A Phosphine-Accelerated Ar_F–Chloride Bond Activation Process by Palladium

We present a mechanistic study demonstrating selective Arf–Cl bond activation preceded by η2 coordination of Pd­(PEt3)2 to a CC moiety of a partially fluorinated substrate. An intramolecular ring-walking process to activate the Arf–Cl bond is plausible, but an intermolecular reaction becomes dominant in the presence of PEt3. The latter pathway is significantly enhanced, since PEt3 promotes dissociation of Pd­(PEt3)3 from the CC moiety followed by activation of the Arf–Cl bond. Our observations also show that PEt3 can be used to control reaction selectivity. The experimental observations are supported by density functional theory (DFT) calculations (at the SMD­(toluene)-DSD-PBEP86/cc-pV­(D+d)­Z-PP//DF-PBE+dv2/SDD­(d) level of theory).