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Updated: Jun 2, 2026

Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
Proton-catalyzed, silane-fueled Friedel-Crafts coupling of fluoroarenes
Oliver Allemann1, Simon Duttwyler, Paola Romanato
1Organic Chemistry Institute, University of Zürich, Winterthurerstrasse 190, Zürich CH-8057, Switzerland.
Abstract:
The venerable Friedel-Crafts reaction appends alkyl or acyl groups to aromatic rings through alkyl or acyl cation equivalents typically generated by Lewis acids. We show that phenyl cation equivalents, generated from otherwise unreactive aryl fluorides, allow extension of the Friedel-Crafts reaction to intramolecular aryl couplings. The enabling feature of this reaction is the exchange of carbon-fluorine for silicon-fluorine bond enthalpies; the reaction is activated by an intermediate silyl cation. Catalytic quantities of protons or silyl cations paired with weakly coordinating carborane counterions initiate the reactions, after which proton transfer in the final aromatization step regenerates the active silyl cation species by protodesilylation of a quaternary silane. The methodology allows the high-yield formation of a range of tailored polycyclic aromatic hydrocarbons and graphene fragments.
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