My watch list
my.chemeurope.com  
Login  

McMurry reaction



 The McMurry reaction is an organic reaction in which two ketone or aldehyde groups are coupled to an alkene in the presence of a titanium chloride compound such as titanium(III) chloride and a reducing agent [1].

Additional recommended knowledge

The McMurry reaction is named after its discoverer, John E. McMurry, who is currently professor emeritus at Cornell University.

Reaction mechanism

In 1974, McMurry and Fleming described a ‘new method for the reductive coupling of carbonyls to olefins’ with TiCl3 and LiAlH4. This reductive coupling involves two steps. The first step is the formation of a pinacolate (1,2-diolate) (see pinacol coupling reaction ), the second the deoxygenation of the pinacolate to yield the alkene.

McMurry himself proposed, after his discovery of the TiCl3–LiAlH4 system (1974), several ‘improved procedures’ by using the TiCl3–K, TiCl3–Li (1976) and then TiCl3–Zn(Cu) reagents (1978)and finally recommended an ‘optimized procedure’ with the TiCl3(DME)1.5–Zn(Cu) combination, which gave reproducibly high yields in many cases (1989).

Several mechanisms have been discussed for this reaction [2]. Low-valent titanium species are formed before or during the reaction and induce the reaction by single electron transfer to the carbonyl group - which low-valent titanium species is formed depends on the used reagent[3]. In fact, it was found that TiCl3 could be reduced by Zn only if its redox potential has been lowered by coordination to the carbonyl substrate. A decisive contribution to the mechanistic investigations was made by Bogdanovic and Bolte, who identified the nature and mode of action of the active species in some classical McMurry systems[4].

Scope

The original publication concerned the coupling of retinal to carotene with a titanium(III) trichloride / Lithium aluminium hydride system. In a similar fashion tetraphenylethylene is synthesized from benzophenone. Other dimers formed in the original publication are those of adamantanone and civetone. A McMurry reaction with titanium tetrachloride and zinc is employed in the synthesis of a molecular motor [5].

References

  1. ^ John E. McMurry, Michael P. Fleming (1974). "New method for the reductive coupling of carbonyls to olefins. Synthesis of β-carotene". J. Am. Chem. Soc. 96 (14): 4708-4709. doi:10.1021/ja00821a076.
  2. ^ Michel Ephritikhine (1998). "A new look at the McMurry reaction". Chem. Commun.: 2549–2554.
  3. ^ Borislav Alois Furstner, Borislav Bogdanovic (1996). "New developments in the chemistry of low-valent titanium". Angew. Chem. Int. Ed. (35): 2442.
  4. ^ Borislav Bogdanovic, Andreas Bolte (1995). "A comparative study of the McMurry reaction utilizing [HTiCl(THF)0.5)]x, TiCl3(DME)1.5-Zn(Cu) and TiCl2*LiCl as coupling reagents". J. Organomet. Chem. 502: 109-121.
  5. ^ Matthijs K. J. ter Wiel, Richard A. van Delden, Auke Meetsma, and Ben L. Feringa (2005). "Light-Driven Molecular Motors: Stepwise Thermal Helix Inversion during Unidirectional Rotation of Sterically Overcrowded Biphenanthrylidenes". J. Am. Chem. Soc. 127 (41): 14208. doi:10.1021/ja052201e.
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "McMurry_reaction". A list of authors is available in Wikipedia.
Your browser is not current. Microsoft Internet Explorer 6.0 does not support some functions on Chemie.DE