Microwave-enhanced reductive amination via Schiffʹs base formation for block copolymer synthesis

Reductive amination via Schiffʹs base formation is a widely used reaction for laboratory and industrial applications ranging from protein immobilization to nanoparticle synthesis. One major limitation of this reaction is the slow kinetics and hence, it can take several days for the reaction to reach completion. Here we demonstrate that electromagnetic microwave can be used to accelerate the rate of reduction amination. To demonstrate proof of concept, we utilized the reductive amination between reducing end of dextran and primary amine from N-Boc-ethylenediamine as a model reaction. The reaction was conducted at room temperature to demonstrate that the enhancement was mainly due to electromagnetic effects of the microwave rather than thermal effects. We show that reductive amination reaction time was reduced from 72 h to 4 h using microwave irradiation. These results indicate non-thermal microwave effects to expedite reductive amination for synthesizing copolymers. The efficient conjugation of dextran using reductive amination provides an important tool for developing biocompatible copolymers using carbohydrates.