Ring‐Closing Metathesis

Lierop, Bianca J. van; Lummiss, Justin A. M.; Fogg, Deryn E.

doi:10.1002/9781118711613.ch3

Cited by 53 publications

(58 citation statements)

References 342 publications

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“…[8][9][10] Likewise, metathesis of amine-bearing substrates has long been known to require either Nprotection, 11 or an adjacent substituent to block access to and/or withdraw electron density from the nitrogen site. [5][6][7] The Cossy group recently extended the latter strategy to metathesis of N-heteroaromatic compounds. 12 For protected amines, a survey of recent examples [13][14][15][16][17][18][19][20][21] illustrates moderate to excellent metathesis yields.…”

Section: Chart 1 Metathesis Catalysts Discussed and The Resting-stamentioning

confidence: 99%

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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: Chart 1 Metathesis Catalysts Discussed and The Resting-stamentioning

confidence: 99%

“…Notwithstanding the importance of metathesis in the synthesis of alkaloids and other nitrogen heterocycles, 4 however, compounds bearing sterically accessible nitrogen sites challenge the functional-group tolerance of these catalysts. [5][6][7] …”

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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“…For isocyanide III,a ni nteresting and counterintuitivet rend was observed (Table 1, entries [16][17][18]: the less III used, the better were the results. The optimal amount turned out to be approximately 0.7 equivalents of the compound, or 2.2 equivalents of isocyanide groups, with respect to ruthenium.…”

Section: Introductionmentioning

confidence: 99%

“…The resultant product 4b contained 40 ppm of ruthenium (Table 1, entry 5). Scavengers I-III gave much better results (Table 1, entries [7][8][9][10][11][12][13][14][15][16][17][18][19]. The use of II (4.4 equiv) reduced the residual ruthenium content by two orders of magnitudew ith respect to the control experiment, down to 1.6 ppm ( Table 1, entry 12).…”

Section: Introductionmentioning

confidence: 99%

“…It creates carbon-carbon double bonds under mild conditions, with high yield and selectivity. [18] It has been used in the total synthesis of aw ide variety of natural compounds [19] and increasingly finds its way into the syntheses of pharmaceutical products. [20] Over the last 20 years, tremendous progress was made in the design of new OM catalysts.…”

Section: Introductionmentioning

confidence: 99%

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High‐Performance Isocyanide Scavengers for Use in Low‐Waste Purification of Olefin Metathesis Products

Szczepaniak

Urbaniak²,

Wierzbicka³

et al. 2015

ChemSusChem

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Alkene Cross‐Metathesis Reactions

et al. 2021

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This chapter describes olefin cross‐metathesis (CM) reactions catalyzed by ruthenium, molybdenum, and tungsten complexes and surveys the literature from 1993 through 2020. Cross‐metathesis has been applied to the synthesis of a wide range of functionalized alkenes, including natural and biologically active products. Due to its simplicity and inherit atom economy, CM has found applications in the preparation of fine chemicals and various building blocks, and in transformations of biomass. Tandem reactions involving CM as the key step are also reviewed. Examples discussed in this chapter serve to illustrate how the reactivity of alkene substrates in CM depends on the presence of functional groups and steric congestion in the proximity of the reacting double bonds. A discussion of the mechanism of olefin metathesis is also included.

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Ring‐Closing Metathesis

Cited by 53 publications

References 342 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

High‐Performance Isocyanide Scavengers for Use in Low‐Waste Purification of Olefin Metathesis Products

Alkene Cross‐Metathesis Reactions

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