Synthesis
GENERAL STEPS: To a solution of 4,5-dibromothiophene-2-carboxylic acid (9.8 mmol, 2.8 g) in tert-butanol (20 mL) were sequentially added diphenylphosphoryl azide (DPPA, 12.5 mmol, 2.7 mL) and triethylamine (29 mmol, 4.2 mL). The reaction mixture was heated to 85 °C and stirred for 12 h under nitrogen protection. Upon completion of the reaction, it was cooled to room temperature and subsequently concentrated under reduced pressure to remove the solvent. Purification of the crude product by fast column chromatography (silica gel as stationary phase, hexane/ethyl acetate=10:1 as eluent) afforded tert-butyl (4,5-dibromothiophen-2-yl)carbamate (2.6 g, 74% yield) as a white solid. m/z LC-MS (electrospray ionization): 357 [M+H]+.
References
[1] Patent: WO2007/76423, 2007, A2. Location in patent: Page/Page column 92
[2] Bioorganic and Medicinal Chemistry Letters, 2009, vol. 19, # 8, p. 2244 - 2248
[3] Bioorganic and Medicinal Chemistry Letters, 2006, vol. 16, # 21, p. 5567 - 5571
