Methods for controlling the regioselection in the reaction of 3-amino-5-benzylthio-1,2,4-triazole with acetylacetaldehyde dimethyl acetal

The reaction of 3-amino-5-benzylthio-1,2,4-triazole with acetylacetaldehyde dimethyl acetal affords 2-benzylthio-5-methyl-1,2,4-triazolo[1,5a]pyrimidine or 2-benzylthio-7-methyl-1,2,4-triazolo[1,5a]pyrimidine regioselectively depending on the reaction conditions.