Fused aromatic compounds, and

In general there is a good correlation between bond distances in fused aromatic compounds and bond orders. Another experimental quantity that correlates well with the bond order of a given bond in an aromatic system is the nmr coupling constant for coupling between the hydrogens on the two carbons of the bond.74... 

Fused aromatic compounds such as polyacenes have attracted much attention as organic conductive materials. However, established methods are very limited. Lack of general and convenient synthetic methods for fused aromatic compounds and their very poor solubility in organic solvents are the most serious problems that control further advances in this very important field. Taka-hashi and coworkers have recently developed a synthetically useful method for preparation of fused aromatic compounds, by using the zirconocene-mediated aromatization of alkynes. In order to solve the solubility problem, alkyl substituents are introduced into to the skeletons. In principle, two types of synthetic protocols have been used. Type I protocol is via the homologation starting from a functionalized benzene derivative (Scheme 3) [75] the Type II protocol is via the intermolecular cycloaddition of two alkynes to an arene (Scheme 4) [76]. 

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