Synthesis of an Unsymmetrical Phenyl-Substituted [7]Phenacene

Posted May 26th, 2010 at 3:08 pm.

Annie Butler and Joy Racowski

Mentor: Dr. Frank Mallory

One of the major objectives of Professor Frank Mallory’s laboratory is the development of methods for the synthesis of [n]phenacenes. What are [n]phenacenes? They are compounds with chains of n benzene rings fused in an extended zig-zag or phenanthrene-like formation. Our particular project involves synthesizing a particular unsymmetrical [7]phenacene with four phenyl substituents attached to the first, third, fifth, and seventh rings, respectively, of the polycyclic framework of the molecule. This compound is being synthesized in order to determine whether phenyl substituents are more effective as solubilizing groups than tert-butyl substituents by comparing the solubility of this compound to the solubility of the previously synthesized [7]phenacene derivative with four tert-butyl solubilizing groups in place of the four phenyl groups.

Along with the solubility tests, it will be of interest to obtain the crystal structure of the unsymmetrical phenyl-substituted [7]phenacene to determine how the Van der Waals repulsions involving the crowded phenyl substituents influence the orientations of those phenyl groups with respect to the polycyclic framework of the compound. It is hypothesized that two orientations are conceivable. One of these would have an alternating pattern in which the phenyl groups on the first and fifth rings of the framework are bent forward out of the plane of the framework, while the phenyl groups on the third and seventh rings of the framework are bent backwards out of the plane of the framework. The other conceivable orientation would have all of the crowded phenyl groups bent in the same sense with respect to the polycyclic framework (that is, either all bent forward or all bent backward), with the result that the framework would be continuously twisted in a screw-like fashion.

We plan to synthesize the previously unknown target molecule through a multi-step iterative process involving reactions such as Wittig reactions, lithiations of aryl bromides, formations of phosphonium salts, and photocyclizations.

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