Synthesis
The general procedure for the synthesis of 1,3-dibromo-5-iodobenzene from 2,6-dibromo-4-iodoaniline is as follows:
1. Preparation of 3,5-dibromoiodobenzene: 188.4 g of 2,6-dibromo-4-iodoaniline and 600 g of hypophosphorous acid were added to the reaction vessel at room temperature and stirred well. Subsequently, a solution formed by dissolving 34.5 g of sodium nitrite in 60 ml of water was added dropwise. The reaction is violently exothermic and the reaction temperature needs to be controlled at 20-25°C by means of a water bath. After the dropwise addition was completed, the reaction was continued for about 3 hours until a large white solid precipitate was observed. The reaction was continued at this temperature for 1 hour. The progress of the reaction was monitored by HPLC and stopped when the raw material 2,6-dibromo-4-iodoaniline completely disappeared. The crude product was collected by filtration.
2. Purification of the crude product: the crude product was dispersed in three 1000 ml flasks, 700 ml of anhydrous ethanol was added to each flask, and the product was heated to reflux (ca. 80 °C) to completely dissolve the product. Subsequently, it was cooled to 20-25 °C, the crystals were collected by filtration and dried under reduced pressure at 60 °C to obtain white needle-like crystals of 136 g. The purity of the product, 3,5-dibromo-2-iodobenzene, was 99.72% by HPLC analysis and the reaction yield was 75.2%.
References
[1] Atti della Accademia Nazionale dei Lincei, Classe di Scienze Fisiche, Matematiche e Naturali, Rendiconti, 1913, vol. <5> 22 I, p. 823
[2] Atti della Accademia Nazionale dei Lincei, Classe di Scienze Fisiche, Matematiche e Naturali, Rendiconti, 1914, vol. <5> 23 I, p. 283 Anm.
[3] Journal of the American Chemical Society, 2002, vol. 124, # 29, p. 8661 - 8666
[4] Journal of Organic Chemistry, 2015, vol. 80, # 2, p. 882 - 896
[5] Patent: CN105523884, 2016, A. Location in patent: Paragraph 0014; 0016; 0017
