General procedure for the synthesis of tert-butyl 4-bromothiazole-2-methylamine from N-BOC-2-amino-5-bromothiazole: diisopropylamine (2.3 mL, 16 mmol) was dissolved in 30 mL of THF at 0 °C. To this solution, 2.5 M hexane solution of butyl lithium (6.4 mL, 16 mmol) was slowly added and the reaction mixture was stirred at the same temperature for 20 min. Subsequently, tert-butyl 5-bromothiazol-2-ylcarbamate (1.5 g, 5.4 mmol) was dissolved in 8 mL of THF and slowly added dropwise to the reaction system. After 15 minutes of reaction, the reaction was quenched by the addition of about 2 mL of water and the mixture was gradually warmed to room temperature with continued stirring for 12 hours. Upon completion of the reaction, the reaction mixture was diluted with 30 mL of 1/2 saturated aqueous NH4Cl and transferred to a dispensing funnel. It was extracted twice with 5 mL EtOAc, and the organic phases were combined, washed with brine and dried over MgSO4. After filtration, the organic phase was concentrated under reduced pressure to give tert-butyl 4-bromothiazol-2-ylcarbamate (1.5 g, 100% yield) as a brown solid.
