A Comparison of Macrocyclization Strategies for the Selective Synthesis of [8], [10], [12], [15], and [16]Cycloparaphenylene

The size-selective synthesis of [8], [10], [12], [15], and [16]cycloparaphenylene (CPP) is reported. The syntheses compare Suzuki-Miyaura and Pt-square-based macrocyclization strategies and feature a dehydrative aromatization reaction of macrocyclic cyclohex-2-ene-1,4-diols to furnish the carbon nanohoops. These unsaturated diols have proven to be versatile arene surrogates, enabling the synthesis of highly strained p-terphenyl-containing macrocycles, as well as functionalized and substituted bent p-phenylene units. This report represents the first time this aromatization protocol has been employed in the synthesis of [n]CPPs.