scCO2介质中Pd/O2促进的缺电子氟代苯环C-H键活化与有机硅试剂的偶联反应研究

Transition-metal catalyzed C-H bond activation and its related functionalization can simplify the organic synthesis processes to achieve atom-economic synthesis. As a result, transition-metal catalyzed C-H bond activation coupling reaction is a hot research project in chemistry. Dioxygen (O2) as an oxidant, which is especially favored in transition-metal catalyzed C-H activation coupling reaction. However, O2 has small solubility in organic solvent, which restrains the further development of transition-metal catalyzed C-H activation coupling reaction. Therefore, taking advantage of miscible characteristic of O2 in scCO2, there is important scientific significance to carry on a transition-metal catalyzed coupling reaction research with O2 as oxidant in scCO2. Unfortunately, there is no report on transition-metal catalyzed C-H bond activation coupling with O2 as oxidant in scCO2. Basing on understanding of related reports and first-phase research by applicant, this application project is a research for Pd-catalyzed Hiyama coupling of C-H activation of electron-deficient polyfluoroarenes with silyl reagents using O2 as terminal oxidant in scCO2. The research of desired reaction is the discovery of new field in chemistry; on the other hand, includes the research of equilibration of reaction rates, fast regeneration and circle of Pd(II) from Pd(0) under aerobic conditions, solubility of transition metal catalyst Pd in scCO2, real catalytic species of Pd-catalyzed C-H activation of electron-deficient polyfluoroarenes in scCO2, and further development of other new coupling reactions with green and cheap features.

过渡金属催化C-H 活化及相关的C-H 官能团化可简化合成步骤，提供原子经济合成路线。因此，过渡金属催化C-H 活化的偶联反应是当前的研究热点。在此类反应中，氧气(O2)作为氧化剂备受关注，但O2在有机溶剂中的溶解度制约了此类反应的进一步发展。鉴此，利用O2在超临界二氧化碳(scCO2)中的互溶特点，研究scCO2/O2体系中的偶联反应，具有重要意义。 然而，scCO2中O2参与的过渡金属催化C-H活化的偶联反应研究，在目前仍属空白。基于对相关报道的分析和我们的先期探索研究，本申请项目立足于以scCO2为反应介质，O2为单一氧化剂，过渡金属Pd催化缺电子氟代苯环C-H键活化与有机硅试剂的偶联反应研究。 对目标反应，一方面是探索新的化学领域，另一方面是研究反应速率的匹配、氧气下的催化剂再生与循环、过渡金属催化剂在scCO2介质中溶解度、反应中的真正催化物种，进一步开拓其它绿色廉价的新反应。

对目标反应，我们尝试了不同的碱、添加剂、温度等对反应的影响，初步获得了均衡反应速率所需的碱、温度等反应参数；在氧气作为反应氧化剂情况下，初步研究发现升高ScCO2压力对反应有着积极作用。尝试了以醋酸碘苯和芳基羧酸分别作为添加剂，以期在scCO2反应介质中增强模型反应效率，通过对反应中副产物分析，发展了五氟苯底物C-H键活化与醋酸碘苯的偶联反应，以及2-硝基苯甲酸在Cu作用下的脱羧官能团化反应，实现了脱羧的甲硫醚化、质子化、二聚、卤化和氰化反应。. 项目研究过程中，在J. Org. Chem.、Eur. J. Org. Chem.、RSC Adv.等国际主流化学杂志发表论文9篇，其中IF>2的7篇，IF>3的4篇；申请专利1项；协助课题组长培养了具有良好科研素质的研究生10名。