[Cl:1][C:2]1[CH:3]=[C:4]([NH:9][C:10](=[O:16])[NH:11][CH2:12][C:13](O)=[O:14])[CH:5]=[C:6]([Cl:8])[CH:7]=1.CS(O)(=O)=O.O>ClC1C=CC=CC=1>[Cl:1][C:2]1[CH:3]=[C:4]([N:9]2[C:13](=[O:14])[CH2:12][NH:11][C:10]2=[O:16])[CH:5]=[C:6]([Cl:8])[CH:7]=1To a suspension of 3-(3,5-dichlorophenyl)-ureidoacetic acid (526 g.) in chlorobenzene (2,250 cc.) is added methanesulphonic acid (d = 1.48) (10 cc., representing 0.077 mol per mol of ureidoacetic acid). The water formed in the reaction is removed by azeotropic distillation. After 45 minutes' distillation, a limpid solution is obtained. After cooling to about 15° C, the precipitate formed is filtered off and washed on the filter with ethanol (500 cc.) at 10° C. After drying, 3-(3,5-dichlorophenyl)-hydantoin (467 g.) melting at 199° C is obtained. Yield: 94%.
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