A convenient synthesis of 1-aryl-3-methyl-1,2,4-triazolin-5-ones from the reaction between acetone arylhydrazones and acetyl isocyanate

The reaction of acetone arylhydrazones with acetyl isocyanate gave the corresponding 4-acetyl-1-aryl-3,3-dimethyl-1,2,4-triazolidin-5-ones which eliminated acetone upon acidic hydrolysis to give 1-aryl-3-methyl-1,2,-4-triazolin-5-ones. The above transformation can be achieved in one pot by a simple solvent swap.