Functionalization of 2-Amino-3-benzyl-6-(benzylthio)pyrimidin-4(3H)-one: An Efficient Access to the Synthesis of Polycyclic Pyrimidine Scaffolds

2-Aminouracil is used in the synthesis of a new series of tri- and tetracyclic pyrimidine scaffolds as the precursor. Thiazolo[5,4-d]triazolo[4,3-a]pyrimidine has been synthesized by diazotization and heterocyclization of the aminopyrimidinone derivative with nitrous acid at low temperature. Some new pyrimidines have been formed in the course of acylation and cyclization of the same compound with acetic anhydride, formic acid, pyruvic acid, or phthalic anhydride.