Palladium-Catalyzed Carbonylation For The Synthesis Of Green Chemicals:Malonates And Glycerol Carbonate

Fossil resources, especially the petroleum gradually tends to dry up. The development of environmentally benign and efficient synthetic methods continues to be a central goal of current research in chemistry. In this regard, catalysis is a key technique for achieving these objectives and for contributing to a "greener" chemistry in the future. Carbonylation reactions generally have a high atom efficiency and attract significant coverage from many researchers. On the other hand, biomass possesses many advantages such as renewable, large reserves, wide variety of sources, and easy to obtain, has caused great concern. Combining carbonylation reaction and biomass utilization would effectively achieve deep processing and valorization of biomass as well as make the fine chemicals synthesis process much greener, so it is the significant hot spot of current chemical research and development.In this dissertation, we will study palladium-catalyzed carbonylation reactions in-depth from the two aspects of enhancing the existing homogeneous catalytic synthesis system and opening up a new catalytic reaction system. First, an efficient process for the synthesis of diethyl malonate (DEM) and other malonates via palladium-catalyzed carbonylation of chloroacetates was investigated. Excellent selectivity (96%) and yield (94%) are obtained without Pd black formation. We adopt a weakly alkaline buffer to control the selectivity of DEM in the reaction for the first time, and discuss in detail the relationship between selectivity and buffer medium in the reaction. The combination of an anisole solvent and a Na2HPO4/NaH2PO4 buffer is beneficial for thoroughly restraining the phase transfer catalyzed substitution of DEM with ethyl chloroacetate, as well as accommodating the proposed [(PPh3)2PdI]-[Bu4N]+intermediate by providing a suitable environment for its stable existence. We achieve the highest efficiency for the catalytic cycle by fine-tuning the balance between oxidative addition and reductive elimination rates, and develop a recoverable heterogeneous polymer-bound Pd catalyst with 85% yield that can be reused without appreciable loss of activity over four cycles.We present a direct and highly efficient approach for synthesizing glycerol carbonate, via the catalytic oxidative carbonylation of glycerol, using PdCl2(phen) (phen 1,10-phenanthroline) as catalyst with the aid of KI. The palladium catalyst loading as low as 0.25 mol% is sufficient for high conversion (92%) and selectivity (99%) at the reaction condition:2.0 MPa CO,1.0 MPa O2,140℃,2h. The turnover frequency (TOF) reaches 184 h-1. Furthermore, using crude glycerol, we achieved 85% conversion of glycerol. We discuss in detail a plausible mechanism based on PdI2(phen) as an intermediate. We propose that there is synergistic effect of I- and 1,10-phenanthroline on the performance of the Pd complex catalyst. Based on the cyclic voltammograms, the reduction of PdI2(phen) occurred at a more positive potential than that of PdCI2(phen). This may explain why the catalytic activity of PdI2(phen) was more effective than that of PdCI2(phen). Furthermore, we develop a more efficient palladium-catalyzed system PdCI2(phen)/CuI, high conversion (91%) and selectivity (98%) are achieved and the TOF reaches 455 h-1 at the milder reaction condition:1.6 MPa CO,0.8 MPa O2,120℃,2h.Finally, a novel zeolite-Y confined Pd catalyst, PdCl2(phen)@Y, is successfully prepared by a"flexible ligand"method. The structure and composition of the heterogeneous catalyst have been characterized by AAS, elemental analysis, N2 sorption, XRD, FTIR, solid state NMR and XPS, respectively. This catalyst exhibits a comparable activity to the homogeneous counterpart and could be reused 5 times without significant decrease in activity. PdCI2(phen)@Y is much more active than the reported polystyrene grafted palladium 1,10-phenantroline complex catalyst PdCl2(phen-PS) and two usual ligand-free palladium(O) catalysts Pd/C and Pd/a-Al2O3. Furthermore, the reaction mechanism of this highly efficient and stable heterogeneous catalyst system is also discussed in detail, which maybe due to the unique nanocage-confined structure.