Valois-Escamilla Ismael, Alvarez-Hernandez Alejandro, Rangel-Ramos Luis Felipe, Suárez-Castillo Oscar Rodolfo, Ayala-Mata Francisco, Zepeda-Vallejo Gerardo . Synthesis of 6-bromo-2-arylindoles using 2-iodobenzoic acid as precursor. Tetrahedron Letters 2011, 52, 3726-3728. Elsevier, Holanda. ISSN: 0040-4039 doi:10.1016/j.tetlet.2011.05.040
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.