Evidence of a Wheland Intermediate in Carboxylate-Assisted C(sp2)−H Activation by Pd(IV) Active Catalyst Species Studied via DFT Calculations

Evidence of a Wheland intermediate in carboxylate-assisted C−H activation was found using DFT calculations when the Pd(IV) catalyst species postulated as active (ACS). In order to delineate reaction mechanism Pd-catalyzed bisarylation 3-alkylbenzofuran, five hypothetical species, [Pd(OAc)(PMe3)(Ph)] (I), [Pd(OAc)2] (II), [Pd(OAc)2(PMe3)] (III), [Pd(OAc)2(Ph)]+ (IV) and [Pd(OAc)2(PMe3)(Ph)]+ (V) were tested potential ACS candidates. The I, previously reported an context ambiphilic metal−ligand assistance or concerted metalation-deprotonation mechanism, unsuccessful, with maximum barriers (ΔG‡max) for C(sp2)−H C(sp3)−H activations 33.3 51.4 kcal/mol, respectively. ΔG‡max values II−V 23.8/28.7, 32.0/49.6, 10.9/10.9, 36.0/36.0 respectively, indicating that is likely IV. This forms state (IV_1) before proceeding transition (IV_TS1,2) activation, which C(2) atom 3-methylbenzofuran has substantial σ-character. degree σ-character IV_1 further evaluated quantitatively terms geometric parameters, partial charge distribution, strain analysis. analysis results support existence intermediate, long been recognized manifestation electrophilic aromatic substitution yet never identified computationally.