Greener and scalable synthesis of N-methyl imines using a sustainable functional polymer

Abstract

N-Methyl imines, as simple Schiff bases, could be prepared using a more sustainable and greener system, including a 33 wt.% solution of methylamine in absolute ethanol, and poly(N-vinylimidazole) (PVIm) at room temperature within 45–60 min. PVIm is a biocompatible, biodegradable and water-soluble synthetic solid functional polymer. It was indicated that PVIm can act as a reagent with multiple tasks in this reaction, including (a) reducing activation energy and stabilizing the transition states through hydrogen bond acceptor sites and low acidity of C(2)–H and (b) dehydrating activity through trapping of the released water molecules as the association phase. Inexperienced chemists can handle it easily because it is solid and less toxic than conventional catalysts – that is, piperidine, pyridine or metal- or halogen-containing salts. Additionally, ethanol and PVIm could be recycled and reused in subsequent runs without any further purification. The regenerated PVIm demonstrated stable activity after several recycle runs. No changes were detected in its chemical structure, as confirmed by Fourier transform infrared and nuclear magnetic resonance spectrum analyses.