as substrate [13]. This led to proteins modified with PEG chains. These two examples illustrate the potential applications of olefin metathesis in protein modification. Further applications would be the implementation of olefin

• . These transformations include all three fundamental olefin metathesis reactions: ring-opening metathesis polymerization (ROMP), ring-closing metathesis (RCM) as well as cross metathesis (CM) (Scheme 2). Review Artificial metatheases – anchoring approaches Metalloproteins that contain one or more metal

• weight distribution (PDI = 1.05), suggesting the living nature of the ROMP even within the protein scaffold. Neither regioselectivity (cis/trans) nor tacticity were affected [56]. The transmembrane protein FhuA The β-barrel proteins introduced for the construction of artificial metatheases up to this

Ring-opening metathesis of some strained bicyclic systems; stereocontrolled access to diolefinated saturated heterocycles with multiple stereogenic centers

• Zsanett Benke,
• Melinda Nonn,
• Márton Kardos,
• Santos Fustero and
• Loránd Kiss

Beilstein J. Org. Chem. 2018, 14, 2698–2707, doi:10.3762/bjoc.14.247

• catalysts, bicyclic lactone (±)-4 a stereoisomer of (±)-3 furnished olefinated γ-lactone (±)-6 similar to (±)-5 (Scheme 3, Table 2). Unfortunately, ROM reactions, however, took place with total conversions, they were always accompanied by the formation of a significant amount of polymeric materials (ROMP

Simple activation by acid of latent Ru-NHC-based metathesis initiators bearing 8-quinolinolate co-ligands

• Julia Wappel,
• Roland C. Fischer,
• Luigi Cavallo,
• Christian Slugovc and
• Albert Poater

Beilstein J. Org. Chem. 2016, 12, 154–165, doi:10.3762/bjoc.12.17

• 10.3762/bjoc.12.17 Abstract A straightforward synthesis utilizing the ring-opening metathesis polymerization (ROMP) reaction is described for acid-triggered N,O-chelating ruthenium-based pre-catalysts bearing one or two 8-quinolinolate ligands. The innovative pre-catalysts were tested regarding their

• behavior in ROMP and especially for their use in the synthesis of poly(dicyclopentadiene) (pDCPD). Bearing either the common phosphine leaving ligand in the first and second Grubbs olefin metathesis catalysts, or the Ru–O bond cleavage for the next Hoveyda-type catalysts, this work is a step forward

• initiators was able to convert the monomer to a polymer. Therefore, efforts to activate the initiators via acid have been made. Upon addition of HCl aq complexes 1 to 4 became active and initiated the ROMP reaction of 5. The activation process is accompanied by a colour change from deep red, to brownish to

Recent advances in metathesis-derived polymers containing transition metals in the side chain

• Ileana Dragutan,
• Valerian Dragutan,
• Bogdan C. Simionescu,
• Albert Demonceau and
• Helmut Fischer

Beilstein J. Org. Chem. 2015, 11, 2747–2762, doi:10.3762/bjoc.11.296

• as prepared by controlled living ring-opening metathesis polymerization (ROMP) of the respective metal-incorporating monomers. Ferrocene- and other metallocene-modified polymers, macromolecules including metal-carbonyl complexes, polymers tethering early or late transition metal complexes, etc. are

• herein discussed. Recent advances in the design and syntheses reported mainly during the last three years are highlighted, with special emphasis on new trends for superior applications of these hybrid materials. Keywords: advanced materials; metallopolymers; metathesis; ROMP; transition metals

• ) polymerization [15][16], living ionic polymerizations, specifically ring-opening polymerization (ROP) [17], as well as migration insertion polymerization (MIP) [18], acyclic diene metathesis polymerization (ADMET) [19][20] and ring-opening metathesis polymerization (ROMP) [21][22][23][24][25][26][27]. These

Olefin metathesis in air

• Lorenzo Piola,
• Fady Nahra and
• Steven P. Nolan

Beilstein J. Org. Chem. 2015, 11, 2038–2056, doi:10.3762/bjoc.11.221

• been made to render catalysts more stable and yet more functional group tolerant. This review summarizes the major developments concerning catalytic systems directed towards water and air tolerance. Keywords: air stability; catalysis; olefin metathesis; RCM; ROMP; ruthenium; Introduction Transition

• -workers synthesized the first well-defined ruthenium(II) complex (5, Scheme 2) bearing a carbene moiety, able to perform ring-opening metathesis polymerization (ROMP) reactions of low-strained olefins [34][35] and ring-closing metathesis (RCM) reactions of functionalized dienes [36]. In the solid state

• , showed the highest rate of initiation reported to date for alkene metathesis reactions. Complex 81 is used mostly for ROMP and CM reactions with electron-deficient olefins. The complex can be prepared in air but only one example of its use in air has been reported. In 2010, Tew and co-workers reported

Hexacoordinate Ru-based olefin metathesis catalysts with pH-responsive N-heterocyclic carbene (NHC) and N-donor ligands for ROMP reactions in non-aqueous, aqueous and emulsion conditions

• Shawna L. Balof,
• K. Owen Nix,
• Matthew S. Olliff,
• Sarah E. Roessler,
• Arpita Saha,
• Kevin B. Müller,
• Ulrich Behrens,
• Edward J. Valente and
• Hans-Jörg Schanz

Beilstein J. Org. Chem. 2015, 11, 1960–1972, doi:10.3762/bjoc.11.212

• (ROMP) and ring closing metathesis (RCM) reactions with standard substrates. The ROMP with complex 11 is accelerated in the presence of two equiv of H3PO4, but is reduced as soon as the acid amount increased. The metathesis of phenylthiomethylidene catalysts 9 and 12 is sluggish at room temperature, but

• their ROMP can be dramatically accelerated at 60 °C. Complexes 11 and 12 are soluble in aqueous acid. They display the ability to perform RCM of diallylmalonic acid (DAMA), however, their conversions are very low amounting only to few turnovers before decomposition. However, both catalysts exhibit

• outstanding performance in the ROMP of dicyclopentadiene (DCPD) and mixtures of DCPD with cyclooctene (COE) in acidic aqueous microemulsion. With loadings as low as 180 ppm, the catalysts afforded mostly quantitative conversions of these monomers while maintaining the size and shape of the droplets throughout

New aryloxybenzylidene ruthenium chelates – synthesis, reactivity and catalytic performance in ROMP

• Patrycja Żak,
• Szymon Rogalski,
• Mariusz Majchrzak,
• Maciej Kubicki and
• Cezary Pietraszuk

Beilstein J. Org. Chem. 2015, 11, 1910–1916, doi:10.3762/bjoc.11.206

• exhibit high catalytic inactivity in their dormant forms and a profound increase in activity after activation with HCl. The strong electronic influence of substituents in the chelating ligand on the catalytic activity was demonstrated. The catalytic properties were tested in ROMP of cyclooctadien (COD

• ) and a single selected norbornene derivative. Keywords: chemoactivation; latent catalysts; metathesis; ROMP; ruthenium; Introduction Olefin metathesis is nowadays one of the most important methods for the formation of carbon–carbon bonds in organic and polymer chemistry [1][2]. The availability of

• have also been independently studied by Skowerski and Grela [10]. Phenoxybenzylidene complexes have been demonstrated to behave like latent catalysts in common testing reactions involving ring opening metathesis polymerisation (ROMP) of COD, norbornene derivative and dicyclopentadiene as well as cross

Stereochemistry of ring-opening/cross metathesis reactions of exo- and endo-7-oxabicyclo[2.2.1]hept-5-ene-2-carbonitriles with allyl alcohol and allyl acetate

• Piotr Wałejko,
• Michał Dąbrowski,
• Lech Szczepaniak,
• Jacek W. Morzycki and
• Stanisław Witkowski

Beilstein J. Org. Chem. 2015, 11, 1893–1901, doi:10.3762/bjoc.11.204

• allyl acetate promoted by different ruthenium alkylidene catalysts were studied. The stereochemical outcome of the reactions was established. The issues concerning chemo- (ROCM vs ROMP), regio- (1-2- vs 1-3-product formation), and stereo- (E/Z isomerism) selectivity of reactions under various conditions

• are discussed. Surprisingly good yields of the ROCM products were obtained under neat conditions. Keywords: Grubbs’ catalysts; metathesis; ROCM; ROMP; Z-selectivity; Introduction Substituted tetrahydrofurans are a common motif found in many biologically active natural products [1][2], e.g

• -opening metathesis polymerization (ROMP) can be minimized by carrying out the reaction in high dilution. Furthermore good yields of ROCM products can be obtained only when an 1.5-fold excess of a cross olefin is used [14][19][20]. Results and Discussion Now, we wish to report our preliminary results of

Cross-metathesis of polynorbornene with polyoctenamer: a kinetic study

• Yulia I. Denisova,
• Maria L. Gringolts,
• Alexander S. Peregudov,
• Liya B. Krentsel,
• Ekaterina A. Litmanovich,
• Arkadiy D. Litmanovich,
• Eugene Sh. Finkelshtein and
• Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2015, 11, 1796–1808, doi:10.3762/bjoc.11.195

• and PCOE are commonly synthesized by ring-opening metathesis polymerization (ROMP). PNB is a well-known commercial product available under the trademark Norsorex® [8][16], which is mainly used as a solidifier of oil and solvent for the complete absorption of oil or other hydrocarbons. PCOE, known as

• structure, which gets opened during ROMP [8][20]. To solve this problem, two approaches were elaborated in the literature. One approach utilizes a specially designed catalyst that facilitates the formation of a highly alternating NB-COE copolymer [21][22][23][24][25]. The other approach is associated with a

• Gr-1 and PNB in CDCl3. This technique is widely applied for investigating ROMP in the presence of well-defined catalysts since it allows quantitative determination of the active complex type and conversion during the reaction [29][30][31]. By fitting the experimental data with a simple kinetic model

Grubbs–Hoveyda type catalysts bearing a dicationic N-heterocyclic carbene for biphasic olefin metathesis reactions in ionic liquids

• Maximilian Koy,
• Hagen J. Altmann,
• Benjamin Autenrieth,
• Wolfgang Frey and
• Michael R. Buchmeiser

Beilstein J. Org. Chem. 2015, 11, 1632–1638, doi:10.3762/bjoc.11.178

• , H2ITapMe2 = 1,3-bis(2’,6’-dimethyl-4’-trimethylammoniumphenyl)-4,5-dihydroimidazol-2-ylidene, OTf− = CF3SO3−) based on a dicationic N-heterocyclic carbene (NHC) ligand was prepared. The reactivity was tested in ring opening metathesis polymerization (ROMP) under biphasic conditions using a nonpolar organic

• solvent (toluene) and the ionic liquid (IL) 1-butyl-2,3-dimethylimidazolium tetrafluoroborate [BDMIM+][BF4−]. The structure of Ru-2 was confirmed by single crystal X-ray analysis. Keywords: biphasic catalysis; ionic initiators; recycling; ROMP; ruthenium; Introduction Ionic metathesis catalysts offer

• are introduced via anion metathesis [13][14]. These novel catalytic systems have successfully been used under SILP conditions [11][15]. Furthermore, they allow running ring-opening metathesis polymerization (ROMP) reactions under biphasic conditions, an approach that offers access to both ROMP-derived

Thermal properties of ruthenium alkylidene-polymerized dicyclopentadiene

• Yuval Vidavsky,
• Yotam Navon,
• Yakov Ginzburg,
• Moshe Gottlieb and
• N. Gabriel Lemcoff

Beilstein J. Org. Chem. 2015, 11, 1469–1474, doi:10.3762/bjoc.11.159

• Differential scanning calorimetry (DSC) analysis of ring opening methatesis polymerization (ROMP) derived polydicyclopentadiene (PDCPD) revealed an unexpected thermal behavior. A recurring exothermic signal can be observed in the DSC analysis after an elapsed time period. This exothermic signal was found to be

• ]. Metathesis polymerization techniques [13][14][15], and especially ring opening metathesis polymerization (ROMP) [16][17], have had a vital role in this growth. Polydicyclopentadiene (PDCPD), probably the most widely used metathesis polymer, is formed through ROMP of mostly endo-dicyclopentadiene (DCPD, 1

• ) (Figure 1). The Grubbs-type ruthenium initiators, known for their high activity, stability and functional group tolerance are extensively used to promote this type of olefin metathesis reactions. For example, the Grubbs second generation catalyst 2 [18] (Figure 1), may be used to initiate ROMP reactions

Consequences of the electronic tuning of latent ruthenium-based olefin metathesis catalysts on their reactivity

• Karolina Żukowska,
• Eva Pump,
• Aleksandra E. Pazio,
• Krzysztof Woźniak,
• Luigi Cavallo and
• Christian Slugovc

Beilstein J. Org. Chem. 2015, 11, 1458–1468, doi:10.3762/bjoc.11.158

• Arabia 10.3762/bjoc.11.158 Abstract Two ruthenium olefin metathesis initiators featuring electronically modified quinoline-based chelating carbene ligands are introduced. Their reactivity in RCM and ROMP reactions was tested and the results were compared to those obtained with the parent unsubstituted

• initiators in ROMP In the next step, compounds 5a, 14 and 15 were tested as initiators in ring-opening metathesis polymerization (ROMP). The active species in ROMP (i.e., the propagating species) can be considered more stable than the methylidene intermediate in RCM, particularly when norbornenes such as

• . Conclusion The present work introduced two ruthenium-based olefin metathesis catalysts/initiators featuring electronically modified quinoline-based chelating carbene ligands. Their reactivity in RCM and ROMP reactions was tested and results were set in comparison to those obtained with the parent compound