Straightforward selective preparation of nitro- or amino-indoles from 2-halonitroanilines and alkynes. First synthesis of 7-amino-5-nitroindoles

A one-pot selective synthesis of 2-substituted C5-, C6-, and C7-nitro- or amino-indoles has been developed from 2-halonitroanilines. These two types of nitrogen-substituted indoles have been selectively obtained by only varying the solvent used in the tandem Sonogashira coupling/heteroannulation reaction. Moreover, from commercially available 2-bromo-4,6-dinitroaniline an unprecedented in situ selective reduction of one of the nitro groups has allowed the synthesis of new 7-amino-5-nitro-2-substituted indoles.