3.2.2. Synthesis Method of Intermediate II

Under the protection of inert gas, intermediate I (2.5 mmol) was dissolved in dichloromethane (5 mL) and N-chlorosuccinimide (NCS, 2.75 mmol), and N, N-dimethylpiperazine (1.25 mmol) dichloromethane (1 mL) solution was added drop-by-drop at 0 ◦C. The reaction system was stirred continuously at 0 ◦C for 2 h. Then, a mixed solution of trichloroacetic acid (0.63 mmol) and N-methylaniline (5 mmol) dichloromethane (2 mL) was added. The reaction was then heated to room temperature and stirred continuously for 3.5 h at room temperature. At the end of the reaction, the reaction mixture was washed with saturated sodium bicarbonate aqueous solution, 1N concentration of hydrochloric acid, and salt water, and then, the separated organic phase was dried by anhydrous magnesium sulfate and condensed under pressure on a rotary evaporator. Finally, the solid product was purified by column chromatography with the eluent of n-hexane/ethyl acetate (7/1), and the intermediate II was finally obtained.

### Methyl 6-chloro-2-(methyl(phenyl)amino)-1H-indole-3-carboxylate (Intermediate II)

Yield, 64%; white solid, m.p. 154–156 ◦C (DMSO); 1H NMR (400 MHz, DMSO-d6) δ 12.08 (s, 1H), 7.92 (d, J = 8.5 Hz, 1H), 7.34 (d, J = 1.9 Hz, 1H), 7.28–7.20 (m, 2H), 7.17 (d, J = 8.5 Hz, 1H), 6.86 (t, J = 7.3 Hz, 1H), 6.83–6.77 (m, 2H), 3.65 (s, 3H), 3.37 (s, 3H). 13C NMR (100 MHz, DMSO-d6) δ 163.77, 148.66, 147.76, 133.48, 129.46 (2C), 126.94, 125.51, 122.26, 121.79, 120.10, 115.75 (2C), 111.38, 97.10, 50.93, 40.15. MS-ESI *m*/*z*: calcd for C17H15ClN2O2[M + H]+: 315.0822; found: 315.1015.

#### 3.2.3. Synthesis Method of Intermediate III

An appropriate amount of diphenyl ether was added to the round bottom flask, and then, the reactor temperature was heated to about 60 ◦C, until the diphenyl ether was in the molten state, and then, intermediate II was added to the diphenyl ether. Then, the temperature increased to 250 ◦C reflux for 1–3 h, the end of the reaction, until the temperature was reduced to room temperature, and reactants were dumped into a large quantity of petroleum ether. The intermediate III was obtained by collecting precipitated precipitation.
