Facile construction of substituted pyrimido[4,5-d] pyrimidones by transformation of enaminouracil

The reaction of 6-amino-1,3-dimethylpyrimidine-2,4[1H,3H]-dione [1] as a binucleophile with primary aromatic or heterocyclic amines and formaldehyde or aromatic [heterocyclic] aldehydes in a molar ratio [1:1:2] gave the pyrimido[4,5-d]pyrimidin-2,4-dione ring systems 2-5. Treatment of 1 with diamines and formalin in molar ratio [2:1:4] gave the bis-pyrimido[4,5-d]pyrimidin- 2,4-diones 6-8. Furthermore, substituted pyrimido[4,5-d]pyrimidin-2,4-diones with uracil derivative 11 or spiro indole 16 were synthesized. Synthesis of pyrimido[4,5-d]pyrimidin-2,4-diones with different substitution at C-5 and C-7 was achieved to give 13 and 18, respectively

Synthesis, characterization and RHFlab initio simulations of 2-amino-1,3,4-thiadiazole and its annulated ring junction pyrimidine derivatives

Michael addition reaction of the 2-amino-1,3,4-thiadiazole to chalcone as biselectrophile - afforded 5,7-diphenyl-6-[1,3-diphenylpropan-1-on-3-yl][l,3,4]thiadiazolo[3,2-[a]pyrimidine [3] instead of 5,7-diphenyl-5H-[l,3,4]thiadiazolo[3,2-a]pyrimidine [5] via further Michael addition at C[5] in pyrimidine moiety. The structure 3 was established through the aspect of ab initio calculations, elemental analysis and spectral data