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

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.

Automated summary

A direct and efficient method for the synthesis of 3-chloro-2-formylindoles using SO2ClF is reported. This tandem system involves electrophilic chlorination, deprotonation, nucleophilic addition, and oxidation. Under mild conditions, various 2-methylindoles can be successfully transformed into 2,3-difunctionalized indoles in good yields.