Synthesis and Reactivity of Olefin Metathesis Catalysts Bearing Cyclic (Alkyl)(Amino)Carbenes

Anderson, Donde R.; Lavallo, Vincent; O’Leary, Daniel J.; Bertrand, Guy; Grubbs, Robert H.

doi:10.1002/ange.200702085

Cited by 39 publications

(20 citation statements)

References 21 publications

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“…[6a, 40c] To prove that this "sleeping" catalyst is not a bystander but actually takes part in the reaction, [40,45] we carried out a simple crossover experiment. According to established procedures, [46] the labelled complexes [D 7 ]Hov-II and [D 7 ]Gre-II (99 % D atom) were prepared.…”

Section: H T U N G T R E N N U N G (=Chph)a C H T U N G T R E N N U Nmentioning

confidence: 99%

In an Attempt to Provide a User's Guide to the Galaxy of Benzylidene, Alkoxybenzylidene, and Indenylidene Ruthenium Olefin Metathesis Catalysts

Bieniek

Michrowska

Usanov

et al. 2008

Chemistry A European J

223

158

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The data reported in this paper demonstrate that great care must be taken when choosing an appropriate catalyst for a given metathesis reaction. First-generation catalysts were found to be useful in the metathesis of sterically unhindered substrates. Second-generation catalysts (under optimised conditions) showed good to excellent activities toward sterically hindered and electron-withdrawing group (EWG)-substituted alkenes that do not react using the first-generation complexes. A strong temperature effect was noted on all of the reactions tested. Interestingly, attempts to force a reaction by increasing the catalyst loading were much less effective. Therefore, when possible, it is suggested that metathesis transformations should be carried out with a second-generation catalyst at 70 degrees C in toluene. However, different second-generation catalysts proved to be optimal for different applications and no single catalyst outperformed all others in all cases. Nevertheless, some empirical rules can be deduced from the model experiments, providing preliminary hints for the selection of the optimal catalysts.

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Section: H T U N G T R E N N U N G (=Chph)a C H T U N G T R E N N U Nmentioning

confidence: 99%

In an Attempt to Provide a User's Guide to the Galaxy of Benzylidene, Alkoxybenzylidene, and Indenylidene Ruthenium Olefin Metathesis Catalysts

Bieniek

Michrowska

Usanov

et al. 2008

Chemistry A European J

223

158

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“…[7b-e, [10][11][12][13][14][15][16][17] Other unsymmetrical carbenic frameworks that have been recently incorporated in ruthenium-based catalysts include a series of cyclicA C H T U N G T R E N N U N G (alkyl)A C H T U N G T R E N N U N G (amino) carbenes, [18] and thiazole-2-ylidenes. [19] Unsymmetrical NHC frameworks, especially those with an aliphatic amino side group, were initially used in order to increase the electron-donating ability of the NHCs and, therefore, enhance the catalytic activity of the corresponding complexes.…”

Section: Introductionmentioning

confidence: 99%

Ruthenium‐Based Olefin Metathesis Catalysts Coordinated with Unsymmetrical N‐Heterocyclic Carbene Ligands: Synthesis, Structure, and Catalytic Activity

Vougioukalakis

Grubbs

2008

Chemistry A European J

Self Cite

107

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A series of ruthenium-based olefin metathesis catalysts coordinated with unsymmetrical N-heterocyclic carbene (NHC) ligands has been prepared and fully characterized. These complexes are readily accessible in one or two steps from commercially available [(PCy(3))(2)Cl(2)Ru==CHPh]. All of the complexes reported herein promote the ring-closing of diethyldiallyl and diethylallylmethallyl malonate, the ring-opening metathesis polymerization of 1,5-cyclooctadiene, and the cross metathesis of allyl benzene with cis-1,4-diacetoxy-2-butene, in some cases surpassing in efficiency the existing second-generation catalysts. Especially in the cross metathesis of allyl benzene with cis-1,4-diacetoxy-2-butene, all new catalysts demonstrate similar or higher activity than the second-generation ruthenium catalysts and, most importantly, afford improved E/Z ratios of the desired cross-product at conversion above 60 %. The influence of the unsymmetrical NHC ligands on the initiation rate and the activation parameters for the irreversible reaction of these ruthenium complexes with butyl vinyl ether were also studied. Finally, the synthesis of the related chlorodicarbonyl(carbene) rhodium(I) complexes allowed for the study of the electronic properties of the new unsymmetrical NHC ligands that are discussed in detail.

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“…Complexes of cyclic (alkyl)(amino)carbenes 4 (CAACs) [8] and of di(amido)-carbenes 5 (DACs) [9] have demonstrated interesting activities and selectivities for several ring-closing metathesis and cross-metathesis reactions. [10–12] For instance, DAC-ruthenium complex 5 catalyzes the ring-closing metathesis (RCM) of tetra-substituted olefins, a challenging transformation that is accomplished by only a limited range of metathesis catalysts. [11,13] However, note that this was found to be also the case for catalyst 6 , which bears a non-electrophilic NHC with a similar steric environment to 5 .…”

mentioning

confidence: 99%

“…The Ru1–C1 (192.6 pm) and Ru1–O1 (232.4 pm) bond lengths are comparable to those in CAAC-complexes 4 . [10] In contrast, the tetrahydropyrimidin-2-ylidene complex 6 features a significantly longer Ru1–C1 bond length (204.8 pm). [11] This is consistent with an increased double bond character of the metal-carbene bond of the anti-Bredt NHC complex, which is due to the superior π-accepting capabilities of the carbene.…”

mentioning

confidence: 99%

“…This was interpreted as the result of negative steric interactions, which would prevent the alkyl groups of the quaternary carbon of CAAC to approach the benzylidene proton. [10] This explanation is clearly irrelevant in the case of the anti-Bredt NHC ligand, which features a non-bulky distorted amino group in place of the quaternary carbon of CAACs. The preferred conformation of 7 in the solid state could be governed by unfavorable steric interactions between the chlorides and the N-2,6-di(isopropyl)phenyl groups.…”

mentioning

confidence: 99%

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A Ruthenium Catalyst for Olefin Metathesis Featuring an Anti‐Bredt N‐Heterocyclic Carbene Ligand

et al. 2016

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A ruthenium complex bearing an “anti-Bredt” N-heterocyclic carbene was synthesized, characterized and evaluated as a catalyst for olefin metathesis. Good conversions were observed at room temperature for the formation of di- and tri-substituted olefins by ring-closing metathesis. It also allowed for the ring-opening metathesis polymerization of cyclooctadiene, as well as for the cross-metathesis of cis-1,4-diacetoxy-2-butene with allyl-benzene, with enhanced Z/E kinetic selectivity over classical NHC-based catalysts.

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Synthesis and Reactivity of Olefin Metathesis Catalysts Bearing Cyclic (Alkyl)(Amino)Carbenes

Cited by 39 publications

References 21 publications

In an Attempt to Provide a User's Guide to the Galaxy of Benzylidene, Alkoxybenzylidene, and Indenylidene Ruthenium Olefin Metathesis Catalysts

In an Attempt to Provide a User's Guide to the Galaxy of Benzylidene, Alkoxybenzylidene, and Indenylidene Ruthenium Olefin Metathesis Catalysts

Ruthenium‐Based Olefin Metathesis Catalysts Coordinated with Unsymmetrical N‐Heterocyclic Carbene Ligands: Synthesis, Structure, and Catalytic Activity

A Ruthenium Catalyst for Olefin Metathesis Featuring an Anti‐Bredt N‐Heterocyclic Carbene Ligand

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