Olefin Metathesis allows the exchange of substituents between different olefins - a transalkylidenation.
This reaction was first used in petroleum reformation for the synthesis of higher olefins (Shell higher olefin process - SHOP), with nickel catalysts under high pressure and high temperatures. Nowadays, even polyenes with MW > 250,000 are produced industrially in this way.
Synthetically useful, high-yield procedures for lab use include ring closure between terminal vinyl groups, cross metathesis - the intermolecular reaction of terminal vinyl groups - and ring opening of strained alkenes. When molecules with terminal vinyl groups are used, the equilibrium can be driven by the ready removal of the product ethene from the reaction mixture. Ring opening metathesis can employ an excess of a second alkene (for example ethene), but can also be conducted as a homo- or co-polymerization reaction. The driving force in this case is the loss of ring strain.
All of these applications have been made possible by the development of new homogeneous catalysts. Shown below are some of these catalysts, which tolerate more functional groups and are more stable and easy to handle.
The Schrock catalysts are more active and are useful in the conversion of sterically demanding substrates, while the Grubbs catalysts tolerate a wide variety of functional groups.
The second generation Grubbs catalysts are even more stable and more active than the original versions. Some of these are depicted:
K. Grela, S. Harutyunyan, A. Michrowska, Angew. Chem. Int. Ed., 2002, 114, 4038. DOI
Mechanism of Olefin Metathesis
Advanced Fine-Tuning of Grubbs/Hoveyda Olefin Metathesis Catalysts: A Further Step toward an Optimum Balance between Antinomic Properties
M. Bieniek, R. Bujok, M. Cabaj, N. Lugan, G. Lavigne, D. Arlt, K. Grela, J. Am. Chem. Soc., 2006, 128, 13652-13653.
Allenylidene-to-Indenylidene Rearrangement in Arene-Ruthenium Complexes: A Key Step to Highly Active Catalysts for Olefin Metathesis Reactions
R. Castarlenas, C. Vovard, C. Fischmeister, P. H. Dixneuf, J. Am. Chem. Soc., 2006, 128, 4079-4089.
New Catalysts and Strategies for Alkene Metathesis
Heterocycle Construction by Grubbs Metathesis
Alkyne Metathesis in Synthesis: Syntheses of (+)-Ferrugine and Anatoxin-α
The Grubbs Reaction in Organic Synthesis