The Dimroth rearrangement is a rearrangement reaction taking place with certain 1,2,3-triazoles where endocyclic and exocyclic nitrogen atoms switch place.Heterocyclic chemistry T.L. Gilchrist This organic reaction was discovered in 1909 by Otto Dimroth.Ueber intramolekulare Umlagerungen. Umlagerungen in der Reihe des 1, 2, 3-Triazols Justus Liebig's Annalen der Chemie Volume 364, Issue 2, Date: 1909, Pages: 183-226 Otto Dimroth Intramolekulare Umlagerung der 5-Amino-1,2,3-triazole Justus Liebig's Annalen der Chemie Volume 459, Issue 1, Date: 1927, Pages: 39-46 Otto Dimroth, Walter Michaelis Mittheilungen Ueber eine Synthese von Derivaten des 1.2.3-Triazols Otto Dimroth Berichte der deutschen chemischen Gesellschaft 1902 Volume 35, Issue 1 , Pages 1029 - 1038
With R a phenyl group the reaction takes place in boiling pyridine for 24 hours.Organic Syntheses, Coll. Vol. 4, p.380 (1963); Vol. 37, p.26 (1957). http://orgsynth.org/orgsyn/pdfs/CV4P0380.pdf
This type of triazole has an amino group in the 5 position. After ring-opening to a diazo intermediate, C-C bond rotation is possible with 1,3-migration of a proton.
Certain 1-alkyl-2-iminopyrimidines also display this type of rearrangement.
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]. References