Paracyclophanes: Extending the Bridges. Reactions
作者:Zissis Pechlivanidis、Henning Hopf、Jörg Grunenberg、Ludger Ernst
DOI:10.1002/ejoc.200800748
日期:2009.1
n]Paracyclophanes with bridges of equal and unequal length (m,n ≤ 4) undergo electrophilic aromatic substitution (Friedel–Crafts acylation, bromination) under very mild conditions as long as the bridge contains less than four atoms. Whenever there is a choice, the aromatic ring is attacked at the position closest to the shorter alkano bridge, which indicates that the transannular benzene moiety acts as
[mn]具有等长和不等长桥(m,n ≤ 4)的对环芳烃在非常温和的条件下进行亲电芳香取代(弗里德尔-克拉夫茨酰化,溴化),只要桥包含少于四个原子。每当有选择时,芳环就会在最靠近较短链烷烃桥的位置受到攻击,这表明跨环苯部分充当相邻基团。通过溴化获得的乙酰基衍生物和由其衍生的酸和酯,将第二个取代基引入到假偶合位置,即直接与导向基团相对。然而,这种效应仅在那些相邻桥的长度不超过三个原子的[mn]phanes 中观察到。对于丁醇桥接衍生物,区域选择性完全丧失。对于在一个苯环上带有两个酯取代基的 [mn] 对环芳,观察到非常相似的结果,限制情况是 [4.3] 对环芳衍生物。我们建议取代基的立体控制效应只能在环内距离低于 4 A 时发生。 (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)