Oppenauer oxidation
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Oppenauer oxidation, named after Rupert Viktor Oppenauer [1], is a gentle method for oxidising secondary alcohols to ketones.
The reaction is the opposite of Meerwein-Ponndorf-Verley reduction. The alcohol is oxidised with Aluminium-tert.-butylate in excess acetone. This shifts the equilibrium toward the product side.
The method has been largely displaced by oxidation methods based on chromates (e.g. PCC) or dimethylsulfoxide (e.g. Swern oxidation) or Dess-Martin oxidation. It is still used for the oxidation of acid labile substrates. An advantage of the Oppenauer reaction is its use of relatively inexpensive and non-toxic reagents.
A variation that uses trichloroacetaldehyde and aluminium oxide is able to selectively oxidise secondary alcohols, leaving primary alcohols unchanged.
In one modification [2] the catalyst is trimethyl aluminum and the aldehyde 2-nitrobenzaldehyde for example in the oxidation of isoborneol to camphor:
[edit] References
- ^ Oppenauer, R. V. Recl. Trav. Chim. Pays-Bas 1937, 56, 137-144.
- ^ Efficient and Selective Al-Catalyzed Alcohol Oxidation via Oppenauer Chemistry Christopher R. Graves, Bi-Shun Zeng, and SonBinh T. Nguyen J. Am. Chem. Soc.; 2006; 128(39) pp 12596 - 12597; (Communication) DOI:10.1021/ja063842s
