Electroreductive Intermolecular Coupling of Coumarins with Benzophenones: Synthesis of 4-(2-Hydroxyphenyl)-5,5-diaryl-γ-butyrolactones, 2-(2,2-Diaryl-2,3-dihydrobenzofuran-3-yl)acetic Acids, and 4-(Diarylmethyl)coumarins
作者:Naoki Kise、Yusuke Hamada、Toshihiko Sakurai
DOI:10.1021/acs.joc.6b02056
日期:2016.11.18
4-position of coumarins as trimethylsilyl ethers. From 3-methylcoumarin, 3,4-cis-adducts were formed stereoselectively. The de-trimethylsilylation of the adducts with 1 M HCl aq or TBAF in THF at 25 °C produced 4-(2-hydroxyphenyl)-5,5-diaryl-γ-butyrolactones. The γ-butyrolactones were further transformed to 2-(2,2-diaryl-2,3-dihydrobenzofuran-3-yl)acetic acids by treatment with 1 M HCl aq at reflux temperature
在TMSC1的存在下,香豆素与二苯甲酮的电还原偶联使加合物在香豆素的4位反应为三甲基甲硅烷基醚。由3-甲基香豆素立体选择性地形成3,4-顺式加合物。在25°C下用1 M HCl水溶液或TBAF在THF中对加合物进行脱三甲基甲硅烷基化反应,生成4-(2-羟苯基)-5,5-二芳基-γ-丁内酯。通过在回流温度下用1M HCl水溶液处理,将γ-丁内酯进一步转化为2-(2,2-二芳基-2,3-二氢苯并呋喃-3-基)乙酸。用1M HCl的MeOH溶液使加合物进行脱三甲基甲硅烷基化反应,得到2-(2,2-二芳基-2,3-二氢苯并呋喃-3-基)乙酸甲酯。加合物的脱三甲基甲硅烷氧基化或γ-丁内酯的脱水产生了4-(二芳基甲基)香豆素。