A Mini review Synthesis of Hydantoin and Thiohydantoin and related compounds using conventional, microwave and green chemistry methods

In alkaline medium the benzil reacts with urea or thiourea in presence of base like 30% w/v NaOH, using ethanol as solvent to give the cyclic hydantoin compounds, or phenytoin (5,5’dipenylimidazolidine-2,4-dione) and thiohydantoin (5,5-diphenyl-2-thioimidazolidine-4-one) respectively. The first step in the reaction involve the attack by urea or thiourea on the carbonyl group of the benzil to give a diol, which then eliminate water and gave the final compounds. Phenytoin and thiophenytoin is the anticonvulsant agents. The application of green chemistry principles, thiophenytoins were prepared by condensation of benzil and substituted aryl thioureas in alkaline condition and water as green solvent. These compounds were also prepared by microwave method, in this method yield of phenytoin was obtained in 80% while in conventional Biltz’s method the yield rarely exceeded 50%. The microwave method can be profitably performed using microwave activation. All compounds were characterized by its spectral analysis.