Synthesis Of Poly(Imidazole Ionic Liquid) Supported Pd Catalysts And Their Application In Solvent-free Heck Reaction

Heck reaction, which presents the coupling of halides and olefins catalyzed by Palladium, is the main method to synthesize cinnamate derivatives, stilbene deribatives and pharmaceutical intermediates. Traditional homogeneous Pd catalysts used for Heck reaction have some drawbacks like high cost, separation problem and environmental pollution. Thus supported Pd catalysts are considered as a solution to these problems. However, many supported Pd catalysts still had low activity. Supported ionic liquid Pd catalysts, which combine ionic liquids, heterogeneous support and Pd, have high activity and good recycling performance. Moreover, extensive organic solvent used in industry caused serious environmental pollution. Thus it’s desirable to develop more green reaction systems. Solvent-free reaction system is considered as an effective method to solve the problem of solvent pollution.Here we designed and prepared three kinds of poly(imidazole ionic liquid) supported Pd catalysts: Pd/Fe3O4@PIL-NH2, Pd/PSV and Pd/PSVV, and their structure and properties were characterized with FT-IR, TEM, XRD, XPS and so on. The catalysts could catalyze Heck reaction efficiently and be able to reuse under solvent-free condition. The specific contents are as follows:1. Magnetic support Fe3O4@PIL-NH2 was prepared by copolymerized ionic liquid 1-vinyl-3-(2-aminoethyl) imidazolium bromide([VAIM]Br) and magnetic nanoparticles Fe3O4-MPS, and then used to support Pd nanoparticles to obtain Pd/Fe3O4@PIL-NH2. The catalyst could efficiently catalyze solvent- free Heck reaction of halogenated benzenes and olefins with the highest TOF value up to 34,182 h-1. The catalyst could run five times with 94% isolated yield still achieved at the fifth run. In addition, the catalyst could be easily separated by an external magnet.2. The support PSV was prepared by copolymerizing 1-vinyl-3-butyl imidazolium bromide(VBIB) and styrene. Then Pd was immobilized on the support to give the catalyst Pd/PSV. The catalyst could efficiently catalyze Heck reaction with a maximum TOF value of 39,000 h-1 obtained. And Pd/PSV could be used for five times, with 86% yield still obtained at the fifth run.3. PSVV was synthesized by copolymerizing VBIB, N-vinylimidazole(VI) and styrene, which was loaded Pd to get the catalyst Pd/PSVV. The catalyst was very effectively for Heck coupling with an amazing TOF value achieved 57,000 h-1. The catalyst could be used for five consecutive times, and 90% isolated yield still received at the fifth run.