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 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 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 CPP.
- flow chemistry
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