AbstractThe condensation of 3‐amino‐5‐benzylthio‐s‐triazole (2) with acetylacetone in refluxing acetic acid has been reported to have given 3‐benzylthio‐5,7‐dimethyl‐s‐triazolo[4,3‐a]pyrimidine (3). However, it has now been established, with the aid of13C spectra and a modification of the original synthetic work, that only 2‐benzylthio‐5,7‐dimethyl‐s‐triazolo[1,5‐a]pyrimidine (4) can be obtained by this method of condensation. The erroneously reported, but previously unknown6was synthesized and its structure and that of4was firmly established by ir, uv, pmr,13C nmr, tlc and mixed melting point data. The correct structures of 3‐mercapto‐5,7‐dimethyl‐s‐triazolo‐[4,3‐a]pyrimidine (5) and 2‐mercapto‐5,7‐dimethyl‐s‐triazolo[1,5‐a]pyrimidine (6) were also esta