实验性13 C 动力学同位素效应 (KIE) 为有机光氧化还原催化实现的三种分子间反马尔可夫尼科夫烯烃加氢官能化反应——加氢酯化、加氢胺化和加氢醚化提供了前所未有的机理洞察力。发现所有三个反应都是通过模型烯烃的初始氧化形成自由基阳离子中间体,然后进行连续的亲核攻击和氢原子转移以提供加氢官能化产物。经历亲核攻击的烯烃碳上的正常13 C KIE 为所有三个反应中的限速亲核攻击提供了定性证据。与预测13的比较从该步骤的密度泛函理论 (DFT) 计算获得的 C KIE 值表明,烯烃氧化在加氢酯化和加氢胺化中具有部分限速影响,而亲核攻击仅在加氢醚化反应中限速。碱性添加剂(2,6-二甲基吡啶)通过去质子化激活亲核试剂,并且是对自由基阳离子进行亲核攻击的过渡态的组成部分,为开发这些反应的不对称版本提供了重要的设计原则。更富电子的吡啶碱基(2,6-二甲氧基吡啶)在分子间和分子内氢化反应中表现出相当大的速率增强。
作者:Andranik Petrosyan、Luisa Zach、Tobias Taeufer、T. S. Mayer、Jabor Rabeah、Jola Pospech
DOI:10.1002/chem.202201761
日期:2022.10.12
Pyrimidopteridine organic photoredox catalysts are applied in a formal addition of carboxylic acids to activated alkenes as a dual photoredox and hydrogen atom transfer catalysts. Electron-rich alkenes counter the decarboxylation of carboxylic acids upon single-electron oxidation and a selective hydroacetoxylation is observed.
Direct Catalytic Anti-Markovnikov Addition of Carboxylic Acids to Alkenes
作者:Andrew J. Perkowski、David A. Nicewicz
DOI:10.1021/ja4057294
日期:2013.7.17
A direct catalytic anti-Markovnikov addition of carboxylic acids to alkenes is reported. The catalyst system is comprised of the Fukuzumi acridinium photo-oxidant (1) and a substoichiometric quantity of a hydrogen-atom donor. Oxidizable olefins, such as styrenes, trisubstituted aliphatic alkenes, and enamides, can be employed along with a variety of carboxylic acids to afford the anti-Markovnikov addition adducts exclusively. A deuterium-labeling experiment lends insight to the potential mechanism.