Polycyclic aromatic hydrocarbons, (PAHs) are structures that are formed from aromatic rings of various sizes. Some of the PAH's are curved molecules and are produced through a reaction known as an indenoannulation. An indenoannulation is a reaction that involves the intramolecular formation of a five membered ring between a PAH and a benzene ring.  These indenoannulations are highly important when dealing with the formation of fullerenes and fullerene fragments.   Various fullerenes have been synthesized such as C60, C70, and C84, however, it is suggested that fullerenes between these standard sizes also exist.  C72 is one of these missing fullerenes and has been calculated to be stable, but has never been isolated without a metal encapsulated inside the cage.  Our long-term goal is to synthesize C72, but new methods will have to be developed before we proceed. Currently we are designing a new method for the creation of aromatic ketones that we can use in the synthesis of C72. Our proposed method first relies upon a Buchwald-Hartwig cross coupling reaction between 1,3-cyclohexanedione and a brominated PAH. This arylated diketone will be converted into an enol-triflate, followed by a ring closure that is accomplished by a palladium catalyst to yield a new class of aromatic ketones. We plan to extend this method to synthesize one of the intermediates in our proposed synthesis of C72.  So far, the first two steps have been successfully completed on numerous substrates.  Future work will focus on the final palladium-catalyzed closure and beginning the synthesis of C72.

New palladium-catalyzed method for the synthesis of novel aromatic ketones

243rd National Meeting (2012)

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