A rapid access to indolo[2,1-a]pyrrolo[4′,3′:4,5]pyrano[5,6-c]coumarin/[6,5-c]chromone derivatives by domino Knoevenagal intramolecular hetero Diels-Alder reactions

Knoevenagal condensation of indole-2-carbaldehyde containing an internal dienophile with coumarins, followed by domino intramolecular hetero Diels-Alder reaction, provides polycyclic heterocycles. Different approaches for stereo- and chemoselective synthesis of indolo[2,1-a]pyrrolo[4′,3′:4,5]pyrano[5,6-c]coumarin and indolo[2,1-a]pyrrolo[4′,3′:4,5]pyrano[6,5-c]chromone derivatives are described.