Olefin metathesis



Olefin metathesis or transalkylidenation (in some literature, a organic synthesis".[2]

The reaction is alkylidene fragments. The general scope is outlined by the following equation:

Overview

Olefin metathesis was first used in petroleum reformation for the synthesis of higher olefins from the products (α-olefins) from the Shell higher olefin process (SHOP) under high pressure and high temperatures. Many traditional catalysts are derived from a reaction of the metal halides with alkylation agents for example WCl6-EtOH-EtAlCl2. A metathesis reaction is a chain reaction that begins when a metallocarbene and an olefin react to form a metallacyclobutane. This intermediate then reacts further, decomposing into a new olefin (the product) and a new metallocarbene, which can then be recycled through the reaction pathway.

The alkyne metathesis and related polymerizations.

Reaction mechanism

Hérison and Chauvin first proposed the widely accepted mechanism of transition metal alkene metathesis.[5] The direct [2+2] cycloaddition of two alkenes is formally d-orbitals on the metal catalyst lowers the activation energy enough that the reaction can proceed rapidly at modest temperatures.

Metathesis chemistry

Some important classes of metathesis chemistry:

Like most organometallic reactions, the metathesis pathway is usually driven by a thermodynamic imperative; that is, the final products are determined by the energetics of the possible products, with a distribution of products proportional to the exponential of their respective energy values.

Alkene metathesis is generally driven by the evolution of gaseous ethylene; and alkyne metathesis is driven by the evolution of Thorpe-Ingold effect may be exploited to improve both reaction rates and selectivity.

Alkene metathesis is synthetically equivalent to (and has replaced) a procedure of ozonolysis of an alkene to two ketone fragments followed by the reaction of one of them with a Wittig reagent.

Scope

One study reported a ring-opening cross-olefin metathesis based on a Hoveyda-Grubbs Catalyst:[6]

The metathesis reaction of 1-hexene with the WCl4(OAr)2 catalyst yields 5-decene[7] plus many byproducts from secondary metathesis reactions.

References

  1. ^ Astruc D. (2005). ""The metathesis reactions: from a historical perspective to recent developments"" (abstract). New J. Chem. 29 (1): 42–56.
  2. ^ Nobelprize.org (5 Oct 2005). "The Nobel Prize in Chemistry 2005". Press release.
  3. ^ Ileana Dragutan*, Valerian Dragutan*, Petru Filip (2005). "Recent developments in design and synthesis of well-defined ruthenium metathesis catalysts – a highly successful opening for intricate organic synthesis".. 105. From Arkivoc.
  4. ^ R.R. Schrock* (1986). "High-oxidation-state molybdenum and tungsten alkylidene complexes". Acc. Chem Res.
  5. ^ Hérisson, J.-L.; Chauvin, Y. Macromol. Chem. 1970, 141, 161.
  6. ^ A Recyclable Chiral Ru Catalyst for Enantioselective Olefin Metathesis. Efficient Catalytic Asymmetric Ring-Opening/Cross Metathesis in Air Joshua J. Van Veldhuizen, Steven B. Garber, Jason S. Kingsbury, and J. Am. Chem. Soc.; 2002; 124(18) pp 4954 - 4955; (Communication) doi:10.1021/ja020259c
  7. ^ Ione M. Baibich, Carla Kern (2002). ""Reactivity of Tungsten-aryloxides with Hydrosilane Cocatalysts in Olefin Metathesis"". Journal of the Brazilian Chemical Society 13 (1): 43–46.

Further reading

  1. (2002) "Olefin Metathesis: Big-Deal Reaction". Chemical & Engineering News 80 (51): 29-33.
  2. (2002) "Olefin Metathesis: The Early Days". Chemical & Engineering News 80 (51): 34-38.
  3. Acc. Chem. Res. 23 (5): 158–165. doi:10.1021/ar00173a007.
  4. Angew. Chem. Int. Ed. 42 (38): 4592–4633. doi:10.1002/anie.200300576.
  5. Trnka, T. M.; Acc. Chem. Res. 34 (1): 18–29. doi:10.1021/ar000114f.
  6. Tetrahedron 54 (18): 4413–4450. doi:10.1016/S0040-4020(97)10427-6.
  7. Tetrahedron 60 (34): 7117–7140. doi:10.1016/j.tet.2004.05.124.

See also

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Concepts in Bioinorganic chemistry
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Olefin_metathesis". A list of authors is available in Wikipedia.