Synthesis of 6-[4-(allyl/phenyl)-5-thioxo-1,2,4-triazol-3-yl]pyrimidine-2,4-diones and their reaction with electrophiles

Cyclization of 1-(2,4-dioxo-1,2,3,4-tetrahydropyrimidin-6-yl)carbonyl-4-R-thiosemicarbazides in basic medium gave 6-(4-R-5-thioxo-1,2,4-triazol-3-yl)pyrimidine-2,4-diones (R = Allyl, Ph). Alkylation of the latter with iodomethane occurred at the sulphur atom to give the corresponding methylsulfanyl derivatives. Acetylation using acetyl chloride occurred at the N₍₁₎ atom of the triazole ring to the corresponding acetyl derivative when R = Ph but for R = Allyl the acetylation did not occur under the same conditions. In the presence of bromine in refluxing methanol the indicated allyl-substituted compound cyclizes to 6-bromomethyl-3-(2,4-dioxo-1,2,3,4-tetrahydropyrimidin-6-yl)-5,6-dihydrothiazolo2,3-c]-1,2,4-triazole. Under Mannich and bromination conditions the methylsulfanyl derivatives prepared form derivatives at the 5 position of the uracil ring: 5-methylmorpholino-(piperidino)-and 5-bromo-(4-R-5-thioxo-1,2,4-triazol-3-yl)pyrimidine-2,4-diones respectively. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 906–912, June, 2006.