A facile synthesis of 6,6'- and 5,5'-dihalogenoindigos

摘要

Our convenient synthetic method for Tyrian purple was applied to syntheses of 6,6'- and 5,5'- dihalogenoindigos. The dihalogenoindigos were easily obtained by three steps of reactions from the commercially available haloindoles. lodination of the haloindoles, followed by acetoxylation with silver acetate in acetic acid, afforded 5- or 6-halo-3-acetoxyindoles, whose alkaline hydrolysis accompanying air oxidation gave the corresponding dihalogenoindigos. The first ~1H NMR spectrum of 6,6'-difluoroindigo was taken in dimethyl sulfoxide.