v-Triazolo[4,5-d]pyrimidines (8-azapurines). Part XV. Degradation by acid of ring N-alkylated derivatives of 6-amino-(and 1,6-dihydro-6-imino-)8-azapurines to N-alkylated 4-amino-1,2,3-triazole-5-carboxamidines

Abstract

Degradation, in boiling dilute acid, is described for 6-amino-8-azapurines (3)(7-amino-v-triazolo[4,5-d]pyrimidines), alkylated on a ring-nitrogen atom and/or the exocyclic amino-group, to give the corresponding alkylated 4-amino-1,2,3-triazole-5-carboxamidines (4). Similar, but more rapid, degradation of the isomeric 1,6-dihydro-6-imino-1-methyl-8-azapurines (5) to the same class of product is reported. Yields are usually excellent. Preparations of new 8-azapurines are described. It is shown that earlier attempts to produce 1,2,3-triazole amidines had given the corresponding zwitterions.

The action of acid on 6-alkylamino-8-azapurines, e.g.(8), becomes more complex when the triazole ring carries no N-substituent. Some rearrangement occurs to give a 6-amino-9-alkyl-8-azapurine, e.g.(10), which is degraded to an amidine, isomeric with the required product. The rearrangement can be effected quantitatively by heating the solid.

Ionization constants and u.v., i.r., and ¹H n.m.r. spectra are recorded and discussed.