v-Triazolo[4,5-d]pyrimidines (8-azapurines). Part 21. Synthesis of 2-substituted 8-azapurin-6-ones from 4-amino-1,2,3-triazole-5-carboxamides and amidines

Abstract

4-Amino-1,2,3-triazole-5-carboxamides (3)(several of them alkylated on a ring-nitrogen atom) were condensed with the acetates of acetamidine, trichloroacetamidine, and benzamidine to give the correspondingly 2-substituted 8-azapurin-6-ones (1). Thus, 4-amino-1-methyl-1,2,3-triazole-5-carboxamide (3b) and acetamidine furnished 2,7-dimethyl-8-azapurin-6-one in excellent yield. The reactions involving trichloroacetamidine halted at an intermediate [e.g. at 4-(α-amino-βββ-trichloroethylideneamino)-1,2,3-triazole-5-carboxamide (2d)] which was isolated and cyclized in aqueous alkali. Physical properties (u.v., i.r., m/e, pK_a, n.m.r.) of typical products were measured and discussed.