To a beaker immersed in an ice bath, 7 mL of acetic acid, 3.7 mL of 35% formaldehyde and 6.1 mL of 40% dimethylamine are added. Then 5 g of indole is added to the solution and stirred until clear, after which stirred for 2 h at room temperature. Subsequently, the solution is poured into a solution prepared from 5 g of NaOH in 150 mL of water. The mixture is filtered, washed 3 times with water and recrystallized from hot acetone.
The solution after the addition of the indole
Stirring the solution at room temperature
The basic mixture
Filtration of the crude product
The recrystallized product