Ethyl 2-amino-5-chloro-1,3-thiazole-4-carboxylate (2.00 g, 9.678 mmol, 1.00 eq.) was used as starting material, which was mixed with tert-butyl nitrite (1.20 g, 11.637 mmol, 1.20 eq.) and copper bromide (2.59 g, 11.596 mmol, 1.20 eq.) in acetonitrile (50 mL). The reaction mixture was stirred at 80 °C for 2 hours. After completion of the reaction, the resulting solution was concentrated under vacuum and the obtained residue was purified by silica gel column chromatography with the eluent dichloromethane/methanol (40:1, v/v), resulting in the target compound ethyl 2-bromo-5-chlorothiazole-4-carboxylate (1.2 g, 46% yield) as a white solid. The product was confirmed by LC-MS (electrospray ionization, m/z) analysis: 270 [M + H]+.
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