Iminoxyl Radical-Based Strategy for Intermolecular C-O Bond Formation: Cross-Dehydrogenative Coupling of 1,3-Dicarbonyl Compounds with Oximes
Iminoxyl Radical-Based Strategy for Intermolecular C-O Bond Formation: Cross-Dehydrogenative Coupling of 1,3-Dicarbonyl Compounds with Oximes
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DOI：
10.1002/adsc.201400143
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发表时间：
2014-07-07
影响因子：
5.4
通讯作者：
Nikishin, Gennady I.
中科院分区：
文献类型：
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作者：
Krylov, Igor B.;Terent'ev, Alexander O.;Nikishin, Gennady I.
首次实现了1，3-二酮和1，3-酮酯与肟的交叉取代C-O偶联反应。反应在氧化剂[KMnO 4、Mn（OAc）（2）/KMnO 4、Mn（OAc）（3）中心点2 H（2）O、MnO 2、Mn（acac）（3）、Fe（ClO 4）（3）、Cu（ClO 4）（2）中心点6 H（2）O、Cu（NO3）（2）中心点2.5H（2）O和（NH 4）（2）Ce（NO3）（6）]的存在下进行。用高锰酸钾（KMnO_4）、二水合醋酸锰[Mn（OAc）（3）中心点2 H（2）O]或醋酸锰/高锰酸钾[Mn（OAc）（2）/KMnO_4]体系合成了20个交叉偶联产物，产率为27- 92%。合成可以很容易地放大到克量的目标产品。显然，该反应通过自由基机理进行，其中氧化剂用于从肟产生自由基并进行1，3-二羰基化合物的单电子氧化。通过电子自旋共振（ESR）光谱定量证实了肟自由基的形成。在本研究中描述的耦合是第一个例子的选择性分子间反应，涉及不稳定的亚氨氧基自由基原位生成。
Cross-dehydrogenative C-O coupling of 1,3-diketones and 1,3-keto esters with oximes was realized for the first time. The reaction proceeds in the presence of the oxidants [KMnO4, Mn(OAc)(2)/KMnO4, Mn(OAc)(3)center dot 2H(2)O, MnO2, Mn(acac)(3), Fe(ClO4)(3), Cu(ClO4)(2)center dot 6H(2)O, Cu(NO3)(2)center dot 2.5H(2)O, and (NH4)(2)Ce(NO3)(6)]. Twenty cross-coupling products were synthesized using potassium permanganate (KMnO4), manganese(II) acetate dihydrate [Mn(OAc)(3)center dot 2H(2)O], or the manganese(II) acetate/potassium permanganate [Mn(OAc)(2)/KMnO4] system; yields are 27-92%. The synthesis can be easily scaled up to gram quantities of the target products. Apparently, the reaction proceeds via a radical mechanism in which the oxidizing agent serves to generate radicals from oximes and perform the one-electron oxidation of 1,3-dicarbonyl compounds. The formation of oxime radicals was confirmed quantitatively by electron spin resonance (ESR) spectroscopy. The coupling described in the present study is the first example of the selective intermolecular reaction involving unstable iminoxyl radicals generated in situ.