Intramolecular (4+2) cycloaddition of aryl-1-aza-2-azoniaallene salts: a practical approach to highly sterically-congested polycyclic protonated azomethine imines
作者:Ram C. Dhakal、Matthias Brewer
DOI:10.1016/j.tet.2016.03.037
日期:2016.6
containing a 1,2,3,4-tetrahydrocinnoline scaffold in high yield. This sequence involves the oxidation of aryl hydrazones with TFAA-activated DMSO to give the corresponding α-trifluoroacetoxyazo products, which react readily with TMSOTf to give 1-aza-2-azoniaallene salt intermediates that undergo intramolecular (4+2) cycloadditions with pendent alkenes. This reaction sequence is more general, more practical
我们报告了一种改进的两步反应顺序,该顺序以高产率产生含有 1,2,3,4-四氢肉啉支架的三环质子化偶氮甲碱亚胺产物。该序列涉及用 TFAA 活化的 DMSO 氧化芳基腙,得到相应的 α-三氟乙酰氧基偶氮产物,该产物很容易与 TMSOTf 反应,得到 1-aza-2-azoniaallen 盐中间体,该中间体与悬垂烯烃进行分子内 (4+2) 环加成。该反应顺序比我们最初报道的方法更通用、更实用、更环保。环加成以高产率提供了异常空间位阻的产物。