 Electron-donating substituents at C3 subsequently favor equatorial approach, since increasing C–C electron density favors σC-C donation into σ*C-Nuc and thereby encourages equatorial approach.This effect can also be investigated by changing the electronic nature of the nucleophile.In the case of an electron-deficient nucleophile, the σ* of the forming C-Nuc bond is lower in energy and better stabilized by attack antiperiplanar to electron-rich axial C-H bonds.