The<unk>  is a<unk>  reaction taking place with certain 1,2,3-triazoles where endocyclic and exocyclic nitrogen atoms switch place . This organic reaction was discovered in 1909 by Otto<unk>    .
With R a phenyl group the reaction takes place in boiling pyridine for 24 hours 
This type of triazole has a amino group in the 5 position. After ring-opening to a diazo intermediate, C-N bond rotation is possible with 1,3-migration of a proton.
Certain 1-alkyl-2-iminopyrimidines also display this type of<unk> .
In the first step is an addition reaction of water followed by ring-opening of the hemiaminal to the aminoaldehyde followed by ring closure.
Dimroth rearrangement
Mitotic crossover
Cre-Lox recombination
Arndt-Eistert synthesis
Somatic hypermutation
Self-replication
Allosteric regulation
Thermal depolymerization