1H‐NMR study and conformational aspects of some bicyclo[3.2.0]heptane derivatives

Abstract The 1H‐NMR parameters of endo 2‐hydroxy‐bicyclo[3.2.0]heptan‐6‐one (1), 6,6‐dimethoxy‐bicyclo[3.2.0]heptan‐2‐one (2) and bicyclo[3.2.0]heptane‐2, 6‐dione (3) are discussed, allowing configurational and conformational descriptions. The usual 1H‐nmr criterion based on the observation of one single coupling to state the configuration of the ring annelation in bicyclo[3.2.0]heptane derivatives being not safe, a complete analysis of the ring system seems to be the only alternative as is illustrated for 1. It is found that the five‐membered rings occur in a twist(T)conformation, somewhat more flattened in 2 and 3.