Reaction of 2-Amino-5-Substituted-l, 3, 4-Thiadiazole with 1, 3-Dicarbonyl Compound

The synthesis of thiadiazolopyrimidines by heating a-amino-l, 3,4-thiadiazoles with 1,Sdicarbonyl compounds in polyphosphoric acid has been investigated. The products obtained from 2-amino-l, 3,4_thiadiazoles with ,&keto-esters were 5H_thiadiazolo[3,2-a]pyrrmrdrn-5-ones, and those obtained from 2-amino-1,3,4_thiadiazoles with 1, S-dicarbony1 compounds were thiadiazolo 13, 2-alpyrimidin-4-ium compounds. It was also found that the reaction of 2-amino-5-mercapto-1,3,4-thiadiazole with alkyl acetoacetate yielded 7-methyl-2-alkylthio-FiH-thiadiadiazolo[3,2-a]pyrimidin-5-one