19952-47-7

333-20-0

95-51-2

19952-47-7

GENERAL METHOD: A solution of o-chloroaniline (2 mmol) in acetonitrile (15 mL) was slowly added to a solution of potassium thiocyanate (8 mmol) in acetonitrile (15 mL). Subsequently, nano BF3/SiO2 catalyst (0.06 g, 30 mol% BF3) was added to the reaction system and the mixture was placed in an ice-salt bath and mechanically stirred for 30 min. A solution of bromine (4 mmol, 0.2 mL) in acetonitrile (3 mL) was slowly added through a dropping funnel, and the rate of dropping was controlled to ensure that the reaction temperature did not exceed 0 °C. After the bromine solution was added, the reaction mixture continued to be stirred at room temperature for 4 h, during which the progress of the reaction was monitored by TLC. Upon completion of the reaction, the mixture was poured into water and heated to 70 °C on a steam bath followed by thermal filtration to isolate the catalyst. The catalyst was washed with acetone and recycled for reuse. The filtrate was neutralized with 10% NaOH solution and the resulting precipitate was collected by filtration, dried and recrystallized from ethanol (10 mL) to give the target product 2-amino-4-chlorobenzothiazole. All products were characterized by physical properties and spectral data including FT-IR, 1H NMR and 13C NMR and confirmed by comparison with known standards.