温和条件下金属双氮杂环卡宾配合物催化CO2直接转化为炔酸的高效均相羧化反应

近年来,催化CO2合成精细化学品的研究备受关注。本研究在温和条件下利用金属双氮杂环卡宾催化剂实现CO2与末端炔烃的直接羧化反应,并提出合理的催化机理。首先,合成制备了铜基、银基两种金属双氮杂环卡宾催化剂,实验证明银双氮杂环卡宾配合物具有较好催化活性。通过改变环境条件和底物种类,对反应条件及催化剂底物适应性进行了探究,利用核磁共振谱仪表征产物分子结构并计算直接羧化反应的催化产率。结果表明,适宜催化条件为:1.2eq Cs2CO3作为添加剂、1大气压、室温、无水溶剂和1(mmol)%催化剂用量。银基金属催化剂活性较铜基催化剂高并具有广泛的底物适应性,对苯乙炔的催化产率高达93%;对乙炔气体同样具有良好的催化活性。此类催化剂具有优良的催化活性,能催化合成丙炔酸等重要医药中间体,在工业应用上具有极大潜力和广阔前景。

Notable Homogeneous Catalysis of CO2 into Acetylenic Acid by Bis-NHC-Metal Complex in Mild Conditions

Recently, the research of carboxylation reaction from CO2 to fine chemicals under mild conditions has attracted significant attention. Our studies focus on achievement of direct interaction between CO2 and terminal alkynes in the presence of metal catalysts bearing two N-heterocyclic carbene ligands at atmospheric pressure and room temperature, coming up with a reasonable catalytic mechanism. Firstly, Cu and Ag based bis(N-heterocyclic carbene) complexes were synthesized and screened for activity towards carboxylation reaction of terminal alkynes with CO2. Through varying a number of substrates and adjusting conditions of pressure, temperature, environmental basic strength, catalyst loading, water content and etc, suitable reaction conditions and the substrate adaptability were studied. Meanwhile, by utilizing nuclear magnetic resonance the structure of products were characterized and yields of direct carboxylation reactions were calculated. Herein, suitable conditions for carboxylation were 1.2eq Cs2CO3, 1 atm, room temperature, no water and 1%mmol catalyst loading. Bis-NHC-Ag exhibited higher catalytic activity than the Cu based analogue on a wide range of substrates. In addition, Ag based catalyst catalyzed the carboxylation of phenylacetylene under mild conditions in high yield, which is up to 93% as well as acetylene. Thus this kind of catalysts can be used for producing pharmaceutical intermediates and has great potential and broad prospects for industrial application.