One-pot reductive coupling of N-acylcarbamates with activated alkenes: application to the asymmetric synthesis of pyrrolo[1,2-a]azepin-5-one ring system and (−)-xenovenine
作者:Xue-Kui Liu、Xiao Zheng、Yuan-Ping Ruan、Jie Ma、Pei-Qiang Huang
DOI:10.1039/c1ob06697h
日期:——
cyclic N-acylcarbamates can be used as stable substrates, and a range of activated alkenes serve as effective radical receptors. The reductive coupling of l-N-acylcarbamates 12/13 gave 2,5-disubstituted pyrrolidine derivatives in high trans-diastereoselectivities. The reductive coupling with penta-2,4-dienoate proceeded exclusively in a 1,6-addition fashion, producing a single non-conjugated E-isomer
描述了N-酰基氨基甲酸酯与活化的烯烃的一锅还原还原。该方法基于用DIBAL-H部分还原N-酰基氨基甲酸酯,然后形成N-酰基亚胺离子和SmI(2)介导的与活化烯烃的自由基偶联。无环和环状N-酰基氨基甲酸酯均可用作稳定的底物,并且一系列活化的烯烃可用作有效的自由基受体。1N-酰基氨基甲酸酯的还原偶联以高反式非对映选择性产生2,5-二取代的吡咯烷衍生物。与2,4-戊二酸五酯的还原偶联仅以1,6-加成方式进行,产生单个非共轭的E-异构体。在此方法的基础上,三步构建了吡咯并[1,2-a]氮杂环庚烷-5-酮16,该骨架是许多茎类生物碱和来咪唑定生物碱的骨架,