Pd催化的配体导向C-H键乙酰化反应的理论研究

Theoretical Study of Palladium-Catalyzed Ligand-Directed C—H Acetoxylation

Pd催化的配体导向C—H键官能化反应已经成为有机化学中一种重要的合成手段.我们用B3PW91密度泛函方法研究了Pd催化的配体导向C—H键乙酰化反应中催化剂和底物配合步骤以及C—H键活化步骤中的热力学性质.研究发现,具有不同导向基团的反应物之间竞争反应的选择性取决于导向基团与Pd(OAc)2的配合步骤,配合反应稳定常数大的较容易生成乙酰化的产物.另一方面,反应的选择性与C—H键的活化步骤无关,并且与导向基团的配位原子的气相碱性、原子上的电荷密度以及最高占据轨道能量都没有相关性.

Pd-Catalyzed ligand-directed C—H functionalization has become one of the most important synthetic methods in organic chemistry. A theorecical study with the B3PW91 density functional theory method is carried out on Pd-catalyzed ligand-directed C—H acetoxylation. The thermodynamic properties in substrates binding step and C—H activation step are calculated. The data indicate that the selectivity of competition reactions between substrates with different directed group is determined by the substrates binding step. A larger complex stability constant will facilitate the formation of the corresponding product. However, the C—H activation step is unrelated to the reaction selectivity. Furthermore, no correlation is found between the reaction selectivities and the gas-phase basicities, Mulliken charges or HOMO energies of the directed groups.