Herein, we report the palladium-catalyzed borylation of aryl halides (iodides or bromides) under base-free conditions utilizing a commercially available Lewis acidic mediator, Zn(OTf). Under these conditions, an array of electronically and functional-group-diverse aryl iodides and bromides undergo borylation to afford the corresponding aryl boronic esters in ≤82% isolated yields. Mechanistic investigations are consistent with Zn(OTf) enabling transmetalation between a cationic Pd(II)-Ar intermediate and Bpin via halide abstraction. Furthermore, stabilization of the cationic [ArPd] complex with added [BAr] significantly improves the reaction efficiency with electron-poor arenes.
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