Contrastive photoreduction pathways of benzophenones governed by regiospecific deprotonation of imidazoline radical cations and additive effects
Contrastive photoreduction pathways of benzophenones governed by regiospecific deprotonation of imidazoline radical cations and additive effects
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DOI：
10.1021/jo0514220
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发表时间：
2005-11-11
影响因子：
3.6
通讯作者：
Ikeda, H
中科院分区：
文献类型：
--
作者：
Hasegawa, E;Seida, T;Ikeda, H
[图表]在二苯甲酮与 1,3-二甲基-2-苯基苯并咪唑啉 (DMPBI) 的光反应中，二苯甲醇是主要产物。添加H2O加速了反应，且产物分布没有变化，而AcOH、PhOH和金属盐如LiClO4和Mg(ClOL4)(2)是生产苯频那醇的有效添加剂。相比之下，在与 2-(邻羟基苯基)-1,3-二甲基苯并咪唑啉 (o-HPDMBI) 的反应中，无论溶剂和添加剂如何，苯频那醇都会专门形成。这些观察结果与以下假设一致：DMPBI 中心点+ 在 C-2 位上向二苯甲酮羰基自由基提供质子，而 o-HPDMBI 中心点+ 提供苯酚质子。
[GRAPHICS]In the photoreaction of benzophenones with 1,3-dimethyl-2-phenylbenzimidazoline (DMPBI), benzhydrols were major products. Addition of H2O accelerated the reaction with no change in the product distribution, while AcOH, PhOH, and metal salts such as LiClO4 and Mg(ClOL4)(2) were effective additives to produce benzpinacols. In contrast, benzpinacols were exclusively formed regardless of the solvent and the additive in the reactions with 2-(o-hydroxyphenyl)-1,3-dimethylbenzimidazoline (o-HPDMBI). These observations are consistent with the hypothesis that DMPBI center dot+ donates a proton at the C-2 position to the benzophenone ketyl radicals while o-HPDMBI center dot+ donates a phenol proton.