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 methyl amine, 33 wt. % solution 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 multi-task reagent 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, (b) dehydrating activity through trapping of the released water molecular as association phase. Inexperienced chemists can handle it easily because it is solid and less toxic than a conventional catalyst, i.e., piperidine, pyridine, or metal- or halogen-containing salts. In addition, ethanol and PVIm could be recycled and reused in the next runs without any further purification. The regenerated PVIm demonstrated stable activity after several recycle runs. No changes were detected in its chemical structure, approved by FTIR and NMR spectra analyses.