Olefin Metathesis Reactions: From a Historical Account to Recent Trends

Astruc, Didier

doi:10.1002/9781118711613.ch1

Cited by 6 publications

(4 citation statements)

References 284 publications

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“…Olefin metathesis offers exceptional power and efficiency in the assembly of carbon–carbon bonds . The development of readily handled, highly active ruthenium catalysts (preeminently the second-generation Grubbs and Hoveyda catalysts GII and HII ; Chart ) , led to widespread uptake of these methodologies in organic synthesis. Notwithstanding the importance of metathesis in the synthesis of alkaloids and other nitrogen heterocycles, however, compounds bearing sterically accessible nitrogen sites challenge the functional-group tolerance of these catalysts. − …”

Section: Introductionmentioning

confidence: 99%

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: Introductionmentioning

confidence: 99%

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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“…Among many possible catalyst designs that can be used to introduce our principle of host–guest catalyst removal, Ru-based olefin metathesis catalysts are suitable catalyst systems due to their practical utility in wide areas and high stability of the resulting precatalysts toward air and moisture. Olefin metathesis itself represents a ubiquitous chemical transformation for the formation of carbon–carbon double bonds in the presence of a transition-metal catalyst. , In particular, Ru-based olefin metathesis catalysts have garnered a strong following mainly due to the low oxophilicity of Ru and their tolerance toward polar functional groups, impurities, and solvents, including water. The most frequently used Ru-based olefin metathesis catalyst is the Hoveyda–Grubbs second-generation catalyst, which possesses metal alkylidene and N -heterocyclic carbene (NHC) ligands. , …”

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confidence: 99%

Removable Water-Soluble Olefin Metathesis Catalyst via Host–Guest Interaction

2018

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A highly removable N-heterocyclic carbene ligand for a transition-metal catalyst in aqueous media via host-guest interactions has been developed. Water-soluble adamantyl tethered ethylene glycol in the ligand leads a hydrophobic inclusion into the cavity of β-cyclodextrin. Ruthenium (Ru) olefin metathesis catalyst with this ligand demonstrated excellent performance in various metathesis reactions in water as well as in CHCl, and removal of residual Ru was performed via filtration utilizing a host-guest interaction and extraction.

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“…Furthermore, the installation of o -isopropoxybenzylidene ligand led to an even more stable and productive, phosphine-free second generation of Hoveyda–Grubbs catalysts ( Ru3–Ru6 , Scheme 2b). 27…”

Section: Resultsmentioning

confidence: 99%