温和条件下的环己酮脱氢及其转化反应研究

Functionalization of alkanes especially for those without any functional groups is a very hot and challenging topic in organic chemistry. It is also a very important and fundamental reaction in petrochemical industry. Thus the direct functionalization of simple alkanes attracts much attention and made great progress during the past several decades. However, due to the high energy of C-H bond, the direct funtionalization of simple alkanes always occur problems such as high reaction temperature,low selectivity and need use large amount of noble metals. Selective functionalization of alkanes under mild reaction conditions is highly desirable. In this project we will focus our research on dehydrogenation of alkanes under mild conditions and its further transformations. Using cyclohexanones and their derivatives as the model substrates, we will systematically investigate the reaction conditions. In this process, nitro, cyano or imine groups will act as the hydrogen acceptors and cyclohexanones act as the hydrogen and aryl sources via dehydrogenation and aromatization. The dehydrogenation, reduction, C-X bond formation will complete in one-pot without any additional reducing reagent and oxidant. With this in hand, we will focus our research on dehydrogenation of simple alkanes with further optimization of the reaction conditions. Our final goal is to develop an environmentally benign approach for efficient functionalization of simple and inert alkanes.

烷烃尤其是不含任何官能基团的简单烷烃的功能化反应是有机合成化学研究的前沿和热点领域，同时也是石油化工的基础。由于烷烃碳-氢键具有键能高、难以选择性活化的特点，实现在温和条件下烷烃的高效、高选择性切断和重组是发现、发明和发展饱和烷烃转化新反应的关键科学问题。针对当前烷烃脱氢反应中存在的反应温度高、选择性难以控制、需要使用氢接受剂等不足，本项目拟开展环己酮和简单烷烃的均相催化脱氢及其转化反应研究。通过系统筛选高效、高选择性和廉价的过渡金属催化剂，实现环己酮类化合物在温和条件下的脱氢反应。采用硝基、氰基和亚胺等作为氢接受剂，实现在无外加氧化剂和还原剂存在条件下的环己酮脱氢、硝基（氰基或亚胺）还原、碳-杂键生成反应在"一锅"中完成，环己酮类化合物作为氢源和芳基来源。在此基础上，进一步优化反应条件发展简单烷烃在温和条件下的催化脱氢反应及其进一步转化反应体系，开辟环境友好的烷烃功能化反应新途径。

本课题主要以环己酮及其衍生物作为研究对象，通过脱氢芳构化作为芳基来源用于进一步转化反应。通过系统的研究发现，环己酮可以在过渡金属存条件下和没有过渡金属参与条件下进行脱氢芳构化及其进一步转化反应。实现了环己酮作为芳基来源的直接芳基化反应，实现了过渡金属催化条件下的杂环生成反应，实现了无过渡金属参与条件下环己酮作为芳基来源的杂环生成反应，实现了环己酮参与的选择性杂环生成反应（非脱氢芳构化）。在多组分杂环选择性生成反应中，环己酮作为反应底物表现出十分优越的反应性能：这类反应大多不需要使用过渡金属催化剂，不但可以降低反应成本，还可以从源头上避免重金属污染，对于制备电子功能材料和药物分子尤其重要；环己酮可以作为二碳来源用于[2+2+2]或者[4+2]成环反应，由于其羰基和邻位碳的反应活性有明显的差别，因而反应的选择性控制变得十分简单。采用环己酮作为反应底物，将为碳-碳键、碳-杂键和杂环选择性生成反应提供环境友好的新途径。