Zinc bioinspired catalytic system for the valorisation of CO2 into cyclic carbonates

Abstract Cyclic organic carbonates are defined as key compounds for a sustainable chemical economy. Their synthesis from CO 2 under mild conditions is a useful way to valorise this greenhouse gas as carbon source. Even if a wide range of catalysts were described to promote the carbon dioxide cycloaddition into epoxides, only few ones concern enzymatic systems. The zinc– l ‐histidine active site of carbonic anhydrase inspired the present work, pointing out that the imidazole moiety of the amino acid ligand has a crucial role. An extensive study was undertaken to establish the structure–activity relationship of imidazole derivatives, zinc salts, and their respective catalytic activity in the CO 2 cycloaddition reaction. The effect of aromatic, alkyl, or iodine substituents and their position in N‐heterocycles were highlighted. A synergic effect was noted when combining imidazole compounds with zinc salts. The optimization of reaction conditions emphasised the in situ ZnI 2 –1‐methylimidazole catalytic system, which is selective toward cyclic styrene carbonates and efficient under solvent‐free mild conditions (50 °C, atmospheric CO 2 pressure). Once reusing tests confirmed the catalytic system robustness, the reaction scope was enlarged to several epoxides resulting in 84%–99% yields of their corresponding cyclic carbonates.