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Highly Efficient Ruthenium CAAC Complexes for Olefin Metathesis developed by Apeiron

Cyclic alkyl amino carbene (CAAC) ruthenium catalysts for olefin metathesis

The introduction of Grubb’s 2nd generation metathesis catalyst nearly 20 years ago demonstrated the ability of NHC-containing ruthenium catalysts to provide enhanced selectivity and higher turnover numbers (TON) compared to the phosphine-based ligands of Generation 1.1  More recently, a related ligand platform, cyclic alkyl amino carbenes (CAACs), has received significant attention in olefin metathesis.  These investigations have shown CAAC-containing catalysts to have enhanced selectivity and unprecedented catalyst lifetimes in several industrially relevant applications.2,3,4


Figure 1. CAAC metathesis catalysts now available from Strem (44-0775 & 44-0778)

In partnership with Apeiron Synthesis, Strem offers bis- and mono-CAAC Ruthenium- catalysts which have proven to be versatile synthetic tools for use in cross-metathesis, ring-closing metathesis, and ring-opening metathesis polymerization (ROMP).5  The high stability of these systems enables handling in air and remarkably high turnover numbers (TON = 300000 with 1-decene).  Scheme 1 shows exceptional performance of the bis-CAAC system UltraCat (cat. #44-0775) in ethenolysis of methyl oleate compared to the NHC-containing Grubbs II catalyst.    


Scheme 1.  Comparison of catalyst performance in ethenolysis of methyl oleate.

Substitution of ruthenium benzylidene complexes with a judiciously selected CAAC ligand provides a remarkable enhancement in cross metathesis of electron-deficient substrates compared to the related NHC-substituted benzylidene complex, nitro-Grela (scheme 2).  UltraNitroCat (cat. #44-0778) also showed a significant advantage in ring-closing metathesis (scheme 3).  Importantly, these reactions are likely of interest for application across specialty chemicals, pharmaceutical, and F&F industries (Flagrance and Flavors).       


Scheme 2.  Performance of mono-CAAC NHC-substituted catalysts in cross-metathesis with acrylonitrile.


Scheme 3.  UltraNitroCat outperforms well-known NHC catalysts in ring-closing metathesis. 



  1.       Org. Lett. 1999, 1, 953-956.
  2.       Organometallics 2008, 27, 563-566.
  3.       ACS Catal. 2017, 7, 7634-7637.
  4.       Angew. Chem. Int. Ed. 2015, 54, 1919-1923.
  5.       ACS Catal. 2017, 7, 5443-5449.


Featured Products:

44-0775 Bis(1-(2,6-diethylphenyl)-3,5,5-trimethyl-3-phenylpyrrolidin-2-ylidene)(3-phenyl-1H-inden-1-ylidene)ruthenium(II) dichloride UltraCat (2055540-61-7)

44-0778  (1-(2,6-Diethylphenyl)-3,5,5-trimethyl-3-phenylpyrrolidin-2-ylidene)(2-isopropoxy-5-nitrobenzylidene)ruthenium(II) dichloride UltraNitroCat (2106819-64-9)


Visit the links below to view additional details on our website:

Metathesis Catalysts
Apeiron Metathesis Catalyst Kit
Selected Ruthenium Metathesis Catalysts




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