Synthesis
Add 3-bromo-5-nitrobenzoic acid (25 g, 101.6 mmol) and anhydrous ethanol (200 mL) to a 500 mL round bottom flask. With stirring at 0 °C, sulfoxide chloride (15 mL) was added slowly and dropwise. The reaction mixture was warmed to 80 °C with continuous stirring for 4 hours. Upon completion of the reaction, the reaction was quenched by the addition of 50 mL of water. The reaction mixture was extracted with dichloromethane (3 x 50 mL), the organic layers were combined and concentrated under reduced pressure. The concentrated residue was purified by silica gel column chromatography with ethyl acetate/petroleum ether as eluent (gradient elution, 1:20 to 1:10). Ethyl 3-bromo-5-nitrobenzoate 27.5 g (99% yield) was obtained as a white solid.
References
[1] Patent: WO2017/184623, 2017, A1. Location in patent: Page/Page column 127
[2] Bioorganic and Medicinal Chemistry Letters, 2011, vol. 21, # 13, p. 3992 - 3996
