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Step 3: Synthesis of 7-nitrobenzo[d]thiazol-2-amine [244] To a stirred solution of 1-(3-nitrophenyl)thiourea (5.16 g, 26.20 mmol) in chloroform (130 mL) prepared in Step 2, bromine (2.68 mL, 52.3 mmol) was slowly added dropwise at room temperature. The reaction mixture was heated to reflux for 3 hours and subsequently cooled to room temperature. The reaction mixture was diluted with isopropyl ether and filtered. The resulting solid was redissolved in water and alkalized with sodium carbonate solution to pH 11-12. The aqueous layer was extracted with ethyl acetate, the organic layers were combined and washed with brine, dried over anhydrous magnesium sulfate and filtered. The filtrate was concentrated under reduced pressure and the resulting solid was dried under reduced pressure to give 3.52 g of 2-amino-7-nitrobenzothiazole as a yellow solid (yield: 69%). [245] 1H NMR (CDCl3, 400 MHz) δ 7.95 (m, 3H), 7.73 (d, 1H), 7.47 (t, 1H).