Indole → 1-Methylindole

To a solution of the indole product from Example 52 (160 mg, 0.539 mmol) and dimethyl oxalate (70 mg, 0.59 mmol) in DMF (5 mL), potassium tert-butoxide (66 mg, 0.59 mmol) was added in one portion at room temperature under nitrogen. The reaction mixture was warmed to reflux under nitrogen for 30 min and then was cooled to room temperature. The mixture was diluted with water (50 mL) and extracted (3×) with methylene chloride. The combined organic layers were washed with brine, dried over Na2SO4, filtered and concentrated in vacuo. The residue was purified by chromatography (SiO2, EtOAc/hexanes, 1:1) to afford the N-methyl indole product as a white solid (160 mg, 96%): mp 90-92° C.; 1H NMR (300 MHz, CDCl3) δ 7.03-7.23 (m, 6H), 6.71 (d, J=8.5 Hz, 1H), 6.41 (dd, J=3.0, <1 Hz, 1H), 4.33 (t, J=7.5, 5.0 Hz, 1H), 3.94 (d, J=15.1 Hz, 1H), 3.88 (d, J=15.1 Hz, 1H), 3.74 (s, 3H), 3.01 (dd, J=11.4, 5.0 Hz, 1H), 2.66 (dd, J=11.4, 7.5 Hz, 1H), 2.48 (s, 3H); CI MS m/z=311 [C19H19ClN2+H]+; IR (KBr) 2937, 2766, 1594, 1497, 1265 cm−1; Anal. Calcd for C19H19ClN2-0.l H2O: C, 73.00; H, 6.19; N, 8.96. Found: C, 72.78; H, 6.09; N, 8.78.