View source for Wolff–Kishner reduction

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The '''Wolff–Kishner''' reduction is a reaction used in organic chemistry to reduce carbonyl groups into methylene groups. 

==Description==
The reaction mechanism first involves the in situ generation of a hydrazone by condensation of [[hydrazine]] with the [[ketone]] or [[aldehyde]] substrate. The hydrazone is deprotonated by alkoxide base followed by a concerted, rate-determining step in which a diimide anion is formed. Collapse of this alkyldiimide with loss of [[nitrogen]] leads to formation of an alkylanion which can be protonated by solvent to give the desired product.<ref>https://en.wikipedia.org/wiki/Wolff%E2%80%93Kishner_reduction</ref>

The Wolff-Kishner reduction doesn't work on esters or ethers.

==Procedure==
As this reaction involves the use of hydrazine hydrate, work must be performed under a fumehood, as pure hydrazine is very toxic.

==Modifications==
===Huang Minlon modification===
The modified procedure consists of refluxing the carbonyl compound in 85% hydrazine hydrate with three equivalents of [[sodium hydroxide]] followed by distillation of water and excess hydrazine and elevation of the temperature to 200 °C. Significantly reduced reaction times and improved yields can be obtained using this modification.

===Barton modification===
This method features vigorous exclusion of water, higher temperatures, and longer reaction times as well as [[sodium]] in [[diethylene glycol]] instead of alkoxide base.

===Cram modification===
Slow addition of preformed hydrazones to [[potassium tert-butoxide]] in [[Dimethyl sulfoxide|DMSO]] as reaction medium instead of glycols allows hydrocarbon formation to be conducted successfully at temperatures as low as 23 °C.

===Henbest modification===
Henbest extended Cram’s procedure by refluxing carbonyl hydrazones and potassium tert-butoxide in dry [[toluene]]. Slow addition of the hydrazone is not necessary and it was found that this procedure is better suited for carbonyl compounds prone to base-induced side reactions than Cram's modification.

===Caglioti reaction===
Involves treatment of tosylhydrazones with hydride donors, like sodium cyanoborohydride, sodium triacetoxyborohydride, or catecholborane to obtain the corresponding alkanes.

==Uses==
*Reduce ketones and aldehydes

==References==
<references/>
===Relevant Scencemadness threads===
*[http://www.sciencemadness.org/talk/viewthread.php?tid=68467 ethylbenzene by Wolff-Kishner (Huang-Minlon)]
*[http://www.sciencemadness.org/talk/viewthread.php?tid=12419 alpha-keto acids and hydrazone formation/wolff-kishner stuffs]

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