Birch reductive arylation by mechanochemical anionic activation of polycyclic aromatic compounds

Birch reduction is a well-known process for transforming aromatic compounds. The reduction of aromatic rings using alkali metals produces anionic species that react with protons or electrophiles. Generally, this reaction is accompanied by significant limitations in the available nucleophiles, since in most cases only alkyl halides and silyl chlorides are available. In particular, the arylation of unfunctionalized polycyclic aromatic hydrocarbons (PAHs), so-called Birch reductive arylation, has not yet been investigated. Herein, we report a Birch reductive arylation by mechanochemical anionic activation using a lithium(0) wire, followed by addition of various fluoroarenes. Specifically, not only Birch reductive arylation products but also formal C–H arylation products can be obtained from unfunctionalized PAHs, achieving one-pot annulative π-extension to give nanographenes. This process is a unique reaction that is rarely achieved in solution, and shows the interesting reactivity of lithium metal and fluoroarenes in the solid state.