Anomalous Stereoselectivity in the Wittig Reaction: the Role of Steric Interactions

Stępień, M.
J. Org. Chem. 2013, 78, 9512-9516 | view at publisher's site

Density Functional Theory calculations combined with a distortion/interaction energy analysis show that the anomalous Z-selectivity observed in Wittig reactions of ortho-substituted benzaldehydes is not caused by phosphorus–heteroatom interactions in the addition transition state, as assumed in earlier work, but is predominantly steric in nature. Calculations reproduce correctly stereoselectivity preferences for a wide range of reactant pairs, as well as relative reactivities for different substituent types, providing a deeper structural insight into the mechanism of Wittig olefination.