摘要/Abstract

原子经济性良好的炔烃[2+2+2]环加成反应与绿色溶剂超临界二氧化碳相结合, 是一个符合绿色化学原则的环境友好反应过程. 建立了一个纯超临界二氧化碳介质中八羰基二钴催化的端基炔烃环三聚反应体系, 在优化的反应条件下, 以较高产率选择性地制备1,2,4-三取代苯衍生物. 优化了催化剂用量、二氧化碳压力、反应温度及时间等反应条件, 讨论了反应物料及催化剂在超临界二氧化碳介质中的溶解性和相行为, 提出了端基炔烃环三聚反应机理, 并将反应底物从C≡C键拓展至C≡N键, 对超临界二氧化碳介质中炔-腈环加成反应进行了初步探索. 优化出的炔烃环三聚催化反应体系无需使用有机助溶剂和各类助剂, 底物适应性好, 产物选择性高, 为合成1,2,4-三取代苯衍生物提供了一种绿色合成方法.
关键词: 超临界二氧化碳, 端基炔烃, 环三聚反应, 羰基钴催化剂, 炔-腈环加成反应
Atom-efficient [2+2+2] cycloaddition reaction of alkynes in green solvent supercritical carbon dioxide (ScCO₂) is an environmentally friendly reaction process that conforms to the principles of green chemistry. Cyclotrimerization of terminal alkynes catalyzed by Co₂(CO)₈ in pure ScCO₂ has been studied to obtain 1,2,4-trisubstituted benzene derivatives with excellent selectivity. The reaction conditions for the cyclotrimerization were optimized, such as concentration of catalyst, CO₂ pressure, reaction temperature and time. The solubility and phase behavior of the reaction materials and catalysts in ScCO₂ medium were discussed, and the mechanism of Co₂(CO)₈ catalyzed cyclotrimerization of terminal alkynes was assumed. The reaction substrate was extended from C≡C (alkyne) to C≡N (nitrile), and the alkyne-nitrile cycloaddition reaction in ScCO₂ was preliminary explored. Our optimized catalytic system for the cyclotrimerization of terminal alkynes exhibited wide substrate scope and high product selectivity, in which no organic co-solvent or additives were added. It provided a green synthetic method for 1,2,4-trisubstituted benzenes.
Key words: supercritical carbon dioxide, terminal alkyne, cyclotrimerization reaction, carbonyl cobalt catalyst, alkyne-nitrile cycloaddition reaction


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