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Dihydropyrimidine derivatives possess great potential to be used as a precursor for the synthesis of wide diverse dihydropyrimidine-like derivatives. In this research, the title compounds were synthesized through the reaction between 5-acetyl-4-(2,5-dimethoxyphenyl)-6-methyl-3,4-dihydropyrimidin-2(1H)-thione and 2,5-dimethoxybenzladehyde under aldol condensation condition. The title compound, (E)-3-(2,5-dimethoxyphenyl)-1-{[(4-(2,5-dimethoxyphenyl)-6-((E)-2,5-dimethoxystyryl)-2-thioxo-1,2,3,4-tetrahydropyrimidin-5-yl)]}prop-2-en-1-one (yield 15%), was obtained as major product, whereas (E)-3-(2,5-dimethoxyphenyl)-1-{[(4-(2,5-dimethoxyphenyl)-6-methyl-2-thioxo-1,2,3,4-tetrahydro pyrimidin-5-yl)]}prop-2-en-1-one (yield 8%) as side product through vinylogous aldol condensation.

A new compound belonging to a dihydrotetrazolopyrimidine derivative, that is, ethyl 5-methyl-7-(4-morpholinophenyl)-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate, was successfully synthesized using a Biginelli reaction between 4-morpholinobenzaldehyde, ethyl acetoacetate, and 5-aminotetrazole with p-toluenesulfonic acid (pTSA) as a catalyst in ethanol under reflux. The molecular structure of the title compound was characterized on the basis of spectroscopic evidence, using FTIR, HRESI-MS, 1H- and 13C-NMR, and 2D NMR.

A one-pot multicomponent reaction has been used to synthesize the title compound, ethyl 4-[5-(methoxymethyl)furan-2-yl]-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate by PTSA catalyzed Biginelli reaction. The chemical structure of the product was confirmed by spectroscopic evidence, FTIR, HRESI-MS, 1D-, and 2D NMR.

A new compound belonging to the “heterostilbene” derivative, namely ethyl (E)-4-(2,4-dimethoxyphenyl)-6-(2,4-dimethoxystyryl)-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate (2), has been successfully synthesized as an unprecedented side product of the Biginelli reaction between 2,4-dimethoxybenzaldehyde, ethyl acetoacetate and urea, employing PTSA as catalyst in reflux conditions and using ethanol as solvent. The molecular structure of compound (2) was established by FTIR, HRESIMS, 1D and 2D NMR.