An enzymatic biomimetic system: enhancement of catalytic efficiency with new polymeric chiral ionic liquids synthesised by controlled radical polymerisation

摘要

The controlled radical polymerization of monomeric units containing chiral ionic liquids (CILs) allows thesynthesis of intrinsically chiral polymers through a bottom-up design. These polymeric chiral ionic liquids(PCILs) show a well-defined three dimensional structure organized as the result of a complex noncovalentnetwork of hydrogen-bonding contacts driven by the C2 hydrogen atoms of the imidazoliumaromatic rings and the OH moieties present in the side functionalities of the main polymeric chain. Theexchange of the chloride counter ion by the L-prolinate anion leads to new types of polymeric catalysts,which behave as efficient artificial aldolase biomimetic systems, being highly active and selective forthe aldol reaction in water. These new polymeric catalysts are significantly more active than thecorresponding monomeric counterpart when the reaction is performed either in water or in thepresence of water. The increase in catalytic efficiency can be related to their 3D structure, displayinghelical chirality in the polymeric chain as a function of their preparation methodology. Under suitableexperimental conditions, these polymers are able to catalyse the consecutive aldol-dehydration process,behaving as synthetic mimics of the aldolase-dehydrogenase enzymatic system. Moderateenantioselectivities can be achieved under suitable conditions.