N[C:2]1[S:3][C:4]2[CH:10]=[C:9](O)[CH:8]=[CH:7][C:5]=2[N:6]=1.[CH3:12][C:13]([Si](Cl)(C)C)([CH3:15])C.[NH:20]1[CH:24]=[CH:23][N:22]=[CH:21]1.[CH3:25][N:26](C=O)C>>[CH3:25][NH:26][C:9]1[CH:8]=[CH:7][C:5]2[N:6]=[C:2]([C:12]3[CH:23]=[N:22][C:21]([NH:20][CH3:24])=[CH:15][CH:13]=3)[S:3][C:4]=2[CH:10]=1A solution of 2-amino-6-hydroxybenzothiazole (5.00 g, 30.1 mmol), TBDMSCl (5.40 g, 1.2 equiv) and imidazole (2.46 g, 1.2 equiv) in DMF (160 ml) was stirred at ambient temperature for 16 h. The reaction mixture was then partitioned between water and ethyl acetate. The aqueous phase was extracted twice with ethyl acetate and the combined organics dried (MgSO4) and concentrated in vacuo. The crude product thus obtained was purified by silica gel chromatography by gradient elution (n-heptane:ethyl acetate) to yield 3.0 g of the title compound as a yellowish solid. 1H NMR δ 7.23 (br s, 2H) 7.18 (d, 1H) 7.16 (d, 1H) 6.70 (dd, 1H) 0.95 (s, 9H) 0.16 (s, 6 H); MS m/z (M+H) 281.
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