N-杂环卡宾金属络合物催化的烷烃脱氢反应研究

Dehydrogenation reaction, which is one of the basic organic reactions, is the inverse process of hydrogenation reaction. Dehydrogenation is an endothermic and entropy-increased process. It is generally accomplished in the heterogeneous conditions with extremely high reaction temperature and accompanied by the side reactions. Homogeneous reaction system typically has more moderate reaction conditions, higher catalytic activity and regioselectivity. In view that the N-heterocyclic carbene-metal complexes have been widely used as catalysts in homogeneous hydrogenation reactions, this project intends to apply them in the inverse process of hydrogenation, to realize the dehydro-alkenylation and dehydro-aromatization reactions of alkanes (including chain alkanes and cycloalkanes) under homogeneous conditions through the adjustment of the combination of metal salt, ligand and other reaction conditions. Under comparatively mild reaction conditions, we will try to develop a green and efficient reaction system, which avoid to use extra base, oxidizing agent (except O2) and other hydrogen-acceptor reagent. It will be a dehydrogenation reaction with H2 or H2O as the sole by-product. We will also explore the detailed reaction mechanism through both experiments and DFT calculations. The mechanism research will provide theoretical explanations to experimental observations and theoretical guidance for further research. This project will deepen the understanding for the dehydrogenation reactions, and provide a new pathway for fine utilization of alkane materials.

脱氢反应为氢化反应的逆过程，是一类基本的有机反应。脱氢反应是吸热、熵增加的反应，目前大多数该类反应需在苛刻高温的非均相条件下进行，同时伴有较多的副反应。一般来说，相对于非均相催化体系，均相催化体系反应条件更加温和，催化剂活性和反应的区域选择性更加容易调控。鉴于N-杂环卡宾-金属络合物已被广泛应用于均相催化的氢化反应，本项目拟通过调节催化剂、配体组合以及反应条件，实现其逆过程—均相条件下的烷烃(包括链状烷烃和环烷烃)的催化脱氢烯基化或芳构化反应。在相对温和的反应条件下，发展绿色，高效的反应体系，避免额外添加碱、氧化剂（O2除外）和其它氢气接收试剂，以H2或H2O作为唯一的副产物。通过实验和密度泛函理论计算，对N-杂环卡宾-金属络合物催化脱氢反应机理进行深入研究，为反应现象提供理论解释，为后续研究提供理论指导。本项目的开展，将加深对脱氢反应的理解，为烷烃类化工原料的精细化加工提供新路径。

脱氢反应和氢化反应是有机化学中最常用的转化之一。在本项目的支持下，我们着手开发一些绿色高效的脱氢反应体系，利用空气作为氧化剂，避免使用额外的氧化剂和氢受体试剂。以此为目标，我们成功开发了几种制备含氮杂环化合物的新方法。通过这些一锅法反应，我们可以快速构筑N，N'-二芳基吲唑-3-酮，吖啶酮或者吖啶骨架结构。总体上来说，上述一锅法反应方法可以将铜催化的Chan-Evans-Lam（CEL）C-N偶联反应与随后的铜催化的交叉脱氢偶联（CDC）反应结合在一起，无需分离中间体，实现相应杂环化合物的快速构筑。同时，我们还探索了使用H2以外的新型加氢试剂的氢化反应。本课题组成功地实现了一锅法钯催化的C-N偶联和利用B2（pin）2进行的硝基还原的结合，使氨基二芳胺骨架的快速构建成为可能。