Stereoelectronic Effects on .PI.-Facial Selectivity in Addition to 4H-1,3-Dioxin-4-ones.

π-Facial selectivity in catalytic hydrogenation and conjugate addition of a series of 2, 2-disubstituted 4H-1, 3-dioxin-4-ones was examined. The results indicated that pyramidalization at the reaction center of dioxinones is less important than other stereoelectronic effects and the steric effect as the origin of π-facial selectivity.