To a pale yellow solution of 4-(benzyloxy)phenol (9.01 g, 45.0 mmol) in anhydrous tetrahydrofuran (100.0 mL) was added isopropylmagnesium chloride (26.3 mL, 52.5 mmol, 2.0 M solution in tetrahydrofuran) at 0° C. The reaction solution was stirred for 0.5 h followed by the addition of 1-((5-chlorothiophen-2-yl)methyl)indoline-2,3-dione (8.31 g, 30.0 mmol) in portions. The reaction mixture was stirred for 16 h at ambient temperature. The reaction was quenched by the addition of saturated ammonium chloride solution (50.0 mL) and concentrated in vacuo to dryness. The residue was diluted with ethyl acetate (100 mL), washed with saturated ammonium chloride solution (2×25.0 mL), brine (2×25 mL), dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated in vacuo to dryness. The residue was purified by column chromatography with ethyl acetate to afford 3-[5-(benzyloxy)-2-hydroxyphenyl]-1-[(5-chlorothiophen-2-yl)methyl]-3-hydroxy-1,3-dihydro-2H-indol-2-one (4.90 g, 28%) as a colourless solid: mp 174-175° C.; 1H NMR (300 MHz, CDCl3) δ8.45 (br, 1H), 7.40-7.27 (m, 7H), 7.14 (dd, J=7.5, 7.5 Hz, 1H), 6.92 (d, J=2.9 Hz, 1H), 6.89 (s, 1H), 6.83 (d, J=2.9 Hz, 1H), 6.79 (d, J=3.7 Hz, 1H), 6.70 (d, J=3.7 Hz, 1H), 6.43 (d, J=2.9 Hz, 1H), 4.86 (ABq, 2H), 4.84 (s, 2H); 13C NMR (75 MHz, CDCl3) δ 178.3, 152.6, 149.790, 141.7, 136.8, 135.8, 130.4, 130.1, 129.1, 128.6, 127.9, 127.6, 126.3, 126.2, 126.0, 125.9, 124.3, 120.2, 116.3, 114.4, 109.6, 79.1, 70.6, 39.2; MS (ES+) m/z 478.2 (M−1), 476.2 (M−1).
