| abstract |
By dehydration of indolines or their salts, the corresponding indoles of formula (I) are obtained in which R1 and R3 independently represent hydrogen or alkyl groups having 1 to 4 atoms of C, R2 represents hydrogen, a methyl group or a carboxyl group, R4 or R5 represent, independently of one another, hydrogen, amino groups, hydroxy groups, alkyl groups having 1 to 4 C atoms or alkoxy groups having 1 to 4 C atoms, or alternatively in the case where R4 and R5 are linked to neighboring C atoms, these two residues can also jointly represent an alkylene dioxy group having 1 to 4 C atoms. to obtain high yields of very pure indoles. |