Brother vs. Brother: Competitive Stabilization of Carbocationic Centers by Flanking Cyclopropanes and π-Systems
B3LYP and MP2 quantum chemical calculations on cyclopropylcarbinyl cations fused to various cyclic and polycyclic architectures are described. ‘Competition' for delocalization between the cyclopropane and other cyclopropanes and/or π‐systems incorporated into the (poly)cyclic framework to which it is fused was assessed, primarily through the use of characteristic geometric perturbations to the cyclopropane substructure. For example, a linear correlation between the orientation of the ‘empty p‐orbital' at the carbocationic center, which is affected by the nature of the (poly)cyclic framework, and the magnitude of bond elongation in the cyclopropane was observed. Possible bis‐ and trishomoaromaticity of some systems was also evaluated using nucleus independent chemical shift (NICS) and magnetic susceptibility exaltation calculations.
cyclopropane, polycyclopropane, cyclopropylcarbinyl, carbocation, polycyclic, homoaromatic, trishomoaromatic, substituent effects
Siebert, Matthew R., and Dean J. Tantillo. "Brother versus brother: competitive stabilization of carbocationic centers by flanking cyclopropanes and π‐systems." Journal of Physical Organic Chemistry 20, no. 6 (2007): 384-394.
Journal of Physical Organic Chemistry