Activation Of Carbon Dioxide And Synthesis Of Cyclic Carbonates

The chemistry of carbon dioxide has received much attention in decades from both economical and environmental points of view:utilization of the least-expensive carbon source and reduction of global-warming gas. One of the most successful examples is the synthesis of carbonates from CO2 and epoxides, including cyclic carbonates and polycarbonates. The cyclic carbonates have been widely used as synthetic intermediates, aprotic polar solvents, precursors for biomedical applications and raw materials for engineering plastics.Now, the frontier of chemical science and popular area is green chemistry, and the biomimetic catalysis is the most important branch of green chemistry. Main biomass and enzyme molecule under the action of the enzyme catalysis constitutive structural-activity relationships can also simulated by green biomimetic catalysis. The hot spot of carbon dioxide inserting to epoxides to synthesis of cyclic carbonates or polycarbonates has been considerable development in the past decades, however, the aerobic oxidative carboxylation of olefins to synthesis of cyclic carbonates from carbon dioxide and dioxygen with metalloporphyrin catalysts is difficult. But, carbon dioxide and water can be transformed to polysaccharides or cellulose in plants used catalyst-chlorophyll A that is exactly porphyrin structure.From the study of activation of carbon dioxide and the process and mechanism of the formation of cyclic carbonates via epoxides and carbon dioxide, further research of the synthesis of cyclic carbonate from dioxygen, carbon dioxide and olefins catalyzed by biomimetic porphyrin was detailed documented.(1) A magnetic nanoparticle (MNP)-supported biomimetic cobalt porphyrin (MNP-P) as cytochrome P-450 model was designed, prepared and evaluated as an efficient catalyst for coupling reaction of epoxides and carbon dioxide under 1.0 MPa carbon dioxide pressure at ambient temperature to generate relevant cyclic carbonates. The effects of different co-catalysts, the equivalent of co-catalyst and the recycling of catalyst were studied. The phentrimethyl ammonium tribromide (PTAT) combined with the supported porphyrin MNP-P was the best catalytic system to catalyze the cycloaddition of carbon dioxide to epoxides generating relevant cyclic carbonates at room temperature. The MNP-P catalyst could be simply recycled with the assistance of an external magnet and reused for 16 times without significant loss of activity and mass.(2) The cycloaddition of carbon dioxide to epoxides catalyzed by bifunctional metalloporphyrin (M(TTEMP)I4(X)) was studied. The reaction conditions of different metal center, counterion, reaction temperature and recycling times were optimized. 95.4% yield of propylene carbonate was formed at 85℃under 667 KPa within 5 hours. The moderate yield of submitted cyclic carbonate was obtained.(3) We synthesized a series of main group metalloporphyrins to catalyze the formation of cyclic carbonate from epoxides and carbon dioxide. The effects of different main group metal, co-catalyst, reaction temperature, and carbon dioxide pressure were investigated in detail. The cyclic carbonates was synthesized in high yields catalyzed by Al(TPP)Cl/2 PTAT at 25℃. The chiral cyclic carbonate was formation using chlorophyll A as catalyst. We found that the harder the acid, the stronger the Lewis acidity. The mechanism of this cycloaddition reaction catalyzed by main group metal porphyrin was discussed in detail.(4) We have been developed a new catalyst system of titanocene dichloride/Lewis base to catalyze the synthesis of cyclic carbonate from epoxides and carbon dioxide. The reaction conditions affecting the cycloaddition including reaction temperature, solvent and co-catalyst were optimized. The propylene carbonate was obtained with 98.1% yield and 392.1 h-1 TOF at 150℃under 1.2 MPa carbon dioxide pressure within 15 mins when using THF as solvent. To the best of our knowledge, this is the first report about metallocene catalyzed the coupling of epoxides and carbon dioxide to generate useful cyclic carbonates.(5) The synthesis of cyclic carbonate from carbon dioxide, dioxygen and olefins based on the previous studies on the cycloaddition of carbon dioxide to epoxides were reported. The styrene carbonate with 76% yield were obtained at 30℃under 1.1 MPa carbon dioxide pressure and 0.5 MPa dioxygen pressure within 48 hours using Ru(TPP)O2/2 TBAB as catalytic system from styrene, carbon dioxide and dioxygen. The scope of olefins was investigated. The aerobic oxidative carboxylation of olefins reaction mechanism was researched in detail.