Computational Studies on the Involvement of PhI(OAc)2 on CMD Pathways for the Intramolecular C(sp3)-H Activation
Peng-Yu Liu1,2, Yuehui Xu1,3, Xin Peng1,3
1State Key Laboratory of Fine Chemicals, Ningbo Institute of Dalian University of Technology, No.26 Yucai Road, Ningbo 315016, China.
Abstract:
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.
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