Intramolecular Photoaddition of Alkenes to Chiral 1,3-Dioxin-4-ones: Evidence for Effect of Pyramidalization on the Facial Selectivity

Article abstract of DOI:10.1021/jo00126a045

Intramolecular photoaddition of alkenes to chiral 1,3-dioxin-4-ones 5 present, for the first time, examples with high facial selectivity in which the addition proceeds preferentially from the less exposed side (b-side) under kinetic control conditions.This unprecedented facial selectivity cannot be explained only on the basis of steric effects; however, it is consistent with the direction of pyramidalization in structure 3.It can be concluded that the geometry of the pyramidalized C_β in the triplet excited dioxinones plays an important role in defining the facial selectivity in this reaction.However, steric effect cannot be neglected in rationalizing the facial selectivity as found by comparing the facial selectivity obtained in the irradiation of the studied compounds.