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The Wolff–Kishner reduction is a reaction used in organic chemistry to convert carbonyl functionalities into methylene groups. [1] [2] In the context of complex molecule synthesis, it is most frequently employed to remove a carbonyl group after it has served its synthetic purpose of activating an intermediate in a preceding step.
The 4-acetyl group could easily be converted to a 4-ethyl group by Wolff-Kishner reduction (hydrazine and alkali, heated); hydrogenolysis, or the use of diborane. Benzyl or tert-butyl acetoacetates also work well in this system, and with close temperature control, the tert-butyl system gives a very high yield (close to 80%). [10]
The vinylogous Wolff rearrangement consists of a β,γ-unsaturated diazo ketone undergoing a Wolff rearrangement, and a formal 1,3-shift of the CH 2 CO 2 R group. The vinylogous Wolff rearrangement yields a γ,δ-unsaturated carboxylic acid derivative, which is the same retron as for the Claisen rearrangement. The variant was discovered when it ...
The acylated reaction product can be converted into the alkylated product via a Clemmensen or a Wolff-Kishner reduction. [17] The Gattermann–Koch reaction can be used to synthesize benzaldehyde from benzene. [18] The Gatterman reaction describes arene reactions with hydrocyanic acid. [19] [20]
Wolff–Kishner reduction: Alkane: If an aldehyde is converted to a simple hydrazone (RCH=NHNH 2) and this is heated with a base such as KOH, the terminal carbon is fully reduced to a methyl group. The Wolff–Kishner reaction may be performed as a one-pot reaction, giving the overall conversion RCH=O → RCH 3. Pinacol coupling reaction: Diol
In organic chemistry, the Arndt–Eistert reaction is the conversion of a carboxylic acid to its homologue.It is named for the German chemists Fritz Arndt (1885–1969) and Bernd Eistert (1902–1978).
For the same reason, E1cb reactions involving hydroxide as a leaving group are not uncommon (e.g., in the aldol condensation). It is exceedingly rare for groups such as H − ( hydrides ), R 3 C − ( alkyl anions , R = alkyl or H), or Ar − (aryl anions, Ar = aryl) to depart with a pair of electrons because of the high energy of these species.
The Seyferth–Gilbert homologation is a chemical reaction of an aryl ketone 1 (or aldehyde) with dimethyl (diazomethyl)phosphonate 2 and potassium tert-butoxide to give substituted alkynes 3.