Hybrid [n]Arenes through Thermodynamically Driven Macrocyclization Reactions
Hybrid [n]Arenes through Thermodynamically Driven Macrocyclization Reactions
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DOI：
10.1021/acs.joc.5b00099
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发表时间：
2015-04-03
影响因子：
3.6
通讯作者：
Szumna, Agnieszka
中科院分区：
文献类型：
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作者：
Boinski, Tomasz;Cieszkowski, Artur;Szumna, Agnieszka
杂化[n]芳烃是一类由不同烷氧苯单元组成的中型大环化合物，由Bronsted酸（三氟乙酸）催化的两种不同的烷氧苯与甲醛进行简单的一锅直接缩合得到。我们已经证明，在Bronsted酸催化下，该反应是可逆的，因此受产物的相对稳定性控制。主要的大环产物是由四个[2 + 2]或[3 + 1]的烷氧苯单元组成的杂化[n]芳烃。然而，作为1,4-二甲氧基苯、1,3,5-三甲氧基苯与甲醛缩合的主要产物，也得到了一个不寻常的[3 + 2]杂化大环。以柱状[5]芳烃和过o -甲基化间苯二甲酸[4]芳烃为原料，进一步验证了杂化产物的稳定性和反应的可逆性。加扰实验得到的杂化大环的产率可与缩合反应相媲美。杂化[n]芳烃的核磁共振波谱和x射线结构表明，1,2-和1,3-二氧苯单元是大环的柔性部分。然而，1,4-二氧基苯单元表现出相当大的空间位阻，由于抑制旋转导致形成异构体和固有的手性大环。测定了其对各种有机阳离子的识别性能。在[3 + 2]杂化大环中观察到n -甲基吡啶阳离子的高度选择性识别。
Hybrid [n]arenes, the class of medium-sized macrocyclic compounds consisting of different alkoxybenzene units, were obtained by a simple, one-pot, direct condensation of two different alkoxybenzenes with formaldehyde catalyzed by a Bronsted acid (trifluoroacetic acid). We have shown that, under Bronsted acid catalysis, this reaction is reversible and therefore governed by the relative stability of the products. The main macrocyclic products are hybrid [n]arenes consisting of four alkoxybenzene units of [2 + 2] or [3 + 1] stoichiometry. However, an unusual [3 + 2] hybrid macrocycle was also obtained as a main product of the condensation between 1,4-dimethoxybenzene, 1,3,5-trimethoxybenzene, and formaldehyde. The stability of the hybrid products and the reversibility of the reaction were further confirmed by a scrambling experiment, involving pillar[5]arene and per-O-methylated resorcin[4]arene. The scrambling experiment has given hybrid macrocycles in yields comparable with those obtained in condensation reactions. NMR spectra and X-ray structures of hybrid [n]arenes indicate that 1,2- and 1,3-dialkoxybenzene units are flexible parts of macrocyclic rings. However, the 1,4-dialkoxybenzene units present considerable steric hindrance, resulting in the formation of isomers and inherently chiral macrocycles due to inhibited rotation. The recognition properties toward various organic cations were also determined. Highly selective recognition of the N-methylpyridinium cation was observed for the [3 + 2] hybrid macrocycle.