Carbon Dioxide Involved Catalytic Conversion Of Methylene Cyclic Carbonates

With the rapid development of modern industry,carbon dioxide?CO₂?,as the most notorious chemical waste,has a serious impact on the global environment due to uncontrolled excessive emissions.On the basis of environmental protection and resource utilization,the efficient activation of CO₂ and the selective conversion to high value-added fine chemicals or polymer materials have very important theoretical and practical significance.Among them,the research field of cyclic carbonate formation from CO₂ has attracted much attention.So far,metal catalysts,or high temperature and high pressure reaction conditions are needed to synthesize cyclic carbonates.Hence,the development of new organic catalytic systems is urgent.At present,the preparation of non-isocyanate polyurethane?NIPU?using cyclic carbonate as a monomer is also a major research hotspot.The research focus of this thesis is to design and develop a novel organocatalytic system to realize CO₂ involved methylene cyclic carbonate formation,thus further preparing high value-added cyclic carbonate compounds and non-isocyanate polyurethane?NIPU?.?1?Design a novel Lewis base-CO₂ adduct/organic amine dual organocatalyst system to realize the"one-pot"cascade reaction of CO₂,propargylic alchols and vicinal diols in a mild reaction condition,and efficiently synthesize functional cyclic carbonates.Among them,the carboxylation reaction of CO₂ and propargylic alchols takes place to generate?-alkylidene cyclic carbonates as a new carbonylation reagent,which further reacts with vicinal diols via transesterification to form functionalized cyclic carbonates with high activity and chemical selectivity.The optimal reaction conditions are:1)LB-CO₂ adduct?1 h,10 mol%?,CO₂?0.1MPa?,25oC,24 h;2)MTBD?10 mol%?,CH₃CN,25oC,24 h.NMR,IR,MS and X-ray single crystal diffraction proved the correctness of the structure.In addition,the ee value of the corresponding chiral product was determined by GC and HPLC,and the proposed reaction mechanism was explored by density functional theory calculation?DFT?.?2?Using the prepared biomass-based binary cyclic carbonate as a new type of monomer,the polyaddition of cyclic carbonate and diamines in the organic catalytic system was investigated to synthesize non-isocyanate polyurethane employing organocatalyst.By optimizing the type of diamines,organic catalyst,reaction solvent and reaction temperature,only polyurethane oligomers with a number average molecular weight of about 3000 g.mol^-1were obtained.The proposed mechanism of polyaddition indicates that unstable hemiketal intermediates were generated via aminolysis process,which should be the main cause for the oligomer formation.