v-Triazolo[4,5-d]pyrimidines (8-azapurines). Part XVI. Preparation of 6-amino-8-azapurines by heating 4-amino-1,2,3-triazole-5-carbonitrile (and its N-alkyl derivatives) with amidines

Abstract

4-Amino-1,2,3-triazole-5-carbonitrile, and its 1-, 2-, and 3-methyl, and 3-benzyl derivatives (1a–e), reacted with formamidine, acetamidine, 2,2,2-trichloroacetamidine, and NN′-dibutylformamidine to give the corresponding 6-amino-, 6-amino-2-methyl-, 6-amino-2-trichloromethyl-, and 6-butylamino-8-azapurines (2), respectively. Yields were usually very good and the reaction has preparative value. 6-Amino-9-benzyl-2-methyl-8-azapurine was prepared also by the action of triethyl orthoacetate on 4-amino-3-benzyl-1,2,3-triazole-5-carboxamidine (3). A 2-trichloromethyl-8-azapurine was conveniently dehalogenated to the 2-dichloromethyl analogue.

4-Amino-3-benzyl-1,2,3-triazole-5-carbonitrile (1e) was converted by free guanidine into 1-(4-amino-3-benzyl-1,2,3-triazol-5-ylcarbonimidoyl)guanidine (7b), which could be cyclized thermally to 2,6-diamino-9-benzyl-8-azapurine (2p). The mechanisms of the amidine and guanidine reactions are compared.

I.r. and ¹H n.m.r. spectra are recorded and discussed.