Natural-abundance studies of 13C13C coupling constants. Substituent dependencies of directly bonded and vicinal 13C13C coupling constants in 1-substituted bicycloalkanes
A series of 1-substituted-bicyclo[2.2.2]octanes and bicycloalkane-l-carboxylic acids were synthesized and the 13C13C coupling constants were measured in natural abundance by 13C satellite and/or double-quantum coherence methods. Experimental data for vicinal/geminal coupling between the bridgehead carbon atoms are in good agreement with calculated molecular orbital results, which are based on the INDO-FPT method for the Fermi contact contributions. Although the numerical agreement for the directly bonded 13C13C coupling constants is not as good, the substituent trends are well reproduced. Moreover, a linear least squares fit of the calculated and experimental data for the bicyclo [2.2.2]octanes provides a good correlation of most of the directly bonded coupling constant data. This is discussed in terms of the approximations which are implicit in the INDO-FPT method. © 1984.
