An alternative approach to the synthesis of 5H-chromeno[4,3-b]pyridin-5-one system using the cleavage of 5H,9H-pyrano[2',3':5,6]chromeno[4,3-b]pyridine-5,9-diones with binucleophiles

Hantzsch reaction has been successfully employed for a one-step assembling of pyranopyridine fragment to produce 5De,9De-pyrano[2',3':5,6]- chromeno[4,3-b]pyridine-5,9-diones which upon treatment with binucleophiles undergo chemoselective gamma-pyrone ring opening with the concomitant recyclization to give five-membered cycles, providing a concise route to 6-pyrazolyl(isoxazolyl)-5H-chromeno[4,3-b]- pyridin-5-ones.