Amine‐Mediated Degradation in Olefin Metathesis Reactions that Employ the Second‐Generation Grubbs Catalyst

Lummiss, Justin A. M.; Ireland, Benjamin J.; Sommers, Jacob M.; Fogg, Deryn E.

doi:10.1002/cctc.201300861

Cited by 60 publications

(65 citation statements)

References 37 publications

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“…They carry further weight given that HII functions as not only the pre-catalyst, but also a key resting state during metathesis. 33 Despite the presence of the oxygen donor in the styrenyl ether ligand, the chemistry of HII itself was found to parallel that previously communicated 26 for reaction of GII with a subset of these donors.…”

Section: Resultsmentioning

confidence: 83%

“…The analogous mono-amine complex was not observed for GII, but reportedly formed via loss of amine on drying GIIf 2 under vacuum. 25,26 Ensuing benzylidene abstraction by f was slightly faster than in the GII system. 26 Loss of alkylidene was complete after 12 h at RT (vs. 95% for GII), and the diagnostic methylene singlet for the amine product NH( n Bu)(CH 2 Ar) 1 (Ar = C 6 H 4 -o-O i Pr) was evident at 3.93 ppm (0.8 equiv vs. starting HII).…”

Section: Adduct Formation On Reaction Of Hii With N-donorsmentioning

confidence: 98%

“…25,26 Ensuing benzylidene abstraction by f was slightly faster than in the GII system. 26 Loss of alkylidene was complete after 12 h at RT (vs. 95% for GII), and the diagnostic methylene singlet for the amine product NH( n Bu)(CH 2 Ar) 1 (Ar = C 6 H 4 -o-O i Pr) was evident at 3.93 ppm (0.8 equiv vs. starting HII). 35 The corresponding reactions with benzylamine g proceeded similarly, affording mono-and bis-amine derivatives HIIg and HIIg 2 (Scheme 3; Table 1).…”

Section: Adduct Formation On Reaction Of Hii With N-donorsmentioning

confidence: 98%

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Decomposition of a Phosphine-Free Metathesis Catalyst by Amines and Other Bronsted Bases: Metallacyclobutane Deprotonation as a Major Deactivation Pathway

2015

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Reactions are described of the second-generation Hoveyda catalyst HII with amines, pyridine, and DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), in the presence and absence of olefin substrates. These nitrogen bases have a profoundly negative impact on metathesis yields, but in most cases are innocuous toward the pre-catalyst. HII adducts were formed by primary and secondary amines (n-butylamine, sec-butylamine, benzylamine, pyrrolidine, morpholine), pyridine, and DBU at room temperature. No reaction was evident for NEt 3 , even at 60 °C. On longer reaction at RT, unencumbered primary amines abstract the benzylidene ligand from HII. With 10 equiv NH 2 n Bu, this process was complete in 12 h, affording NH n Bu(CH 2 Ar) (Ar = o-C 6 H 4 -O i Pr) and [RuCl(H 2 IMes)(NH 2 n Bu) 4 ]Cl. For benzylamine, benzylidene abstraction occurred over days at RT. No such reaction was observed for sec-butylamine, secondary amines, NEt 3 , pyridine, or DBU. All of these bases, however, strongly inhibited metathesis of styrene by HII, with a general trend toward more deleterious effects with higher Bronsted basicity. Studies at 10 mol% HII and 10 equiv DBU, NEt 3 , and pyrrolidine (60 °C, C 6 D 6 ) indicated that the primary mechanism for decomposition involved base-induced deprotonation of the metallacyclobutane intermediate, rather than the Lewis base-mediated decomposition pathways previously established for the Grubbs catalysts. In the corresponding metathesis of ethylene, this decomposition process is rapid even at RT, highlighting the vulnerability of the monosubstituted metallacyclobutane.

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Section: Resultsmentioning

confidence: 83%

Section: Adduct Formation On Reaction Of Hii With N-donorsmentioning

confidence: 98%

Section: Adduct Formation On Reaction Of Hii With N-donorsmentioning

confidence: 98%

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Decomposition of a Phosphine-Free Metathesis Catalyst by Amines and Other Bronsted Bases: Metallacyclobutane Deprotonation as a Major Deactivation Pathway

2015

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“…This observation indicates the importance of the stability of metathesis catalysts toward impurities when large scale reactions are performed with ppm levels of catalyst . Recent work on the degradation pathway show that catalysts containing a phosphine group undergo displacement of the phosphine by an amine, followed by an attack of the ruthenium alkylidene species by the phosphine . For catalysts without phosphine, the Bronsted–Lowry base deprotonates the metallacyclobutane that is formed in the catalytic cycle .…”

Section: Parameters Influencing the Turnover Number Of Methyl Oleatementioning

confidence: 99%

The Future of Ethenolysis in Biobased Chemistry

et al. 2016

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The desire to utilise biobased feedstocks and develop more sustainable chemistry poses new challenges in catalysis. A synthetically useful catalytic conversion is ethenolysis, a cross metathesis reaction with ethylene. In this Review, the state of the art of ethenolysis in biobased chemistry was extensively examined using methyl oleate as a model compound for fatty acids. Allied to this, the ethenolysis of fatty acid, polymers and more challenging substrates are reviewed. To determine the limiting factors for the application of ethenolysis on biomass, the influence of reaction parameters were investigated and the bottlenecks for reaching high turnover numbers identified.

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“…This seems to indicate that other decomposition routes are worth considering in phosphine‐free conditions . The formation of ruthenium amine complexes and the detrimental effect of the presence of amines in olefin metathesis reactions performed with Grubbs and Hoveyda catalysts observed during the scale‐up production of BILN 2061 ZW drug was recently analyzed in detail by Fogg and co‐workers,, as was the implication of other types of common impurities in industrial processes …”

Section: Mechanism and Limitationsmentioning

confidence: 94%

Ethenolysis: A Green Catalytic Tool to Cleave Carbon–Carbon Double Bonds

Bidange

Fischmeister

Bruneau

2016

Chemistry A European J

118

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Remarkable innovations have been made in the field of olefin metathesis due to the design and preparation of new catalysts. Ethenolysis, which is cross-metathesis with ethylene, represents one catalytic transformation that has been used with the purpose of cleaving internal carbon-carbon double bonds. The objectives were either the ring opening of cyclic olefins to produce dienes or the shortening of unsaturated hydrocarbon chains to degrade polymers or generate valuable shorter terminal olefins in a controlled manner. This Review summarizes several aspects of this reaction: the catalysts, their degradation in the presence of ethylene, some parameters driving their productivity, the side reactions, and the applications of ethenolysis in organic synthesis and in potential industrial applications.

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Amine‐Mediated Degradation in Olefin Metathesis Reactions that Employ the Second‐Generation Grubbs Catalyst

Cited by 60 publications

References 37 publications

Decomposition of a Phosphine-Free Metathesis Catalyst by Amines and Other Bronsted Bases: Metallacyclobutane Deprotonation as a Major Deactivation Pathway

Decomposition of a Phosphine-Free Metathesis Catalyst by Amines and Other Bronsted Bases: Metallacyclobutane Deprotonation as a Major Deactivation Pathway

The Future of Ethenolysis in Biobased Chemistry

Ethenolysis: A Green Catalytic Tool to Cleave Carbon–Carbon Double Bonds

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