The conformations of bicyclo[3.1.0]hexane derivatives by 1H and 13C NMR

The ¹H and ¹³C spectra of bicyclo3.1.0]hexanes and thujanes have been recorded and assigned. Application of the Karplus equation has yielded dihedral angles, and a computer calculation of the angle of ring buckle as a function of the main dihedral angles has been carried out. The calculated angles of ring buckle agree well with known values in the bicyclo3.1.0]hexanes, but for 1-methylbicyclo3.1.0]hexanes and thujanes the results are not self consistent. It is suggested that the bridgehead substituent causes the boat to twist, although the twist can be reduced by an axial methyl substituent on C-4.