)-bridged calix[6]arenes with four uncapped hydroxy groups at the lower rim and various kinds of functionalities on the bridging unit were synthesized. Their structures in solution and in the crystalline state were determined by NMR spectroscopy, molecular mechanics calculations, and X-ray crystallographic analyses. They were found to adopt a pinched cone conformation, where the bridging 1,3-phenylenebis(methylene)
合成了 1,3-亚苯基双(亚甲基)-桥连杯[6]芳烃,其下缘有四个未封端的羟基,桥接单元上有各种官能团。它们在溶液中和结晶状态下的结构通过核磁共振光谱、分子力学计算和 X 射线晶体学分析确定。发现它们采用收缩锥体构象,其中桥接的 1,3-亚苯基双(亚甲基)单元位于下方,从而形成锥体的底部。这些分子中有很强的分子内氢键网络,形成环状阵列;该网络被认为在稳定收缩锥体构象方面发挥着重要作用。还研究了桥接单元的构象迁移率。
Syntheses and structures of novel m-xylylene-bridged calix[6]arenes: stabilization of a sulfenic acid in the cavity of calix[6]arene
found to be directed into the cavity and surrounded by the calix[6]arene macrocycle with the 1,2,3-alternate conformation, being protected from self-condensation leading to the corresponding thiosulfinate. The high stability of 1h demonstrates that the framework of the bridgedcalix[6]arene can effectively regulate the reactivity of the functional group fixed in the cavity.
Conformational Mobility of the Bridged Calix[6]arenes with Allyl and Ethyl Groups at the Lower Rim
作者:Shigehisa Akine、Kei Goto、Takayuki Kawashima
DOI:10.1246/bcsj.74.2167
日期:2001.11
The conformational mobility of the bridgedcalix[6]arenes with allyl and ethyl groups at the lower rim was investigated. Allylation of the tetrahydroxy compounds afforded two isomers: 5a (cone) and 5b (1,2,3-alternate), which were separated by silica-gel chromatography. These isomers underwent slow isomerization at room temperature with a half-life time of about 2 weeks. On the other hand, the ethyl
Isolation of Two Conformationally Frozen Isomers of a Bridged Calix[6]arene
作者:Toshiyuki Saiki、Kei Goto, and Renji Okazaki
DOI:10.1246/cl.1996.993
日期:1996.11
Two conformationally frozen isomers of a 1,4-bridged calix[6]arene, one of which is a cone conformer while the other adopts a 1,2,3-alternate conformation, have been isolated by silica-gel chromatogarphy. The interconversion between them was not observed even after heating either of them at 120 °C.
1,4-桥接杯[6]芳烃的两种构象冻结异构体,一种是锥形构象异构体,另一种采用1,2,3-交替构象,已通过硅胶色谱分离。即使在 120 °C 下加热它们中的任何一个后也未观察到它们之间的相互转化。