An improved preparation of isatins from indoles

A convenient method has been developed for the conversion of indoles into isatin derivatives in good to excellent yields. The general process utilizes our efficient one-pot method for bromination and oxidation with an N-bromosuccinimide - dimethyl sulfoxide reagent. 1-Alkyl-7-azaindoles are readily available in excellent yields from the reaction of the sodium salt of 7-azaindole with appropriate alkyl halides in dimethylacetamide. Similar reactions with 1-alkyl-5-cyanoindoles and indole gave 1-alkyl-5-cyanoisatins and isatin, respectively.