H-1, C-13 AND O-17 NMR SPECTROSCOPIC STUDY OF 4 BICYCLO [3.1.1]HEPTENES (DERIVATIVES OF ALPHA-PINENE) AND 4 BICYCLO [3.1.1]HEPTANES (DERIVATIVES OF BETA-PINENE)

Four derivatives of 2,6,6-trimethylbicyclo[3.1.1]hept-2-ene (alpha-pinene) and four derivatives of 2-methylene-6,6-dimethylbicyclo[3.1.1]heptane (beta-pinene) were synthesized and their H-1, C-13 and O-17 NMR spectra were measured, analysed and assigned. The H-1 NMR spectral parameters were obtained by computer-aided analyses of the very complex multi-spin, second-order spectra. Some of the C-13 NMR chemical shift assignments of these compounds reported in the literature should be changed, based on these accurate H-1 NMR spectral analyses and carbon-proton chemical shift correlated spectra (COSY). The new assignments are supported by the 1J(C,H) values, which show a strong dependence on the bond angle and the steric strain of the ring system concerned.