To a stirred solution of 3,4-dimethylphenol (2.50 g, 20.5 mmol) in tetrahydrofuran (100 mL) was added isopropylmagnesium chloride (10.2 mL, 2.0 M tetrahydrofuran solution, 20.40 mmol) at 0° C. The mixture was allowed to stir for 1 h at 0° C., then the solvent was removed in vacuo. Dichloromethane (200 mL) was added, followed by the addition of 1-(diphenylmethyl)-1H-indole-2,3-dione (5.00 g, 15.95 mmol). The mixture was stirred for 54 h at ambient temperature, quenched with saturated ammonium chloride solution. The organic layer was washed with water, brine, dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated in vacuo, the residue was purified by column chromatography to give 1-(diphenylmethyl)-3-hydroxy-3-(2-hydroxy-4,5-dimethylphenyl)-1,3-dihydro-2H-indol-2-one (5.10 g, 73%): 1H NMR (300 MHz, CDCl3) δ7.49-7.45 (m, 1H), 7.35-7.27 (m, 10H), 7.08-7.04 (m, 2H), 6.93 (s, 1H), 6.81-6.75 (m, 1H), 6.52 (s, 1H), 6.49-6.46 (m, 1H), 2.15 (s, 3H), 2.02 (s, 3H); MS (ES+) m/z 418.1 (M−17).
