Recent Advances in the Dimroth Rearrangement

Synthesis of [1,2,4]Triazolo[4″,3″:1′,6′]Pyrimido[4′,5′:3,4]Pyridazino[1,6-D] [1,2,4]Triazine; A Novel Tetracyclic System

“…Similar results relating to this rearrangement are in agreement with the reported results for analogueous compounds. [25][26][27] In our attempts to prepare various derivatives of the novel [1,2,4]triazolo[4′′,3′′:1′,6′]pyrimido[4′,5′:3,4]pyridazino[1,6-d] [1,2,4]triazine heterocyclic ring system, we encountered that compounds 4f and 4g did not react in an analogueous manner to compounds 4a-e. In the IR spectra of compounds 5f and 5g in contrast to compounds 5a-e, the stretching vibration band of CN group was still present and, on the basis of the other spectral and microanalytical analyses, it seems that the cyclisation has not occurred as with the similar analogues 5a-e. We are now exploring the effect of substituents on the aryl moiety on the nature of the two groups of products and these studies will be reported later.…”

Efficient New Synthesis of N‐Arylbenzo[b]furo[3,2‐d]pyrimidin‐4‐amines and Their Benzo[b]thieno[3,2‐d]pyrimidin‐4‐amine Analogues via a Microwave‐Assisted Dimroth Rearrangement

“…This “ancestral” transformation consists of a translocation of exocyclic and endocyclic heteroatoms present in both five‐ and six‐membered heterocycles . As shown in Scheme , the reaction generally leads to one of the two possible isomers, and the thermodynamic stability of the final compound is the driving force for its formation.…”

“…When an excess of aniline was used in the reaction mixture, the condensation of a part of the starting aromatic amine with acetic acid was observed and gave the corresponding acetamide derivatives as by‐products [5g]. As described in various applications of this rearrangement, reaction time and yields depend on the nucleophilicity of the aniline and also on steric hindrance of the substituents . The presence of large atoms or groups on the ortho ‐position of the aromatic amine (e.g., 4‐bromo‐2‐fluoroaniline in Table ) involved an increase of reaction time and slight decrease of the yields.…”

“…Taking into account all of these facts, we decided to explore the possibility of obtaining a rapid and efficient method for varying the aromatic amines that can be added to these tricyclic homologues of the basic 4‐anilinopyrimidine pharmacophore. We decided to adapt the possibilities offered by the Dimroth rearrangement . A survey of literature revealed that the synthesis of two examples of benzofuro[3,2‐ d ]pyrimidines 1 was only described 30 years ago via this thermally sensitive method .…”

One-pot regioselective synthesis of new 5-(arylsulfonylamino)imidazo[2,1-b]thiazoles

“…At the same time, the reaction path, presented in the scheme 8, is not proved to the full extent. Although Dimroth type isomerization is described for a range of heterocyclic compounds, 38 similar transformations are not typical for 1,3-thiazole fragments. Therefore, further investigation of a possible reaction path is needed.…”