The Synthesis Of Water-soluble Palladium Catalyst With A Pyridinium Salt Tag And Its Application In Coupling Reaction

Palladium-catalyzed Heck coupling reaction, which plays an important role in organic synthesis, can be performed stereoselectively under mild reaction conditions, with widely applicable substrates and easily processed products. As a green, environmentally friendly solvent, ionic liquid can increase the efficiency of transition metal catalyst and promote the reaction, thus having become an ideal alternative for traditional organic solvents. In recent years, ionic liquids have been applied in Heck reactions. Ionic liquids, as ligands or catalysts, not only enhance the catalytic activity or stability of metal, but also allow recycling, which will have significant application value.The main contents of this thesis are as follows:1. First, the application of ionic liquid-supported catalysts, the effect of reaction conditions on Heck coupling reaction, and the application of ionic liquids in Heck reactions were briefly reviewed.2. A new pyridine salt-modified palladium catalyst (Pd-[Salen-Py][X]2) was synthesized by a multi-step reaction starting from ethylenediamine and acetylacetone, and this catalyst was fully characterized. Modified by pyridine salt, the catalyst was highly soluble in water and other polar solvents (e.g. DMF and NMP).3. The catalytic properties of Pd-[Salen-Py][X]2 were investigated. Using the coupling reaction of iodobenzene and styrene as a probe, the factors influencing the Heck coupling, such as temperature, catalyst concentration, bases, solvents, and anions, were examined. Using the optimized conditions, after 4 h of reaction at 100℃, the conversion rate of iodobenzene reached 99.1%, and TOF number was 49.6 while the selectivity of the product was 99.9%. Besides, the catalyst was also applied in the coupling reaction of other substrates. The results suggested that the system was universal for different unsaturated olefin substrates.4. Compared with non-supported metal Schiff base catalyst (Pd-Salen), the palladium catalyst which was modified by ionic compound Pd-[Salen-Py][Br]2 was more reactive. Besides, Pd-[Salen-Py][Br]2 had higher catalytic activity and selectivity for coupling reaction comparing with other palladium catalysts. The catalyst was also thermally stable. More importantly, the catalyst, because of excellent thermal stability and water solubility, could be recovered easily and remained its reactivity after being recycled five times. The catalytic activity of palladium catalyst Pd-[Salen-Py][X]2 supported by ionic compounds was effected by different anions obviously. In addition, different polar solvents determined the form of ions in the ionic compound, thus influencing the catalytic activity of the catalyst.Overall, a novel catalyst supported by ionic compounds was designed and prepared to conduct the coupling reactions of iodobenzene and styrene. The catalytic activity of this ionic compounds-supported catalyst can be ascribed to the designability and microscopic structural characteristics. The results herein provide valuable references for the design and synthesis of new ionic compounds-supported catalysts with high efficiency in the future.