Formation of Cyclic Carbonates from Carbon Dioxide and Epoxides Coupling Reactions Efficiently Catalyzed by Robust, Recyclable One-Component Aluminum-Salen Complexes

Abstract

Aluminum salen complexes bearing appended quaternary ammonium salt substituents have been synthesized and shown to be effective catalysts for the coupling of epoxides and carbon dioxide to generate cyclic carbonates. 27 Al NMR spectra have demonstrated that these exist as both five-and six-coordinate Al(III) species in dimethylsulfoxide (DMSO) solution, whereas only a five-coordinate Al(III) species was detected in the (salen)AlCl analogue in the presence of an external onium salt. The onium salt group tethered on the salen ligand was found to play an important role in enhancing the catalytic activity. The effects of reaction variables such as temperature, time, pressure, molar ratio of epoxide to catalyst on the catalytic performance were systematically investigated. These bifunctional catalysts were found to be highly stable to moisture and oxygen, resistant to impurities, and recyclable with only minor losses in catalytic activity.

Highly efficient conversion of CO2 at atmospheric pressure to cyclic carbonates with in situ-generated homogeneous catalysts from a copper-containing coordination polymer

“…11) have been characterized. According to the above kinetic experiments and previous experiments [38,39], a bromide anion (Br À ) may be involved in the catalysis and most likely serves as a key nucleophile. The role of the halide anion on the epoxide activation prior to carbon dioxide fixation has been also reported in the previous computational studies [9,40].…”

Enantiomeric impurities in chiral catalysts, auxiliaries, and synthons used in enantioselective syntheses. Part 4

“…41 (1) Used in the carbon dioxide and epoxides coupling reactions to form cyclic carbonates. 42 (2) Used in the a-addition of isocyanides to aldehydes. 43 (3) Used in the enantioselective addition of indoles to arylnitroalkenes to enantiomerically enriched tryptamine precursors.…”

Metal Complexes Catalyzed Cyclization with CO2

“…Whereas the first catalytic systems showed a considerable decrease in catalytic activity in subsequent cycles, the Al(salen) catalyst reported by Darensbourg in 2012 showed higher stability towards moisture and heat; it tolerates process impurities and shows only a minor loss in activity over five catalytic cycles [74].…”