Aza-analogues of pteridine. Part VI. Some 3-alkyl-5(and 7)-amino-pyrimido[5,4-e]-as-triazines and related compounds

Abstract

4-[N′-(1-Ethoxypropylidene)hydrazino]-2-methoxy-5-nitropyrimidine (3; R = Et) was converted into 3-ethyl-5,7-dimethoxy[5,4-e]-as-triazine (1a), which underwent ammonolysis to 5-amino-3-ethyl-7-methoxypyrimido-triazine (1b) and its 5,7-diamino-analogue (1c). Hydrolysis of the same dimethoxypyrimidotriazine gave 3-ethyl-7-methoxypyrimidotriazin-5(6H)-one (2b), which on ammonolysis gave its 7-amino-analogue (2e). Homologous compounds were made similarly.

In boiling toluene, the pyrimidine intermediate (3; R = Et) isomerized to 3-ethoxy-3-ethyl-2,3-dihydro-5-methoxy-8-nitro-s-triazolo[4,3-c]pyrimidine (4; R = Et).

5-Amino-3-methylthio-as-triazine-6-carboxamide (6; R¹= SMe, R²= R³= NH₂) was converted by Vilsmeier reagents into 8-chloro-6-dimethylamino-5,6-dihydro-3-methylthiopyrimido[4,5-e]-as-triazine (7) or by triethyl orthoformate into 3-methylthiopyrimido[4,5-e]-as-triazin-8(7H)-one (5; R = SMe). Assigned structures were consistent with ionization constants and with the u.v., i.r., ¹H n.m.r., and mass spectra recorded.