Heterocyclic studies. Part 42. Pyrimido[5,4-d][1,2,3]triazines and some related tricyclic compounds

Abstract

Nitrous acid treatment of 2,4-disubstituted 6-methyl-5-nitropyrimidines gave the corresponding pyrimido[5,4-d][1,2,3]triazine 3-oxides. The latter reacted with thionyl chloride to give 4-chloro derivatives which were then converted into other 4-substituted pyrimidotriazines, two of which were further converted into the novel heterocyclic systems, imidazo- and pyrimido-[1′,2′-c]pyrimido[4,5-e][1,2,3]triazine.

Measurements of ¹H n.m.r. spectra included variable temperature studies of some bis(dimethylamino) compounds. These showed that the extent to which a dimethylamino group is conjugated with the heterocyclic system, and the energy barrier to its rotation, vary substantially with its position in the pyrimidotriazine system.