Oppenauer oxidation

Oppenauer oxidation
Named after Rupert Viktor Oppenauer
Reaction type Organic redox reaction
Identifiers
Organic Chemistry Portal oppenauer-oxidation
RSC ontology ID RXNO:0000047

Oppenauer oxidation, named after Rupert Viktor Oppenauer [de],[1] is a gentle method for selectively oxidizing secondary alcohols to ketones.

Oppenauer oxidation reaction scheme
Oppenauer oxidation reaction scheme

The reaction is the opposite Meerwein–Ponndorf–Verley reduction.[2] The alcohol is oxidized with aluminium isopropoxide in excess acetone. This shifts the equilibrium toward the product side.

The oxidation is highly selective for secondary alcohols and does not oxidize other sensitive functional groups such as amines and sulfides.[3] Though primary alcohols can be oxidized under Oppenauer conditions, primary alcohols are seldom oxidized by this method due to the competing aldol condensation of aldehyde products. The Oppenauer oxidation is still used for the oxidation of acid labile substrates. The method has been largely displaced by oxidation methods based on chromates (e.g. pyridinium chlorochromate) or dimethyl sulfoxide (e.g. Swern oxidation) or Dess–Martin oxidation due to its use of relatively mild and non-toxic reagents (e.g. the reaction is run in acetone/benzene mixtures). The Oppenauer oxidation is commonly used in various industrial processes such as the synthesis of steroids, hormones, alkaloids, terpenes, etc.

  1. ^ Oppenauer, R. V. (1937). "Eine Methode der Dehydrierung von Sekundären Alkoholen zu Ketonen. I. Zur Herstellung von Sterinketonen und Sexualhormonen" [Dehydration of secondary alcohols to ketones. I. Preparation of sterol ketones and sex hormones]. Recl. Trav. Chim. Pays-Bas (in German). 56 (2): 137–144. doi:10.1002/recl.19370560206.
  2. ^ Wilds, A. L. (1944). "Reduction with Aluminum Alkoxides (The Meerwein-Ponndorf-Verley Reduction)". Org. React. 2 (5): 178–223. doi:10.1002/0471264180.or002.05.
  3. ^ Otvos, L.; Gruber, L.; Meisel-Agoston, J. (1965). "The Meerwein-Ponndorf-Verley-Oppenauer. Investigation of the reaction mechanism with radiocarbon. Racemization of secondary alcohols". Acta Chim. Acad. Sci. Hung. 43: 149–153.