General procedure for the synthesis of 2,6-dimethyl-1H-indole (VI) from acetone and 3-methylaniline: in a reaction tube, 3-methylaniline (5.00 g, 0.046 mol), anhydrous copper(II) acetate (18.6 g, 0.093 mol), and palladium(II) acetate (0.208 g, 0.930 mmol) were dissolved in a mixture of acetone (25 mL) and dimethyl sulfoxide (25 mL) in a mixed solution and the reaction was heated at 90 °C for 18 hours. After completion of the reaction, it was cooled to room temperature and the reaction mixture was poured into cold water and extracted with ethyl acetate (2 x 250 mL). The organic layer was separated and washed sequentially with water and brine. The organic layer was dried with anhydrous sodium sulfate and concentrated under reduced pressure to give the crude product. The crude product was purified by silica gel column chromatography (100-200 mesh) with gradient elution of ethyl acetate/hexane to afford the target compound VI (1.0 g, 15% yield).1H NMR (400 MHz, CDCl3): δ 10.70 (s, 1H), 7.23 (d, J = 8.00 Hz, 1H), 7.02 (s, 1H), 6.72 (d J = 7.8 Hz, 1H), 6.01 (s, 1H), 2.34 (s, 6H); MS (ESI, positive mode) m/z 146 ([M+H]+).
