- A Cyclic Ruthenium Benzylidene Initiator Platform Enhances Reactivity for Ring-Expansion Metathesis Polymerization
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Ring-expansion metathesis polymerization (REMP) has shown potential as an efficient strategy to access cyclic macromolecules. Current approaches that utilize cyclic olefin feedstocks suffer from poor functional group tolerance, low initiator stability, and slow reaction kinetics. Improvements to current initiators will address these issues in order to develop more versatile and user-friendly technologies. Herein, we report a reinvigorated tethered ruthenium-benzylidene initiator, CB6, that utilizes design features from ubiquitous Grubbs-type initiators that are regularly applied in linear polymerizations. We report the controlled synthesis of functionalized cyclic poly(norbornene)s and demonstrate that judicious ligand modifications not only greatly improve kinetics but also lead to enhanced initiator stability. Overall, CB6 is an adaptable platform for the study and application of cyclic macromolecules via REMP.
- Wang, Teng-Wei,Huang, Pin-Ruei,Chow, Jayme L.,Kaminsky, Werner,Golder, Matthew R.
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supporting information
p. 7314 - 7319
(2021/05/26)
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- METAL-LIGAND COMPLEX, OLEFIN POLYMERIZATION CATALYST DERIVED THEREFROM, AND OLEFIN POLYMERIZATION METHOD UTILIZING THE CATALYST
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A metal-ligand complex has formula (I): wherein J, L, M, R1, R2, R3, R4, X, p, q, and r are defined herein. The metal-ligand complex is useful as a catalyst or catalyst precursor for olefin polymerization.
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Paragraph 0090
(2016/11/14)
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- Non covalent immobilization of pyrene-tagged ruthenium complexes onto graphene surfaces for recycling in olefin metathesis reactions
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Synthesis of Hoveyda-type ruthenium complexes, modified by pyrene tags on the NHC ligand and/or the benzylidene moiety, is described. Thanks to non-covalent π-π interactions these new complexes were immobilized on carbon supports [reduced graphene oxide (rGO) or graphene] and their activity and recoverability for metatheses reactions have been studied. A SIPr-based complex possessing the pyrene function on the benzylidene ligand (C2) delivered the best results for the ring closing metathesis of diethyldiallyl malonate as benchmark reaction. The presence of additional pyrene-functionalized styrenyl-ether as ligand to the rGO-supported catalyst (C2/L@rGO) noticeably improved the recycling procedure allowing supplementary efficient catalytic runs. This may be due either to a facilitated boomerang effect or to a gradual release of the active species in solution. Finally, catalyst C2/L@rGO was proven to be successfully used to promote metathesis reactions in a multisubstrate procedure, the same supported-catalyst batch being successively engaged to transform three different substrates, in diene and ene-yne RCM reactions.
- Nasrallah, Houssein,Germain, Stéphane,Queval, Pierre,Bouvier, Caroline,Mauduit, Marc,Crévisy, Christophe,Schulz, Emmanuelle
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p. 136 - 146
(2016/10/14)
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- New indenylidene-type metathesis catalysts bearing unsymmetrical N-heterocyclic ligands with mesityl and nitrobenzyl substituents
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New indenylidene-type second generation catalysts bearing modified unsymmetrically substituted N- heterocyclic carbene ligands were synthesized. The com- plexes contain an N-mesityl and N?-nitrobenzyl substituted NHC ligand. The precursors of free carbenes—imidazolinium salts—were obtained in an easy and environment- friendly way (under aqueous or neat conditions). The new catalysts were prepared by reaction of in situ generated carbenes with a 1st generation indenylidene catalyst, containing pyridine ligands instead of tricyclohexylphosphine. The complexes were tested in RCM, CM, and ene-yne metathesis model reactions in commercial-grade solvents in air. Their activities were compared with that of commercially available indenylidene catalyst. The structures of complexes and their stability were investigated using static DFT calculations with mixed basis set.
- Malinowska, Marta,Kozlowska, Mariana,Hryniewicka, Agnieszka,Witkowski, Stanis?aw,Morzycki, Jacek W.
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p. 1091 - 1100
(2017/01/11)
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- Modular trimethylene-linked bisimidazol(in)ium salts
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A short and modular synthesis of symmetrically and non-symmetrically substituted bisimidazolinylene N-heterocyclic carbene precursors is described. Two methods to establish dicopper(I) complexes of these compounds depending on the steric shielding of the
- Bessel, Michael,Rominger, Frank,Straub, Bernd F.
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experimental part
p. 1459 - 1466
(2010/10/20)
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- High-yielding large-scale syntheses of enantiomerically pure NOBIN and a NOBIN-based enantiomerically pure NHC precursor
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The MOM-protected monotriflate derived from enantiomerically pure (S)-BINOL rendered (S)-NOBIN (67% over 5 steps) and an (S)-configured NHC precursor (55% over 5 steps) on 10 gram and 5 gram scales, respectively. The C-N bond formation was realized by OTf → NHBn and OTf → NH-CH2-CH 2-NH-mesityl exchanges, respectively. Georg Thieme Verlag Stuttgart.
- S?linger, Daniel,Brückner, Reinhard
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experimental part
p. 109 - 111
(2009/06/05)
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- New pinene-derived pyridines as bidentate chiral ligands
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A synthesis of new bidentate pyridines 8a-d, 9, and 10 has been developed, starting from triflate 14, readily available from β-pinene 11. A copper complex of the pyridine-oxazoline ligands 8a has been found to catalyze asymmetric allylic oxidation of cyclic olefins 36a-c with good conversion rates and acceptable enantioselectivity (≤67% ee). The imidazolium salt 10 has been identified as a precursor of the corresponding N,N′-unsymmetrical N-heterocyclic carbene ligand, whose complex with palladium catalyzed the intramolecular amide enolate α-arylation leading to oxindole 45 in excellent yield but with low enantioselectivity.
- Malkov, Andrei V.,Stewart-Liddon, Angus J.P.,Teply, Filip,Kobr, Luká?,Muir, Kenneth W.,Haigh, David,Ko?ovsky, Pavel
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p. 4011 - 4025
(2008/09/20)
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- Modular synthesis of heterocyclic carbene precursors
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A series of N-heterocyclic carbene precursors, containing an imidazoline or tetrahydropyrimidine framework, were prepared from ω-chloroalkanoyl chlorides. The sequential attachment of nitrogen nucleophiles and subsequent ring closure gave, depending on the reagents used, either the desired dihydroimidazolium and tetrahydropyrimidinium salts or their parent heterocycles. In this latter case, the second substituent was introduced in an alkylation step. The preparation of carbene precursors bearing chiral or bulky substituents was achieved with comparable efficiency.
- Paczal, Attila,Benyei, Attila C.,Kotschy, Andras
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p. 5969 - 5979
(2007/10/03)
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- Steric variations between the synthesis of a stable chiral C 2-symmetric diimidazolidinylidene and an electron-rich tetraazafulvalene
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C2-Symmetric electron-rich olefin dimers and imidazolidinylidene ligands with a 2,2-dimethyl-1,3-dioxolane backbone were synthesised and characterised. The steric protection of the carbene dictates which product is obtained. Georg Thieme Verlag
- Marshall, Colin,Ward, Mark F.,Skakle, Janet M. S.
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p. 1040 - 1044
(2007/10/03)
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- Synthesis, structure-activity relationships, and anxiolytic activity of 7-aryl-6,7-dihydroimidazoimidazole corticotropin-releasing factor 1 receptor antagonists
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7-Aryl-6,7-dihydroimidazoimidazoles represent a novel series of high-affinity corticotropin-releasing factor 1 receptor antagonists. Here, we report their synthesis and SAR as well as behavioral activity of two exemplary compounds, 7b and 7k, in a mouse canopy model of anxiety.
- Han, Xiaojun,Michne, Jodi A.,Pin, Sokhom S.,Burris, Kevin D.,Balanda, Lynn A.,Fung, Lawrence K.,Fiedler, Tracey,Browman, Kaitlin E.,Taber, Matthew T.,Zhang, Jie,Dubowchik, Gene M.
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p. 3870 - 3873
(2007/10/03)
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- Synthesis and study of 1-aryl-1H-4,5-dihydroimidazoles
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An easy synthesis of 1-aryl-1H-4,5-dihydroimidazoles 1 by cyclocondensation of N-aryl-N′-formylethylenediamines 2 is described. Such precursors were synthesized by selective formylation of N-arylethylenediamines 3 with p-nitrophenyl formate. Cyclizations were performed using trimethylsilyl polyphosphate. Chemical properties of compounds 1, typical of amidine system, were studied. Reaction of 1 with methyl iodide leads to the corresponding 1-aryl-3-methyl-1H-4,5-dihydroimidazolium salts 5. Reduction of dihydroimidazoles 1 with sodium cyanoborohydride provides a convenient access to N-aryl-N′-methylethylenediamines 4.
- Perillo, Isabel,Caterina, M. Cristina,Lopez, Julieta,Salerno, Alejandra
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p. 851 - 856
(2007/10/03)
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