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Hydroiodides of secondary and primary amines effectively catalyzed the reaction of carbon dioxide and epoxides under mild conditions such as ordinary pressure and ambient temperature, to obtain the corresponding five-membered cyclic carbonates in moderate to high yields. Detailed investigation showed that the catalytic activity was highly affected by the counter anions of the ammonium salts; the iodides catalyzed efficiently the carbonate-forming reactions, whereas the bromide and chloride counterparts exhibited almost no catalysis. We also revealed that two important factors on the amine moieties that affected the catalytic reactions. First, the catalytic activity increased with increasing bulkiness of the substituents on the ammonium nitrogen atoms. Second, the catalysis became more efficient as the parent amines become more basic. Dicyclohexylammonium iodide was the best catalyst among the ammonium salts investigated in this study. As an application of this reaction system, we synthesized homo-and copolymers bearing epoxide pendant groups as substrates, which were converted with high efficiency into the corresponding homo-and copolymers bearing cyclic carbonate pendant groups under 1 atm at 45 C. All polymers were easily purified simply by precipitation in water, and were isolated in high yields (>95%).

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Hydroiodides of amidines effectively catalyzed the reaction of CO2 and epoxides under mild conditions such as ordinary pressure and ambient temperature, and the corresponding 5-membered cyclic carbonates were obtained in moderate to high yields.

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In this study, we investigated the CO 2 -capture/ release behavior of the polystyrene-bearing cyclic amidine pendant groups, which was synthesized via free radical polymerization of HCl salt of the corresponding styrene monomer followed by neutralization. For comparison, we also prepared the polystyrene bearing N-formyl-1,3-propanediamine pendant groups through the hydrolysis of the cyclic amidine group by treatment with an alkaline solution. First, we examined the CO 2 -capture/release behaviors of the amidine and amine monomers in aqueous solution in terms of conductivity. The conductivity of a wet DMSO solution of the amidine monomer increased upon CO 2 bubbling at 25 C and reached a stationary value of about 11 mS/m, which indicated the formation of the bicarbonate salt. Conversely, the conductivity decreased to its original value upon N 2 bubbling at 50 C, reflecting the complete release of the trapped CO 2 molecules. Both solutions showed the changes in the conductivity with quick responses, and no appreciable difference was observed between them. We then investigated the CO 2 -capture/release behaviors of the amidine and amine polymers, by taking advantage of the binary system with polyethylene glycol, and found that the binary system with the amidine polymer captured and released CO 2 more efficiently than that with the amine polymer.Polyethylene glycols (PEGs) are known to have interesting properties, such as good miscibility for common solids, thermal stability, nonvolatility, innocuousness, and environmentally benign characterization. In particular, PEGs have high affinity toward CO 2 and show some CO 2 -expansion effect that increases gas/liquid diffusion rates. 30 By taking Additional Supporting Information may be found in the online version of this article.