[CH3:1][C:2]([C:11]1[S:12][CH:13]=[CH:14][N:15]=1)([CH3:10])[C:3]([O:5][C:6]([CH3:9])([CH3:8])[CH3:7])=[O:4].[Br:16]Br>C(Cl)(Cl)Cl.[O-]S([O-])(=S)=O.[Na+].[Na+].C([O-])(O)=O.[Na+]>[Br:16][C:13]1[S:12][C:11]([C:2]([CH3:1])([CH3:10])[C:3]([O:5][C:6]([CH3:7])([CH3:8])[CH3:9])=[O:4])=[N:15][CH:14]=1
The product from Step 1 (935 mg, 4.11 mmol) was taken up in CHCl3 (20 mL) and placed in a cool water bath. NaHCO3 (380 mg, 4.52 mmol) was added, followed by bromine (1.315 g, 8.23 mmol). After stirring for 2 h at room temperature, some starting material remained, so additional NaHCO3 (380 mg, 4.52 mmol) and bromine (1.315 g, 8.23 mmol) were added. After another 2 h at room temperature, the reaction was diluted with aqueous 10% Na2S2O3 and aqueous saturated NaHCO3 and extracted with CH2Cl2 (2×). The combined organic layers were washed with brine, dried (Na2SO4), and evaporated. Flash chromatography (0-10% ethyl acetate in hexanes) afforded tert-butyl 2-(5-bromo-1,3-thiazol-2-yl)-2-methylpropanoate (1.032 g, 82%) as a colorless oil. MS ESI: [M-t-Bu]+ m/z 249.9/251.9.
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