SYNTHESIS OF INDOLES BY DEHYDRATION OF INDOLINES

摘要

PCT No. PCT/EP93/00261 Sec. 371 Date Aug. 25, 1994 Sec. 102(e) Date Aug. 25, 1994 PCT Filed Feb. 4, 1993 PCT Pub. No. WO93/16076 PCT Pub. Date Aug. 19, 1993. IMAGE (I) By dehydrating indolines or their salts, the corresponding indoles having formula (I) are obtained. In the formula, R1 and R3 represent independently from each other hydrogen or alkyl groups with 1 to 4 C atoms, R2 stands for hydrogen, a methyl or a carboxyl group, R4 and R5 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 R4 and R5 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.