Amino acids/superbases as eco-friendly catalyst system for the synthesis of cyclic carbonates under metal-free and halide-free conditions

Laminaria digitata and Palmaria palmata Seaweeds as Natural Source of Catalysts for the Cycloaddition of CO2 to Epoxides

“…A small quantity of 1-phenyl-1,2-ethanediol by-product was observed, which was found to increase when incorporating polar amino acids histidine and lysine as co-catalysts, most likely due to residual water contamination, (SI, Table S1a–e). However, the addition of amino acid co-catalysts containing a basic group (histidine and lysine) significantly increased conversions to styrene carbonate for all metal halide catalysts containing a bromide and chloride counter ion; histidine was found to give the greatest synergistic effect of all, in accordance with the literature [37]. CaCl 2 achieved 80.0% conversion to 2a when used with histidine as opposed to being inactive when used alone.…”

Rational Study of DBU Salts for the CO2 Insertion into Epoxides for the Synthesis of Cyclic Carbonates

“…Some of the most efficient organocatalysts reported in the literature for the synthesis of cyclic carbonates are based on DBU, − since it is able to activate CO 2 to afford a catalytically active zwitterionic carbamate species and favors the ring expansion of epoxides . There are two different approaches to developing catalytic DBU derivatives.…”

Cycloaddition of CO2 to epoxides by highly nucleophilic 4-aminopyridines: establishing a relationship between carbon basicity and catalytic performance by experimental and DFT investigations

“…Seminal work on binary catalytic systems employing HBDs in the presence of halogen-free nucleophiles were reported such as DMAP/p-methoxyphenol 53 (DMAP: 4-dimethylaminopyridine), DBU/cellulose 54 (DBU: 1,8-diazabicyclo [5.4.0]undec-7-ene) and DBU-histidine. 55 However, the use of these catalytic systems required relatively harsh reaction conditions (120 °C, 20-36 bar CO2 pressure) and, often, high loadings (up to 10 mol%) of bases. Moreover, in the prospect of heterogeneous catalysts design, it should be considered that the different components of binary catalytic systems are generally difficult to coimmobilize, making the use of single catalytic moieties more desirable.…”