3-Formylbenzenesulfonyl Chloride

3-Formylbenzenesulfonyl Chloride 

A suspension of bisulphite adduct 3 (300 g, 1.4 mol) and anhydrous potassium sulfate powder (174 g; 1.0 mol) in DCM (3 L) was stirred at 0–5 °C, and chlorosulfonic acid (560 mL, 8.6 mol) was added dropwise into the suspension while maintaining the temperature below 30 °C (caution: highly exothermic). When the addition completed over 6 h, the reaction mixture was further stirred at 25–30 °C for 22 h. After the completion of the reaction, monitored by TLC, the reaction mixture was slowly poured into crushed ice (3 kg) and stirred for 1 h. The aqueous phase was removed, and the organic phase was washed with water (2 L) followed by 5% aqueous solution of sodium bicarbonate (1 L) and brine (1 L) before being dried over anhydrous sodium sulfate. The sodium sulfate was filtered off and the filtrate was concentrated in vacuum (10–15 Torr, pot temperature of 20 °C) to afford crude 4

The crude 4 was dissolved in toluene (300 mL) and then the solution was taken ahead as such for the purification. The silica gel (1.2 kg) was carefully poured into a column (diam: 10 cm), and compressed air was used to pack the column. After 1 h, a portion of the solution (one-sixth of the total) was added and pressed into the dry silica gel using compressed air. When added solution was all deposited on silica, another portion was added, and repeated until all six portions were added. After the portion-wise addition, the column was eluted with toluene (7.3 L), and the eluent was concentrated in vacuum (10–15 Torr, pot temperature below 35 °C) to afford light yellow oil 3-formylbenzenesulfonyl chloride (203 g, 69%). (caution: 3-formylbenzenesulfonyl chloride 4 was more likely to convert into strong-polarity impurities when the pot temperature was higher than 40 °C).

1H NMR (CDCl3, 400 MHz) δ = 10.13 (s, 1H,), 8.53 (s, 1H), 8.31–8.26 (m, 2H), 7.85 (t, J = 8.0 Hz, 1H).

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