(Z)-3-(3-Phenylallylidene)-1,5-dioxaspiro[5.5]undecane-2,4-dione

In the title compound, C18H18O4, the 1,3-dioxane ring adopts a distorted envelope conformation with the C atom common to the cyclohexane ring forming the flap. In the crystal, inversion dimers linked by pairs of C—H...O hydrogen bonds occur.