Practical synthesis of regioisomeric 5(7)-amino-6,7(4,5)-dihydro[1,2,4]triazolo[1,5-a][1,3,5]triazines

A convenient and efficient synthesis of new 5-azapurine derivatives was developed. The regioisomeric 5-amino-6,7-dihydro- and 7-amino-4,5-dihydro[1,2,4]triazolo[1,5-a][1,3,5]triazines were prepared in 3–4 steps from benzhydrazide via complementary and regiospecific routes as a part of our lead finding program. The molecular structures and tautomeric preferences of the compounds obtained were investigated using NMR spectral data and X-ray crystallography.