Flow-Assisted Synthesis of [10]Cycloparaphenylene through Serial Microreactions under Mild Conditions

Cycloparaphenylene (CPP) has been recognized as an attractive template for the bottom-up synthesis of carbon nanotubes with uniform diameter, and is important for the chemistry of graphitic as well as ring-shaped macromolecules. However, the reported routes from halogenated benzenes have suffered from low yields even under time- and labor-consuming multistep conditions. Herein we report a flow-assisted synthesis of [10]CPP in four steps under mild conditions. For the synthesis, a selective nucleophilic addition of the unprotected diketone without the double-added byproduct was achieved within 3 s in high yield. Subsequently, the obtained compound was reacted with dilithiated benzene at 25°C to form a U-shaped precursor for CPP in a separate microreactor, which was finally dimerized and aromatized to obtain [10]CPP by a two-step in-flask reaction. Precise control of time and flow facilitated by the flow-assisted system enabled the development of an efficient synthetic route for [10]CPP.