Recyclable DMAP-Functionalized polymeric nanoreactors for highly efficient acylation of alcohols in aqueous systems

Abstract

Fabrication of highly efficient and recyclable nanoreactors via macromolecular self-assembly represents a promising strategy for green organic transformation. In this study, small-molecule catalysts 4-(N,N-dimethylamino)pyridine (DMAP) functionalized nanoreactors were constructed by self-assembly of amphiphilic block copolymers with DMAP moieties in the hydrophobic block, leading to heterogeneous catalysts with excellent dispersity in water. The key preparation route included reversible addition-fragmentation chain transfer (RAFT) polymerization of 2-(N-methyl-N-(4-pyridyl)amino)ethyl methacrylate (MAPMA) and methyl methacrylate (MMA) using poly (oligomeric (ethylene glycol) methyl ether methacrylate) (POEGMA) as a hydrophilic macromoleculer RAFT reagent. The characterization by dynamic light scattering (DLS) and transmission electron microscopy (TEM) shows that the nanoreactors possess a core-shell nanostructure with the diameter of around 110 nm. The resulting polymeric nanoreactors showed excellent catalytic activity for acylation of alcohols in water. High conversion of a variety of alcohol (>99%) and excellent product selectivity were achieved. The high catalytic efficiency of the nanoreactors may be attributed to the enhancement of the interaction between the reactant and the catalyst in the confined hydrophobic space, which simulates how enzymes usually work. Moreover, the catalyst could be easily recovered by thermos-responsive separation and reused with high activity for more than 5 cycles. This study presents an efficient approach to achieve green catalytic reactions which are normally incompatible to aqueous conditions, potentially applicable to other catalytic systems such as metal-mediated organic transformations.