Furonaphthoquinones are promising skeletons for anticancer drug molecules. In particular, methoxylated furonaphthoquinones are characteristic constituents of Tabebuia plants. In this research, we synthesized the furonaphthoquinones by effective one-pot cascade reactions of 3-phenyliodonio-1,2,4-trioxo-1,2,3,4-tetrahydronaphthalenides with 3-butyn-2-ol in the presence of palladium and cuprous catalysts via Sonogashira coupling and intramolecular cyclization. Furthermore, we demonstrated that the synthetic furonaphthoquinones showed moderate cytotoxicity against human leukemia U937 and HL-60 cells. Our work highlights the importance of furonaphthoquinones as antileukemic agents.