(CAS NO.: ), which is also known as 1H-Indole, could be produced through the following synthetic routes.

A 2-l. three-necked round-bottomed flask is fitted with a reflux condenser and a glass inlet tube connected to a cylinder of nitrogen. The third opening of the flask is closed by a stopper. The top of the condenser is connected to an air trap which consists of two 500-ml. suction flasks joined in series. The first suction flask is empty; the second contains 100 ml. of paraffin oil, and the inlet tube of this flask extends slightly below the surface of the oil.

In the reaction flask is placed 600 ml. of commercial tert-butyl alcohol, and the air in the flask is displaced by dry nitrogen gas. Then 29 g. (0.75 gram atom) of metallic potassium is added, in portions, to the alcohol. The mixture is heated on a water bath until all the potassium has dissolved, and then 68 g. (0.5 mole) of o-formotoluide is added and brought into solution. The condenser is set for distillation with a filter flask as the receiver; this flask is protected from the air by connecting it to the trap used in the initial operation. The reaction flask is surrounded by a metal bath, and the excess alcohol is removed by distillation. The residue is heated to 350–360° for about 20 minutes and then is allowed to cool in a stream of nitrogen. The residue is decomposed by addition of 300 ml. of water, and the mixture is steam-distilled to remove the indole. The distillate is extracted successively with 300 ml. and 100 ml. of ether, and the combined ether extracts are shaken with cold dilute 5% hydrochloric acid to remove small amounts of o-toluidine. The ether extract is washed with 100 ml. of water, followed by 100 ml. of 5% sodium carbonate solution, and is dried over 20 g. of sodium sulfate. The ether is removed by distillation, and the residue is distilled under reduced pressure. Indole distils at 142–144°/27 mm. (128°/10 mm.; 121°/5 mm.) as a pale yellow oil which solidifies and then melts at 52–53°. The yield is 23 g. (79%).