Preparation of 2,3-Disubstituted 5-Bromo-1H-pyrrolo[2,3-b]pyridine Framework by Fischer Cyclization

Abstract A simple synthesis of some hard-to-reach heterocycles containing 2,3-disubstituted 5-bromo-1 H -pyrrolo[2,3- b ]pyridine framework by Fisсher indole cyclization in polyphosphoric acid has been developed. A particularly valuable feature of this synthetic route is the possibility to build a 5-bromo-7-azaindole scaffold with alkyl or aryl substituents at positions 2 and 3 from available starting materials.