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1H, 13C and 17O NMR spectroscopic study of four bicyclo [3.1.1]heptenes (derivatives of α‐pinene) and four bicyclo[3.1.1]heptanes (derivatives of β‐pinene)

Four derivatives of 2, 6, 6‐trimethylbicyclo[3.1.1]hept‐2‐ene (α‐pinene) and four derivatives of 2‐methylene‐6, 6‐dimethylbicyclo[3.1.1]heptane (β‐pinene) were synthesized and their 1H, 13C and 17O NMR spectra were measured, analysed and assigned. The 1H NMR spectral parameters were obtained by computer‐aided analyses of the very complex multi‐spin, second‐order spectra. Some of the 13C NMR chemical shift assignments of these compounds reported in the literature should be changed, based on these accurate 1H 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.