Chemoselective synthesis of multisubstituted pyrrolo[3,4-b]pyridine-2,5,7(6H)-trione through a cascade reaction

A simple and efficient protocol for direct synthesis of multisubstituted 6-alkyl-4-chromenyl-1-aryl-3,4-dihydro-1H-pyrrolo[3,4-b]pyridine-2,5,7(6H)-trione derivatives is presented by a cascade reaction of 3-formylchromones, Meldrum’s acid and α-aminomaleimides as readily accessible starting materials. In this chemoselective, metal catalyst-free approach Michael addition/intramolecular cyclization and elimination of acetone and carbon dioxide occur consecutively. The significant advantages of this strategy are creating a C–N and a C–C bond, short reaction times, excellent yields (68–80%), and a metal-free catalyst.