Synthesis and 1H NMR Spectral Behavior of a Methano[20]annulenedione Derivative
A potential 18π-electron system, 11,16-dimethyl-12,14-bisdehydro-1,6-methano[20]annulene-7,20-dione was synthesized and its 1H NMR spectral behavior in CDCl3, CF3CO2D, and D2SO4 was studied. The energy barrier to the methylene flipping was highly dependent on the medium.