Novel amphiphilic poly(2-oxazoline)s bearing l-prolinamide moieties as the pendants: Synthesis, micellization and catalytic activity in aqueous aldol reaction

Abstract

Abstract Novel amphiphilic poly(2-oxazoline)s bearing l -prolinamide moieties at the alkyl side-chain termini were designed and synthesized by a bottom-up protocol. These polymers formed micelle-type assemblies with a size of 10–30 nm in water, in which the majority of prolinamide active groups was tucked into the hydrophobic inner core. As a nanoreactor, the micellar systems were successfully applied to the direct asymmetric aldol reaction in aqueous media. The results demonstrated that the polymer-bound prolinamide catalysts show a significant improvement in catalytic efficiency when compared with their monomeric counterpart and non-amphiphilic reference polymer, affording the anti-product with a moderate stereoselectivity in the representative aldol addition of cyclohexanone to p -nitrobenzaldehyde. Additionally, the poly(2-oxazoline) derivatives can also promote effectively the reactions of tetrahydro-4 H -pyran-4-one or cyclopentanone donors to give the corresponding aldol adducts in high yield and with good diastereo- and enantioselectivities.