Synthesis of Flavonols via Pyrrolidine Catalysis: Origins of the Selectivity for Flavonol versus Aurone
作者:Wei Xiong、Xiaohong Wang、Xianyan Shen、Cuifang Hu、Xin Wang、Fei Wang、Guolin Zhang、Chun Wang
DOI:10.1021/acs.joc.0c01869
日期:2020.10.16
method for flavonol from 2′-hydroxyl acetophenone and benzaldehyde promoted by pyrrolidine under an aerobic condition in water is established. This protocol was supported by efficient synthesis of 44 common examples and three natural products. The α, β-unsaturated iminium ion (enimine ion E) was proved to be the key intermediate in the reaction. H218O and 18O2 isotope tracking experiments demonstrated
建立了一种在水中好氧条件下由吡咯烷促进的2'-羟基苯乙酮和苯甲醛合成黄酮醇的新方法。该协议得到44个常见实例和三种天然产物的有效合成的支持。事实证明,α,β-不饱和亚胺离子(亚胺离子E)是反应的关键中间体。H 2 18 O和18 O 2同位素跟踪实验表明,水和好氧气氛对于确保转化都必不可少。黄酮醇或金酮的选择性源自溶剂触发的中间体,该中间体由分离的亚胺的紫外可见光谱确定。酚亚胺EA在水中占主导地位,酮烯胺中间体EB在乙腈中盛行。在环化和[2 + 2]氧化的关键步骤之后,在吡咯烷和氧的存在下,EA通过EI(两性离子样的酚氧基亚胺离子)通过EI生成黄酮醇。EB通过路径II进行,这是由EB与吡咯烷和氧气共同光解而引发的自由基过程,从而生成金酮。初步的机械研究报道。