1,2,3,4,6-Penta-azaindenes (8-azapurines). Part IV. A new route to the 8-methyl-8-azapurines through the 2-methyl-1,2,3-triazoles

Abstract

4-Amino-1,2,3-triazole-5-carboxyamide was formylated to an anhydro-dimer (IV) of 4-formamido-1,2,3-triazole-5-carboxyamide. Methylation of the latter took place almost exclusively in the 2-position to give 4-formamido-2-methyl-1,2,3-triazole-5-carboxyamide (IIa)(some minor products of this methylation are also described). This formyl amide (IIa) was deformylated to the corresponding amine (IIb), and both substances were cyclised (by boiling formamide) to 6-hydroxy-8-methyl-8-azapurine (Ib). The latter was converted by the usual metathetical reactions into the 6-chloro-, 6-mercapto-, 6-methylthio-, 6-amino-, 6-methoxy-, and 6-hydrazino-derivatives of 8-methyl-8-azapurine. The last-named (VI; R NH·NH₂), when heated with silver oxide in propan-2-ol, gave the parent: 8-methyl-8-azapurine, the cation of which was shown to be covalently hydrated across the 1- and 6-positions. Many ionization constants and spectra of these triazoles and azapurines are reported for the first time.