Aza-analogues of pteridine. Part V. 5-Alkylaminopyrimido[5,4-e]-as-triazines from 5-alkyl or 5-unsubstituted analogues via 5,6-adducts with amines

Abstract

5-Alkylamino- and 5-dimethylamino-pyrimido[5,4-e]-as-triazines were formed by aerating the corresponding 5-unsubstituted or 5-alkyl-pyrimidotriazines, or their 1,2-dihydro-derivatives, in tetrahydrofuran containing an appropriate amine. The mechanism involved 5,6-addition of the amine and one or two oxidative steps, depending on the substrate. The method was used to make 5-propylaminopyrimidotriazine (1k) and its 3-methyl and 3,7-dimethyi derivatives: 5-dimethylaminopyrimidotriazine (11) and its 3-methyl, 7-methyl. 3,7-dimethyl, and 7-methoxy-3-methyl derivatives; and 3-methyl-5-methylaminopyrimidotriazine(1r). Of these, the second, fifth, eighth, and ninth were made unambiguously by aminolyses of the corresponding methoxypyrimidotriazines; other structures were confirmed by u.v. and ¹H n.m.r. spectra. 1,2-Dihydro-3-methyl-5-propylpyrimidotriazine (2b) was made by cyclization of 4-(2-acetylhydrazino)-2-chloro-5-nitro-6-propylpyrimidine (3; R¹= NH·NHAc, R²= Pr), prepared from its 2,4-dichloroanalogue and acetylhydrazine; other 1,2-dihydrosubstrates were made similarly or by established routes.