Synthesis
Example 3 Synthesis of 4-benzyloxy-2-(2,6-dioxo-piperidin-3-yl)-isoindole-1,3-dione Step 1: [169] 3-Hydroxyphthalic anhydride (4.96 g, 30.2 mmol) was dissolved in methanol (60 mL) and refluxed for 3 hours. After the reaction was completed, it was cooled to room temperature and the solvent was removed by vacuum evaporation. The residue was suspended with sodium bicarbonate (7.11 g, 84.6 mmol) in DMF (40 mL), iodomethane (4.53 mL, 72.5 mmol) was added, and the reaction mixture was heated at 50 °C for 2 hours. At the end of the reaction, the solvent was removed under vacuum and the residue was partitioned with ethyl acetate (120 mL) and water (100 mL). The organic phase was washed with water (2 x 100 mL) and evaporated. The residue was purified by silica gel column chromatography using hexane-ethyl acetate (6:4) as eluent to afford dimethyl 3-hydroxyphthalate (4.83 g, 76% yield).1H NMR (CDCl3) δ 3.89 (s, 3H), 3.92 (s, 3H), 6.97 (dd, J=7.9 Hz, J=0.9 Hz, 1H), 7.09 ( dd, J=8.6 Hz, J=1.0 Hz, 1H), 7.46 (t, J=8.3 Hz, 1H), 10.58 (s, 1H).
Example 24 Synthesis of 2-(2,6-dioxo-piperidin-3-yl)-4-(4-methoxy-benzyloxy)-isoindole-1,3-dione Step 1: [232] 3-Hydroxyphthalic anhydride (20.5 g, 125 mmol) was dissolved in methanol (100 mL), and heated to reflux for 3 hours. After the reaction was completed, the solvent was removed by vacuum evaporation and the residue was suspended with sodium bicarbonate (29.4 g, 350 mmol) in DMF (250 mL), iodomethane (19 mL, 300 mmol) was added, and the reaction mixture was heated at 55 °C for 4 hours. At the end of the reaction, it was cooled to room temperature, the solvent was removed by vacuum evaporation, and the residue was partitioned with water (200 mL) and ethyl acetate (200 mL). The organic layer was washed with water (2 x 200 mL), dried and concentrated in vacuum, and purified by fast column chromatography (silica gel, EtOAc/hexane, 0% gradient to 100% for 30 min) to afford dimethyl 3-hydroxyphthalate (20.2 g, 77% yield). The product could be used in the next step without further purification.
