A mixture of 6-aminobenzothiazol-2-yl tert-butyl carbamate (Intermediate 4, 0.796 g, 3.0 mmol), 4-chloro-3-(trifluoromethyl)phenyl isocyanate (0.731 g, 3.3 mmol) and dimethylformamide (80 mL) was stirred overnight at r.t. Water was added, the resulting precipitate was filtered off, washed thoroughly with water and dried. The so obtained material was suspended in dichloromethane (15 mL) and trifluoroacetic acid (15 mL) was added. After stirring for 1.5 h at r.t., the volatiles were removed in vacuo and dimethylformamide (20 mL) was added to the residue. The solution was neutralised by adding saturated sodium hydrogencarbonate solution. Water was added and the resulting precipitate was filtered off, washed with water and dried (grey solid, 0.999 g, 2.58 mmol, 86%). LC/ESI-MS: m/z=387 [M(35Cl)+H]+; m/z=385 [M(35Cl)−H]−; Rt=3.54 min.
