Synthesis of 6-bromo-2-arylindoles using 2-iodobenzoic acid as precursor

The synthesis of 6-bromo-2-arylindoles starting from readily available 2-iodobenzoic acid is presented. Regioselective bromination of the latter was followed by Curtius rearrangement and trapping of the isocyanate with benzyl alcohol led to the benzyl carbamate of 2-iodo-5-bromoaniline. Chemoselective Sonogashira coupling of this compound with arylacetylenes followed by TBAF induced 5-endo-dig cyclization gave the desired bromo indoles. The method allows selective introduction of a bromine atom at the indole C-6 position.