环钯化二茂铁亚胺-三苯基膦配合物的合成、表征及催化Suzuki反应研究

为筛选高效催化Suzuki反应的催化剂, 合成了3种新的环钯化二茂铁亚胺-三苯基膦配合物2~4, 经元素分析(或HRMS)、 红外光谱和核磁共振谱对其结构进行了表征, 并通过X射线单晶衍射测定了化合物3的晶体结构. 这些化合物容易合成, 在空气和溶液中稳定, 可用作芳基溴及杂芳基溴与苯基硼酸偶联的Suzuki反应催化剂. 使用摩尔分数为0.01%的催化剂3, 以2倍量的K3PO4为碱, 于110 ℃下, 在甲苯中反应5~15 h, 使具有不同电子和位阻效应的取代芳基溴及杂芳基溴能以较高的产率与苯基硼酸反应生成偶联产物; 与溴苯相比, 带吸电子基的溴苯反应活性较高, 催化剂的摩尔分数降低至0.001%时, 仍能得到较高产率, 而带强给电子基的溴苯如4-溴苯甲醚及带邻位取代基的溴苯在其它条件相同时, 需要延长反应时间才能得到较高的产率.

Synthesis, Characterization and Catalytic Activity in Suzuki Reaction of Cyclopalladated Ferrocenylimine Triphenylphosphine Complexes

Biaryls are important fine chemicals and constitute ubiquitous fragments of numerous biologically active natural products, pharmaceuticals as well as functionalized materials. As one of the most powerful methods for the formation of biaryls, palladium catalyzed Suzuki coupling reaction of aryl halides with aryl boronic acids has attracted much research interest. In this article, three novel cyclopalladated ferrocenylimine triphenylphosphine complexes 2-4 were easily synthesized and characterized by elemental analysis(or HRMS), IR, 1H NMR, 31P NMR and X-ray single crystal diffraction. Compounds 2-4 were stable to air and moisture both in the solid state and in solution. These complexes were successfully used as catalysts in the Suzuki coupling of aryl bromides and heteroaryl bromides with phenylboronic acid. Using molar fraction 0.01% of catalyst 3 in the presence of 2 equiv. of K3PO4 as base in toluene at 110 ℃ for 5-15 h, a variety of aryl bromides with different electronic and steric effect and some heteroaryl bromides could be coupled with phenylboronic acid to afford the coupled products with moderate or excellent yields. Compared with phenyl bromide, the catalyst loading could be lowered to 0.001% providing the coupled products in good yields in the case of aryl bromides bearing electron-withdrawing groups. The reaction needed more time to get higher yields in the case of aryl bromides bearing electron-donating group or sterically hindered bromides.