The Dimroth rearrangement is a rearrangement reaction taking place with certain 1,2,3-triazoles where endocyclic and exocyclic nitrogen atoms switch place.
[2][3][4] With R a phenyl group the reaction takes place in boiling pyridine for 24 hours.
After ring-opening to a diazo intermediate, C-C bond rotation is possible with 1,3-migration of a proton.
In the first step is an addition reaction of water followed by ring-opening of the hemiaminal to the aminoaldehyde followed by ring closure.
A known drug example of the Dimroth rearrangement includes in the synthesis of Bemitradine [88133-11-3].