Towards the Highly Efficient Synthesis and Selective Methylation of C(sp³)‐Bridged [6]Cycloparaphenylenes from Fluoren[3]arenes

Abstract

An approach to the highly efficient synthesis of C(sp3)-bridged [6]cycloparaphenylenes (C[6]CPPs)f rom fluoren[3]arenes (F[3]As)w as developed. Consequently, F[3]As as anew kind of macrocyclic arenes were synthesized. Followed by the demethylation, triflation and intramolecular aryl-aryl coupling reactions, C[6]CPPs were then conveniently obtained. Interestingly, C[6]CPPs could be selectively methylated to produce their fully outer-methyl-substituted derivatives.T he crystal structures showed the hydroxyl-substituted F[3]As had bowl-shaped conformations,a nd the C[6]CPPs exhibited rigid belt-shaped structures with deep cavities.Moreover, C[6]CPPs exhibited high HOMO energies and narrowe nergy gaps.A nu nclosed belt was further obtained, and it not only showed as imilar narrowe nergy gap to those of the aromatic belts,b ut also displayed strong fluorescence property,whichcan play avital role in the design and synthesis of new aromatic belts.