A mixed solution of diisopropylamine (8.28 mL, 59.1 mmol) and 100 mL of tetrahydrofuran (THF, 1.29 g, 17.9 mmol) was added to a 500 mL round bottom flask. The reaction system was cooled to 0 °C, followed by the slow addition of n-butyllithium (2.5 M hexane solution, 23.6 mL, 59.1 mmol). The reaction mixture was stirred at 0 °C for about 20 min, followed by the slow addition of tert-butyl 5-bromothiazol-2-ylcarbamate (5.00 g, 17.9 mmol) in THF solution. After continued stirring for 30 min, the reaction was quenched by dropwise addition of N,N-dimethylformamide (DMF, 4.58 mL, 59.1 mmol). The reaction mixture was stirred at room temperature for about 12 hours. Upon completion of the reaction, the mixture was partitioned between water and ethyl acetate (EtOAc) and the aqueous layer was extracted with ethyl acetate (2 x 100 mL). The combined organic layers were washed with saturated brine, dried over anhydrous magnesium sulfate, filtered and concentrated. The crude product was purified by silica gel column chromatography using a 330 g Redi-Sep? pre-populated silica gel column eluting with a gradient of 5% to 25% ethyl acetate in hexane solution to afford tert-butyl 4-bromo-5-formylthiazol-2-ylcarbamate (3.31 g, 60.2% yield).
