Synthesis of 1-Benzyl-1H-indole-3-carboxylic Acid Methyl Ester from N-Benzyl-N-phenylhydroxylamine and Methyl propiolate – DMAP as Catalyst

R.Hwu, H.V. Patel, R.J. Lin, and M.O. Gray, J. Org. Chem., 59, 1577, (1994)

1. To a solution of N-benzyl-N-phenylhydroxylamine (86.2 mg, 0.426 mmol), in THF (15.0 mL), is added 4A molecular sieves.  The reaction mixture is cooled to 0°C; DMAP (6.0 mg, 0.049 mmol) and methyl propiolate (54 mg, 0.562 mmol) are added.
2. Reaction mixture is stirred at 0° C for 1 h, then at room temperature for 48 h.
3. Ethyl acetate (5.0 mL) is added, and after filtration, the organic solution is washed with water (3 x 20 mL), brine, and then dried over magnesium sulfate.  Following filtration, the organics are concentrated under reduced pressure and the resultant oil purified by use of a chromatotron (hexanes:ethyl acetate, 7:3 as eluent) to give 1-benzyl-1H-indole-3-carboxylic acid methyl ester (95.6 mg; 82% yield) as a white solid (m.p. 67.0-67.5°C).