2-Phenylcyclododecanone and 2-cyclohexylcyclododecanone derivatives were
synthesized and characterized by 1H NMR, 13C NMR, HR-ESI-MS and X-ray diffraction.
Their preferred conformations were analyzed by the coupling constants in the 1H NMR
spectra and X-ray diffraction, which showed the skeleton ring of these derivatives containing
[3333]-2-one conformation, and the phenyl groups were located at the side-exo position
of [3333]-2-one conformation due to the strong π-π repulsive interaction between the π-
electron of benzene ring and π-electron of carbonyl group. The cyclohexyl groups were
located at the corner-syn or the side-exo position of [3333]-2-one conformation depending
on the hindrance of the other substituted groups. The π-π electron effect played a crucial role in
efficiently controlling the preferred conformation of 2-aromatic cyclododecanone and the other
2-aromatic macrocyclic derivatives with the similar preferred square and rectangular conformations.