Metal-Free Cross-Dehydrogenative C-O Coupling of Carbonyl Compounds with N-Hydroxyimides: Unexpected Selective Behavior of Highly Reactive Free Radicals at an Elevated Temperature.,The Journal of Organic Chemistry

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Metal-Free Cross-Dehydrogenative C-O Coupling of Carbonyl Compounds with N-Hydroxyimides: Unexpected Selective Behavior of Highly Reactive Free Radicals at an Elevated Temperature.
The Journal of Organic Chemistry ( IF 3.3 ) Pub Date : 2020-01-13 , DOI: 10.1021/acs.joc.9b02656
Igor B Krylov ₁ , Elena R Lopat'eva _{1,

2} , Alexander S Budnikov _{1,

2} , Gennady I Nikishin ₁ , Alexander O Terent'ev ₁

Affiliation

Cross-dehydrogenative C-O coupling of N-hydroxyimides with ketones, esters, and carboxylic acids was achieved employing the di-tert-butyl peroxide as a source of free radicals and a dehydrogenating agent. The proposed method is experimentally simple and demonstrates the outstanding efficiency for the challenging CH substrates, such as unactivated esters and carboxylic acids. It was shown that N-hydroxyphthalimide drastically affects the oxidative properties of t-BuOOt-Bu by intercepting the t-BuO• radicals with the formation of phthalimide-N-oxyl radicals, a species responsible for both hydrogen atom abstraction from the CH reagent and the selective formation of the C-O coupling product by selective radical cross-recombination. The practical applicability of the developed method was exemplified by the single-stage synthesis of commercial reagent (known as Baran aminating reagent precursor) from isobutyric acid and N-hydroxysuccinimide, whereas in the standard synthetic approach, four stages are necessary.

中文翻译：

羰基化合物与N-羟基酰亚胺的无金属交叉脱氢CO偶联：高反应性自由基在高温下的意外选择行为。

N-羟基酰亚胺与酮，酯和羧酸的交叉脱氢CO偶联是通过使用二叔丁基过氧化物作为自由基源和脱氢剂来实现的。所提出的方法在实验上很简单，并且证明了对于具有挑战性的CH底物（例如未活化的酯和羧酸）具有出色的效率。结果表明，N-羟基邻苯二甲酰亚胺通过拦截t-BuO•自由基而形成邻苯二甲酰亚胺-N-氧基自由基，从而极大地影响t-BuOOt-Bu的氧化性能。通过选择性自由基交叉重组选择性形成CO偶联产物。

更新日期：2020-01-14

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