The [4+2] cycloaddition of chromone-fused dienes with enamines was found to be an efficient method for the synthesis of 4,4a- and 3,4-dihydroxanthone derivatives. Either product type could be obtained by choosing the proper conditions [reaction time and addition of La(NO₃)₃ as a Lewis acid]. Calculations using density functional theory and Møller–Plesset perturbation theory showed that the isomerization of 4,4a-dihydroxanthones to 3,4-dihydroxanthones occurred through a base-assisted sigmatropic rearrangement. The described reaction provides a convenient route to a natural-product-inspired group of 4,4a-dihydroxanthones with cytotoxic activity.