Assignment of13C Resonances in the Phencyclone-Norbornadiene Adduct Via 2D NMR.13C Evidence for Hindered Rotation of Unsubstituted Bridgehead Phenyl Rings

13C NMR chemical shift assignments were obtained for the Diels-Alder adduct of phencyclone with norbornadiene in CD2Cl2 and in CDCl3 solution. The 13C spectrum at 50.3 MHz, as well as the 1H spectrum at 200.1 MHz, show evidence for hindered rotation of the two unsubstituted bridgehead phenyl rings of the adduct at ambient temperatures. In CD2Cl2 solution, all 19 of the unique 13C nuclei of this molecule give rise to individual 13C resonances. The 1H assignments which were made earlier, together with one-bond and long-range 2D heteronuclear correlation experiments, allowed the assignment of all 13C chemical shifts in the molecule.