Heteroatomic translocation, Dimroth

El Ashry, E. S. H., El Kilany, Y., Assafir, H., Rashed, N., Dimroth Rearrangement Translocation of Heteroatoms in Heterocyclic Rings and Its Role in Ring Transformations of Heterocycles, 75, 79. 

Dimroth rearrangement Isomerization of heterocycles in which endocyclic or oxocyclic heteroatoms and their attached substituents are translocated via a ring-opening-ring-closure sequence. 144... 

Dimroth Rearrangement Translocation of Heteroatoms in Heterocyclic Rings and Its Role in Ring Transformations of Heterocycles... 

The general Dimroth arrangement refers to the translocation of heteroatoms either within the rings of fused heterocyclic systems or between a ring heteroatom and a substituent. The present chapter presents the first modern general review of the Dimroth rearrangement and is authored by Professor E. S. H. El Ashry and Drs. Y. El Kilany, N. Rashed, and H. Assafir, all of Alexandria University, Egypt. 

Translocation of heteroatoms in rings and its role in Dimroth rearrangement of heterocycles 00AHC(75)79. 

The Dimroth rearrangement is an isomerization process whereby atoms on a heterocyclic ring are translocated. The reaction can be catalyzed by a variety of acids and bases, with or without the presence of heat or light. Several factors may influence the rearrangement, including the number and types of heteroatoms in the ring, the number and types of substituents on the ring, and the kinetic and thermodynamic stabilities of the reactants and translocation products. 

The most common rearrangements involve the translocation of exo-and endocyclic heteroatoms on a single heterocyclic ring. However, the Dimroth rearrangement has been shown to occur on a limited basis with heteroatoms in fused heterocyclic ring systems such as imidazo-, pyrazolo-, 1,2,3-triazolo- and 1,2,4-triazolo- and pyrimido-heterocycles. 

The translocation of exocyclic and endocyclic heteroatoms on a single heterocycle is shown below in D. In this case, the rearrangement is generally promoted by an exocyclic heteroatom on the ring. This is the most common example of a Dimroth rearrangement. 

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