作者:Yuhui Kou、Derong Cao、Hongqi Tao、Lingyun Wang、Jianquan Liang、Zhizhao Chen、Herbert Meier
DOI:10.1007/s10847-012-0242-5
日期:2013.12
A detailed study of the reaction conditions revealed that a quantitative cyclocondensation of 1,4-dialkoxy-2,5-bis(alkoxymethyl)-benzenes to pillar[n]arenes can be achieved by catalysis of p-toluenesulfonic acid in CH2Cl2. Major product of this new reaction is in each case a cyclopentamer (n = 5), but small amounts of the pillar[n]arenes with n = 6, 7 and 10 can be obtained as well. Different alkoxy groups in 1- and 4-position lead to regioisomers. All cyclooligomers exist in pillar structures as pair of enantiomers, which show a racemisation at room temperature, which is fast in terms of the NMR time scale. The racemisation process occurs by rotation of the 1,4-phenylene segments in the macrocyclic rings. Pillar[n]arenes exhibit novel host–guest behavior.
对反应条件的详细研究表明,在对甲苯磺酸在 CH2Cl2 中的催化作用下,可以将 1,4-二烷氧基-2,5-双(烷氧基甲基)苯定量环缩合为柱[n]烷。这种新反应的主要产物都是环五聚物(n = 5),但也可以得到少量 n = 6、7 和 10 的柱[n]烷。1 位和 4 位上的烷氧基不同,会产生区域异构体。所有环醇异构体都以一对对映体的形式存在于柱状结构中,在室温下会发生消旋化,从核磁共振时间尺度来看,消旋化速度很快。外消旋过程是通过大环中的 1,4-亚苯基段旋转而发生的。柱[n]烷表现出新颖的宿主-宾客行为。