Indole → 1-Methylindole

Participants

Reaction Steps

To a solution of indole product from Example 38, Step F (182 mg, 0.694 mmol) and dimethyl oxalate (90 mg, 0.76 mmol) in DMF (5 mL), potassium tert-butoxide (86 mg, 0.76 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, Example 37, as a white solid (180 mg, 92%): mp 106-108° C.; 1H NMR (500 MHz, CDCl3) δ 7.19-7.28 (m, 5H), 7.05 (d, J=8.5 Hz, 1H), 7.03 (d, J=3.0 Hz, 1H), 6.73 (d, J=8.5 Hz, 1H), 6.41 (dd, J=3.0, <1 Hz, 1H), 4.37 (t, J=6.3 Hz, 1H), 4.00 (d, J=15.1 Hz, 1H), 3.85 (d, J=15.1 Hz, 1H), 3.75 (s, 3H), 3.08 (dd, J=11.4, 5.4 Hz, 1H), 2.66 (dd, J=11.4, 8.1 Hz, 1H), 2.50 (s, 3H); CI MS m/z=277 [C19H20N2+H]+; IR (KBr) 3050, 2939, 2783, 1487, 1451 cm−1; Anal. Calcd for C19H20N2-0.1 H2O: C, 82.04; H, 7.32; N, 10.07. Found: C, 82.06; H, 7.50; N, 9.85.

Provenance & Evidence