Polycyclic aromatic hydrocarbons (PAHs) are a class of molecules composed of fused aromatic rings. These molecules can be used as the building blocks to larger molecules, such as carbon nanotubes or fullerenes. Non-alternant PAHs are valuable in creating bowl shaped molecules through a process referred to as indenoannulation. Indenoannulation is a method where intramolecular cyclization occurs producing a five membered ring between a benzene ring and base PAH molecule.  There are several current methods to produce indenoannulated products, which include acid-catalyzed cyclization, flash vacuum pyrolysis (FVP), and palladium-catalyzed cyclization. Although these methods do complete an indenoannulation, they all have major disadvantages. In order to eliminate the disadvantages of these current methods, we have created a new process that allows for the synthesis of a wide variety of annulated and indenoannulated PAH compounds. The first step of our method installs a cyclohexanone unit on to a brominated PAH using the Buchwald-Hartwig cross-coupling reaction. This arylated-ketone is then converted to a regiospecific enol-trifilate, which is then subjected to a palladium-catalyzed cyclization forming the annulated PAH.  The conversion of the annulated PAH to an indenoannulated PAH is accomplished by the efficient oxidation of the saturated six-membered ring to an aromatic ring with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). Each step of this process provides excellent conversions and good to excellent yields. Further work will center on the use of this process to create large curved PAHs specifically tetraindenopyrene and the end cap of a single chirality carbon nanotube.

New method for the annulation of polycyclic aromatic hydrocarbons

247th National Meeting (2014)

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