General procedure for the synthesis of 2-amino-5-chlorobenzothiazole and 7-chlorobenzo[d]thiazol-2-amine from 3-chlorobenzothiourea: 3-chlorobenzothiourea (105 mg, 0.56 mmol) was dissolved in 10 mL of acetic acid. Benzyltrimethylammonium tribromide (329 mg, 0.84 mmol) was added and the reaction mixture was stirred at room temperature for 14 hours. After completion of the reaction, the acetic acid was removed by distillation under reduced pressure. The residue was redissolved in 15 mL of dichloromethane (DCM) and 10 mL of 0.5 N aqueous sodium hydroxide was added. The aqueous phase was extracted with dichloromethane (2 x 15 mL). The organic layers were combined, filtered through a phase separator and concentrated under reduced pressure to remove the solvent. The crude product was purified by fast column chromatography using pentane-ethyl acetate (12:5) as eluent to afford the target product 2-amino-5-chlorobenzothiazole (61 mg, 59% yield) as a white solid. The structure of the product was analyzed by 1H NMR (500 MHz, CD3OD) δ 7.05 (dd, J = 8.4, 2.0 Hz, 1H), 7.35 (d, J = 2.0 Hz, 1H), 7.53 (d, J = 8.4 Hz, 1H); 13C NMR (125 MHz, CD3OD) δ 117.41, 121.45, 121.60 129.37, 131.55, 153.24, 170.04; Mass Spectrometry (ESI): m/z 185 [M + H]+ confirmed.
