6283-25-6

4533-95-3

General procedure for the synthesis of 2-chloro-5-nitrobenzenesulfonyl chloride from 2-chloro-5-nitroaniline: 2-chloro-5-nitrobenzene-1-sulfonyl chloride (37) was prepared as shown in Scheme 5. First, 2-chloro-5-nitroaniline (10 g) was added in batches to hydrochloric acid (100 mL) cooled in an ice bath until complete dissolution. Subsequently, an aqueous sodium nitrite solution (6.0 g, dissolved in 50 mL of water) was added dropwise and the reaction mixture was stirred at 0 °C for 1 hour. Next, the resulting diazonium ion solution was slowly added to acetic acid (500 mL) pre-saturated with sulfur dioxide gas, which contained ice bath cooled copper chloride dihydrate (5 g). The reaction mixture was continued to be stirred at 0°C for 1 hr and then carefully added to the ice-water slurry in batches while maintaining vigorous stirring. The precipitated solid was collected by filtration, washed with water and dried under vacuum to afford the target product 37 as a cream colored powder (8.2 g, 55% yield). The product was characterized by 1H NMR (500 MHz, DMSO-d6): δ 8.61 (d, J=3Hz, 1H), 8.16 (dd, J1=9Hz, J2=3Hz, 1H), 7.70 (d, J=9Hz, 1H).