Semmler-Wolff aromatization

What is Semmler-Wolff aromatization?

The first report of this reaction dates back to 1892 by Semmler. Later, in 1902, Wolff studied it, and in 1911, Schroeter also conducted a study on it. The reaction involves the rearrangement of an oxime of an α,β-unsaturated cyclohexenone, also known as the α,β-unsaturated cyclohexenyl ketoxime, into an aromatic amine.

Semmler-Wolff aromatization - general reaction scheme
Semmler-Wolff aromatization

Y = CH, N (see list of acronyms)
This reaction takes place in a mixture of acetic anhydride Ac2O and acetic acid AcOH, which is saturated with either HCl or HBr. It is commonly referred to as the Semmler-Wolff aromatization, Semmler-Wolff rearrangement, or Semmler-Wolff reaction. Sometimes it is also known as the Semmler-Wolff-Schroeter reaction.

However, it is important to note that the Beckmann rearrangement and the fragmentation to nitriles often compete with the Semmler-Wolff aromatization. Furthermore, substituents that are in close proximity to the reaction center can impede the Semmler-Wolff aromatization.

References

  • Semmler, W., Ber., 1892, 25, 3352
  • Wolff, L., Ann., 1902, 322, 351
  • Schroeter, G., Ber., 1911, 44, 1201
Shares