To a solution of 1,3-benzodioxol-5-ol (9.63 g, 69.7 mmol) in anhydrous tetrahydrofuran (200 mL) was added dropwise a solution of isopropyl magnesium chloride (92.9 mmol, 46.5 mL, 2.0 M solution in tetrahydrofuran) over 30 min at 0° C. 7-Trifluoromethylisatin (4.00 g, 22.0 mmol) was added in one portion. The reaction mixture was stirred at ambient temperature for 4 h and the reaction was quenched by the addition of 10% aqueous hydrochloric acid (25.0 mL) and the mixture was concentrated in vacuo to dryness. The residue was diluted with ethyl acetate (200 mL), washed with saturated ammonium chloride (3×30.0 mL), brine (3×30.0 mL), dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated in vacuo to dryness. The residue was triturated with hot diethyl ether to afford 3-hydroxy-3-(6-hydroxy-1,3-benzodioxol-5-yl)-7-(trifluoromethyl)-1,3-dihydro-2H-indol-2-one (13.6 g, 83%): 1H NMR (300 MHz, DMSO-d6) δ 10.65 (s, 1H), 9.21 (s, 1H), 7.38 (d, J=7.8 Hz, 1H), 7.22 (s, 1H), 7.07 (d, J=7.2 Hz, 1H), 6.95 (dd, J=7.7, 7.7 Hz, 1H), 6.57 (s, 1H), 6.17 (s, 1H), 5.89 (d, J=6.2 Hz, 2H); 13C NMR (75 MHz, DMSO-d6) δ 179.2, 148.6, 147.3, 141.0, 139.9, 135.7, 127.9, 125.3, 124.3, 121.7, 119.8, 110.1, 107.2, 101.2, 97.7, 73.9; MS (ES−) m/z 352.2 (M−1).
