To a solution of 3-(5-fluoro-2-hydroxyphenyl)-1-pentyl-1,3-dihydro-2H-indol-2-one (2.10 g, 6.70 mmol) in THF (20.0 mL) were added paraformaldehyde (1.76 g, 58.8 mmol) and lithium diisopropylamide (7.35 mL, 2.0 M in THF, 14.7 mmol) at 0° C. The reaction mixture was stirred at 0° C. for 2 hrs followed by the addition of ammonium chloride solution (10.0 mL) and ethyl acetate (100 mL). The organic layer was washed with water and brine, dried over Na2SO4 and filtered. The filtrate was concentrated in vacuo to dryness to give the title compound: 1H NMR (300 MHz, CDCl3) δ 9.55-9.10 (br, 1H), 7.53-6.86 (m, 6H), 6.57-6.49 (m, 1H), 4.74-4.30 (br, 1H), 4.18-4.07 (m, 2H), 3.79-3.60 (m, 2H), 1.77-1.61 (m, 2H), 1.41-1.24 (m, 4H), 0.87 (t, 3H); MS (ES+) m/z 326 (M−17), 366 (M+23).
