The Boomerang is Back in Olefin Metathesis

by Diana Stoianova on December 9, 2014

Bates, J. M.; Lummiss, J. A. M.; C.; Bailey; G. A., and Fogg, D. E. “Operation of the Boomerang Mechanism in Olefin Metathesis Reactions Promoted by the Second-Generation Hoveyda Catalyst” ACS Catal., 2014, 4 (7), 2387-94.

No consensus has been reached about the validity of the release-return or Boomerang mechanism involved in the metathesis reactions with the 2nd gen Hoveyda-Grubbs type catalysts despite the numerous studies on the subject. Basically, the views are divided between the two extremes:

  • Only a fraction of the precatalyst initiates and the uninitiated catalyst can be recovered after the reaction.
  • All the precatalyst initiates during the reaction and then is regenerated by reuptake by the Hoveyda ligand allowing for almost quantitative recovery.

Trying to resolve this long standing debate in the metathesis community, Deryn Fogg’s group undertook recently a new study revisiting previous experiments and addressing their deficiencies.

A prerequisite for the operation of the release-return mechanism is the ability of the Hoveyda ligand to compete with a large excess of the substrate and recapture the active catalyst during the catalytic cycle. Competition experiments showed that the styrenyl ether can inhibit the metathesis reaction even when present in small amounts under cross-metathesis or ring closing metathesis conditions indicating rapid uptake by the active catalyst in both early and late stages of the reactions.

Crossover studies with the 13C-labeled Hoveyda ligand (HL*) showed very efficient initiation as well as very rapid uptake of the styrenyl ether during cross metathesis reactions or RCM. Near equilibrium amount of the 13C-labeled HII* (47%) were reached.1 In contrast, the background reaction in the absence of metathesis substrates was much slower and reaches only 5% even at much higher catalyst concentrations.


These new results are pretty convincing in favor of the release-return mechanism. But no matter what, the fact is that the second gen Hoveyda can outperform the Grubbs catalyst in some challenging RCM reactions. The release-return mechanism can be one of the contributors to the higher productivity of this class of catalysts. Due to the ease of initiation and regeneration the Hoveyda pre-catalyst can be viewed as a reactive resting state species which protects the active catalyst from decomposition and readily re-enters the catalytic cycle.

1Uptake of HL* was measured without work up to exclude the possibility for accelerated regeneration during concentration.


Olefin Metathesis at the 248th ACS Meeting

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The 248th American Chemical Society National Meeting and Exposition will be held in San Francisco, California from August 10-14, 2014. The theme of this fall’s meeting is “Chemistry and Global Stewardship.” As olefin metathesis has made significant contributions to the responsible management of world resources, it is fitting that many notable presentations will be given. […]

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Examining Polytopal Rearrangements around Ruthenium

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Torker, S.; Khan, R.K.M.; Hoveyda, A.M. “The Influence of Anionic Ligands on Stereoisomerism of Ru Carbenes and Their Importance to Efficiency and Selectivity of Catalytic Olefin Metathesis Reactions” J. Am. Chem. Soc. 2014, 136, 3439-3455. For the past 15 years ruthenium catalysts have been a workhorse for olefin metathesis. Chemists have been able to tune […]

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Metathesis Featured at Modern Synthetic Methods & Chiral USA

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Modern Synthetic Methods & Chiral USA Resort Orlando-Celebration Hotel, Florida USA May 19–21, 2014 Scientific Update has created a 3-day conference and exhibition to bridge a gap between industry and academia. Since industry rarely devises new synthetic methods to perform each step in the synthetic route, the event will provide a forum where industry and […]

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Cooperation between a Organometallic Complex and a Metalloenzyme

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Denard, C. A.; Huang; H.; Bartlett, M. J., Lu, L.; Tan, Y.; Zhao, H.; and Hartwig, J. F. Angew. Chem. Int. Ed. 2014, 53, 465. Recently, the Hartwig group reported a tandem reaction in which a metalloenzyme and a metathesis catalyst worked cooperatively to yield products which cannot be generated in comparable yield by sequential […]

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Olefin Metathesis at the 247th ACS Meeting

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The 247th ACS National Meeting and Exposition is less than a month away. The late winter/early spring event is set for Dallas, Texas from March 16-20, 2014. Olefin metathesis has no problem fitting into the meeting’s theme of “Chemistry and Materials for Energy” and keeping with tradition, we here at All Things Metathesis will provide […]

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Ruthenium Initiators Deliver Syndiotactic Polymers

December 16, 2013

Keitz, B.K.; Fedorov, A.; Grubbs, R.H. “Cis-Selective Ring-Opening Metathesis Polymerization with Ruthenium Catalysts” J. Am. Chem. Soc. 2012, 134, 2040-2043. Rosebrugh, L.E.; Marx, V.M.; Keitz, B.K.; Grubbs, R.H. “Synthesis of Highly Cis, Syndiotactic Polymers via Ring-Opening Metathesis Polymerization Using Ruthenium Metathesis Catalysts” J. Am. Chem. Soc. 2013, 135, 10032-10035. Controlling the stereochemistry of ring opening […]

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