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。
Direct<i>ortho</i>-Hydroxylation of 2-Phenylpyridines using Palladium(II) Chloride and Hydrogen Peroxide
Direct functionalization of the ubiquitous CHbond is receiving much attention because complex structures can be formed from simple precursors. This paper reports a useful method for the direct hydroxylation of 2‐phenylpyridines using palladium(II) chloride and aqueous hydrogen peroxide. In this method, hydrogen peroxide, which has high atom efficiency, is employed as the oxidant and phenol derivatives
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.