SO2ClF-promoted chlorination-oxidation of 2-methylindoles: a one-step synthetic method to access 2,3-difunctionalized indoles

Abstract

A direct and one-step method for the synthesis of 3-chloro-2-formylindoles with SO₂ClF is reported. This tandem system consists of double electrophilic chlorination and deprotonation, nucleophilic addition of H₂O to the resulting enamine intermediate, and subsequent oxidation. Various readily available 2-methylindoles were applicable to this protocol under mild conditions, furnishing 2,3-difunctionalized indoles in good to high yields.