827-01-0

17422-32-1

827-01-0

The general procedure for the synthesis of 5-chloroindole-3-carbaldehyde from 5-chloroindole was as follows: phosphorus trichloride (4.6 mL, 49 mmol) was added slowly and dropwise to stirred dimethylformamide (20 mL) at 0 °C. After the dropwise addition, the reaction mixture was continued to be stirred for 10 minutes. Subsequently, a solution of 5-chloroindole (5.0 g, 33 mmol) dissolved in dimethylformamide (5 mL) was added slowly dropwise. After completion of the dropwise addition, the reaction mixture was heated to 40°C and kept at this temperature for 45 minutes. After completion of the reaction, the mixture was cooled to room temperature and then treated with a solution of sodium hydroxide (5.9 g, 148 mmol) in water (20 mL). Next, the mixture was heated to 50°C, held for 10 minutes and then cooled to room temperature. The reaction mixture was poured into crushed ice (100 mL) and the precipitate was collected by filtration. Finally, the filter cake was recrystallized by methanol to give the white solid product 5-chloroindole-3-carboxaldehyde (3.5 g, 59% yield) with a melting point of 215-216 °C. Elemental analysis measured values: C, 60.13; H, 3.40; N, 7.75%. Consistent with theoretical values (C9H6ClNO): C, 60.19; H, 3.37; N, 7.79%.