General procedure for the synthesis of 1,2,3-trichloro-5-nitrobenzene from 2,6-dichloro-4-nitroaniline: 96 g of 98% concentrated sulphuric acid was added to the reaction flask at 20 °C, 7.2 g of sodium nitrite was added slowly with stirring, and then the temperature was raised to 70 °C. After the sodium nitrite was completely dissolved, the solution was cooled to 50°C. 20g of 2,6-dichloro-4-nitroaniline was added at once and the reaction was maintained at this temperature for 1 hour. After the reaction was completed, the mixture was cooled to 5 °C and 27.3 g of glacial acetic acid was slowly added dropwise. After the dropwise addition was completed, stirring was continued for 1 hour to obtain a 2,6-dichloro-4-nitroaniline diazonium salt solution. In another reaction flask, 18 g of cuprous chloride and 7.14 g of concentrated hydrochloric acid were added. The above diazonium salt solution was slowly added dropwise to this reaction flask under rapid stirring, keeping the temperature below 15 °C. After completion of the dropwise addition, the reaction was maintained for 1 hour, followed by raising the temperature to 70°C to continue the reaction for 1 hour. At the end of the reaction, the mixture was cooled to room temperature, poured into a 2L reaction flask, and 60 g of water was added under stirring. 0.5 h later, filtration was carried out to obtain 1,2,3-trichloro-5-nitrobenzene as a yellow solid with a dry weight of 21.5 g. The yield was 98.5%, and the purity was 98.3% by HPLC.
