v-Triazolo[4,5-d]pyrimidines (8-azapurines). Part VIII. Synthesis, from 1,2,3-triazoles, of 1- and 2-methyl derivatives of 5,7-disubstituted v-triazolo[4,5-d]pyrimidines (7- and 8-methyl 2,6-disubstituted 8-azapurines)

Abstract

4-Amino-1-methyl-1H-1,2,3-triazole-5-carboxamide (1), fused with thiourea, gave 5-mercapto-1-methyl-1H-v-triazolo[4,5-d]pyrimidin-7(6H)-one (2-mercapto-7-methyl-8-azapurin-6-one)(2a), which was methylated and oxidised to give the 5-methylsulphonyl derivative. This, when heated with sodium methoxide or ammonia, gave the 5-methoxy- and 5-amino-derivatives, respectively. 4-Amino-2-methyl-2H-1,2,3-triazole-5-carboxamide similarly gave various 5-substituted 2-methyl-2H-v-triazolo[4,5-d]pyrimidin-7(6H)-ones. 4-Amino-2-methyl-N-bis(methylamino)methylene-2H-1,2,3-triazole-5-carboxamide (5) was obtained as a by-product when the 2-methyl-5-methylsulphonyl derivative was heated with methylamine.

Alkaline hydrolysis of the two methylsulphonyl compounds gave the corresponding 5,7-diones, identical with products obtained by fusing the two triazoles with urea. A by-product of the first hydrolysis was 1-methyl-4-ureido-1H-1,2,3-triazole-5-carboxylic acid (3), which was further degraded to the 4-amino-derivative.

The two 5-mercapto-compounds were converted into the corresponding 5,7-bis(methylthio)-derivatives, which gave 7-amino-5-methylthio-compounds on heating with ethanolic ammonia. 5,7-Diamino-derivatives were made by heating the derived sulphones with ethanolic ammonia; in contrast, treatment with sodium methoxide and aqueous alkali gave 7-amino-5-methoxy- and 7-amino-5-oxo-derivatives, respectively. 5,7-Dichloro-2-methyl-2H-v-triazolo[4,5-d]pyrimidine (2,6-dichloro-8-methyl-8-azapurine)(made from the appropriate 5,7-dione) gave the 5,7-diamine with ethanolic ammonia.

The ionisation constants and the u.v., i.r, and n.m.r. spectra of these compounds are recorded and discussed.