Molecular receptors. Synthesis, X-ray crystal structures, and chemical properties of crown ethers bearing an intraannular phenolic group
Molecular receptors. Synthesis, X-ray crystal structures, and chemical properties of crown ethers bearing an intraannular phenolic group
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分子受体。
DOI：
10.1021/ja00295a024
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发表时间：
1985
影响因子：
15
通讯作者：
M. Parvez
中科院分区：
文献类型：
--
作者：
C. Browne;G. Ferguson;M. Mckervey;D. Mulholland;T. O'Connor;M. Parvez
已经合成了具有1，3-二甲苯基亚基和环内酚基的大环聚醚，以确定冠醚的邻近氧原子对环内取代基的化学行为的影响，以及相反地，取代基对大环的结合性质的影响。2，6-双（溴甲基）苯甲醚与三、四、五甘醇的钠盐进行威廉姆森合成，得到相应的15、18、21元冠醚苯甲醚，再用碘化锂在吡啶中脱甲基，分别得到15、18、21元冠醚酚6、7、8。发现这些酚的pAfa（H2 Q）为（6）10.7、（7）10.6和（8）10.5。测定了18-冠酚（7）及其对硝基衍生物（Id）和10的铵盐的晶体结构。7的晶体是正交晶系，空间群Pelf，晶胞中有四个分子，尺寸为a= 9.779（2）A，B= 18.943（3）A，c= 8.915（2）A。10的晶体为单斜晶系，空间群P2\c，晶胞中有四个分子，晶胞尺寸为a= 10.503（1）A，B= 9.003（3）A，c= 18.924（3）A，B = 101.98（1）A。16的晶体也是单斜晶系，空间群I2 ~ a，晶胞参数a= 20.476（2）A，B= 9.092（3）A，c= 21.211（2）A，A = 108.92（1）。通过直接方法求解结构，并通过全矩阵最小二乘计算进行优化：对于7，759个观察到的反射，R= 0.053;对于10，1189个反射，R= 0.032;对于16，2635个反射，R= 0.053。分析表明，在所有三种结构中，酚基都朝向大环空腔的中心;分子内O-H-O氢键在7（0（1）-H-0（5）2.856 A）和10（0（1）-H-0（2）2.707 A）中很明显。在16中，+NH 4阳离子通过三个N-H-O氢键靠近环腔，一个与酚氧（N-O 2.690 Ω），两个与环氧（N-O 2.884和2.883 Ω）。第四个N-H-O氢键与相邻分子的酚氧（N-O 2.781 π）形成中心对称的氢键二聚体。7、10和16的尺寸与预期值雅阁。10中的对硝基基团对大环的构象产生了相当大的结构影响。讨论了这些酚类化合物与包括氨在内的碱的反应，并报道了一些结晶酚盐的分离.许多冠醚类的多氧大环化合物具有空穴，能够为客体物种的接纳提供有利的环境，特别是碱金属和碱土金属阳离子以及铵盐和烷基铵盐。离子-偶极相互作用导致结合，其强度和特异性由阳离子和空腔大小、阳离子-偶极相互作用、受体拓扑结构、醚氧原子的数量和布置、受体的层性质以及整个系统的环境性质决定。离子结合特性也可以通过用另一个杂原子或能够给电子的基团取代冠醚的一个或多个醚氧原子，或通过将官能团形式的额外结合位点连接到大环的外围来影响，这一认识已经成为合成重链冠醚的最新发展的一个重要特征。
Macrocyclic polyethers having the 1, 3-xylyl subunit and an intraannular phenolic group have been synthesised to determine the influence of the proximate oxygen atoms of the crown ether on the chemical behavior of an intraannular substituent and, conversely, the influence of the substituent on the binding properties of the macrocycle. Williamson synthesis between 2, 6-bis (bromomethyl) anisole and the sodium salts oftri-, tetra-, and pentaethylene glycol produced the corresponding 15-, 18-, and21-membered crown ether anisóles which were demethylated with lithium iodide in pyridine affording the 15-, 18-, and 21-membered crown ether phenols 6, 7, and 8, respectively. The pAfa’s (H2Q) of these phenols were found to be (6) 10.7,(7) 10.6, and (8) 10.5. The crystal structures of 18-crown phenol (7), its p-nitro derivative (Id), and the ammonium salt of 10 have been determined. The crystals of 7 are orthorhombic, space group Pelf with four molecules in the unit cell of dimensions a= 9.779 (2) A, b= 18.943 (3) Á, and c= 8.915 (2) Á. Crystals of 10 are monoclinic, space group P2\¡ c with fourmolecules in the unit cell of dimensions a= 10.503 (1) A, b= 9.003 (3) Á, c= 18.924 (3) Á, and ß= 101.98 (1). Crystals of 16 are also monoclinic, space group I2¡ a with eightmolecules in the unit cell of dimensions a= 20.476 (2) A, b= 9.092 (3) A, c= 21.211 (2) Á, andß= 108.92 (1). The structures were solved by the direct methods and refined by full-matrix least-squares calculations: for 7 R= 0.053 for 759 observed reflections, for 10 R= 0.032 for 1189 reflections, and for 16 R= 0.053 for 2635 reflections. The analyses establish that in all three structuresthe phenolic group is oriented toward the center of the macrocyclic cavity; intramolecular O—H—O hydrogen bonding is apparent in 7 (0 (1)—H-0 (5) 2.856 Á) and 10 (0 (1)—H-0 (2) 2.707 A). In 16 the+ NH4 cation is held closeto the ring cavity by three N—H—O hydrogenbonds, one to the phenolate oxygen (N—O 2.690 Á) and two to ring oxygens (N—O 2.884 and 2.883 Á). A fourth N—H—O hydrogen bond to the phenolate oxygen of a neighboring molecule (N—O 2.781 Á) yields centrosymmetric hydrogen-bonded dimers. Dimensions for 7, 10, and 16 are in accord with expected values. The p-nitro group in 10 exerts a considerable structuring effect on the conformation of the macrocycle. Reactions of these phenols with bases including ammonia are discussed, and the isolation of some crystalline phenoxides is reported.Many polyoxygenatedmacrocycles of the crown ether variety possess cavities capable of providing a favorable environment for the reception of guest species, notably alkali and alkaline earth metal cations and ammonium and alkylammonium salts. 1™ 9 Ion-dipole interactions lead to binding, the strength and specificity of which are determined by cation and cavity size, cation-coun-terion interactions, receptor topology, the number and disposition of the ethereal oxygen atoms, the layer properties of the receptor, and the environmental properties of the system as a whole. 1CW7 The realization that ion-binding characteristics can also be influenced by replacing one or more ethereal oxygenatom of the crown ether by another heteroatom or group capable of electron donation, or by attaching additional binding sites in the form of functional groups to the periphery of the macrocycle, has been an important feature of recent developments with synthetic re-