Organocatalytic synthesis of densely functionalized oxa-bridged 2,6-epoxybenzo[<i>b</i>][1,5]oxazocine heterocycles
作者:Ramani Gurubrahamam、Koppanathi Nagaraju、Kwunmin Chen
DOI:10.1039/c8cc02565g
日期:——
Metal-free addition of salicylhydrazones to electron deficient internal alkynes catalyzed by 1,4-diazabicyclo[2.2.2]octane (DABCO) to yield oxa-bridged 2,6-epoxybenzo[b][1,5]oxazocine heterocycles was achieved. The demonstrated protocol proceeds through an o-quinone methide formation, aza-Michael addition, stereoselective protonation, enamine promoted aromatization, O,O-acetalization and O,N-aminalization
实现了在1,4-二氮杂双环[2.2.2]辛烷(DABCO)催化下,将水杨酰肼无金属加成至缺电子的内部炔烃中,从而生成氧杂桥联的2,6-环氧苯并[ b ] [1,5]恶唑啉杂环。所证明的方案通过邻醌甲基化物的形成,氮杂-迈克尔加成,立体选择性质子化,烯胺促进的芳构化,O,O-乙缩醛化和O,N-酰胺化序列进行,以高产率提供具有高非对映选择性的特权杂环。