Wolff–Kishner reduction
The Wolff–Kishner reduction is a chemical reaction that fully reduces a ketone (or aldehyde) to an alkane.[1][2]
The method originally involved heating the hydrazine with sodium ethoxide in a sealed vessel at about 180 °C. Other bases have been found equally effective. Diethylene glycol (DEG) is usually used as solvent.
Several reviews have been published.[3][4]
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[edit] Reaction mechanism
The most probable mechanism involves the elimination of an alkyl anion as the final step:
The mechanism first involves the formation of the hydrazone in a mechanism that is probably analogous to the formation of an imine. Successive deprotonations eventually result in the evolution of nitrogen. The mechanism can be justified by the evolution of nitrogen as the thermodynamic driving force. This reaction is also used to distinguish between aldehydes and ketones.
[edit] Huang-Minglon modification
The Huang-Minglon modification (after Huang Minglon) [5][6] is a convenient modification of the Wolff–Kishner reduction and involves heating the carbonyl compound, potassium hydroxide, and hydrazine hydrate together in ethylene glycol in a one-pot reaction.[7]
[edit] References
- ^ Nicolai Kishner J. Russ. Chem. Soc. 1911, 43, 582.
- ^ Ludwig Wolff (1912). "Chemischen Institut der Universität Jena: Methode zum Ersatz des Sauerstoffatoms der Ketone und Aldehyde durch Wasserstoff". Justus Liebigs Annalen der Chemie 394 (1): 86–108. doi:10.1002/jlac.19123940107.
- ^ Todd, D. Org. React. 1948, 4, 378. (Review)
- ^ Hutchins, R. O.; Hutchins, M. K. Comp. Org. Syn. 1991, 8, 327-343. (Review)
- ^ Huang-Minlon J. Am. Chem. Soc. 1946, 68, 2487.
- ^ Huang-Minlon J. Am. Chem. Soc. 1949, 71, 3301.
- ^ Organic Syntheses, Coll. Vol. 4, p. 510 (1963); Vol. 38, p. 34 (1958). (Article)
- Organic Syntheses, Coll. Vol. 5, p. 533 (1973); Vol. 43, p. 34 (1963). (Article)
