Functionalized Carbon Nanohoops: Synthesis and Structure of a [9]Cycloparaphenylene Bearing Three 5,8-Dimethoxynaphth-1,4-diyl Units

A functionalized [9]­cycloparaphenylene ([9]­CPP) bearing three evenly spaced 5,8-dimethoxynaphth-1,4-diyl units and two macrocyclic [6]­CPP precursors have been synthesized. The Diels–Alder reaction between (E,E)-1,4-bis­(4-bromophenyl)-1,3-butadiene and 1,4-benzoquinone followed by methylation produces cis-5,8-bis­(4-bromophenyl)-5,8-dihydro-1,4-dimethoxynaphthalene as the key intermediate for the construction of the hooplike structures. The nickel-mediated homocoupling reactions followed by aromatization led to the functionalized [9]­CPP.