Face selectivity in electrophilic additions to methylenenorsnoutanes: relative importance of through-space, through-bond and electrostatic interactions

4-Substituted 9-methylenenorsnoutanes undergo a variety of electrophilic additions with a small but consistent syn preference; ab initio MESP maps indicate that electrostatic factors and through-space interaction between the double bond and cyclopropane Walsh orbitals are unimportant in determining the face selectivity, while AM1 transition state energetics suggest that the observed preferences are determined primarily by through-bond interactions.