In a 100 mL stainless steel autoclave, 1.09 g (5.1 mmol) of 5-chloro-2-nitrophenylacetone and 72 mg (4 mol%) of cyclopentadienyl ferric dicarbonyl (dimer) were added as a catalyst and 40 g of toluene as a solvent, and the system was protected by nitrogen. After displacing the atmosphere in the reactor three times (10 kgf/cm2 nitrogen each time), carbon monoxide gas was injected to a pressure of 30 kgf/cm2. The reaction mixture was stirred at 120 °C for 5 h. The reaction was completed by cooling to room temperature. Upon completion of the reaction, it was cooled to room temperature and the complete conversion of 5-chloro-2-nitrophenylacetone was confirmed by liquid chromatography analysis. Subsequently, the reaction mixture was post-treated and purified by silica gel column chromatographic separation to afford 0.79 g (94.0% yield) of the target product 5-chloro-2-methylindole.
