化学
马尔科夫尼科夫法则
亲核细胞
烯烃
氢胺化
分子内力
脱质子化
亲核加成
光化学
催化作用
动力学同位素效应
过渡状态
速率决定步骤
烯丙基重排
药物化学
计算化学
有机化学
区域选择性
物理
离子
量子力学
氘
作者
Sharath Chandra Mallojjala,Victor O. Nyagilo,Stephanie A. Corio,Alafate Adili,Anuradha Dagar,Kimberly A Loyer,Daniel Seidel,Jennifer S. Hirschi
摘要
Experimental 13C kinetic isotope effects (KIEs) provide unprecedented mechanistic insight into three intermolecular anti-Markovnikov alkene hydrofunctionalization reactions─hydroesterification, hydroamination, and hydroetherification─enabled by organophotoredox catalysis. All three reactions are found to proceed via initial oxidation of the model alkenes to form a radical cation intermediate, followed by sequential nucleophilic attack and hydrogen-atom transfer to deliver the hydrofunctionalized product. A normal 13C KIE on the olefinic carbon that undergoes nucleophilic attack provides qualitative evidence for rate-limiting nucleophilic attack in all three reactions. Comparison to predicted 13C KIE values obtained from density functional theory (DFT) calculations for this step reveals that alkene oxidation has partial rate-limiting influence in hydroesterification and hydroamination, while the nucleophilic attack is solely rate-limiting in the hydroetherification reaction. The basic additive (2,6-lutidine) activates the nucleophile via deprotonation and is an integral part of the transition state for nucleophilic attack on the radical cation, providing an important design principle for the development of asymmetric versions of these reactions. A more electron-rich pyridine base (2,6-dimethoxypyridine) exhibits considerable rate enhancements in both inter- and intramolecular hydrofunctionalization reactions.
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