Rad transition: The combination of transition‐metal‐catalyzed CHactivation and a NHPI‐initiated radical process is essential for the title transformation. The neutral conditions and the ideal oxidant, molecular oxygen, make this hydroxylation environmentally friendly and practical. NHPI=N‐hydroxyphthalimide.
Herein we present a Pd-catalyzeddirectC–H hydroxylation of 2-arylpyridines using molecular oxygen (O2) as the sole oxidant. The key aspects of the method include: (a) the activation of molecular oxygen with a nontoxic and inexpensive aldehyde; (b) an efficient association of the in situ-generated acyl peroxo radical with palladium catalysis; and (c) convenient operating conditions. On the basis of
本文中,我们介绍了使用分子氧(O 2)作为唯一氧化剂的Pd催化2-芳基吡啶的直接C–H羟基化反应。该方法的关键方面包括:(a)用无毒且廉价的醛活化分子氧;(b)原位产生的酰基过氧自由基与钯催化的有效结合;(c)方便的操作条件。基于一系列对照实验中获得的结果,涉及Pd II / Pd IV催化循环的转化。此外,该方法可容易地以良好的分离产率获得广泛范围的取代的2-(吡啶-2-基)苯酚。
Metallaphotoredox-Mediated C<sub>sp2</sub>–H Hydroxylation of Arenes under Aerobic Conditions
作者:Sk. Sheriff Shah、Amrita Paul、Manoranjan Bera、Yarra Venkatesh、N. D. Pradeep Singh
DOI:10.1021/acs.orglett.8b01973
日期:2018.9.21
The direct hydroxylation of 2-arylpyridines and 2-arylbenzothiazoles via the merger of organic photoredox and metal catalysis is reported where 4CzIPN is used as the visible-light photocatalyst and Pd(OAc)2 as the metal catalyst. This method has been employed to synthesize organic molecules exhibiting excited-stateintramolecularprotontransfer properties for generating tunable luminescence responses
A visible-light-induced strategy for the synthesis of phenolic compounds was developed throughpalladium-catalyzed CH hydroxylation of aromatics with nitrogen-heterocyclic as the directing group and hydrogen peroxide as hydroxylation reagent. Diverse (hetero)arenes with nitrogen-heterocyclic directing groups can be utilized for the ortho CH hydroxylation under mild reaction conditions, and a series
通过钯催化芳烃的 C H 羟基化,以氮杂环为导向基团,过氧化氢为羟基化试剂,开发了一种可见光诱导的酚类化合物合成策略。具有氮杂环导向基团的多种(杂)芳烃可在温和的反应条件下用于邻位CH羟基化,并以良好的收率合成了一系列酚类化合物。该方案具有良好的官能团耐受性和广泛的底物范围,已成功应用于天然产物卡波霉素和药物地拉罗司的合成。根据实验结果和文献调查,光诱导 C 的激进机制提出了 H 羟基化。该方案为通过CH键活化羟基化制备酚类化合物提供了一种新的解决方案。
Palladium-Catalyzed Aryl C(sp<sup>2</sup>)–H Bond Hydroxylation of 2-Arylpyridine Using TBHP as Oxidant
作者:Jiawei Dong、Ping Liu、Peipei Sun
DOI:10.1021/acs.joc.5b00167
日期:2015.3.6
An efficient synthesis of phenols via Pd-catalyzed, pyridyl-directed homogeneous hydroxylation of the aryl C-H bond was developed, in which tert-butyl hydroperoxide was used as the sole oxidant. The method had a broad group tolerance and was available for both electron-rich and electron-deficient substrates. The reaction of a series of 2-arylpyridine derivatives gave the ortho-hydroxylation products in moderate to good yields.