Abstract:
Phenanthro [3,4-c] - phenanthrene (I) represents a very interesting example of a purely aromatic hydrocarbon which owes its asymmetry to intramolecular overcrowding. The systematic name "helicene" was proposed by Newman and Lednicer (I) for nuclei of this type, as these are coiled in a helical fashion. Under this system, this compound I would be known as "hexahelicene."
The intramolecular overcrowding is due to the carbon atoms in the 11,12 and 13,14 positions interfering.
From a brief reference to molecular models it appears that the fusion of a benzene ring to hexahelicene to give 11,12-benzo-phenanthro [ 3,4-c ] - phenanthrene, or heptahelicene (II) would not alter the steric strain to any great extent, and the object of this work was to investigate possible syntheses of compounds which might be used as intermediates in the synthesis of such a compound.
