3-Acetylindole (97%, Ark Pharm)

3-Acetylindole (10.007 g, 63.262 mmol, 1 eq.), 4-(N,N-dimethylamino)pyridine (1.542 g, 12.62 mmol, 0.2 eq.) and triethylamine (26.3 mL, 188 mmol, 3 eq.) were dissolved in dichloromethane (500 mL) and stirred at room temperature for 30 minutes. Trimethylacetyl chloride (10.8 mL, 88.0 mmol, 1.4 eq.) was added and the solution was stirred at room temperature for 4 days. The reaction mixture was washed with water (1 x 100 ml) and dried over magnesium sulfate. The drying agent was filtered off and the solvent was removed under reduced pressure. The crude product was purified by column chromatography (1:4 ethyl acetate:hexane on SiO₂), giving white crystals (13.036 g. 86%).

R_f = 0.17 (SiO₂, 1:4 EtOAc:hexanes)

M.p. 118-120 °C

¹H NMR (500 MHz, CDCl₃) δ 8.46 (d, J = 7.9, 1H), 8.35 (s, 1H), 8.34 (d, J = 6.4, 1H), 7.44-7.38 (m, 2H), 2.61 (s, 3H), 1.58 (s, 9H)

¹³C NMR (126 MHz, CDCl₃) δ 193.5, 177.0, 137.3, 131.4, 126.12, 126.09, 125.0, 122.0, 121.1, 116.8, 41.6, 28.7, 27.9;

IR (film, cm^-1) 3054.4, 2986.3, 1710.7, 1667.1, 1547.6, 1478.4, 1447.1, 1349.4, 1319.3, 1265.4, 1193.8, 1174.9, 1149.5, 1137.1, 1009.4, 897.5, 740.7, 705.0, 645.1 cm^-1

MS (EI, m/z) [M]⁺ calculated for C₁₅H₁₇N₁O₂⁺ requires 243.1254, found 243.1252.

Anal. Calcd for C₁₅H₁₇N₁O₂: C, 74.05; H, 7.04; N, 5.76. Found: C, 74.18; H, 7.16; N, 5.76