New hydrantoin derivatives

The invention comprises compounds of the general formula (wherein R1 stands for an o-substituted phenyl radical which may optionally bear one or more additional substituents in the remaining positions of the phenyl radical, the substituent(s) being selected from halogen atoms and methyl, trifluoromethyl, methoxy, phenyl, halophenyl and nitro groups, and R2 stands for a hydrogen atom or a C1-4 alkyl group), pharmaceutical preparations containing them, and their preparation by (a) reacting an aminonitrile of the formula with R1NCO and heating the product with a strong acid in an aqueous medium, (b) heating a ureido derivative of the formula with a strong acid in an aqueous medium or (c) heating an iminohydantoin of the formula with a strong acid in an aqueous medium. The following intermediates are prepared from the starting materials indicated in parentheses: 2 - (p - bromophenyl) 5 bromophenylisocyanate (2 - (p - bromophenyl) - 5 - bromoaniline); 2 - (p - chlorophenyl) - 5 - chlorophenylisocyanate (2 - (p - chlorophenyl) - 5 - chloroaniline); 2 - (p - fiuorophenyl) - 5 - fluorophenylisocyanate (2 - (p - fluorophenyl) - 5 - fluoroaniline hydrochloride); o - iodophenylisocyanate (o - iodoaniline); o - bromophenylisocyanate (o - bromoaniline) 4 - chloro - 2 - trifluoromethylphenylisocyanate (4 - chloro - 2 - trifluoromethylaniline). The compounds of the invention are anticonvulsants useful in the treatment of epilepsy, and may be administered orally in the form of pharmaceutical preparations (e.g. tablets, capsules, aqueous or oily solutions or suspensions, dispersible powders or granules, syrups or elixirs) containing them together with a diluent or carrier.