The palladium-catalysed copper-free Sonogashira coupling of isoindoline nitroxides: a convenient route to robust profluorescent carbon-carbon frameworks
The palladium-catalysed copper-free Sonogashira coupling of isoindoline nitroxides: a convenient route to robust profluorescent carbon-carbon frameworks
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DOI：
10.1039/b806963h
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发表时间：
2008-09-07
影响因子：
3.2
通讯作者：
Bottle, Steven E.
中科院分区：
文献类型：
--
作者：
Keddie, Daniel J.;Fairfull-Smith, Kathryn E.;Bottle, Steven E.
通过钯催化的无铜Sonogashira偶联反应合成了一系列新型的乙炔取代的异吲哚氮氧化合物。这些结果表明，Sonogashira反应适合于生成广泛的扩展结构的芳基氮氧化物。含有氮氧化物的新型芳基碘化物5-iodo-1，1，3，3-tetramethylisoindolin-2-yloxyl，3是这种偶联反应的关键中间体，高产率地得到了乙炔取代的异吲哚氮氧化物。脱保护的乙炔基氮氧化合物12与碘化多芳烃的后续反应提供了具有扩展共轭的新型芳香氮氧化合物。这类氮氧化物被描述为前荧光化合物，因为它们的量子产率明显低于相应的抗磁性衍生物。与非自由基甲氧胺衍生物(23和24)相比，萘基和苯乙炔基异吲哚氮氧化合物(13和14)的量子产率分别接近200倍和65倍。乙炔和丁二炔连接的氮氧化物二聚体也可以用这种交叉偶联方法合成。
A series of novel acetylene-substituted isoindoline nitroxides were synthesised via palladium-catalysed copper-free Sonogashira coupling. These results demonstrate that the Sonogashira reaction is suitable for the generation of a wide range of aryl nitroxides of expanded structural variety. The novel aryl-iodide containing nitroxide, 5-iodo-1,1,3,3-tetramethylisoindolin-2-yloxyl, 3, was a key intermediate for this coupling, giving acetylene-substituted isoindoline nitroxides in high yield. Subsequent reaction of the deprotected ethynyl nitroxide 12 with iodinated polyaromatics furnished novel aromatic nitroxides with extended-conjugation. Such nitroxides have been described as profluorescent, as their quantum yields are significantly lower than those of the corresponding diamagnetic derivatives. The quantum yields of the naphthyl- and phenanthryl-acetylene isoindoline nitroxides (13 and 14) were found to be similar to 200-fold and similar to 65-Fold less than the non-radical methoxyamine derivatives (23 and 24). Ethyne- and butadiyne-linked nitroxide dimers could also be synthesised by this cross coupling methodology.