多元醇修饰Pd-氮杂环卡宾复合物的制备及其对Suzuki-Miyaura反应的催化行为

提高催化剂在反应体系中的分散性,是有效提高催化剂活性的重要手段。本文利用Ullmann反应在大位阻氮杂环卡宾配体(NHC配体)上修饰丙三醇基团,以此来提高催化剂的分散性,进而促进其催化效率的提升。并通过这种大位阻NHC配体与乙酰丙酮钯的络合反应,制备高活性的钯复合物催化剂,进一步以Suzuki-Miyaura偶联反应为模型反应,评价该催化剂的活性与稳定性。结果表明,该催化剂在多种溶剂中表现出较好的分散性,针对溴苯甲醚和苯硼酸的偶联反应,在不同催化条件下,均表现出良好的催化活性,其中转化数(TON)值最高可达到99000。而且该催化剂针对溴苯与苯硼酸的反应体系中,具有广泛的反应底物适用性。与传统的四-(三苯基膦)钯相比较,该催化剂在空气气氛中仍可保持高效的催化行为,表现出较好的稳定性。

Preparation of Polyol Modified Pd-N-Heterocyclic Carbene Complex and Its Catalytic Performance in Suzuki-Miyaura Reaction

The improvement of dispersibility of catalyst is one of the most effective methods to increase its catalytic activity. After the N-heterocyclic carbene(NHC) ligand containing bulky substituent was modified with glycerol through Ullmann reaction, the responding oxygen-containing groups could effectively improve the stability, dispersibility and catalytic efficiency of this catalyst. Then, this NHC ligand was employed to chelate with palladium acetylacetonate to synthesize the responding catalyst. At last, this compound was employed to catalyze the Suzuki-Miyaura coupling reaction. With p-bromoanisole and phenylboronic acid as the model reaction to evaluate the catalytic activity of this palladium complex, this catalyst exhibits high catalytic activity in different conditions. Furthermore, the highest turnover number(TON) value of the catalyst even reaches up to 99000 due to its good dispersibility in various solvents. Moreover, the catalyst shows excellent catalytic performance towards Suzuki-Miyaura reaction when a wide variety of substituents are employed. Compared with tetrakis(triphenylphosphine)-palladium, the catalyst also keeps good catalytic activity and stability in air atmosphere.