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Acyloin condensation



Acyloin condensation is a reductive coupling of two carboxylic esters using metallic sodium to yield an α-hydroxyketone, also known as an acyloin.[1][2]

The reaction is most successful when R is aliphatic and inert. To achieve the condensation, chemists should employ aprotic solvents with a high boiling point, such as benzene and toluene. (Usage of protic solvents results in the Bouveault-Blanc reduction.) Depending on ring size and steric properties, but independent from high dilution, the acyloin condensation of diesters favours intramolecular cyclisation over intermolecular polymerisation.

Additional recommended knowledge

Contents

Variations

Rühlmann-method

The method according to Rühlmann[3] employs trimethylchlorosilane as a trapping reagent; by this, competing reactions are efficiently subdued. Generally, yields increase considerably. The hydrolytic cleavage of the silylether gives the acyloin. To achieve a mild cleavage methanol can be used in several cases.

Usually toluene, dioxane, tetrahydrofuran or acyclic dialkylethers are employed as solvents. Advantageously also N-methyl-morpholine has been used. It allowed in some cases a successful reaction, in which otherwise the reaction failed in less polar media.

References

  1. ^  Bouveault, L., and R. Loquin. Comptes. Rendus. 1905, 140, 1593.
  2. ^  Finley, K. T. Chem. Rev. 1964, 64, 573. (Review)
  3. ^  Rühlmann K., Synthesis, 1971, 236–253. (Review)

See also

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