Ionic liquids-functionalized porphyrins as bifunctional catalysts for cycloaddition of carbon dioxide to epoxides

Six ionic liquids-functionalized metallophorphyrins have been designed, prepared and characterized by NMR, MS and elemental analysis. They were applied as efficient bifunctional catalysts to the cycloaddition of epoxides and carbon dioxide without additive and organic solvent yielding cyclic carbonates. 5,15-Di[4-(4-tributylammoniobutoxy)phenyl]porphyrin zinc(II) dibromide (JB(p)) and 5,15-di [3-(4-tributylammoniobutoxy)phenyl]porphyrin zinc(II) dibromide (JB(m)) have been demonstrated excellent activities under optimized conditions. It has been found that both the structure of porphyrin complex cations and the anion moieties would strongly affect their catalytic performance. The catalysts were versatile for the cycloaddition of CO2 to various terminal epoxides in satisfying yields with excellent selectivities. Moreover, phenoxypropylene carbonate was able to be obtained under atmosphere pressure of CO2 and in large-scale. Furthermore, a plausible mechanism involving Lewis acid-base synergistic catalysis has been proposed according to our experimental results. (C) 2016 Elsevier Ltd. All rights reserved.