[Br:1][C:2]1[C:3]([O:13][CH3:14])=[C:4]([Br:12])[C:5]2[S:9][C:8]([NH2:10])=[N:7][C:6]=2[CH:11]=1.C(N(CC)CC)C.[CH2:22]([N:24]=[C:25]=[O:26])[CH3:23]>CS(C)=O.O>[Br:1][C:2]1[C:3]([O:13][CH3:14])=[C:4]([Br:12])[C:5]2[S:9][C:8]([NH:10][C:25]([NH:24][CH2:22][CH3:23])=[O:26])=[N:7][C:6]=2[CH:11]=15,7-Dibromo-6-methoxy-1,3-benzothiazol-2-amine (208 mg, 0.62 mmol) was dissolved in anhydrous DMSO (1 mL) and triethylamine (0.189 mL, 1.35 mmol) followed by ethyl isocyanate (0.058 mL, 0.74 mmol). The mixture was stirred at rt. A further aliquot of ethyl isocyanate (0.058 mL, 0.74 mmol) was added after 3 h. After 3.75 h, the mixture was diluted with water and extracted into EtOAc (3×30 mL). The combined organic phases were washed with water and brine, dried over Na2SO4 and concentrated to dryness under reduced pressure. The desired compound was obtained as a pale yellow solid, 234 mg (93%). The material was used without further purification in the next step. m/z: 407.83/409.83/411.81 [M+H]+.
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