Reaction Steps
To a stirred suspension of 4-aminomethyl-2-(2,6-dioxo-piperidin-3-yl)-isoindole-1,3-dione hydrochloride (0.7 g, 2.2 mmol) in CH3CN (60 ml), was added 1,8-diazabicyclo[5.4.0]undec-7-ene (0.8 g, 5.4 mmol). After stirring for 10 minutes, 1-hydroxybenzenetriazole (0.35 g, 2.6 mmol) and 2-benzofuran carboxylic acid (0.39 g, 2.4 mmol) were added. To the reaction, was then added 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (0.62 g, 3.2 mmol), and the resulting mixture was stirred at room temperature overnight. The reaction mixture was then concentrated in vacuo, and the residue was dissolved in CH2Cl2 (50 mL). The CH2Cl2 solution was washed with water (2×30 mL) and brine (30 mL), and dried over MgSO4. Solvent was removed in vacuo, and the resulting oil was purified by ISCO silica gel flash chromatography (eluent: 30% EtOAc in CH2Cl2 for 10 min, then 40% EtOAc in CH2Cl2 for 10 min) to afford benzofuran-2-carboxylic acid [2-(2,6-dioxo-piperidin-3-yl)-1,3-dioxo-2,3-dihydro-1H-isoindol-4-ylmethyl]-amide as a white solid (0.59 g, 63%): mp, 292-295° C.; HPLC: Waters Symmetry C-18, 3.9×150 mm, 5 micro, 1 mL/min, 240 nm, 40/60 (CH3CN/H2O): tR=4.3 min. (98%); 1H NMR (DMSO-d6): δ 2.09-2.10 (m, 1H), 2.55-2.65 (m, 2H), 2.84-2.93 (m, 1H), 4.97 (d, J=6.0 Hz, 2H), 5.15-5.21 (dd, J=5, 12 Hz, 1H), 7.33-7.84 (m, 8H), 9.40 (t, J=6 Hz, 1H), 11.15 (s, 1H). 13C NMR (DMSO-d6) δ: 21.97, 30.92, 37.90, 48.87, 109.90, 111.79, 121.95, 122.81, 123.74, 126.96, 127.09, 127.15, 131.54, 133.02, 134.83, 138.71, 148.71, 154.27, 158.52, 166.94, 167.51, 169.82, 172.74. Anal Calcd for C23H17N3O6+0.2H2O: C, 63.51; H, 4.03; N, 9.66. Found: C, 63.45; H, 3.76; N, 9.52.
