Abstract
The individual reactions of acetyl group rearrangement are examined to elucidate the complicated formation of five acetylated products of 3-methylpyrazol-5-one (I). In heated acetic acid-anhydride mixture the initially formed 2-acetyl-3-hydroxy-5-methylpyrazole (II) reacts further to produce 1-acetyl-3-hydroxy-5-methylpyrazole (III), 3-acetoxy-2-acetyl-5-methylpyrazole (IV) and finally 3-acetoxy-1-acetyl-5-methylpyrazole (V), while inter- as well as intra-molecular acetyl transfer reaction takes place. The diacetate (V) is a sort of activated ester and is proved to be effective as a mild acetylating reagent of primary and secondary amines.
