General procedure for the synthesis of 1,3-benzothiazol-5-amine from 5-nitrobenzothiazole: A mixture of 5-nitro-1,3-benzothiazole (5.1 g, 11 mmol) and stannous(II) chloride dihydrate (8.6 g, 38 mmol) in 2-propanol (30 mL) was heated to reflux and the reaction was sustained for 24 hr. Upon completion of the reaction, the cooled reaction mixture was poured into an ice/water mixture (85 mL) and the pH was adjusted with sodium hydroxide solution to 7. Subsequently, the mixture was extracted with ethyl acetate (3 x 50 mL), and the organic layers were combined and dried over anhydrous sodium sulfate. The dried organic phase was filtered and concentrated and the residue was purified by silica gel column chromatography (eluent ratio 1:1 hexane:ethyl acetate) to afford the target product 1,3-benzothiazol-5-amine (820 mg, 52% yield). The product was characterized by LHNMR (CDCl3): δ 6.85 (1H, dd, J=2.3,8.6 Hz), 7.40 (1H, d, J=2.1 Hz), 7.66 (1H, d, J=8.4 Hz), 8.90 (1H, s).
