Synthesis of Potentially Biologically Active Fused Polyheterocycles Containing a Pyrimidine Unit

A number of new fused polyheterocyclic compounds were synthesized on the basis of 2-amino-6-sulfanylpyrirnidin-4(3 H )-one. In particular, reactions of 2-amino-6-suffanylpyrirnidin-4(3 H )-one with cinnamic acids, aroyl isothiocyanate, and acetic anhydride afforded imidazo[1,2 -a ]thieno[2,3 -d ]pyrimidine, [1,3]thiazino[6′,5′: 4,5]pyrimido[1,2- a ][1,3,5]triazine, and imidazo[1,2- a ]tWeno[2,3- d ]pyrimidine derivatives, respectively. The alkylation of 2-amino-6-smfanylpyrirnidin-4(3 H )-one with benzyl chloride gave 3-benzyl-6-(benzylsulfanyl)-2-imino-2,5-dihydropyrimidin-4(3 H )-one which was converted to [1,3]thiazolo[5,4- d ][1,2,4]triazolo-[4,3- a ]pyrimidine, imidazo[1,2- a ]pyrimidine, dihydropyrimido[4,5- b ]quinoline, imidazo[1,2- a ]pyrrolo[2,3- d ]-pyrimidine, and benzo[ g ]imidazo[2,1- b ]pteridine derivatives via reactions with nitrous acid, ethyl chloroacetate, and aniline (followed by treatment with carbon disulfide, cinnamic acid, or sodium nitrite in acetic acid). 2-Amino-3,4-dihydropyrimidin-6-sulfonic acid was obtained by oxidation of the same substrate with hydrogen peroxide in alkaline medium. Some of the synthesized compounds showed antimicrobial activity.