Example 1 Synthesis of 3-iodo-1H-indole-5-carbonitrile (V)
1H-indole-5-carbonitrile (5 g, 35.2 mmol), potassium hydroxide (KOH, 7.90 g, 141 mmol) and iodine (I2, 8.90 g, 35.2 mmol) were suspended in 25 mL of N,N-dimethylformamide (DMF) under inert atmosphere. The reaction mixture was stirred at 10 °C for 30 min under light protection, followed by quenching the reaction with 0.1 M sodium thiosulfate (Na2S2O3) solution (150 mL). The resulting suspension was continued to be stirred for 30 min, then filtered, and the collected solid was washed with deionized water and dried under vacuum at 50 °C to constant weight. The final white solid product 3-iodo-1H-indole-5-carbonitrile (V) (9.0 g) was obtained in 95% yield.
1H-NMR (400 MHz, CDCl3) data: δ 8.78 (1H, broad peak); 7.80 (1H, single peak); 7.46-7.40 (3H, multiple peaks).
