To a solution of 2-indolone (5 g, 37.55 mmol) and lithium chloride (5.6 g, 131.4 mmol) in tetrahydrofuran (100 mL) was added n-butyllithium (2.5 M, 30 mL) dropwise at -78 °C. The reaction mixture was stirred at -78 °C for 20 min, followed by the addition of iodomethane (4.8 mL, 75.1 mmol). The reaction system was warmed to 25 °C and stirred overnight. Upon completion of the reaction, the reaction was quenched with saturated aqueous ammonium chloride solution (100 mL) and extracted with ethyl acetate (100 mL x 3). The organic phases were combined, washed sequentially with water (100 mL) and saturated saline (100 mL), dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (petroleum ether/ethyl acetate, 8:1, v/v) to afford 1,2-dihydro-3,3-dimethyl-2-oxo-3H-indole as a white solid (2.92 g, 48.3% yield). Mass spectrum (ESI, positive ion mode) m/z: 162 [M+H]+; NMR hydrogen spectrum (CDCl3) δ (ppm): 9.23 (s, 1H), 7.21-7.18 (m, 2H), 7.04 (t, 1H), 6.96 (d, 1H), 1.41 (s, 6H).
