Electrocatalytic synthesis of α,α-gem-dihalide ketones from α-mono-halide ketones and unexpected dimer condensation,Green Chemistry

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Electrocatalytic synthesis of α,α-gem-dihalide ketones from α-mono-halide ketones and unexpected dimer condensation
Green Chemistry ( IF 9.3 ) Pub Date : 2022-03-09 , DOI: 10.1039/d1gc04584a
Bei Zhou _{1,

2} , Yu-Juan He ₁ , Yun-Feng Tao ₁ , Lan-Xiang Liu ₂ , Min Hu _{1,

2} , Zu-Hui Chang ₁ , Hong Lei ₁ , Jun Lin ₂ , Tong Lin ₃ , Guan-Ben Du ₁

Affiliation

A novel, environmentally friendly electrocatalytic process has been developed to prepare α,α-gem-dihalide (F, Cl, and Br) ketones from α-mono-halide ketones in an aqueous solution containing alkali halide salts. The gem-dihalides could have the same or different halogens on the same carbon, depending on the reactant and inorganic halide salt used. An electron-withdrawing group, such as carbonyl, located at the α-site of mono-halogenated carbon, was essential to the reaction. The electrosyntheses were performed under ambient conditions without inert gas protection and displayed yields of about 80%. This method avoided the classical haloform elimination reaction. However, when the aqueous solution contained NaOH, two α-mono-halide ketone molecules had a special dimer condensation. The reaction mechanisms were explored by conducting GC-MS, EPR, and CV with DFT calculations. These revealed that in situ generation of a halogen radical initiated electrocatalytic halogenation, while the dimer condensation involved a hydroxyl radical-mediated C1 fragment elimination.

中文翻译：

α-单卤化物酮电催化合成α,α-二卤化物酮和意想不到的二聚体缩合

已经开发了一种新颖的、环境友好的电催化工艺，以在含有碱金属卤化物盐的水溶液中从 α-单卤化物酮制备 α,α-偕二卤化物（F、Cl 和 Br）酮。宝石_-二卤化物可以在相同的碳上具有相同或不同的卤素，这取决于所使用的反应物和无机卤化物盐。位于单卤代碳的α位的吸电子基团，如羰基，对反应至关重要。电合成在没有惰性气体保护的环境条件下进行，产率约为 80%。该方法避免了经典的卤仿消除反应。然而，当水溶液中含有NaOH时，两个α-单卤酮分子发生了特殊的二聚体缩合。通过使用 DFT 计算进行 GC-MS、EPR 和 CV 来探索反应机制。这些揭示了现场卤素自由基的产生引发了电催化卤化，而二聚体缩合涉及羟基自由基介导的 C1 片段消除。

更新日期：2022-03-09

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