General procedure for the synthesis of 4-amino-N-methylindole from 1-methyl-4-nitro-1H-indole: Reduced iron powder (3.36 g, 60 mmol) was added batchwise to a boiling mixture containing 1-methyl-4-nitro-1H-indole (40 mmol), concentrated hydrochloric acid (5 mL) and ethanol (100 mL). The resulting suspension was refluxed for 1 h. The reaction process was monitored by thin layer chromatography (TLC). Upon completion of the reaction, the reaction mixture was neutralized with ammonia, filtered to remove iron residue, and washed with ethanol (30 mL). The filtrate was evaporated and concentrated, then diluted with ethyl acetate (100 mL). The organic phase was washed sequentially with brine (25 mL) and water (2 x 50 mL), dried with magnesium sulfate, and the solvent was evaporated to give the residue 1-methyl-1H-indol-4-ylamine (7). The product was a gray solid with a melting point of 95-96 °C in 85% yield.1H NMR (300 MHz, CDCl3) δ 7.02 (t, 1H, J = 7.8 Hz, H-6), 6.86 (d, 1H, J = 3.3 Hz, H-2), 6.74 (d, 1H, J = 8.7 Hz, H-5), 6.33 (d, 1H, J = 8.7 Hz , H-7), 6.32 (d, 1H, J = 3.3 Hz, H-3), 3.82 (br s, 2H, NH2-4), 3.61 (s, 3H, CH3-1). Calculated values for elemental analysis (C9H10N2): C, 73.94; H, 6.89; N, 19.16; measured values: C, 73.80; H, 6.80; N, 19.30%.
