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. Go with the flow: The cycloparaphenylene (CPP) derivative [10]CPP was synthesized in four steps under mild conditions using a flow‐assisted synthetic method by precise control of the reaction time and flow rate. Selective nucleophilic addition of a lithiated benzene derivative to a diketone could be achieved in high yield without a protection/deprotection step.