作者:Gerardus B.M. Kostermans、Willem H. De Wolf、Friedrich Bickelhaupt
DOI:10.1016/s0040-4020(01)86834-4
日期:1987.1
A relatively efficient route to substituted [5]paracyclophanes 11 is described. Diels Alder reaction of the pentamethylenecyclobutacfienes 3 and 4, prepared in situ, with acetylenes E-C≡C-E (5, E = electron withdrawing group) gives a mixture of Dewar benzenes, from which the 1,4-bridged isomer 7 is conveniently isolated after aromatization of the other isomers. Irradiation (254 nm) of 7 at 220 K establishes
描述了到取代的[5]对环环烷11的相对有效的途径。原位制备的五亚甲基环丁二烯3和4与乙炔EC≡CE(5,E =吸电子基团)的Diels Alder反应产生杜瓦苯的混合物,在芳香化后可方便地从中分离出1,4-桥连异构体7其他异构体。照射(254纳米)7在220ķ之间建立相片平衡7和11与后者的2-15%,这取决于E.的芳族特性11从UV-和衍生的1 H-NMR光谱; 在220 K下有两个构象异构体可以看出11 '和11。尽管大多数11均比母体化合物[5]对环环烷具有更高的热稳定性,但它们在室温下会在溶液中缓慢分解。