Process for the preparation of indoles

摘要

A process for producing an indole which comprises reacting an aniline and a diol in the presence of a catalyst to produce a reaction mixture containing the indole, unreacted aniline and by-products, condensing the reaction mixture to obtain a liquid reaction product, recovering the unreacted aniline from the liquid reaction product, reducing the contents of specified by-products in the recovered aniline below specified levels and reutilizing the resulting recovered aniline. To reduce the contents of the specified by-products in the recovered aniline below specified levels, it is preferred to subject the liquid reaction product or an aniline fraction separated therefrom to a heat-treatment and then to distillation. In the above manner, the recovered aniline can be reutilized in the reaction without causing the activity of the catalyst to deteriorate.