Ruthenium carbene complexes with imidazolin-2-ylidene ligands allow the formation of tetrasubstituted cycloalkenes by RCM

Ackermann, Lutz; Fürstner, Alois; Weskamp, Thomas; Kohl, Florian J.; Herrmann, Wolfgang A.

doi:10.1016/s0040-4039(99)00919-3

Cited by 408 publications

(143 citation statements)

References 32 publications

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“…[13] Various homo-and heterobimetallic ruthenium-alkylidene complexes were also successfully employed to promote the ROMP of cyclooctene and norbornene or norbornadiene derivatives, [16] the self-metathesis of cis-2-pentene, [12] and the ring-closing metathesis (RCM) of a,w-dienes. [15,36] For this last application, they displayed excellent activities in the formation of tri-or even tetrasubstituted cycloalkene products, a performance that could not be achieved with the monometallic complex 1a. In sharp contrast with these trends, homobimetallic ruthenium-indenylidene compound 5 (now 11) was repeatedly found to be a less efficient catalyst than its monometallic parent in the ring-closing metathesis of several dienes.…”

Section: Catalytic Studiesmentioning

confidence: 99%

Homobimetallic Ruthenium Vinylidene, Allenylidene, and Indenylidene Complexes: Synthesis, Characterization, and Catalytic Studies

et al. 2009

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Four homobimetallic ruthenium-(pcymene) complexes bearing a tricyclohexylphosphine ligand and polyunsaturated carbon-rich fragments were obtained via a vinylidene-allenylidene-indenylidene cascade pathway from the ethylene complex. All the products were isolated and fully characterized by IR and NMR spectroscopies. The molecular structure of the indenylidene complex 11 was determined by X-ray crystallographic analysis. The catalytic activity of the four complexes was probed in various types of olefin metathesis reactions and compared with those of a related homobimetallic ruthenium-benzylidene complex, as well as first, second, and third generation monometallic Grubbs catalysts. In the ring-closing metathesis (RCM) of diethyl di-A C H T U N G T R E N N U N G allylmalonate, the homobimetallic ruthenium-indenylidene complex 11 outperformed all the rutheniumbenzylidene complexes under investigation and was only slightly less efficient than its monometallic parent. Cross-metathesis experiments with ethylene showed that deactivation of ruthenium-benzylidene or indenylidene complexes was due to the rapid bimolecular decomposition of methylidene active species into ethylene complex 7a. Vinylidene and allenylidene complexes were far less efficient catalyst precursors for ring-opening metathesis polymerization (ROMP) or RCM and remained inert under an ethylene atmosphere. Their catalytic activity was, however, substantially enhanced upon addition of an acidic co-catalyst that most likely promoted their in situ transformation into indenylidene species. Due to its straightforward synthesis and high metathetical activity, homobimetallic ruthenium-indenylidene complex 11 is a valuable intermediate for the preparation of the Hoveyda-Grubbs catalyst A C H T U N G T R E N N U N G [Cl 2 RuA C H T U N G T R E N N U N G (PCy 3 )(=CH-o-O-i-PrC 6 H 4 )] via stoichiometric cross-metathesis with 2-isopropoxystyrene. The procedure did not require any sacrificial phosphine and the transition metal not incorporated into the final product was easily recovered and recycled at the end of the process.

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Section: Catalytic Studiesmentioning

confidence: 99%

Homobimetallic Ruthenium Vinylidene, Allenylidene, and Indenylidene Complexes: Synthesis, Characterization, and Catalytic Studies

et al. 2009

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“…At room temperature the selectivity is [14] Under these conditions, Suzuki coupling reactions of other substrates give little or no products in the absence of phosphane ligands. [15] ] for the model compounds as depicted in Equation (1). [a] Model compound…”

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confidence: 99%

Highly Active Ruthenium Catalysts for Olefin Metathesis: The Synergy of N‐Heterocyclic Carbenes and Coordinatively Labile Ligands

Weskamp

Kohl

Hieringer

et al. 1999

Angewandte Chemie Intl Edit

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465

164

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“…NHCs with unsaturated backbones have a longer history; ruthenium carbene complexes with NHCs bearing N-cyclohexyl groups were even amongst the first 2 nd generation catalysts to be described in the literature. [12] In addition, Grubbstype metathesis catalysts with "unsaturated" NHCs bearing an N-alkyl as well as an N-aryl group have thoroughly been reported in the literature by Fürstner et al [13] and Grubbs et al [14] It was shown that substantial structural variations can be accommodated at the NHC ligand and eventually lead to designer catalysts with tailor-made properties. As "saturated" NHCs generally afford more active metathesis initiators than "unsaturated" ones, [15] we were hoping to successfully contribute to the continuous search for more efficient catalysts.…”

Section: Introductionmentioning

confidence: 99%

Comparative Investigation of Hoveyda–Grubbs Catalysts bearing Modified N‐Heterocyclic Carbene Ligands

et al. 2007

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This paper reports the structural modification of Hoveyda-Grubbs complexes through the introduction of either an N-alkyl-N'-mesityl heterocyclic carbene, an N-alkyl-N'-(2,6-diisopropylphenyl) heterocyclic carbene, or an N-alkyl-N'-alkyl heterocyclic carbene. The effect of the modified N-heterocyclic carbene (NHC) ligand was investigated in representative ring-opening metathesis polymerization (ROMP), ring-closing metathesis (RCM) and cross metathesis (CM) reactions. A pronounced influence on both catalyst activity and selectivity was found to be exerted by the NHC amino substituents, which emphasizes that a rigorously selected steric environment is critical in olefin metathesis catalyst design.

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Ruthenium carbene complexes with imidazolin-2-ylidene ligands allow the formation of tetrasubstituted cycloalkenes by RCM

Cited by 408 publications

References 32 publications

Homobimetallic Ruthenium Vinylidene, Allenylidene, and Indenylidene Complexes: Synthesis, Characterization, and Catalytic Studies

Homobimetallic Ruthenium Vinylidene, Allenylidene, and Indenylidene Complexes: Synthesis, Characterization, and Catalytic Studies

Highly Active Ruthenium Catalysts for Olefin Metathesis: The Synergy of N‐Heterocyclic Carbenes and Coordinatively Labile Ligands

Comparative Investigation of Hoveyda–Grubbs Catalysts bearing Modified N‐Heterocyclic Carbene Ligands

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