Mechanism, Reactivity, and Selectivity in Rh(III)-Catalyzed Phosphoryl-Directed Oxidative C-H Activation/Cyclization: A DFT Study
Mechanism, Reactivity, and Selectivity in Rh(III)-Catalyzed Phosphoryl-Directed Oxidative C-H Activation/Cyclization: A DFT Study
复制标题
Rh(III) 催化的磷酰基氧化 C-H 活化/环化的机制、反应性和选择性：DFT 研究
DOI：
10.1021/jo500616g
复制
发表时间：
2014-06-06
影响因子：
3.6
通讯作者：
Zhao, Yufen
中科院分区：
文献类型：
--
作者：
Liu, Liu;Wu, Yile;Zhao, Yufen
采用密度泛函理论（DFT）研究了Rh（III）催化的磷酰基导向的C-H氧化活化/环化反应的详细机理，包括C-H活化、炔插入、还原消除和催化剂回收四个基本步骤，每个步骤由不同的步骤组成.有趣的是，与Rh（III）-Ag 2CO 3体系相比，发现Rh（III）-AgOAc催化剂体系在C-H活化步骤中更有利，而Rh（I）-Ag 2 O3催化剂体系对于催化剂再循环更有效。重要的是，我们的计算表明，炔插入过程是一个可逆的步骤。还原消除是速率控制步骤，活化能为25.0 kcal/mol。此外，通过比较DFT计算，探讨了二芳基乙炔和二烷基乙炔或富电子和缺电子二芳基乙炔之间的反应性和选择性差异的来源。计算结果表明，炔的电子效应对反应活性和选择性起着关键作用，这与实验观察到的二芳基乙炔和富电子二芳基乙炔的反应活性分别比二烷基乙炔和缺电子二芳基乙炔高一致.我们的研究结果将有助于过渡金属催化的C-H活化反应的进一步发展。
Density functional theory calculations (DFT) have been performed on Rh(III)-catalyzed phosphoryl-directed oxidative C-H activation/cyclization to investigate the detailed mechanism, including four basic steps: C-H activation, alkyne insertion, reductive elimination, and catalyst recycling, each of which consists of different steps. Interestingly, the Rh(III)-AgOAc catalyst system was found to be more favorable in the C-H activation step in comparison with the Rh(III)-Ag2CO3 system, whereas the Rh(I)-Ag2O3 catalyst system was more efficient for catalyst recycling. Importantly, our calculations suggest that the alkyne insertion process is a reversible step. Reductive elimination is the rate-determining step with an activation energy of 25.0 kcal/mol. In addition, the origin of the reactivity and selectivity difference between diarylacetylenes and dialkylacetylenes or electron-rich and electron-deficient diarylacetylenes was probed by means of comparative DFT calculations. The calculation results show that the electronic effects of alkynes play a key role in the reactivity and selectivity, in line with the experimental observations that diarylacetylenes and electron-rich diarylacetylenes are more reactive than dialkylacetylenes and electron-deficient diarylacetylenes, respectively. Our findings should be useful for further developments of transition-metal-catalyzed C-H activation reactions.