Cooperative Reactivity in an Extended-Viologen-Based Cyclophane
详细信息 查看全文
- 作者：Edward J. Dale ; Daniel P. Ferris ; Nicolaas A. Vermeulen ; James J. Henkelis ; Ilja Popovs ; Michal Juríček ; Jonathan C. Barnes ; Severin T. Schneebeli ; J. Fraser Stoddart
- 刊名：Journal of the American Chemical Society
- 出版年：2016
- 出版时间：March 23, 2016
- 年：2016
- 卷：138
- 期：11
- 页码：3667-3670
- 全文大小：384K
- ISSN：1520-5126
文摘
A tetracationic pyridinium-based cyclophane with a box-like geometry, incorporating two juxtaposed alkyne functions, has been synthesized. The triple bonds are reactive through cycloadditions toward dienes and azides, promoted by the electron-withdrawing nature of the pyridinium rings, as well as by the strain inherent in the cyclophane. The cycloadditions proceeded in high yields, with the cyclophane reacting faster than its acyclic analogue. While the cyclophane contains two reactive triple bonds, there is no evidence for a stable monofunctional intermediate—only starting material and the difunctional product have been detected by 1H NMR spectroscopy. Molecular modeling of the energy landscape reveals a lower barrier for the kinetically favored second cycloaddition compared with the first one. This situation results in tandem cascading reactions within rigid cyclophanes, where reactions at a first triple bond induce increased reactivity at a distal second alkyne.