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 hydrazone with sodium ethoxide in a sealed vessel at about 200 °C. Other bases have been found equally effective.

Several reviews have been published.^[3][4]

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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.

Huang-Minlon modification

The Huang-Minlon modification^[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]

References

1. ^  Kishner, N. J. Russ. Chem. Soc. 1911, 43, 582.
2. ^  Wolff, L. Ann. 1912, 394, 86.
3. ^  Todd, D. Org. React. 1948, 4, 378. (Review)
4. ^  Hutchins, R. O.; Hutchins, M. K. Comp. Org. Syn. 1991, 8, 327-343. (Review)
5. ^  Huang-Minlon J. Am. Chem. Soc. 1946, 68, 2487.
6. ^  Huang-Minlon J. Am. Chem. Soc. 1949, 71, 3301.
7. ^  Organic Syntheses, Coll. Vol. 4, p.510 (1963); Vol. 38, p.34 (1958). (Article)
8. Organic Syntheses, Coll. Vol. 5, p.533 (1973); Vol. 43, p.34 (1963). (Article)

See also

• Clemmensen reduction
• Haworth phenanthrene synthesis
• Raney nickel
• Wharton reaction