Investigation of the Bischler indole synthesis from 3,5-dimethoxyaniline

Abstract

Cyclization of the amino ketones (3a,b) derived from 3,5- dimethoxyaniline, and phenacyl bromide and 4-bromophenacyl bromide respectively, afforded 2-arylindoles (8a,b) in preference to 3-aryl- indoles(7). The 3-(4'-bromophenyl)indole (7b) was also isolated in the presence of polyphosphoric acid, but not when amine hydrochloride catalysis was employed. The structure of 2-(4'-bromophenyl)-4,6- dimethoxyindole (8b) was confirmed by X-ray diffraction studies.