A Precisely Bromo‐Functionalized [9]Cycloparaphenylene as a Platform for Late‐Stage Multisite π‐Extension Toward Chiral Nanohoops

Abstract Selective functionalization of [ n ]cycloparaphenylenes ([ n ]CPPs) has remained a significant synthetic challenge due to their inherent ring strain. In this study, we present the synthesis of a [9]CPP derivative in which bromo groups are orderly introduced at the 2,5‐positions of three benzene rings in the [9]CPP framework, each separated by two phenylene units. The use of our developed Au‐mediated CPP synthetic method enabled efficient and scalable access to the target compound in five steps with an overall yield of 37%. The resulting molecule exhibited phosphorescence at low temperature, arising from the heavy‐atom effect of the bromo substituents. Furthermore, post‐functionalization through Pd‐catalyzed coupling reactions demonstrated multisite π‐extension and afforded a chiral nanohoop exhibiting exceptional chiroptical performance (| g lum | = 0.100).