Hydrochloric Acid → (3,5-Difluorophenyl)thiourea

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Benzoyl chloride (5.44 g, 38.73 mmol) was added to a stirred solution of ammonium thiocyanate (3.83 g, 50.35 mmol) in acetone (80 mL) at 30° C. The mixture was stirred at reflux for 30 minutes, then cooled to 50° C., and a solution of 3,5-difluoroaniline (5.00 g, 38.73 mmol) in acetone (10 mL) was added in one portion. The mixture was stirred at reflux for 30 minutes. A solution of NaOH (5.42 g, 135.54 mmol) in water (65 mL) was added, and the mixture was stirred at reflux for 20 minutes and then cooled to 20° C. Concentrated HCl was added to adjust the acidity to pH=5, and then the mixture was adjusted to slightly alkaline by the addition of conc. ammonium hydroxide. After 30 minutes, the mixture was cooled to 10° C. and extracted with EtOAc, and the combined organic layer was washed with brine, filtered, and concentrated to afford N-(3,5-difluorophenyl)thiourea (3.52 g, 48%). ret. time 1.73; m/z 189.0 (MH+); 1H NMR (400 MHz, MeOH-d4) δ 6.72 (m, 1H), 7.16 (m, 2H).

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