Size-selective Synthesis of [n]Cycloparaphenylenes and Related Benzenoid Macrocycles

Abstract

This work begins with a discussion of the currently existing methods for the π-extension of nonplanar aromatic systems with a focus on reactions pertaining to the π-extension of cyclophane-based molecules. Completing the first chapter is a synthesis of “[n]PQPPs”, a new model system developed for the purpose of modeling π-extension on para-linked curved benzenoid systems, particularly with the goal of investigating reactions for use with [n]cycloparaphenylenes.

The second chapter includes a review of the history of [n]cycloparaphenylene synthesis and the key methods that are in use for the construction of these nanohoop structures, which represent the smallest possible cross section of armchair carbon nanotubes. After this summary of the field, I report my size-selective synthesis of [6], [8], and [10]cycloparaphenylenes from a cyclohex-2-ene-1,4-diol-containing key intermediate building block, along with an attempted synthesis of [5]cycloparaphenylene which fell short only at the final step. A pathway is then proposed for the completion of [5]CPP based on previous results in our lab.

The third and final chapter of this document follows this with a summary of the existing strategies for the functionalization of [n]CPPs, including publications in which the functional groups are installed early in the sequence and carried through the steps as well as late-stage modifications of existing cycloparaphenylenes. Ending this chapter is a concise synthesis of an octamethoxy derivative of [12]cycloparaphenylene, which is proposed as a precursor to a wide cross section of a [12,12]carbon nanotube.