Synthesis
A solution of glacial acetic acid (75 mL) and 3-aminopiperidine-2,6-dione hydrochloride (8.5 g) was added to a round bottom flask. Anhydrous sodium acetate (4.5 g) was added to the solution in batches at 25 °C to 30 °C, followed by 3-nitrophthalic anhydride (10 g) at the same temperature. The reaction mixture was stirred at 118 °C for 18 hours. After completion of the reaction, the reaction material was cooled to 60 °C and the solvent was removed by distillation under vacuum to obtain a residue. Water (100 mL) was added to the residue and the mixture was stirred at 25 °C to 30 °C for 1 hour, followed by filtration. The wet filter cake was slurried with water (100 mL x 2), filtered and dried in an air pan drier to less than 0.5% water to give 2-(2,6-dioxopiperidin-3-yl)-4-nitroisoindoline-1,3-dione (14 g). Yield: 89.7%, purity: 98%.
References
[1] Patent: US2017/260157, 2017, A1. Location in patent: Page/Page column 5
[2] Patent: CN104926786, 2017, B. Location in patent: Paragraph 0044; 0045
[3] Synthetic Communications, 2016, vol. 46, # 16, p. 1343 - 1348
[4] Bioorganic and Medicinal Chemistry Letters, 1999, vol. 9, # 11, p. 1625 - 1630
[5] Patent: CN104402863, 2016, B. Location in patent: Paragraph 0035
