1H and 13C NMR Spectral Behavior and Isomerism in 7,12-Dimethyl-, 2,7, 12-Trimethyl-, and 7,12,15-Trimethyl-8,10-bisdehydro(15)annulenones.

Configurational and conformational isomerism in the bisdehydro[15]annulenones were studied in CDCl3 and CF3CO2D–CD2Cl2 solutions by 1H NMR spectroscopy. The 7,12-dimethyl compound with the initial “all-E” configuration isomerized in both media at ambient temperature to give an equilibrium mixture of isomers but the trimethyl derivatives retained their original configuration under the similar conditions. The charge distribution in the deuterated species was discussed on the basis of the 13C NMR spectra.