C–F bond arylation of fluoroarenes catalyzed by Pd0 phosphine complexes: theoretical insight into regioselectivity, reactivity, and prediction of ligands,Organic Chemistry Frontiers

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C–F bond arylation of fluoroarenes catalyzed by Pd0 phosphine complexes: theoretical insight into regioselectivity, reactivity, and prediction of ligands
Organic Chemistry Frontiers ( IF 4.6 ) Pub Date : 2019-11-05 , DOI: 10.1039/c9qo01095e
Rong-Lin Zhong _{1,

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Affiliation

Palladium-catalyzed C–F bond arylation of pentafluorobenzene was theoretically investigated as an example of aryl–F bond functionalization. DFT computations show that C3-regioselective arylation of pentafluorobenzene occurs more favorably than C1 and C2-ones as reported experimentally, through oxidative addition of the C–F bond to Pd⁰ species, transmetalation and reductive elimination of the C–C bond. Oxidative addition of the C–F bond is the rate-determining and regioselectivity-determining step. The lower energy transition state of the oxidative addition of the C3–F bond (TS-C3) arises from a larger stabilization energy between Pd⁰(BrettPhos) and distorted pentafluorobenzene moieties in TS-C3 than those in TS-C1 and TS-C2. The larger stabilization energy is a result of a lower σ* orbital energy of the distorted C3–F bond than those of C1–F and C2–F bonds, which leads to a larger charge transfer from the Pd dπ orbital to the σ* orbital of the C3–F bond. The results suggest that both σ* orbital energy and bond dissociation energy are important factors for determining the reactivity of the C–F bond. Also, the activation barriers of the C–F bond with different substitution groups follow the order: NO₂ < COOMe < CN ∼ CF₃ < F, which is approximately consistent with the order of electron-withdrawing ability of these groups. It is theoretically predicted here that NMe₂-substituted BrettPhos is better for C–F bond cleavage than BrettPhos, where three NMe₂ groups are introduced to BrettPhos instead of the isopropyl groups.

中文翻译：

Pd0膦配合物催化氟代芳烃的CF键芳基化：区域选择性，反应性和配体预测的理论见解

理论上研究了钯催化的五氟苯的C-F键芳基化，作为芳基-F键功能化的一个例子。DFT计算表明，通过实验报道的五氟苯的C3-区域选择性芳基化比C1和C2-一个更有利，这是通过将C-F键氧化添加到Pd ⁰物种，金属转移和C-C键的还原消除而实现的。C–F键的氧化加成是决定速率和决定区域选择性的步骤。氧化加成的C3-F键（的下能量过渡态TS-C3）选自Pd之间的较大的稳定化能产生⁰中（BrettPhos）和失真五氟苯基部分TS-C3比在TS-C1和TS-C2。较大的稳定能是由于C3-F键畸变的σ*轨道能量比C1-F和C2-F键的低，从而导致更大的电荷从Pddπ轨道转移到σ*轨道C3-F键的基团。结果表明，σ*轨道能和键解离能都是决定CF键反应性的重要因素。同样，具有不同取代基的C–F键的激活势垒遵循以下顺序：NO ₂ <COOMe <CN〜CF ₃ <F，这与这些基团的吸电子能力顺序基本一致。从理论上讲，NMe ₂取代BrettPhos的CF键断裂效果要好于BrettPhos，后者将三个NMe ₂基团引入异丙基而不是BrettPhos。

更新日期：2019-11-05

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