Synthesis
The general procedure for the synthesis of sodium 4-chlorobenzenesulfinate from 4-chlorobenzenesulfonyl chloride: chlorobenzene (3.23 g, 28 mmol) was added dropwise to chlorosulfonic acid (10 g, 86 mmol) at a strictly controlled temperature not exceeding 20°C. The reaction was carried out by stirring for 1 hour. After completion of the reaction, the reaction solution was stirred at room temperature for 1 h, followed by slow pouring into ice (50 g) for quenching. The precipitate was collected by filtration, washed with water and added in batches to a solution of sodium bisulfite (7.5 g, 60 mmol) in water (28 mL). The mixture was heated to 90 °C and stirred for 1 h, during which a 50% sodium hydroxide solution was added slowly and dropwise to maintain the pH of the reaction system between 8-9. At the end of the reaction, the reaction mixture was filtered and the filtrate was allowed to stand at room temperature for 10 hours to crystallize. Filtration gave a white crystalline 4-chlorobenzenesulfinic acid sodium salt product, which was washed with cold water and dried at room temperature. The final product 3 was obtained in 75% yield (4.3 g). The characteristic absorption peaks (cm-1 ) of the IR spectrum of the product were as follows: 1575 (aromatic C-H stretching vibration); 1340, 1130 (SO2 symmetric and asymmetric stretching vibration); 1004, 981 (C-H in-plane bending vibration); 832, 740 (C-Cl stretching vibration).
References
[1] Tetrahedron Letters, 2014, vol. 55, # 29, p. 3851 - 3855
[2] Chemistry - An Asian Journal, 2016, vol. 11, # 15, p. 2121 - 2125
[3] Acta Chemica Scandinavica, Series A: Physical and Inorganic Chemistry, 1976, vol. A30, # 8, p. 579 - 585
[4] European Journal of Medicinal Chemistry, 2007, vol. 42, # 6, p. 880 - 884
[5] Patent: WO2007/66844, 2007, A1. Location in patent: Page/Page column 14-15
