Fabrication of Nanoreactors Based on End-Functionalized Polymethacrylate and Their Catalysis Application

Abstract

Polymer-based nanoreactor, which can be achieved by self-assembling of amphiphilic polymers in water, has attracted more and more attention in recent years. In this study, a kind of Pd-nanoreactor was fabricated by self-assembling of chiral palladium complex-containing amphiphilic polymers in water. Firstly, chain transfer reagent (CTA) CEPA-PyOx was obtained by condensation reaction of (S,S)-4-hydroxymethyl-5-phenyl-2-(2′-pyridinyl)-1,2-oxazoline (PyOx) and 4-cyano-4-[((ethylthio)carbonothioyl)thio] pentanoic acid (CEPA) in the presence of EDC·HCl. Next, polymethacrylate with a terminal chiral oxazoline ligand (CEPA-POEGMA36-PyOx) was synthesized through Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization. After removal of the thioester bond and coordination with palladium trifluoroacetate, the polymer self-assembled in water affording Pd-nanoreactor, which possess core-shell structure and with chiral palladium complex in the core. At last, the nanoreactor was successfully applied in the asymmetric catalytic synthesis of flavanone in aqueous phase, and the catalyst loading was greatly reduced compared to unsupported palladium complex. In the presence of low palladium loading (0.5 mol%), flavanone was successfully synthesized with excellent yield (98%) and high enantioselectivity (82%).