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

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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.

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