N[C:2]1[S:3][C:4]2[C:10]([Br:11])=[C:9]([F:12])[CH:8]=[CH:7][C:5]=2[N:6]=1.N(OC(C)(C)C)=O>C1COCC1>[Br:11][C:10]1[C:4]2[S:3][CH:2]=[N:6][C:5]=2[CH:7]=[CH:8][C:9]=1[F:12]To a solution of impure 2-amino-7-bromo-6-fluorobenzothiazole from Step A in THF (10 mL) was added tert-butyl nitrite (90%, 1.25 mL, 9.46 mmol). The mixture was stirred at 50° C. for 7 h and then purified by ISCO chromatography (0 to 40% EtOAc:heptane) to afford 114 mg (34%) of the title compound as a yellow solid. 1H NMR (400 MHz, CDCl3): δ 7.54 (dd, J=2.4, 8.0 Hz, 1H), 7.62 (dd, J=2.4, 8.0 Hz, 1H), 9.03 (s, 1H); 19F NMR (376 MHz, CDCl3): δ−113.77; MS (ESI): 231.92/233.92 [M+H]+; HPLC tR=1.38 min (TOF: polar—3 min).
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