Ultrasound-enhanced Green Synthesis of 5,5-Diphenylhydantoin Derivatives Using Symmetrical or Unsymmetrical Benzils

A rapid, highly efficient and mild green synthesis of 5,5-diphenylhydantoin derivatives was achieved from the reaction of symmetrical or unsymmetrical benzil derivatives with urea in the presence of ethanolic KOH under ultrasound irradiation. This simple method affords 5,5-diphenylhydantoin derivatives at room temperature in short reaction time with high yield and purity. This study aimed to overcome the limitations and drawbacks of the reported methods such as tedious work-up, low yield and long reaction time.