Abstract7‐Arylidene‐2H,6H‐naphtho[1,8‐bc]furan‐2,6‐diones3were prepared by a retro‐Diels‐Alder reaction of the corresponding dihydro 1,3‐oxazines2or in a one pot synthesis from 6‐hydroxy‐2H‐naphtho[1,8‐bc]furan‐2‐one1. TheirEconfiguration was established from the chemical shift's values of the vinylic proton and by1H nmr NOE difference spectroscopy. Cycloadditions of3bupon styrene or stilbene were catalyzed by boron trifluoride etherate. The cycloadducts were obtained with t