| Abstract
| - Two 14 π cross-linked annulenes which belong to the family of dicyclopenta[a,e]pentalenes havebeen synthesized, 14 π bis enol triflate ester 27 and the 3,7-diisopropylsilyl substituted 14 π dicyclopenta[a,e]pentalene 30. The new allenic tandem Pauson−Khand reaction mediated by Mo(CO)6 was employedas the key process to construct the core of the tetracycles. The two linear dicyclopenta[a,e]pentalenes 27and 30 underwent significant electronic delocalization, perhaps even aromaticity, as revealed by the X-raystructure of 27. The tetracyclic rings in 27 assumed a flat geometry (Figure 4); the bond lengths of thetetracycle in 27 also fit well into the criteria for aromatic compounds. A comparison of the NMR and UVspectra of both 27 and 30 demonstrated that they both exhibited similar electronic properties, therefore,the purple colored 14 π cross linked annulene 30 is planar as well as delocalized.
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