Synthesis of 3-Benzyloxindole Derivative

9 (8.30 g, 36.2 mmol) was dissolved in DMF (10 ml) and added to a heterogenous mixture of isatin (5.86 g, 39.9 mmol) and K₂CO₃ (11.02 g, 79.7 mmol) in DMF (25 mL). The reaction mixture was stirred at room temperature for 4 hr, quenched with dH₂O (100 mL), and extracted with EA (2 × 100 mL). The combined organic extracts were washed with brine (100 mL), dried over anhydrous Na₂SO₄, and concentrated in vacuo to afford a red crystal. The residue was dissolved in MeOH (60 mL), then K₂CO₃ (10.02 g, 72.5 mmol) was added and stirred at room temperature for 2 hr. The reaction mixture was quenched with 1N HCl (50 mL), extracted with EA (2 × 100 mL), dried over anhydrous Na₂SO₄, concentrated in vacuo, and purified by flash chromatography (SiO2, DCM/EA;0–40%) to afford 10 as a red crystal (2.30 g, 25.1%). ¹H NMR (DMSO-d₆, 600 MHz): δ 9.41 (1H, s); 7.59–7.54 (2H, m); 7.23–7.21 (2H, d, J = 8.74 Hz); 7.11–7.08 (1H, m); 7.00–6.99 (1H, d, J = 7.87 Hz); 6.71–6.70 (2H, d, J = 8.74 Hz); 4.77 (2H, s). ¹³C NMR (DMSO-d₆, 600 MHz): δ 183.7, 158.6, 157.3, 150.8, 138.4, 129.3, 125.9, 124.9, 123.7, 118.1, 115.8, 111.6, 42.9. Measured purity by elemental analysis: calculated for (C: 71.14, H: 4.38, N: 5.53); found (C: 70.65, H: 4.26, N: 5.54). HRMS: calculated for (C₁₅H₁₁NO₃): 253.0739, found 276.0641 (M + Na⁺).