3-BroMo-5-fluorobenzene-1-sulfonyl chloride

73183-34-3

134168-97-1

1214342-44-5

Intermediate S2: 3-bromo-5-fluorobenzene-1-sulfonyl chloride was synthesized as follows: 3-bromo-5-fluoroaniline (0.500 g, 2.63 mmol) cooled in an ice bath was dissolved in glacial acetic acid (0.70 mL), followed by the addition of concentrated hydrochloric acid (2.15 mL). A solution of sodium nitrite (0.199 g, 2.89 mmol) in water (0.45 mL) was slowly added dropwise, ensuring that the reaction temperature was maintained at about 0°C. After the dropwise addition was completed, the reaction mixture was continued to be stirred at 0 °C for 20 min. The resulting solution was slowly added to a pre-prepared mixture of ~40% aqueous sodium bisulfite (1.915 mL, 7.36 mmol), copper chloride (0.052 g, 0.526 mmol), glacial acetic acid (5.0 mL) and concentrated hydrochloric acid (1 mL). The reaction mixture was stirred at room temperature for 2.5 hours. Subsequently, the mixture was cooled to 0 °C, an additional amount of sodium nitrite (0.5 eq.) was added and stirring was continued for 1 hour at room temperature. Upon completion of the reaction, the mixture was extracted with EtOAc, the organic layer was dried with anhydrous sodium sulfate and concentrated under reduced pressure to afford 3-bromo-5-fluorobenzenesulfonyl chloride (0.450 g, 1.65 mmol, 63% yield), which could be used for the next reaction without further purification. The product was characterized by 1H NMR (400 MHz, DMSO-d6): δ 7.54-7.58 (m, 1H), 7.50-7.54 (m, 1H), 7.30-7.36 (m, 1H).