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

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

• . Reactivity of vinylsilanes in the presence of ruthenium alkylidene complexes; a) cross metathesis, b) homometathesis, and c) decomposition of β-silylruthenacyclobutane. Application of olefin metathesis in the synthesis and modification of POSS-based materials: a) functionalization of vinyl-substituted POSS

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

• based on the design concepts illustrated in Scheme 1 [3]. The design concept C is of interest because of the potential hemilabile nature and latent metathesis activity of these complexes [4]. Of particular interest to us are the ruthenium alkylidene complexes containing the pyridinyl alcoholato

• ) of diethyl diallylmalonate with 100% conversion after 30 min, results comparable to the unimolecular catalyst. Denk et al. [9] synthesised N-heterocyclic (NHC) ruthenium alkylidene complexes containing pyridinyl-alcoholato ligands (4). These complexes were tested as precatalysts at different

• of methyl 9-dodecene and in hexane for the RO-RCM of cis-cyclooctene. The above-mentioned studies clearly illustrate the versatility and use of ruthenium alkylidene complexes with pyridinyl-alcoholato ligands. In principle these studies had one approach in common concerning the pyridinyl-alcoholato

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

• ]. According to the Chauvin mechanism, the catalytically active species are Schrock-type carbenes or alkylidenes [2]. Olefin metathesis greatly profited from the isolation of structurally well-defined metal alkylidene complexes [3][4]. The best studied and most commonly employed catalysts are based on Mo, W

Efficient catalytic alkyne metathesis with a fluoroalkoxy-supported ditungsten(III) complex

• Henrike Ehrhorn,
• Janin Schlösser,
• Dirk Bockfeld and
• Matthias Tamm

Beilstein J. Org. Chem. 2018, 14, 2425–2434, doi:10.3762/bjoc.14.220

• were initially based on a design strategy inspired by the structure of highly active olefin metathesis catalysts, the Schrock-type molybdenum and tungsten alkylidene complexes [13][14][15]. Imidazolin-2-iminato ligands were used to modify Schrock-type alkylidyne complexes, resulting in new active

Ru complexes of Hoveyda–Grubbs type immobilized on lamellar zeolites: activity in olefin metathesis reactions

• Hynek Balcar,
• Naděžda Žilková,
• Martin Kubů,
• Michal Mazur,
• Zdeněk Bastl and
• Jiří Čejka

Beilstein J. Org. Chem. 2015, 11, 2087–2096, doi:10.3762/bjoc.11.225

• immobilization; olefin metathesis; Introduction Immobilization of Ru alkylidene complexes (Grubbs and Hoveyda–Grubbs type catalysts) on siliceous supports represents a successful way to highly active, selective, and reusable metathesis catalysts [1][2][3][4]. Mesoporous molecular sieves (MCM-41, MCM-48, SBA-15

• ) not allowing to anchor appropriate alkylidene complexes in the channel system and to ensure accessibility of catalytic centers by reactants. However, new methods for the preparation of lamellar (also called two-dimensional) zeolite with high surface area and layered structure have been developed [23

• alkylidene complexes HGIIN+Cl− and HGIIN+PF6− were kindly provided by Krzysztof Skowerski (Apeiron Synthesis, Wroclaw, Poland). Zeolites MCM-22, MCM-56 and MCM-36 (Na forms) were prepared according to literature [37][38][39] as well as mesoporous molecular sieves SBA-15 [40]. Individual supports were

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

• , OR 97203, USA 10.3762/bjoc.11.212 Abstract Three new ruthenium alkylidene complexes (PCy3)Cl2(H2ITap)Ru=CHSPh (9), (DMAP)2Cl2(H2ITap)Ru=CHPh (11) and (DMAP)2Cl2(H2ITap)Ru=CHSPh (12) have been synthesized bearing the pH-responsive H2ITap ligand (H2ITap = 1,3-bis(2’,6’-dimethyl-4’-dimethylaminophenyl

• the polymerization process. Furthermore, the coagulate content for all experiments stayed <2%. This represents an unprecedented efficiency in emulsion ROMP based on hydrophilic ruthenium alkylidene complexes. Keywords: activation; aqueous catalysis; emulsion; olefin metathesis; polymerization

• accessibility of water-insoluble catalysts has resulted in an increased investigation of water-insoluble Ru–alkylidene complexes for emulsion ROMP in aqueous media. Slugovc et al. reported the ROMP of dicyclopentadiene (DCPD) in a “high internal phase emulsion” (HIPE) of the monomer in water [58]. Stable

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

• confirmed the formation of new alkylidene complexes. Complexes 13 and 14 were prepared by using a similar methodology. Complex 4 was subjected to a metathesis exchange with a slight excess of the appropriate 2-vinylphenol in the presence of triphenylphosphine (Scheme 3). Complexes were obtained with

• ruthenium–alkylidene complexes active in metathesis, the coordination of the Ru atom might be described as a distorted tetragonal pyramid, with the carbon atom double-bonded to Ru (C4) in the apex of the pyramid. The distortions in the dimer are more pronounced than in the similar mononuclear complex 1a

Nitro-Grela-type complexes containing iodides – robust and selective catalysts for olefin metathesis under challenging conditions

• Andrzej Tracz,
• Mateusz Matczak,
• Katarzyna Urbaniak and
• Krzysztof Skowerski

Beilstein J. Org. Chem. 2015, 11, 1823–1832, doi:10.3762/bjoc.11.198

• – reaction under Ar, red squares – reaction under ethylene). Modifications of the 2nd generation alkylidene complexes. Synthesis of iodide-containing nitro-Grela type catalysts. Results of RCM reactions.a Results of CM reactions.a Results of the macrocyclization reactions. RCM of 1 in ACS-grade solvents

Latent ruthenium–indenylidene catalysts bearing a N-heterocyclic carbene and a bidentate picolinate ligand

• Thibault E. Schmid,
• Florian Modicom,
• Adrien Dumas,
• Etienne Borré,
• Loic Toupet,
• Olivier Baslé and
• Marc Mauduit

Beilstein J. Org. Chem. 2015, 11, 1541–1546, doi:10.3762/bjoc.11.169

• catalytic performance [10][11][12]. Among the different [N–O]-chelating ligands that have been previously considered [13][14][15][16][17], the pyridyl-2-carboxylate (picolinate) ligand has demonstrated its usefulness in the preparation of efficient latent catalysts based on (NHC)Ru–alkylidene complexes [18

Metal–ligand multiple bonds as frustrated Lewis pairs for C–H functionalization

• Matthew T. Whited

Beilstein J. Org. Chem. 2012, 8, 1554–1563, doi:10.3762/bjoc.8.177

• , moderately-to-severely bulky ligands must be employed to favor the most reactive monomeric M═E FLPs. M═E FLPs with π-basic ligands: Reactions with unsaturated bonds Species containing Mδ+═Eδ− moieties have been known for some time, with the clearest examples being terminal imido and alkylidene complexes of

• alkylidene complexes that can cleave C–H bonds. An alternative route involves the generation of a M═E FLP species by multiple C−H (or E–H) activations [18][70][86]. As mentioned above, Whited and Grubbs showed that an iridium(I) carbene system that exhibited FLP reactivity could be generated by multiple C–H

Synthesis of Ru alkylidene complexes

• Renat Kadyrov and
• Anna Rosiak

Beilstein J. Org. Chem. 2011, 7, 104–110, doi:10.3762/bjoc.7.14

• Renat Kadyrov Anna Rosiak Evonik Degussa GmbH, Rodenbacher Chaussee 4, 63457 Hanau-Wolfgang, Germany present address: ASM Research Chemicals, Feodor-Lynen-Str. 31, 30625 Hannover, Germany 10.3762/bjoc.7.14 Abstract The present work describes the robust synthesis of Ru alkylidene complexes (PCy3

• (thienyl) bond was estimated (ΔG≠303K = 12.6 kcal/mol). Keywords: alkylidene complexes; metathesis; rotation barrier; ruthenium; Introduction The key to active ruthenium metathesis initiators is the accessibility of the ruthenium precursor containing the alkylidene moiety. The most commonly used

• precursors for the “second generation” catalysts bearing NHC ligands are the alkylidene ruthenium complexes coordinated with two phosphines [1]. For recent reviews see [2][3][4]. There are several routes for accessing five-coordinated ruthenium(II) alkylidene complexes such as diazo-transfer [5] and the

Recent advances in the development of alkyne metathesis catalysts

• Xian Wu and
• Matthias Tamm

Beilstein J. Org. Chem. 2011, 7, 82–93, doi:10.3762/bjoc.7.12

• imido ligands, which are present in some of the most active olefin metathesis catalysts, i. e., Schrock–Hoveyda-type tungsten and molybdenum imido-alkylidene complexes [10]. We presumed that substitution of the imido ligands by imidazolin-2-iminato ligands and concurrent conversion of the metal–carbon

Hoveyda–Grubbs type metathesis catalyst immobilized on mesoporous molecular sieves MCM-41 and SBA-15

• Hynek Balcar,
• Tushar Shinde,
• Naděžda Žilková and
• Zdeněk Bastl

Beilstein J. Org. Chem. 2011, 7, 22–28, doi:10.3762/bjoc.7.4

• : alkene metathesis; catalyst immobilization; hybrid catalysts; mesoporous molecular sieves; Ru–alkylidene complexes; Introduction Ru–alkylidene complexes (Grubbs and Hoveyda–Grubbs catalysts, 1 and 2, respectively, Figure 1) belong to the most active and frequently used metathesis catalysts. These

The catalytic performance of Ru–NHC alkylidene complexes: PCy₃ versus pyridine as the dissociating ligand

• Stefan Krehl,
• Diana Geißler,
• Sylvia Hauke,
• Oliver Kunz,
• Lucia Staude and
• Bernd Schmidt

Beilstein J. Org. Chem. 2010, 6, 1188–1198, doi:10.3762/bjoc.6.136

• propargylic alcohols as alkylidene precursors [10], which resulted in the synthesis of a first generation analogue C with an indenylidene ligand [11][12]. A landmark in the evolution of Ru-metathesis catalysts was the introduction of alkylidene complexes bearing N-heterocyclic carbenes (NHC) [13][14][15], in