Stereochemistry of ketonization of enols and enolates (original) (raw)

In the stereochemistry of ketonization of enols and enolates, theory is provided explaining the diastereoselectivity observed in the conversion of certain enols and enolates into the corresponding ketone. It was proposed in 1955 that the kinetic protonation of enolic species proceeds with an early transition state with the alpha carbon being close to sp2 hybridized. The proton donor selectively approaches the less hindered face of the enolate, thus leading to the less stable of two diastereomers. Reactions controlled in this fashion include: