Synthesis
(3) Reduction reaction: 13.1 g of 3-nitro-4-bromophenol and 66 g of anhydrous ethanol were added to a 250 mL three-necked flask and stirred until completely dissolved. Subsequently, 1.3 g of iron oxide catalyst and 11.3 g of 80% (w/w) hydrazine hydrate solution were added. A reflux condensing unit was installed, heated to reflux and kept for 1.5 hours. Upon completion of the reaction, complete consumption of the feedstock was confirmed by TLC monitoring, the heating was stopped and the filtration was carried out after cooling to room temperature. The filtrate was concentrated to dryness under reduced pressure, 16 mL of deionized water was added to the residue, and the pH was slowly adjusted with 10% hydrochloric acid solution under stirring to 7. At this point, a solid precipitated, and the crude product was collected by filtration, with a wet weight of about 15 g. The crude product was purified by recrystallization: the crude product was dissolved in 17 g of ethanol preheated to 60 °C until just soluble, followed by the addition of 17 g of deionized water, and stirring for 10 min. After standing at room temperature for 30 min, it was transferred to an ice water bath and continued cooling for 30 min to promote crystallization. The crystals were collected by filtration to give 8.0 g of light pink needle-like crystals (3-amino-4-bromophenol), which were analyzed by HPLC for 99% purity and 70.9% yield.
