In order to obtain information on the cause of low field shift of 1 H NMR signals of 'acetylene- cumulene'-dehydroannulenes on introduction of substituents, the syntheses of 1, 8- bisdehydro [14]-and 6, 8, 15, 17-tetrakisdehydro [18] annulenes bearing p-substituted phenyl group (s) have been performed. The examination of their 1 H NMR spectra indicates that the low field shift of NMR signals can be regarded as a superposition of three effects, ...
