A self-threaded "molecular 8".
A self-threaded "molecular 8".
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自螺纹“8号分子”。
DOI：
10.1002/1521-3765(20010417)7:8
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
F. Vögtle*
中科院分区：
文献类型：
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作者：
Carin Reuter;W. Wienand;Carsten Schmuck;F. Vögtle*
以轮轴和轮轴各含一个磺胺基的[2]轮烷为起始原料，一步合成得到了一种新型的含有两个脂肪族桥的[1]轮烷，产率为39%。首先在这些磺胺氮上进行温度控制的化学选择取代反应，然后在轮轴上的各种其他羧胺氮上进行化学选择取代反应，形成三种双桥[1]轮烷的异构体混合物，可以通过HPLC分离。通过核磁共振实验和分子模拟计算，可以确定主要产物3a的结构。在不同的反应条件下，可以分离出一个双取代但尚未桥接的[2]轮烷4作为中间体，进一步证明了3a的指定结构及其形成方式。这种双桥[1]轮烷3a的形状让人想起一个自缠绕的手性“分子8”，其中任何可能的外消旋作用都被来自前轮烷轴的两个止动器所阻碍。因此，据我们所知，这是第一个分子的两个概念，环对映异构和螺旋手性，在一个结构中实现的例子。采用手性固定相进一步高效液相色谱法分离了主要产物的对映体。圆形二谱图的棉花效应不同于已合成的在轴和轮之间只有一个脂肪桥的[1]轮烷。
A new type of [1]rotaxanes containing two aliphatic bridges between axle and wheel is obtained in 39% yield in a one-step synthesis starting from a [2]rotaxane which contained one sulfonamide group each in both the wheel and the axle. Temperature controlled chemoselective substitution reactions first at these sulfonamide nitrogens and then subsequently at the various other carboxamide nitrogens in the wheel and axle give rise to the formation of an isomeric mixture of three double-bridged [1]rotaxanes which could be separated by HPLC. Structure determination of the main product 3a was possible by NMR experiments supported by molecular modeling calculations. Using different reaction conditions, a double-substituted but not yet bridged [2]rotaxane 4 could be isolated as an intermediate giving further evidence for the assigned structure of 3a and the way of its formation. The shape of this double-bridged [1]rotaxane 3a reminds of a self-intertwining chiral "molecular 8", in which any possible racemization due to deslipping is hindered by the two stoppers originating from the former rotaxane axle. Hence, to the best of our knowledge this is the first example of a molecule in which both concepts, cycloenantiomerism and helical chirality, are realised in one structure. Enantiomer separation of the main product was possible by further HPLC using chiral stationary phases. The Cotton effects of the circular dichrograms are different to those of the already synthesized [1]rotaxanes bearing just one aliphatic bridge between axle and wheel.