To a stirred solution of oxindole (555 mg, 4.17 mmol) in anhydrous dimethoxyethane (20 ml) under nitrogen was added 2.5M n-BuLi solution in hexane (3.67 ml, 9.17 mmol), and the resulting mixture was stirred at room temperature for 10 minutes, followed by the addition of 5-(2,4-dimethoxy-benzylamino)-3H-isobenzofuran-1-one (1.0 g, 3.34 mmol). After stirred at room temperature for 2.5 hours the mixture was poured into 1M HCl aqueous solution (100 ml). The resulting solid was separated, washed with water, and dried under vacuum to afford a crude product. Trituration of the crude product with MeOH produced 3-[5-(2,4-dimethoxy-benzylamino)-3H-isobenzofuran-1-ylidene]-1,3-dihydro-indol-2-one as a yellow solid (630 mg, 46%).
