Regioselective Synthesis of Chromeno[4′,3′:4,5]pyrano[3,2-c][1,8]naphthyridin-13-one Derivatives by Domino Knoevenagel-Hetero-Diels-Alder Reactions - Majumdar, K. C.; Taher, Abu; Ponra, Sudipta (Synthesis, 2011)