A series of macro-sized (16-24-membered) carbamoyloxa-bridged cyclophanes 3a-k was prepared by sequential inter- and intramolecular transesterifications of dimethyl m-xylylenedicarbamate with α,Ï-dihydroxy compounds 2a-k in good yields (15-74%) without the use of high-dilution techniques. Precursor 4 with lower reactivity cyclized selectively to the desired 1:1 coupling products catalyzed by SnCl2. The conformationally rigid m-xylylene template restricted the location of the two carbamoyloxa-bridges, which resulted in moderate binding affinities to the potassium cation. The binding ability of these carbamoyloxa-bridged cyclophanes was evaluated by the extraction study of aqueous alkali metal picrates, (log K a=3.6-4.0) with the formation of a 1:1 complex.
一系列宏观尺寸(16-24个成员)的
氨基氧桥联环
烷烃3a-k通过二甲基m-二
氨基苯二
甲酸酯与α,ω-二羟基化合物2a-k的顺序分子内和分子间转酯化反应以良好产率(15-74%)制备而成,无需高稀释技术。反应性较低的前体4在SnCl2催化下选择性环化形成所需的1:1偶联产物。构象上刚性的m-二
氨基苯模板限制了两个
氨基氧桥的位置,导致与
钾阳离子产生中等的结合亲和力。这些
氨基氧桥联环
烷烃的结合能力通过提取研究
水相碱
金属
重铬酸盐进行评估(log Kₐ=3.6-4.0),形成了1:1复合物。