Example 15 General procedure for the synthesis of 5-bromo-3-(2,4-dichlorobenzoyl)-1-ethyl-1H-indole:
1a) Synthesis of 5-bromo-1-ethyl-1H-indole
In 75 mL of anhydrous dimethylformamide (DMF), 3.06 g (76.5 mmol, 60% mineral oil suspension) of sodium hydride (NaH) was added. The mixture was stirred and heated to 80 °C. Subsequently, 5.0 g (25.5 mmol) of 5-bromo-1H-indole was slowly added. The heating was continued for 30 minutes (until the hydrogen gas stopped being released). The reaction mixture was cooled to room temperature and 4 mL (51 mmol) of ethyl iodide was added. The mixture was again heated to 80 °C and the reaction was maintained for 2 hours. Upon completion of the reaction, hydrolysis was carried out. The reaction mixture was extracted with dichloromethane and the organic phase was dried with anhydrous sodium sulfate and concentrated. The concentrated residue was purified by silica gel column chromatography using dichloromethane as eluent to give the target product (Int.49). Yield: 89% as a yellow oil.
