Ester Hydrogenation Catalyzed by CNN-Pincer Complexes of Ruthenium
Ester Hydrogenation Catalyzed by CNN-Pincer Complexes of Ruthenium
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DOI：
10.1021/acs.organomet.6b00009
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发表时间：
2016-04-11
期刊：
影响因子：
2.8
通讯作者：
Chianese, Anthony R.
中科院分区：
文献类型：
--
作者：
Kim, Daniel;Le, Linh;Chianese, Anthony R.
合成了两种新型cnn钳形配体负载的钌配合物。在温和的条件下（105℃，6 bar H-2），这两种催化剂都作为酯的加氢催化剂进行了测试。对配体结构的显著依赖性被观察到，二甲氨基取代的配体提供了几乎无活性的催化剂，而二乙胺取代的变体提供了高达980催化周转率的苯甲酸苄酯的加氢。该体系催化各种底物的氢化反应，包括乙基、苄基和己基酯，但令人惊讶的是对甲酯不反应。实验表明，在反应条件下，碱催化酯交换反应迅速，在反应混合物中加入苯甲醇时，甲酯能有效氢化。对伯醇脱氢制酯的逆反应也进行了试验；1-己醇脱氢制己酸己酯的催化转化率高达920次。
Ruthenium complexes supported by two new CNN-pincer ligands were synthesized. Both were tested as catalysts for the hydrogenation of esters under mild conditions (105 degrees C, 6 bar H-2). A striking dependence on ligand structure was observed, as a dimethylamino-substituted ligand gave a nearly inactive catalyst, while a diethylamino-substituted variant gave up to 980 catalytic turnovers for the hydrogenation of benzyl benzoate. This system catalyzes the hydrogenation of various substrates including ethyl, benzyl, and hexyl esters, but is surprisingly unreactive toward methyl esters. Experiments demonstrate that base-catalyzed transesterification is rapid under the reaction conditions and that methyl esters are effectively hydrogenated when benzyl alcohol is added to the reaction mixture. The reverse reaction, dehydrogenation of primary alcohols to give esters, was tested as well; up to 920 catalytic turnovers were observed for the dehydrogenation of 1-hexanol to hexyl hexanoate.