[Br:1][C:2]1[CH:11]=[CH:10][C:5]2[N:6]=[C:7]([NH2:9])[S:8][C:4]=2[CH:3]=1.[CH3:12][C:13](=O)[CH2:14][CH2:15][C:16](=O)[CH3:17].CC1C=CC(S([O-])(=O)=O)=CC=1.C1C=C[NH+]=CC=1.O>C1C=CC=CC=1>[Br:1][C:2]1[CH:11]=[CH:10][C:5]2[N:6]=[C:7]([N:9]3[C:16]([CH3:17])=[CH:15][CH:14]=[C:13]3[CH3:12])[S:8][C:4]=2[CH:3]=1
A solution 6-bromobenzo[d]thiazol-2-amine (5.75 g, 25.1 mmol), hexane-2,5-dione (2.95 mL, 25.1 mmol), and PPTS (0.95 g, 3.76 mmol) in benzene (100 ml) was refluxed for 16 h while water was removed with a Dean-Stark trap. The cooled mixture was poured into EtOAc (100 mL) and extracted with saturated aq. NaHCO3 (2×100 mL) and brine. The organic layer was dried over Na2SO4, filtered and concentrated in vacuo. The crude product was purified by column chromatography on silica gel using 9:1 EtOAc:hexanes as the eluent to give the title compound as an orange oil (6.46 g, 84%).
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