Synthesis
The general procedure for synthesizing 4-nitroisophthalic acid from 1,3-dimethyl-4-nitrobenzene was as follows: referring to Example 103, 1,3-dimethyl-4-nitrobenzene (10.0 g, 66.2 mmol) was dissolved in a mixed solvent of pyridine (65.0 mL) and water (130 mL), followed by batchwise addition of potassium permanganate (62.7 g, 0.397 mol) . The reaction mixture was stirred at room temperature for 30 min. After completion of the reaction, the reaction mixture was filtered and the filtrate was concentrated by distillation under reduced pressure. The residue was acidified with 1N hydrochloric acid and subsequently extracted with ethyl acetate. After the extract was washed with water and dried with anhydrous magnesium sulfate, the solvent was removed by reduced pressure distillation to afford 4-nitroisophthalic acid (12.4 g, 89% yield) as yellow crystals. The obtained product could be directly used in the subsequent reaction without further purification.
References
[1] Patent: US6407116, 2002, B1
[2] Organic Letters, 2010, vol. 12, # 21, p. 4944 - 4947
[3] Patent: CN108164469, 2018, A. Location in patent: Paragraph 0094; 0095
[4] Tetrahedron, 1989, vol. 45, # 5, p. 1311 - 1322
[5] Patent: CN105384687, 2016, A. Location in patent: Paragraph 0394; 0395; 0396; 0397; 0398
