A bioinspired approach toward efficient supramolecular catalysts for CO2 conversion

Nature uses enzymes for affording astonishingly efficient chemical transformations with high chemo-, regio-, and stereoselectivity (e.g., carbonic anhydrase for CO2 conversion). Such sophisticated biomolecules lead to excellent catalytic activities as a result of harmonized supramolecular interactions with the substrates/intermediates of the reactions. Based on this approach, different Zn2+ complexes of pseudopeptidic macrocycles with a high level of preorganization were synthesized and tested as catalysts for cycloaddition of CO2 to epoxides. These bioinspired systems promoted remarkable activities even under mild conditions without the need for any auxiliary co-catalysts. The whole catalytic cycle was dominated by cooperative non-covalent forces involving multiple functional sites, displaying enzyme-like catalytic behavior. The chiral environment associated with the amino acid side chains in the preorganized catalytic system provided recognition sites for efficient kinetic resolution of epoxides. In the case of the sluggish styrene oxide substrate, the highest selectivity factor reported to date was attained.