Polycyclic compounds 1a−c were synthesized to study the diatropic effects of a flanking phenyl ring on nearby CH and CF bonds. 19 F NMR spectra of 1b and 1c were strongly deshielded compared with those of the ring-opened compounds 3b, 7b, and 7c. DMol3 calculations on 1a−c provided quantitative bond lengths and torsional angles to support the conclusion that the downfield shifts in the 19 F NMR spectra are mainly due to steric interactions between the CF bonds and the π clouds of the phenyl ring(s).I nter-and intramolecular CH−π and CF−π interactions play important roles in host−guest chemistry, molecular assembly, and the folding of proteins and polynucleotides. 1 The CH−π interaction is a weak force (0.5−2.5 kcal/mol) 2a that is usually difficult to measure directly using molecules with flexible conformations. Therefore, the measurement of this weak interaction in molecules with intramolecular folding and unfolding has intrigued chemists for decades. 2 Recently, Tsuzuki 3a reported an excellent review that summarizes recently reported gas-phase measurements and high-level ab initio calculations of the CH−π interactions. Ab initio calculations show that the major source of attraction in the CH−π interactions is the dispersion interaction, while the contribution from electrostatic interactions is small. On the other hand, Nishio et al. 3b surveyed and analyzed literature results relevant to the CH−π interactions in crystal packing and conformations based on data reported in crystallographic databases (CSD and PDB). Moreover, as the organofluoride compounds are getting more popular in medicinal chemistry, the need to study CF−π interactions in organic and biological molecules has markedly increased. In order to study such CF−π interactions efficiently, one needs to have a special molecular design in which the CF bond is pointing toward conformationally rigid π bonds or aromatic rings. 4 In previous literature, the typical CF−π interactions between fluoromethane and benzene/hexafluorobenzene were only theoretically studied. For example, the very weak attractive interaction between the fluorine of HF and hexafluorobenzene was measured on the basis of theoretical calculations. 5a Kawahara also indicated that a weak interaction between fluoromethane and hexafluorobenzene was observed; furthermore, it is worth noting that this was an attractive force. 5b Nowak, however, studied CF−π interactions by measuring the effect of fluorine on the reactivity of a proximal double bond using a polyfluorinated indacene system. 6 The through-space interactions between the CF bond and the π electrons of alkenes were explained by Lectka 7 to be due to steric hindrance, anchimeric assistance, and the repulsive interactions from overlap of lone-pair electrons on fluorine with the π electrons on the olefin. Furthermore, they reported that the fluorine was little perturbed by anisotropic effects from the π electrons of the alkene, and only a slight upfield shift relative to theoretical values of fluorine chemical shifts...