HOMOCONJUGATION AND TRANSANNULAR ORBITAL INTERACTIONS DETECTED BY PHOTOELECTRON AND C-13-NMR SPECTROSCOPY - BICYCLO[3.3.1]NONA-3,7-DIENE-2,6-DIONE AND BICYCLO[3.3.1]NONANE-2,6-DIONE

Transannular orbital interactions between two ketone carbonyl groups located at positions 2 and 6 on the bicyclo [3.3.1] nonane carbocyclic framework were detected by C-13-NMR and photoelectron spectroscopy (PES). Thus, an approximately 4.4-ppm shielding of the delta(C = O) is observed in the C-13-NMR spectra of the saturated diones (1 and 3) relative to the monoketones (7 and 9), and in the PE spectra, an approximately 0.15-eV splitting of the n-orbitals of the diones is detected. In the bis-enone analogues (2 and 4) the shieldings (relative to the corresponding mono-enones, 8 and 10, respectively) are more than doubled, to approximately 10 ppm, and significant splittings are observed in the PE spectra for both n-orbitals (approximately 0.1 eV) and pi-orbitals (approximately 0.3 eV), The origin of the electronic interaction would appear to come from orbital interaction through space and through sigma-bonds.