Co@CoO催化剂表面类氢负物种NH_(2)^(δ-)驱动下的还原胺化反应  

Co@CoO‐catalyzed reductive amination driven by hydride‐like NH_(2)^(δ-)species

作　　者：郭万君 王志强 相爽 景亚轩 刘晓晖[1] 郭勇[1] 龚学庆[1] 王艳芹[1] Wanjun Guo;Zhi‐Qiang Wang;Shuang Xiang;Yaxuan Jing;Xiaohui Liu;Yong Guo;Xue‐Qing Gong;Yanqin Wang(Key Laboratory for Advanced Materials and Joint International Research Laboratory of Precision Chemistry and Molecular Engineering,Feringa Nobel Prize Scientist Joint Research Center,Research Institute of Industrial Catalysis,School of Chemistry and Molecular Engineering,East China University of Science and Technology,Shanghai 200237,China)

机构地区：[1]华东理工大学化学与分子工程学院,工业催化研究所,上海200237

出　　处：《Chinese Journal of Catalysis》2023年第4期181-190,共10页催化学报（英文）

基　　金：国家自然科学基金(21832002,21872050,21808063,21825301,22102056);中国博士后科学基金会(2021M691011,2021TQ0106).

摘　　要：胺类化合物作为一类重要的精细化学品,广泛应用于合成染料、表面活性剂、聚合物、药品和农用化学品.催化还原胺化是合成胺类化合物的重要手段.在还原胺化反应中,水是唯一的副产物,且反应条件温和,符合绿色化学原则,因此受到了广泛关注.在过去的几十年里,生物质衍生的羰基化合物(糠醛、环戊酮、5-羟甲基糠醛等)的催化还原胺化得到了特别关注,为利用可再生资源可持续地生产胺类提供了可能性.通常,金属(Ru,Ir,Pt,Rh,Co,Ni等)被认为是还原胺化的活性中心,相关研究快速发展,但大部分研究都围绕着金属负载型催化剂展开,对于以金属氧化物为活性中心鲜有研究.另外,还原胺化过程研究表明,席夫碱在反应开始阶段迅速生成,然后通过氨解产生相应的伯胺;但席夫碱氨解为伯胺的过程速率较慢,是该反应的决速步骤,因此设计高效催化剂加快席夫碱的氨解是还原胺化过程中的重要科学问题.受孤立的路易斯酸碱对可以催化氢气异裂过程的启发,本文利用具有核壳结构的Co@Co O为催化剂,发现表面具有氧空位的CoO具有独特的解离NH_(3)生成类氢负物种(NH_(2)^(δ-))的能力,该NH_(2)^(δ-)物种能够加速席夫碱的氨解,从而使得该催化剂展现出较好的还原胺化性能,且具有较好的稳定性,在环戊酮胺化为环戊胺过程中使用10次没有失活.通过密度泛函理论(DFT)计算和D_(2)同位素示踪实验发现了类氢负物种NH_(2)^(δ-),且验证了H^(δ-)和NH_(2)^(δ-)物种在Co O表面可稳定地共吸附,席夫碱在催化剂表面吸附较弱,使得希夫碱中间体可以在解离NH_(2)^(δ-)和H^(δ-)后的CoO表面自由移动,从而与表面解离的H^(-)和NH_(2)^(δ)–发生分子碰撞,生成伯胺,最后脱附完成催化循环.本文实现了金属氧化物催化还原胺化反应.更重要的是,在加氢/氢解反应中,孤立的路易斯酸碱对上异裂产生的H^(δ-)物种虽然�Owing to the wide application of primary amines,their selective production via reductive amination has become a crucial research topic.Various metal‐supported catalysts(Pt,Ru,Rh,Ir,Co,Ni,etc.)have been investigated,and metallic species have been recognized as active sites in recent years.Herein,we reveal for the first time that CoO species containing oxygen vacancies within a core‐shell‐structured Co@CoO catalyst accelerate the ammonolysis of Schiff bases,key intermediates in reductive amination,through NH_(3)dissociation to hydride‐like NH_(2)^(δ-)species,delivering an excellent reductive amination performance.The catalyst is highly stable and was utilized in 10 catalytic cycles for the amination of biomass‐derived cyclopentanone(CPO)to cyclopentylamine(CPA)without deactivation.Various computational models in combination with spectroscopic measurements indicated that this catalyst not only drives the dissociation of H_(2)to the active H^(δ-)species,but also enables the homolytic cleavage of NH_(3)to NH_(2)^(δ-).D_(2)isotopic tracing experiments provided further evidence of the direct involvement of hydride‐like NH_(2)^(δ-)species in Schiff base ammonolysis.Theoretical calculations verified the stable co‐adsorption of H^(δ-)and NH_(2)^(δ-),which allows the Schiff base to move freely on the surface of the CoO shell and participate extensively in molecular collisions,resulting in exceptional catalytic activity.This is the first study that demonstrates the potential of metal oxide catalysts for the production of primary amines via reductive amination.

关 键 词：还原胺化 类氢负物种NH_(2)^(δ-) Co@CoO 席夫碱 

分 类 号：O622.6[理学—有机化学] O643.36[理学—化学]