The Origins of Dramatic Differences in Five-Membered vs Six-Membered Chelation of Pd(II) on Efficiency of C(sp3)-H Bond Activation

作者：Yang, Yun-Fang; Chen, Gang; Hong, Xin; Yu, Jin-Quan^*; Houk, K. N.^*

来源：Journal of the American Chemical Society, 2017, 139(25): 8514-8521.

DOI：10.1021/jacs.7b01801

• C-H ACTIVATION
• AB-INITIO PSEUDOPOTENTIALS
• EFFECTIVE CORE POTENTIALS
• TRANSITION-ELEMENTS
• POLARIZATION FUNCTIONS
• DENSITY FUNCTIONALS
• PALLADIUM ACETATE
• BASIS-SETS
• ARYLATION
• CHEMISTRY

The origin of the unique effectiveness of six-membered chelates on the beta-methylene C(sp3)-H activation reactions by Pd(II) catalyst was explained with density functional theory. The Pd(II) catalysts that involve five-membered chelates are inactive in this transformation. Computational studies suggest that the C(sp3)-H bond activation is the rate-limiting step in both cases. The C(sp3)-H bond activation with a five-membered chelate is unfavorable by 7.7 kcal/mol compared to the corresponding six-membered chelate with Pd(II). Two factors cause the difference: (1) the dimeric Pd species with five-membered chelation square-planar structure is more stable than that with six-membered chelation by 2.0 kcal/mol; (2) steric repulsion between the ArF group of the substrate and the quinoline group of the acetyl-protected aminomethyl quinoline ligand destabilizes the five-membered chelate transition structure by 5.7 kcal/mol. The six-membered chelate of Pd(II) with an acetyl-protected aminoethyl quinoline ligand orients the ligand away from the ArF group of the substrate and alleviates the steric repulsion.

• 出版日期2017-6-28
• 单位浙江大学