Lithium Hydroxide → 3-[1-(Phenylsulfonyl)indolin-5-yl]acrylic Acid

1M LiOH aqueous solution (1.16 ml, 1.16 mmol) was added to a solution of 14 (0.20 g, 0.58 mmol) in dioxane (15 mL). The reaction mixture was stirred at 40° C. overnight before it was concentrated under reduced pressure. The residue was dissolved in water and concentrated HCl was added up to acidic pH to give the precipitation, which was dried by vacuum to afford 15 (0.16 g). 1H NMR (500 MHz, CD3OD): δ 2.92 (t, J=8.5 Hz, 2H), 3.96 (t, J=8.5 Hz, 2H), 6.33 (d, J=15.9 Hz, 1H), 7.38 (s, 1H), 7.41 (d, J=8.5 Hz, 1H), 7.50-7.53 (m, 2H), 7.55 (d, J=16.1 Hz, 1H), 7.58-7.64 (m, 2H), 7.82 (d, J=7.6 Hz, 2H).