Aza analogues of pteridine. VII. 3-Alhoxypyrimido[5,4-e]-as-triazines and some derivatives

Abstract

Syntheses and some reactions of 3-ethoxypyrimido[5,4-e]-as-triazines are described. For example, 4-hydrazino-6-methoxy-5-nitropyrimidine (3a) and ethyl orthocarbonate give the 4-(diethoxymethylene)hydrazino derivative (4a) which may be reduced to its 5-amino analogue (4b) and thence cyclized to the 3-ethoxy-1,2-dihydro-5-methoxypyrimidotriazine. This undergoes dehydrogenation by mercuric oxide to the 3-ethoxy-5- methoxypyrimidotriazine (1a). Such dialkoxypyrimidotriazines are aminolysed to 5-mono- or 3,5-di-amines, e.g. (1g) or (1e), according to conditions; similarly trialkoxypyrimidotriazines, e.g. (1p), undergo successive aminolysis at the 5-, 3-, and 7-position. In contrast, the 3-group proves to be least reactive during progressive acidic hydrolysis of trialkoxypyrimidotriazines to the trione (8). The tabu- lated ultraviolet and p.m.r. spectra serve to prove or confirm many of the structures.