Hofmann-Martius rearrangement

What is Hofmann-Martius rearrangement?

The Hofmann-Martius rearrangement, or aniline rearrangement, which involves the thermal conversion of hydrohalides of N-alkylated aromatic amines to produce o-alkylated and p-alkylated aromatic amine derivatives, was initially documented by Hofmann and Martius in 1871.

Hofmann-Martius rearrangement

When N-alkylated aromatic amine hydrochlorides are heated, they dissociate, and the resulting components undergo intermolecular alkylation through the migration of an alkyl group in the form of a free radical, olefin, or carbocation. Evidence suggests that both radical and olefin pathways may be involved. In the solid state, the Hofmann-Martius rearrangement primarily produces ortho-alkylated products, likely due to restricted diffusion. Additionally, the rearrangement can be initiated by photo-irradiation.