一种黄明龙还原反应副产物产生的机理分析

Analysis of the mechanism of the by-product of Huang-Minlon reaction

芳基乙基酮类化合物在Wolff-Kishner-Huang还原反应过程中会产生副产物,随着底物共轭体系增大,副产物含量也相应增加,产品收率降低;通过1H NMR、13C NMR和LC-MS对副产物结构分析,证明其结构为二亚乙基肼,可能是共轭体系增加了中间体腙的氨基亲核性,从而与另一分子酮反应生成二亚乙基肼。实验结果表明,可通过改变碱的加入节点来避免该副产物的产生,水合肼加入量对反应也有影响。

In the Wolff-Kishner-Huang reaction,aryl acetophenone compounds will produce by-products.As size of theπ-conjugated system was increased,the yield of the corresponding by-products increased accordingly.The structure of by-product dithylene hydrazine was identified by 1H NMR,13C NMR and LC-MS.The nucleophilicity of the intermediate hydrazine might be enhanced by resonancing electron-releasing properties of the aryl group.Subsequently,the intermediate hydrazone reacted with aryl acetophenone to generated the by-product diethylhydrazine.The experimental results indicated that the generation of the by-product was avoided by changing the time of adding the base.