Wohl-Aue reaction

What is Wohl-Aue reaction?

The Wohl-Aue reaction, a method for synthesizing phenazine and phenazine N-oxide, was first reported by Wohl and Aue in 1901. This reaction involves the condensation of an aromatic nitro compound with an aniline in the presence of a strong base and is commonly referred to as the Wohl-Aue reaction, Wohl-Aue phenazine synthesis, or Wohl-Aue condensation. Although typically performed at high temperatures, it has also been reported to occur at room temperature.

Wohl-Aue reaction - general reaction scheme - Wohl-Aue phenazine synthesis - Wohl-Aue condensation
Wohl-Aue reaction
Wohl-Aue reaction - general reaction scheme - Wohl-Aue phenazine synthesis - Wohl-Aue condensation
Wohl-Aue reaction

The phenazine N-oxide is derived from the nitro group of the nitro compound, and its formation is supported by the depression of the melting point of the admixture of phenazine N-oxide from the Wohl-Aue reaction. Phenazine N-oxides can be further reduced by hot aniline to produce phenazines. Although this reaction often produces low yields of phenazines and corresponding N-oxides and may result in other side products, using a solvent during the condensation step typically leads to better yields than solvent-free conditions. In particular, substituting toluene for benzene as the solvent can increase the yield. Unhindered phenazines can be directly oxidized to phenazine dioxide, while hindered ones, such as benzo[a]phenazine, can only be converted into mono-oxides.

References

Wohl, A. and Aue, A., Ber., 1901, 34, 2442

Shares