General procedure for the synthesis of methyl 2-bromobenzothiazole-6-carboxylate from methyl 2-aminobenzothiazole-6-carboxylate: to a solution of methyl 2-aminobenzothiazole-6-carboxylate (1.11 g, 5 mmol) and copper(II) bromide (2.23 g, 10 mmol) in acetonitrile (50 mL) was added slowly at 0 °C tert-butyl nitrite (1.32 mL, 10 mmol). The reaction mixture was stirred at room temperature overnight. After completion of the reaction, the mixture was extracted with ethyl acetate. The organic phase was washed sequentially with saturated sodium bicarbonate solution and brine. The solvent was removed by concentration under reduced pressure and the crude product was purified by fast column chromatography (eluent: hexane/ethyl acetate, 10:1, v/v) to afford methyl 2-bromobenzothiazole-6-carboxylate. The product was characterized by 1H NMR (400 MHz, CDCl3): δ 8.53 (d, 1H), 8.15 (dd, 1H), 8.01 (d, 1H), 4.42 (q, 2H), 1.42 (t, 3H). Mass spectrum (ESI) m/z: 271.9 ([M + H]+).
![methyl 2-bromobenzo[d]thiazole-6-carboxylate](/CAS2/GIF/1024583-33-2.gif)