Synthetic experiment Typical experimental procedure (3a) Bis(indol-3-yl)(phenyl)methane [1]. To a mixture of CuBr (3.6 mg, 0.025 mmol) and indole (59 mg, 0.5 mmol), N-benzyl-piperidine (88 mg, 0.5 mmol) was added. Then tert-butyl hydroperoxide (0.6 mmol, 5-6 M in decane) was added dropwise into the mixture under nitrogen at room temperature. The resulting mixture was stirred at 80 °C for 18 h. Then, the cooled reaction mixture was dissolved in water (5 mL) and extracted with CH 2 Cl 2 (3×5 mL).

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... The combined organic layer was dried with anhydrous MgSO 4 , and the product was further purified by silica gel column chromatography and eluted with cyclohexane and petroleum ether mixture to afford the product. Pink solid; mp 122-124 °C; 1 H NMR (400 MHz, CDCl 3 ): δ 7.91 (br s, 2H, NH), 7.34-7.39 (m, 6H), 7.25-7.29 (m, 2H), 7.14-7.17 (m, 3H), 7.00 (t, J = 6.8 Hz, 2H), 6.66 (s, 2H), 5.88 (s, 1H, Ar-CH); 13 C NMR (50 MHz, [3b] Bis(6-chloroindol-3-yl)(phenyl)methane. Pink solid; mp 128-130°C; 1 H NMR (200 MHz, CDCl 3 ): δ 7.96 (br s, 2H, NH), 7.34 (s, 2H), 7.28-7.30 (m, 4H), 7.23-7.26 (m, 3H), 6.96 (d, J = 8.4 Hz, 2H), 6.61 (s, 2H), 5.78 (s, 1H, Ar-CH); 13 C NMR (50 MHz,