Computational Studies on the Involvement of PhI(OAc) ₂ on CMD Pathways for the Intramolecular C(sp ³ )-H Activation Mediated by Palladium

The first systematic computational simulation study on the CMD (concerted metalation-deprotonation) process of C(sp³)-H bonds involving PhI(OAc)₂ (phenyliodine(III) diacetate, a hypervalent iodine reagent) has been reported. Two distinct CMD pathways were comparatively analyzed: (1) the conventionally directed concerted metalation-deprotonation (CMD) pathway and (2) the oxidative-addition-preceded CMD. The latter exhibits enhanced kinetic accessibility and thermodynamic favorability under the influence of a tetravalent mononuclear palladium system. Density functional theory (DFT) calculations systematically reveal that PhI(OAc)₂ initially decomposes into OAc radicals, which oxidize the Pd(II) intermediate to generate the Pd(IV) species, with subsequent CMD completion occurring in this high-valent state. Both computational and experimental results demonstrate that the PhI(OAc)₂ system exhibits superior efficiency compared with conventional silver-based (AgOAc) and inorganic salt (NaOAc) systems. Wave function analysis identifies the stabilized CMD transition state in the PhI(OAc)₂ system as directly attributable to the strongest basicity of the hydrogen-abstracting acetoxy group.