Abstract:
In 1952 Pullmann et al. Pullmann, B., Pullmann, A., Berthier, G., and Pontis, J., J. chim. Phys., (1952), 49, 20 made a theoretical study of pleiadiene (1), acepleiadylene (2), pleiadene (3), and benzo [4,5] cyclohepta [de] naphthalene (4).
Boekelheide and Vick Boekelheide, V., and Vick, G.K., J. Am. chem. Soc. (1956), 78, 653 have synthesised pleiadiene (1) and acepleiadylene (2), and they have shown that their properties, both chemical and physical, agreed with those predicted by calculation. Attempted syntheses of pleiadene (3) and its acenaphthylene analogue (5) were described by Cava and Schlessinger Cava, M.P., and Schlessinger, R.H., J.Am. chem. Soc. (1963), 85, 835 in 1963. They showed that these compounds were much less stable than pleiadiene or acepleiadylane; neither compound could be isolated, both being obtained as the dimer resulting from a Diels-Alder self-condensation reaction.
As Craig, J.T., Aust. J. Chem., (1966), 19, 1927 has indicated, this instability might have been predicted by analogy with the increasing reactivity in the acene series which results from linear fusion of six membered rings. On the other hand, the hydrocarbon, benzo [4,5] cyclohepta [de] naphthalene (4), resulting from angular fusion of a six membered ring to one of the formally fixed double bonds of pleiadiene (l) might be expected to be more stable than, or at least as stable as, pleiadiene itself.
