Synthesis of tert-butyl 2-bromothiazole-5-carbamate: 2-bromothiazole-5-carboxylic acid (2.29 g, 11.0 mmol) was added to a 250 mL round bottom flask and ground to a fine powder using a spatula. Tert-butanol (12.2 mL, 11.0 mmol) and triethylamine (TEA, 1.53 mL, 11.0 mmol) were then added and rapid dissolution of the solid was observed. Diphenylphosphoryl azide (DPPA, 2.61 mL, 12.1 mmol) was then added, and the flask was sealed with a rubber septum and the sealed flask was heated in an 80 °C oil bath. After 10 hours of reaction, the reaction mixture was transferred to a partition funnel and extracted with saturated saline (100 mL) and ethyl acetate (EtOAc, 100 mL). The organic layer was separated and dried over anhydrous sodium sulfate. The dried organic phase was concentrated onto silica gel and purified by rapid column chromatography on a Redi-Sep pre-populated silica gel column (120 g) using a gradient elution of 0% to 80% ethyl acetate in hexane. The final target product, tert-butyl 2-bromothiazole-5-carbamate (2.02 g, 66% yield), was obtained as an off-white crystalline solid. It was analyzed by LCMS (API-ES) and measured m/z (relative abundance): 279 (100%, [M-H]-).
