The chemistry of polyazaheterocyclic compounds. Part IV. Dimroth rearrangements of 4-substituted 5-amino-1-phenyl-1,2,3-triazoles and a synthesis of v-triazolo[4,5-d]pyrimidines

Abstract

Heating of 4-substituted 5-amino-1-phenyl-1,2,3-triazoles in acetic anhydride affords acetyl derivatives of the isomeric 4-substituted 5-anilino-1,2,3-triazoles. On the other hand the anilino-isomers and their acetyl derivatives retrogress to acetyl derivatives of the amino-compounds on prolonged refluxing in acetic anhydride. The course of these rearrangements is discussed. Acylation of 5-amino- or 5-anilino-1,2,3-triazoles at room temperature in the presence of concentrated sulphuric acid yields unrearranged products. Acyl derivatives of 5-amino-1-phenyl-1,2,3-triazole-4-carboxamide are smoothly converted into v-triazolo[4,5-d]pyrimidine derivatives when they are heated in aqueous alkali. The structure of a dimeric product obtained from the base-catalysed condensation of phenyl azide with malononitrile is discussed.