Synthesis
The general procedure for the synthesis of 2-(3-oxocyclopentyl)isoindole-1,3-dione from 3-hydroxy-1H-isoindol-1-one and 2-cyclopentenone was as follows: 2-cyclopentenone (100 g, 1.2 mol) and 3-hydroxy-1H-isoindol-1-one (170 g, 1.2 mmol) were dissolved in methanol (900 mL) and the reaction was stirred at room temperature for 18 hours. The reaction was vigorously stirred using a mechanical stirrer and 2 M Na2CO3 aqueous solution (80 mL) was slowly added. After about 2 hours, a thick white precipitate gradually formed in the reaction system. Stirring was continued at room temperature for 48 hours to ensure complete reaction. Upon completion of the reaction, the white solid product was collected by vacuum filtration and washed with methanol. The resulting solid was suspended in water (300 mL) and stirred for 3 hours to remove soluble impurities. The solid was collected again and dried overnight in a vacuum oven at 40 °C to give a final 195 g (71% yield) of 2-(3-oxocyclopentyl)isoindole-1,3-dione as a white solid. The product was characterized by 1H NMR (DMSO-d6): δ 7.85-7.77 (m, 4H), 4.90 (m, 1H), 2.67 (ddd, 1H, J = 18.5, 6.2, 1.3 Hz), 2.54 (dd, 1H, J = 18.5, 9.2 Hz), 2.45 (m, 1H), 2.32-2.21 (m, 3H); Mass spectrum (m/z): 230 (M + 1, weak).
References
[1] Patent: US2010/69404, 2010, A1. Location in patent: Page/Page column 12
[2] Patent: US2011/118326, 2011, A1. Location in patent: Page/Page column 8
[3] Patent: WO2009/140448, 2009, A1. Location in patent: Page/Page column 28-20
[4] Patent: WO2017/35357, 2017, A1. Location in patent: Paragraph 0603
[5] Patent: WO2017/35353, 2017, A1. Location in patent: Paragraph 0745
