Imidazo[2,1-b]-1,3,4-thiadiazolo[3,2-a]pyrimidone-(6) aus 2-Acetoacetylamino-imidazo[2,1-b]-1,3,4-thiadiazolen

Imidazo[2,1-b]-1,3,4-thiadiazolo[3,2-α]pyrimidin-6-ones by Cyclisation of 2-(Acetoacetylamino)-imidazo[2,1-b]-1,3,4-thiadiazoles The 2-acetoacetylamino-6-methyl- (or -aryl) imidazo[2,1-b]-1,3,4-thiadiazoles 1, 2a–f cyclise on heating in polyphosphoric acid (PPA) to yield the tricyclic 2,8-dimethyl- or 2-aryl-8-methyl-imidazo[2,1-b]-1,3,4-thiadiazolo[3,2-α]pyrimidin-6-ones 3, 4a–f . Only 4c inhibits the growth of vaccinia viruses. The other compounds have no antiviral activity.