7-fluoro-1-(3-fluorobenzyl)-3,3-dimethyl-1,3-dihydro-2H-indol-2-one (1.01 g, 3.5 mmol) was dissolved in tetrahydrofuran and cooled to −78° C. n-Butyl lithium (2.5 M in hexane, 1.55 mL, 3.97 mmol) was added dropwise and the mixture was warmed to 0° C. (2-Bromoethoxy)-tert-butyldimethylsilane (1.14 mL, 5.25 mmol) was added and the mixture was allowed to warm to 25° C. The mixture was stirred for 16 hours then quenched with saturated aqueous ammonium chloride, diluted with ether, washed with water, and saturated brine. The organic layer was separated, dried over anhydrous magnesium sulfate, filtered, and concentrated in vacuo. The crude product was purified via Isco chromatography (Redisep, silica, gradient 0-10% ethyl acetate in hexane) to afford 0.8 g (55%) 1-[3-{[tert-butyl(dimethyl)silyl]oxy}-1-(3-fluorophenyl)propyl]-7-fluoro-3,3-dimethyl-1,3-dihydro-2H-indol-2-one.
