Size-Selective Syntheses of [n]Cycloparaphenylenes and the Development of an Allylic Arylation Strategy for π-Extension of Benzenoid Systems

Abstract

Chapter 1: [n]Cycloparaphenylenes ([n]CPPs) are strained π-conjugated macrocycles that serve as fundamental models for armchair carbon nanotubes, yet their size-selective synthesis and functionalization remain challenging. This chapter presents a versatile strategy for size-selective synthesis of [n]CPPs using syn cyclohex-2-ene-1,4-diol building blocks. L-shaped intermediates undergo Suzuki–Miyaura and platinum mediated macrocyclization, followed by mild dehydrative aromatization to afford [8], [10], [12], [15], and [16]CPPs in high yields. This work represents the first application of this diol and aromatization method to [n]CPPs.

Chapter 2: To overcome the limitations of multistep, harsh PAH synthesis, this chapter reports a modular strategy using FeCl3.6H2O-catalyzed allylic arylation of syn-cyclohex-2-ene-1,4-diol derivatives. This mild, regioselective carbon–carbon bond formation enables efficient aromatization to triphenylene-based PAHs, which are readily functionalized for π-extension, offering a versatile platform for diverse nanocarbon frameworks.

Chapter 3: This chapter describes the synthesis of a tetra-phenylethynyl-substituted [6]cycloparaphenylene as a platform for π-extension toward carbon nanobelts (CNBs) and carbon nanotubes (CNTs). While [n]CPPs are precise molecular templates, their transformation into extended nanocarbon systems faces several challenges. The nanohoop was synthesized via platinum-mediated macrocyclization, followed by deprotection and aromatization. The functionalized [6]CPP is designed for iodine monochloride–mediated benzannulation for CNB synthesis.