Sommelet-Hauser Rearrangement

Here is Sommelet-Hauser rearrangement definition with mechanism and example without doubt.

what is Sommelet-Hauser rearrangement explain?

Sommelet-Hauser rearrangement is one of the thermal [2,3]-sigmatropic rearrangements,  in which the benzylic quaternary ammonium salts are treated within the presence of a strong base like  NaNH2, KNH2, as well as alkyl lithium to prepare the Substituted 3° benzylic amine.

Sommelet-Hauser rearrangement takes place in the presence of a strong base as well as aprotic solvents. The rearrangement can be done on substituted aromatic ring like benzene as well as a substituted heteroaromatic ring.

To point out the two competing reactions that can occur on the substrate under Sommelet-Hauser rearrangement reaction condition are as follow

  1. Hofmann elimination: when hydrogen atoms are present on  alkyl groups attached to the nitrogen, elimination reaction can take under place those circumstances
  2. Stevens rearrangement:  if there are cyclic quaternary ammonium salts that can give ring-expansion reaction.
Sommelet-Hauser rearrangement
Sommelet-Hauser rearrangement of quaternary ammonium salt

Sommelet Hauser Rearrangement Mechanism:

  In the mechanism Sommelet-Hauser rearrangement first step is the formation of nitrogen yield intermediate, which is generated from benzylic quaternary ammonium salts by removing acidic proton using a strong base. The next step is the sigmatropic rearrangement, and then benzylic amines will form as I have shown below image.

Sommelet Hauser Rearrangement Mechanism or Mechanism of Sommelet-Hauser Rearrangement
Sommelet Hauser Rearrangement Mechanism or Mechanism of Sommelet-Hauser Rearrangement

Applications of Sommelet-Hauser Rearrangement:

  1. Total synthesis of the potent antibiotic natural product streptonigrin.
  2. Synthesis of 4,7-disubstituted indoles from aryl sulfilimines.
  3. Potential herbicides 5-Tetrahydrophtalimide-substituted indolin-2(3H)-ones synthesis.

Related Reaction:

  • Hofmann elimination
  • Stevens rearrangement
  • Claisen rearrangement
  • Cope rearrangement
  • Wittig rearrangement
  • Oxy-Cope rearrangement
  • aza-Wittig rearrangement

References :


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