The Nierenstein reaction is an organic reaction describing the conversion of an acid chloride into a haloketone with diazomethane.[1][2] It is an insertion reaction in that the methylene group from the diazomethane is inserted into the carbon-chlorine bond of the acid chloride.
| Nierenstein reaction | |
|---|---|
| Named after | Maximilian Nierenstein |
| Reaction type | Carbon-carbon bond forming reaction |
Reaction mechanism
The reaction proceeds through a diazonium salt intermediate formed by displacement of the chloride with diazomethyl anion.
If excess diazomethane is present during the reaction, it can act as a base, abstracting a hydrogen from the diazonium-salt intermediate. The result is a neutral diazoketone, which does not react with the chloride. Instead, the byproduct, diazonium-methyl from the other diazomethane molecule, can be attacked by the chloride to produce chloromethane. The unreactive diazoketone can be re-activated and reacted by treatment with hydrogen chloride to give the normal Nierenstein product.
In some cases, even limiting the amount of diazomethane gives a reaction process that stalls via the neutral diazoketone pathway, requiring the addition of HCl gas to rescue it.[3]
Scope
One original 1924 Nierenstein reaction:[4]
and a reaction starting from benzoyl bromide going haywire with formation of the dioxane dimer:[5]
See also
- Maximilian Nierenstein
- Curtius rearrangement
- Wolff rearrangement
- Arndt–Eistert reaction: where acid chlorides react with diazomethane to give chain extended carboxylic acids via a rearrangement
References
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