Synthesis of 5-oxo-4,5,6,7-tetrahydro-1H-pyrrolo-[3,2-b]pyridine-3-carboxylic acids by three-component condensation of 3-aminopyrrole derivatives

5-Oxo-4,5,6,7-tetrahydro-1H-pyrrolo[3,2-b]pyridine-3-carboxylic acids were prepared by three-component condensation of 3-aminopyrroles, (het)aromatic aldehydes and Meldrum's acid. The labile intermediate 3-aminopyrrole derivative was generated in situ by regioselective (at 2-position) decarboxylation of 3-aminopyrrole-2,4-dicarboxylic acid.