11C-Cyanation of Aryl Fluorides via Nickel and Lithium Chloride-Mediated C-F Bond Activation

Aryl fluorides are expected to be useful as radiolabeling precursors due to their chemical stability and ready availability. However, direct radiolabeling via carbon-fluorine (C-F) bond cleavage is a challenging issue due to its significant inertness. Herein, we report a two-phase radiosynthetic method for the ipso-C-11-cyanation of aryl fluorides to obtain [C-11]aryl nitriles via nickel-mediated C-F bond activation. We also established a practical protocol that avoids the use of a glovebox, except for the initial preparation of a nickel/phosphine mixture, rendering the method applicable for general PET centers. This method enabled the efficient synthesis of diverse [C-11]aryl nitriles from the corresponding aryl fluorides, including pharmaceutical drugs. Stoichiometric reactions and theoretical studies indicated a significant promotion effect of lithium chloride on the oxidative addition, affording an aryl(chloro)nickel(II) complex, which serves as a precursor for rapid C-11-cyanation.

Automated summary

In this study, a two-phase radiosynthetic method for the ipso-C-11-cyanation of aryl fluorides was developed, using nickel-mediated C-F bond activation. A practical protocol was established that does not require a glovebox, making it applicable for general PET centers. This method enabled the efficient synthesis of diverse [C-11]aryl nitriles, including pharmaceutical drugs. Stoichiometric reactions and theoretical studies demonstrated the significant promotion effect of lithium chloride on the oxidative addition, facilitating rapid C-11-cyanation.