Towards the annealation of a five and seven- membered ring to an alternant polycyclic aromatic hydrocarbon.

Abstract

The anti-symmetric behaviour of cyclohepta-fused and cyclopenta-fused PAHs make these two annealed odd-membered rings interesting moieties to combine and fuse on the same aromatic perimeter, e.g. pyrene. The synthesis of cyclopenta-cycloheptapyrene 11 is attempted with different synthetic strategies, making use of pyrene (1) and 1,2,3,6,7,8-hexahydropyrene (2) as precursors. However, the use of 2 as starting material turned out to require tedious synthetic procedures and laborious purification steps. A promising effort in the synthesis of 11 is made by acylation of 3,4- dihydrocyclopenta[cd]pyrene (7), after which ringclosure of the acylated compound 23 afforded the bis-keto cyclohepta-derivative 24. Subsequently, 24 is transformed into the suitable FVT precursor 26, which is obtained properly, though impure containing a lot of salts. Although GC-MS analysis substantiated the obtention of 24, subjecting it to FVT afforded polymeric material and no desired product.