Reactions

The reaction is performed under acidic conditions and starts with the formation of an imine (Need a refresher? Check the Imine formation sheet). The hydrazone then undergoes tautomerization to give an enamine intermediate. Protonation of this enamine triggers an irreversible [3,3]-sigmatropic rearrangement, which breaks the N-N bond. A new primary amine is obtained after a tautomerization step and attacks the iminium function, leading to intramolecular cyclization. After a prototropy, the elimination of ammonium generates the indole.