Chromium-Salen Catalyzed Cross-Coupling of Phenols: Mechanism and Origin of the Selectivity
Chromium-Salen Catalyzed Cross-Coupling of Phenols: Mechanism and Origin of the Selectivity
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DOI：
10.1021/jacs.9b03890
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发表时间：
2019-06-26
影响因子：
15
通讯作者：
Kozlowski, Marisa C.
中科院分区：
文献类型：
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作者：
Nieves-Quinones, Yexenia;Paniak, Thomas J.;Kozlowski, Marisa C.
研究了在Cr-salen催化剂催化下的高化学选择性苯酚交叉偶联反应。动力学研究表明，Cr（III）氧化为Cr(V)是反应的速率决定步骤。此外，实验化学计量分析表明，高价Cr(V)是该过程的活性催化剂。发现反应的选择性是由碳-碳交叉偶联成键反应决定的，而不是由任何预配位物质决定的。与最低能量的均偶联途径相比，最低能量的交叉偶联途径在其过渡态中需要更少程度的电子重组。这一结果得到了化学计量学Cr(V)动力学、C-13动力学同位素效应和密度泛函理论（DFT）计算的支持。对该反应的全面了解使我们能够进行一般分析，以预测交叉偶联反应的区域选择性。
A highly chemoselective phenol cross-coupling reaction catalyzed by a Cr-salen catalyst was developed. Kinetic studies showed that the oxidation of Cr(III) to Cr(V) is the rate-determining step of the reaction. In addition, experimental stoichiometric analysis showed that a high valent Cr(V) species is the active catalyst for this process. The selectivity of the reaction was found to be determined by the cross-coupling carbon-carbon bond forming reaction, rather than any precoordination species. It appears that the lowest energy cross-coupling pathway requires a lesser degree of electronic reorganization in its transition state vs the lowest energy homocoupling pathway. This result was supported by stoichiometric Cr(V) kinetics, C-13 kinetic isotope effects, and density functional theory (DFT) calculations. The understanding of the full landscape of this reaction allowed us to develop a general analysis to predict the regioselectivity of the cross-coupling reaction.