Operation of the Boomerang Mechanism in Olefin Metathesis Reactions Promoted by the Second-Generation Hoveyda Catalyst

Three new ruthenium phosphonium alkylidene complexes incorporating N-heterocyclic carbene ligands with bulky N-aryl groups (2,6-diethyl, L = 1,3-bis(2,6-diethylphenyl)imidazolin-2-ylidene (H2IDEP) and 2,6-diisopropyl, L = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene (H2ID-i-PP)) were synthesized and characterized. The H2ID-i-PP supported complex was found to exhibit excellent thermal stabilities relative to the parent N-mesityl (N-Mes) complexes as well as the H2IDEP supported complexes. All three phosphonium alkylidenes were evaluated in comparison to the N-Mes derivative and Grubbs second generation catalyst using standard olefin metathesis reactions and conditions. The complex containing the bulky H2ID-i-PP ligand was found to have excellent activity and longevity in comparison to the other catalysts. Although initiation rates were slow for this sterically bulky precatalyst, its superior activity led to the best overall efficiency in test reactions.

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

ChemCatChem ◽

10.1002/cctc.201300861 ◽

2014 ◽

Vol 6 (2) ◽

pp. 459-463 ◽

Cited By ~ 38

Author(s):

Justin A. M. Lummiss ◽

Benjamin J. Ireland ◽

Jacob M. Sommers ◽

Deryn E. Fogg

Keyword(s):

Olefin Metathesis ◽

Second Generation ◽

Grubbs Catalyst ◽

Metathesis Reactions

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Catalytic Carbonyl-Olefin Metathesis of Aliphatic Ketones: Iron(III) HomoDimers as Lewis Acidic Superelectrophiles

10.26434/chemrxiv.7130801.v1 ◽

2018 ◽

Author(s):

Haley Albright ◽

Paul S. Riehl ◽

Christopher C. McAtee ◽

Jolene P. Reid ◽

Jacob R. Ludwig ◽

...

Keyword(s):

Lewis Acid ◽

Olefin Metathesis ◽

Acid Activation ◽

Lewis Acid Catalysts ◽

Distinct Mode ◽

Aliphatic Ketones ◽

Carbon Carbon Bond ◽

Metathesis Reactions ◽

Acid Catalyzed

<div>Catalytic carbonyl-olefin metathesis reactions have recently been developed as a powerful tool for carbon-carbon bond</div><div>formation. However, currently available synthetic protocols rely exclusively on aryl ketone substrates while the corresponding aliphatic analogs remain elusive. We herein report the development of Lewis acid-catalyzed carbonyl-olefin ring-closing metathesis reactions for aliphatic ketones. Mechanistic investigations are consistent with a distinct mode of activation relying on the in situ formation of a homobimetallic singly-bridged iron(III)-dimer as the active catalytic species. These “superelectrophiles” function as more powerful Lewis acid catalysts that form upon association of individual iron(III)-monomers. While this mode of Lewis acid activation has previously been postulated to exist, it has not yet been applied in a catalytic setting. The insights presented are expected to enable further advancement in Lewis acid catalysis by building upon the activation principle of “superelectrophiles” and broaden the current scope of catalytic carbonyl-olefin metathesis reactions.</div>

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