Substituent Effect on the Enantiomer-Differentiating Reaction of Lithiomethyl p-Tolyl Sulfoxide with Meta- or Para-Substituted (R)-(-)-Menthyl Benzoates

Article abstract of DOI:10.1246/bcsj.62.2229

Treatment of (R)-(-)-menthyl benzoates, which have a variety of meta- or para-substituents, with 2 equivalents of racemic lithiomethyl p-tolyl sulfoxide displays the feature of an enantiomer-differentiating reaction, affording the corresponding optically active β-keto sulfoxides.The degree and the direction of enantioselectivity were affected by the nature of the substituent on benzene ring.The electron-releasing substituents trend to increase the percente.e. value.The reversal in the configuration with the variation in the substituent which has a high electron-withdrawing p-CN group was also observed.The R/S values thus obtained gave a good correlation with Hammett's ? values (γ = 0.975), affording a negative straight line. based on these observations, a plausible stereochemical course of this reaction has been discussed.