A
100-ml., three-necked flask fitted with a
reflux condenser, a
magnetic stirring bar, and a
gas-inlet tube is charged with
2.34 g. (0.0200 mole) of indole (Note
1) and
15 ml. of hexamethylphosphoric triamide (Note
2) under a static atmosphere of
argon. The flask is cooled to 0° with an
ice bath, and
0.53 g. (0.022 mole) of sodium hydride is added to the stirred solution over a period of 10 minutes (Note
3). The resulting slurry is stirred for 5 hours at room temperature (Note
4) then cooled to 0° (ice bath) before
2.53 g. (2.30 ml., 0.0200 mole) of benzyl chloride (Note
5) is added as rapidly as possible to the stirred mixture. The mixture is stirred for 8–15 hours (overnight), during which time the ice in the ice bath melts, and the temperature of the reaction flask gradually rises to room temperature. The mixture is then diluted with 15 ml. of water and extracted with three
25-ml. portions of diethyl ether. The combined ethereal extracts are washed with two 40-ml. portions of water and dried with anhydrous
magnesium sulfate. After filtration the solvent is removed at reduced pressure, and
4.4 g. of crude
1-benzylindole is obtained as a liquid. After bulb-to-bulb distillation of this material in a
Kügelrohr oven [120–130° (0.0025 mm.)], crystallization of the distillate from
15 ml. of hot ethanol affords
3.46–3.61 g. (
83–87%) of
1-benzylindole. A second crop of
0.17–0.26 g. (
4–6%) is obtained on concentration of the mother liquors to 6 ml. The total yield of
1-benzylindole, m.p.
43–44°, is
3.72–3.78 g. (
90–91%) (Note
6) and (Note
7).