[F:1][C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][C:3]=1[C:8](=O)[CH3:9].[C-:11]#[N:12].[K+].[C:14](=[O:17])([O-])[O-].[NH4+:18].[NH4+].[OH-:20].[NH4+]>C(O)C.O>[F:1][C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][C:3]=1[C:8]1([CH3:9])[NH:18][C:11](=[O:20])[NH:12][C:14]1=[O:17]
A mixture of freshly distilled 1-(2-fluorophenyl)ethanone (27.6 g, 24.6 ml, 200 mmol, Eq: 1.00), potassium cyanide (15.6 g, 240 mmol, Eq: 1.20), ammonium carbonate (96.1 g, 1.00 mol, Eq: 5.00) and ammonium hydroxide (25%) (130 g, 145 ml, 931 mmol, Eq: 4.65) in ethanol (250 ml) and water (200 ml) was stirred at 60° C. for 5.5 h. The ethanol was removed in vacuum, then cooled to 0° C., cautiously acidified the residue to pH 1, the precipitate was filtered off, washed with dilute HCl and dried at 50° C. first at rotary evaporator, then at high vacuum to give the 5-(2-fluorophenyl)-5-methylimidazolidine-2,4-dione (40.4 g, 194 mmol, 97.0% yield) as a white solid. MS (ISN): m/z=207.5 [M−H]−.
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