| abstract |
##STR1## By dehydrating indolines or their salts, the corresponding indoles having formula (I) are obtained. In the formula, R 1 and R 3 represent independently from each other hydrogen or alkyl groups with 1 to 4 C atoms, R 2 stands for hydrogen, a methyl or a carboxyl group, R 4 and R 5 represent independently from each other hydrogen, amino groups, hydroxy groups, alkyl groups with 1 to 4 C atoms or alkoxy groups with 1 to 4 C atoms, or, in case R 4 and R 5 are bound to adjacent C atoms, both residues may also represent together an alkylene dioxy group with 1 to 4 C atoms. This process allows high yields of very pure indoles to be produced. |