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To a mixture of 4,5-dibromothiophenecarboxylic acid (9.8 mmoles, 2.8 g) in t-BuOH (20 mL) was added DPPA (12.5 mmoles, 2.7 ml_) and triethylamine (29 mmole, 4.2 mL). The mixture was heated to 85 0C for 12 h under an atmosphere of N2. After cooling to RT, the reaction was concentrated in vacuo. Flash chromatography (silica gel, hexanes/EtOAc, 10:1)) gave the title compound (2.6 g, 74percent) as a white solid. LCMS (ES) m/z 357 (M+H)+.
Reference:
[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