333-20-0

108-42-9

20358-00-3

General method: a solution of m-chloroaniline (2 mmol) in acetonitrile (15 ml) was slowly added to a solution of potassium thiocyanate (8 mmol) in acetonitrile (15 ml). Subsequently, 0.06 g (30 mol%) of BF3/SiO2 nanocatalyst 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 dropping rate was controlled to ensure that the reaction temperature did not exceed 0 °C. After the addition of the bromine solution, stirring was continued at 0 °C for 60 min, after which the reaction mixture was brought to room temperature and stirred for 4 h. The reaction was carried out by thin layer chromatography (TLC). The reaction process was monitored by thin layer chromatography (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 remove 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-5-chlorobenzothiazole. The structure of the product was confirmed by the following physical and spectral data and compared with known standards. In the case of 6-bromo-1,3-benzothiazol-2-amine (2e): yellow solid; yield = 93%; melting point = 202-204 °C (literature value 203 °C); FT-IR (KBr, cm^-1 ): 3315, 3012, 2835, 1580, 1476, 1261, 920, 742, 512; ^1H NMR (400 MHz, CDCl3, δ ppm): 5.44 (s, 2H, NH2), 7.4-7.5 (d, 2H, Ar-H), 7.71 (s, 1H, Ar-H); ^13C NMR (100 MHz, DMSO-d6, δ ppm): 119, 120.9, 125.15, 126.07, 133.1, 152.15, 167.75.