New robust protocols for the solid phase synthesis of 5-alkylthio-, 5-alkyl/aryl-, and 5- acylamino-2-alkylamino-[1, 3, 4]-thiadiazoles are described based on a common resin bound thiosemicarbazide. A protocol for the solid phase synthesis of 2-alkyl/aryl-amino-5- alkylamino-[1, 3, 4]-oxadiazoles from a resin bound semicarbazide is likewise reported. The protocols have been verified by the preparation of four small libraries that all gave ...