NMR and theoretical investigation of dicylopentadiene derivatives

Abstract

AbstractThe 1H and 13C NMR spectra of endo‐tricyclo[5.2.1.02,6]deoane (1‐H), endo‐tricyclo[5.2.1.02,6]decan‐2‐ol (1‐OH) and 2‐endo‐tricyclo[5.2.1.02,6]decanyl acetate (1‐OAc) were assigned by the use of 1H1H, 1H13C and 13C13C correlation spectra. The substituent chemical shifts were similar to those observed for the analogous norbornane derivatives.2 The flip angle of the five‐membered ring and the conformational composition were estimated from the vicinal 1H1H coupling constants. The results were compared with those from molecular mechanics calculations (MMPMI) and semi‐empirical molecular orbital calculations (MNDO). The geometries obtained from the NMR data were close to those from the MMPMI calculations, and the calculated and observed energy differences were within ± 2 kJ mol−1 of each other. The endo conformation of the five‐membered ring was found to be most stable for both 1‐OH and 1‐OAc. The MNDO calculation indicated a close to planar five‐membered ring to be the most stable. This result could not be accommodated with the NMR data.