Nierenstein reaction
Chemical reaction
From Wikipedia, the free encyclopedia
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 when diazomethyl anion displaces the chloride:
Excess diazomethane can act as a base, abstracting a hydrogen from the diazonium intermediate. The results are a neutral diazoketone, which does not react further; and methyldiazonium chloride, which decomposes to chloromethane. The unreactive diazoketone can, however, be re-activated with hydrogen chloride to give the Nierenstein product:
In even some cases with limited diazomethane, the reaction process can stall into the diazoketone pathway, requiring reparative HCl gas.[3] Substitution of a mixed anhydride for the acyl halide also gives the diazoketone.[4]
Examples
Nierenstein's original 1924 publication:[5]
A reaction from benzoyl bromide going haywire and forming the dioxane dimer:[6]
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