1,2,3,4,6-Penta-azaindenes (‘8-azapurines’). Part III. A new route to the 7-methyl-8-azapurines

Abstract

A new and convenient preparation of the hitherto difficulty accessible 7-methyl-8-azapurines begins with the condensation of cyanoacetamide with benzyl azide to 4-amino-3-benzyl-3H-1,2,3-triazole-5-carboxyamide (III) which is methylated to the previously unknown 4-amino-3-benzyl-5-carbamoyl-1-methyl-1,2,3-triazolium-toluene-p-sulphonate. This is hydrogenated to 4-amino-1-methyl-1H-1,2,3-triazole-5-carboxyamide (IV) which gives 6-hydroxy-7-methyl-8-azapurine when heated with formamide. Phosphoryl chloride converts this to the 6-chloro-compound from which the 6-amino-, methoxy-, mercapto-, methylthio-, and hydrazino-analogues are prepared. Oxidation of the last named gave 7-methyl-8-azapurine, the cation of which exists preferentially as the covalent hydrate (V). Many ionisation constants and spectra (u.v., i.r., and n.m.r.) are reported.