Temperature‐dependent reaction of 1,4,6‐triaminopyrimidine‐2(1 H )‐thiones with vilsmeier reagent. formation of [1,2,4]triazolo[1,5‐ c ]pyrimidin‐5(6 H )‐ones

5,7‐Diamino[1,3,4]thiadiazolo[3,2‐ a ]pyrirnidinium chloride 2 , 7‐amino[1,2,4]triazolo[1,5‐ c ]pyrimidine‐5(6 H )‐thiones 3 and the 5(6 H )‐one derivative 4a were synthesized by the reaction of 1,4,6‐triaminopyrimidine‐2(1 H )‐thione 1 with phosphoryl chloride and N,N ‐dimethylacylamides. Further, compounds 4 were prepared from 2, 3 or 1,4,6‐triaminopyrimidin‐2(1 H )‐one 6 by the treatment with the above reagents. Compounds 3 and 4 were converted to 7‐amino[1,2,4]triazolo[1,5‐ c ]pyrimidin‐5(6 H )‐ones 5 .